In the ground tests of hypersonic scramjet,the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants H 2 O and CO 2. The contaminants may cause the ignition characteristics of the fuel to become discrepant between ground tests and real flights. In order to properly assess the effects of the contaminants on ignition characteristics of hydrocarbon fuels,the effects of H 2 O and CO 2 on ignition charateristics of ethylene were investigated in a preheated shock tube. Based on...