The present study discusses the effects of reacting and non-reacting flow conditions on the flow physics of a scramjet combustor. A cavity based supersonic combustor with a triangular strut is used to analyze the mixing behavior of fuels namely, hydrogen and ethylene, numerically. In this context, the influence of Mach number on static pressure distribution, mixing efficiency and the mole fraction of hydrogen and ethylene is analyzed. Our study reveals that there is a strong interplay between flow conditions viz., reacting and non-reacting and Mach number on flow field characteristics. It has been observed that the ignition delay time is very less for hydrogen fuel as compared to ethylene fuel. Further, the mixing efficiency is found to be maximum at Mach 2.5 and Mach 3.5 for hydrogen and ethylene, respectively for reacting flow conditions. Moreover, it was observed that additional igniters are required to enhance the rate of mixing in case of ethylene since the complete mixing of ethylene and air occurs at higher Mach number. It is seen that the deviation in the static pressure and mixing efficiency for reacting and non-reacting flow increases with the increase in Mach number. Further, this deviation is found relatively higher for hydrogen as compared to ethylene. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.