Browse Topic: PCCI engines

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7.0.101 - A New Image De-hazing Method for Safety Critical ADAS ApplicationsSAE-PP-002772/4/2021
Driver safety and Advanced Driver Assistance Systems (ADAS) is gaining lot of importance these days. In some countries, there are strict regulations in place which mandate the use of certain ADAS features in automobiles. However, as the need for these safety critical systems increases, the challenges associated also increase. These challenges can arise due to technology, human factors or due to nature. In countries like India, where one can expect different weather conditions with changing geography, the associated challenges are mainly due to the natural factors like haze, fog, rain and smoke. This poses a challenging problem in terms of visibility for the drivers as well as in vision based ADAS; thereby, leading to many fatal road accidents. In this paper, a novel pre-processing technique, which addresses the interesting problem of enhancing the perceptual visibility of an image that is degraded by atmospheric haze, is proposed. The solution to this problem is presented by combining model (Beer Lambert model) based and non-model based technique of haze removal. The combined hybrid model picks the best haze free image from the series of non-hazy outputs, that are derived based on multiple scattering coefficients of the input hazy image. The idea here is to restore the true color of an image that is affected by the atmospheric haze. In comparison with the state of the art methods that are available in literature, the proposed method is shown to be capable of recovering better haze-free images both in terms of visual perception and quantitative evaluation. The proposed method promises better perceptual understandings and visibility restoration for vision based ADAS under hazy driving conditions.
Lname, Fname
6.0.116 - Development of 6 Years Old Child Virtual Model by Automatic ScalingSAE-PP-002712/4/2021
Traffic accidents cause one of the highest numbers of severe injuries in the whole population. The numbers of deaths or seriously injured citizens prove that traffic accidents and their consequences are still a serious problem to be solved. A lot of effort is devoted to both passive and active safety systems development. The transportation standards usually define safety requirements by regulations (e.g. ECE-R94, 96/79/EC and ECE-R95, 96/27/EC in Europe) with specific dummies for children to be used. The dummies include hardware sensors for monitoring accelerations, loads and other signals and each dummy is developed for a specific scenario, but there are limitations of these dummies, such as only a specific age or calibration just for a specific test. Taking into account that the consequence of a traffic accident is highly influenced by the stature of the body, virtual human body models, including those for children, start to play a significant role because they can be scaled or even personalized towards a particular population or even a particular person. The paper contributes to the field of vehicle safety technology concerning child restraint systems development, assessment and optimization with a virtual numerical approach. The goal of the paper is to exploit the previously developed scaling algorithm to create a virtual model of a six-year-old (6YO) child and to compare its response to the virtual dummy used for child safety in order to propose an automatic scaling process for a population-based vehicle safety assessment. The automatic scaling algorithm developing virtual human body models for a given age and gender is used to create the virtual 6YO child model. The algorithm scales body dimensions and particular segments' mass and the flexibility of the body is driven by flexindex and stiffness scaling. The performance of the automatically developed virtual 6YO child model was tested in frontal and lateral directions. The frontal response was tested with a standard sled test simulation using the standardized AAMA pulse in the frontal direction. The lateral response was tested with a side barrier impact test. The results of both tests were compared to the validated virtual Q6 Child Dummy FE model. The paper shows good performance of the automatic scaling process for developing 6YO virtual model for safety assessment. The automatically developed 6YO child model corresponds well from both the anthropological point of view and performance point of view to the existing validated dummy model.
Mutagaana, Festo
6.0.101 - Piston Sealing System Structure Design for Automobile's Lightweight Auto-TransmissionSAE-PP-002572/4/2021
Current automobile's auto-transmission has problems of defects and cost reduction because of welding process and very complicated assembly process due to individualized transmission piston and sealing components. Also, size and heavy weight of transmission piston components are the source of low mileage because they are made of aluminum, steel material. In this study, therefore, we perform structure design for piston sealing system which integrates piston and sealing material for automobile's lightweight auto-transmission. Also performed stress analysis through finite element analysis to secure required suitable strength when internal pressure is applied after assemble.
Mutagaana, Festo
2.0.101 - Experimental Study of cooling of Continuously Variable Transmission (CVT) in ScooterSAE-PP-002102/1/2021
The continuously variable transmission (CVT), which was conceptualized more than 500 years ago, is just now beginning to replace traditional transmissions in some automobiles. It is mostly used in scooter transmission. Engine power is transmitted to wheel through belt drive between two pulleys. The diameter of belt contact with pulley can change continuously and hence provide infinite gear ratios between driver and driven shafts. This technology leads to a smoother ride of vehicle. Heat is generated inside CVT due to friction between drive belt and clutch pulley. Amount of heat generated is even more due to clutch slippage during acceleration and deceleration. This will affect the service life of CVT components such as front movable drive (FMD), clutch pulley, clutch outer, and belt. In scooters generally, air cooling is preferred over liquid cooling. Cooling is achieved by incorporating centrifugal fan inside CVT housing. For better durability/service life, the degree of heat generated at CVT components should be minimal. The objective of this work is to identify the parameters causing change in temperature of CVT components and to evaluate its surface temperature in accordance with changed parameters. With reference to this, experiments were conducted with requisite design modification inside CVT housing, which enhances cooling effect. Amongst, variables determining air flow rate, are studied and their effect on temperature inside CVT housing is observed experimentally. Keeping the previous variables unaltered, further design modifications related to air flow pattern are done and cumulative effect of all variables is observed. Experiments were performed on an 110cc scooter engine by following customer driving pattern on chassis dynamometer. Results showed that design modifications intended for better cooling effect, has brought down temperature at CVT components. So, desired cooling effect is observed inside CVT housing imparting better service life of CVT components.
Mutagaana, Festo
Infrared/Visible Optical Diagnostics of RCCI Combustion with Dieseline in a Compression Ignition Engine2020-01-05574/14/2020
Compression ignition engines are widely used for transport and energy generation due to their high efficiency and low fuel consumption. To minimize the environmental impact of this technology, the pollutant emissions levels at the exhaust are strictly regulated. To reduce the after-treatment needs, alternative strategies as the low temperature combustion (LTC) concepts are being investigated recently. The reactivity controlled compression ignition (RCCI) uses two fuels (direct- and port- injected) with different reactivity to control the in-cylinder mixture reactivity by adjusting the proportion of both fuels. In spite of the proportion of the port-injected fuel is typically higher than the direct-injected one, the characteristics of the latter play a main role on the combustion process. Use of gasoline for direct injection is attractive to retard the start of combustion and to improve the air-fuel mixing process. In this work, the influence of the direct-injected fuel properties on RCCI combustion mode is studied in an optical compression ignition engine. Gasoline fuel is injected in the intake manifold while a blend of gasoline and diesel (a.k.a. dieseline) is directly injected into the cylinder. Non-conventional optical diagnostics in the visible and infrared spectra are applied for the direct investigation of the in-cylinder phenomena during the injection and the combustion processes. A low-luminosity, mainly kinetically controlled combustion mode has been observed.
Sequino, Luigi, Mancaruso, Ezio, Monsalve-Serrano, Javier, Garcia, Antonio
Use of Butanol Blend Fuels on Diesel Engines - Effects on Combustion and Emissions2020-01-03334/14/2020
Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Like ethanol, butanol can be produced as a biomass-based renewable fuel or from fossil sources. In the research project, DiBut (Diesel and butanol) addition of butanol to Diesel fuel was investigated from the points of view of engine combustion and of influences on exhaust aftertreatment systems and emissions. One investigated engine (E1) was with emission class “EU Stage 3A” for construction machines, another one, engine (E2) was HD Euro VI. The most important findings are: with higher butanol content, there is a lower heat value of the fuel and there is lower torque at full load. With Bu30 the conversion rates of CO and HC in the oxidation catalyst (DOC) are slightly lower, light-off temperatures are a little higher and NO2 production is lower. The PM-emissions with Bu30 are lower, so the soot loading of DPF takes a longer time. No impacts of Bu30 on NOx reduction rates of the SCR-system and on the non-legislated gaseous emission components were found. The operation of engine (E1) with Bu30 (30% vol butanol in fuel) was instable at lower part load due to the lower Cetane Number of the blend fuel. The electronic control system of the engine (E2) compensated very well the varying properties of fuels up to Bu30. For both investigated engines, the butanol rate (Bu30) can be considered as a limit for a problem-free engine starting and operation.
Engelmann, Danilo, Czerwinski, Jan, Nauroy lng, Hervé, Comte, Pierre, Hüssy lng, Andreas
Numerical Investigation of the Combustion Kinetics of Partially Premixed Combustion (PPC) Fueled with Primary Reference Fuel2020-01-05544/14/2020
This work numerically investigates the detailed combustion kinetics of partially premixed combustion (PPC) in a diesel engine under three different premixed ratio fuel conditions. A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict PPC combustion under various operating conditions. The experimental results showed that the increase of premixed ratio (PR) fuel resulted in advanced combustion phasing. To provide insight into the effects of PR on ignition delay time and key reaction pathways, a post-process tool was used. The ignition delay time is related to the formation of hydroxyl (OH). Thus, the validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how PR change the formation of OH during the low-to high-temperature reaction transition. The reaction pathway analyses of the formations of OH before ignition time were investigated. It was found that in the case of PR0%, the second isomerization from C7H14OOH2-4O2 to NC7KET24 and the decomposition of NC7KET24 contributed 27.6% and 46.46% of OH formation respectively. The contribution of AC8H16OOH-B to the formation of OH was just 12.13%. It can be concluded that the low temperature oxidation reactions of n-heptane were key steps in producing OH. While in the cases of PR30% and PR50%, because of the higher in-cylinder temperature, most of OH derived from the decomposition reaction of H2O2 that contributed 54.47% and 54.63% of OH formation respectively. Besides, in the PR30% and PR50%, the oxidation reactions of IC4H7 contributed 31.95% and 33.84% of OH formation respectively, and the oxidation reaction of IC4H6OH contributed 19.08% and 22.22% of OH formation respectively, which indicated that the oxidation of iso-octane also contributed to the production of OH. In addition, the distributions of mass fraction, production rate and representative creation reaction (RCR) of OH showed that in the case of PR30% and PR50%, the formation of OH outside the spray periphery were dominated by the reactions R394 (H2O2 (+ M) <=> 2 OH (+ M)), while that in the spray periphery were predominantly controlled by the reaction R21 (NC7KET24 => NC3H7CHO + CH3COCH2 + OH) and R125 (IC4H6OH + HO2 <=> CH2CCH2OH + CH2O + OH). Premixed fuel from port injection changed the formation pathway of OH during the oxidation of direct injection fuel through the reaction R125.
Zhao, Yuanyuan, Wang, Hu, Liu, Xinlei, Liu, Daojian, Chenchen, Wang, Zhu, Hongyan, Zheng, Zunqing, Yao, Mingfa
Transition from HCCI to PPC: Investigation of the Effect of Different Injection Timing on Ignition and Combustion Characteristics in an Optical PPC Engine2020-01-05594/14/2020
The partially premixed combustion (PPC) concept is regarded as an intermediate process between the thoroughly mixed Homogeneous charge compression ignition (HCCI) combustion and compression ignition (CI) combustion. It’s a combination of auto-ignition mode, a fuel-rich premixed combustion mode, and a diffusion combustion mode. The concept has both high efficiency and low soot emission due to low heat losses and less stratified fuel and air mixtures compared to conventional diesel CI. The mechanisms behind the combustion process are not yet very well known. This work focuses on the efficiency and the in-cylinder process in terms of fuel distribution and the initial phase of the combustion. More specifically, double injection strategies are compared with single injection strategies to achieve different levels of stratification, ranging from HCCI to PPC like combustion as well as poor (43%) to good (49%) of gross indicated efficiency. The experiments were performed in an optical heavy-duty CI engine. To analyze how the efficiency was affected in a transition from HCCI to PPC, the natural luminosity (N.L.) was captured with high-speed video (HSV). To complement the HSV data, fuel, temperature, and oxygen distribution were explored by Computational fluid dynamics (CFD) simulation. The results show that the jet-jet and jet-piston interactions can be modified and can reshape the transition trends of gross indicated efficiency and ignition location compared to a single injection. In the transition region, these interactions can improve the efficiency by shaping the fuel-rich region away from cold areas, like the vertical wall of the piston and the squish region, to avoid fuel wetting and incomplete combustion. However, with double injections in the piston bowl (PPC region), jet-jet interaction can unfortunately inhibit the mixing process of the second fuel jet and oxygen due to interaction with the fuel rich region from the first injection, ending up with a lower combustion efficiency.
Zhang, Miao, Derafshzan, Saeed, Xu, Leilei, Bai, Xue-Song, Richter, Mattias, Lundgren, Marcus
Nonlinear Identification Modeling for PCCI Engine Emissions Prediction Using Unsupervised Learning and Neural Networks2020-01-05584/14/2020
Premixed charged compression ignition (PCCI) is an advanced combustion strategy, which has the potential to achieve ultra-low nitrogen oxide and soot emissions at high thermal efficiencies. PCCI combustion is characterized by a complex nonlinear chemical-physical process, which indicates that a physical description involves significant development times and also high computation cost. This paper presents a method to use cylinder pressure data and engine operations parameters for prediction of PCCI engine emissions by unsupervised learning and nonlinear identification techniques. The proposed method first uses principal component analysis (PCA) to reduce the dimension of the cylinder-pressure data. Based on the PCA analysis, a multi-input multi-out model was developed for nitrogen oxide and soot emission prediction by multi-layer perceptron (MLP) neural network. Before the training process, a second principal component analysis was done to reduce the input dimension with hyper-parameters thereby reducing memory requirements of the models. The algorithm is applied to an experimental data set from a single-cylinder light-duty engine with piezo injection system. By comparing the model predictions with experimental results, it is shown that the neural network coupling with the unsupervised learning method can successfully capture the nonlinear relationship between the state parameters and the emissions of PCCI combustion system.
Pan, Wang, Korkmaz, Metin, Beeckmann, Joachim, Pitsch, Heinz
Control of Ignition Timing and Combustion Phase by Means of Injection Strategy for Jet-Controlled Compression Ignition Mode in a Light Duty Diesel Engine2020-01-05554/14/2020
Controllability of ignition timing and combustion phase by means of dual-fuel direct injection strategy in jet-controlled compression ignition mode were investigated in a light-duty prototype diesel engine. Blended fuel with lower reactivity was delivered in the early period of compression stroke to form the premixed charge, while diesel fuel which has higher reactivity was injected near TDC to trigger the ignition. The effects of several important injection parameters including pre-injection timing, jet-injection timing, pre- injection pressure and ratio of pre-injection in the total heat value of injected fuel were discussed. Numerical Simulation by using CFD software was also conducted under similar operating conditions. The experimental results indicate that the jet-injection timing shows robust controllability on the start of combustion under all the engine load conditions. Pre-injection timing/pressure/ratio show little impact on the start of combustion due to low reaction activity of premixed charge. Early pre-injection timing and larger pre-injection pressure lead to wall-wetting and poor vaporization of pre-injected fuel especially at light duty conditions, as a result, combustion duration increases, and CO/THC emissions enhance. Larger pre-injection ratio in the total heat value of injected fuel prolongs combustion duration and enhances CO/THC emissions at lower engine load, reduces combustion duration and CO/THC emissions at higher engine load. The numerical simulation results demonstrate the two-stage combustion process described according to the experimental results. The two-stage combustion process of diesel jet JCCI mode is featured by the evolution of intermediate species such as H2O2 and OH, and the main emission products such as CO and NOx. At last, the effects of injection parameters on JCCI combustion characteristics are summarized.
Zhu, Jingyu, Bo, Li, Long, Wuqiang
Impact of Multiple Injection Strategies on Efficiency and Combustion Characteristics in an Optical PPC Engine2020-01-11314/14/2020
Partially premixed combustion (PPC) is a promising way to achieve high thermal efficiency and low emissions, especially by using multiple injection strategies. The mechanisms behind PPC efficiency are still to be explained and explored. In this paper, multiple injections have been used to affect the gross indicated efficiency in an optical PPC engine modified from a Volvo MD13 heavy-duty diesel engine. The aim is both to improve and impair the gross indicated efficiency to understand the differences. The combustion natural luminosity is captured by a high-speed camera, and the distribution of fuel, oxygen, and temperature during the combustion process has been further explored by CFD simulation. The results show that with the right combination of the pilot, main, and post injection the gross indicated efficiency can be improved. Using a post injection in a triple-injection case show to have less effect on the combustion phasing than pilot injection in a double-injection case, while it can significantly affect combustion efficiency. The later of the double-injection cases tested (c30/16), has less heat transfer losses since the high-temperature region transported away from the cylinder head and piston bowl wall, which can be seen in the CFD-simulations. The highest gross indicated efficiency among the tested cases is given by the triple-injection case d38/24/6 as it reaches the best balance between the mixing and the local temperature through the jet-jet interactions and combustion-jet interactions.
Zhang, Miao, Xu, Leilei, Derafshzan, Saeed, Bai, Xue-Song, Richter, Mattias, Lundgren, Marcus
Varying Intake Stroke Injection Timing of Wet Ethanol in LTC2020-01-02374/14/2020
Computational Fluid Dynamics (CFD) modeling was used to investigate the effects of the direct injection of wet ethanol at various injection timings during the intake stroke in a diesel engine with a shallow bowl piston. Thermally Stratified Compression Ignition (TSCI) has been proposed to expand the operating range of Low Temperature Combustion (LTC) by broadening the temperature distribution in the cylinder prior to ignition. TSCI is accomplished by injecting either water or a water-fuel mixture with a high latent heat of vaporization like wet ethanol. This current study focuses on isolating the effects that injecting such a high heat of vaporization mixture during the intake stroke has on the distribution of temperature and equivalence ratio in the cylinder before the onset of combustion. A CONVERGE 3-D CFD model of a single cylinder diesel research engine using Reynolds Averaged Naiver Stokes (RANS) turbulence modeling was developed and validated against experimental data. Then, five cases of injection timing with an injector included angle of 60° were simulated from -330 CAD to -210 CAD BTDC in increments of 30 CAD and five cases with an injector included angle of 150° were simulated from -330 CAD to -240 CAD BTDC also in increments of 30 CAD with an additional case at -340 CAD BTDC. For each spray case, the temperature and equivalence ratio stratification in the cylinder 10 CAD before TDC were analyzed using joint probability density functions (jPDFs). Results show that a later injection timing yields a more stratified mixture as well as a stronger inverse relationship between local temperature and equivalence ratio. An injection of wet ethanol at specific timings also causes the fuel to experience different mixing profiles due to the injector included angle and the piston position at each injection timing. Wall wetting on the piston was another area explored under varying spray conditions due to the high heat of vaporization of the fuel mixture.
O'Donnell, Patrick C., Rahimi Boldaji, Mozhgan, Gainey, Brian, Lawler, Benjamin
Combustion System Optimization of a Light-Duty GCI Engine Using CFD and Machine Learning2020-01-13134/14/2020
In this study, the combustion system of a light-duty compression ignition engine running on a market gasoline fuel with Research Octane Number (RON) of 91 was optimized using computational fluid dynamics (CFD) and Machine Learning (ML). This work was focused on optimizing the piston bowl geometry at two compression ratios (CR) (17 and 18:1) and this exercise was carried out at full-load conditions (20 bar indicated mean effective pressure, IMEP). First, a limited manual piston design optimization was performed for CR 17:1, where a couple of pistons were designed and tested. Thereafter, a CFD design of experiments (DoE) optimization was performed where CAESES, a commercial software tool, was used to automatically perturb key bowl design parameters and CONVERGE software was utilized to perform the CFD simulations. At each compression ratio, 128 piston bowl designs were evaluated. Subsequently, a Machine Learning-Grid Gradient Algorithm (ML-GGA) approach was developed to further optimize the piston bowl design. This extensive optimization exercise yielded significant improvements in the engine performance and emissions compared to the baseline piston bowl designs. Up to 15% savings in indicated specific fuel consumption (ISFC) were obtained. Similarly, the optimized piston bowl geometries produced significantly lower emissions compared to the baseline. Emissions reductions up to 90% were obtained from this optimization exercise. The performances of the optimized piston bowl geometries were further validated at different operating conditions at the high-load point and at part-load conditions (6 bar IMEP) and compared with those of the baseline designs. The dependence of the engine performance on the piston bowl geometry at part-loads was lower than that at high-loads because injections normally occurred earlier (-60 to -20 CAD after top dead center (aTDC)) where minimal interactions between the spray and piston were anticipated. The interactions between late injections (-3 to 3 CAD aTDC) and piston geometry at high-loads significantly affected, fuel-air mixing, droplet breakup, combustion and emissions. It was also observed that heat losses, dictated by the interactions between the flame and piston surface, significantly affected the performance of the engine.
Badra, Jihad, khaled, Fethi, Sim, Jaeheon, Pei, Yuanjiang, Viollet, Yoann, Pal, Pinaki, Futterer, Carsten, Brenner, Mattia, Som, Sibendu, Farooq, Aamir, Chang, Junseok
Thermal Efficiency Improvements with Split Primary Fuel Injections in Semi-Premixed Diesel Combustion with Multi-Peak Shaped Heat Release2019-01-217012/19/2019
To improve the combustion characteristics in semi-premixed diesel combustion, consisting in the first-stage premixed combustion of the primary fuel injection and the second-stage spray combustion of the secondary injection, the effect of splitting the primary injection was investigated in a diesel engine and analyzed with a CFD. The indicated thermal efficiency improves due to reductions in heat transfer losses to the in-cylinder wall and the combustion noise is suppressed with the split primary injections. The CFD analysis showed that the reduction in heat transfer loss with the split primary injections is due to a decrease in the combustion quantity near the combustion chamber wall.
Inaba, Kazuki, Masuko, Yosuke, Zhang, Yanhe, Kobashi, Yoshimitsu, shibata, Gen, Ogawa, Hideyuki
A Study of a Lean Homogeneous Combustion Engine System with a Fuel Reformer Cylinder2019-01-217712/19/2019
The Dual-Fuel (DF) combustion is a promising technology for efficient, low NOx and low exhaust particulate matter (PM) engine operation. To achieve equivalent performance to a DF engine with only the use of conventional liquid fuel, this study proposes the implementation of an on-board fuel reformation process by piston compression. For concept verification, DF combustion tests with representative reformed gas components were conducted. Based on the results, the controllability of the reformed gas composition by variations in the operating conditions of the reformer cylinder were discussed.
Asai, Go, Tokuoka, Yuki, Bayer, Thomas, Ishiguro, Shuntaro, Shibata, Gen, Ogawa, Hideyuki, Kobashi, Yoshimitsu, Watanabe, Yusuke
Numerical Optimization of Compression Ratio for a PPC Engine running on Methanol2019-01-216812/19/2019
Partially premixed combustion (PPC) has shown to produce high gross indicated efficiencies while yielding lower pollutant emissions, such as oxides of nitrogen and soot, than conventional diesel combustion. Gasoline fuels with a research octane number (RON) of 60-70 have been proposed as optimal for PPC as they balance the trade-off between ensuring good combustion stability at low engine loads and avoiding excessive peak pressure rise rates at high loads. However, measures have to be taken when optimizing the engine operating parameters to avoid soot emissions. In contrast, methanol has a much lower propensity for soot formation. However, due to a higher RON of methanol the required intake temperature is higher for the same engine compression ratio to ensure auto-ignition at an appropriate timing. Increasing the compression ratio allows a lower intake temperature and improves combustion stability as well as engine brake efficiency. Nevertheless, a higher compression ratio generally increases in-cylinder heat losses and peak pressure. These effects were investigated in a simulation study, which combined 0-D and 1-D models, of a multi-cylinder heavy-duty Scania D13 engine operated in PPC mode and running on methanol. Engine experiments from a single-cylinder engine at different compression ratios were used to validate the simulation models. The optimal compression ratio from a brake efficiency perspective was found for four operating conditions from the 12 mode non-idle European stationary cycle supplemental emissions test points. This compression ratio was then used for optimizing key engine parameters. The results showed that a 21.6:1 compression ratio was optimal instead of the original 17.3:1 compression ratio. Especially at lower engine loads, a significant increase in brake efficiency was found. The main reason was a lower intake temperature which increased the average ratio of specific heats and allowed for a lower boost pressure.
Svensson, Erik, Verhelst, Sebastian
Characteristics Investigation on Di Diesel Engine with Nano-Particles as an Additive in Lemon Grass Oil2019-28-008110/11/2019
In this experimental study, combustion, performance & emission characteristics of a single cylinder D.I. diesel engine is analyzed using lemon grass oil and diesel blend B20. The alumina (Al2O3) nano-particles of 10, 20 and 30 parts per million (B20A10, B20A20, B20A30) are assorted with prepared fuel blend through an ultrasonicator which would help to fetch an unvarying suspension of nano-particles over the blend fuel. SEM analysis and X-ray diffraction have been done for the alumina nano-particles to test the size of the particles that are blended to the bio-fuel blends. The chemical reactivity and rate of mixing are better though the characteristics of nano-particles exhibit high exterior area/capacity ratio during combustion that ultimately results in good characteristics of a diesel engine. Among test fuels, B20A20 shows healthier performance both in relationships of efficiency & emissions such as Nitrous oxide (NOx), hydrocarbon (HC), Carbon monoxide (CO), and Smoke. The ŋBTE for fuel B20A20 is significantly improved by 11.5% when it is compared to the fuel B100. The HC emission is decreased by 40%, CO emission reduced by 6%, NOx emission decreased by 31% and smoke emission reduced by 39% when it is compared to the pure bio-fuel (B100). It is seen clearly that the blending of bio-fuel at the proportion of B20 in the diesel fuel has increased the performance and reduced HC, CO and smoke emission owing to the increase in NOx emission due to better combustion characteristics. From this investigation, adding alumina nano-particles has improved combustion quality showing better performance and shown reduced NOx, CO, HC & smoke in comparison to neat diesel and bio-fuels.
Balasubramanian, Dhinesh, Papla Venugopal, Inbanaathan, Viswanathan, Karthickeyan
Zero-Dimensional Heat Release Modeling Framework for Gasoline Compression-Ignition Engines with Multiple Injection Events2019-24-00839/9/2019
A zero-dimensional heat release model was developed for compression ignition engines. This type of model can be utilized for parametric studies, off-line optimization to reduce experimental efforts as well as model-based control strategies. In this particular case, the combustion model, in a simpler form, will be used in future efforts to control the combustion in compression ignition engines operating on gasoline-like fuels. To allow for a realistic representation of the in-cylinder combustion process, a spray model has been employed to allow for the quantification of fuel distribution as well as turbulent kinetic energy within the injection spray. The combustion model framework is capable of reflecting premixed as well as mixing controlled combustion. Fuel is assigned to various combustion events based on the air-fuel mixture within the spray. The mixing controlled combustion consists of two separate combustion events; one occurring within the fuel spray, which is characterized by rich fuel mixtures with a substantial level of turbulent kinetic energy and high combustion rates; the other one describes moderate combustion rates of lean fuel mixtures with less turbulent kinetic energy. Model constants were calibrated against experimental data from a 12.4L heavy-duty compression ignition engine operated on gasoline for various sweeps at 14bar BMEP and mostly at an engine speed of 1038rpm. A maximum prediction error in combustion phasing of 1.3CAD was found across the 30 calibrated sample points.
Pamminger, Michael, Hall, Carrie, Wang, Buyu, Wallner, Thomas, Rajkumar, M
Validation and Analysis of Heat Losses Prediction Using Conjugate Heat Transfer Simulation for an Internal Combustion Engine2019-24-00919/9/2019
New technologies are required to improve engine thermal efficiency. For this it is necessary to use all the tools available nowadays, in particular computational tools, which allow testing the viability of different solutions at reduced cost. In addition, numerical simulations often provide more detailed information than experimental tests. Such is the case for the study of the heat transfer through the walls of an engine. Conjugate Heat Transfer (CHT) simulations permit precise calculations of the heat transfer from gas to walls throughout the whole engine cycle, and thus it is possible to know such details as the instantaneous heat losses and wall temperature distribution on the walls, which no experiment can give. Nevertheless, it is important to validate CHT calculations, either with some experimental measurements or with some other reliable tool, such as 0D-1D modelling known to work well. The proposed work is based on the CHT simulation of the heat transfer to the walls of an engine piston during an entire cycle to determine the parameters that permit obtaining good results. This will be ascertained by comparison with the results of a lumped model previously validated for many applications. Another objective of this work is also to determine if it is significant to take into account the spatial and temporal variations of the wall temperature for the prediction of the heat losses during the engine cycle, as generally a mean and constant wall temperature (isothermal walls) is assumed for CFD combustion calculations.
Broatch, Alberto, Margot, Xandra, Garcia-Tiscar, Jorge, Escalona, Johan
Study of Fuel Octane Sensitivity Effects on Gasoline Partially Premixed Combustion Using Optical Diagnostics2019-24-00259/9/2019
Partially premixed combustion (PPC) is a low-temperature combustion concept that could deliver higher engine efficiency, as well as lower emissions. Gasoline-like fuel compression ignition (GCI) is beneficial for air/fuel mixing process under PPC mode because of the superior auto-ignition resistance to prolong ignition delay time. In current experiments, three surrogate fuels with same research octane number (RON77) but different octane sensitivities (OS), PRF77 (S = 0), TPRF77-a (S = 3) and TPRF77-b (S = 5), are tested in a full-transparent single cylinder AVL optical compression ignition (CI) engine at low load conditions. Aiming at investigating the fuel octane sensitivity effect on engine combustion behavior as well as emissions under GCI-PPC mode, engine parameters, and emission data during combustion are compared for the test fuels with a change of injection timing. In addition, in order to get a deeper insight into fuel OS effect on GCI-PPC mode, high-speed natural flame luminosity (NFL) imaging techniques are used for visualizing in-cylinder combustion processes. The results show that higher octane sensitivity generally lead to delayed start of combustion, prolonged ignition delay time, retarded combustion phasing of CA50 as well as extended combustion duration. At late injection timing of -15 CAD aTDC, higher IMEP is achieved with higher OS fuel along with lower maximum in-cylinder pressure. A 4% increase of IMEP is achieved by the test fuel with highest OS (TPRF77-b) as compared with zero sensitivity fuel (PRF77). Moreover, the fuel spray vaporization process is affected by fuel octane sensitivity, which introduces some bright tiny spots during the combustion process as well as higher UHC and CO emissions, especially for early injection timing.
Shi, Hao, An, Yanzhao, Johansson, Bengt
A Computationally Efficient Progress Variable Approach for In-Cylinder Combustion and Emissions Simulations2019-24-00119/9/2019
The use of complex reaction schemes is accompanied by high computational cost in 3D CFD simulations but is particularly important to predict pollutant emissions in internal combustion engine simulations. One solution to tackle this problem is to solve the chemistry prior the CFD run and store the chemistry information in look-up tables. The approach presented combines pre-tabulated progress variable-based source terms for auto-ignition as well as soot and NOx source terms for emission predictions. The method is coupled to the 3D CFD code CONVERGE v2.4 via user-coding and tested over various speed and load passenger-car Diesel engine conditions. This work includes the comparison between the combustion progress variable (CPV) model and the online chemistry solver in CONVERGE 2.4. Both models are compared by means of combustion and emission parameters. A detailed n-decane/α-methyl-naphthalene mechanism, comprising 189 species, is used for both online and tabulated chemistry simulations. The two chemistry solvers show very good agreement between each other and equally predict trends derived experimentally by means of engine performance parameters as well as soot and NOx engine-out emissions. The CPV model shows a factor 8 speed-up in run-time compared to the online chemistry solver without compromising the accuracy of the solution.
Matrisciano, Andrea, Netzer, Corinna, Werner, Adina, Borg, Anders, Seidel, Lars, Mauss, Fabian
Experimental and Numerical Investigation of the Maximum Pressure Rise Rate for an LTC Concept in a Single Cylinder CI Engine2019-24-00239/9/2019
In the foreseeable future, the transportation sector will continue to rely on internal combustion engines. Therefore, reduction of engine-out emissions and increase in engine efficiency are important goals to meet future legislative regulations and restricted fuel resources. One viable option, which provides lower peak temperatures and increased mixture homogeneity and thus simultaneously reduces nitric oxide as well as soot, is a low-temperature combustion (LTC) concept. However, this might result in an increase of unburnt hydrocarbon, carbon monoxide, and combustion noise due to early combustion phasing and lower engine efficiency. Various studies show that these drawbacks can be compensated by advanced injection strategies, e.g. by employing multiple injections. The aim of this work is to identify the optimum injection strategy, which enables a wide range of engine operating points in LTC mode with reduced engine-out emissions. To achieve this goal, experiments with variations in the maximum pressure rise rate, injection pressure, intake pressure, and the EGR-rate are carried out and analyzed. Numerical investigation is carried out by three dimensional (3D) computational fluid dynamics (CFD) simulations in CONVERGE software for several multiple injection strategy conditions. CFD could predict ignition delay, pressure rise and heat release rate of each injection and hence overall injection rate shaping combustion process with good accuracy.
Korkmaz, Metin, Lakshmanan, Raghavan, Falkenstein, Tobias, Beeckmann, Joachim, Pitsch, Heinz
Virtual Investigation of Real Fuels by Means of 3D-CFD Engine Simulations2019-24-00909/9/2019
The reduction of both harmful emissions (CO, HC, NOx, etc.) and gases responsible for greenhouse effects (especially CO2) are mandatory aspects to be considered in the development process of any kind of propulsion concept. Focusing on ICEs, the main development topics are today not only the reduction of harmful emissions, increase of thermodynamic efficiency, etc. but also the decarbonization of fuels which offers the highest potential for the reduction of CO2 emissions. Accordingly, the development of future ICEs will be closely linked to the development of CO2 neutral fuels (e.g. biofuels and e-fuels) as they will be part of a common development process. This implies an increase in development complexity, which needs the support of engine simulations. In this work, the virtual modeling of real fuel behavior is addressed to improve current simulation capabilities in studying how a specific composition can affect the engine performance. The goal is to create a series of models that allow to virtually investigate different fuels and to minimize, as much as possible, the costly and time-consuming experimental tests. In the first part, a fuel modeling approach is presented and compared with traditional methodologies. Subsequently, two fuel virtual investigations are presented. In the first, fuels with different RON and oxygenates content are compared to analyze their knock behavior and performance potential. In the second analysis, the fuel investigation - conducted virtually at the FKFS of Stuttgart and experimentally at the engine laboratory of the Chair of Internal Combustion Engines at the Technical University of Munich with the support from Volkswagen Motorsport GmbH - on a single-cylinder research engine operating with the innovative SACI (Spark Assisted Compression Ignition) combustion concept is presented.
Cupo, Francesco, Chiodi, Marco, Bargende, Michael, Koch, Daniel, Wachtmeister, Georg, Wichelhaus, Donatus
A Study of Flow Characteristics on the Diesel-Gasoline Dual-Fuel Combustion by 3-D CFD2019-24-01179/9/2019
Various advanced combustion concepts, which can achieve higher thermal efficiency and emissions reduction, have been suggested as the emissions regulation gets stricter. Dual-fuel combustion that operates by using different fuels having both premixed and non-premixed combustion characteristics is one of the viable alternatives. In dual-fuel combustion, it is critical to understand air-fuel mixture distribution as it determines the ignition spot and following combustion phase. The fuel distribution in the engine is affected by various factors, such as chamber geometry, injection strategy or in-cylinder flow motion. Furthermore, among them, in-cylinder motion, usually described in terms of swirl or tumble motion, is mostly affected by in-cylinder port geometry. In this paper, 3-dimensional Computational Fluid Dynamics (CFD) was used to investigate the effect of in-cylinder flow motion in dual-fuel combustion. Two head and port geometries were used in the simulations. One is the conventional diesel engine shape that has a flat head and intake ports with swirl-inducing shape; the other one has a pent-roof shape with straight intake port geometry. For the combustion model, the Representative Interactive Flamelet (RIF) model and G-equation were combined to solve the auto-ignition of direct-injected diesel fuel and the flame propagation of premixed gasoline fuel. For the chemical mechanism, the reduced Primary Reference Fuel (PRF) mechanism with 73 species and 296 reactions was used. The flow analysis was first conducted with different geometry cases under a full-mesh condition and was followed by the combustion analysis which was conducted under a sector mesh condition by using the flow simulation results as initial conditions. This paper illustrates the effect of difference in in-cylinder flow motion on the fuel distribution and combustion characteristics.
Moon, Sunyoung, Chu, Sanghyun, Nam, Taewoo, Min, Kyoungdoug
A Coupled Tabulated Kinetics and Flame Propagation Model for the Simulation of Fumigated Medium Speed Dual-Fuel Engines2019-24-00989/9/2019
The present work describes the numerical modeling of medium-speed marine engines, operating in a fumigated dual-fuel mode, i.e. with the second fuel injected in the ports. This engine technology allows reducing engine-out emissions while maintaining the engine efficiency and can be fairly easily retrofitted from current diesel engines. The main premixed fuel that is added can be a low-carbon one and can additionally be of a renewable nature, thereby reducing or even completely removing the global warming impact. To fully optimize the operational parameters of such a large marine engine, computational fluid dynamics can be very helpful. Accurately describing the combustion process in such an engine is key, as the prediction of the heat release and the pollutant formation is crucial. Auto-ignition of the diesel fuel needs to be captured, followed by the combustion and flame propagation of the premixed fuel. In this work, an approach based on tabulated kinetics has been used, to include detailed chemistry while still maintaining acceptable computation times. To allow for the modeling of a fumigated dual-fuel engine, this approach has been extended with a Coherent Flame Model (CFM), capable of tracking the premixed flame surface. This methodology has been validated for standard diesel operation, dual-fuel diesel/natural gas and diesel/methanol operation. The model has been applied under a variety of different loads, speeds, diesel substitution ratios and equivalence ratios to capture and study a large operating range. While still observing some discrepancies between certain simulations and the corresponding experiments, already a large improvement in the prediction of fumigated dual-fuel engine operation was observed with the proposed method.
Decan, Gilles, Lucchini, Tommaso, D'Errico, Gianluca, Verhelst, Sebastian
A Guide to Uncertainty Quantification for Experimental Engine Research and Heat Release Analysis03-12-05-00338/22/2019
Performing an uncertainty analysis for complex measurement tasks, such as those found in engine research, presents unique challenges. Also, because of the excessive computational costs, modeling-based approaches, such as a Monte Carlo approach, may not be practical. This work provides a traditional statistical approach to uncertainty analysis that incorporates the uncertainty tree, which is a graphical tool for complex uncertainty analysis. Approaches to calculate the required sensitivities are discussed, including issues associated with numerical differentiation, numerical integration, and post-processing. Trimming of the uncertainty tree to remove insignificant contributions is discussed. The article concludes with a best practices guide in the Appendix to uncertainty propagation in experimental engine combustion post-processing, which includes suggested post-processing techniques and down-selected functional relationships for uncertainty propagation.
Gainey, Brian, Longtin, Jon P., Lawler, Benjamin
Methodology to Perform Conjugate Heat Transfer Modeling for a Piston on a Sector Geometry for Direct-Injection Internal Combustion Engine Applications2019-01-02104/2/2019
The increase in computational power in recent times has led to multidimensional computational fluid dynamics (CFD) modeling tools being used extensively for optimizing the diesel engine piston design. However, it is still common practice in engine CFD modeling to use constant uniform boundary temperatures. This is either due to the difficulty in experimentally measuring the component temperatures or the lack of measurements when simulation is being used predictively. This assumption introduces uncertainty in heat flux predictions. Conjugate heat transfer (CHT) modeling is an approach used to predict the component temperatures by simultaneously modeling the heat transfer in the fluid and the solid phase. However, CHT simulations are computationally expensive as they require more than one engine cycle to be simulated to converge to a steady cycle-averaged component temperature. Furthermore, a piston design optimization study would involve large numbers of simulations and including CHT modeling would be impractical considering the computational expense. Accordingly, in the current publication, an approach to perform piston CHT simulations on sector geometries is proposed to reduce the computational time significantly with minimal impact on the prediction accuracy. The study was performed on a heavy-duty engine at a high load operating condition of 20 bar gross IMEP and engine speed of 1800 rev/min. Since the open cycle portion of the engine cycle cannot be simulated on a sector mesh, a scaling methodology was developed to account for the contribution of the open cycle to the wall heat transfer. The average and the maximum piston temperature from the sector CHT approach were predicted within 35 K and 25 K of the full geometry CHT simulation respectively. Additionally, the distribution of the temperature within the solid piston obtained from the sector CHT simulation was compared to the temperature distributions from a full CHT geometry and the results showed good agreement. The sector CHT approach resulted in a ~8x reduction in computational time on a 1/7 sector geometry.
Kavuri, Chaitanya, Anders, Jonathan
Comparison of Kinetic Mechanisms for Numerical Simulation of Methanol Combustion in DICI Heavy-Duty Engine2019-01-02084/2/2019
The combustion process in a homogeneous charge compression ignition (HCCI) engine is mainly governed by ignition wave propagation. The in-cylinder pressure, heat release rate, and the emission characteristics are thus largely driven by the chemical kinetics of the fuel. As a result, CFD simulation of such combustion process is very sensitive to the employed reaction mechanism, which model the real chemical kinetics of the fuel. In order to perform engine simulation with a range of operating conditions and cylinder-piston geometry for the design and optimization purpose, it is essential to have a chemical kinetic mechanism that is both accurate and computational inexpensive. In this paper, we report on the evaluation of several chemical kinetic mechanisms for methanol combustion, including large mechanisms and skeletal/reduced mechanisms. These mechanisms are evaluated in terms of homogeneous ignition delay time, laminar flame speed, and multi-phase simulations of HCCI heavy-duty engine. The results are compared with experimental data and evaluated in terms of the accuracy and computational cost. It was found that scattering of ignition delay time predicted from different chemical kinetic mechanisms reported in the literature under homogeneous mixture ignition conditions give rise to a high sensitivity of the engine in-cylinder pressure prediction to the selected mechanism.
Pucilowski, Mateusz, Li, Rui, Xu, Shijie, Li, Changle, Qin, Fei, Tuner, Martin, Bai, Xue-Song, Konnov, Alexander A.
Thermal Efficiency Improvement and its Mechanism at Low Load Conditions in Semi-Premixed Diesel Combustion with Twin Peak Shaped Heat Release2019-01-11534/2/2019
Semi-premixed diesel combustion with a twin peak shaped heat release with the two-stage fuel injection (twin combustion) has the potential to establish efficient, low emission, and low noise operation. However, with twin combustion at low loads the indicated thermal efficiencies are poorer than at medium loads due to the lower combustion efficiencies. In this report, to increase the combustion efficiencies at low loads, the thermal efficiency related parameters were investigated in a 0.55 L single cylinder diesel engine. The results show that the indicated thermal efficiency improves with increases in the intake gas temperatures at low loads. However, at the higher loads where the combustion efficiencies are somewhat higher the indicated thermal efficiencies decrease with increases in the intake gas temperatures due to increases in the cooling losses. At the low load condition below 300 kPa IMEP, the indicated thermal efficiency is higher and the combustion noise is lower in the twin combustion than in the single premixed combustion. Further, the combustion characteristics of twin and single premixed diesel combustion at low loads were analyzed with CFD simulation, showing that in the twin combustion, re-oxidation of the CO is promoted by the second-stage combustion and the indicated thermal efficiencies are higher than in the single premixed combustion due to higher combustion efficiencies. Both the heat flux value and the high heat flux area in the twin combustion are smaller than in the single premixed combustion due to decreases in the quantities of burned gas near the combustion chamber wall due to the separating of the fuel injections.
Inaba, Kazuki, Masuko, Yosuke, Zhang, Yanhe, Kobashi, Yoshimitsu, Shibata, Gen, Ogawa, Hideyuki
Novel Geometry Reaching High Efficiency for Multiple Injector Concepts2019-01-02464/2/2019
Heat losses are known to decrease the efficiency of CI engines largely. Here, multiple injectors have been suggested to shrink these losses through reduction of spray wall impingement. Studies on multiple injectors have proven the concept’s heat transfer reduction but also highlighted the difficulty of using a standard piston bowl. This study proposes a two-injector concept combined with a flat bowl to reduce heat losses further. To change the spray pattern, the two injectors are injecting in a swirling motion while placed at the rim of the bowl. Four injection timings have been investigated using Reynolds-Averaged Navier-Stokes simulations. This computational method quantified the amount of heat loss reduction possible. A conventional single injector concept is compared to two injector concepts with a standard and flat bowl. A Double Compression Expansion Engine (DCEE) concept, based on a modified Volvo D13 single-cylinder engine, was the base for all simulations. The DCEE can re-use the residual exhaust energy for a second expansion meaning increased importance of reduced heat losses. Heat release effects were discarded in the evaluation as an explanation for the reduced heat losses in order to isolate the effects of the changed spray pattern. Results showed a decrease in heat losses by 25.1 % or 4.2 % of the fuel energy as well as an increased IMEP of 4.5 % or 1.9 % of the fuel energy. Together with the increased exhaust energy, results showed a possible total engine efficiency increase of 2.6 % using the DCEE concept. This work successfully proves the benefits of using two injectors with a flat bowl over a standard bowl and the conventional one-injector strategy.
Nyrenstedt, Gustav, Im, Hong, Andersson, Arne, Johansson, Bengt
Φ-Sensitivity for LTGC Engines: Understanding the Fundamentals and Tailoring Fuel Blends to Maximize This Property2019-01-09614/2/2019
Φ-sensitivity is a fuel characteristic that has important benefits for the operation and control of low-temperature gasoline combustion (LTGC) engines. A fuel is φ-sensitive if its autoignition reactivity varies with the fuel/air equivalence ratio (φ). Thus, multiple-injection strategies can be used to create a φ-distribution that leads to several benefits. First, the φ-distribution causes a sequential autoignition that reduces the maximum heat release rate. This allows higher loads without knock and/or advanced combustion timing for higher efficiencies. Second, combustion phasing can be controlled by adjusting the fuel-injection strategy. Finally, experiments show that intermediate-temperature heat release (ITHR) increases with φ-sensitivity, increasing the allowable combustion retard and improving stability. A detailed mechanism was applied using CHEMKIN to understand the chemistry responsible for φ-sensitivity. For fuels with NTC behavior, φ-sensitivity is greatest in the NTC region due to enhanced ITHR reactions, which explains the experimental correlation between φ-sensitivity and ITHR. Under engine conditions, higher intake pressure means lower intake temperature to balance the reactivity, and both effects increase the φ-sensitivity. However, φ-sensitivity remains almost constant if decreased oxygen concentration is used to control the reactivity increase with intake-pressure boost because pressure and oxygen have opposite effects. Finally, for fuels without an NTC region, φ-sensitivity is lower and almost constant as operating conditions vary. The potential of designing fuel blends that increase the φ-sensitivity compared to RD5-87 (regular E10 gasoline), while maintaining high RON and octane-sensitivity, was investigated. Higher φ-sensitivity and higher RON than RD5-87 can be reached with a 5-component blend that meets U.S. regulations. The fuel mixture is composed of a combination of 1-hexene, n-pentane, iso-octane, p-xylene and iso-butanol (which was recently approved for gasoline in the U.S.). This study shows that it is possible to have both high φ-sensitivity and high RON with high octane-sensitivity.
Lopez Pintor, Dario, Dec, John, Gentz, Gerald
Effects of Compression Ratio and Water Vapor Induction on the Achievable Load Limits of a Light Duty Diesel Engine Operated in HCCI Mode2019-01-09624/2/2019
Among the various Low Temperature Combustion (LTC) strategies, Homogeneous Charge Compression Ignition (HCCI) is most promising to achieve near zero oxides of nitrogen (NOx) and particulate matter emissions owing to higher degree of homogeneity and elimination of diffusion phase combustion. However, one of its major limitations include a very narrow operating load range owing to misfire at low loads and knocking at high loads. Implementing HCCI in small light duty air cooled diesel engines pose challenges to eliminate misfire and knocking problems owing to lower power output and air cooled operation, respectively. In the present work, experimental investigations are done in HCCI mode in one such light duty production diesel engine most widely used in agricultural water pumping applications. An external mixture preparation based diesel HCCI is implemented in the test engine by utilizing a high-pressure port fuel injection system, a fuel vaporizer and an air preheater. With an existing compression ratio of 17.5, the engine could not be operated beyond 20% of rated BMEP owing to severe knocking. The existing bowl shaped piston is modified into a flat piston which is justified by the fact that fuel-air mixing has minimal or negligible role in HCCI combustion. In order to examine the effects of compression ratio on the achievable load range in HCCI, the geometric compression ratio is reduced in incremental steps from 17.5 to 11.5 with an interval of 2.5 by reducing the piston crown thickness. However, the compression ratio could not be reduced below 11.5 with the existing piston design. The results obtained show that the load range could be extended up to 57% by reducing the compression ratio to 11.5 without utilizing exhaust gas recirculation. It is also intended to examine the effects of water vapor induction on the achievable load range in HCCI. For this purpose, 20 ultrasonic atomizers with 1.7 MHz vibration frequency are utilized to produce water vapor which is inducted along with diesel vapor and air during the engine suction stroke. The homogeneous mixture of diesel vapor, water vapor and air is ignited during the engine compression stroke at a fixed compression ratio of 15. The water vapor concentration is varied from 0.8 mg/cycle to 2.4 mg/cycle by using a control valve. The results obtained shows that the load range could be extended up to 50% in HCCI by utilizing water vapor induction. At a fixed load condition, water vapor induction reduces NOx and smoke emissions, while unburned emissions are higher compared to the results obtained with reducing compression ratio because of lower temperatures and displacement of intake oxygen. Overall, the present work shows that either by reducing the geometric compression ratio or by utilizing water vapor induction, there is a greater potential to increase the load range of diesel HCCI engines.
M, Murugesa Pandian, Krishnasamy, Anand
Effects of Single versus Two-Stage Heat Release on the Load Limits of HCCI Using Primary Reference Fuels2019-01-09504/2/2019
Homogeneous Charge Compression Ignition (HCCI) enables combustion with high efficiency and low emissions. Control over the combustion process and its narrow operating range are still the biggest challenges associated with HCCI. To expand the operable load ranges of HCCI, this paper explores the effects of single versus two-stage ignition fuels by studying the Primary Reference Fuels (PRF) in a variable compression ratio Cooperative Fuel Research (CFR) engine. The PRF fuels, iso-octane and n-heptane, are blended together at various concentrations to create fuel blends with different autoignition characteristics. Experiments were conducted using these PRF blends to explore the extent to which the load range can be extended with two-stage ignition fuels at various compression ratios and intake temperatures. The reactivity of the PRF blends increases with the fraction of n-heptane and so does the amount of low temperature heat release (LTHR). Since the low PRF number fuels have a higher reactivity, they can be autoignited at very low compression ratios while maintaining comparable combustion phasing and equivalence ratios. At the lower compression ratios, the low load limits were found to be extended while maintaining high combustion efficiencies. Additionally, lower peak pressures and pressure rise rates were achieved at low PRF number fuels as a result of its two-stage heat release, which can be used to reach higher loads. In addition, the energy released from the LTHR can be used to delay the CA50 combustion phasing (i.e., the crank angle timing where 50% of the energy has been released) beyond what is possible with a single-stage ignition fuel, which allows further high load extension. However, using lower compression ratios has a negative impact on the thermal efficiency. The effects of the extended load, single- and two-stage heat release, combustion phasing, and equivalence ratios on combustion efficiency, thermal efficiencies, and combustion durations were also explored.
Hariharan, Deivanayagam, Yang, Ruinan, Mamalis, Sotirios, Lawler, Benjamin
Modeling the Effect of Thermal Barrier Coatings on HCCI Engine Combustion Using CFD Simulations with Conjugate Heat Transfer2019-01-09564/2/2019
Thermal barrier coatings with low conductivity and low heat capacity have been shown to improve the performance of homogeneous charge compression ignition (HCCI) engines. These coatings improve the combustion process by reducing heat transfer during the hot portion of the engine cycle without the penalty thicker coatings typically have on volumetric efficiency. Computational fluid dynamic simulations with conjugate heat transfer between the in-cylinder fluid and solid piston of a single cylinder HCCI engine with exhaust valve rebreathing are carried out to further understand the impacts of these coatings on the combustion process. For the HCCI engine studied with exhaust valve rebreathing, it is shown that simulations needed to be run for multiple engine cycles for the results to converge given how sensitive the rebreathing process is to the residual gas state. The effect of thermal barrier coatings on the piston surface is explored using the properties of Yttria-Stabilized Zirconia (YSZ) and Gadolinium Zirconate (GdZr) top coatings with two different thicknesses. Heat flux measurements from an experimental engine with an all metal piston and YSZ and GdZr thermal barrier coatings are compared to the simulation results and the simulation is found to under predict heat transfer. Reducing the conductivity of the coating advances combustion as does increasing the thickness of the coating.
Killingsworth, Nick, Powell, Tom, O'Donnell, Ryan, Filipi, Zoran, Hoffman, Mark
Experimental Investigations to Extend the Load Range of Premixed Charge Compression Ignited Light Duty Diesel Engine through Fuel Modifications2019-01-09534/2/2019
Premixed Charge Compression Ignition (PCCI) is one of the most promising low temperature combustion (LTC) strategies to achieve near zero oxides of nitrogen (NOx) and particulate matter (PM) emissions along with higher thermal efficiency. One of the major problems in diesel PCCI is a narrow operating load range because of very early ignition and knocking combustion at higher loads owing to higher reactivity of diesel fuel. Further, low volatile diesel resist vaporization, resulting in fuel spray wall wetting and higher unburned emissions in PCCI. Thus, high reactivity and low volatility of diesel fuel make it not suitable for PCCI combustion. The present work attempts to address these limitations, by blending diesel with high volatile and low reactive fuels, viz. gasoline and butanol at 10% and 20% blend levels by volume. A production light duty air cooled diesel engine most widely used in agricultural water pumping applications is modified to run in PCCI mode by replacing an existing mechanical fuel injection system with a flexible common rail injection system. The test engine is initially run in diesel PCCI mode to establish the baseline reference data. The direct injected (DI) diesel fuel timings and exhaust gas recirculation (EGR) concentration are optimized at each load conditions to achieve maximum brake thermal efficiency. The results obtained show that the engine could be operated only upto 40% of rated load in diesel PCCI mode beyond which it knocks severely. The engine is then operated with diesel-gasoline and diesel-butanol blends at 10% and 20% blend levels at similar operating conditions. Among the investigated fuel blends, 20% butanol with 80% diesel (DB20) perform better in terms of achievable load range and lower carbon monoxide emissions. Optimization of DI timings and EGR concentration with DB20 helps to extend the load range upto 60% of rated load. The NOx and smoke emissions are significantly lower in PCCI with all the tested fuels.
Gupta, Saurabh K, Krishnasamy, Anand
Evaluation of Knock Intensity and Knock-Limited Thermal Efficiency of Different Combustion Chambers in Stoichiometric Operation LNG Engine2019-01-11374/2/2019
Liquefied natural gas (LNG) engine could provide both reduced operating cost and reduction of greenhouse gas (GHG) emissions. Stoichiometric operation with EGR and the three-way catalyst has become a potential approach for commercial LNG engines to meet the Euro VI emissions legislation. In the current study, numerical investigations on the knocking tendency of several combustion chambers with different geometries and corresponding performances were conducted using CONVERGE CFD code with G-equation flame propagation model coupled with a reduced natural gas chemical kinetic mechanism. The results showed that the CFD modeling approach could predict the knock phenomenon in LNG engines reasonably well under different thermodynamic and flow field conditions. The predicted threshold between “no knock” and “knock” conditions was found to be in good agreement with experimental results, which means it provides a valid way to estimate the capability of knock suppression and knock-limited thermal efficiency for the design and optimization of LNG combustion system. Based on the validated CFD model, the effects of combustion chamber structures on turbulent flow and combustion process were discussed. The results showed that lower mean flow velocity in the spark plug region and higher turbulent kinetic energy in the center of the combustion chamber and near the spark plug can be obtained with a shallow re-entrant chamber geometry at the time of ignition and during the early combustion stage, which could effectively promote the initial flame propagation. However, the knock propensity is also higher compared to other combustion chamber geometries, mainly due to the preheating of the flame front in the squish crevices and the suppression of flame propagation to the bottom of the combustion chamber, which limits the thermal efficiency improvement. In addition, it’s found that the thermal efficiency of the current LNG engine with aluminum piston is restricted by both the knock and durable peak in-cylinder pressure (mechanical strength). Therefore, it’s essential to develop effective combustion and knock control strategies under higher peak in-cylinder pressure conditions (with higher CR steel piston) to further improve the thermal efficiency of stoichiometric LNG engine.
Zhao, Xumin, Wang, Hu, Zheng, Zunqing, Yao, Mingfa, Sheng, Li, Zhu, Zan
Triple Injection Strategies for Gasoline Compression Ignition (GCI) Combustion in a Single-Cylinder Small-Bore Common-Rail Diesel Engine2019-01-11484/2/2019
Implementing triple injection strategies in partially premixed charge-based gasoline compression ignition (GCI) engines has shown to achieve improved engine efficiency and reduced NOx and smoke emissions in many previous studies. While the impact of the triple injections on engine performance and engine-out emissions are well known, their role in controlling the mixture homogeneity and charge premixedness is currently poorly understood. The present study shows correspondence between the triple injection strategies and mixture homogeneity/premixedness through the experimental tests of second/third injection proportion and their timing variations with an aim to explain the observed GCI engine performance and emission trends. The experiments were conducted in a single cylinder, small-bore common-rail diesel engine fuelled with a commercial gasoline fuel of 95 research octane number (RON) and running at 2000 rpm and 830 kPa indicated mean effective pressure conditions. While the first injection proportion and timing were fixed at 40% and 170 °CA bTDC, the second injection proportion was varied between 5 and 20% (i.e. third injection of 40~55%) and the timing was varied from 20 to 80 °CA bTDC. The third injection timing was also swept from 2 to 11 °CA bTDC. The results show that increased second injection proportion causes higher peak in-cylinder pressure and apparent heat release rate (aHRR) due to increased charge premixing. This leads to lower smoke emissions but increased combustion-induced noise and NOx emissions. Despite higher peak in-cylinder pressure, the engine efficiency shows a decreasing trend with increased second-injection proportion because of the lower late-cycle pressure at the expansion stroke and increased wall wetting. Advanced second injection timing leads to lower peak in-cylinder pressure and aHRR and thereby decreasing engine efficiency, which is associated with the increased mixture homogeneity. Consequently, the smoke/NOx and combustion-induced noise emissions are reduced while the uHC emissions become higher, similar to homogeneous charge compression ignition (HCCI) combustion. In comparison, the advanced third injection timing leads to higher peak in-cylinder pressure and aHRR as well as lower uHC/CO emissions suggesting increased charge premixing with no wall wetting concerns. However, the engine efficiency shows a decreasing trend because of the lower expansion pressure. A typical smoke-NOx trade-off is found with decreasing smoke and increasing NOx emissions which once again indicates increased charge premixing.
Liu, Xinyu, Goyal, Harsh, Kook, Sanghoon, Ikeda, Yuji
The Relevance of Different Fuel Indices to Describe Autoignition Behaviour of Gasoline in Light Duty DICI Engine under PPC Mode2019-01-11474/2/2019
Partially premixed combustion (PPC) with gasoline fuels is a new promising combustion concept for future internal combustion engines. However, many researchers have argued the capabilities of research octane number (RON) and Motor Octane Number (MON) to describe the autoignition behaviour of gasoline fuels in advanced combustion concepts like PPC. The objective of this study is to propose a new method, called PPC number, to characterize the auto ignition quality of gasoline fuels in a light-duty direct injected compression ignition engine under PPC conditions. The experimental investigations were performed on a 4-cylinder Volvo D4 2 litre engine. The ignition delay which was defined as the crank angle degrees between the start of injection (SOI) and start of combustion (SOC) was used to represent the auto ignition quality of a fuel. The ignition delays of primary reference fuels PRF (blends of n-heptane and iso-octane) were used to develop a reference curve where a PPC metric for gasoline could be based on. The PPC number of a specific gasoline is defined as the octane number of the PRF, which has the same ignition delay as gasoline under the same operating condition. Twelve different gasolines, having RON values between 55 and 95, were tested at two different operating conditions of 0% exhaust gas recirculation (EGR) and 40% EGR levels namely Case0 and Case40 respectively. The intake pressures of Case0 and Case40 were 1.5 bar and 1.8 bar respectively with a constant inlet temperature of 110oC. The PPC numbers of all gasolines were measured and the relevancy of the other indices such as RON, MON, Octane Index and HCCI number were assessed. When the indices were compared, PPC number showed consistence and continues correlations with ignition delays in both conditions. Results also revealed that the spray target and piston geometry gave a big impact to the auto ignition quality of fuels.
Aziz, Amir, Li, Changle, Verhelst, Sebastian, Tuner, Martin
Engine-Aftertreatment in Closed-Loop Modeling for Heavy Duty Truck Emissions Control2019-01-09864/2/2019
An engine-aftertreatment computational model was developed to support in-loop performance simulations of tailpipe emissions and fuel consumption associated with a range of heavy-duty (HD) truck drive cycles. For purposes of this study, the engine-out exhaust dynamics were simulated with a combination of steady-state engine maps and dynamic correction factors that accounted for recent engine operating history. The engine correction factors were approximated as dynamic first-order lags associated with the thermal inertia of the major engine components and the rate at which engine-out exhaust temperature and composition vary as combustion heat is absorbed or lost to the surroundings. The aftertreatment model included catalytic monolith components for diesel exhaust oxidation, particulate filtration, and selective catalytic reduction of nitrogen oxides (NOx) with urea. Both the engine and aftertreatment models have been calibrated with dynamometer measurements from a commercial 2010-certificated 15-L Cummins diesel engine. The fuel consumption engine map with the reduced data is attached in the appendix. Simulations with the combined engine and aftertreatment models above appear to reveal important trends among the fuel efficiency, emissions control, power demand for HD trucks under realistic drive cycle conditions. Thus, this type of computational simulation appears to have significant value in choosing among options for HD vehicle design and operation.
Gao, Zhiming, Deter, Dean, Smith, David, Pihl, Josh, Daw, C. Stuart, Parks, James
The Physical and Chemical Effects of Fuel on Gasoline Compression Ignition2019-01-11504/2/2019
In the engine community, gasoline compression ignition (GCI) engines are at the forefront of research and efforts are being taken to commercialize an optimized GCI engine in the near future. GCI engines are operated typically at Partially Premixed Combustion (PPC) mode as it offers better control of combustion with improved combustion stability. While the transition in combustion homogeneity from convectional Compression Ignition (CI) to Homogenized Charge Compression Ignition (HCCI) combustion via PPC has been comprehensively investigated, the physical and chemical effects of fuel on GCI are rarely reported at different combustion modes. Therefore, in this study, the effect of physical and chemical properties of fuels on GCI is investigated. In-order to investigate the reported problem, low octane gasoline fuels with same RON = 70 but different physical properties and sensitivity (S) are chosen. Fuels with comparable sensitivity and RON are chosen to study the impact of physical properties on GCI. On the other hand, by keeping the same RON and physical properties, the effect of sensitivity on GCI is investigated. In this regard, three test fuels such as RON 70 gasoline (S=0.7), PRF 70 (S=0) and RON 70 gasoline (S=7) are chosen in the present study. Herein, RON 70 gasoline (S=0.7) and PRF 70 have similar RON and sensitivity but different physical properties; however, RON 70 gasoline (S=0.7) and RON 70 gasoline (S=7) have the same RON and physical properties but different sensitivity. These test fuels were tested in a heavy-duty CI engine at a compression ratio of 17.8 under different combustion modes. The experimental investigation reveals that RON 70 gasoline (S=0.7) and PRF 70 (S=0) behaves the same in terms of combustion behavior (combustion phasing, ignition delay, in cylinder pressure and rate of heat release) regardless of the difference in physical properties. While nitrogen oxide (NOX) and soot emissions are comparable between RON 70 gasoline (S=0.7) and PRF 70 at all combustion modes, the hydrocarbon (HC) and carbon monoxide (CO) emissions are slightly higher for PRF 70 when compared to RON 70 gasoline (S=0.7) at HCCI mode but not at PPC and CI modes due to the impact of physical properties. On the other hand, due to higher sensitivity, the reactivity for RON 70 gasoline (S=7) is improved to advance the combustion phasing at HCCI combustion mode when compared to RON 70 gasoline (S=0.7). At HCCI mode, the HC emissions are lower for high sensitive gasoline when compared to low sensitive gasoline whereas they are comparable at PPC and CI combustion modes. The NOX and soot emissions are comparable at HCCI modes whereas high sensitivity gasoline shows slightly decreased NOX and increased soot emissions, respectively, at PPC and CI combustion modes when compared to low sensitive gasoline.
Vallinayagam, R., Hlaing, Ponnya, AlRamadan, Abdullah S., An, Yanzhao, Sim, Jaeheon, Chang, Junseok, Johansson, Bengt
Numerical Analysis on the Effect of Piston Bowl Geometry in Gasoline-Diesel Dual-Fuel Combustion2019-01-11644/2/2019
As emissions regulations become stricter, a variety of advanced combustion concepts that can reduce emissions with a higher thermal efficiency have been suggested. Dual-fuel combustion is one of the alternatives that has both premixed and non-premixed combustion characteristics. Knowing the effects of the mixture formation in dual-fuel combustion is important because it determines the ignition location and the following combustion phase. Hence, a thorough investigation on the related factors, such as the engine hardware or fuel spray, is required. Meanwhile, Computational Fluid Dynamics (CFD) is a good technique to visualize the in-cylinder phenomena and enables quantitative investigations into the detailed combustion characteristics. In this paper, a 3-dimensional CFD simulation was used to investigate the effects of the mixture formation in dual-fuel combustion. The combustion model consists of two parts. The Representative Interactive Flamelet (RIF) model was used to solve the auto-ignition of the direct injected fuel, and the level-set approach was used to mimic the flame propagation. The reduced Primary Reference Fuel (PRF) mechanism with 73 species and 296 reactions was used. The combustion model was validated with experimental results under gasoline-diesel dual-fuel combustion in a single cylinder diesel engine where the diesel-gasoline ratio was varied. Then, the effects of the mixture formation on the combustion and emissions characteristics were investigated by changing the piston bowl shape. The model showed good agreement with the experimental results, and it could quantitatively analyze how the spray targeting affects the emissions reduction and thermal efficiency.
Moon, Sunyoung, Kim, Gyujin, Chu, Sanghyun, Kang, Jaegu, Min, Kyoungdoug, Choi, Hoimyung, Ha, Taehun
CFD-Guided Combustion System Optimization of a Gasoline Range Fuel in a Heavy-Duty Compression Ignition Engine Using Automatic Piston Geometry Generation and a Supercomputer2019-01-00011/15/2019
A computational fluid dynamics (CFD) guided combustion system optimization was conducted for a heavy-duty diesel engine running with a gasoline fuel that has a research octane number (RON) of 80. The goal was to optimize the gasoline compression ignition (GCI) combustion recipe (piston bowl geometry, injector spray pattern, in-cylinder swirl motion, and thermal boundary conditions) for improved fuel efficiency while maintaining engine-out NOx within a 1-1.5 g/kW-hr window. The numerical model was developed using the multi-dimensional CFD software CONVERGE. A two-stage design of experiments (DoE) approach was employed with the first stage focusing on the piston bowl shape optimization and the second addressing refinement of the combustion recipe. For optimizing the piston bowl geometry, a software tool, CAESES, was utilized to automatically perturb key bowl design parameters. This led to the generation of 256 combustion chamber designs evaluated at several engine operating conditions. The second DoE campaign was conducted to optimize injector spray patterns, fuel injection strategies and in-cylinder swirl motion for the best performing piston bowl designs from the first DoE campaign. This comprehensive optimization study was performed on a supercomputer, Mira, to accelerate the development of an optimized fuel-efficiency focused design. Compared to the production combustion system in the baseline engine, the new combustion recipe from this study showed significantly improved closed-cycle fuel efficiency across key engine operating points while meeting the engine-out NOx targets. Optimized piston bowl designs and injector spray patterns were predicted to provide enhanced in-cylinder air utilization and more rapid mixing-controlled combustion, thereby leading to a fuel efficiency improvement. In addition, shifting the engine thermal boundary conditions toward leaner operation was also key to the improved fuel efficiency.
Pei, Yuanjiang, Pal, Pinaki, Zhang, Yu, Traver, Michael, Cleary, David, Futterer, Carsten, Brenner, Mattia, Probst, Daniel, Som, Sibendu
CFD Study of Heat Transfer Reduction Using Multiple Injectors in a DCEE Concept2019-01-00701/15/2019
Earlier studies on efficiency improvement in CI engines have suggested that heat transfer losses contribute largely to the total energy losses. Fuel impingement on the cylinder walls is typically associated with high heat transfer. This study proposes a two-injector concept to reduce heat losses and thereby improve efficiency. The two injectors are placed at the rim of the bowl to change the spray pattern. Computational simulations based on the Reynolds-Averaged Navier-Stokes approach have been performed for four different fuel injection timings in order to quantify the reduction in heat losses for the proposed concept. Two-injector concepts were compared to reference cases using only one centrally mounted injector. All simulations were performed in a double compression expansion engine (DCEE) concept using the Volvo D13 single-cylinder engine. In the DCEE, a large portion of the exhaust energy is re-used in the second expansion, thus increasing the thermodynamic efficiency. To isolate the heat losses associated with the changed spray pattern of the two-injector concept, effects of the heat release are excluded during the analysis. Results showed that the optimal injection strategy allows a decrease in the temperature close to the walls, leading to heat loss reduction up to 13 % or 2 % of the fuel energy. The residual exhaust energy was increased by 1.5 %-points with the two-injector concept when compared to the reference case. This proved the advantage of the two-injector concept compared to conventional single injector case for the DCEE application.
Nyrenstedt, Gustav, Alturkestani, Tariq, Im, Hong, Johansson, Bengt
Optimized In Cylinder NOx Reduction Strategy for Meeting BSVI Emission Limits2019-26-01421/9/2019
The tough emission limits of BSVI norms with very low levels of NOx and PM emissions presents major techno economic challenges for the automobile industry. Combined efforts of pollutants reduction by combustion modification as well as the exhaust after treatment devices could only facilitate to achieve the desired emission targets. selective catalytic reduction technology is a mandatory system which uses ammonia from the aqueous urea solution to react with NOx forming nontoxic by products. The cost spent on aqueous urea solution in addition to the cost of BSVI diesel encounters high operating cost for the vehicle. NOx reduction by SCR too requires adequate quantity of ammonia from the AdBlue. Hence sensible utilization of DEF is essential for reduced running cost of the SCR system. SCR efficiency is higher for higher exhaust temperature and it requires minimum exhaust temperature above which only it operates. For conditions like cold start and low temperature combustion, SCR may not be effective and combustion optimization is the only way to reduce NOx. This article focuses on the reduction of NOx emission of the 2.2 l engine on adjustment of EGR rate and Main injection timing on different operating points on various equivalence ratios. The operating points for optimization were determined by conducting various drive trials on different type of road conditions along with consideration of NEDC. NOx, BSFC, soot and CO were measured and studied thoroughly from richer to leaner fuel-air mixtures. Calibration strategy involved the safe limits of NOx, soot, CO emissions and fuel consumption. Combustion optimization for NOx reduction was done keeping the in mind the consumption of DEF as well as diesel and the cost factor of both. Finally the best fit of strategy for reduced NOx and fuel consumption was arrived ensuring lower operating fuel and DEF cost.
Muthusamy, Anbarasu, Shangar Ramani, Vagesh, Sinha, Pranav Kumar, J, Giftson, R, Sivasubramamanian, Halbe, Vasudeo Ganesh
Influences of Butanol Blends on Combustion and Emissions of a Small SI Engine2018-32-005810/30/2018
In the general efforts to replace the fossil fuels in transportation by renewable fuels the bioalcohols are an important alternative. The global share of Bioethanol used for transportation is continuously increasing. Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for Gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than Ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. In the present work research with different nButanol portions in gasoline (BuXX)* was performed on the 2-cylinder SI engine with variations of several parameters on engine dynamometer. At different steady state operating points were varied: spark timing (αz), air excess factor (λ) and EGR-rate. Furthermore, the conversion rates and light-off of a 3-way-catalyst were investigated. As research tools the combustion pressure indication and the exhaust gas analysis were used. In the steady state operation, it was found that Bu-blends generally reduce the emissions of CO, HC, NOx in untreated exhaust gas and have a very little influence on catalytic conversion rates of the 3-way-catalyst. At lower engine part load, “Bu” shortens the inflammation lag and reduces the cyclic dispersion of combustion. Nevertheless, this advantage disappears at higher engine loads and with higher “Bu” portions. The present paper shows some examples of the most important results.
Czerwinski, Jan, Güdel, Martin, Engelmann, Danilo, Pechout, Martin
Effects of In-Cylinder Flow and Stratified Mixture on HCCI Combustion in High Load2018-32-001610/30/2018
The purpose of this paper is to find a way to extend the high load limit of homogeneous charge compression ignition (HCCI) combustion. This paper presents the effect of in-cylinder flow and stratified mixture on HCCI combustion by experiments and three-dimensional computer fluid dynamics coupled with a detailed chemical reaction calculation. The first study was conducted using a rapid compression and expansion machine (RCEM) equipped with a flow generation plate to create in-cylinder turbulent flow and with a control unit of in-cylinder wall temperature to create in-cylinder temperature distribution. The study assesses the effect of the turbulent flow and the temperature distribution on HCCI combustion. In the second study, the numerical simulation of HCCI combustion was conducted using large eddy simulation coupled with a detailed chemical reaction calculation. The study analyzes the interaction between in-cylinder turbulent flow and mixture distribution and HCCI combustion. The result shows that turbulent flow effects a change in the distribution of chemical species which is a trigger of combustion initiation.
Yoshimura, Kei, Watanabe, Shogo, Ogawa, Kazuya, Kuboyama, Tatsuya, Moriyoshi, Yasuo
Diesel CAI Combustion in Uniflow Scavenging 2-Stroke Engine Provided with Port Fuel Injection Device2018-32-001510/30/2018
We studied a simple and cost effective controlled auto ignition (CAI) combustion engine in order to achieve simultaneous reduction of NOx and soot, which are issues in diffusion combustion. The engine type was a uniflow scavenging 2-stroke engine, and the fuel used was diesel, as is common in diesel engines. We examined the position of the injector that effectively forms the premixture and realized stable operation with diesel fuel by the low pressure fuel injection device for port fuel injection (PFI), and it was found that the CAI combustion ignition timing can be controlled through setting the air/fuel ratio that obtains the optimal ignition timing per operation conditions. As a result of verifying the potential of this engine, it was confirmed that the regulation emissions level required for joint use of common rail fuel injection system (CRS), exhaust gas recirculation (EGR), diesel particulate filter (DPF), diesel oxidation catalyst (DOC), etc. in nonroad compression ignition (NRCI) engines can be achieved only by exhaust aftertreatment with a DOC. Furthermore, it was confirmed that break mean effective pressure (BMEP) equivalent to 4-stroke is about the same level as naturally aspirated NRCI engines and specific fuel consumption (SFC) has the potential to be about the same level or lower than NRCI engines with displacement of less than 2000 cm3.
Kurata, Mashu, Yamada, Yoshikazu
Cylinder Selective Combustion, the New Diesel Dual Fuel Combustion Control Concept for Low Load Operating Condition2018-01-17339/10/2018
Diesel dual fuel (DDF) operated under moderate load condition emits a lot of CH4 and CO. Even these emissions have been improved significantly by Dual Fuel Premixed Charge Compression Ignition: DF-PCCI [3] combustion control technique which was proposed by the authors. However, the emission was still high as compared to diesel emissions. To overcome this problem, the new combustion control concept so called Cylinder Selective Combustion (CSC) has been proposed. From the fact that at low load condition, diesel combustion has lower CH4 and CO emissions than DDF combustion and DDF emissions can be improved significantly by DF-PCCI concept at higher load. So, in the new concept, some cylinder was selected to run with very low IMEP diesel combustion and some cylinder was selected to run with higher IMEP DF-PCCI combustion. The IMEP ratios between DF-PCCI and diesel have been optimized for each engine speed and engine load. The engine and vehicle test results showed that the CSC concept could be utilized with smooth engine running without any misfire meanwhile the CH4 and CO emissions can be reduced significantly.
Wannatong, Krisada, Tepimonrat, Thananchai, Kongviwattanakul, Sompach
Split Injection Spray Development, Mixture Formation, and Combustion Processes in a Diesel Engine Piston Cavity: Rig Test and Real Engine Results2018-01-16989/10/2018
The objectives of this study are to investigate the effects of premixed charge compression ignition (PCCI) strategies with split injection on soot emission characteristics. The split injection conditions included three injection intervals (1.1 ms, 1.3 ms, and 1.5 ms) and three injection quantity fraction ratios (Q1/Q2 = 10.0/14.6 mm3/st, 15.2/9.4 mm3/st, and 20.0/4.6 mm3/st). The results in real engine tests showed that shorter injection intervals, and the 1st injection quantity contributes to reduced soot emissions. A rig test with high-pressure and high-temperature constant-volume vessel (CVV) and a two-dimensional (2D) model piston cavity were used to determine correlations between injection conditions and soot emissions. During the rig test, fuel was injected into the CVV by a single-hole nozzle under split injection strategies. The injection strategies include the same injection intervals and quantity fraction ratios as in the real engine test. The 2D piston cavity model took the same shape as that used in a small-bore diesel engine to investigate spray development, mixture formation, and combustion process. Tracer laser absorption scattering (LAS) was used to observe the spray development and mixture formation processes without combustion. The spatial distributions of the vapor and liquid phases and spray mixture formation characteristics in the 2D piston cavity were investigated. Spray combustion and soot formation processes were studied using a high-speed video camera. The flame structure and soot formation process were examined using two-color pyrometry. The experimental results revealed that the split injection interval and mass fraction ratio influence the characteristics of the mixture formation and soot formation processes in the 2D piston cavity. The rig test results show that the correlation between soot emission characteristics and injection strategies is similar to that observed in the rig test.
Shiwaku, Tomoya, Yasaki, Shintaro, Nishida, Keiya, Ogata, Youichi, Suzuki, Mamoru, Umehara, Tsutomu
Effects of Injection Rate Profiles on Auto-Ignition in Ignition Quality Tester2018-01-16959/10/2018
Ignition quality tester (IQT) is a standard experimental device to determine ignition delay time of liquid fuels in a controlled environment in the absence of gas exchange. The process involves fuel injection, spray breakup, evaporation and mixing, which is followed by auto-ignition. In this study, three-dimensional computational fluid dynamics (CFD) is used for prediction of auto-ignition characteristics of diethyl ether (DEE) and ethanol. In particular, the sensitivity of the ignition behavior to different injection rate profiles is investigated. Fluctuant rate profile derived from needle lift data from experiments performs better than square rate profile in ignition delay predictions. DEE, when used with fluctuant injection rate profile resulted in faster ignition, while for ethanol the situation was reversed. The contrasting results are attributed to the difference in local mixing. The fluctuant injection profile yields larger spray velocity variations promoting fuel evaporation and local turbulent mixing. The suitable ignition conditions were reached earlier for DEE with fluctuant injection profile, whereas ethanol exhibits pseudo-homogeneous mixing due to its lower cetane number. Ignition was faster for square rate profile due to ignition in end tube for ethanol. The fluctuant injection leads to a better homogeneity for ethanol due to longer time available for mixing. The nature of heat release rate, auto-ignition and combustion were altered by the fluctuant injection rate profile when compared to square rate injection profile.
Luo, Yueqi, Mubarak Ali, Mohammed Jaasim, Huang, Zhen, Im, Hong
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