Simplification of pyrolytic reaction mechanism and turbulent heat transfer of n-decane at supercritical pressures

摘要

Fluid flows and heat transfer of hydrocarbon fuels with endothermic pyrolysis play an important role in regenerative cooling of many flight vehicles and energy-conversion devices. In this paper, an approach to simplifying the global pyrolytic reaction mechanism of n-decane is proposed for problems with mild endothermic pyrolysis at supercritical pressures. The basic idea lies in the fact that the high-molecular-weight alkane or alkene components in a thermally decomposed n-decane mixture possess similar thermophysical properties and make only minor contributions to heat absorption; they can thus be grouped together and represented by a single light species. Numerical tests indicate that a reduced 12-species reaction mechanism for mild cracking of n-decane represents a reasonable choice in terms of model accuracy and efficiency. The reduced pyrolytic reaction mechanism is employed to study the effect of mild thermal decomposition of n-decane on turbulent convective heat transfer at supercritical pressures. The wall heat flux can be increased significantly at high fluid temperatures, due mainly to heat absorption resulting from endothermic pyrolytic reactions.