Influence of H2O and CO2 Contamination in Air on the Combustion Properties of Ethylene

Clean air at high temperature and velocity acts as oxidant for fuel combustion in a hypersonic scramjet. In ground tests, however, high temperature air produced by combustion heating contains H2O and CO2 contaminants. In this study, the effects of contamination on the properties and wall pressure of a combustion chamber during C2H4 combustion was investigated. Clean air was heated via electric resistance and water vapor and carbon dioxide gas were added to simulate vitiated air. Through comparative experiments between clean air and vitiated air, effects such as the stability of the flame and the wall pressure inside the combustion chamber on the contamination during the combustion of ethylene were evaluated. Furthermore, the impacts of H2O and CO2 in air upon ignition delay and combustion temperature were simulated by assuming a rigid and adiabatic reactor. Results from both experiment and kinetics modeling are discussed by considering the chain reaction mechanism.