In this paper, 7-species, 8-step finite-rate chemical reaction models of the non-equilibrium flow in a scramjet single expansion ramp nozzle have been investigated numerically. Chemical reactions and mass transfer under various freestream Mach numbers and flight height conditions are performed by the RNG k-ε turbulence model. The fluid flow in the nozzle is analyzed under non-equilibrium chemical reactions and frozen flow conditions. It is shown that the total temperature is obviously increased while the total pressure is evidently decreased in the chemical non-equilibrium flow at certain inlet conditions. The mass fractions of H2 and O2 are decreased while that of H2O is increased, and the mass fraction of N2 is almost identical throughout the whole reaction process. This indicates that combustion occurs in the nozzle, and the scramjet nozzle can supplement the combustion in a supersonic combustor so that the performance of the nozzle can be increased. It can be found that there are eddies in the chemical non-equilibrium flow because of the variations of the mass fractions of O2, H, O and OH. These eddies suggest that the variations of the mass fractions of O2, H, O and OH is non-monotonic. Although the flow is speeded up, the chemical reaction at the beginning part of the nozzle is faster than that downstream. The calculation shows that the non-equilibrium chemical reactions should always be considered in investigations of the flow and performance of scramjet nozzles.

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