Thermal response time characteristics of endothermic hydrocarbon fuel in cooling channels with thermal cracking

Abstract

The varying operating conditions of hypersonic vehicles often lead to variations in the demand for cooling capability and the heat transfer performance of hydrocarbon fuel in regenerative cooling channels. Understanding the transient heat transfer performance of hydrocarbon fuel is essential for optimizing cooling systems; existing research on thermal response time distribution, particularly in the context of thermal cracking, is notably limited. This study combines experimental and numerical approaches to investigate the transient flow and heat transfer behavior of hydrocarbon fuel undergoing thermal cracking, fills a gap in the current literature and offers new insights into the management of cooling systems. According to the experimental data, the thermal response time decreased as temperature increase, which is different from that of noncracking region. A series of numerical simulation results revealed that the enhancement of heat transfer at the interface and the acceleration of thermal diffusion within the fluid due to thermal cracking makes the heat transfer faster, eventually lead to the shorter thermal response time. Thus, the thermal response time distribution across the entire temperature range is characterized by a pattern of initial decrease, followed by an increase, and then a subsequent decrease as the temperature rises. In addition, the nonlinear relation between the chemical reaction and temperature caused the thermal response and chemical reaction response to be unsynchronized, leading to differences in the transient response processes induced by increased and decreased heat fluxes. Based on the experimental data, a new empirical correlation with an error within 20% effective across entire temperature range is proposed, offering a valuable tool for engineers and researchers working with hydrocarbon fuels in hypersonic applications.