Pressurised combustion in hot and low-oxygen environments: Chemiluminescence imaging and modelling

Abstract

Turbulent flames in a confined and pressurised jet-in-hot-coflow combustor, under a range of pressures and coflow conditions, are investigated in this study. The investigation involves both experimental and numerical analyses, with the central focus on extending the use of an atmospheric-pressure computational fluid dynamics (CFD) model to describe hot and low-oxygen combustion at elevated pressures. A series of CFD simulations are compared against experimental images, in terms of both flame structure and chemiluminescence behaviour. The imaging of OH* and CH* is performed experimentally for flames with Reynolds numbers of 10,000 and 15,000, issuing into coflows with O2 concentrations ranging from 3%–9%. The experimental results show a reduction in OH* and CH* intensity with increasing pressure under the various coflow conditions, while the CFD results display some key differences in the trends with pressure and O2. The computational analysis is complemented by a series of one-dimensional laminar flame simulations at a range of pressures and oxidant O2 concentrations. These simulations enable the changes in chemical kinetics with pressure and O2 concentration to be studied in greater detail, and several key differences in comparison with the CFD results are observed. Ultimately, the results highlight the importance of accurately predicting both the flow-field and finite-rate chemistry to reproduce the trends observed under hot and low-oxygen combustion conditions at elevated pressures.