污染组分对高超声速试验热力学参数影响研究

在燃烧加热风洞中进行的地面模拟试验,高焓气流成分有别于纯净空气,这种污染现象给试验结果带来了一定的不确定性。为了考察污染组分对高超声速模型试验流场的影响,在激波风洞中通过调节激波强度以及添加一定量的污染组分(H2 O 和CO2)来模拟燃烧加热风洞的来流条件,采用简化的不同角度斜劈来模拟飞行器试验模型对来流的压缩作用,结合近红外可调谐半导体激光吸收光谱技术(TDLAS)测量系统获取模型流场的静温,综合多组数据对比分析和研究污染组分对试验模型流场影响的特征和规律。结果表明,污染气体所产生的影响程度不仅与污染气体组分含量有关,而且与模型构型对来流的压缩程度以及来流自身的热力学参数状态都有密切的关系;对于压缩量不大的飞行器构型和来流静温不高的风洞试验而言,不同含量的CO2污染组分对流场静温影响不明显;但随着来流静温的提高或模型压缩量的增加,一旦二者的共同作用使得压缩后温升达到一定程度,污染效应的显现则渐趋明显。

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.