An experimental investigation on the vitiation effects of hypersonic testing of aerothermal behaviors

For ground tests in a combustion-heated wind tunnel,the composition of the tes-ting gas is different from that of the air,which may cause some unexpected deviations and result in more uncertainties.An experimental investigation on the vitiation effects of hypersonic testing is carried out with special focus on the aerothermal behaviors of the model flow.The experiments are conducted in a shock tunnel and the related combustion-heated wind tunnel flow conditions are simulated by adj usting the strengths of shock waves and adding specific mole fractions of contam-inations (H2 O and CO2 ).A couple of simplified wedge models with different deflection angles are used to characterize the typical compression of the flow by the vehicle model.The static tem-peratures of the wedge model flow under groups of conditions are obtained through tunable diode laser absorption spectroscopy (TDLAS)measurement system.The results indicate that the vitia-tion effects depend not only on the fractions of contaminants,but also strongly related to the freestream static temperature as well as the compression process of the model flow.A low tem-perature incoming flow with small compression angle is favorable for reducing the vitiation effects.On the other hand,if the combined interaction of the flow with the compression wall is so severe that the resulted static temperature is increased to a certain level,an obvious depend-ence of vitiation effects on the contaminations are readily observed.