横向射流对排气系统红外辐射影响的实验研究

Experimental Research on Infrared Radiation Characteristics of Exhaust System with Jet in Cross-Flow Injection

为了研究横向射流注入后飞机发动机排气系统红外辐射的变化情况,设计了不同横向射流注入方案。实验探测了在喷口处注入横向射流后,排气系统在水平探测面上,3-5μm波段内的红外辐射强度。分析了排气系统的光谱辐射强度和积分辐射强度的变化情况,并结合速度分布图及红外热像图给出了解释。由于射流能够挤压尾喷流,提高主流剪切层脉动强度,强化其与冷气流的掺混,不同方案横向射流的注入,均能引起排气系统红外辐射强度的降低;在同一个探测面上,探测器能探测的红外辐射强度因不同射流方案对尾喷流的挤压方向不同而有较大差异,探测到的红外辐射由强到弱的方案依次：垂直注入、周向四股注入和水平注入;对尾喷流而言,相比于无横向射流注入状态,采用横向射流双股、单股垂直注入时,其红外辐射强度分别下降了60%,45%;横向射流双股、单股水平注入时,分别下降了5.1%,5.3%;采用周向四股注入时,下降了24.7%。

In order to study the variation of infrared radiation of airplane exhaust system when jet in cross- flow （JICF） injected, different kinds of JICF injecting schemes were designed. Experiments, designed with cross-flow injecting at nozzle orifice, were conducted to detect the infrared radiation intensity of the exhaust system on the wave band of 3 - 5μm in horizontal measuring plane. The variation of spectral radiant intensity and integral radiant intensity were analyzed and an explanation was presented by using velocity distribution and infrared thermo-grams. The infrared radiation intensity of exhaust system reduces when different kinds of JICF injected, for JICF can compress the jet exhaust flow, enhance the turbulence intensity of mainstream shear layer and inten- sify its mixing with cold air. In the same detection plane, the infrared radiation intensity detected by the detector varies considerably on different JICF schemes because they compress the jet exhaust flow in different directions. The schemes arranged by the detected infrared radiation intensity from strong to weak are as follows, the vertical injecting scheme, the circumference four-injecting scheme and the horizontal injecting scheme. As far as be con- cerned with the jet exhaust flow, compared with no injection state, the infrared radiation intensify reduces by 60% and 45%, respectively, when cross-flow is double or single vertically injected, reduces by 5.1% and 5.3%, respectively, when cross-flow is double or single horizontal injected, reduces by 24.7% when using the circumference four-injecting scheme.