In order to know the characteristics of reducing the exhaust gas infrared signal of the lobed mixer according to the external air mixing ratio, an infrared signal and temperature distribution measurement using a micro-turbojet engine is performed. A certain amount of compressed air is supplied through an external duct mounted on the micro-turbojet engine exhaust to simulate bypass flow, which is mixed with high-temperature core air and ejected to the atmosphere. The exhaust nozzle used in the experiment is a lobed mixer with a lobe of sinusoidal shape and is designed to have a penetration of 0.2. Exhaust gas temperature and infrared signal are measured according to distance from nozzle outlet under conditions of bypass ratio of 0.5, 1.0 and 1.4. Infrared reduction rates are compared to data without compressed air supply. As a result of the experiment, as the bypass ratio increased, the infrared signal of the exhaust gas and the temperature decrease with bypass ratio increase, and in the case of a bypass ratio of 1.4, the effect of reducing the temperature is observed even at a long distance. In addition, we compared the results of previous studies of a simple cone shape without mixer with infrared reduction effect. The results show that the lobed mixer has a greater effect on reducing the temperature of the exhaust gas and reducing the infrared signal than the cone nozzle. The structure of the mixed jet flow is also studied through Schlieren visualisation and 3D temperature distribution.

中文翻译：

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带外部空气混合的叶状混合器的红外信号

为了了解叶片式混合器根据外气混合比降低废气红外信号的特性，利用微型涡喷发动机进行红外信号和温度分布测量。一定量的压缩空气通过安装在微型涡轮喷气发动机排气装置上的外部管道提供一定量的压缩空气，以模拟旁通流，与高温核心空气混合并喷射到大气中。实验中使用的排气喷嘴是一个带有正弦形状叶片的叶片混合器，其设计穿透率为 0.2。在涵道比为0.5、1.0、1.4的条件下，根据距喷嘴出口的距离测量排气温度和红外信号。红外还原率与没有压缩空气供应的数据进行比较。实验结果表明，随着涵道比的增加，废气的红外信号和温度随涵道比的增加而降低，在涵道比为 1.4 的情况下，即使在很长的距离。此外，我们还比较了以往研究中没有混合器的简单锥形具有红外减少效果的研究结果。结果表明，与锥形喷嘴相比，叶状混合器对降低废气温度和减少红外信号的作用更大。还通过纹影可视化和 3D 温度分布研究了混合射流的结构。即使在很远的距离也能观察到降低温度的效果。此外，我们还比较了以往研究中没有混合器的简单锥形具有红外减少效果的研究结果。结果表明，与锥形喷嘴相比，叶状混合器对降低废气温度和减少红外信号的作用更大。还通过纹影可视化和 3D 温度分布研究了混合射流的结构。即使在很远的距离也能观察到降低温度的效果。此外，我们还比较了以往研究中没有混合器的简单锥形具有红外减少效果的研究结果。结果表明，与锥形喷嘴相比，叶状混合器对降低废气温度和减少红外信号的作用更大。还通过纹影可视化和 3D 温度分布研究了混合射流的结构。