Numerical investigation of pyrolysis and surface coking of hydrocarbon fuel in the regenerative cooling channel

Fuel pyrolysis is a common phenomenon in regenerative cooling channels. However, the alkenes and aromatic hydrocarbons produced by thermal cracking tend to deposit on the channel surface, leading to local heat transfer deterioration, corrosion resistance reduction, or blockage. This study establishes a numerical investigation at a supercritical pressure to evaluate the fuel flow effects on thermal cracking and surface coking. The results indicate a threshold of fuel flow rate or conversion rate that can improve the utilization of chemical heat sink. The threshold of the conversion rate for RP-3 fuel (Rocket Propellant No. 3 jet fuel) is around 80%, exceeding which will reduce the benefits of fuel endothermic pyrolysis. Moreover, a critical criterion of buoyancy parameter has been proposed for the severe pyrolysis of RP-3 fuel. In addition, the variation of fuel flow significantly influences the distribution of wall temperature and coking precursors, which further affects the coke layer thickness.