Thermal behavior of steam reforming reaction at different aspect ratios in the scramjet engine cooling channel

The structure of the regenerative cooling channels is crucial for high-performance scramjet engines. To investigate the effect of catalyst coating thickness and aspect ratio on the thermal behavior of steam reforming reactions in cooling channels, three-dimensional simulation models of flow and heat transfer were developed in this study based on the steam reforming reaction. The models were validated by experiment. We propose a parameter named cracking heat transfer efficiency index (CHTEI) to evaluate synergistic effect of cracking rate and convective heat transfer coefficient. The calculated results indicate that CHTEI is favorable at a catalyst coating thickness of 100 μm. The lower aspect ratio effectively improves the inhomogeneity of temperature and n-decane distribution, as well as strengthens the heat exchange capability of fuels. However, lower aspect ratios result in low cracking rates, which are detrimental to chemical recuperation process of the combustion chamber. We present the cracking uniformity efficiency index (CUEI) to measure the combined cracking rate and inhomogeneity coefficient of the n-decane distribution. Consequently, CUEI is optimal at an aspect ratio of 2. This study is expected to provide new ideas and necessary theoretical support for thermal management of hypersonic vehicles at high Mach numbers.