Low Mach number lattice Boltzmann model for turbulent combustion: flow in confined geometries

TL;DR

This paper introduces a robust hybrid lattice Boltzmann/finite-difference solver for turbulent combustion in complex geometries, demonstrating accurate simulations of flame propagation and swirl burner flows with good agreement to experimental and high-fidelity numerical data.

Contribution

It extends previous low Mach number lattice Boltzmann models by incorporating a more stable collision operator, enabling large Reynolds number turbulent combustion simulations in complex geometries.

Findings

Accurately simulates flame front propagation in 2D chambers with obstacles.

Successfully models turbulent swirl burner flows with good experimental agreement.

Demonstrates stability and accuracy at lower grid resolutions.

Abstract

A hybrid lattice Boltzmann/finite-difference solver for low Mach thermo-compressible flows developed in earlier works is extended to more realistic and challenging configurations involving turbulence and complex geometries in the present article. The major novelty here as compared to previous contributions is the application of a more robust collision operator, considerably extending the stability of the original single relaxation time model and facilitating larger Reynolds number flow simulations. Additionally, a subgrid model and the thickened flame approach have also been added allowing for efficient large eddy simulations of turbulent reactive flows in complex geometries. This robust solver, in combination with appropriate treatment of boundary conditions, is used to simulate combustion in two configurations: flame front propagation in a 2-D combustion chamber with several obstacles, and the 3-D PRECCINSTA swirl burner. Time evolution of the flame surface in the 2-D configuration shows very good agreement compared to direct numerical and large eddy simulation results available in the literature. The simulation of the PRECCINSTA burner is first performed in the case of cold flow using two different grid resolutions. Comparisons with experimental data reveal very good agreement even at lower resolution. The model is then used, with a 2-step chemistry and multi-component transport/thermodynamics, to simulate the combustor at operating conditions similar to previously reported experimental/numerical studies for $\phi$=0.83. Results are again in very good agreement compared with available large eddy simulation results as well as experimental data, demonstrating the excellent performance of the hybrid solver.