Treffer: Parametric study on the methanol/diesel JCCI mode with dual-direct injection system in a light-duty engine.

• The methanol/diesel JCCI mode with dual-direct injection system was introduced to improve the engine performance at 75 % engine load and 3000 r/min. • The 3D CFD solver combined with NSGA Ⅱ through self-developed python code was employed to conduct the multiple-objective optimization. • The optimal engine performance can be realized with the CA50 at 4 ∼ 7 °CA ATDC, the MER within 78.9 ∼ 80.8 %, along with the increased T in and retarded SOI m. • The MER presents the most significant influence on the engine performance, the SOI d and T in also have a significant effect on EISFC. The methanol/diesel jet controlled compression ignition (JCCI) mode with dual-direct injection system has been proven as an advanced engine combustion mode to reduce carbon emissions and to achieve an efficient and clean working process based on the experiments on a light-duty high-speed 186FA platform. The methanol/diesel dual-direct injection system also brings further flexibility and possibilities for engine control. Therefore, the parametric optimization and sensitivity analysis, involving the initial in-cylinder pressure and temperature (p in and T in), the start of diesel injection (SOI d) and methanol injection (SOI m), and the methanol energy ratio (MER), were performed in this work using the three-dimensional computational fluid dynamics (3D CFD) combined with the nondominated sorting genetic algorithm (NSGA-Ⅱ). The results indicate that the MER within 78.9 %∼80.8 % and the initial in-cylinder temperature within 421.8 ∼ 431.1 K can realize the high-efficiency optimal performance, and a higher MER in conjunction with a higher initial in-cylinder temperature is needed to avoid incomplete combustion. The CA50s for the optimum cases are overall located at 4 ∼ 7 °CA ATDC. The retarded SOI d increases the local reactivity and combustion temperature, resulting in higher nitrogen oxide (NO x) emissions and lower equivalent indicated specific fuel consumption (EISFC). According to the comparison of the typical cases, the late SOI m and late SOI d lead to fast two-stage high-temperature combustion along with the increased NO x emissions. However, the soot, total hydrocarbon (THC) + carbon monoxide (CO) and EISFC are lower because of the higher local equivalence ratio. The advanced SOI m increases the wall-wet and crevice issues, resulting in the low combustion efficiency. The sensitivity analysis shows that the MER presents the most significant influence on the engine performance. The SOI d and T in also exert a significant effect on EISFC, while p in has an insignificant influence on the engine performance. [ABSTRACT FROM AUTHOR]