Gasoline compression ignition(GCI)has been considered as a promising combustion concept to yield ultralow NOX and soot emissions while maintaining high thermal efficiency.However,how to improve the low-load performanc...Gasoline compression ignition(GCI)has been considered as a promising combustion concept to yield ultralow NOX and soot emissions while maintaining high thermal efficiency.However,how to improve the low-load performance becomes an urgent issue to be solved.In this paper,a GCI engine model was built to investigate the effects of internal EGR(i-EGR)and pre-injection on in-cylinder temperature,spatial concentration of mixture and OH radical,combustion and emission characteristics,and the control strategy for improving the combustion performance was further explored.The results showed an obvious expansion of the zone with an equivalence ratio between 0.8∼1.2 is realized by higher pre-injection ratios,and the s decreases with the increase of pre-injection ratio,but increases with the increase of i-EGR ratio.The high overlap among the equivalentmixture zone,the hightemperature zone,and the OH radical-rich zone can be achieved by higher i-EGR ratio coupled with higher preinjection ratio.By increasing the pre-injection ratio,the combustion efficiency increases first and then decreases,also achieves the peak value with a pre-injection ratio of 60%and is unaffected by i-EGR.The emissions of CO,HC,NOX,and soot can also be reduced to low levels by the combination of higher i-EGR ratios and a pre-injection ratio of 60%.展开更多
Gasoline compression ignition(GCI) is a practicable way to obtain low emissions and high thermal efficiency of gasoline-like fuels in internal combustion engines. In this paper, the research octane number(RON) and inj...Gasoline compression ignition(GCI) is a practicable way to obtain low emissions and high thermal efficiency of gasoline-like fuels in internal combustion engines. In this paper, the research octane number(RON) and injection strategy were coordinated to optimize the GCI engine performance and emissions under high loads. The direct injection and port injection were used to achieve two injection strategies: direct injection(DI) and port injection plus direct injection(PIDI), and the primary reference fuels(PRF) with the RON of 60, 70, 80 and 90 were used. The results show that using lower RON fuels under high loads, DI mode can achieve higher efficiency, while PIDI mode can achieve lower combustion noise at an expense of slightly lower fuel economy. When the DI mode is converted to PIDI mode with a pre-injection ratio of 30%, using PRF70 under 12 bar and the exhaust gas recirculation(EGR) rate of 40%, the gross indicated thermal efficiency and the maximum pressure rise rate are reduced by 1% and by 2 bar/°CA, respectively, while the particle emissions also decrease significantly, thus achieving low emissions and high efficiency. However, under the same load and EGR rate, DI mode produces less regulated and unregulated emissions than PIDI mode. In addition, the effect of fuel RON was obvious, the lower RON fuels exhibit obvious three-stage heat release in PIDI mode, however, PRF90 with higher RON only exhibits two-stage heat release, and the peak value of the firststage heat release rate is also lower than those of other fuels.展开更多
Gasoline direct injection(GDI)engines are currently the dominant powertrains for passenger cars.With the implementation of increasingly stringent fuel consumption and emission regulationsworldwide,GDI engines are faci...Gasoline direct injection(GDI)engines are currently the dominant powertrains for passenger cars.With the implementation of increasingly stringent fuel consumption and emission regulationsworldwide,GDI engines are facing challenges owing to high particulate matter emissions and a tendency to knock,leading to a change in the research and design(R&D)issues compared with those in the twentieth century.This paper reviews the progress in research regarding GDI engine technologies over the past 20 years,focusing on combustion system configurations,and also highlights common issues in GDI R&D,including pre-ignition and deto-knock,soot formation and PM emissions,injector deposits and gasoline compression ignition(GCI).First,an overview of recent developments in the field as driven by regulations is provided,following which progress in injection and combustion systems is examined.Third,the review addresses the occurrence and mechanism of deto-knock and considers means of suppressing this phenomenon.The fourth section discusses soot formation mechanisms and particulate matter emission characteristics of GDI engines and describes the application of gasoline particulate filter(GPF)after-treatment.The subsequent section summarizes studies regarding injector deposit formation,as well as pioneering research into GCI combustion modes.Finally,a summary and future prospects for GDI engine technologies are provided.展开更多
Gasoline compression ignition(GCI)combustion faces problems such as high maximum pressure rise rate(MPRR)and combustion deterioration at high loads.This paper aims to improve the engine performance of the GCI mode by ...Gasoline compression ignition(GCI)combustion faces problems such as high maximum pressure rise rate(MPRR)and combustion deterioration at high loads.This paper aims to improve the engine performance of the GCI mode by regulating concentration stratification and promoting fuel-gas mixing by utilizing the double main-injection(DMI)strategy.Two direct injectors simultaneously injected gasoline with an octane number of 82.7 to investigate the energy ratio between the two main-injection and exhaust gas recirculation(EGR)on combustion and emissions.High-load experiments were conducted using the DMI strategy and compared with the single main-injection(SMI)strategy and conventional diesel combustion.The results indicate that the DMI strategy have a great potential to reduce the MPRR and improve the fuel economy of the GCI mode.At a 10 bar indicated mean effective pressure,increasing the main-injection-2 ratio(Rm-2)shortens the injection duration and increases the mean mixing time.Optimized Rm-2 could moderate the trade-off between the MPRR and the indicated specific fuel consumption with both reductions.An appropriate EGR should be adopted considering combustion and emissions.The DMI strategy achieves a highly efficient and stable combustion at high loads,with an indicated thermal efficiency(ITE)greater than 48%,CO and THC emissions at low levels,and MPRR within a reasonable range.Compared with the SMI strategy,the maximum improvement of the ITE is 1.5%,and the maximum reduction of MPRR is 1.5 bar/°CA.展开更多
基金sponsored by the projects of National Natural Science Foundation of China (Grant Nos.51806127 and 52075307)Key Research and Development Program of Shandong Province (Grant No.2019GHZ016).
文摘Gasoline compression ignition(GCI)has been considered as a promising combustion concept to yield ultralow NOX and soot emissions while maintaining high thermal efficiency.However,how to improve the low-load performance becomes an urgent issue to be solved.In this paper,a GCI engine model was built to investigate the effects of internal EGR(i-EGR)and pre-injection on in-cylinder temperature,spatial concentration of mixture and OH radical,combustion and emission characteristics,and the control strategy for improving the combustion performance was further explored.The results showed an obvious expansion of the zone with an equivalence ratio between 0.8∼1.2 is realized by higher pre-injection ratios,and the s decreases with the increase of pre-injection ratio,but increases with the increase of i-EGR ratio.The high overlap among the equivalentmixture zone,the hightemperature zone,and the OH radical-rich zone can be achieved by higher i-EGR ratio coupled with higher preinjection ratio.By increasing the pre-injection ratio,the combustion efficiency increases first and then decreases,also achieves the peak value with a pre-injection ratio of 60%and is unaffected by i-EGR.The emissions of CO,HC,NOX,and soot can also be reduced to low levels by the combination of higher i-EGR ratios and a pre-injection ratio of 60%.
基金supported by the National Natural Science Foundation of China(Grant Nos.51425602 and 51961135105)
文摘Gasoline compression ignition(GCI) is a practicable way to obtain low emissions and high thermal efficiency of gasoline-like fuels in internal combustion engines. In this paper, the research octane number(RON) and injection strategy were coordinated to optimize the GCI engine performance and emissions under high loads. The direct injection and port injection were used to achieve two injection strategies: direct injection(DI) and port injection plus direct injection(PIDI), and the primary reference fuels(PRF) with the RON of 60, 70, 80 and 90 were used. The results show that using lower RON fuels under high loads, DI mode can achieve higher efficiency, while PIDI mode can achieve lower combustion noise at an expense of slightly lower fuel economy. When the DI mode is converted to PIDI mode with a pre-injection ratio of 30%, using PRF70 under 12 bar and the exhaust gas recirculation(EGR) rate of 40%, the gross indicated thermal efficiency and the maximum pressure rise rate are reduced by 1% and by 2 bar/°CA, respectively, while the particle emissions also decrease significantly, thus achieving low emissions and high efficiency. However, under the same load and EGR rate, DI mode produces less regulated and unregulated emissions than PIDI mode. In addition, the effect of fuel RON was obvious, the lower RON fuels exhibit obvious three-stage heat release in PIDI mode, however, PRF90 with higher RON only exhibits two-stage heat release, and the peak value of the firststage heat release rate is also lower than those of other fuels.
基金The authors acknowledge theChina NationalNat-ural Science Foundation Project“Formation and Evolution of PM from GDI Engines:From Primary Particles to Secondary Aerosols”(Grant No.51636003)the National Key R&D Plan Project“Integration Technology of PM Capture and Clean Emissions for GDI Vehicles”(Grant No.2017YFC02110004).
文摘Gasoline direct injection(GDI)engines are currently the dominant powertrains for passenger cars.With the implementation of increasingly stringent fuel consumption and emission regulationsworldwide,GDI engines are facing challenges owing to high particulate matter emissions and a tendency to knock,leading to a change in the research and design(R&D)issues compared with those in the twentieth century.This paper reviews the progress in research regarding GDI engine technologies over the past 20 years,focusing on combustion system configurations,and also highlights common issues in GDI R&D,including pre-ignition and deto-knock,soot formation and PM emissions,injector deposits and gasoline compression ignition(GCI).First,an overview of recent developments in the field as driven by regulations is provided,following which progress in injection and combustion systems is examined.Third,the review addresses the occurrence and mechanism of deto-knock and considers means of suppressing this phenomenon.The fourth section discusses soot formation mechanisms and particulate matter emission characteristics of GDI engines and describes the application of gasoline particulate filter(GPF)after-treatment.The subsequent section summarizes studies regarding injector deposit formation,as well as pioneering research into GCI combustion modes.Finally,a summary and future prospects for GDI engine technologies are provided.
基金supported by the National Key R&D Program of China(Grant No.2022YFE0100100).
文摘Gasoline compression ignition(GCI)combustion faces problems such as high maximum pressure rise rate(MPRR)and combustion deterioration at high loads.This paper aims to improve the engine performance of the GCI mode by regulating concentration stratification and promoting fuel-gas mixing by utilizing the double main-injection(DMI)strategy.Two direct injectors simultaneously injected gasoline with an octane number of 82.7 to investigate the energy ratio between the two main-injection and exhaust gas recirculation(EGR)on combustion and emissions.High-load experiments were conducted using the DMI strategy and compared with the single main-injection(SMI)strategy and conventional diesel combustion.The results indicate that the DMI strategy have a great potential to reduce the MPRR and improve the fuel economy of the GCI mode.At a 10 bar indicated mean effective pressure,increasing the main-injection-2 ratio(Rm-2)shortens the injection duration and increases the mean mixing time.Optimized Rm-2 could moderate the trade-off between the MPRR and the indicated specific fuel consumption with both reductions.An appropriate EGR should be adopted considering combustion and emissions.The DMI strategy achieves a highly efficient and stable combustion at high loads,with an indicated thermal efficiency(ITE)greater than 48%,CO and THC emissions at low levels,and MPRR within a reasonable range.Compared with the SMI strategy,the maximum improvement of the ITE is 1.5%,and the maximum reduction of MPRR is 1.5 bar/°CA.