Modeling of scalar dissipation rates in flamelet models for low temperature combustion engine simulations

TL;DR

This paper investigates scalar dissipation rate modeling in flamelet-based combustion models for low temperature combustion engines, using DNS data to validate existing models and improve understanding of turbulent mixing.

Contribution

It provides fundamental insights into turbulent mixing in LTC engines and validates scalar dissipation rate models against DNS data for different ignition regimes.

Findings

Existing models of scalar dissipation rates are validated against DNS data.

Conditional scalar dissipation rate models show good agreement with DNS results.

The study enhances understanding of turbulent mixing in low temperature combustion.

Abstract

The flamelet approach offers a viable framework for combustion modeling of homogeneous charge compression ignition (HCCI) engines under stratified mixture conditions. Scalar dissipation rate acts as a key parameter in flamelet-based combustion models which connects the physical mixing space to the reactive space. The aim of this paper is to gain fundamental insights into turbulent mixing in low temperature combustion (LTC) engines and investigate the modeling of scalar dissipation rate. Three direct numerical simulation (DNS) test cases of two-dimensional turbulent auto-ignition of a hydrogen-air mixture with different correlations of temperature and mixture fraction are considered, which are representative of different ignition regimes. The existing models of mean and conditional scalar dissipation rates, and probability density functions (PDFs) of mixture fraction and total enthalpy are a priori validated against the DNS data.