Laminar flame speed evaluation for CH4/O2 mixtures at high pressure and temperature for rocket engine applications

Pure methane-oxygen mixtures in liquid rocket engines lead to extreme pressure and temperature condi-tions that are prohibitive for most of the experimental setups. Hence, there is very little data on such flames in the literature, especially concerning the laminar flame speed Su, often limited at atmospheric pressure. The recent development of methalox rocket engines, which design process often requires CFD calculations, brings this lack of data to the forefront. Indeed, the CFD simulations require valid chemical schemes in the real operating conditions. To address this problem, flame measurements have been performed in a special isochoric combustion chamber with full optical access (OPTIPRIME) developed at ICARE. An extensive database in conditions never tested before is generated for several equivalence ratios, temperature and pres-sure ranges. Multiple chemical mechanisms were then compared to those results, showing various levels of agreement. Hence, the best mechanism from the literature on OPTIPRIME results and other literature exper-imental data was selected. A sensitivity analysis was performed to identify key chemical reactions controlling the flame speed. These key reactions could later be tuned by an optimization process to perfectly match the experimental results. Finally, additional measurements were performed in order to develop a Su =f(P,T) correlation to build a future flame speed database under rocket engines relevant conditions.& COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Pure methane-oxygen mixtures in liquid rocket engines create extreme pressure and temperature conditions that are difficult to replicate in experiments. This lack of data, especially regarding laminar flame speed Su at atmospheric pressure, poses a challenge for designing methalox rocket engines using CFD calculations. To address this issue, flame measurements were conducted in an isochoric combustion chamber with optical access, generating an extensive database for various conditions. Different chemical mechanisms were compared to the experimental results, and the most accurate mechanism was selected. Sensitivity analysis identified key reactions controlling the flame speed, which can be fine-tuned to match the experimental data.