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 this study, a ‘‘direct-starting'' procedure was used to activate a single-chamber biocathode microbial electrolysis cell(MEC) and the development of a biocathode was studied through output current curves ...In this study, a ‘‘direct-starting'' procedure was used to activate a single-chamber biocathode microbial electrolysis cell(MEC) and the development of a biocathode was studied through output current curves and cyclic voltammograms. It only took 163 h for a successful start-up, and a current density of 14.75 A/m^2 was obtained. In the formal hydrogen-production stage, it was found that the biocathode MEC was comparable with the Pt/C cathode MEC in terms of current density and energy efficiency, and the hydrogen recovery, cathodic hydrogen recovery, and hydrogen production rate of the biocathode MEC were 71.22% ± 8.98%, 79.42% ± 5.94%, and 0.428 ± 0.054 m^3 H_2/m^3 days, respectively, which were slightly higher than those obtained with the Pt/C cathode MEC. Besides, under the effect of applied voltage, the microbial populations in the anodophilic biofilm of MEC(MECan) and the cathodophilic biofilm of MEC(MECca) were less diverse than those of the original aerobic activated sludge(AAS) and the anodophilic biofilm of MEC(MECan). Furthermore, the microbial community structures evidently differed between MECan/MECca and AAS/MFC.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funded by the National Natural Science Foundation of China (Grant No. 51703151)the Natural Science Foundation of Shanxi Province of China (Grant No. 201601D011023)
文摘In this study, a ‘‘direct-starting'' procedure was used to activate a single-chamber biocathode microbial electrolysis cell(MEC) and the development of a biocathode was studied through output current curves and cyclic voltammograms. It only took 163 h for a successful start-up, and a current density of 14.75 A/m^2 was obtained. In the formal hydrogen-production stage, it was found that the biocathode MEC was comparable with the Pt/C cathode MEC in terms of current density and energy efficiency, and the hydrogen recovery, cathodic hydrogen recovery, and hydrogen production rate of the biocathode MEC were 71.22% ± 8.98%, 79.42% ± 5.94%, and 0.428 ± 0.054 m^3 H_2/m^3 days, respectively, which were slightly higher than those obtained with the Pt/C cathode MEC. Besides, under the effect of applied voltage, the microbial populations in the anodophilic biofilm of MEC(MECan) and the cathodophilic biofilm of MEC(MECca) were less diverse than those of the original aerobic activated sludge(AAS) and the anodophilic biofilm of MEC(MECan). Furthermore, the microbial community structures evidently differed between MECan/MECca and AAS/MFC.
