IMECH-IR  > 高温气体动力学国家重点实验室
新颖的瞬态量热型热流传感器
英文题名Novel Transient Calorimetric Heat Flux Sensor
张仕忠
导师俞鸿儒
2018-05-21
学位授予单位中国科学院大学
学位授予地点北京
学位类别博士
学位专业流体力学
关键词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
英文摘要

       随着临近空间飞行器的发展,飞行器在大气层中的飞行时间加长,热积累效应严重,防热问题变得越来越突出。气动热环境的准确预测,可以有效降低防热材料的余量,增加有效载荷,而地面风洞试验则是准确预测气动热环境的重要手段。风洞试验中气动加热表面热流率测量方法可分为两类:常规和瞬态表面热流率测量。瞬态测量中,模型表面和传感器温升很低,由于材料热物性变化导致的误差少,因此瞬态测量结果优于常规测量。

       现有的瞬态热流传感器主要有三种:薄膜电阻温度计,同轴热电偶和铜箔量热计。薄膜电阻温度计最早获得应用,它灵敏度高,但膜厚度很薄,结构和物性参数不稳定,测量结果的可靠性难以提高,且不适用气流冲刷以及气流导电的场合。同轴热电偶近年进展明显,性能符合使用要求,但灵敏度较低。现有铜箔量热计采用热偶测背面温度,虽然耐冲刷,但灵敏度不高,且热偶接点技术困难,妨碍测量数据的准度进一步提高。

       本项研究目的为创立一种灵敏度有较大提高的瞬态量热型热流传感器。如果量热计背面测温元件由热电偶改为薄膜电阻,则传感器的灵敏度便能大幅度提高。但现有量热计采用铜箔作为量热片,铜导热性能高,满足瞬态量热计要求,但导电性也高,阻碍薄膜电阻用作背面测温元件。本项研究的要害为探求一种具有良好导热性但电绝缘性很好的材料。经过探求,提出采用金刚石片代替目前普遍采用的铜片作为量热片,从而极大地提高了瞬态量热计的输出灵敏度。

       瞬态量热型热流传感器不但可以解决低热流、强冲刷的测量场合无传感器可用的现状,其热流的测量覆盖范围更广。同时,传感器同气流接触的为非金属材料,可以方便开展解离条件下的气动热试验研究,具有广泛的应用前景。

       传感器的设计和特征参数选取借助了理论分析和数值计算,制作的传感器阻值同温度的线性度高。通过激波风洞气动热测量试验表明,瞬态量热型热流传感器的重复性误差在4%以内,测量准确度误差在6%以内,多次试验传感器阻值保持不变,测量结果准确可靠。

       针对传感器小型化带来的测量误差难题,本文提出了一种小型化传感器的动态修正方法。数值计算表明,此动态修正方法可以将热流误差从19%提高到了1%以内。通过激波风洞开展了动态修正系数的测定,并在燃气状态下气动热试验测量和激波管驻点热流测量中验证了此动态修正方法的准确性和可行性。

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    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.

语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/73128
专题高温气体动力学国家重点实验室
作者单位中国科学院力学研究所
推荐引用方式
GB/T 7714
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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