|Alternative Title||Novel Transient Calorimetric Heat Flux Sensor|
|Place of Conferral||北京|
|Keyword||瞬态量热型热流传感器 金刚石量热片 气动热测量 动态修正方法 激波风洞试验|
With the development of space flight technology, the flight time of aircraft in atmosphere is longer, so the heat accumulation effect is serious, which makes the heat protection problems become more and more prominent. The accurate prediction of aerodynamic heating environment can effectively reduce the margin of thermal design and increase the payload, while the ground wind tunnel experiment is an important means to accurately predict the aerodynamic heating environment. The methods for measuring the heat flux of aerodynamic heating in wind tunnel tests can be divided into two categories: conventional and transient surface heat flux measurements. In the transient measurement, the surface temperature of the model and the temperature rise of the sensor are very low. Due to the small error caused by the change of the thermal properties of the material, the transient measurement result is superior to the conventional measurement.
There are three main types of transient heat flux sensors available today: thin film resistance thermometers, coaxial thermocouples and copper foil calorimeters. The thin film resistance thermometer was first applied, it has high sensitivity, but the film thickness is very thin, the structure and physical property parameters are not stable. The reliability of the measurement result is difficult to be improved, and the occasions where the airflow is seriously washed out or airflow is conductive are not suitable. Coaxial thermocouples have made remarkable progress in recent years, and their performance meets the requirements for use, but their sensitivity is low. The existing copper foil calorimeter uses a thermocouple to measure the back surface temperature. Although it is resistant to erosion, the sensitivity is not high, and the technology of the thermocouple contact point is difficult, which hinders further improvement of the accuracy of the measurement data.
The purpose of this study was to create a transient calorimetric heat flux sensor with a greatly improved sensitivity. If the calorimeter back temperature measuring element is changed from thermocouple to thin film resistance thermometer, the sensitivity of the sensor can be greatly improved. However, the existing calorimeter uses copper foil as a calorimetric sheet. The copper has high thermal conductivity, which satisfies transient calorimeter requirements, but it also has high electrical conductivity, which hinders the use of thin-film resistance thermometer as the back-side temperature measuring elements. The key to this study is to find a material with good thermal conductivity and good electrical insulation. After exploration, it was proposed to use diamond chips to replace the commonly used copper pieces as the calorimetric sheet, which greatly improved the output sensitivity of the transient calorimeter.
The new transient heat flux sensor can not only solve the problem in the case of low heat flux and strong scouring that no sensor is available, but also cover a wider range of heat flux measurement. Meanwhile, the sensor is in contact with the air flow with non-metallic materials, which can facilitate the study of aerodynamic heating under dissociation conditions. The new sensor has a wide range of applications.
The sensor design and selection of characteristic parameters is with the help of theoretical analysis and numerical calculation. The fabricated sensors have high linearity with temperature. The experimental results show that the repeatability error of the transient calorimetric heat flux sensor is within 4% and the error of measurement accuracy is within 6%. The sensor resistance keeps unchanged in the multi-tested and the measurement result is accurate and reliable.
Aiming at the measurement error brought by the miniaturization of sensors, this paper proposes a dynamic correction method for miniaturized sensors. Numerical calculations show that this dynamic correction method can decrease the heat flux test error from 19% to less than 1%. The dynamic correction coefficient was determined through the shock tunnel. The accuracy and feasibility of the dynamic correction method were verified in gas state aerodynamic heating test and stagnation point heating measurement in shock tube.
|张仕忠. 新颖的瞬态量热型热流传感器[D]. 北京. 中国科学院大学,2018.|
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