Modulation of wall turbulence by propagating flame of premixed hydrogen-air combustion

The mechanism of modulation of turbulent structures in the vicinity of a combustion engine wall is not yet clarified. Thus, we conducted direct numerical simulations of wall turbulence based on premixed hydrogen-air combustion using a detailed chemical reaction mechanism to clarify the mechanism of modulation of turbulence structures such as quasi-streamwise vortices by a flame propagating toward a wall. In particular, the turbulence modulation can alter the momentum and heat fluxes through the wall surface. In the simulations, we solved the fundamental equations for the compressible flow of multiple chemical species under combustion. The flame propagation speed was affected by the turbulence and was 2.04 times larger than that of the laminar flame. Moreover, upon examining the variation in the flow field, we determined that the turbulence kinetic energy in the flow field increased temporarily owing to the newly produced vortices along the flame surface including the existing turbulence vortices. In contrast, the turbulence vortices along the wall were suppressed as the flame approached the wall, and the turbulent flow tended to become laminar. In terms of vorticity transport equation, the suppression of the turbulence vortices was caused by the thermal expansion of the combustion rather than the increased viscosity. Furthermore, we determined that the vortex structure slightly influenced the chemical reaction process, but it strongly influenced the heat release rate distribution and concentration distribution of the chemical species. The current findings on the stated mechanism will aid in improving the accuracy of practical prediction and control methods for wall turbulence with combustion. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study investigated the mechanism of modulation of turbulent structures near a combustion engine wall through direct numerical simulations. The results showed that flame propagation influenced the turbulence and suppressed the turbulence vortices along the wall. Additionally, the study found that the vortex structure had a significant impact on the heat release rate distribution and concentration distribution of the chemical species.