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Dynamic models for large eddy simulation of the G-equation of turbulent premixed combustion are proposed and tested in forced homogeneous isotropic turbulence. The basic idea is to represent the ‘‘filtered propagation term’’ as ‘‘propagation of the filtered front at higher speed,’’ where the enhanced filtered-front speed is modeled. The validity of the(More)
To characterize the ignition process in homogeneous charge compression ignition engines, high fidelity simulations are performed to study the effects of different initial temperature distributions on the autoignition of a turbulent homogeneous mixture at high pressure. The effects of the initial temperature distribution on the ignition and subsequent heat(More)
The interaction of turbulent nonpremixed flames with fine water spray is studied using direct numerical simulations (DNS) with detailed chemistry. The study is of practical importance in fire safety devices that operate in the mist regime, as well as an inexpensive temperature control mechanism for gas turbines. The implemented computational methods for the(More)
The dynamics of soot formation in turbulent ethylene–air nonpremixed counterflow flames is studied using direct numerical simulation (DNS) with a semi-empirical soot model and the discrete ordinate method (DOM) as a radiation solver. Transient characteristics of soot behavior are studies by a model problem of flame interaction with turbulence inflow at(More)
The upstream interaction of twin premixed hydrogen-air flames in 2-D turbulence is studied using direct numerical simulations with detailed chemistry. The primary objective is to determine the effect of flame stretch on the overall burning rate during various stages of the interaction. Preferential diffusion effects are accounted for by varying the(More)
This paper presents a computational algorithm to predict highly-transient flame behavior in counterflow situations. The first objective of the paper is to extend the transient counterflow problem to incorporate some gasdynamic compressibility effects, yet retain the desirable similarity structure. By relaxing assumptions in earlier formulations, the(More)
As an attempt at providing insight to develop better modeling strategies for HCCI engines, the ignition and propagation of a reaction front in a premixed fuel/air stream mixed with hotter exhaust gases is computationally investigated using the opposed-flow configuration. The effects of heat and radical transport are studied by imposing various mixing rates(More)
As a fundamental study relevant to micro-combustor application, the effects of mixture dilution on the lean extinction characteristics is studied for a stagnation-point flow system with a methane/air mixture over a platinum surface. For steady conditions, the level of flammability extension by surface reaction depends strongly on the mixture dilution, such(More)
A three-dimensional reacting flow modeling approach is presented for diesel engine studies that can be used for predictions of trends in soot emissions for a wide range of operating conditions. The modeling framework employs skeletal chemistry for n-heptane for ignition and combustion, and links acetylene chemistry to the soot nucleation process. The soot(More)