Experiments on the direct-connect dual-mode Kerosene-fueled scramjet engine with two cavities were conducted in the supersonic combustion facility to compare the combustor performance under clean air and air vitiated with H2O conditions.The primary objective was to understand the complicated issues with regard to the effects of air-stream vitiation on scramjet test performance.A set of comparative combustion tests were conducted with the same test gas parameters of nominal Mach number 2

total temperature of about 828K and total pressure of about 800kPa.The simulations of reacting flowfield in the combustor under the same experimental conditions were conducted using flow solver AHL3D.The calculation results were close to experimental data.The final objective was to provide insight into the detail of combustion flow which was not resolved by the available instruments.