Development of coke model for thermal cracking of hydrocarbon fuels under supercritical conditions and its experimental validation

Abstract

Coke prediction and its judicious mitigation for thermal cracking of fuels is an essential aspect of regenerative cooling in hypersonic vehicles. The present study performs a numerical investigation of coke prediction for the thermal cracking reactions of hydrocarbon fuels under supercritical conditions. Numerical simulation is performed to obtain the concentration profiles of coking precursors along the length of the reactor. Product distribution and transport properties are estimated using the shear stress transport k-ώ turbulence model. A predictive coke model is developed by considering operating conditions, feed density, and coke precursors concentration. The model is validated with literature-reported experimental data for different hydrocarbons. The model predicted coke value lies within ± 25 % of the experimental coke for a temperature range of 550 °C to 700 °C and a pressure range of 35–55 bar. The suitability of the Coke model is also examined by conducting experiments in an electrically heated flow reactor with n-heptane. At 650 °C and 40 bar pressure, the experimentally obtained coking rate (0.6 mg/min) shows a good agreement with the model-predicted coking rate (0.7 mg/min).