Optimization of n-decane kinetic model and its application in supercritical regenerative cooling simulations

The thermal cracking and coke deposition of endothermic hydrocarbon fuels (EHFs) under supercritical conditions are pivotal to the safety and performance of hypersonic vehicle. The accuracy of the pyrolysis kinetic model is essential for the prediction of temperature fields, species distributions, and coke deposition within the regenerative cooling channels. In this study, the pyrolysis model of n-decane, widely regarded as a representative surrogate for RP-3, is optimized by performing the chemical kinetic simulations and sensitivity analysis. Computational fluid dynamics simulations confirm that the optimized pyrolysis model substantially improves the prediction accuracy of the fluid temperature, conversion rate, and intermediate species profiles compared to existing models reported in the literature. Furthermore, a two-dimensional transient CFD model is established by integrating the optimized pyrolysis model with the MC-II coking model. The dynamic mesh method is employed to simulate the growth of coke layers, encompassing both catalytic and pyrolytic coke within the regenerative cooling channel. Results indicate that the optimized pyrolysis model reliably predicts the onset location, growth rate, and mass distribution of the deposited coke. Consequently, the coke deposition increases the thermal resistance and accelerates the flow velocity due to the reduction of the effective flow area, which ultimately leads to the elevated wall temperature and a drastic rise in the pressure drop. This work develops a high-fidelity pyrolysis model for simulating coupled thermal-chemical-coking processes in the supercritical regenerative cooling channels, offering a robust theoretical basis for the design and optimization of hypersonic regenerative cooling systems.