Simplified pyrolytic model of RP-3 fuel at high conversion rates and the effects of primary reaction on the regenerative cooling process

The efficient and accurate prediction of fuel pyrolysis and surface coking in regenerative cooling systems is critical to developing hypersonic vehicles. This study adopts a combined method based on the chemical reaction kinetics and corresponding states principle to establish a simplified RP-3 fuel pyrolysis model. The chemical reactions are decreased from 24 to 6, and the species equations are reduced from 18 to 14. Compared with the existing simplified model, the model presents high fidelity in predicting temperature distribution, species diffusion, thermo-physical properties, flow field, and surface coking at high conversion rates. The results calculated by the simplified and baseline models are almost overlapped when the conversion rate is less than 100%, and the simplified model can reduce the computational time by 47.5%. In addition, the effects of the primary pyrolytic reaction on the regenerative cooling process are also investigated. The results indicate that the velocity at the channel outlet is nearly tripled by fuel pyrolysis, where 70.8% of the acceleration is generated by the primary reaction. Moreover, the chemical to sensible heat sink ratio is 55.6% when RP-3 fuel is fully cracked, and 85.5% of the chemical heat sink is provided by the primary reaction.