直升机发动机舱通风、遮挡和隔热对红外辐射特性的影响

Effects of ventilation,shelter and thermal resistance in nacelle of helicopter on infrared radiation characteristics

为了降低直升机发动机舱蒙皮的温度，减弱直升机红外辐射能量，采用数值仿真的方法研究其处于悬停状态、考虑了旋翼下洗作用的发动机舱蒙皮温度场和直升机红外辐射特性．针对基准发动机舱结构提出了在舱内加设辐射遮挡套、增开通风百叶窗、排气管尾缘修型和蒙皮内侧敷设隔热层等改进方案，研究了上述改进方案对直升机发动机舱蒙皮温度场和红外辐射特性的影响，得到了如下结论：①在发动机舱内加设辐射遮挡套后，整机侧向探测方位角内3～5“m红外辐射强度出现了约25％的增幅，8～14bcm波段红外辐射与原始结构相当．②在发动机舱顶部增开通风百叶窗，直升机3～5肛m红外辐射低于原始结构约12％，8～14um波段红外辐射与原始结构相当．③在发动机舱顶部增开通风百叶窗的基础上，对排气管尾缘采取延伸遮挡以及在发动机舱蒙皮内侧敷设隔热层，整机3～5tLm波段红外辐射的最大值下降约70％，8～14ttm波段红外辐射的最大值下降约10％．

To reduce the temperature on helicopter nacelle skin and lower the helicopter infrared radiation, numerical investigation was conducted to study the temperature distribu tion on the nacelle skin and the helicopter infrared radiation characteristics for helicopter un der hovering state in consideration of the rotor down wash. Several improved schemes for the nacalle were presented based on the baseline nacalle configuration, such as adopting radi ation shelter, adding ventilation slots, improving trailing edge of mixed exhaust duct, and making thermal resistance layer. The effects of above treatments on the temperature distributionand infrared radiation characteristics were assessed. Conclusions can be listed as follows： （1） With the adopted radiation shelter, infrared radiation intensity of the helicopter is enhanced by 25% in 3-51um band but remained almost the same in 8-14um band. （2） With the added ventilation slots, infrared radiation intensity of the helicopter is reduced by 12% in 3-5um band but remained almost the same in 8-14um band. （3） With the added ventilation slots, in：proved trailing edge and thermal resistance layer, infrared radiation intensity of the helicopter is re- duced by 70% and 10%, respectively, in 3-5um and in 8-14um bands.