Effects of Porous versus Solid Inserts Pertaining to Instability Mitigation in Lean Direct Injection Combustion

Le résumé fourni par la source

View Video Presentation: https://doi.org/10.2514/6.2022-2349.vid Lean direct injection (LDI) is an emerging combustion strategy to meet the increasingly stringent emissions requirements for carbon monoxide, nitric oxide, soot, and unburned hydrocarbons for aviation gas turbines. The LDI process is designed such that the fuel-air mixing occurs vigorously at the combustor inlet, to produce a globally lean combustion process. Studies have shown that LDI combustion systems are vulnerable to thermoacoustic instabilities. Previously, we have shown that a porous annular disc placed at the dump plane of the combustor can be effective at reducing the strength of thermoacoustic instabilities in LDI systems. Conversely, a solid insert of the same bulk geometry has been shown to be detrimental to combustion stability under some flow conditions. This paper includes a parametric study of acoustic behavior over a range of equivalence ratios to identify conditions when fundamental mechanisms of flame stability may change. Using the results of this parametric study, simultaneous OH* chemiluminescence and particle image velocimetry will be applied at a test condition with marked change in the acoustic behavior, allowing a spectral analysis of both heat release and velocity fluctuations. Additionally, proper orthogonal decomposition and phase-averaging techniques are used to clearly identify structures that drive flame dynamics, with the purpose of evaluating how insert porosity alters the flow-flame interactions.

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