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Early injection timing is an effective measure of pre-mixture formation for diesel low-temperature combustion. Three algebraic subgrid models (Smagorinsky model, dynamic Smagorinsky model and WALE model) and one-equation kinetic energy turbulent model using modified TAB breakup model (MTAB model) have been implemented into KIVA3V code to make a detailed large eddy simulation of the atomization and evaporation processes of early injection timing in a constant volume chamber and a Ford high-speed direct-injection diesel engine. The results show that the predictive vapor mass fraction and liquid penetration using LES is in good agreement with the experiment results. In combustion chamber, the sub-grid turbulent kinetic energy and viscosity using LES are less than with the RANS models, and following the increasing time, the sub-grid turbulent kinetic energy and viscosity also increase and are concentrated on the spray area.

To understand the working mechanism of the porous medium (PM) internal combustion engine, effects of a porous medium heat regenerator inserted into a combustion chamber on the turbulent flow field and fuel-air mixture formation are studied by numerical simulation. The cylindrical chamber has a constant volume, in which a disk-shaped PM insert is fixed. A simplified model for the random structure of the PM is presented, in which the PM is represented by an assembly of a great number of randomly distributed solid units. To simulate flows in the PM a Brinkman-Forchheimer-extended Darcy's equation is introduced into the numerical solver. A version of two-equation k - ε turbulence model suggested by Antohe and Lage is employed for the turbulence prediction in the PM. A spray model, in which the effects of drop breakup, collision and coalescence are taken into account, is introduced to describe spray/wall interactions.

Porous medium (PM) engine was a new type engine based on the technique of combustion in porous medium, which can realize homogeneous and stable combustion. In this paper, the combustion and working processes of a specific PM engine was simulated by a two-zone model considering the influences of the mass distribution, heat transfer from the cylinder wall, mass exchange between zones and the heat transfer in porous medium. Influences of operating parameters, e.g. intake temperature and pressure, compression ratio, the excess air ratio on the performance of the PM engine were discussed. It is found out that the porous medium, acting as a heat recuperator, can significantly enhance the evaporation of liquid fuel and preheat the mixture, which promotes the ignition and combustion in the cylinder; and that the initial PM temperature and the compression ratio are critical factors controlling the compression ignition of the mixture.