Modeling of Scalar Dissipation Rates in Flamelet Models for HCCI Engine Simulation

Saurabh Gupta, SeungHwan Keum, Hong Im
2012 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition   unpublished
The flamelet approach is considered a viable framework to the modeling of homogeneous charge compression ignition (HCCI) engines under stratified mixture conditions. However, there are several issues that need further improvement. In particular, accurate representation of the scalar dissipation rate, which is the key parameter to connect the physical mixing space to the reactive space, requires further investigation. This involves a number of aspects: (i) probability density functions, (ii)
more » ... functions, (ii) mean scalar dissipation rates, and (iii) conditional scalar dissipation rates, for mixture fraction (Z) and total enthalpy (H). The present study aims to assess the validity of existing models in HCCI environments both in the RANS and LES contexts, and thereby suggest alternative models to improve on the above three aspects. Nomenclature Z = mixture fraction H = total enthalpy Z  = Z scalar dissipation rate H  = H scalar dissipation rate  Z  = Mean Z scalar dissipation rate  H  = Mean H scalar dissipation rate  ZH  = Mean Z-H cross scalar dissipation rate  2 Z  = Variance of Z  2 H  = Variance of H  = Mean turbulent kinetic energy dissipation rate  = Mean turbulent kinetic energy I. Introduction omogeneous charge compression ignition (HCCI) engine technology shows promises as an advanced internal combustion (IC) engines in favor of lower NO x and soot emissions and higher efficiencies. This has led to an ongoing interest in HCCI engine research for over than two decades [1, 2] . Considering that the mixture field within the HCCI engines is nearly homogeneous, full-cycle engine simulations based on the multi-zone models have been conducted with success [3-6]. More recently, however, mixture stratification by exhaust gas recirculation or residual
doi:10.2514/6.2012-350 fatcat:r4k4rbtwtjfctbtekwdbcmt6t4