During the highly transient process of the direct-start in a four-cylinder GDI engine,each cylinder exhibits specific characteristics in terms of in-cylinder conditions and energy demands,necessitating different contr...During the highly transient process of the direct-start in a four-cylinder GDI engine,each cylinder exhibits specific characteristics in terms of in-cylinder conditions and energy demands,necessitating different control for each cylinder.However,recent studies have paid insufficient attention to cylinders other than the first starting cylinder.This paper proposes a comprehensive control strategy based on experimental data from the direct-start process of the second,third,and fourth cylinders,aiming to enhance the characteristics of combustion and emission performance through the optimization of injection timing,equivalence ratio,and ignition timing.The research findings indicate that the second cylinder should inject fuel approximately 10 ms after the first cylinder ignites to mix thoroughly the fuel with air.The ignition timing of the second cylinder should be close to the highest point of the piston movement to minimize hindrance to the piston compression process.The third and fourth cylinders should adopt a delayed injection timing strategy to prevent the escape of injected fuel caused by low engine speed.The optimal ignition timing for the third cylinder is 20℃A BTDC,while the fourth cylinder should be ignited earlier due to its stronger airflow and faster formation of a mixture that can be ignited.As the fuel injection quantity increases,the power output of the three cylinders enhances,but at the same time,emissions also increase.Therefore,their optimal equivalence ratios are determined as 1.2,1.4,and 1.2,respectively,striking a balance between combustion and emission performances.展开更多
In the post-pandemic era,the global economic and security landscapes are fraught with complexities and uncertainties.Among them,four risk flashpoints merit attention:Certain countries are raising interest rates to sub...In the post-pandemic era,the global economic and security landscapes are fraught with complexities and uncertainties.Among them,four risk flashpoints merit attention:Certain countries are raising interest rates to subdue inflation,despite their already high levels of debt;the bulk commodities market is experiencing volatility,leading to global turbulence and change;trade protectionism is at the forefront of major-power rivalry in political and economic spheres;and regional security crises are compounding international tensions.Behind those flashpoints are contradictions that obstruct world peace and progress,including development imbalances,governance gaps,and structural tensions in global security.In the face of uncertainties,it is crucial for China to seize strategic opportunities and transform crises into favorable situations.China has launched the Global Development Initiative(GDI)and the Global Security Initiative(GSI)to contribute to global prosperity and security.The two initiatives demonstrate China’s commitment to addressing global deficits in peace,development,security,and governance.展开更多
In September 2021,Chinese President Xi Jinping attended the General Debate of the 76th Session of the United Nations General Assembly via video link and proposed the Global Development Initiative(GDI)for the first tim...In September 2021,Chinese President Xi Jinping attended the General Debate of the 76th Session of the United Nations General Assembly via video link and proposed the Global Development Initiative(GDI)for the first time.The GDI is China's solution to promoting global development and building a global community with shared development.展开更多
通过一款涡轮增压汽油直喷(gasoline direct injection,GDI)发动机低压废气再循环(exhaust gas recirculation,EGR)的试验,研究了EGR率和点火提前角的综合作用对增压GDI发动机的燃烧、缸压、排放和油耗等方面的影响。结果表明,在GDI增...通过一款涡轮增压汽油直喷(gasoline direct injection,GDI)发动机低压废气再循环(exhaust gas recirculation,EGR)的试验,研究了EGR率和点火提前角的综合作用对增压GDI发动机的燃烧、缸压、排放和油耗等方面的影响。结果表明,在GDI增压发动机中加入EGR后,由于废气的稀释和热容作用,使缸内燃烧持续期增大,排气温度下降,燃烧相位也发生了改变。这对发动机外特性的有利影响是油耗减少,CO和NO_x排放也明显减少;不利影响是EGR的加入提高了增压发动机的排气压力,导致泵气损失增加。此外,总碳氢(total hydro carbons,THC)排放也有所增加。在GDI增压汽油机中使用EGR系统并配合点火角的调节能够有效提高热效率,降低NO_x排放。展开更多
基金supported by the National Natural Science Foundation of China(grant number 51576129).
文摘During the highly transient process of the direct-start in a four-cylinder GDI engine,each cylinder exhibits specific characteristics in terms of in-cylinder conditions and energy demands,necessitating different control for each cylinder.However,recent studies have paid insufficient attention to cylinders other than the first starting cylinder.This paper proposes a comprehensive control strategy based on experimental data from the direct-start process of the second,third,and fourth cylinders,aiming to enhance the characteristics of combustion and emission performance through the optimization of injection timing,equivalence ratio,and ignition timing.The research findings indicate that the second cylinder should inject fuel approximately 10 ms after the first cylinder ignites to mix thoroughly the fuel with air.The ignition timing of the second cylinder should be close to the highest point of the piston movement to minimize hindrance to the piston compression process.The third and fourth cylinders should adopt a delayed injection timing strategy to prevent the escape of injected fuel caused by low engine speed.The optimal ignition timing for the third cylinder is 20℃A BTDC,while the fourth cylinder should be ignited earlier due to its stronger airflow and faster formation of a mixture that can be ignited.As the fuel injection quantity increases,the power output of the three cylinders enhances,but at the same time,emissions also increase.Therefore,their optimal equivalence ratios are determined as 1.2,1.4,and 1.2,respectively,striking a balance between combustion and emission performances.
基金supported by the key project of the National Social Science Fund of China(NSSFC):“Study on China-Russia Strategic Partnership for the New Era”(Grant No.20AGJ012).
文摘In the post-pandemic era,the global economic and security landscapes are fraught with complexities and uncertainties.Among them,four risk flashpoints merit attention:Certain countries are raising interest rates to subdue inflation,despite their already high levels of debt;the bulk commodities market is experiencing volatility,leading to global turbulence and change;trade protectionism is at the forefront of major-power rivalry in political and economic spheres;and regional security crises are compounding international tensions.Behind those flashpoints are contradictions that obstruct world peace and progress,including development imbalances,governance gaps,and structural tensions in global security.In the face of uncertainties,it is crucial for China to seize strategic opportunities and transform crises into favorable situations.China has launched the Global Development Initiative(GDI)and the Global Security Initiative(GSI)to contribute to global prosperity and security.The two initiatives demonstrate China’s commitment to addressing global deficits in peace,development,security,and governance.
文摘In September 2021,Chinese President Xi Jinping attended the General Debate of the 76th Session of the United Nations General Assembly via video link and proposed the Global Development Initiative(GDI)for the first time.The GDI is China's solution to promoting global development and building a global community with shared development.
文摘通过一款涡轮增压汽油直喷(gasoline direct injection,GDI)发动机低压废气再循环(exhaust gas recirculation,EGR)的试验,研究了EGR率和点火提前角的综合作用对增压GDI发动机的燃烧、缸压、排放和油耗等方面的影响。结果表明,在GDI增压发动机中加入EGR后,由于废气的稀释和热容作用,使缸内燃烧持续期增大,排气温度下降,燃烧相位也发生了改变。这对发动机外特性的有利影响是油耗减少,CO和NO_x排放也明显减少;不利影响是EGR的加入提高了增压发动机的排气压力,导致泵气损失增加。此外,总碳氢(total hydro carbons,THC)排放也有所增加。在GDI增压汽油机中使用EGR系统并配合点火角的调节能够有效提高热效率,降低NO_x排放。
