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Regenerative cooling utilizing on-board endothermic hydrocarbon fuels of the high-temperature components of the scramjet engine plays a paramount role in maintaining the reliability and durability of the systems. A molecular kinetic model was proposed by modifying the Kumar–Kunzru kinetic model to describe the thermal cracking of n-decane at supercritical pressures. The apparent kinetic parameters at different pressures were optimized by the Levenberg–Marquardt algorithm. After the model validation, the role of pressure on the chemical heat absorption rate during n-decane pyrolysis was investigated using the one-dimensional plug flow model. It was found that the heat absorption rate first increases and then slightly decreases as the temperature increases at all pressures. The highest chemical heat absorption rate is located at a conversion of 41.81%, 53.34%, and 59.40% at 3, 4, and 5 MPa. In addition, the effect of pressure on n-decane pyrolysis was quantitated using the equivalence temperature. Under the simulation conditions considered in the present study, each 1 MPa increase in pressure produced the same conversion as a temperature decrease of 6.5–10 K. Finally, in order to extrapolate the kinetic model to a wider range of pressure conditions, a model extrapolation method based on the activation volume was proposed.

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