Browse Topic: Variable compression ratio engines

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Test 123SAE-PP-005182/8/2022
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Basile, Julia, Mutagaana, Festo
Continuously Variable Displacement Drive for Engines Part 2, Design, Analysis, and TestSAE-PP-005162/8/2022
A new type of drive system has been designed, analyzed, patented, prototyped, and tested. The drive’s unique capabilities include the ability to vary the bottom dead center position to reduce the stroke, and simultaneously vary the top dead center position to achieve the desired compression ratio with one simple, low friction mechanism. The purpose of the concept is to reduce losses associated with operation at partial load as most engines spend a preponderance of their operating life at partial load. This paper covers the design and analysis, prototyping, and testing of the unit as an air compressor. Engine simulation of the unit configured as a gasoline engine showed a ~30% improvement in fuel economy on a 10-mode weighted cycle and is covered in SAE 2021-01-0442, “Continuously Variable Displacement Drive for Engines Part 1, Performance Simulation.”
Basile, Julia
Knock: A Century of Research03-15-01-00047/28/2021
Knock is one of the main limitations on increasing spark-ignition (SI) engine efficiency. This has been known for at least 100 years, and it is still the case today. Knock occurs when conditions ahead of the flame front in an SI engine result in one or more autoignition events in the end gas. The autoignition reaction rate is typically much higher than that of the flame-front propagation. This may lead to the creation of pressure waves in the combustion chamber and, hence, an undesirable noise that gives knock its name. The resulting increased mechanical and thermal loading on engine components may eventually lead to engine failure. Reducing the compression ratio lowers end-gas temperatures and pressures, reducing end-gas reactivity and, hence, mitigating knock. However, this has a detrimental effect on engine efficiency. Automotive companies must significantly reduce their fleet carbon dioxide (CO2) values in the coming years to meet targets resulting from the 2015 Paris Agreement. One path towards meeting these is through partial or full electrification of the powertrain. However, the vast majority of automobiles in the near future will still feature a gasoline-fueled SI engine; hence, improvements in combustion engine efficiency remain fundamental. As knock has been a key limitation for so long, there is a huge amount of literature on the subject. A number of reviews on knock have already been published, including in recent years. These generally concentrate on current understanding and status. The present work, in contrast, aims to track the progress of research on knock from the 1920s right through to the present day. It is hoped that this can be a useful reference for new and existing researchers of the subject and give further weight to occasionally neglected historical activity, which can still provide important insights today.
Corrigan, Daire James, Fontanesi, Stefano
Review of Additive Manufacturing for Internal Combustion Engine Components03-13-05-00399/9/2020
With highway vehicles using over 20% of the total energy consumption in the United States, making strides in improving their fuel economy will positively influence the nation’s environmental impact. One methodology to accomplish this outcome is by reducing vehicle weight. In this regard, since the internal combustion (IC) engine is a major contributor to the mass of an automobile, it is an ideal area to target. Prior efforts in this area include using alternative materials (e.g., aluminum or magnesium) to decrease weight. Here, additive manufacturing (AM) is an appealing option due to its freedom from typical manufacturing constraints and the ability to produce highly optimized designs using nonconventional powertrain materials (e.g., titanium). The use of AM has the potential to increase reliability, improve performance, decrease production cost, and possibly minimize the number of parts. Since metal-based AM is a relatively new area of manufacturing for IC engines, its use has been largely limited to research, motorsport, and luxury vehicle activities. Given its potential, this effort provides a review and summary of AM work completed in this field including design optimization, prototyping, tooling and indirect manufacturing, part production, and remanufacturing and repair for IC engine components.
Gray, Jamee, Depcik, Christopher
Downsized-Boosted Gasoline Engine with Exhaust Compound and Dilute Advanced Combustion2020-01-07954/14/2020
This article presents experimental results obtained with a disruptive engine platform, designed to maximize the engine efficiency through a synergetic implementation of downsizing, high compression-ratio, and importantly exhaust-heat energy recovery in conjunction with advanced lean/dilute low-temperature type combustion. The engine architecture is a supercharged high-power output, 1.1-liter engine with two-firing cylinders and a high compression ratio of 13.5: 1. The integrated exhaust heat recovery system is an additional, larger displacement, non-fueled cylinder into which the exhaust gas from the two firing cylinders is alternately transferred to be further expanded. The main goal of this work is to implement in this engine, advanced lean/dilute low-temperature combustion for low-NOx and high efficiency operation, and to address the transition between the different operating modes. Those include well-mixed charge compression-ignition at low-load, and a mixed-mode combustion at higher loads, before transitioning to boosted homogenous and stochiometric spark-ignited combustion. Here, the mixed-mode combustion strategy is composed of a deflagration of a stratified mixture created by a late direct injection, then triggering a controlled autoignition of the surrounding gas, improving the robustness of lean/dilute combustion. The paper describes the key features of the engine and details regarding the combustion and multi-mode valve strategies. The experiments were performed under steady-state operation at 2000 rpm, from 1 to 11 bar IMEPn and naturally aspirated conditions. The engine demonstrated great efficiency gains compared to a conventional naturally-aspirated and downsized-boosted spark-ignited engines. The piston-compounding exhaust-heat recovery system contributes to up to 10% of the total efficiency improvement, while lean/dilute advanced combustion increases the fuel economy by up to 38% compared to a naturally aspirated engine, and up to 22%, compared to a downsized-boosted engine. NOx emissions target was met using high-levels of internal and external dilution in mixed-mode combustion operation, as well as by optimizing the injection and ignition strategy. Finally, the analysis shows that a seamless transition between the different valving strategies is achievable in support of robust transient operation.
Dernotte, Jeremie, Najt, Paul M., Durrett, Russell P.
Evaluation of Trajectory Based Combustion Control for Electrical Free Piston Engine2020-01-11494/14/2020
Previously, the authors have proposed a novel strategy called trajectory based combustion control for the free piston engine (FPE) where the shape of the piston trajectory between top and bottom dead centers is used as a control input to modulate the chemical kinetics of the fuel-air mixture inside the combustion chamber. It has been shown that in case of a hydraulic free piston engine (HFPE), using active motion control, the piston inside the combustion chamber can be forced to track any desired trajectory, despite the absence of a crankshaft, providing reliable starting and stable operation. This allows the use of optimized piston trajectory for every operating point which minimizes fuel consumption and emissions. In this work, this concept is extended to an electrical free piston engine (EFPE) as a modular power source. A dynamic model of a linear electrical free piston engine unit has been developed which consists of a single phase linear generator driven by a single cylinder engine. The linear generator unit not only provides the required electromagnetic force to ensure precise trajectory tracking for the piston in the combustion chamber, but also efficiently extracts the combustion energy to charge the battery. The concept has been experimentally validated in a hardware-in-loop setup. The combustion data corresponding to a predetermined piston trajectory is obtained from a controlled trajectory rapid compression and expansion machine (CT-RCEM) and the dynamic model is used to evaluate the electrical output corresponding to the combustion data.
Nahin, Minal, Tripathi, Abhinav, Sun, Zongxuan
Pre-design Investigation of Resonant Frequency Effects on Gas Exchange Efficiencies of a One-kW Natural-Gas Linear Engine Alternator2020-01-04884/14/2020
Performance of a natural gas two-stroke engine incorporated in a 1-kW free-piston oscillating Linear Engine Alternator (LEA) - a household electricity generator - was investigated under different resonant frequencies for pre-design phase purposes. To increase the robustness, power density, and thermal efficiencies, the crank mechanism in free-piston LEA is omitted and all moving parts of the generator operate at a fixed resonant frequency. Flexure springs are the main source of the LEA’s stiffness and the mass-spring dynamics dominates the engine’s speed. The trade-off between the engine’s performance, mass-spring system limits, and power and efficiency targets versus the LEA speed is very crucial and demands a careful investigation specifically at the concept design stages to find the optimum design parameters and operating conditions. CFD modeling was performed to analyze the effects of resonant frequency on the engine’s gas exchange behavior. To take combustion effects into account, a semi-empirical method was employed to obtain the initial and boundary conditions during the gas exchange from experiments and imported into CFD simulation. The numerical results of the gas exchange were validated at the engine speed of 5400 RPM with the experimental results. The semi-empirical method eliminated the complicated combustion simulation and significantly reduced the computational time and well-matched with experiments within 1 % error. Results showed enhanced trapping efficiency of 7.1% per 1000 RPM, and reduced scavenging efficiencies of 5.5% per 1000 RPM as speed engine’s speed increased. Comparison of the trapping and scavenging efficiencies showed an improved fuel/power efficiency equal to about 1.45 % per each 15 Hz increase in the LEA resonant frequency.
Zamani Meymian, Nima, Darzi, Mahdi, Johnson, Derek, Famouri, Parviz
Statistical Analysis of the Results Obtained by Thermodynamic Methods for the Determination of TDC Offset in an Internal Combustion Engine2020-01-13504/14/2020
Presented is a comprehensive evaluation of thermodynamic techniques used for the determination of top dead centre (TDC) in an internal combustion engine (ICE). This work thoroughly explores the assumptions made in thermodynamic calibration and assesses the impact these have through a rigorous sensitivity analysis, not previously attempted in any other study. The results of this work are presented as kernel density estimates (KDEs), an estimate of the probability density function (pdf), in order to offer both qualitative and quantitative assessments of the loss angle and the influence of the assumptions underpinning the loss angles determination. Thermodynamic loss angles ranging between -0.5°CA and -0.6°CA have been found for the engine under investigation.
Lodi, Faisal, Jafari, Mohammad, Brown, Richard, Bodisco, Timothy
Fourier Transform Infrared Spectroscopy Models to Predict Cetane Number of Different Biodiesels and Their Blends2020-01-06174/14/2020
The ignition quality of a fuel is described by its cetane number. Experimental methods used to determine cetane number employ Co-operative fuel research (CFR) engine and Ignition quality tester (IQT) which are expensive, have less repeatability and require skilled operation, and hence least preferred. There are many prediction models reported, which involve number of double bonds and number of carbon atoms whose determination is not direct. Using models that relate biodiesel composition to its cetane number is limited by the range of esters involved. Hence, a model to predict cetane number of biodiesels that addresses the limitations of the existing models, without ignoring the influence of factors such as degree of unsaturation and number of carbon atoms, is needed. Fourier transform infrared spectroscopy (FTIR) could be one such method. Five biodiesels with significant compositional variations were prepared from Camelina, Coconut, Karanja, Linseed and Palm oils, and blended in different volume proportions to arrive at 70 samples. The range of cetane number covered was from 42.2 to 65.4. Peak absorbance of different functional groups of these samples and peak ratios were determined using FTIR which were correlated to their cetane number to develop prediction models using regression. These models were validated using biodiesels data that are not used in developing them. Mean absolute deviation and Mean absolute percentage error were the statistical parameters used to compare the proposed model with existing models whose values turned out to be considerably good.
Bukkarapu, Kiran Raj, Krishnasamy, Anand
Knock, Auto-Ignition and Pre-Ignition Tendency of Fuels for Advanced Combustion Engines (FACE) with Ethanol Blends and Similar RON2020-01-06134/14/2020
Researchers have known about a higher pre-ignition frequency of alcohol fuels for several decades now. Several studies, assessing the effect of ethanol addition on stochastic pre-ignition, have shown contradicting observations. Researchers at FEV observed an increase in pre-ignition frequency with an increase in ethanol concentration, however the pre-ignition events at high ethanol content did not lead to super-knock. Most of the studies have used varying ethanol fraction in a common base-fuel, thereby varying the auto-ignition tendency of the blend. In the current study, the effect of ethanol addition on FACE (Fuels for Advanced Combustion Engines) gasolines is assessed. Five different FACE gasolines (FACE A, C, I, J and G) were used for the study. Ignition delay time of varying ethanol fractions in FACE gasolines was measured in an Ignition Quality Tester (IQT), following ASTM 6890. The measurements showed that 13% ethanol (v/v) is needed for FACE A and C, while 27% ethanol (v/v) is needed for FACE I and J to match the ignition delay time of FACE G fuel. The five blends were tested in a Co-operative Fuel Research (CFR) engine in Homogeneous Charge Compression Ignition (HCCI) and Spark Ignition (SI) combustion mode. The experiments showed similar auto-ignition and knocking tendency for the five blends. After that, the pre-ignition tendency of the blends was assessed in a supercharged AVL engine. In general, increasing ethanol content led to higher pre-ignition frequency. Moreover, the effect of ethanol on increasing pre-ignition frequency was dependent on the base-fuel into which ethanol was added. For the same ethanol fraction added, base-fuels with higher aromatic content showed higher pre-ignition frequency.
Singh, Eshan, Dibble, Robert
Influence of Nozzle Opening Pressure, Fuel Injection Timing and Compression Ratio on the Performance of Compression Ignition Engine Fueled with Biodiesel-Diesel-Butanol Blends2020-01-02994/14/2020
Biodiesel from vegetable waste can be utilized as fuel for compression ignition engine. This experimental study used biodiesel extracted from the cauliflower outer leaves and butanol from vegetable waste as property enhancer to fuel the diesel engine. This study consists of two stages: Solubility and properties test of various proportions of diesel biodiesel butanol blends to obtain an optimal fuel blend that possesses closer properties to that of diesel; followed by testing the optimal blend in a modified engine for nozzle opening pressure (180, 190, 200 and 210 bar), fuel injection timing (23, 26, 29 and 320 before top dead centre) and compression ratio (16: 1, 17.5:1, 19:1 and 20.5:1). The optimal level of these parameters was attained using L16 orthogonal array and Taguchi method. Test results showed that the blend containing 40% biodiesel 20% diesel and 40% butanol can be used as fuel for diesel engine. The diesel engine was operated under 210 bar of nozzle opening pressure, 260before top dead center of fuel injection timing and 19:1 of compression ratio. This optimal blend produced closer brake thermal efficiency, in-cylinder peak pressure, peak heat release rate, ignition delay, and combustion duration which were found to be similar compared to that of diesel (above 40% of rated power). The emissions produced by this blend were found lower compared to that of diesel operated at higher brake power condition (above 50% of rated power). This study enables to utilize the waste vegetables and renewable resources to fuel diesel engine and replacing the diesel to a certain extent.
B, Prabakaran
Development of Dual Fuel Engine Fueled with Used Cooking Oil Biodiesel and Ethanol-an Experimental Study on Performance and Combustion Characteristics2020-01-08034/14/2020
This paper investigates the performance and combustion characteristics of a compression ignition engine (CI engine) fueled with Used Cooking Oil Biodiesel (UCOB) and ethanol in dual fuel mode. In this study, UCOB was injected as the main fuel through a conventional mechanical fuel injection system. Various mass flow rates of ethanol were inducted as primary fuel through the engine intake manifold using a separate fuel injection system. Mass flow rates of ethanol were metered by an electronic control circuit. The engine test was conducted under different load conditions from no load to full load in a fully instrumented direct injection, water-cooled compression ignition engine. The results indicated that the dual fuel engine produced higher brake thermal efficiency, cylinder pressure, heat release rate with lower specific fuel consumption at a higher load condition. However, it was found that combustion characteristics improved marginally at the lower load conditions.
Velmurugan, Ramanathan, Mayakrishnan, Jaikumar, Palanimuthu, Vijayabalan, Nandagopal, Sasikumar, Elumalai, Sangeethkumar, Anaimuthu, Shridhar, Busireddy, Vamshidhar
A Real-Time Capable and Modular Modeling Concept for Virtual SI Engine Development2020-01-05774/14/2020
Spark Ignited (SI) combustions engines in combination with different degrees of hybridization are expected to play a major role in future vehicle propulsion. Due to the combustion principle and the related thermodynamic efficiency, it is especially challenging to meet future CO2 targets. The layout and optimization of the overall system requires novel methods in the development process which feature a seamless transition between real and virtual prototypes. Herein, engine models need to predict the entire engine operating range in steady-state and transient conditions and must respond to all relevant control inputs. In addition, the model must feature true real-time capability. This work presents a holistic and modular modeling framework, which considers all relevant processes in the complex chain of physical effects in SI combustion. The basis is a crank-resolved cylinder model which describes gas exchange and compression to determine the thermodynamic state and turbulence conditions at spark-advance. Ignition and flame front combustion are modeled by a mechanistic, quasi-dimensional combustion model with a detailed consideration of combustion chamber geometry for flame-wall interaction. Cycle-to-cycle variations are imposed in a semi-empirical manner in order to provide realistic boundary conditions for the thermo-chemical knock model. The models are validated against engine measurements for a passenger car sized TGDI engine in a wide range of operating conditions covering the entire engine map. Emphasis is put on comparing pressure and heat release traces, not only for the mean cycle, but for the range of stochastic variations of 100 measured cycles. The validation results confirm a good level of agreement between measured and simulated results. To demonstrate capabilities of the proposed modeling concept, a model-based optimization is performed in a computational study, aiming at an optimization of engine efficiency under knocking constraints. The study examines two motoric measures, namely water injection and variable compression ratio. Finally, the optimized model runs in a transient drivecycle simulation. The test is performed on a HiL system to prove the model’s real-time capability.
Poetsch, Christoph, Wurzenberger, Johann, Katrasnik, Tomaz
Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability2020-01-05784/14/2020
This paper reports a numerical and experimental analysis on a twin-cylinder turbocharged Spark Ignition engine carried out to investigate the cylinder-to-cylinder variability in terms of performance, combustion evolution and exhaust emissions. The engine was tested at 3000 rpm in 20 different steady-state operating conditions, selected with the purpose of observing the influence of cylinder-by-cylinder A/F ratio variations and the EGR effects on the combustion process and exhaust emissions for low to medium/high loads. The experimental outcomes showed relevant differences in the combustion evolution (characteristic combustion angles) between cylinders and not negligible variations in the emissions of the single cylinder exhaust and the overall engine one. This misalignment resulted to be due to differences in the injected fuel amount by the port injectors in the two cylinders, mainly deriving from the specific fuel rail geometry. The experimental data were then used to validate a 1D engine model, integrated with refined sub-models of turbulence, combustion, heat transfer and emissions. The model takes into account the in-cylinder production of noxious species, and their propagation in the exhaust system, up to the three-way catalytic converter. A satisfactory accuracy was reached in reproducing the overall engine performance and the combustion process in the two cylinders. In particular, the emission sub-models confirmed that the variations of the cylinder-out exhaust emissions (NOx, HC and CO) were mainly due to the non-uniform effective in-cylinder A/F ratio. The proposed numerical methodology has the potential to highlight unexpected combustion non-uniformities among different cylinders and represents a powerful support to the engine design and development. It also allows for the prediction of the overall exhaust emissions at different engine operating conditions up to the entire domain, thus assisting the engine calibration phase and reducing the experimental efforts.
Marchitto, Luca, Teodosio, Luigi, Tornatore, Cinzia, Valentino, Gerardo, Bozza, Fabio
A Modular Gasoline Engine Family for Hybrid Powertrains: Balancing Cost and Efficiency Optimization2020-01-08394/14/2020
The electrification of the powertrain is a prerequisite to meet future fuel consumption limits, while the internal combustion engine (ICE) will remain a key element of most production volume relevant powertrain concepts. High volume applications will be covered by electrified powertrains. The range will include parallel hybrids, 48V- or High voltage Mild- or Full hybrids, up to Serial hybrids. In the first configurations the ICE is the main propulsion, requiring the whole engine speed and load range including the transient operation. At serial hybrid applications the vehicle is generally electrically driven, the ICE provides power to drive the generator, either exclusively or supporting a battery charging concept. As the ICE is not mechanically coupled to the drive train, a reduction of the operating range and thus a partial simplification of the ICE is achievable. The paper shows the advances on a modular powertrain technology approach with different combinations of ICE, electrification and transmission variants, based on an engine family architecture with common parts, machining and assembly concepts, as well as the feasibility to integrate different technology packages, such as variabilities on the cranktrain and valve train, advanced, electrically assisted boosting technologies, high pressure injection or water injection. The focus of the modular approach is on a balanced overall complexity of the powertrain with increasing electrical power in regard of cost and CO2-reduction.
Schoeffmann, Wolfgang, Howlett, Michael, Fuerhapter, Alois, Kapus, Paul, Sams, Christoph, Sorger, Helfried
Assessment of the Ignition System Requirement on Diluted Mixture Spark Engines2020-01-11164/14/2020
In order to face the new challenges, spark ignition engines are evolving by following some strategies and technologies. Among them, alternative combustion processes based on the dilution of the homogeneous mixture, either with fresh air or with Exhaust Gas Recirculation (EGR), are being explored. In a higher or lower extent, these changes modify in-cylinder thermodynamic conditions during the engine operation (pressure, temperature and gas composition) thus conditioning the spark ignition system requirements that will have to evolve to become more reliable and powerful. In this framework, an experimental study on the effect of the key in-cylinder conditions on the ignition system performance has been carried out in a single-cylinder spark-ignition (SI) research engine. The study includes EGR, lambda and energizing time sweeps to assess the behavior of the engine in different operating conditions. Furthermore, various Insulated-Gate Bipolar Transistors (IGBT) and spark plugs have been tested to assess the influence of these components on the ignition process at high diluted mixtures. Conclusions show that diluted mixtures (with EGR or lambda), even though they require more spark energy to achieve a stable combustion, have up to 4% benefit on indicated efficiency, providing that the combustion propagates adequately. However, at high diluted conditions the combustion is compromised, so two different approaches were explored to improve it. Whilst it was checked that increasing the clamping value of the IGBT does not necessarily imply a better combustion in all scenarios, the increment of the electrodes gap of the spark plug would require higher clamping voltage at the IGBT, and it would have a slight benefit on efficiency providing that the rest of components, in particular the coil, are adequate.
Molina, Santiago, Martin, Jaime, Novella, Ricardo, Gomez-Soriano, Josep, Padilla, Jose
On Maximizing Argon Engines' Performance via Subzero Intake Temperatures in HCCI Mode at High Compression Ratios2020-01-11334/14/2020
The improvement of the indicated thermal efficiency of an argon power cycle (replacing nitrogen with argon in the combustion reaction) is investigated in a CFR engine at high compression ratios in homogeneous charge compression ignition (HCCI) mode. The study combines the two effects that can increase the thermodynamic efficiency as predicted by the ideal Otto cycle: high specific heat ratio (provided by argon), and high compression ratios. However, since argon has relatively low heat capacity (at constant volume), it results in high in-cylinder temperatures, which in turn, leads to the occurrence of knock. Knock limits the feasible range of compression ratios and further increasing the compression ratio can cause serious damage to the engine due to the high pressure rise rate caused by advancing the combustion phasing. The technique proposed in this study in order to avoid intense knock of an argon cycle at high compression ratios is to cool the intake charge to subzero temperatures which leads to lower in-cylinder temperatures and hence, less possibility of having knock. The main variable in this study was the intake temperature which was investigated at 40.0 °C and -6.0 °C which corresponded to low and high compression ratios, respectively. Emission analysis shows that the low in-cylinder temperature of the cooled case led to less complete combustion, and so, lower combustion efficiency. Since nitrogen is replaced with argon, NOx was only formed in negligible amounts due to some nitrogen traces in the used gasses cylinders. Furthermore, the cooled charge required more work to be done in the gas exchange process due to the decrease in the intake pressure caused by cooling the intake which deteriorated the gas exchange efficiency. The heat losses factor was found to be the main parameter that dictated the improvement of the thermodynamic efficiency and it was found that the indicated thermal efficiency was deteriorated for the cooled case as a result of all the aforementioned factors. Although the values of the thermodynamic efficiency at high compression ratios did not meet the expectations based on the ideal Otto cycle due to the assumptions of the ideal cycle, the obtained values, in general, are relatively high.
Elkhazraji, Ali, Mohammed, Abdulrahman, Jan, Sufyan, Masurier, Jean-Baptiste, Dibble, Robert, Johansson, Bengt
Effects of Direct Injection Timing and Air Dilution on the Combustion and Emissions Characteristics of Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine2020-01-11394/14/2020
Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of conventional spark ignition (SI) gasoline engines, due to shortened combustion processes caused by multi-point auto-ignition. However, its commercial application is limited by the difficulties in controlling ignition timing and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion, a concept in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites in the increasing in-cylinder temperature during flame propagation, was proposed to overcome these challenges. The combustion and emissions characteristics in the SFI hybrid combustion were experimentally investigated in a single-cylinder 4-stroke gasoline engine operating at medium to high loads when direct injection timing was retarded from -100 °CA to -40 °CA after top dead center (ATDC) and excess air coefficient was increased from 1.0 to 1.2 at the direct injection ratio of 30%. The experimental results show that direct injection timing and excess air coefficient control the ignition timing and combustion duration. Ignition timing advances with increased excess air coefficient at the same direct injection timing. Long combustion duration occurs at earlier direct injection timing close to -100 °CA ATDC or very late direct injection timing near -40 °CA ATDC at different excess air coefficients. In the meantime, combustion duration reduces with increased excess air coefficient when auto-ignition occurs during the combustion processes, while it increases with excess air coefficient without auto-ignition. Nitrogen oxides emissions increase first and then decrease with retarded direct injection timing at different excess air coefficients, and their maximum values occur at the direct injection timing of -60°CA ATDC.
Fu, Xue-Qing, He, Bang-Quan, Li, Hongtao, Chen, Tao, Zhao, Hua, Yang, Jian-Jun, Liu, Shuang-Xi, Gao, Haiyang
Comparative Analysis between a Barrier Discharge Igniter and a Streamer-Type Radio-Frequency Corona Igniter in an Optically Accessible Engine in Lean Operating Conditions2020-01-02764/14/2020
Among plasma-assisted ignition technologies, the Radio-Frequency (RF) corona family represents an interesting solution for the ability to extend the engine operating range. These systems generate transient, non-thermal plasma, which is able to enhance the combustion onset by means of thermal, kinetic and transport effects. Streamer-type RF corona discharge, at about 1 MHz, ignites the air-fuel mixture in multiple filaments, resulting in many different flame kernels. The main issue of this system is that at high electrode voltage and low combustion chamber pressure a transition between streamer and arc easily occurs: in this case transient plasma benefits are lost. A barrier discharge igniter (BDI), supplied with the same RF energy input, instead, is more breakdown-resistant, so that voltage can be raised to higher levels. In this work, a streamer-type RF corona igniter and a BDI were tested in a single-cylinder optical engine fueled with gasoline. Combustion behavior was characterized at stable, near-stable and unstable conditions (depending on IMEP coefficient of variation), increasing the air-fuel ratio starting from a near-stoichiometric mixture. For each test point the maximum allowable electrode voltage for both the igniters was used: in the streamer-type corona case it had to be limited because of the arc transition. Both indicating and imaging analysis were carried out, the latter by means of a high-speed camera that records the natural luminosity of early flames. Raw exhaust gas analysis was carried out as well. Results in terms of cycle-to-cycle variability, combustion duration, pollutant emissions, flame radii evolution and flame growth speed, as well as flame probability presence, are presented. The outcomes of this research can improve the knowledge on streamer-type corona and BDI and can be used to assess the operating range for the control parameters of these igniters.
Cruccolini, Valentino, Discepoli, Gabriele, Ricci, Federico, Petrucci, Luca, Grimaldi, Carlo, Papi, Stefano, Dal Re, Massimo
Influence of Nano Alumina Oxide Addition on the Performance of Diesel Engine Fueled with Nonedible Oil Biodiesel-Butanol Blends2020-01-50363/10/2020
Biodiesel and butanol are best-suited liquid fuels to fuel compression ignition engines. This experimental study is to investigate the effects of nano alumina on the performance of a variable compression ratio engine fueled with biodiesel-butanol blends. The experiment was conducted in two stages: Arriving at an optimal blend of biodiesel and butanol from the property testing of the blends followed by fueling the optimal blend containing 50% biodiesel and 50% butanol with nano alumina in four proportions (25, 50, 75, and 100 ppm) variable compression ratio engine. The compression ratio was varied as 16:1, 19:1, and 20.5:1. The compression ratio of the engine was varied by the increase and decrease of the clearance volume as the engine used was a variable compression ratio engine. Nano alumina was blended with biodiesel-butanol blend by ultasonication. The results of the property testing showed that the addition of butanol into biodiesel reduced the kinematic viscosity, cetane number, flash point, energy content, and an increase in oxygen content and heat of vaporization. The addition of nano alumina into biodiesel-butanol blend improved the energy content and cetane number significantly. The significance in the addition of nano alumina is that it is a combustion enhancer and due to its micro explosion and catalytic action, an increase in the rate of oxidation was improved. The engine results were compared with the characteristics of diesel fuel. The engine test results showed that the optimal blend with 100 ppm of nano alumina produced brake thermal efficiency, incylinder peak pressure, peak heat release rate, and ignition delay closer to that of diesel at compression ratio 19:1. However, the increase of compression ratio beyond this produced adverse results. The emissions of oxides of nitrogen and smoke from the engine fueled with the optimal blend and 100 ppm nano alumina were also found closer to that of diesel.
Prabakaran, B.
A Time-Saving Methodology for Optimizing a Compression Ignition Engine to Reduce Fuel Consumption through Machine Learning03-13-02-00192/7/2020
Applying a suitable design optimization technique is a crucial task for optimizing compression ignition engines because of the time-consuming process of optimization even with advanced supercomputers. Traditional computational fluid dynamics (CFD) used in conjunction with design of experiment (DOE) methods requires executing the CFD model several times. A response surface is usually fitted to relate the inputs to the outputs, which is often created based on linear regression. This method is not well suited to capture interaction effects between inputs and nonlinearities existing during engine combustion. A combination of genetic algorithm (GA) and CFD tools usually eventuates better optimum results. However, the CFD simulations must be executed sequentially, resulting in extremely high computational times, which makes it impossible to apply an optimization study using a single desktop computer. The current study examines a novel approach, which combines CFD, GA, and a type of machine learning approach, namely artificial neural networks (ANNs), in order to optimize a compression ignition engine to achieve its minimum indicated specific fuel consumption (ISFC). Start of injection (SOI) timing and input pressure were selected as the optimization variables in order to investigate improvement in ISFC without any hardware modifications of the engine. Maximum in-cylinder peak pressure and ringing intensity (pressure rise rate) were chosen as the optimization constraints. Conducting a reliable optimization study with a single desktop computer in a shorter time can be achieved by using the proposed methodology. The results indicate that a 97% decrease in the estimated number of days to achieve the final results was obtained, compared to the traditional CFD-GA approach. Furthermore, adopting this methodology eliminates the necessity for additional response surface fitting to GA data. Therefore, it facilitates an examination of design parameter effects on the engine outputs, doing sensitivity analysis, post-processing the optimization results, and providing a powerful tool to gain optimum designs. The final optimum point illustrates a 10% improvement in ISFC, while avoiding sensitive regions and without exceeding optimization constraints.
Rahnama, Pourya, Arab, Majid, Reitz, Rolf D.
Optimization of Intake Port and Pentroof Angle for Simultaneous Reduction of Fuel Consumption and Exhaust Emissions in a GDI Engine03-13-03-00202/4/2020
This article aims to identify the best combination of intake port angle (IPA) and cylinder head pentroof angle (PA) of a gasoline direct injection (GDI) engine to achieve a simultaneous reduction in the fuel consumption and the exhaust emissions using computational fluid dynamics (CFD) and optimization techniques. The present study is carried out on a single-cylinder, four-stroke GDI engine. The design space is bound by the range of the IPA (35°, 80°) and the PA (5°, 20°). The initial data set consists of 80 design points, which are generated using the uniform Latin hypercube (ULH) algorithm. CFD simulations were carried out at all the points in the initial data set using CONVERGE at engine speed of 2,000 rev/min and the overall equivalence ratio of 0.7 ± 0.05. A prediction model based on the support vector machine algorithm is generated between the design inputs and the output parameters viz., indicated specific fuel consumption (ISFC), hydrocarbon (HC), nitric oxides (NOx), and soot. After sufficient validation of the prediction model, it is used for the optimization study. The optimization is carried out using the MOGA-II algorithm. The optimization study predicted that the IPA of 58° and the PA of 13.4° results best, in simultaneous reduction of the fuel consumption and the emissions. The results of the optimization study are further validated using the CFD analysis, which is carried out at the optimum design point. From the results, it is concluded that the optimization-driven design techniques could be effectively used to improve the engine performance and reduce the emissions simultaneously.
Saw, Om Prakash, Addepalli, Srinivasa Krishna, Mallikarjuna, J.M.
The Experimental Investigation of the Performance and Emissions Characteristics of Direct Injection Diesel Engine by Bio-Hydro Fined Diesel Oil and Diesel Oil in Different EGR2019-32-05951/24/2020
Bio-hydro fined diesel (BHD) oil is known as a second generation oil made from bio hydro finning process. Biodiesel in the first generation is made from transesterification process and it has several disadvantages such as high density and increased the viscosity that can cause operational problems because can make some deposits in the engine. To overcome this, the second generation process of biodiesel has been modified from the first generation oil. BHD is made from the waste cooking oil by using the hydro finning process without the trans-esterification process. The results of BHD oil has nearly the same with diesel oil. BHD oil has low viscosity and high oxidation stability. Therefore, BHD oil can be used in the diesel engine without making any modifications in the engine. In this study, the comparison of performance and emissions characteristics from BHD oil, waste cooking oil, and diesel oil are investigated. The experimental conditions are varied for loads (low load and partial load) and exhaust gas circulations (EGR) are zero, 10, and 20%. The engine speed was constant at 2000 rpm. The results show that the BHD oil can be an alternative fuel to replace the diesel oil because the emissions can be reduced from diesel oil, therefore it is friendly to the environment.
Bhikuning, Annisa, Li, Xin, Koshikawa, Shoi, Matsumura, Eriko, Senda, Jiro
Improvements to a CFR Engine Three Pressure Analysis GT-Power Model for HCCI and SI Conditions2019-32-06081/24/2020
While experimental data measured directly on the engine are very valuable, there is a limitation of what measurements can be made without modifying the engine or the process that is being investigated, such as cylinder temperature. In order to supplement the experimental results, a Three Pressure Analysis (TPA) GT-Power model of the Cooperative Fuel Research (CFR) engine was previously developed and validated for estimating cylinder temperature and residual fraction. However, this model had only been validated for normal and knocking spark ignition (SI) combustion with RON-like intake conditions (naturally aspirated, <52 °C). This work presents improvements made to the GT-Power model and the expansion of its use for HCCI combustion. The burn rate estimation sub-model was modified to allow for low temperature heat release estimation and compression ignition operation. After this, several updates were made in the GT-Power model parameters so that the air and fuel charge mass was correctly predicted under these different combustion (SI vs. HCCI) and intake conditions (boosted or heated). Thermodynamic verifications were made to compensate for uncertainty in some of the measured operating parameters, such as compression ratio, in the CFR engine. The updated CFR model was used to obtain the cylinder pressure-temperature trajectories of both HCCI and SI cases under different levels of intake pressure, intake temperature, and speed. Two additional common cylinder temperature estimation methods were compared to the results of the GT-Power model.
Pulpeiro Gonzalez, J., Waqas, M. U., Kolodziej, C. P., DelVescovo, D., Ross, T. G.
Scavenging Phenomena Based Post-oxidation in Exhaust Manifold of a Turbocharged Spark Ignition Engine2019-01-219712/19/2019
In this research, a novel methodology for the post-oxidation in a turbocharged spark ignition (SI) engine is proposed and investigated that can improve the emissions along with the reduction in turbo-lag. In this research, both simulation and experimental activities are performed. The 1-D simulation model was used for the identification of efficient scavenging. Thereafter, experimental validation tests for modeling and post oxidation were conducted on a 4-cylinder turbocharged SI engine. From the results, it was revealed that efficient scavenging and post-oxidation can be obtained at lower speed and higher load. The enthalpy in exhaust manifold increased due to the post-oxidation reaction which in turn increased the temperature and pressure of the exhaust gases and hence emissions reduced. Also, due to the increased enthalpy at turbine upstream, the turbocharger speed increased and as a consequence, reduction in the turbo-lag was observed. It was also noted that the post-oxidation is limited at higher load and overlap in an inline 4-cylinder engine due to the strong scavenging which increased the cooling effect in in-cylinder and exhaust manifold due to excess air.
Kumar, Madan, Kuboyama, Tatsuya, Hasegawa, Naohiro, Moriyoshi, Yasuo
Potential for Emission Reduction and Fuel Economy with Micro & Mild HEV2019-28-250411/21/2019
The development of modern combustion engines (spark ignition as well as compression ignition) for vehicles compliant with future oriented emission legislation (BS6, Euro VI, China 6) has introduced several technologies for improvement of both fuel efficiency as well as low emissions combustion strategies. Some of these technologies as there are high pressure multiple injection systems or sophisticated exhaust gas after treatment system imply substantial increase in test and calibration time as well as equipment cost. With the introduction of 48V systems for hybridization a cost- efficient enhancement and, partially, an even attractive alternative is now available. An overview will be given on current technologies as well as on implemented test procedures. The focus will be on solutions which have potential for the Indian market, i.e. solutions which can be implemented with moderate application effort for currently available compact and medium size cars. The possibilities of 48V technologies for fuel economy and emission reduction will be discussed. Simultaneously, tools for testing and calibration at power train testbed as well as for on-road application will be presented. Furthermore, it considers the requirements on the test procedures due to the transition from NEDC to WLTP and the implications of the demand for greater integration of tests under real driving conditions (RDE).
Murr, Franz, Winklhofer, Ernst, Weissbaeck, Michael, Teuschl, Gerald
Optimization of Compression Ratio for DI Diesel Engines for Better Fuel Economy2019-28-243111/21/2019
Fuel economy is becoming one of the key parameter as it does not only account for the profitability of commercial vehicle owner but also has impact on environment. Fuel economy gets affected from several parameters of engine such as Peak firing pressure, reduction in parasitic losses, volumetric efficiency and thermal efficiency. Compression ratio is one of key design criteria which affects most of the above mentioned parameters, which not only improve fuel efficiency but also results in improvement of emission levels. This paper evaluates the optimization of Compression ratio and study its effect on Engine performance. The parameters investigated in this paper include combustion bowl volume in Piston and Cylinder head gasket thickness as these are major contributing factors affecting clearance volume and in turn the compression ratio of engine. Based on the calculation results, an optimum Compression Ratio for the engine is selected. Further Engine testing carried out with selected Compression ratios and parameters such as Fuel efficiency, In-cylinder pressure, and Brake thermal efficiency and Ignition delay were compared.
Gavade, Sujit, Bhargava, Aashish, Soni, Gaurav, Deshmukh, Chandrakant
Assessing the Combined Outcome of Rice Husk Nano Additive and Water Injection Method on the Performance, Emission and Combustion Characters of the Low Viscous Pine Oil in a Diesel Engine2019-01-260410/22/2019
The research work intends to assess the need and improvement by using a low viscous bio oil, RH (rice husk) nano particles and water injection method in enhancing the performance, emission and combustion characters of a diesel engine. One of the major setbacks for using biodiesel is its higher viscosity. Hence, a low viscous oil (pine oil) which does not need transesterification process was used as a biofuel in this study. Further, to improve its characteristics a non-metallic nano additive produced from rice husk was added at 3 proportions (50, 100, 200 ppm) and the optimal quantity was found as 100 ppm based on the BTE (brake thermal efficiency) value of 30.2% at peak load condition. This efficiency value was accompanied by a considerable decrease in pollutants like HC (hydrocarbon)-34.8%, Smoke-31.6%, CO (carbon monoxide)-43.7%. On the contrary, NOx (oxides of nitrogen) emission was found to be increased for all load values. At peak load, when compared with diesel, pine oil with RH has 19.3% increased NOx emission. To reduce this increased NOx emission, water was injected at the inlet manifold along with the incoming fresh air at 1%, 2% and 3% by volume. Pine oil provided better peak pressure and heat release rate values which was well aided with the RH additive. The RH additive helped in providing better performance and emissions results also. The negative effect being the increased amount of NOx formation, which was reduced considerably (-13.15%) by using water injection process. 2% of water injection was found to be a well-balanced quantity, that does not greatly affect the performance and other emissions. Additionally, ANN (Artificial Neural Network) was used as a theoretical analysis. The network was trained and validated using the known experimental values to help in predicting unknown values during necessity.
P, Mebin Samuel, Gobalakichenin, Devaradjane, V, Gnanamoorthi
Feasibility of Multiple Piston Motion Control Approaches in a Free Piston Engine Generator2019-01-259910/22/2019
The control and design optimization of a Free Piston Engine Generator (FPEG) has been found to be difficult as each independent variable changes the piston dynamics with respect to time. These dynamics, in turn, alter the generator and engine response to other governing variables. As a result, the FPEG system requires an energy balance control algorithm such that the cumulative energy delivered by the engine is equal to the cumulative energy taken by the generator for stable operation. The main objective of this control algorithm is to match the power generated by the engine to the power demanded by the generator. In a conventional crankshaft engine, this energy balance control is similar to the use of a governor and a flywheel to control the rotational speed. In general, if the generator consumes more energy in a cycle than the engine provides, the system moves towards a stall. If the generator consumes less energy, then the effective stroke, compression ratio and maximum translator velocity must rise steadily from cycle-to-cycle until the heat transfer losses stop the increase. Moreover, when stiff springs are added to the FPEG system, the dynamics becomes more sinusoidal and more consistent with increasing spring stiffness. To understand the behavior of proposed control and cycle-to-cycle variations, a comprehensive FPEG numerical model with a 1 kW target electric power was developed in MATLAB®/Simulink. An FPEG system corresponding to that numerical model has been operated in the laboratory. This MATLAB®/Simulink numerical model has been used to examine the sensitivity of FPEG dynamics and performance parameters to the changes in design and operating inputs. A difficulty during the modeling is associated with the cycle-to-cycle energy balance, and this difficulty is also reflected in the real-world FPEG control. Therefore, the authors have devised a control strategy similar to the real world intended control methodology. In this numerical model, two different feedback control methodologies were implemented and investigated. These control methodologies were applied to regulate the generator load with selected control or input variables, namely peak pressure, mid-stroke piston velocity, trapped compression ratio and dead center set points. The controllers with optimized coefficients demonstrated the feasibility of energy balance management during the transient operation. Based on the simulation results, the controllers with compression ratio, peak pressure and dead center clearance set points as control variables demonstrated stable FPEG operation whereas the mid-stroke velocity failed to achieve the steady-state operation due to deviation in the piston dynamics. The simulation results from this study will be used as the pathway for improving and optimizing the experimental FPEG design.
Bade, Mehar, Clark, Nigel, Famouri, Parviz, Guggilapu, PriyaankaDevi
Experimental Investigation on Performance of a Variable Compression Ratio Engine Fueled with Diesel Butanol Blends with Nano Additives2019-28-015710/11/2019
Butanol is an attractive alcohol having closer properties to that of diesel. This experimental study is to investigate the performance of a variable compression ratio engine fueled with diesel butanol blends enhanced by two nano additives (nano alumina and nano zinc oxide) in various proportions. To start with a solubility test was conducted with various proportions of diesel and butanol (0% to 50%). Optimal blend as (50% diesel and 50% butanol) from diesel butanol blends was selected from this step. Nano zinc oxide (100 - 500ppm) and nano alumina (0 - 100ppm) were blended with this optimal blend through ultasonication. This blend was tested for essential properties such as cetane number, energy content, kinematic viscosity, oxygen content, the heat of vaporization and flash point. Out of the 10 proportions of diesel butanol blends with nano-additives, two blends were chosen with respect to the properties in comparison to that of diesel. These two blends were tested in a variable compression ratio engine by varying compression ratios (16: 1, 17.5:1, 19:1 & 20.5:1) under various load conditions. Results indicated that the compression ratio 19:1 was found suitable for these two blends. Brake thermal efficiency, peak in-cylinder pressure, peak heat release rate, ignition delay, emissions of oxides of nitrogen and smoke produced by these blends at 19:1 compression ratio was found closer to that of diesel. However, the emissions of hydrocarbons and carbon monoxide produced by these blends operated under 19:1 compression ratio was found slightly higher compared to that of diesel.
Balasubramanian, Prabakaran
Experimental Study on Combined Effect of Yttria Stabilized Zirconia Coated Combustion Chamber Components and Emulsification Approach on the Behaviour of a Compression Ignition Engine Fuelled with Waste Cooking Oil Methyl Esters2019-28-016410/11/2019
Waste Cooking Oil (WCO) is generated in large quantity worldwide due to the increase in population and change of food habits. This work is about utilizing this WCO as an alternative fuel for Compression Ignition (CI) engine, in view of addressing the constraints in the domain of land as well as air pollution. A fuel and engine level modification were carried out to analyse the behaviour of the test engine. In the first phase of the study, collected WCO was converted into its methyl esters (i.e. WCOME) and tested for its properties. A single cylinder, water cooled, direct injection, compression ignition engine was developed with suitable emission and combustion parameters computing equipments in the second phase of the work. In the third phase of the work, the developed engine was tested with neat diesel, WCO and WCOME under different engine power outputs. WCOME was converted into its emulsion (WCOMEE) and tested in the developed engine in the fourth phase of the work. In the fifth phase of the study, combustion chamber components like piston, cylinder head and valves were coated with 100 microns of Nickel-Chromium Aluminium (NiCrAl) bond coat and 200 microns of 8% Yttria Stabilized Zirconia (YSZ) ceramic coat as a Thermal Barrier Coating (TBC) using plasma spray coating technique. Finally, the modified engine was tested with the WCOMEE and results were compared. Carbon-based emissions of WCOMEE were also found to be in the lower side with the TBC engine at the penalty of a slight increase of Oxides of Nitrogen Emission. On the other hand Brake Thermal Efficiency (BTE) of WCOMEE has been decreased from 27.2% to % with the unmodified engine. However, the BTE of WCOMEE has been significantly increased to 29.4 % when it was tested in the TBC engine. Thus, it has been proved that WCOME can be used in the emulsified form in the TBC coated CI engine for optimized performance and emission characteristics.
Elumalai, Sangeethkumar, Mayakrishnan, Jaikumar, Nandagopal, Sasikumar, Raja, Selvakumar, Velmurugan, Ramanathan
Experimental Investigation of Performance of Di Diesel Engine Fueled with Diesel Butanol Blends by Modification of Engine Operating Parameters2019-28-011210/11/2019
Butanol is an attractive fuel that can be utilized in compression ignition engines. This experimental study is to investigate the performance of direct injection diesel engine fueled with diesel-butanol blends with and without modification of engine operating parameters. This study includes three stages: Solubility of diesel butanol blends, property testing of the blends followed by an engine test with and without modification of nozzle opening pressure (190 bar, 200 bar, 210 bar and 220 bar), fuel injection timing (230, 260, 290 and 320 before top dead centre) and compression ratio (16:1, 17.5:1,19:1 and 20.5:1). Optimal parameters among these were attained by using an L16 orthogonal array and Taguchi method. Results indicated that 220 bar of nozzle opening pressure, 260 before the top dead centre of fuel injection timing and 19:1 compression ratio were found suitable for the blend containing 50% diesel and 50% butanol. This blend produced similar brake thermal efficiency, peak incylinder pressure, peak heat release rate, ignition delay, emissions of oxides of nitrogen and smoke. However, the emissions produced by this blend were found slightly higher compared to that of diesel. The novelty in this study is the utilization of 50% of butanol and this will be produced from biomass in the nearest future.
Balasubramanian, Prabakaran
Sensitivity Analysis of the Combustion Parameters in a Stratified HCCI Engine with Regard to Performance and Emission2019-24-01149/9/2019
Homogeneous charge compression ignition (HCCI) is a promised solution to environmental and fuel economy concerns for IC engines. Engine application for HCCI engine depends on an array of parameters such as fuel type, mixture composition, intake condition and engine specification, meaning that controlling an HCCI engine can only be done through the adjustment of these parameters. In this numerical study which is driven from an experimental work, thermal and charge stratification is used to control HCCI combustion. The effect of intake temperature, compression ratio, intake pressure, EGR, reformer gas (CO-H2 mixture) and glow plug temperature on engine performance and emission was investigated using a 3D model on AVL-FIRE parallel with 1D model on GT-Power software. Then AHP model as a Multiple Attribute Decision Making method has been used to analyze the sensitivity of these parameters on performance and emission. Results indicate that increasing intake temperature causes the operating condition approaches knock which results in a narrower operating region. Increasing EGR ratio makes possible the expanding of operating range rich limit since it causes delayed combustion start, prolonged combustion duration and avoids knocking. The use of reformer gas expands the operating range lean limit and increases the possibility of engine well operation in this region. However, the change in reformer gas composition does not have a great influence on combustion. Using glow plug advances combustion while prolonging burn duration. Therefore, in-cylinder thermal stratification pushes engine operating points toward rich limit and as a result high power achievement becomes possible. Finally the sensitivity analysis results show that the EGR is the most effective parameter on combustion. In this analysis, the sensitivity of inlet pressure, reformer gas ratio, compression ratio, inlet temperature, reformer gas composition, and glow plug temperature point are in the next ranks respectively.
Pourfallah, Mohsen, Armin, Mahboud
Fuel Consumption and Pollutant Emission Optimization at Part and Full Load of a High-Performance V12 SI Engine by a 1D Model2019-24-00809/9/2019
Modern internal combustion engines show complex architectures in order to improve their performance in terms of brake torque and fuel consumption. Concerning naturally-aspirated engines, an optimization of the intake port geometry, together with the selection of a proper valve timing, allow to improve the cylinder filling and hence the performance. The identification of an optimal calibration strategy at test bench usually requires long and expensive experimental activities. Numerical tools can help to support engine calibration, especially in the early design phases. In the present work, a 12-cylinder naturally aspirated spark ignition engine is investigated. The engine is experimentally tested under full and part load operations. Main performance parameters, in-cylinder pressure cycles and raw pollutant emissions are measured. The engine is schematized in a one-dimensional model (GT-Power™), where “user routines” are employed to simulate turbulence, combustion, knock and pollutant production. 1D model is validated against the experimental data, denoting a good accuracy. A calibration procedure is implemented by an external optimizer, coupled with the 1D engine model, with the aim of minimizing the fuel consumption. The procedure decision parameters are intake and exhaust valve timings, and combustion phasing. Proper constraints are posed for residual gas fraction and knock intensity. The optimal calibration strategies have been recognized for two operating conditions, where the engine most frequently works along an RDE driving cycles. Main drivers for engine efficiency are intake de-throttling at part load, thanks to the internal EGR caused by a Miller-Atkinson valve strategy, and cylinder filling maximization at high load. A ‘virtual’ calibration of the considered engine, employing the developed automatic procedure, is identified on completely theoretical basis. The proposed methodology shows the capability to drive and support the experimental engine calibration and presents the potential to be very helpful in reducing the related costs and time-to-market.
De Bellis, Vincenzo, Malfi, Enrica, Cacciatore, Diego, Aliperti, Antonio, Rizzi, Luca
Impact of Cooled EGR on Performance and Emissions of a Turbocharged Spark-Ignition Engine under Low-Full Load Conditions2019-24-00219/9/2019
The stringent worldwide exhaust emission legislations for CO2 and pollutants require significant efforts to increase both the combustion efficiency and the emission quality of internal combustion engines. With this aim, several solutions are continuously developed to improve the combustion efficiency of spark ignition engines. Among the various solutions, EGR represents a well-established technology to improve the gasoline engine performance and the nitrogen-oxides emissions. This work presents the results of an experimental investigation on the effects of the EGR technique on combustion evolution, knock tendency, performance and emissions of a small-size turbocharged PFI SI engine, equipped with an external cooled EGR system. Measurements are carried out at different engine speeds, on a wide range of loads and EGR levels. The standard engine calibration is applied at the reference test conditions. Then, the exhaust gas is recirculated and the load is controlled by adjusting the intake pressure, the injection and the spark timing. The main results show a significant reduction in specific fuel consumption at low load due to the lower pumping losses when EGR is active, independent on the engine speed. At high load, a lower improvement in fuel economy has been found, mainly due to a slight reduction in the knock tendency. EGR results in a reduction in NO emission at each engine speed and load, with penalties in HC emission.
Marchitto, Luca, Tornatore, Cinzia, Valentino, Gerardo, Teodosio, Luigi
CFD Analysis and Knock Prediction into Crevices of Piston to Liner Fireland of an High Performance ICE2019-24-00069/9/2019
The paper aims at defining a methodology for the prediction and understanding of knock tendency in internal combustion engine piston crevices by means of CFD simulations. The motivation for the analysis comes from a real design requirement which appeared during the development of a new high performance SI unit: it is in fact widely known that, in high performance engines (especially the turbocharged ones), the high values of pressure and temperature inside the combustion chamber during the engine cycle may cause knocking phenomena. “Standard” knock can be easily recognized by direct observation of the in-cylinder measured pressure trace; it is then possible to undertake proper actions and implement design and control improvements to prevent it with relatively standard 3D-CFD analyses. Some unusual types of detonation may occur somewhere else in the combustion chamber: knocking inside piston/liner crevices belongs to the latter category and damages on the piston top land (very similar to pitting) are one of the evidence of knock onset in this region. The very localized regions of damage onset, the cycle to cycle variability and the very short duration of the phenomena do not allow to obtain fully reliable experimental data concerning the investigated problem. A new methodology is therefore implemented in CFD to drive the root causes identification and understanding the impact of crevice design. A preliminary CFD 3D in-cylinder analysis is performed, in order to understand the criticalities in the piston to liner fireland due to local pressure and temperature temporal evolution. Then a “model reduction” is proposed, which is necessary in order to study the problem with reasonable computational costs and times. A 2D simplified model is developed which is able to maintain the possibility to correctly represent the local thermo fluid dynamic effects, especially the auto-ignition conditions. Finally, new geometries are studied in order to prevent local knocking and retard auto-ignition such to improve the KLSA.
Rosetti, Angelo, Iotti, Corrado, Bedogni, Andrea, Cantore, Giuseppe, Fontanesi, Stefano, Berni, Fabio
Oxy-Fuel HCCI Combustion in a CFR Engine with Carbon Dioxide as a Thermal Buffer2019-24-01199/9/2019
Global warming and the increasingly stringent emission regulations call for alternative combustion techniques to reduce CO2 emissions. Oxy-fuel combustion is one of those techniques since the combustion products are easily separated by condensing the water and storing CO2. A problem associated with the burning of fuel using pure oxygen as an oxidant is that it results in high adiabatic flame temperature. This high flame temperature is decreased by introducing a thermal buffer to the system. A thermal buffer in this context is any gas that does not participate in combustion but at the same time absorbs some of the released heat and thus decreases the temperature of the medium. Many experiments have been conducted to study oxy-fuel combustion in ICE using noble gases as thermal buffers. However, those experiments focused on using hydrogen as a fuel to avoid any build-up of CO2 in the system. On the contrary, the work presented in this paper investigates using CO2 as a thermal buffer for oxy-fuel combustion in HCCI engines. Experiments were performed on a standard Waukesha variable compression ratio cooperative fuel research CFR engine, modified to run in HCCI mode. Emissions were measured using an AVL SESAM-i60 FTIR spectrometer. As expected, results showed that the CO2 mixture degraded engine efficiency. The relatively lower engine temperature also decreased NOx emissions, simultaneously increasing CO and unburned hydrocarbon (UHC) emissions.
Mohammed, Abdulrahman, MASURIER, JEAN-BAPTISTE, Elkhazraji, Ali, Johansson, Bengt, Mohammed, Abdulrahman, MASURIER, JEAN-BAPTISTE, Elkhazraji, Ali, Johansson, Bengt
Compression Ratio and Intake Air Temperature Effect on the Fuel Flexibility of Compression Ignition Engine2019-24-01109/9/2019
The effect of compression ratio (CR) and intake air temperature on the combustion characteristics of fuels with different octane ratings were investigated on a single-cylinder heavy duty engine. The study focused on Primary Reference Fuels (PRFs) and commercial grade diesel with octane numbers ranging from 0 to 100. The engine was configured at a CR of 11.5:1, which is lower than typical heavy-duty compression ignition CI engines. This aims to compare the fuels’ burning regime with recently reported measurements at CR17:1. Experiments were performed at different intake air temperatures of 20 to 80 °C and net indicated mean effective pressure (IMEPNet) of 5 to 20 bar. The injection rates have been characterized to determine the hydraulic delay of the injector and thus define the actual ignition delay time. At low loads, diesel-like fuels were found to burn in partially premixed combustion (PPC) mode whereas high octane fuels did not ignite. At high loads, fuels combustion becomes diffusion driven regardless of their RON or MON values. The effect of intake air temperature on the combustion characteristics depended on the combination of the octane ratings and the engine load. At high loads, fuels with low octane numbers were insensitive to the change of the intake air temperature. The ignition delay time was short enough to maintain a diffusion driven combustion. At lower loads, it is more challenging to reach conditions where the combustion characteristics are invariant regardless of the fuel’s RON and MON values (Fuel Flexible). At the low tested compression ratio of 11.5:1, the extent of fuel flexibility is limited to only high loads (IMEPNet = 20 bar) whereas it is extended to intermediate loads (IMEPNet = 10 and 15 bar) at CR17:1.
AlRamadan, Abdullah S., Ben Houidi, Moez, Aljohani, Bassam S. E., Eid, Hassan, Johansson, Bengt
Performance and Emissions of an Advanced Multi-Cylinder SI Engine Operating in Ultra-Lean Conditions2019-24-00759/9/2019
In this work the performance and noxious emissions of a prototype Spark Ignition (SI) engine, working in ultra-lean conditions, are investigated. It is a four-cylinder engine, having a very high compression ratio, and an active pre-chamber. The required amount of air is provided by a low-pressure variable geometry turbocharger, coupled to a high-pressure E-compressor. The engine is equipped with a variable valve timing device on the intake camshaft. The goal of this activity is to support the development and the calibration of the described engine, and to exploit the full potential of the ultra-lean concept. To this aim, a combustion model for a pre-chamber engine, set up and validated in a previous paper for a similar single-cylinder unit, is utilized. It is coupled to additional in-house developed sub-models, employed for the prediction of the in-cylinder turbulence, heat transfer, knock and pollutant emissions. Such a complex architecture, schematized in a commercial 1D modeling framework, presents several control parameters which have to be properly selected to maximize the engine efficiency and minimize the noxious emissions over its whole operating domain. A Rule-Based (RB) calibration strategy is hence implemented in the 1D model to identify the optimal values of each control variable. The reliability of the RB calibration is also demonstrated through the comparison with the outcomes of a general-purpose optimizer, over a load sweep at a constant speed. The 1D model and the RB methodology are then applied for the performance prediction over the whole engine operating domain. The predicted performances show the possibility to achieve a wide zone of very high efficiency, with limited penalizations only at very low loads. Main advantages of the lean-combustion concept are highlighted, concerning a higher specific heat ratio, reduced heat losses, improved knock mitigation, and abatement of pollutant emissions, especially regarding CO and NOx. The presented methodology demonstrates to be a valuable tool to support the development and calibration of the considered high-efficiency engine architecture.
Bozza, Fabio, Tufano, Daniela, Malfi, Enrica, Teodosio, Luigi, LIBERT, Cédric, De Bellis, Vincenzo
Water Injection Contribution to Enabling Stoichiometric Air-to-Fuel Ratio Operation at Rated Power Conditions of a High-Performance DISI Single Cylinder Engine2019-24-01739/9/2019
The next generation of gasoline turbo-charged engines will have to deal with the continuous tightening of emissions regulations. In fact, to better represent real-world emission figures, WLTP and RDE cycles focus on stricter criteria; spanning higher speeds and loads potentially covering the whole engine operating map. It is common practice at present to use overfueling to avoid catastrophic failure of turbine and aftertreatment systems at very high engine speeds and loads due to excessive temperatures. A past technology, which is presently enjoying a resurgence of interest, is water injection. In particular, for high-specific-power applications, this could be used as replacement strategy for overfueling, potentially enabling full operating range stoichiometric operation with no compromise in terms of maximum performance with respect to today. In order to validate this scenario, an experimental campaign on a single cylinder engine has been carried out to highlight port water injection benefits and possible limitations at high engine speed and loads. A dedicated port injector has been characterized in a spray bomb and 3D-CFD simulations have been performed with the goal of better understanding and illustrating the air cooling effect along the water pathway from the injector tip to the cylinder charge. Detailed chemical thermo-kinetics modelling of gasoline/water gaseous mixtures was used to help separate thermal from chemical effects arising from use of a water injection system. A number of injector types, locations, water flow rates and inlet valve timings have been included in the study in order to fully explore the potential benefits of this technology.
Paltrinieri, Stefano, Mortellaro, Fabio, Silvestri, Nicola, Rolando, Luciano, Medda, Massimo, Corrigan, Daire
Ignition Delay Model of Multiple Injections in CI Engines2019-24-00719/9/2019
In compression ignition engines, the combustion starts after the ignition delay period from the start of injection. The degree of mixing between air and fuel during this period impacts combustion characteristics, such as the pressure rise rate, which worsens combustion noise. The formation of soot and nitrogen oxides can also be affected. In addition, ignition delay is essential to estimate the in-cylinder pressure. Therefore, there have been many researches performed to estimate the ignition delay for model-based control applications considering the above relations. In this study, a semiempirical and 0-dimensional ignition delay model is developed for real-time control applications. As the ignition delay consists of physical and chemical delays in compression ignition engines, the integrated ignition delay model considers both of these variables. The ignition delay was correlated with parameters such as in-cylinder charge density, local temperature, the oxygen concentration at which the fuel is injected, injection pressure and the previously injected fuel quantity. This model was applied to multiple injection conditions that are common among conventional diesel engines. A 1.6-liter diesel engine was used to verify the correlation between ignition delay and other parameters, and the established model was also validated with other engines that have different specifications than the test engine. The new 0-dimensional ignition delay model can contribute to researches such as soot model, in-cylinder pressure model and study about combustion noise, which are requiring the ignition delay period and targeting the real-time application.
Lee, Youngbok, Lee, Seungha, Min, Kyoungdoug
Response Surface Methodology (RSM) in Optimization of Performance and Exhaust Emissions of RON 97, RON 98, and RON 100 (Motor Gasoline) and AVGAS 100LL (Aviation Gasoline) in Lycoming O-320 Engine03-12-04-00298/19/2019
Federal Aviation Administration (FAA)’s 20 years of research and development with 200 unleaded blends and full-scale engine tests on 45 high-octane unleaded blends has not found a “drop-in” unleaded replacement for aviation gasoline (AVGAS) 100 low lead (100LL) fuel. In this study, analysis of compatibility via optimization of Lycoming O-320 engine fuelled with RON 97, RON 98, RON 100, and AVGAS was conducted using the Response Surface Methodology (RSM). Test fuels were compositionally characterized based on Gas Chromatography (GC) analysis and were categorized based on types of Hydrocarbon (HC). Basic fuel properties of fuels in this research were analyzed and recorded. For optimization analysis, engine speed and fuel were considered as the input parameters. The output responses were Brake Horsepower (BHP), Brake Thermal Efficiency (BTHE), Brake-Specific Fuel Consumption (BSFC), Exhaust Gas Temperature (EGT), Carbon Dioxide (CO2), Carbon Monoxide (CO), HC, and Nitrogen Oxides (NOx). The engine speed (RPM) was varied at 2000-2700, and the fuels were varied at four (04) levels, RON 97, RON 98, RON 100, and AVGAS. The design matrix was selected based on one factor of RSM with 28 experimental runs. Analysis of Variance (ANOVA) was performed on the models. Values of “Prob > F” less than 0.05, differences between “predicted R2” and “adjusted R2” of less than 0.2, and “Adequate Precision” ratios greater than 4 were used to validate the significance of the model tested. Desirability approach was applied to measure the desirability function. Input parameters, engine speed and type of fuel set to be in range, BHP and BTHE were maximized while BSFC, EGT, and all emission responses were minimized. To confirm that the model can predict actual outcomes at the optimal settings determined from the analysis, confirmation test was carried out. Results indicated that when the engine was run with a speed of 2279.064 RPM, RON 97 fuel gave optimum solution of all tested fuels, and the corresponding values of BHP, BTHE, BSFC, EGT, CO2, CO, HC, and NOx were found to be 146.669 HP, 27.7%, 0.270 Kg/kW-hr, 382.008°C, 7.162%, 7.201%, 199.460 ppm, and 51.296 ppm, respectively, with a desirability index of 0.755. Results of this study indicate that lower octane fuels are favorable in this type of engine with lower compression ratio (CR). Matching engine design and fuel octane rating plays a significant and dominant role in the performance and exhaust emission.
Kumar, Thanikasalam, Mohsin, Rahmat, Majid, Zulkifli Abd., Ghafir, Muhammad Fahmi Abdul, Kim, Je Young, Wash, Ananth Manickam
Knock and Pre-Ignition in Spark-Ignition Engine Fuelled by Different Blends of Jojoba Bio-Gasoline with Kerosene2019-01-50465/17/2019
In the present article, the knock tendency and pre-ignition resistance (PIR) were determined experimentally for different blends of kerosene and jojoba bio-gasoline. The effects of varying equivalence ratios, rotational speed, inlet air temperature and pressure, and ignition timing on knock tendency and PIR were investigated. The influence of compression ratio on PIR was also studied. Jojoba bio-gasoline was synthesized using transesterification method through performing a chemical reaction between well-stirred jojoba raw oil and alcohol. Experiments were carried out on a Ricardo E6/MS variable compression ratio spark-ignition (SI) engine fuelled by jojoba bio-gasoline/kerosene blends of volumetric percentages of 0%, 5%, 10%, 15%, and 20% jojoba bio-gasoline. The onset of pre-ignition and knock were detected by observing the pressure oscillations using a piezoelectric pressure transducer, a synchronizing magnetic sensor, and a degree-marking probe. The results showed that increasing the percentage of bio-gasoline in the blends with kerosene leads to a significant increase in PIR and a remarkable decrease in the knock tendency. This will lead to the design of a more efficient engine by increasing its compression ratio when fuelled by jojoba bio-gasoline. Analytical correlations were developed to assess the knock tendency and PIR for different fuel blends taking into consideration the various design and operating variables.
Radwan, M.S., Attai, Youssef A., Hassan, Y.I.
A Novel Laminar Flame Speed Correlation for the Refinement of the Flame Front Description in a Phenomenological Combustion Model for Spark-Ignition Engines03-12-03-00184/25/2019
This work focuses on the effects of the laminar flame speed (LFS) and flame stretch on the phenomenological modeling of the combustion process in spark ignition engines. The study is carried out using a 1D model of a small-size naturally aspirated SI engine, equipped with an external EGR circuit. The model, developed in GT-Power™ environment, includes advanced sub-models of the in-cylinder processes. The combustion is modeled using a fractal approach, where the burning rate is directly related to the laminar flame speed. A novel LFS correlation based on 1D chemical kinetics computations is presented and assessed with the experimentally derived Metghalchi and Keck correlation. Moreover, the effects of the flame stretch, evaluated according to an asymptotic theory, are properly considered in the combustion model. In order to verify the consistency and accuracy of the present approach, the model predictions are compared with the results of experimental tests performed at full- and part-load engine operations, with and without the activation of the EGR device. The proposed LFS correlation provides more accurate results than the Metghalchi and Keck one, especially for low engine loads and high EGR rates. The introduction of the flame stretch model leads to a much better prediction of the early combustion stage at low engine loads.
De Bellis, Vincenzo, Malfi, Enrica, Teodosio, Luigi, Giannattasio, Pietro, Di Lenarda, Fabio
Development of New I4 2.5L Gasoline Direct Injection Engine2019-01-11994/2/2019
A new 2.5L 4-cylinder direct-injection engine (PR25DD) was developed for use on the new 2019 model year Altima as a successor to the QR25DE engine mounted on the previous model. The development concept defined for this new 4-cylinder engine was to achieve acceleration, fuel economy and noise, vibration and harshness (NVH) performance at the highest possible levels by incorporating the latest technologies, including a world’s first application. The PR25DD engine continues Nissan’s new engine concept of recent years with regard to the basic engine systems, including the use of direct injection, an electrically operated valve timing control (VTC) system, cooled exhaust gas recirculation (EGR), an integrated exhaust manifold, mirror bore coating and a variable displacement oil pump [1]. In addition to these features, it also adopts a resin intake port. The resin port is inserted into the intake port cast in the cylinder head, thereby forming an air layer between the intake air passageway and the head inner wall so as to suppress the rise in intake air temperature. This world’s first application of a resin intake port improves anti-knock performance, thus contributing to improvements in combustion efficiency and power output. As a result, reliable improvements were implemented in the practical operating range to achieve class-leading performance in the areas of power, fuel economy and NVH. This paper describes in detail the principal technologies adopted to achieve these performance improvements.
Yoshida, Naohiro
Numerical Investigation of the Potential of Late Intake Valve Closing (LIVC) Coupled with Double Diesel Direct-Injection Strategy for Meeting High Fuel Efficiency with Ultra-Low Emissions in a Heavy-Duty Reactivity Controlled Compression Ignition (RCCI) Engine at High Load2019-01-11664/2/2019
The potential of diesel/gasoline RCCI combustion coupled with late intake valve closing (LIVC) and double direct injection of diesel for meeting high fuel efficiency with ultra-low emissions was investigated in this study. The study was aiming at high load operation in a heavy-duty diesel engine. Based on the reactivity stratification of RCCI combustion, the employment of double injection of diesel fuel provided concentration stratification of the high-reactivity fuel, which is to further realize effective control of the combustion process. Meanwhile, late intake valve closing (LIVC) strategy is introduced to control the maximum in-cylinder pressure and nitrogen oxides (NOx) emissions. By coupling KIVA-3V code with genetic algorithm (GA), six crucial operating parameters including premix ratio (PR), start of first injection (SOI1), start of second injection (SOI2), mass fraction of the first fuel injection, exhaust gas recirculation (EGR) rate, and intake temperature (Tin) were optimized to realize simultaneous minimization of fuel consumption, NOx and soot emissions in the present study. The results indicate that the soot emissions and fuel economy can be effectively decreased with the employment of two split fuel injections while the NOx is maintained under the Euro 6 limit, which demonstrates the potential of double direct-injection strategy for improving the performance of RCCI combustion with LIVC. In the evolution process, the strategies with more separated fuel injections realized by an earlier SOI1 and later SOI2 are preferred to increase the homogeneity of the cylinder charge and reduce the soot emissions. However, the amount of the premixed diesel fuel in the first injection is limited by the peak pressure rise rate (PPRR) constraint. Moreover, the double injection strategy is superior over the single injection strategy in fuel consumption due to the more near-TDC combustion phasing and in reducing the heat transfer due to the shorter combustion duration, whereas the combustion efficiency is deteriorated to some extend due to serious wall impingement with early fuel injection.
Xu, Guangfu, Jia, Ming, Xu, Zhen, Chang, Yachao, Wang, Tianyou
Sensitivity Analysis and Control Methodology for Linear Engine Alternator2019-01-02304/2/2019
Linear engine alternator (LEA) design optimization traditionally has been difficult because each independent variable alters the motion with respect to time, and therefore alters the engine and alternator response to other governing variables. An analogy is drawn to a conventional engine with a very light flywheel, where the rotational speed effectively is not constant. However, when springs are used in conjunction with an LEA, the motion becomes more consistent and more sinusoidal with increasing spring stiffness. This avoids some attractive features, such as variable compression ratio HCCI operation, but aids in reducing cycle-to-cycle variation for conventional combustion modes. To understand the cycle-to-cycle variations, we have developed a comprehensive model of an LEA with a 1kW target power in MATLAB®/Simulink, and an LEA corresponding to that model has been operated in the laboratory. This MATLAB®/Simulink numerical model has been used to examine the sensitivity of the LEA dynamics and performance parameters to changes in the design and operating inputs. The sensitivity analysis provides insight into the pathway for improving and optimizing the design, as well as an assessment of the effects of modeling assumptions on the reliability of predictions. A difficulty during the modeling is associated with the cycle-to-cycle energy balance for the LEA, and it is clear that this difficulty is reflected in real-world LEA control. If the alternator consumes more energy in a cycle than the engine provides, the system moves towards a stall. If the alternator consumes less energy, then the stroke, compression ratio and maximum translator velocity must rise steadily from cycle-to-cycle until efficiency losses curb the increase. The authors have recognized that the control of this energy balance in the model affects sensitivity analysis and must, therefore, mimic the real world intended control methodology. To understand the LEA behavior further, a control methodology was developed based on the basic feedback control systems in order to monitor the compression ratio of the single cylinder LEA system from cycle-to-cycle, with a view of keeping compression ratio substantially constant. Initially, the LEA system behavior was analyzed with and without the external controller, mainly to highlight the importance and need for an external control methodology. Further, two different control strategies were implemented and investigated. Finally, the cycle-to-cycle variations were studied as spring stiffness increased, by introducing combustion stochastics. With the proposed controller strategies and the addition of stiff springs, the cycle-to-cycle variations were reduced, and the LEA system operated steadily.
Bade, Mehar, Clark, Nigel, Famouri, Parviz, Guggilapu, PriyaankaDevi, Darzi, Mahdi, Johnson, Derek
Benchmarking a 2018 Toyota Camry 2.5-Liter Atkinson Cycle Engine with Cooled-EGR2019-01-02494/2/2019
As part of the U.S. Environmental Protection Agency’s (EPA’s) continuing assessment of advanced light-duty automotive technologies in support of regulatory and compliance programs, a 2018 Toyota Camry A25A-FKS 4-cylinder, 2.5-liter, naturally aspirated, Atkinson Cycle engine with cooled exhaust gas recirculation (cEGR) was benchmarked. The engine was tested on an engine dynamometer with and without its 8-speed automatic transmission, and with the engine wiring harness tethered to a complete vehicle parked outside of the test cell. Engine and transmission torque, fuel flow, key engine temperatures and pressures, onboard diagnostics (OBD) data, and Controller Area Network (CAN) bus data were recorded. This paper documents the test results under idle, low, medium, and high load engine operation. Motoring torque, wide open throttle (WOT) torque and fuel consumption are measured during transient operation using both EPA Tier 2 and Tier 3 test fuels. The design and performance of this 2018 2.5-liter engine is described and compared to Toyota’s published data and to EPA’s previous projections of the efficiency of an Atkinson Cycle engine with cEGR. The Brake Thermal Efficiency (BTE) map for the Toyota A25A-FKS engine shows a peak efficiency near 40 percent, which is the highest value of any publicly available map for a non-hybrid production gasoline internal combustion (IC) engine designed to run on 91 RON fuel. Further improvement is possible by application of fixed discrete or full continuous cylinder deactivation, both of which are currently in production on other engines.
Kargul, John, Stuhldreher, Mark, Barba, Daniel, Schenk, Charles, Bohac, Stanislav, McDonald, Joseph, Dekraker, Paul, Alden, Josh
Combined Benefits of Variable Valve Actuation and Low-Pressure EGR on SI Engine Efficiency Part 1: Part Load2019-01-02414/2/2019
Modern spark ignited engines face multiple barriers to achieving higher thermal efficiency. This study investigated the potential of utilizing both continuously variable valve actuation (VVA) and low-pressure cooled exhaust gas recirculation (EGR) to improve engine thermal efficiency at part-load conditions. Six speed / load points were investigated on a 1.6 L turbocharged gasoline direct injection engine. A design of experiment (DoE) approach using the Box-Behnken surface response model was conducted. The DoE results revealed different brake specific fuel consumption (BSFC) responses to the valve phasing and the intake valve lift at different operating conditions. Further engine testing was carried out at each speed / load point to confirm the engine efficiency and combustion performance when targeting different valvetrain controls and EGR strategies. The results indicated that utilizing the VVA system could always reduce BSFC at the studied operating conditions. The BSFC reduction was attributed to reduced pumping and incomplete combustion losses. The reduction in losses was attributed to optimizing the amount of hot trapped residuals compared with the fixed valve configuration, and load control through valve phasing and lift and thus de-throttling the engine. The cooled EGR offered further BSFC reduction benefits from the perspective of reducing in-cylinder heat losses provided the combustion stability limit was not exceeded. Additionally, the EGR played an important role for cases where the hot trapped residuals decreased by large amount due to the reduced overlap and increased intake pressure requirement with reduced intake valve lift.
Wang, Yanyu, Conway, Graham, Chadwell, Chris
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