Near-limit H$_2$-O$_2$-N$_2$ combustion in nonpremixed counterflow mixing layers
Abstract
Numerical computations employing detailed chemistry are used to characterize the different combustion modes emerging in mixing layers separating nitrogen-diluted counterflowing planar streams of hydrogen and oxygen. Attention is focused on high degrees of dilution, resulting in near-limit flames, with peak temperatures close to the crossover temperature. A bifurcation diagram is presented in a plane, having the stoichiometric mixture fraction and normalized strain rate as coordinates, that identifies six different combustion regimes involving four different flame types, namely, diffusion-flame sheets, advancing and retreating edge flames, multiple flame tubes, and single isolated flame tubes. Multiple-tube flame configurations vary from small, round, widely separated flame strings at high strain rates to wide, flat, densely packed flame strips, with narrow flame-free gaps between them, at lower strain rates, and they are steady and stable in various arrays over a continuum of tube-separation distances. The observed flame behavior exhibits hysteresis in a certain range of parameters, with the structure that is established depending on the ignition mechanism, as it also does at high strain rates, and a continuum of different stable steady-state flame configurations exists, each accessed from a different initial condition.
Keywords
Cite
@article{arxiv.2406.18232,
title = {Near-limit H$_2$-O$_2$-N$_2$ combustion in nonpremixed counterflow mixing layers},
author = {Jaime Carpio and Prabakaran Rajamanickam and Antonio L. Sánchez and Forman A. Williams},
journal= {arXiv preprint arXiv:2406.18232},
year = {2024}
}