To achieve the infrared/radar integrated stealth of a helicopter,the integrated infrared suppressor was incorporated into the design of stealth helicopter.Through numerical simulation,the temperature field,infrared radiation characteristics and radar scattering characteristics of stealth hel-icopter in hover were calculated.Results showed that under the combined effect of the ejected flow of integrated infrared suppressor and downwash airflow,the mixing duct and rear fuselage of stealth helicopter could be effectively cooled.Under the influence of tail rotor airflow,the local heating effect of the high-temperature exhaust on left fuselage was more significant.Due to the integrated design scheme of the exhaust system and rear fuselage,the latter could effectively shield the high-temperature mixing duct,therefore,total infrared radiation in 3～5 μm band was mainly from gas and fuselage skin.However,for 8～14 μm band,gas infrared radiation could be neglected.At 3 GHz,6 GHz,10 GHz and 15 GHz frequencies,the RCS mean of the stealth helicopter throughout the entire circumference was controlled below 4 dBsm,which indicated that the integrated design scheme could not only reduce infrared radiation but also have good radar stealth capability.
利用ABAQUS软件建立电阻应变片"等强度梁(基体)—胶粘层—基底—敏感栅—覆盖层"的有限元模型,分析了应变片各参数对电阻应变片应变传递的影响.结果表明,基体、胶粘层和基底弹性模量越大,敏感栅和覆盖层弹性模量越小;胶粘层、基底和敏感栅厚度越小,则应变过渡区宽度越小,平均应变传递率越大.此外,覆盖层的有无对应变传递几乎无影响.
在分析运输直升机物资运送过程和影响因素的基础上,制定运输直升机任务效能评估指标,采用ADC方法,并通过层次分析法和模糊综合评价法确定能力矩阵C,对运输直升机物资运送任务进行任务效能评估.该研究方法可以用于评估和比较不同状态下运输直升机的任务效能,结果可对运输直升机的效能评估和使用提供参考.
为保证直升机飞行安全、降低维护成本,通过监测发动机排气温度变化预测剩余寿命.首先在发动机实际外场使用数据中经采集、筛选、换算后得到有效分析数据;并将排气温度作为时间序列数据,从自身的相关性出发,通过历史数据预测未来趋势,建立了基于ARIMA模型的排气温度预测模型;运用该模型对某型涡轴发动机实际外场使用数据进行建模预测,结果显示短期波动较大,长期趋势精度较好.
采用分离涡(DES)方法对地面效应下的多桨倾转旋翼飞行器的非定常气动特性展开了研究.采用运动嵌套网格方法和动量源模型相结合的方式对旋翼/机身/地面耦合流场进行了不同精细程度的模拟,并重点从速度场、涡量场以及非定常气动载荷特征角度分析了地效下多桨倾转旋翼飞行器气动载荷非定常波动的形成机理.结果表明:相同机翼上的两副旋翼存在非定常干扰,使旋翼拉力出现非定常波动,波幅达到12.9%;前、后旋翼桨尖涡向下运动与地面碰撞后,部分气流向上卷起,在前后机翼之间融合形成尺度更大的涡结构,该涡结构向上运动并被前、后旋翼重新吸入;此外,该涡结构在前后机翼之间前后移动,被前后旋翼吸入的时刻不一致,从而导致全机在俯仰方向力出现非定常载荷波动,波幅为37.7%.
