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首页> 外文期刊>The Aeronautical Journal >Infra-red signature reduction study on a small-scale jet engine
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Infra-red signature reduction study on a small-scale jet engine

机译：小型喷气发动机的红外签名减少研究

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This paper presents infra-red signature data for a small-scale, low pressure ratio turbojet engine typical of that used in unmanned air vehicle applications. The aim of the study was to test a number of different convergent nozzle designs concentrating on those with trailing edge modifications. The engine used in the tests has a single stage centrifugal compressor and radial inflow turbine and is designed to produce approximately 150N of thrust at 103,500rpm using liquid propane fuel. The test rig consisted of a calibrated thrust stand whilst the engine was controlled through an electronic engine control unit and laptop PC. The jet plume was visualised using an infra-red spectroradiometer which yielded qualitative data across the infra-red spectrum. Simultaneous measurements were also made of the engine thrust. A Pitot probe was used to take pressure readings across different sections of the exhaust flow. Analysis of the infrared signature of the engine exhaust plume and any thrust penalty yielded a performance comparison for each of the nozzles tested. Correlation of engine thrust with engine rpm showed that, within the accuracy of the measurements, there was no significant thrust penalty associated with the notched nozzles. Infra-red imagery of the plain and 60° notched nozzles indicated that the latter reduced the length of the hottest part of the exhaust plume by approximately 33%. The spectroradiometer data shows a significant reduction in spectral radiance for the CO_2 wavelength of approximately 4.3 μm when the notched nozzles are used. The 60° notched nozzle appeared to perform best in reducing the spectral radiance at this wavelength. Centreline total pressure measurements in the exhaust plume correlated well with the infra-red imagery in that a potential core length reduction of up to 30% could be achieved using the 60° notched nozzle. Total pressure contours recorded 20mm (0.43D) downstream of the nozzle exit plane suggest that the notched nozzles are promoting increased mixing through radial spreading of the jet possibly associated with increased streamwise vorticity (although the latter could not be confirmed). There were also signs that the jet plumes being investigated were swirling.
机译：本文介绍了小型，低压比涡轮喷气发动机的红外签名数据，这种数据通常在无人飞行器应用中使用。该研究的目的是测试许多不同的收敛喷嘴设计，重点是那些具有后缘修改的喷嘴。测试中使用的发动机具有单级离心压缩机和径向流入涡轮，并设计为使用液态丙烷燃料以103,500rpm的速度产生约150N的推力。该试验台由一个校准的推力架组成，而发动机是通过电子发动机控制单元和笔记本电脑进行控制的。使用红外分光光度计可以观察到喷射羽流，该分光光度计产生了整个红外光谱的定性数据。同时对发动机推力进行了测量。使用皮托管（Pitot）探头来采集排气流不同部分的压力读数。对发动机排气羽流的红外特征和任何推力损失进行分析，得出了每个测试喷嘴的性能比较。发动机推力与发动机转速的相关性表明，在测量的精度范围内，没有切口喷嘴引起的明显推力损失。普通喷嘴和60°切口喷嘴的红外图像显示，后者使排气羽流最热部分的长度减少了约33％。分光辐射计数据显示，当使用带槽喷嘴时，CO_2波长的光谱辐射显着降低，约为4.3μm。 60°切口喷嘴似乎在降低该波长的光谱辐射方面表现最佳。排气羽流中线的总压力测量值与红外图像非常相关，因为使用60°切口喷嘴可以使芯长减少多达30％。在喷嘴出口平面下游20mm（0.43D）处记录的总压力轮廓表明，带凹口的喷嘴通过射流的径向扩展促进了混合的增加，这可能与沿流的涡流增加有关（尽管无法确定）。也有迹象表明正在研究的喷气流正在旋转。

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