Browse Topic: Fuel injection

Items (1,067)
ABSTRACT The US Army is seeking improvements in the fuel efficiency of their military vehicles.. They have initiated a number of R&D projects aimed at advancing the state-of-the-art of powertrain efficiency including demonstration in a laboratory environment. This effort will set a benchmark for the vehicle integrators, allowing them to improve future vehicle offerings. The SAIC, AVL, Badenoch, QinetiQ and Ker-Train Research team offered powertrain solutions from 7 Tons to 40 Tons that achieved the goal of 44% thermal efficiency and the stringent flexible fuel and emissions requirements. In each of these offerings the team was able to identify modifications to existing engines that allowed dramatic improvements in the thermal efficiency. These efficiency improvements were achieved through a combination of techniques, combustion cycle adjustments using in-cylinder pressure monitoring and precise control of fuel injector timing, and turbo-compounding. For the R&D project, the fuel injector timing will be controlled using commercial engine development hardware and software. The high speed hardware emulates the engine control module but allows the developer to finely tune the fuel injection to maximize the 50% Maximum Fuel Burn point (MFB50) with only limited NOx production. This will be accomplished using a variety of fuels and maintaining the output power to within 2% of the engine’s nominal rating. This paper will describe the fundamental diesel combustion process that must be controlled and techniques for usable power extraction from the waste exhaust gases to provide this performance. It will describe the engine development tools that enable these controls changes to be realized within a vehicle development cycle and retain the baseline engine maturity.
McDowell, JimHunter, Gary L.Hennessy, Chris
Abstract Earlier studies have proven how ducted fuel injection (DFI) substantially reduces soot for low- and mid-load conditions in heavy-duty engines, without significant adverse effects on other emissions. Nevertheless, no comprehensive DFI study exists showing soot reductions at high- and full-load conditions. This study investigated DFI in a single-cylinder, 1.7-L, optical engine from low- to full-load conditions with a low-net-carbon fuel consisting of 80% renewable diesel and 20% biodiesel. Over the tested load range, DFI reduced engine-out soot by 38.1–63.1% compared to conventional diesel combustion (CDC). This soot reduction occurred without significant detrimental effects on other emission types. Thus, DFI reduced the severity of the soot–NOx tradeoff at all tested conditions. While DFI delivered considerable soot reductions in the present study, previous DFI studies at low- and mid-load conditions delivered larger soot reductions (>90%) compared to CDC operation at the same conditions. Therefore, the DFI configuration used here has been deemed nonoptimal (in terms of parameters such as the injector-spray and piston geometries), and several improvements are recommended for future studies with high-load DFI. These improvements include employing better spray-duct alignment, a deeper piston bowl with a smaller injector umbrella angle, and a fuel injector that opens and closes faster. The study also suggests future research to make DFI ready for commercialization, such as metal-engine tests to ensure desirable DFI performance over an engine’s complete speed/load map. Overall, this study supports the continued development and commercialization of DFI to meet upcoming emissions regulations for heavy-duty vehicles. Specifically, multicylinder engine experiments and CFD simulations should be utilized to optimize the performance and clarify the full potential of DFI.
Buurman, Noad J.Nyrenstedt, GustavMueller, Charles J.
The transportation industry is currently in a transition toward the use of zero-emission vehicles; however, reaching it will take a considerable amount of time. In the meantime, a diesel powertrain will remain the workhorse for most heavy-duty transportation. In order to reduce the engine’s environmental impact, biofuels, such as biodiesel, are used as drop-in fuels or fuel blends. The use of drop-in fuels may create challenges for the fuel system since sticky deposits can precipitate and cause injector malfunctioning or premature fuel filter plugging. It has been concluded in the past that these deposits have been caused by soft particles. In this article, soft particles created through the degradation of biodiesel and their effect on filters are studied. The article aims to analyze fuel filters and investigate the materials responsible for soft particle separation. The study includes three pre filters and three main filters that are commercially available truck filters. Different membrane types and membranes with different pore sizes were tested in order to comprehend their potential for fuel filtration. The tests were conducted using a custom-built fuel filter rig, where pressure buildup was measured online. The removal efficiency was assessed by gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma (ICP). The materials of the filters were examined by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and thermogravimetric analysis (TGA). The analysis revealed novel results from the interaction of soft particles and different filter media. The filters show similar performance for the commercial fuel filters with respect to soft particle removal and pressure buildup and thus the tendency for fuel filter plugging, where the efficiency for total calcium ion removal was around 40% for pre-filters and 60% for main filters. The material analysis shows that the particles are most likely removed mainly by the cellulose layer of the filter paper, and filters with glass fiber showed higher capacity. In addition, the membrane filters prove to show good potential for soft particle removal, with the highest removal of 72%; however, their use in practice needs to be further evaluated in actual fuel systems.
Csontos, BotondBernemyr, HannaPach, MayteHittig, Henrik
Renewable fuels have an important role to create sustainable energy systems. In this paper the focus is on biodiesel, which is produced from vegetable oils or animal fats. Today biodiesel is mostly used as a drop-in fuel, mixed into conventional diesel fuels to reduce their environmental impact. Low quality drop-in fuel can lead to deposits throughout the fuel systems of heavy duty vehicles. In a previous study fuel filters from the field were collected and analyzed with the objective to determine the main components responsible for fuel filter plugging. The identified compounds were constituents of soft particles. In the current study, the focus was on metal carboxylates since these have been found to be one of the components of the soft particles and associated with other engine malfunctions as well. Hence the measurement of metal carboxylates in the fuel is important for future studies regarding the fuel’s effect on engines. The first aim of this study was to create synthetic soft particles from biodiesel. Accelerated aging of fuels with different contaminations such as engine oil and calcium oxide were used to create the synthetic soft particles. The precipitates were collected and analyzed with different techniques such as FTIR and GC-MS, to identify the main components which were then compared with the results of the previous study. Following this, specific attention was given to calcium methyl azelate as it was shown to be found in field fuel filters. A method using GC-MS was developed to be able to estimate the amount of soft particles by measuring calcium methyl azelate. The specified method proved to be adequate for future studies to evaluate the filtration efficiency of different filter materials against soft particles.
Csontos, BotondSwarga, ShriharshaBernemyr, HannaPach, MayteHittig, Henrik
Impact of Post-Injection Parameters on Soot and Hydrocarbon Emissions in a Common-Rail Heavy-Duty Diesel Engine2020-01-03744/14/2020
In this paper, based on a direct injection (DI) diesel engine, soot and exhaust gaseous emissions were measured by a smoke meter and multi-component gas analyzer based on Fourier Transform Infrared (FTIR) spectroscopy under post-injection condition. The post-injection timing changed from 20 crank angle degree (CAD) after top dead center (ATDC) to 120 CAD ATDC, and the post-injection mass was set to either 5mg, 10mg or 15mg, to find a suitable post-injection strategy in a wide assessment range based on diesel oxidation catalyst (DOC) coupled diesel particle filter (DPF) after-treatment technology demands, considering emission reduction and after-treatment gas atmosphere investigation. The results showed that post-injection could achieve NOx emission reduction, up to 14%. Besides, post-injection led to worsening soot emissions, and more hydrocarbon (HC) emissions were detected compared to the condition without the post-injection. With the post-injection, a higher concentration of unsaturated HC emissions (such as C2H2, C2H4, and C3H6), formaldehyde (HCHO), and acetaldehyde (CH3CHO) appeared at late post-injection (after 70°CA). In the measured species, at 80°CA post-injection timing and with 10mg post-injection mass, species with low emissions (<30ppm), included CH4, C2H2, C3H6, and CH3CHO; species with medium emissions (>30ppm and <100ppm), included NO2, HCHO, C2H4, and NC8; species with large emissions (>100ppm), included NO, NOx and non-methane hydrocarbon (NMHC). Furthermore, the peak position of NMHC was the same as C3~C8 HCs and different from C2 HCs within the scope of the experiment, which indicated that, in terms of concentration, the proportion of C2 HCs was not dominant in total NMHC emissions.
Pan, WangWu, YanJing, YiZizeng, Huang
RDE-Compliant PEMS Testing of a Gasoline Euro 6d-TEMP Passenger Car at Two Ambient Temperatures with a Focus on the Cold Start Effect2020-01-03794/14/2020
European Union RDE (real driving emissions) legislation requires that new vehicles be subjected to emissions tests on public roads. Performing emissions testing outside a laboratory setting immediately raises the question of the impact of ambient conditions - especially temperature - on the results. In the spirit of RDE legislation, a wide range of ambient temperatures are permissible, with mathematical moderation (correction) of the results only permissible for ambient temperatures <0°C and >+30°C. Within the standard range of temperatures (0°C to +30°C), no correction for temperature is applied to emissions results and the applicable emissions limits have to be met. Given the well-known link between the thermal state of an engine and its emissions following cold start, ambient temperature can be of great importance in determining whether a vehicle meets emissions requirements during an RDE test. This paper reports the results of full RDE-compliant on-road emissions tests performed on a Euro 6d-TEMP passenger car with a direct injection spark ignition engine and a gasoline particle filter. Testing was performed at two temperatures, both lying within the “standard” temperature range for RDE testing: +25°C and +8°C. Regulated gaseous emissions, particle number and CO2/fuel consumption results are presented and discussed. Overall, as expected, emissions following cold start were significantly higher at the lower test temperature. Nevertheless, the long distance covered during RDE tests (~70-100 km) and their urban phases (>16 km, often ~25 km) weakens the impact of this effect. Some simple mathematical analyses of the results from various portions of the trip are presented.
Bielaczyc, PiotrMerkisz, JerzyPielecha, JacekWoodburn, Joseph
Study of Advanced Control Based on the RBF Neural Network Theory in Diesel Engine Speed Control03-13-01-000510/14/2019
Abstract Based on radial basis function (RBF) neural network (NN) theory, RBF-Proportional Integral Derivative (PID) diesel engine speed control is proposed. The algorithm has strong self-learning ability and strong adaptive ability, and is able to optimize the control parameters of the speed loop controller in real time. A series of simulations are carried out with different initial weights. Simulation results reveal that initial weights have little effect on RBF-PID control performance. A STM32 MCU-based controller is developed according to the calculation requirement. Experiments are carried out on a D6114 diesel engine generator to verify the proposed speed control algorithm. The simulation results are in agreement with the experimental results. The results show that the influence of initial weights on RBF-PID control algorithm is smaller than that on BP-PID control algorithm. When RBF-PID control algorithm is adopted, the steady speed fluctuation rate is 0.4%. When sudden load is carried out, the speed recovery time is 2.1 s and the instantaneous adjustment rate is 4.93%. When sudden unload simulation is carried out, the speed recovery time is 2.2 s and the instantaneous adjustment rate is 5.27%. Speed control performance of diesel engine has been greatly improved.
Zhao, Guo-FengLong, YunDing, Shun-LiangYang, Li-PingSong, En-ZheMa, Xiu-Zhen
Characterization of Deposits Collected from Plugged Fuel Filters2019-24-01409/9/2019
Fuel filters serve as a safety belt for modern compression ignition engines. To meet the requirements from environmental regulations these engines use the common rail injection system, which is highly susceptible to contamination from the fuel. Furthermore, the public awareness towards global warming is raising the need for renewable fuels such as biodiesel. An increased fuel variety brings a higher requirement for fuel filters as well. To better understand the process of filtration, awareness of the different possible contaminants from the field is needed. This study used several chemical characterization techniques to examine the deposits from plugged fuel filters collected from the field. The vehicle was run with a biodiesel blend available on the market. The characterization techniques included X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR) joined with attenuated total reflectance (ATR) sampling, gas chromatography-mass spectrometry (GC-MS), and lastly thermal gravimetric analyzer combined with FTIR and a GC-MS (TGA/FTIR/GC-MS). In addition the remaining ash from TGA was measured in energy-dispersive X-ray spectroscopy (EDX). Deposits were scraped from the used filter, and prepared for the different analytic methods. After cleaning the deposits with different solvents, GC-MS identified the traces of glycerol and sterols in the filter. After a transesterification reaction GC-MS could identify carboxylates corresponding to degraded biodiesel. The TGA/FTIR/GC-MS revealed the presence of polymeric compounds in the deposit. XRF did not require any previous cleaning, and was used to identify different metals present in the deposits. The mentioned deposits are characterized as soft particles, and could originate from the impurities of biodiesel, presence of engine oils, or degradation of the fuel. The presented results help to better understand the current concerns with the on-board filtration of fuels, and can help to create more robust fuel systems in the future.
Csontos, BotondBernemyr, HannaErlandsson, Anders ChristiansenForsberg, OscarPach, MayteHittig, Henrik
Numerical Study of Pore Size and Distribution Effects on Gasoline Particulate Filter Performance03-12-05-00328/22/2019
Abstract The improved brake thermal efficiency of Gasoline Direct Injection (GDI) engines is accompanied by a significant increase in Particulate Matter (PM) mass and higher Particulate Number (PN) emissions as compared to (multi)Port Fuel Injected (PFI) engines. Gasoline particulate filters (GPFs) with high filtration efficiency and low backpressure will be required to meet the future, stringent PM/PN regulations. A two-dimensional (2D) CFD study was performed to determine the effects of pore size and distribution on the interdependent performance parameters of filtration efficiency and backpressure for clean GPFs. Simulation results show an on linear change infiltration efficiency as the pore size distribution tightens and determine a recommended distribution range, controlling the quantity of small-sized pores. Pore size distributions beyond this recommended range can cause a filtration performance loss or intolerable backpressure penalty for the GPF. In addition, a recent collaborative publication from our group has demonstrated our ability to create a hierarchical porous filter, with variable pore size in each layer. Knowing that filtration efficiency and pressure drop increase as the average pore size decreases offers inspiration for a novel wall design with small pores comprising the top 40% of the wall layers and larger pores on bottom 60%. The model predicts that such a wall would result in an 8% increase in filtration efficiency.
Yang, PengzeStrzelec, Andrea
Low- to High-Temperature Reaction Transition in a Small-Bore Optical Gasoline Compression Ignition (GCI) Engine03-12-05-00318/19/2019
Abstract This study shows the development of low-temperature and high-temperature reactions in a gasoline-fuelled compression ignition (GCI) engine realizing partially premixed combustion for high efficiency and low emissions. The focus is how the ignition occurs during the low- to high-temperature reaction transition and how it varies due to single- and double-injection strategies. In an optically accessible, single-cylinder small-bore diesel engine equipped with a common-rail fuel injection system, planar laser-induced fluorescence (PLIF) imaging of formaldehyde (HCHO-PLIF), hydroxyl (OH-PLIF), and fuel (fuel-PLIF) has been performed. This was complemented with high-speed imaging of combustion luminosity and chemiluminescence imaging of cool flame and OH*. The diagnostics were performed for two different fuels including conventional diesel as a reference case and then a kerosene-based jet fuel which is a low-ignition quality fuel with cetane number of 30, firstly with single near top dead center (TDC) injection and then a double-injection strategy implementing very early injection and late injection in the same engine. For diesel combustion, it is shown that the cool-flame and HCHO signals appear from the jet axis before spreading downstream towards the bowl wall. The OH radicals present in the high-temperature reaction zones also show a similar development pattern with distinctive reaction zones forming from the jet axis and then near the bowl wall for each nozzle hole. When the reactions occur near the bowl wall, the HCHO and OH radicals coexist. Later, the high-reaction zones merge with each other due to jet-wall and jet-jet interactions. In comparison, the single-injection GCI combustion shows HCHO signals appearing from the bowl-wall region due to extended ignition delay. The OH radicals develop out of this HCHO region and show a more sequential development pattern than diesel combustion. The single-injection GCI also involves multiple ignition kernels that progressively merge to form larger reaction zones. The double-injection GCI combustion has higher charge premixing than the other cases, and due to very early first injection, the mixture homogeneity is also much higher. This is evidenced by a higher consumption rate of HCHO and faster development of OH across the entire reaction zones, indicating faster low- to high-temperature reaction transition. These fundamental findings explain why GCI combustion generates less soot and NO than diesel combustion as well as how double-injection GCI combustion achieves better low-load stability than the single-injection.
Goyal, HarshZhang, YilongKook, SanghoonKim, Kenneth S.Kweon, Chol-Bum
Development and Experimental Validation of a Control Oriented Model of a Catalytic DPF2019-01-09854/2/2019
1 The wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to meet the particulate emissions regulations for automotive engines. Today’s technology shows the best balance between filtration efficiency and back-pressure in the engine exhaust pipe. During the accumulation phase the pressure drop across the filter increases, thus requiring periodic regeneration of the DPF through after and post fuel injection strategies. This paper deals with the development of a control oriented model of a catalytic silicon carbide (SiC) wall flow DPFs with CuFe2O4 loading for automotive Diesel engines. The model is intended to be used for the real-time management of the regeneration process, depending on back-pressure and thermal state. In order to ensure suitable computational demand and to realize emissions control and fuel economy objectives, the 0-D model has been developed with the aim of investigating the essential behavior of the system, such as the chemical kinetic of filtered soot oxidation, the thermal and backpressure dynamics along accumulation and regeneration processes. Parameters identification and model validation have been performed vs. experimental data measured on the engine test bench at the exhaust of a EURO 5 light-duty Diesel engine, in different operating conditions. During the accumulation process, engine speed, load and rail pressure are controlled to ensure several levels of trapped soot; on the other hand, the injections pattern, which directly affects the DPF inlet temperature, is handled during regeneration tests. The results show that the model simulates the thermal dynamics and the pressure drop across the filter with good accuracy.
D'Aniello, FedericaRossomando, BrunoArsie, IvanPianese, Cesare
Experimental and Computational Study of DOC on CSF for Heavy Duty Diesel Applications2019-01-05864/2/2019
For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities in one component, thereby enabling volume reduction. DOC on CSF maintains the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), and the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and a DOC + CSF system, to understand the performance benefits and challenges. All the components were optimized individually for their respective functions. The DOC on CSF was optimized for NO oxidation and passive soot oxidation performance. Experimental data and simulations were used to understand the underlying mechanisms in the DOC on CSF technology. Steady state HC oxidation under active regeneration conditions showed a benefit for DOC on CSF compared to the DOC + DPF system. The soot oxidation characteristics of the DOC on CSF were evaluated in comparison to a DPF or CSF downstream of a DOC under passive and active soot oxidation conditions. In addition, the contribution of NO2 generated within the filter on the soot oxidation was assessed. The passive soot oxidation characteristics of a DOC on CSF were found to be similar, or better, compared to DOC + DPF and DOC + CSF under certain conditions. The active regeneration efficiency was lower for the DOC on CSF due to the gradual increase in temperature along the length of the part during fuel injection. This work demonstrates the differences between the DOC on CSF and DOC + bare/coated DPF systems, thus enabling a better understanding of the performance of DOC on CSF to current applications.
Sethuraman, SharanSitamraju, SiddarthLopez-De Jesus, Yaritza MMarkatou, Penelope
A Dynamic Test Bench for the Assessment of Common Rail Fuel Injection Systems Impact on CO 2 Emissions over the WLTP Cycle2019-01-02924/2/2019
The internal combustion engine technological development is today driven by the pollutants and carbon dioxide (CO2) emission reduction targets imposed by law. The request of lowering CO2 emission reflected in a push towards the improvement of engine efficiency, without sacrificing performances and drivability. The latest generations of Diesel engines for passenger cars are characterized by increasing injection pressure levels (250 MPa for the current production). Enhancing the injection pressure has the drawback of increasing the energy needed to pressurize the fuel and thus the high-pressure fuel pump energy request. A small but not negligible quantity of fuel has to be burned in order to provide this energy, generating a contribution in CO2 emission. In this frame, the injector back-flow represents a significant energy loss for the fuel injection system and for the whole engine. The energetic analysis of the overall fuel injection system of a modern passenger car is therefore interesting. In this research an experimental test bench was developed in order to energetically assess the behavior of a common-rail fuel injection system over the Worldwide harmonized Light vehicles Test Procedure (WLTP) driving cycle. The hydraulic and mechanical energy related to the fuel pump were determined, along with the corresponding CO2 emission. With the proposed test procedure is possible to split the energetic cost into the contributions from injected fuel and back-flow, allowing a comprehensive energetic assessment. Two different configurations of the fuel injection system were tested, differing in the fuel injector type. A standard, latest generation low-leakage injector model was tested and compared to a zero-leakage injector, featuring a particular architecture that should ensure very low back-flow rates. The results showed that the fuel injection system of a passenger car engine in the power range 55 - 65 kW/l absorbs 142.8 kJ of mechanical energy over the WLTP cycle, being responsible of 1.18 g/km of CO2 emission (1.3% of the total emission). The low-leakage injectors mounted on the same fuel injection system showed a 24% energy reduction and 0.29 g/km saving of CO2. In the analyzed setup, the low back-flow benefits are partially balanced by a pump volumetric efficiency reduction due to the lower operating flow-rate.
Cavicchi, AndreaPostrioti, LucioPesce, Francesco Concetto
Diffuse Back-Illuminated Extinction Imaging of Soot: Effects of Beam Steering and Flame Luminosity2019-01-00111/15/2019
This study presents diagnostic development of diffuse back-illuminated extinction imaging of soot. The method provides high temporal and spatial resolution of the line-of-sight optical density of soot (KL) in compression-ignited fuel sprays relevant to automotive applications. The method is subjected to two major sources of error, beam steering effects and broadband flame luminosity effects. These were investigated in detail in a direct injection combustion chamber with diesel fuel, under high and low sooting conditions. A new method for correcting flame luminosity effects is presented and involves measuring the flame luminosity using a separate high-speed camera via a beam splitter. The new method and existing methods are applied and the resulting flame luminosity correction errors are compared. The new method yields 50% lower errors than the most promising method (optical flow method). The impact on KL was investigated, showing that the KL uncertainty when using the optical flow method is unbounded for KL values above 2.7, while the new method has an uncertainty of 0.5 for the maximum KL value of 3.8. The new method yields overall lower uncertainties and is more suited to measuring KL in optical thick conditions. Large refractive index gradients in the path of the incident light cause false attenuation, resulting in ambiguity of the measured KL, referred to as beam steering. A detailed investigation of the beam steering effects caused by the non-uniformities in the diffused light source was performed. A beam steering model was made and qualitatively validated from experiments. The results from the beam steering model showed the importance of having a large collection angle, in order to average out small-scale non-uniformities in the light source. The model also showed that large-scale non-uniformities in the light source could affect the measurement even if the collection angle is large.
Bjørgen, Karl Oskar PiresEmberson, David RobertLovas, Terese
Comparison of Conventional Intake Port and Swirl Intake Port on Mixture Formation in a GDI Engine - A CFD Analysis2019-01-00101/15/2019
Gasoline direct injection (GDI) engines have picked up prominence in the current circumstances in light of lower fuel consumption and exhaust emissions. Mixture formation in these engines plays a critical role which affects the combustion, performance and emission characteristics. To get better mixture formation, various factors ought to be considered, of which intake port design is one of the factors of considerable importance. Therefore, in this study, a comparison of mixture formation, performance and emission characteristics has been analyzed in a GDI engine with conventional intake port and swirl intake port. The analysis is carried out on a four-stroke wall-guided GDI engine using the computational fluid dynamics (CFD) with the help of the CONVERGE. The validation of spray breakup model is carried out to the extent possible using the experimental results available in the literature. The analysis is carried out at four overall equivalence ratios at an engine speed of 2000 rpm., and a fuel injection pressure of 100 bar using a six-hole injector. From the results, it is found that better mixture stratification, higher indicated mean effective pressure (IMEP), and lower emissions are obtained for a GDI engine with the conventional intake ports at overall equivalence ratios (ER) of 0.5 and 0.6, whereas they are better in the engine with swirl intake ports at the overall ERs of 0.7 and 0.8.
Karaya, YashasAddepalli, Srinivasa KrishnaMallikarjuna, J M
Modeling Diesel Spray, Combustion and Emission with GTEA Numerical Code2019-01-00041/15/2019
A detailed chemistry-based CFD model (GTEA, General Transport Equation Analysis) is developed to simulate the diesel spray, combustion and emission process. The numerical model incorporates an improved droplet tracking model, the Hybrid breakup model that consider the influence of turbulence inside the nozzle, the reaction mechanism of n-decane coupled with a reduced NOx mechanism, a phenomenological soot model, a modified dynamic mesh model, a spray/wall impingement model, and other improved sub models in the GTEA codes. The model is first applied to predict the diesel spray process. The computational results demonstrate that the model is capable of predicting satisfactory fuel spray process, and the improved agreement is attributed to the ability of the new Hybrid breakup model to account for the effects of turbulence inside the nozzle, which enhance the spray process. The model is also applied to investigate the ignition delay and flame lift-off length under different ambient conditions. The overall trend of ignition delay and lift-off length with the variation in different conditions is well reproduced by the model. It is found that the ignition delay and lift-off length are a function of ambient density, ambient temperature and oxygen concentration, respectively. This part of study also showed that the longest ignition delay time has the longest lift-off length. Finally, the model is employed to simulate the combustion and emission characteristics of a low-temperature combustion (LTC) engine. Good levels of agreement in cylinder pressures under different EGR conditions are obtained. Predictions of soot and NOx emission are also performed. Although the predicted results are not fully satisfactory, the general trends are still well captured by the simulation.
Qi, WenliangMing, PingjianJilani, AishaPeng, Ye
Fast NGC: A New On-Line Technique for Fuel Flow Measurement2019-01-00621/15/2019
Knowledge of fuel mass injected in an individual cycle is important for engine performance and modelling. Currently direct measurements of fuel flow to individual cylinders of an engine are not possible on-engine or in real-time due to a lack of available appropriate measurement techniques. The objective of this work was to undertake real-time Coriolis fuel flow measurement using GDI injectors on a rig observing fuel mass flow rate within individual fuel injections. This paper evaluates the potential of this technology - combining Coriolis Flow Meters (CFMs) with Prism signal processing together known as Fast Next Generation Coriolis (Fast NGC), and serves as a basis for future transitions on-engine applications. A rig-based feasibility study has been undertaken injecting gasoline through a GDI injector at 150 bar in both single shot mode and at a simulated engine speeds of 1788 and 2978 rpm. The results show that these injections can, in principle, be observed. In addition a number of features of the Fast NGC system unique to gasoline are discussed, and the repeatability of the technique is preliminarily assessed. The study concludes that the Fast NGC system has the potential to measure individual injector flow rates on-engine in real-time.
Leach, FelixDavy, MartinHenry, ManusMalladi, Maruthi RochishnuTombs, MichaelZhou, FeibiaoGold, MartinPearson, Richard
Optical Investigation on the Combustion Process Differences between Double-Pilot and Closely-Coupled Triple-Pilot Injection Strategies in a LD Diesel Engine2019-01-00221/15/2019
The combustion processes of three injection strategies in a light-duty (LD) diesel engine at a medium load point are captured with a high speed video camera. A double-pilot/main/single-post injection strategy representative of a LD Euro 6 calibration is considered as the reference. There is a modest temporal spacing (dwell) after the first pilot (P1) and second pilot (P2). A second strategy, “A,” adds a third pilot (P3). The dwell after both P2 and P3 are several times shorter than in the reference strategy. A third strategy, “B,” further reduces all dwells. Each injection has its own associated local peak in the heat release rate (HRR) following some ignition delay. Between these peaks lie local minima, or dips. In all three cases, the fuel from P1 combusts as a propagating premixed flame. For all strategies, the ignition of P2 primarily occurs at its interface with the existing combustion regions. Extinguishing of the prevailing combustion by the fuel jets of later injections is noted in all strategies. This phenomenon is confirmed by comparing the timing of each fuel injection with the dips in the HRR and spatial luminescence over time. These dips after each injection are larger than would be expected by the cooling effect of the injected fuel alone. Furthermore, not all dips in the HRR are the result of this extinguishing, and it would not have been possible to determine if the dips are due to this extinguishing or a simple exhaustion of available fuel without this optical investigation. Even if the precise hydraulic injection timing can be known, knowledge of the spatial relationship of the injected fuel and prevailing combustion is necessary.
Denny, MichaelMatamis, AlexiosWang, ZhenkanPersson, HåkanTunestal, PerRichter, MattiasAndersson, Öivind
Large-Eddy Simulation on the Effects of Fuel Injection Pressure on the Gasoline Spray Characteristics2019-01-00601/15/2019
Increasing the injection pressure in gasoline direct injection engines has a substantial potential to reduce emissions while maintaining a high efficiency in spark ignition engines. Present gasoline injectors are operating in the range of 20 MPa to 25 MPa. Now there is an interest in higher fuel injection pressures, for instance, around 40 MPa, 60 MPa and even higher pressures, because of its potential for further emission reduction and fuel efficiency improvements. In order to fully utilize the high-pressure fuel injection technology, a fundamental understanding of gasoline spray characteristics is vital to gain insight into spray behavior under such high injection pressures. The understanding achieved may also be beneficial to improve further model development and facilitate the integration of such advanced injection systems into future gasoline engines. In the present study, a gasoline fuel spray has been investigated over a range of fuel injection pressures from 40 to 150 MPa through a numerical simulation study. The numerical calculations have been performed in a constant volume chamber under non-vaporizing conditions to best match the experimental setup. The numerical model utilized a large-eddy simulation (LES) approach for the gas flow and a standard Lagrangian spray model for the liquid phase. The spray atomization has been modeled using the Kelvin Helmholtz - Rayleigh Taylor (KH-RT) atomization model with a droplet size distribution from the injector assumed to follow a Rosin-Rammler distribution function. Simulation results for the spray liquid penetration length are validated with experimental findings under different fuel injection pressures. Afterwards, an arithmetic mean droplet diameter (D10) and a Sauter mean droplet diameter (D32) as a function of pressure are compared against the measured droplet diameters. Simulated drop size distributions are presented and compared with measured droplet sizes. The results indicate that a high fuel injection pressure increases the liquid penetration length and significantly reduces droplet sizes. The results also exhibit that the SMD decreases from 13.4 μm to 7.5 μm, when injection pressure changes from 40 MPa to 150 MPa and that probability of finding the 5-9 μm droplet diameter decreases from 72% to 40% for the injection pressure drops from 150 MPa to 40 MPa.
Wadekar, SandipYamaguchi, AkichikaOevermann, Michael
Water Injection Benefits in a 3-Cylinder Downsized SI-Engine2019-01-00341/15/2019
With progressing electrification of automotive powertrains and demands to meet increasingly stringent emission regulations, a combination of an electric motor and downsized turbocharged spark-ignited engine has been recognized as a viable solution. The SI engine must be optimized, and preferentially downsized, to reduce tailpipe CO2 and other emissions. However, drives to increase BMEP (Brake Mean Effective Pressure) and compression ratio/thermal efficiency increase propensities of knocking (auto-ignition of residual unburnt charge before the propagating flame reaches it) in downsized engines. Currently, knock is mitigated by retarding the ignition timing, but this has several limitations. Another option identified in the last decade (following trials of similar technology in aircraft combustion engines) is water injection, which suppresses knocking largely by reducing local in-cylinder mixture temperatures due to its latent heat of vaporization. Addition of adequate water can lead to stoichiometric air/fuel ratio engine operation, and hence both reduction in fuel consumption and full utilization of a three-way catalytic converter (TWC). Further information about effects of various water injection parameters is required. Thus, in this study, a 4-stroke, 1.5 liter, 3-cylinder turbocharged engine with direct fuel injection and port water injection was operated on 91, 95 and 98 RON gasoline fuel to assess effects of water injection on knock mitigation, combustion phasing, required air:fuel ratios and exhaust gas temperature control. Full- and part-load curves obtained with different fuels and water injection strategies are presented and discussed.
Khatri, JayeshDenbratt, IngemarDahlander, PetterKoopmans, Lucien
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, YuanjiangPal, PinakiZhang, YuTraver, MichaelCleary, DavidFutterer, CarstenBrenner, MattiaProbst, DanielSom, Sibendu
Simulation and Measurement of Transient Fluid Phenomena within Diesel Injection2019-01-00661/15/2019
Rail pressures of modern diesel fuel injection systems have increased significantly over recent years, greatly improving atomisation of the main fuel injection event and air utilisation of the combustion process. Continued improvement in controlling the process of introducing fuel into the cylinder has led to focussing on fluid phenomena related to transient response. High-speed microscopy has been employed to visualise the detailed fluid dynamics around the near nozzle region of an automotive diesel fuel injector, during the opening, closing and post injection events. Complementary computational fluid dynamic (CFD) simulations have been undertaken to elucidate the interaction of the liquid and gas phases during these highly transient events, including an assessment of close-coupled injections. Microscopic imaging shows the development of a plug flow in the initial stages of injection, with rapid transition into a primary breakup regime, transitioning to a finely atomised spray and subsequent vaporisation of the fuel. During closuring of the injector the spray collapses, with evidence of swirling breakup structures together with unstable ligaments of fuel breaking into large slow-moving droplets. This leads to sub-optimal combustion in the developing flame fronts established by the earlier, more fully-developed spray. The simulation results predict these observed phenomena, including injector surface wetting as a result of large slow-moving droplets and post-injection discharge of liquid fuel. This work suggests that post-injection discharges of fuel play a part in the mechanism of the initial formation, and subsequent accumulation of deposits on the exterior surface of the injector. For multiple injections, opening events are influenced by the dynamics of the previous injection closure; these phenomena have been investigated within the simulations.
Gold, MartinPearson, RichardTurner, JackSykes, DanStetsyuk, Viacheslavde Sercey, GuillaumeCrua, CyrilMurali-Girija, MithunKoukouvinis, FoivosGavaises, Manolis
Investigation of an Advanced Combustion System for Stoichiometric Diesel to Reduce Soot Emissions2019-01-00231/15/2019
Diesel engines are facing increased competition from gasoline engines in the light-duty and small non-road segments, primarily due to the high relative cost of emissions control systems for lean-burn diesel engines. Advancements in gasoline engine technology have decreased the operating cost advantage of diesels and the relatively high initial-cost disadvantage is now too large to sustain a strong business position. SwRI has focused several years of research efforts toward enabling diesel engine combustion systems to operate at stoichiometric conditions, which allows the application of a low-cost three-way catalyst emission control system which has been well developed for gasoline spark-ignited engines. One of the main barriers of this combustion concept is the result of high smoke emissions from poor fuel/air mixing. The current study focuses on improving the combustion system by investigating different fuel/air mixing strategies that enhance fuel spray - piston bowl interaction while simultaneously optimizing the fuel injection system. Computational Fluid Dynamics (CFD) simulations were carried out in conjunction with engine testing to evaluate different piston bowl designs as well as injector nozzle designs with reduced hole diameters to improve in-cylinder mixing and reduce spray over penetration. By using proposed combustion strategy, it was demonstrated that smoke emissions were reduced significantly from baseline under stoichiometric diesel operation.
Chase, AveryMiwa, JasonAbidin, ZainalCung, Khanh
Spray Characterization of Gasoline Direct Injection Sprays Under Fuel Injection Pressures up to 150 MPa with Different Nozzle Geometries2019-01-00631/15/2019
Maximum fuel injection pressures for GDI engines is expected to increase due to positive effects on emissions and engine-efficiency. Current GDI injectors have maximum operating pressures of 35 MPa, but higher injection pressures have yielded promising reductions in particle number (PN) and improved combustion stability. However, the mechanisms responsible for these effects are poorly understood, and there have been few studies on fuel sprays formed at high injection pressures. This paper summarizes experimental studies on the properties of sprays formed at high injection pressures. The results of these experiments can be used as inputs for CFD simulations and studies on combustion behavior, emissions formation, and combustion system design. The experiments were conducted using an injection rate meter and optical methods in a constant volume spray chamber. Injection rate measurements were performed to determine the injectors’ flow characteristics. Spray imaging was performed using a high-speed video camera. Several spray properties such as the liquid spray penetration, spray plume angle, and the spray breakup point were determined as functions of the fuel injection pressure and injected fuel mass by image post-processing. The impact of fuel pressure on spray droplet size was also investigated using two-component Phase Doppler Interferometry. Piezoelectric injectors for diesel engines were used with modified nozzles that produce sprays resembling those generated in gasoline engines. Experiments were performed with fuel injection pressures ranging from 20 to 150 MPa, and chamber pressures of 0.1 and 0.6 MPa. In addition, four different nozzles with three different nozzle configurations and either 6 or 10 holes were used to determine how hole geometry affects spray formation. The study’s key findings are that increasing the fuel injection pressure advances spray breakup and creates smaller droplets, improving mixture formation and accelerating evaporation. The nozzle type and the ambient pressure both significantly affect aspects of spray behavior such as spray tip development.
Yamaguchi, AkichikaKoopmans, LucienHelmantel, ArjanKarrholm, Fabian PengDahlander, Petter
An Experimental Study of the Effects of Coolant Temperature on Particle Emissions from a Dual Injection Gasoline Engine2019-01-00511/15/2019
Euro VI emission standards have set a very strict limitation on particulate matter emissions of Gasoline Direct Injection (GDI) engine. It is difficult for GDI engine to meet the Euro VI PN regulation (6×1011#/km) without a series of complicated after-treatment devices such as Gasoline Particulate Filter (GPF). Previous research shows that GDI vehicles under cold start condition account for more than 50% of both particle number and mass emissions during the entire NEDC driving cycle. Dual Injection Gasoline engine is based on the GDI engine by adding a set of port fuel injection system. The good mixing characteristics of the port fuel injection system can help to reduce the particulate matter emissions of the GDI engine during the cold start condition. In this study, a Cambustion DMS500 fast particle spectrometer was employed to characterize the effects of coolant temperature and direct injection ratio on particulate emissions from a turbocharged four-cylinder dual-injection gasoline engine. The experimental results showed that with the coolant temperature increasing the particulate matter tended to be consistent under the port fuel injection mode. The particulate matter showed significantly drop with the coolant temperature increasing both in the dual injection mode and the direct injection mode. At the same coolant temperature, with the decrease of the direct injection ratio, the particulate matter showed notably reductions, and with the increase of coolant temperature, the magnitude of the reductions gradually declined. The experimental results provided important guidance to reduce the particulate matter via dual injection mode during the cold start condition.
Xia, ChunChen, WenhaoFang, JunhuaHuang, Zhen
Methane Direct Injection in an Optical SI Engine - Comparison between Different Combustion Modes2019-01-00831/15/2019
Natural gas, biogas, and biomethane are attractive fuels for compressed natural gas (CNG) engines because of their beneficial physical and chemical characteristics. This paper examines three combustion modes - homogeneous stoichiometric, homogeneous lean burn, and stratified combustion - in an optical single cylinder engine with a gas direct injection system operating with an injection pressure of 18 bar. The combustion process in each mode was characterized by indicated parameters, recording combustion images, and analysing combustion chemiluminescence emission spectra. Pure methane, which is the main component of CNG (up to 98%) or biomethane (> 98 %), was used as the fuel. Chemiluminescence emission spectrum analysis showed that OH* and CN* peaks appeared at their characteristic wavelengths in all three combustion modes. The peak of OH* and broadband CO2* intensities were strongly dependent on the air/fuel ratio conditions in the cylinder. Lower OH* and CO2* intensities were observed with lean air/fuel mixtures because under these conditions, more air was present, the combustion reactions were slower, and the cylinder pressure was higher. CN* was formed by the spark plasma and was detected over a particularly long period when using a dual coil ignition system. The intensities of the OH* and CN* signals correlated when using this ignition system. Combustion image analysis showed that the flame had a wrinkled boundary in stoichiometric and lean burn modes and was especially distorted in stratified mode. No yellow soot luminescence was observed during homogeneous combustion. However, the emission spectra and combustion images acquired during stratified combustion showed that soot formation occurred due to the presence of fuel-rich areas with inadequate mixing in the cylinder. The difficulty of maintaining stable fuel injection, achieving proper air/fuel mixing, and ensuring stable flame propagation in lean air/fuel mixtures increased cycle-to-cycle variations. However, the homogeneous lean burn and stratified combustion modes achieved significantly lower indicated specific fuel consumption values than stoichiometric combustion.
Melaika, MindaugasAndersson, MatsDahlander, Petter
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, GustavAlturkestani, TariqIm, HongJohansson, Bengt
Reactivity controlled compression ignition has been a proven combustion strategy for better reduction of NOx and PM emissions without compromising the fuel economy. However, the combustion strategy still need more investigation to overcome its operational stability. In this study, the influence of hot/cooled exhaust gas recirculation and premixed mass percentage and there cyclic variation of Methanol/Diesel dual fuel reactivity controlled compression ignition (RCCI) combustion was investigated in a modified 3 cylinder light duty, turbocharged, CRDI diesel engine. Methanol/Diesel RCCI combustion was achieved by premixing methanol with intake air in the intake port and injecting diesel directly into the cylinder by flexible common rail direct injection system. The intake manifold was altered to adopt port fuel injection of methanol and EGR. Experiments were conducted at 3.4 bar and 5.1 bar BMEP at 1500 rpm by varying EGR and premixed mass percentage. Overall, the results shows that 26% cooled EGR resulted in less cycle to cycle variation, better reduction in NO, and smoke emissions with improved thermal efficiency at both loads with methanol mass percentage 76% and 81% respectively. At hot EGR operation the higher cyclic variation, higher pressure rise rate and higher NOx and smoke emissions observed than cooled EGR operation. It is also observed that 5.1 bar BMEP operation exhibited a lesser cycle to cycle variation and emissions compared to 3.4 bar BMEP operation.
Duraisamy, GaneshRangasamy, MuruganNagarajan, Govindan
Water Load Determination Approach in Two Wheeler Exhaust System2018-32-007510/30/2018
Future emission norms in India (BS6) necessitates the 2 wheeler industry to work towards emission optimization measures. Engine operation at stoichiometric Air-Fuel Ratio (AFR) would result in a good performance, durability and least emissions. To keep the AFR close to stoichiometric condition, an Oxygen sensor is placed in the exhaust system, which detects if air-fuel mixture is rich (λ<1) or lean (λ>1) and provides feedback to fuel injection system for suitable fuel control. O2 sensor has a ceramic element, which needs to be heated to a working temperature for its functioning. The ceramic element would break (thermal shock) if water in liquid form comes in contact with it when the element is hot. To counter this, oxygen sensor is either fully heated only when all the water in the exhaust system is evaporated, which results in delayed closed loop control, or is capable to withstand higher amount of water in the exhaust system by for example being applied with thermal shock protection and a protective tube. It’s a challenge to control the HC emissions during first 100 seconds of engine start, as the catalyst is not functioning during this duration. Also, the system runs in open loop for first 50 seconds, as the lambda sensor is not functioning. Hence, determining the amount of water present in exhaust and having a protective layer for lambda sensor against water would enable early start of sensor functioning. The present paper explains an approach to determine the maximum water droplet size and water flow rate using a special Liquid sensor mounted in the exhaust pipe. Test cases are defined at various engine and exhaust gas temperatures to determine an appropriate set up and methodology for measurement on a 2Wheeler. The test cases are repeated on various 2wheelers available in the Indian market and influence of different exhaust configurations, mounting location of the Lambda sensor are analysed. The information of water droplet size and water flow rate are driving factors for the design and application of lambda sensor. With thermal shock protection over lambda sensor a full heater voltage can be applied to sensor even before all the water has evaporated in the exhaust system. An early sensor readiness results in a quick closed loop control of the fuel mixture thus reducing emissions.
Meena, Ranjana KumariKrusch, AndreaMeister, KonradHolzknecht, Christopher
Effect of Fuel Injection Timing on the Mixture Preparation in a Small Gasoline Direct-Injection Engine2018-32-001410/30/2018
Gasoline direct-injection (GDI) engines have evolved as a solution to meet the current demands of the automotive industry. Benefits of a GDI engine include good fuel economy, good transient response, and low cold start emissions. However, they suffer from problems, like combustion instability, misfire, and impingement of fuel on in-cylinder surfaces. Therefore, to highlight the influence of fuel injection timing on in-cylinder flow, turbulence, mixture distribution and wall impingement, a computational study is conducted on a small-bore GDI engine. Results showed that air motion inside the engine cylinder is influenced by direct-injection of fuel, with considerable variation in turbulent kinetic energy at the time of injection. Due to charge cooling effect, mixture density and trapped mass were increased by about 10.8% and 9.5%, respectively. A significant drop in mean in-cylinder temperature (about 100 °C) was observed with direct-injection of fuel as compared to the case without injection, with further variation based on injection timing. Fuel distribution near the spark plug and fuel impingement on in-cylinder surfaces are carefully evaluated. An early injection at 80 crank angle degree after top dead center of intake provided the best fuel distribution and minimum wall impingement. At the time of spark, in-cylinder turbulence was also found to be higher for this injection timing. Experimental results also indicated relatively higher brake thermal efficiency and lower emissions with early fuel injection timings, located around the mid of intake.
Jose, JubinParsi, AnilShridhara, ShrinidhiMittal, MayankRamesh, A
Mixture Formation and Combustion Evaluation of a Motorcycle Engine Concept Equipped with One Fuel Injector for Each Intake Valve2018-32-000910/30/2018
In light of a more stringent emission legislation and in anticipation of possible future measures to further reduce the real environmental impact of motorcycles, it is necessary to develop engine concepts which are efficient and low on emissions in a wide range of operating points. This poses an important challenge on the development of high performance motorcycles engines as their focus on full load behaviour conflicts sharply with the emission and efficiency demands of the remaining engine load map. The focus of this paper is to evaluate the potential of a port fuel injection (PFI) concept consisting of one individual fuel injector for each intake valve to solve this trade-off. Previous research shows a positive effect of such a setup on mixture formation due to better targeting and atomization, reducing HC emissions and cyclic variations. It also shows improved efficiency, performance and knocking characteristics caused by an enhanced charge cooling effect through open valve injection (OVI). Although the system has been previously investigated, the necessary layout considerations and impacts of the system for a high performance motorcycle engine have not yet been addressed. In this work the mentioned PFI concept was studied using a high performance two-cylinder motorcycle engine. Engine tests were conducted for two injector sets having different static flow values. The results showed improved efficiency and lower HC emissions for higher engine loads, but no performance gain at full load. The reasons for this behaviour were closely analysed by means of CFD simulation and thermodynamic loss analysis of the combustion process. These explanations were further confirmed by additional engine tests using exhaust gas sampling with fast FID. As a final result a set of recommendations for further concept improvement is proposed.
Gaitan, PedroSchwarz, FrankEibl, Rüdiger
CFD Analysis of a Port Fuel Injection IC Engine to Study Air-Fuel Mixture Preparation and Its Impact on Hydrocarbon Emission and Mixture Homogeneity in Combustion Chamber2018-32-000510/30/2018
At part load conditions, effective utilization of fuel is critical for drivability of an IC engine driven automobile, with minimum emissions and fuel consumption. It becomes cardinal to study the mixture preparation in engines to understand the injection strategy that helps in achieving the prime objectives of lower emission and reliable operation. To add to the complexity of the problem being studied, the injection phenomenon is rapid, turbulent, multi-phase, two-way coupled (where the continuous phase affects the droplets and vice versa) and involves turbulence length scales and time scales, few orders of magnitude lower compared to the characteristic length in the turbulence integral scale. A methodology is developed in Star-CD and ES-ICE to simulate the mixture preparation in Port Fuel Injection (PFI) engines. High quality mixture preparation which is essential for combustion stability and lower emissions is aimed at part load conditions which constitute the majority of driving cycle. This methodology is helpful to understand and solve the injection timing development issues and in improving the combustion stability and lowering the emissions. The fuel injection parameters have been studied in detail both experimentally and numerically in a specialized spray chamber. The fuel injection parameters are correlated to the source of injection to obtain similar fit of droplet distribution profile obtained experimentally. The parameters like - injection timing, injection location and injection pressure can be efficiently optimized through this methodology for efficient mixture formation. Extensive studies have been done on different injection timing in order to reduce the wall film thickness and fuel short circuit losses and to increase the overall evaporation rate of fuel droplets by increasing the residence time. Two injection timing strategies namely - open valve injection and closed valve injection have been analyzed to understand the effect of fuel short circuit losses and its impact on HC (hydro-carbon) emissions. It is observed that, open valve injection has lower short circuit losses compared to closed valve injection, which is experimentally verified and thus has a great significance in reducing the HC emissions. However, open valve injection comparatively affects the in-cylinder charge homogeneity and standard deviation of equivalence ratio. This paper also discusses on the strategies that have been undertaken to achieve best-in-cylinder homogeneity with an adverse effect on increased fuel film thickness on the port walls. Efforts are made to optimize the injection timing and location for best mixture formation in production automotive vehicles and in extending the methodology for the corresponding emission prediction. Being a computationally intensive problem with an additional complexity of moving mesh, opens an opportunity for parallel performance study. Parallel performance study shows that the methodology proposed above uses a Message Passing Interface (MPI) and shows a good scale up for 2-16 cores, above which it saturates. Multi-cycle analysis is carried out to understand the variation in Air-Fuel ratio homogeneity and Coefficient of variation of Indicated Mean Effective Pressure (IMEP) which provides a fundamental vista on the transient behavior of the spray dynamics.
G B, ArivazhaganGarg, Manish
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, MashuYamada, Yoshikazu
Study on Realization of Dual Combustion Cycle by Lean Mixture and Direct Fuel Injection2018-32-001110/30/2018
The purpose of this study is to realize dual-combustion cycle for gasoline engines. For the purpose, lean combustion and direct fuel injection were applied to small diesel engine. The lean gasoline-air mixture was provided and was ignited by small amount of pilot diesel fuel injection (constant volume combustion). Then, diesel fuel was injected by main injection and was burned with the remained oxygen after the lean combustion (diffusion combustion). The equivalence ratio 0.3, 0.4 and 0.5 of mixture were used to avoid the spontaneous compression auto-ignition. The total equivalence ratio with supplied gasoline and diesel fuel was adjusted to 1.0. The base pilot injection timing was selected as the ignition of pre-mixture took place at T.D.C. and pilot injection timings were changed 2 degree before and behind of base timing. The main fuel injection timings were 50, 75 and 100% of the duration between pilot injection timing and T.D.C. The test engine was an air cooled four-stroke single cylinder direct injection diesel engine. The compression ratio was 17.3, and engine performance and exhaust gas emissions were measured at engine speed of 2000 rpm. The pressure of constant volume combustion was rapidly raised for equivalence ratio of 0.5 and was low for equivalence ratio of 0.3, therefore equivalence ratio of 0.4 was preferable in this study. When the constant volume premixed combustion occurred near T.D.C. and main fuel injection was injected after T.D.C., the constant pressure diffusion combustion appeared and high thermal efficacy was obtained. The high THC concentration was detected, because the entire remained air after pre-mixed combustion did not contribute to diffusion combustion, however the smoke concentration was hardly detected. The NOx concentration increased for early pilot and main injection timings due to rapid premixed combustion. However, the pilot and main fuel injection timings hardly influenced engine performance.
Yamada, HikaruYoshida, Koji
Improvement of Thermal Efficiency in a Diesel Engine with High-Pressure Split Main Injection2018-01-17919/10/2018
This study aims to utilize high-pressure split-main injection for improving the thermal efficiency of diesel engines. A series of experiments was conducted using a single-cylinder diesel engine under conditions of an engine speed of 2,250 rpm and a gross indicated mean effective pressure of 1.43 MPa. The injection pressure was varied in the range of 160–270 MPa. Split-main injection was applied to reduce cooling loss under the condition of high injection pressure, and the split ratio and the number of injection stages were varied. The dwell of the split main injection was set to near-zero in order to minimize the elongation of the total injection duration. As a result, thermal efficiency was improved owing to the combined increase in injection pressure, advanced injection timing, and split-main injection. According to the analysis of heat balance, a larger amount of the second part of the main injection decreased the cooling loss and increased the exhaust loss. Computational fluid dynamics calculations were performed to reveal the causes of the lower cooling loss; however, the results could not capture the experimental trend when using an ordinary spray cone angle. While using a wider spray angle for the second part of main injection, the calculated trend improved. The total cooling loss depends on the balance between the cooling losses by the first and second main sprays.
Horibe, NaotoBao, ZhichaoTaguchi, TomokiEgoshi, KentaKawanabe, HiroshiIshiyama, Takuji
Dual Fuel Injection (DI + PFI) for Knock and EGR Dilution Limit Extension in a Boosted SI Engine2018-01-17359/10/2018
Combined direct and port fuel injection (i.e., dual injection) in spark ignition engines is of increasing interest due to the advantages for fuel flexibility and the individual merits of each system for improving engine performance and reducing engine-out emissions. Greater understanding of the impact of dual injection will enable deriving the maximum benefit from the two injection systems. This study investigates the effects of dual injection on combustion, especially knock propensity and tolerance to exhaust gas recirculation (EGR) dilution at different levels of EGR. A baseline for comparison with dual injection results was made using direct injection fueling only. A splash blended E20 fuel was used for the direct injection only tests. For the dual injection tests, gasoline, representing 80% by volume of the total fuel, was injected using the direct injector, and ethanol, representing 20% by volume of the total fuel, was injected using the port fuel injector. EGR mass fraction was varied from 0% to 21%, under boosted intake air pressure of 1.25 bar for both injection strategies. The results showed dual injection was beneficial to shorten the burn duration and improve combustion stability. Dual injection was more sensitive to knock than direct injection primarily due to increased unburned gas temperature. The overall thermal efficiency for the two injection types was comparable. The particulate matter emissions from dual injection showed slightly lower values, and the gaseous emissions showed lower total hydrocarbons and similar nitrogen oxides compared with only using direct injection of E20.
Han, TaehoonLavoie, GeorgeWooldridge, MargaretBoehman, André
The Effect of Pressure, Temperature and Additives on Droplet Ignition of Lubricant Oil and Its Surrogate2018-01-16739/10/2018
Numerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the auto-ignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the lubricant oil film on the cylinder walls, causing fuel splashing to pull oil off the walls, forming droplets. The dilution of the oil by the fuel also changes lubricant oil droplet properties. Therefore, it is important to understand lubricating oils, with and without fuel dilution, as a possible ignition source in pre-ignition and super knock events. In this work, a constant volume (4 L) combustion chamber (CVCC) that allows the introduction of a single droplet of lubricating oil has been built. It is capable of operation at elevated pressures and temperatures. To simulate the droplet-induced pre-ignition event, a droplet injection system was incorporated into the vessel. The oil droplet was suspended on the junction of a thermocouple where the instantaneous internal droplet temperature was measured throughout the oil droplet lifetime. The experiments were carried out in an air atmosphere heated to 300 °C. The ambient pressure was varied from 2-15 bar. In the present work, the effect of pressure on droplet ignition of conventional engine oil (SAE 15 W-40), its surrogate hexadecane (C16H34), and hexadecane mixed with lubricant oil additives has been investigated to understand the fundamental physics of droplet-induced ignition. The objective of this study is to determine the probability that an oil droplet will ignite at temperatures and pressures relevant to modern turbocharged GDI engines.
Maharjan, SumitQahtani, YasserRoberts, WilliamElbaz, Ayman
Effect of Mixture Formation and Injection Strategies on Stochastic Pre-Ignition2018-01-16789/10/2018
Stochastic pre-ignition remains one of the major barriers limiting further engine downsizing and down-speeding; two widely used strategies for improving the efficiency of spark-ignited engines. One of the most cited mechanisms thought to be responsible for pre-ignition is the ignition of a rogue droplet composed of lubricant oil and fuel. This originates during mixture formation from interactions between the fuel spray and oil on the cylinder liner. In the present study, this hypothesis is further examined using a single cylinder supercharged engine which employs a range of air-fuel mixture formation strategies. These strategies include port-fuel injection (PFI) along with side and central direct injection (DI) of an E5 gasoline (RON 97.5) using single and multiple injection events. Computational fluid dynamic (CFD) calculations are then used to explain the observed trends. Overall, this study reinforces that interactions between the fuel spray and oil on the cylinder liner can be an important contributor towards stochastic pre-ignition. The occurrence of pre-ignition, as shown by CFD calculations, is successful after completion of two stages. The first stage involves the formation of precursors from interactions between the fuel spray and oil on the cylinder liner. This is shown to be dependent upon the mass of the fuel impinging on the cylinder liner. The second stage involves the ignition of the precursor, which is shown to be dependent upon the temperature of the air-fuel mixture near top dead center.
Singh, EshanMubarak Ali, Mohammed JaasimIchim, AdrianMorganti, KaiDibble, Robert
Assessment of the New Features of a Prototype High-Pressure “Hollow Cone Spray” Diesel Injector by Means of Engine Performance Characterization and Spray Visualization2018-01-16979/10/2018
The application of more efficient compression ignition combustion concepts requires advancement in terms of fuel injection technologies. The injector nozzle is the most critical component of the whole injection system for its impact on the combustion process. It is characterized by the number of holes, diameter, internal shape, and opening angle. The reduction of the nozzle hole diameter seems the simplest way to promote the atomization process but the number of holes must be increased to keep constant the injected fuel mass. This logic has been applied to the development of a new generation of injectors. First, the tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate. The vertical movement of the needle generates an annulus area for the fuel delivery on 360 degrees, so controlling the atomization as a function of the vertical plate position. Second, on the base of the obtained results, the authors have introduced a new nozzle configuration. This is characterized by a hybrid fuel injection concept, composed of five preferential fuel jets, generated via a specific design of the internal nozzle geometry, and an additional circle-shaped fuel injection, with the aim of using the air between the jets. The experimental investigation has been performed on a single-cylinder metal engine to assess the new concept injector performance by varying the main control parameters (electrical command, nozzle tip protrusion, test point, etc.). Then a deeper investigation of the injector characteristics in different conditions has been performed in an optical single-cylinder diesel engine via digital imaging to catch information on its functioning. A better control of the fuel delivery has been observed compared to the previous injector configuration. Images of the injection process showed that the fuel assumed a good symmetric shape at the nozzle exit for both the jets and the circular plume. A better utilization of the available volume is granted by the new concept injector. The improved mixing quality has shown advantages in terms of combustion efficiency and engine-out emissions.
Sequino, LuigiBelgiorno, GiacomoDi Blasio, GabrieleMancaruso, EzioBeatrice, CarloVaglieco, Bianca Maria
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, YueqiMubarak Ali, Mohammed JaasimHuang, ZhenIm, Hong
Heavy-Duty Diesel Engine Spray Combustion Processes: Experiments and Numerical Simulations2018-01-16899/10/2018
A contemporary approach for improving and developing the understanding of heavy-duty Diesel engine combustion processes is to use a concerted effort between experiments at well-characterized boundary conditions and detailed, high-fidelity models. In this paper, combustion processes of n-dodecane fuel sprays under heavy-duty Diesel engine conditions are investigated using this approach. Reacting fuel sprays are studied in a constant-volume pre-burn vessel at an ambient temperature of 900 K with three reference cases having specific combinations of injection pressure, ambient density and ambient oxygen concentration (80, 150 & 160 MPa - 22.8 & 40 kg/m3-15 & 20.5% O2). In addition to a free jet, two different walls were placed inside the combustion vessel to study flame-wall interaction. Experimentally, low- and high-temperature reaction product distributions are imaged simultaneously using single-shot planar laser-induced fluorescence (PLIF) of formaldehyde and high-speed line-of-sight imaging of the chemically-excited hydroxyl radical (OH*). Interference of soot incandescence in experimental OH* recordings is assessed to improve interpretation of the results. Interference by poly-cyclic aromatic hydrocarbon (PAH) LIF and soot radiation is mostly evaded by evaluating flame structures shortly after ignition for one of the studied cases, but presumably included in others. Simulations were performed using a recently developed computational fluid dynamics (CFD) methodology with detailed chemistry and turbulence-chemistry interaction. Apart from the capability to model flame structures and combustion indicators based on optical diagnostics, heat-release rate trends are predicted accurately at varying boundary conditions. Significant variation in the distribution of low-temperature combustion products under heavy-duty operating conditions are explained using both CFD simulations and a one-dimensional jet model.
Maes, NoudDam, NicoSomers, BartLucchini, TommasoD'Errico, GianlucaHardy, Gilles
Modeling the Pilot Injection and the Ignition Process of a Dual Fuel Injector with Experimental Data from a Combustion Chamber Using Detailed Reaction Kinetics2018-01-17249/10/2018
The introduction of the so called Emission Controlled Areas within the IMO Tier III legislation forces manufacturers of maritime propulsion systems to adherence to stringent emission thresholds. Dual fuel combustion, which is characterized by the injection of a small amount of fuel oil to ignite a premixed natural gas air mixture, constitutes an option to meet this target. At high diesel substitution rates and very short pilot injection events, the injector is operated in the ballistic regime. This influences spray penetration, mixture formation and ignition behavior. In the present work, a seven-hole dual fuel injector was measured in a combustion chamber to provide data for the generation of a CFD model using the commercial code AVL FIRE®. The liquid and the vapor phase of the fuel spray were quantified by Mie-scattering and Schlieren-imaging technique for different chamber conditions. Based on the measured spray characteristics, a methodology was developed to imprint a velocity profile to the initial droplets in the CFD model, to depict the spray penetration for small injection durations. To characterize the ignition process and the flame propagation, measurements of the OH* emission and the natural luminosity of the flame were carried out. A detailed reaction mechanism, which is able to predict both diesel and dual fuel combustion, was integrated in the CFD model. The ignition delay was fitted to the experimental data by adapting the reaction mechanism for different chamber temperatures. The influence of the presence of natural gas on the ignition behavior was validated using data from a rapid compression machine. Even for low temperatures and high pressures, similar to the start of injection under engine operating conditions, a good correlation could be achieved. The developed knowledge will be transferred to an engine model to investigate the limits of dual fuel combustion processes.
Frühhaber, JensPeter, AndreasSchuh, SebastianLauer, ThomasWensing, MichaelWinter, FranzPriesching, PeterPachler, Klaus
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