Praveen Kumar, Xin Yu, Anqi Zhang, Andrew Baur, Nayan Engineer, David Roth
Turbocharged spark-ignition (SI) engines, owing to frequent engine knocking events, utilize retarded spark timing that causes combustion inefficiency, and high turbine inlet temperature (Trb-In T) levels. Fuel enrichment is implemented at high power levels to prevent excessive Trb-In T levels, resulting in an additional fueling penalty and higher CO emissions. In current times, fuel-enrichment reductions are of high strategic importance for engine manufacturers to meet the imminent emissions regulations. To that end, the authors investigated the divided exhaust period (DEP) concept in a 2.2 L turbocharged SI engine with a geometric compression ratio of 14 by decoupling blowdown (BD) and scavenge (SC) events during the exhaust process. Using a validated 1D engine model, the authors first analyzed the DEP concept in terms of pumping mean effective pressure (PMEP) and engine knocking (KI) reduction. Subsequently, the authors examined the effectiveness of the DEP concept using a “low-restriction exhaust flowpath” and varying late intake valve closing (LIVC) duration.
First, using DEP, significant PMEP and KI reductions benefits were observed at high power engine conditions along with a large increase in Trb-In T from the early blowdown event. Subsequently, use of a low restriction exhaust flowpath and a shortened LIVC duration further elevated the DEP benefits, including Trb-In T reduction that facilitated enrichment reduction. At 4,000 RPM/20 bar BMEP, ~70% lower PMEP and a 2.2 point increase in ITEg were noted relative to the base engine. However, the 2,000 RPM peak torque engine condition was compromised using DEP, due to knock limitation and deteriorated stock turbocharger performance. Finally, DEP design integrated with an off-the-shelf (new) turbocharger system remedied the low-end torque challenges and demonstrated a notable enrichment reduction and thermal efficiency benefits at the full load engine curve including the 200 kW rated condition.
{"title":"Divided Exhaust Period Assessment for Fuel-Enrichment Reduction in Turbocharged Spark-Ignition Engines","authors":"Praveen Kumar, Xin Yu, Anqi Zhang, Andrew Baur, Nayan Engineer, David Roth","doi":"10.4271/03-17-03-0022","DOIUrl":"https://doi.org/10.4271/03-17-03-0022","url":null,"abstract":"<div>Turbocharged spark-ignition (SI) engines, owing to frequent engine knocking events, utilize retarded spark timing that causes combustion inefficiency, and high turbine inlet temperature (Trb-In T) levels. Fuel enrichment is implemented at high power levels to prevent excessive Trb-In T levels, resulting in an additional fueling penalty and higher CO emissions. In current times, fuel-enrichment reductions are of high strategic importance for engine manufacturers to meet the imminent emissions regulations. To that end, the authors investigated the divided exhaust period (DEP) concept in a 2.2 L turbocharged SI engine with a geometric compression ratio of 14 by decoupling blowdown (BD) and scavenge (SC) events during the exhaust process. Using a validated 1D engine model, the authors first analyzed the DEP concept in terms of pumping mean effective pressure (PMEP) and engine knocking (KI) reduction. Subsequently, the authors examined the effectiveness of the DEP concept using a “low-restriction exhaust flowpath” and varying late intake valve closing (LIVC) duration.</div> <div>First, using DEP, significant PMEP and KI reductions benefits were observed at high power engine conditions along with a large increase in Trb-In T from the early blowdown event. Subsequently, use of a low restriction exhaust flowpath and a shortened LIVC duration further elevated the DEP benefits, including Trb-In T reduction that facilitated enrichment reduction. At 4,000 RPM/20 bar BMEP, ~70% lower PMEP and a 2.2 point increase in ITEg were noted relative to the base engine. However, the 2,000 RPM peak torque engine condition was compromised using DEP, due to knock limitation and deteriorated stock turbocharger performance. Finally, DEP design integrated with an off-the-shelf (new) turbocharger system remedied the low-end torque challenges and demonstrated a notable enrichment reduction and thermal efficiency benefits at the full load engine curve including the 200 kW rated condition.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134906878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates the behavior of pre-chamber knock in comparison to traditional spark ignition engine knock, using a modified constant-volume gasoline engine with an optically accessible piston. The aim is to provide a deeper understanding of pre-chamber knock combustion and its potential for mitigating knock. Five passive pre-chambers with different nozzle diameters, volumes, and nozzle numbers were tested, and nitrogen dilution was varied from 0% to 10%. The stochastic nature of knock behavior necessitates the use of statistical methods, leading to the proposal of a high-frequency band-pass filter (37–43 kHz) as an alternative pre-chamber knock metric. Pre-chamber knock combustion was found to exhibit fewer strong knock cycles compared to SI engines, indicating its potential for mitigating knock intensity. High-speed images revealed pre-chamber knock primarily occurs near the liner, where end-gas knock is typically exhibited. The study identified that increasing pre-chamber nozzle diameter resulted in a larger dispersion of knock cycles and more severe knock intensity, likely due to shorter jet penetration depth requiring more time for end-gas consumption. Strategies for mitigating knock in pre-chamber combustion systems include reducing the pre-chamber volume for a fixed A/V ratio and increasing dilution level. The results of this study offer valuable insights for developing effective knock mitigation approaches in pre-chamber combustion systems, contributing to the advancement of more efficient and reliable engines.
{"title":"Visualization and Statistical Analysis of Passive Pre-chamber Knock in a Constant-volume Optical Engine","authors":"Dong Eun Lee, Xin Yu, Andrew Baur, Li Qiao","doi":"10.4271/03-17-03-0020","DOIUrl":"https://doi.org/10.4271/03-17-03-0020","url":null,"abstract":"<div>This study investigates the behavior of pre-chamber knock in comparison to traditional spark ignition engine knock, using a modified constant-volume gasoline engine with an optically accessible piston. The aim is to provide a deeper understanding of pre-chamber knock combustion and its potential for mitigating knock. Five passive pre-chambers with different nozzle diameters, volumes, and nozzle numbers were tested, and nitrogen dilution was varied from 0% to 10%. The stochastic nature of knock behavior necessitates the use of statistical methods, leading to the proposal of a high-frequency band-pass filter (37–43 kHz) as an alternative pre-chamber knock metric. Pre-chamber knock combustion was found to exhibit fewer strong knock cycles compared to SI engines, indicating its potential for mitigating knock intensity. High-speed images revealed pre-chamber knock primarily occurs near the liner, where end-gas knock is typically exhibited. The study identified that increasing pre-chamber nozzle diameter resulted in a larger dispersion of knock cycles and more severe knock intensity, likely due to shorter jet penetration depth requiring more time for end-gas consumption. Strategies for mitigating knock in pre-chamber combustion systems include reducing the pre-chamber volume for a fixed A/V ratio and increasing dilution level. The results of this study offer valuable insights for developing effective knock mitigation approaches in pre-chamber combustion systems, contributing to the advancement of more efficient and reliable engines.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135618185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using two subgrid-scale models of Smagorinsky and its dynamic version, large eddy simulation (LES) approach is applied to develop a 3D computer code simulating the in-cylinder flow during intake and compression strokes in an engine geometry consisting of a pancake-shaped piston with a fixed valve. The results are compared with corresponding experimental data and a standard K-Ɛ turbulence model. LES results generally show better agreement with available experimental data suggesting that LES with dynamic subgrid-scale model is more effective method for accurately predicting the in-cylinder flow field. Representative Fiat engine equipped with moving valve and piston bowl is analyzed as the second case to assess the capability of the method to handle complex geometries and impacts of geometrical parameters such as shape and position of piston bowl together with swirling intake flow pattern on both turbulent structure of in-cylinder flow and engine performance using dynamic version of LES approach over a curvilinear computational meshed geometry. Results indicate that presence of piston bowl leads to eye-catching increment in both turbulent kinematic energy and tumble ratio amounts at the end of compression stroke by around 29% and 33%, respectively. The optimum swirl ratio found to be 4, leading to 67.9% increment in pre-injection turbulent kinetic energy in comparison with non-swirl pattern, whereas 20% eccentricity of cylinder bowl just led to 2% improvement in the pre-injection turbulent kinetic energy, which is not recommended due to small impact compared to noticeable manufacturing expenditures.
{"title":"Numerical Simulation of Turbulent Structures Inside Internal Combustion Engines Using Large Eddy Simulation Method","authors":"Negin Aghamohamadi, Hassan Khaleghi, Majid Razaghi","doi":"10.4271/03-17-02-0011","DOIUrl":"https://doi.org/10.4271/03-17-02-0011","url":null,"abstract":"<div>Using two subgrid-scale models of Smagorinsky and its dynamic version, large eddy simulation (LES) approach is applied to develop a 3D computer code simulating the in-cylinder flow during intake and compression strokes in an engine geometry consisting of a pancake-shaped piston with a fixed valve. The results are compared with corresponding experimental data and a standard K-Ɛ turbulence model. LES results generally show better agreement with available experimental data suggesting that LES with dynamic subgrid-scale model is more effective method for accurately predicting the in-cylinder flow field. Representative Fiat engine equipped with moving valve and piston bowl is analyzed as the second case to assess the capability of the method to handle complex geometries and impacts of geometrical parameters such as shape and position of piston bowl together with swirling intake flow pattern on both turbulent structure of in-cylinder flow and engine performance using dynamic version of LES approach over a curvilinear computational meshed geometry. Results indicate that presence of piston bowl leads to eye-catching increment in both turbulent kinematic energy and tumble ratio amounts at the end of compression stroke by around 29% and 33%, respectively. The optimum swirl ratio found to be 4, leading to 67.9% increment in pre-injection turbulent kinetic energy in comparison with non-swirl pattern, whereas 20% eccentricity of cylinder bowl just led to 2% improvement in the pre-injection turbulent kinetic energy, which is not recommended due to small impact compared to noticeable manufacturing expenditures.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136143058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Marietta Markiewicz, Łukasz Muślewski, Michał Pająk
The European Union’s pro-ecological policy imposes a requirement to use biofuel additives in diesel fuel which is supposed to support the sustainable development of transport and limit its negative impact on the natural environment. The study presents an analysis of the exhaust gas components and the amount of solid particles carried out for internal combustion engines fueled with mixtures of diesel fuel and fatty acid methyl esters. Additionally, the computer software of the tested power units was modified by changing the amount of fuel to be supplied and the air intake. The goal of the tests was to find out how the fuel mixture and reprogramming of the computer control systems would impact the emission of exhaust gas components. Based on the tests, it was found that an additive of fatty acid methyl esters to diesel does have an influence on the tested unit parameters. The highest values were found for a mixture containing 90% diesel fuel and 10% fatty acid methyl esters, whereas the lowest ones were for a mixture composed of 50% diesel fuel and 50% fatty acid methyl esters.
{"title":"Impact Level of Selected Fuel Mixtures on the Natural Environment","authors":"Marietta Markiewicz, Łukasz Muślewski, Michał Pająk","doi":"10.4271/03-16-08-0056","DOIUrl":"https://doi.org/10.4271/03-16-08-0056","url":null,"abstract":"<div>The European Union’s pro-ecological policy imposes a requirement to use biofuel additives in diesel fuel which is supposed to support the sustainable development of transport and limit its negative impact on the natural environment. The study presents an analysis of the exhaust gas components and the amount of solid particles carried out for internal combustion engines fueled with mixtures of diesel fuel and fatty acid methyl esters. Additionally, the computer software of the tested power units was modified by changing the amount of fuel to be supplied and the air intake. The goal of the tests was to find out how the fuel mixture and reprogramming of the computer control systems would impact the emission of exhaust gas components. Based on the tests, it was found that an additive of fatty acid methyl esters to diesel does have an influence on the tested unit parameters. The highest values were found for a mixture containing 90% diesel fuel and 10% fatty acid methyl esters, whereas the lowest ones were for a mixture composed of 50% diesel fuel and 50% fatty acid methyl esters.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135918803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An analytical method for nonlinear three-dimensional (3D) multi-body flexible dynamic time-domain analysis for a single-cylinder internal combustion (IC) engine consisting of piston, connecting rod, crank pin, and liner is developed. This piston is modeled as a 3D piston that collides with the liner as in a real engine. The goal is to investigate the piston slap force and subsequent liner vibration. Liner vibrational velocity is directly responsible for pressure fluctuations in the coolant region resulting in bubble formation and subsequent collapse. If the bubble collapse is closer to the liner surface, cavitation erosion in the liner might occur. The mechanism of liner cavitation is briefly explained, which would take a full computational fluid dynamics (CFD) model to develop, which is out of scope for the present work. However, as a first step, the present method focused on a comprehensive and accurate estimation of the highest inward and outward liner velocities, which are directly related to the bubble formation and collapse, respectively. Sensitivity of liner velocity to different engine-operating conditions (warm and hot, with highest skirt temperatures of 178 and 130°C), piston pin bore offsets (thrust side, anti-thrust side directions in the amounts of 0.6 mm, and the nominal no offset case), and liner thicknesses are determined. Piston thermal growth is considered as part of the analysis resulting in interference condition between piston skirt and liner under the hot operating condition and low minimum clearance under the warm condition. Correlation of liner velocity contour plots with real engine liner cavitation erosion is presented. Analytical model showed a maximum liner inward velocity of 55 mm/s with no piston pin offset under nominal engine-operating configuration. A correlation has been found between location of this highest liner velocity and location of the actual cavitation erosion in the field.
{"title":"Cylinder Liner Velocity Calculation under Dynamic Condition in the Pursuit of Liner Cavitation Investigation of an Internal Combustion Engine","authors":"Sanjib Chowdhury","doi":"10.4271/03-17-03-0017","DOIUrl":"https://doi.org/10.4271/03-17-03-0017","url":null,"abstract":"<div>An analytical method for nonlinear three-dimensional (3D) multi-body flexible dynamic time-domain analysis for a single-cylinder internal combustion (IC) engine consisting of piston, connecting rod, crank pin, and liner is developed. This piston is modeled as a 3D piston that collides with the liner as in a real engine. The goal is to investigate the piston slap force and subsequent liner vibration. Liner vibrational velocity is directly responsible for pressure fluctuations in the coolant region resulting in bubble formation and subsequent collapse. If the bubble collapse is closer to the liner surface, cavitation erosion in the liner might occur. The mechanism of liner cavitation is briefly explained, which would take a full computational fluid dynamics (CFD) model to develop, which is out of scope for the present work. However, as a first step, the present method focused on a comprehensive and accurate estimation of the highest inward and outward liner velocities, which are directly related to the bubble formation and collapse, respectively. Sensitivity of liner velocity to different engine-operating conditions (warm and hot, with highest skirt temperatures of 178 and 130°C), piston pin bore offsets (thrust side, anti-thrust side directions in the amounts of 0.6 mm, and the nominal no offset case), and liner thicknesses are determined. Piston thermal growth is considered as part of the analysis resulting in interference condition between piston skirt and liner under the hot operating condition and low minimum clearance under the warm condition. Correlation of liner velocity contour plots with real engine liner cavitation erosion is presented. Analytical model showed a maximum liner inward velocity of 55 mm/s with no piston pin offset under nominal engine-operating configuration. A correlation has been found between location of this highest liner velocity and location of the actual cavitation erosion in the field.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136058489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Edoardo De Renzis, Valerio Mariani, Gian Marco Bianchi, Giulio Cazzoli, Stefania Falfari
Due to the incoming phase out of fossil fuels from the market in order to reduce the carbon footprint of the automotive sector, hydrogen-fueled engines are candidate mid-term solution. Thanks to its properties, hydrogen promotes flames that poorly suffer from the quenching effects toward the engine walls. Thus, emphasis must be posed on the heat-up of the oil layer that wets the cylinder liner in hydrogen-fueled engines. It is known that motor oils are complex mixtures of a number of mainly heavy hydrocarbons (HCs); however, their composition is not known a priori. Simulation tools that can support the early development steps of those engines must be provided with oil composition and properties at operation-like conditions. The authors propose a statistical inference-based optimization approach for identifying oil surrogate multicomponent mixtures. The algorithm is implemented in Python and relies on the Bayesian optimization technique. As a benchmark, the surrogate for the SAE5W30 commercial multigrade oil has been determined. Then, this multicomponent surrogate and a SAE5W30 pseudo-pure are compared by means of an oil film model, which accounts for oil heat exchange with the cylinder wall and the gases from hydrogen combustion, and its evaporation. The results in terms of oil film temperature, viscosity, and thickness under hydrogen-engine boundaries are evaluated. Analyses reveal that the optimized multicomponent mixture behavior is more realistic and can outperform the pseudo-pure approach when the oil phase change and the oil-in-cylinder presence must be considered.
{"title":"A Numerical Methodology to Test the Lubricant Oil Evaporation and Its Thermal Management-Related Properties Derating in Hydrogen-Fueled Engines","authors":"Edoardo De Renzis, Valerio Mariani, Gian Marco Bianchi, Giulio Cazzoli, Stefania Falfari","doi":"10.4271/03-17-02-0015","DOIUrl":"https://doi.org/10.4271/03-17-02-0015","url":null,"abstract":"<div>Due to the incoming phase out of fossil fuels from the market in order to reduce the carbon footprint of the automotive sector, hydrogen-fueled engines are candidate mid-term solution. Thanks to its properties, hydrogen promotes flames that poorly suffer from the quenching effects toward the engine walls. Thus, emphasis must be posed on the heat-up of the oil layer that wets the cylinder liner in hydrogen-fueled engines. It is known that motor oils are complex mixtures of a number of mainly heavy hydrocarbons (HCs); however, their composition is not known a priori. Simulation tools that can support the early development steps of those engines must be provided with oil composition and properties at operation-like conditions. The authors propose a statistical inference-based optimization approach for identifying oil surrogate multicomponent mixtures. The algorithm is implemented in Python and relies on the Bayesian optimization technique. As a benchmark, the surrogate for the SAE5W30 commercial multigrade oil has been determined. Then, this multicomponent surrogate and a SAE5W30 pseudo-pure are compared by means of an oil film model, which accounts for oil heat exchange with the cylinder wall and the gases from hydrogen combustion, and its evaporation. The results in terms of oil film temperature, viscosity, and thickness under hydrogen-engine boundaries are evaluated. Analyses reveal that the optimized multicomponent mixture behavior is more realistic and can outperform the pseudo-pure approach when the oil phase change and the oil-in-cylinder presence must be considered.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135394354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dong Eun Lee, Claudia Iyer, Steven Wooldridge, Li Qiao, Jianwen J. Yi
Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance. Utilizing a modified constant-volume gasoline direct injection engine with an optically accessible piston, we tested three passive pre-chambers with nozzle diameters of 1.2, 1.4, and 1.6 mm, while nitrogen dilution varied from 0 to 20%. With the help of high-speed imaging, we captured pre-chamber jet formations and subsequent flame propagation within the main chamber. Our novel findings reveal that asymmetric temporal and spatial jet formation patterns arising from pre-chambers significantly impact engine performance. The larger-nozzle-diameter pre-chambers exhibited the least variation in jet formation due to their improved scavenging and main mixture filling processes, but had the slowest jet velocity and lowest jet penetration depth. At no dilution condition, the 1.2 mm-PC demonstrated superior performance attributed to higher pressure build-up in the pre-chamber, resulting in accelerated jet velocity and increased jet penetration depth. However, at high dilution condition, the 1.6 mm-PC performed better, highlighting the importance of scavenging and symmetry jet formation. This study emphasizes the importance of carefully selecting the pre-chamber nozzle diameter, based on the engine’s operating conditions, to achieve an optimal and balanced configuration that can improve both jet formation and jet characteristics, as well as scavenging.
{"title":"Impact of Passive Pre-Chamber Nozzle Diameter on Jet Formation Patterns and Dilution Tolerance in a Constant-Volume Optical Engine","authors":"Dong Eun Lee, Claudia Iyer, Steven Wooldridge, Li Qiao, Jianwen J. Yi","doi":"10.4271/03-17-02-0013","DOIUrl":"https://doi.org/10.4271/03-17-02-0013","url":null,"abstract":"<div>Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance. Utilizing a modified constant-volume gasoline direct injection engine with an optically accessible piston, we tested three passive pre-chambers with nozzle diameters of 1.2, 1.4, and 1.6 mm, while nitrogen dilution varied from 0 to 20%. With the help of high-speed imaging, we captured pre-chamber jet formations and subsequent flame propagation within the main chamber. Our novel findings reveal that asymmetric temporal and spatial jet formation patterns arising from pre-chambers significantly impact engine performance. The larger-nozzle-diameter pre-chambers exhibited the least variation in jet formation due to their improved scavenging and main mixture filling processes, but had the slowest jet velocity and lowest jet penetration depth. At no dilution condition, the 1.2 mm-PC demonstrated superior performance attributed to higher pressure build-up in the pre-chamber, resulting in accelerated jet velocity and increased jet penetration depth. However, at high dilution condition, the 1.6 mm-PC performed better, highlighting the importance of scavenging and symmetry jet formation. This study emphasizes the importance of carefully selecting the pre-chamber nozzle diameter, based on the engine’s operating conditions, to achieve an optimal and balanced configuration that can improve both jet formation and jet characteristics, as well as scavenging.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136070930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Leonardo Pulga, Claudio Forte, Alfio Siliato, Emanuele Giovannardi, Roberto Tonelli, Ioannis Kitsopanidis, Gian Marco Bianchi
The use of data-driven algorithms for the integration or substitution of current production sensors is becoming a consolidated trend in research and development in the automotive field. Due to the large number of variables and scenarios to consider; however, it is of paramount importance to define a consistent methodology accounting for uncertainty evaluations and preprocessing steps, that are often overlooked in naïve implementations. Among the potential applications, the use of virtual sensors for the analysis of solid emissions in transient cycles is particularly appealing for industrial applications, considering the new legislations scenario and the fact that, to our best knowledge, no robust models have been previously developed. In the present work, the authors present a detailed overview of the problematics arising in the development of a virtual sensor, with particular focus on the transient particulate number (diameter <10 nm) emissions, overcome by leveraging data-driven algorithms and a profound knowledge of the underlying physical limitations. The workflow has been tested and validated using a complete dataset composed of more than 30 full driving cycles obtained from industrial experimentations, underlying the importance of each step and its possible variations. The final results show that a reliable model for transient particulate number emissions is possible and the accuracy reached is compatible with the intrinsic cycle to cycle variability of the phenomenon, while ensuring control over the quality of the predicted values, in order to provide valuable insight for the actions to perform.
{"title":"Artificial Intelligence Strategies for the Development of Robust Virtual Sensors: An Industrial Case for Transient Particle Emissions in a High-Performance Engine","authors":"Leonardo Pulga, Claudio Forte, Alfio Siliato, Emanuele Giovannardi, Roberto Tonelli, Ioannis Kitsopanidis, Gian Marco Bianchi","doi":"10.4271/03-17-02-0014","DOIUrl":"https://doi.org/10.4271/03-17-02-0014","url":null,"abstract":"<div>The use of data-driven algorithms for the integration or substitution of current production sensors is becoming a consolidated trend in research and development in the automotive field. Due to the large number of variables and scenarios to consider; however, it is of paramount importance to define a consistent methodology accounting for uncertainty evaluations and preprocessing steps, that are often overlooked in naïve implementations. Among the potential applications, the use of virtual sensors for the analysis of solid emissions in transient cycles is particularly appealing for industrial applications, considering the new legislations scenario and the fact that, to our best knowledge, no robust models have been previously developed. In the present work, the authors present a detailed overview of the problematics arising in the development of a virtual sensor, with particular focus on the transient particulate number (diameter &lt;10 nm) emissions, overcome by leveraging data-driven algorithms and a profound knowledge of the underlying physical limitations. The workflow has been tested and validated using a complete dataset composed of more than 30 full driving cycles obtained from industrial experimentations, underlying the importance of each step and its possible variations. The final results show that a reliable model for transient particulate number emissions is possible and the accuracy reached is compatible with the intrinsic cycle to cycle variability of the phenomenon, while ensuring control over the quality of the predicted values, in order to provide valuable insight for the actions to perform.</div>","PeriodicalId":47948,"journal":{"name":"SAE International Journal of Engines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136363707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xin Yu, Vincent Costanzo, Elana Chapman, Richard Davis
To have a more complete understanding of the fuel effects on each subsequent stage of a stochastic preignition event in a spark-ignition engine and to build on the previous work of understanding the propensity of fuel to initiate and sustain a preignition flame, this work is focused on examining the role of fuel on the onset of knock and the intensity of superknock once the unburned mixture reaches certain conditions ahead of the preignition flame. Using a “skip advance” spark test method to simulate preignition flames initiated at different cylinder conditions, more than 20 single- and multicomponent fuels were ranked based on the condition required to reach the onset of knock (the start of end-gas autoignition) and the condition that leads to severe superknock intensities. It was found that average knock intensity can be mainly explained by the unburn mixture fraction and the thermodynamic condition of the unburned mixture and, not surprisingly, that the fuel ranking for the onset of knock and superknock based on average knock intensity is correlated to octane index. However, outlier cycles with extremely high knock intensities cannot be fully explained by the average cycle behavior. More interestingly, different fuels exhibit different superknock characteristics. Some fuels, such as toluene, have fewer extreme cycles once the same average knock intensity condition is reached, whereas other fuels, such as ethanol, have more extreme cycles that tend to break engine hardware in a single cycle event. A preliminary study based on the modes of reaction front propagation show that fuels with low-temperature heat release and negative temperature coefficient (NTC) behavior can lead to a higher propensity to produce extreme knock intensities when coupled with the right in-cylinder pressure wave.
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