Effects of Air Vitiation on Scramjet Performance Based on Thermodynamic Cycle Analysis

Abstract

The influences of air vitiation on scramjet performance were studied in this paper based on thermodynamic cycle analysis. By the aid of NASA Glenn’s computer program Chemical Equilibrium with Applications (CEA), parameters of vitiated air at combustion heater exit could be calculated. Based on thermodynamic cycle analysis, scramjet performance, including internal thrust, specific thrust, and specific impulse, were analyzed with 9 simulation criterions under Mach 4.5 and 6.5 conditions, respectively. The results show that, (1) specific heat and specific heat ratio of vitiated air are mainly affected by combustion heating medium, and also have minor connection with temperature criterions. Moreover, choosing different simulation criterions influences the temperature or pressure between clean air and vitiated air significantly; (2) the internal thrust and specific thrust of scramjet with hydrogen heated airstream are greater than that of scramjet with alcohol and kerosene heated airstream; (3) matching static pressure and dynamic pressure will obtain higher internal thrust compared to total pressure, and the effect of pressure criterions on internal thrust is more remarkable than temperature criterions. On the other hand, these findings proved that the method based on thermodynamic cycle analysis is a simple, dependable, and effective approach to evaluate the scramjet performance affected by air vitiation.