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The main aim of this paper is the numerical investigation of air-fuel mixture formation and spray and combustion characteristics of EF7 engine equipped with spray-guided direct injection system. For this purpose, first, a six-hole injector is simulated in three different injection pressures and to validate the fuel injection characteristics, the results are validated against the Istituto Motori-CNR experimental data. Then, the injector position is selected near the spark plug and by changing of injector angle relative to the axis of combustion chamber, the appropriate angle for optimization mixture formation is obtained. Then, the effect of injection pressure, start of first and second injection as well as the effect of two-stage fuel injection with different proportions of fuel mass at primary and secondary injection are studied on the mixture formation, wall film and engine emissions. The results showed that the injector angle is extremely effective on the mixture formation, pressure and the amount of unburned hydrocarbons due to its direct impact on wall film mass. Also, in the two-stage injection, relatively homogeneous lean mixture compared to the stratified mixture results better combustion at part load condition.

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In the present study, the effects of several global chemical kinetics in 3-dimensional numerical simulation of methane combustion in a horizontal combustion chamber which has lifted flame by a set of open source code OpenFOAM, is compared. The purpose of this comparison is to study the effects of 1, 2 and 4 step global kinetics on velocity, temperature and species distribution. In this simulation, conservation and state equations are solved simultaneously. Partial differential equations are discreted by finite volume method. The effects of turbulence by standard k-e, radiation by P1 model and turbulence-combustion interaction by PaSR are modeled. The results of numerical simulations have been validated by a cylindrical combustion chamber experimental data. The results show that the kinetics have considerable differences in results of velocity, temperature and species in the final third of the chamber where the flame is located, and differently predict locations of the flame. According to these results, 4-step mechanisms were more accurate than the 2-step type. Between 4 step mechanisms, JL is more accurate than Kim in overall; However, its calculation time is higher than the Kim. Single step kinetics were not able to keep the lifted flame.Towards the experimental results, 2-step model predicts the flame in downward and Kim mechanism estimates the flame in the upward.