Thermal Behavior Inside Scramjet Cooling Channels at Different Channel Aspect Ratios

To study the thermal behavior inside scramjet cooling channels at different aspect ratios, a three-dimensional model of fuel flow in terms of the fuel real properties is built and validated through experiments. The whole cooling channel is divided into noncracking and cracking zones, and only the noncracking zone is studied in this paper. The simulation results indicate that heat transfer deterioration occurs very easily in scramjet engine cooling channels due to its small fuel mass flux, relatively high wall heat flux, and near-critical operating pressure. Increasing the channel aspect ratio is not always beneficial for reducing the wall temperature because of thermal stratification, and there exists an optimum value below 8 to make the wall temperature lowest. In addition, increasing the channel aspect ratio will reduce the thermal diffusion coefficient, resulting in a stronger thermal stratification and making the utilization of chemical heat sink and heat transfer design in the cracking zone of the cooling channel much more difficult. At last, a high operating pressure can alleviate the heat transfer deterioration, but it is not a good choice because of the heavier thermal stratification it brings and limited improvement in lowering the optimum wall temperature.