New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing n...New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing new fuels as bio-diesel are beneficial ways to overcome diesel engine issues.This numerical study focused on the effect of split injection strategies as well as swirl ratio(SR)on the biodiesel premixed charge compression ignition(PCCI)combustion process and the related emissions.In this regard,KIVA-3V code as a CFD tool has been utilized to analyze the combustion and emission characteristics of the diesel engine.Single and split injection strategies have been executed on biodiesel PCCI combustion and have been compared in order to probe and examine the injection strategies.The results show that in both strategies,advancing the injection timing can lower the combustion emission and improve the engine performance by optimizing the start of injection(SOI)as sweet spot value.Utilizing a high swirl ratio with the split injection strategy has a negative effect on overall combustion,emission,and performance in comparison with the single injection strategy.For multi-injection scheme,SOI=−35 ATDC,SR=1.1,and for single injection scheme,SOI=−40 ATDC,SR=1.1 are considered as optimum cases regarding minimum total exhaust emissions and highest performance.展开更多
Homogeneous charge compression ignition(HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NOx as well as soot emissions as it combines the compression ignition(CI) and spark ignition(...Homogeneous charge compression ignition(HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NOx as well as soot emissions as it combines the compression ignition(CI) and spark ignition(SI) engine features. In this work, a CI engine was simulated to work in HCCI mode and was analyzed to study the effect of induction induced swirl under varying speeds using three-zone extended coherent flame combustion model(ECFM-3Z, compression ignition) of STAR-CD. The analysis was done considering speed ranging from 800 to 1600 r/min and swirl ratios from 1 to 4. The present study reveals that ECFM-3Z model has well predicted the performance and emissions of CI engine in HCCI mode. The simulation predicts reduced in-cylinder pressures, temperatures, wall heat transfer losses, and piston work with increase in swirl ratio irrespective of engine speed. Also, simultaneous reduction in CO2 and NOx emissions is realized with higher engine speeds and swirl ratios. Low speeds and swirl ratios are favorable for low CO2 emissions. It is observed that increase in engine speed causes a marginal reduction in in-cylinder pressures and temperatures. Also, higher turbulent energy and velocity magnitude levels are obtained with increase in swirl ratio, indicating efficient combustion necessitating no modifications in combustion chamber design. The investigations reveal a total decrease of 38.68% in CO2 emissions and 12.93% in NOx emissions when the engine speed increases from 800 to 1600 r/min at swirl ratio of 4. Also an increase of 14.16% in net work done is obtained with engine speed increasing from 800 to 1600 r/min at swirl ratio of 1. The simulation indicates that there is a tradeoff observed between the emissions and piston work. It is finally concluded that the HCCI combustion can be regarded as low temperature combustion as there is significant decrease in in-cylinder temperatures and pressures at higher speeds and higher swirl ratios.展开更多
文摘New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing new fuels as bio-diesel are beneficial ways to overcome diesel engine issues.This numerical study focused on the effect of split injection strategies as well as swirl ratio(SR)on the biodiesel premixed charge compression ignition(PCCI)combustion process and the related emissions.In this regard,KIVA-3V code as a CFD tool has been utilized to analyze the combustion and emission characteristics of the diesel engine.Single and split injection strategies have been executed on biodiesel PCCI combustion and have been compared in order to probe and examine the injection strategies.The results show that in both strategies,advancing the injection timing can lower the combustion emission and improve the engine performance by optimizing the start of injection(SOI)as sweet spot value.Utilizing a high swirl ratio with the split injection strategy has a negative effect on overall combustion,emission,and performance in comparison with the single injection strategy.For multi-injection scheme,SOI=−35 ATDC,SR=1.1,and for single injection scheme,SOI=−40 ATDC,SR=1.1 are considered as optimum cases regarding minimum total exhaust emissions and highest performance.
文摘Homogeneous charge compression ignition(HCCI) mode of combustion is popularly known for achieving simultaneous reduction of NOx as well as soot emissions as it combines the compression ignition(CI) and spark ignition(SI) engine features. In this work, a CI engine was simulated to work in HCCI mode and was analyzed to study the effect of induction induced swirl under varying speeds using three-zone extended coherent flame combustion model(ECFM-3Z, compression ignition) of STAR-CD. The analysis was done considering speed ranging from 800 to 1600 r/min and swirl ratios from 1 to 4. The present study reveals that ECFM-3Z model has well predicted the performance and emissions of CI engine in HCCI mode. The simulation predicts reduced in-cylinder pressures, temperatures, wall heat transfer losses, and piston work with increase in swirl ratio irrespective of engine speed. Also, simultaneous reduction in CO2 and NOx emissions is realized with higher engine speeds and swirl ratios. Low speeds and swirl ratios are favorable for low CO2 emissions. It is observed that increase in engine speed causes a marginal reduction in in-cylinder pressures and temperatures. Also, higher turbulent energy and velocity magnitude levels are obtained with increase in swirl ratio, indicating efficient combustion necessitating no modifications in combustion chamber design. The investigations reveal a total decrease of 38.68% in CO2 emissions and 12.93% in NOx emissions when the engine speed increases from 800 to 1600 r/min at swirl ratio of 4. Also an increase of 14.16% in net work done is obtained with engine speed increasing from 800 to 1600 r/min at swirl ratio of 1. The simulation indicates that there is a tradeoff observed between the emissions and piston work. It is finally concluded that the HCCI combustion can be regarded as low temperature combustion as there is significant decrease in in-cylinder temperatures and pressures at higher speeds and higher swirl ratios.
