塞块式量热计长时间变工况热流测量

采用塞块式量热计对200 MW燃气流风洞试验件表面热流进行测量,试验过程中塞块式量热计遍历风洞的启动、模型变攻角、停车等阶段。为准确获取不同攻角条件下模型表面热流值,采用数值仿真对塞块式量热计的传热特性进行分析,研究背温反算的热流值与输入热流边界条件的差异,提出塞块式量热计长时间使用的修正方法,该修正方法通过一次稳态热流源的标定即可获得其他热流边界条件下的结果,从而简化标定过程。将修正方法应用于长时间变工况热流测量修正时,偏差小于2%,增加了塞块式量热计的使用范围,通过一次风洞试验,获取多个稳态工况条件下试验件表面热流值,节约风洞运行成本。此外,该修正方法也可用于高热流瞬时测量结果的修正。     

镀层式同轴热电偶数据处理方法研究

同轴热电偶热流传感器进行热流测量是风洞试验热流测量的一种非常重要的手段.应用二维轴对称热传导理论,结合横向传热影响、表面温升对热流的耦合影响、流场建立初始阶段来流对传感器表面温升的影响等因素,为激波风洞同轴热电偶热流传感器的数据处理方法建立了两套方案,为进一步提高测热精度提供了技术途径.     

辐射平衡壁温下有限催化模型数值模拟

文章发展了高超声速飞行器辐射平衡壁温下有限催化的数值方法,将数值模拟结果与基于返回舱外形的风洞实验数据进行了对比,并进一步针对典型高超声速飞行器钝双锥研究了辐射平衡壁温下有限催化对气动热环境的影响规律.针对返回舱外形的数值实验表明,完全催化与完全非催化边界条件下壁面热流密度均与风洞实验结果偏差较大,而采用合适的有限催化模型获得的壁面热流密度与风洞实验结果符合良好.针对典型高超声速飞行器钝双锥的研究表明,在辐射平衡温度边界条件下驻点附近氧原子的催化复合系数约为0.17,氮原子的催化复合系数约为0.026,大面积区则分别降为0.005 3和0.01.在驻点热流密度方面,完全催化的壁面热流峰值比有限催化高约21%,而完全非催化的壁面热流峰值比有限催化低约29%.      

高温燃气流风洞全尺寸舱段热结构试验技术研究

利用200 MW高温燃气流风洞,开展1:1全尺寸舱段模型热结构/热匹配试验.围绕风洞试验状态调节、介质影响热流设计评估、多台阶长时间热流校测等技术问题,开展高温燃气流风洞舱段类模型试验设计方法研究.引入新的燃气流风洞试验状态调节方法和考虑燃气介质差异的等效冷壁热流修正方法,并通过长时间变工况表面热流测试方法的建立,实现了多工况同步流场校测.试验设计方法有效应用于全尺寸舱段模型热结构/热匹配试验研究中.经试验验证,所建立的长时间大功率燃气流风洞试验设计方法有效可行,实现了全尺寸舱段飞行热环境的有效模拟.      

前缘一体化高温热管结构防热效果的实验研究

为了研究复杂构型前缘一体化高温热管结构在高热流密度状态下的防热效果, 设计了飞行器气动加热轨道, 实现了高温热管低状态完全启动、高状态极限考核。然后采用超声速电弧风洞驻点自由射流结合轨道模拟技术, 模拟乘波体飞行器的前缘疏导构件的气动加热环境, 开展了前缘一体化高温热管结构防热效果研究。实验结果表明, 一体化高温热管结构能够多次使用, 低状态下高温热管的启动时间约为115 s, 在高状态下结构依然有效, 降温系数达到24.5%, 验证了前缘疏导式防热结构的防热效果, 可为未来新型高超声速飞行器非烧蚀热防护系统的设计提供指导。      

温敏涂料TSP热流密度测量方法及应用

温度敏感涂料（temperature-sensitive paint，TSP）可以实现高空间分辨率的温度测量.基于时间解析温度数据计算热流密度是典型的导热反问题.基于一维双层导热模型，通过解析或数值求解的方法计算热流密度，是上述问题的通用解法.在工程应用中，可根据试验工况简化一维双层导热模型，采用更简便的方法进行热流计算.TSP测量热流的精度受涂料厚度、TSP测温真实位置和材料热物性变化等因素影响，相应地可以在涂料设计、物理建模以及计算方法等方面进行完善，提高TSP热流测量的精度.TSP热流测量在暂冲式和激波式两类高超声速风洞中均已得到成功应用，文章结合两个应用实例对工程应用中的挑战与对策进行了讨论.      

气动热参数辨识在测热试验中的应用研究

数据处理方法的合理性直接关系到测热试验精度的提高。本文针对同轴热电偶的测热特点,采用轴对称传热模型,应用共轭梯度法、顺序函数法,建立了合理的同轴热电偶测热的数据处理方法。计算表明,两种方法具有较高的计算效率,能在一定程度上提高试验精度,具有较大的推广应用价值。     

吸气式高超声速飞行器气动力气动热的数值模拟方法及应用

对吸气式高超声速飞行器而言,物面热流和摩阻的准确预测对飞行器设计及安全十分关键.介绍采用CFD准确预测气动力和气动热的方法,包括流动的控制方程、湍流模型及湍流的先进壁面函数边界条件,介绍流动的数值求解方法.对典型超声速层流和湍流流动的摩擦阻力和热流进行详细的验证与确认,考察CFD工具在使用先进壁面函数边界条件后,湍流计算的法向网格无关性能力.对设计的一种吸气式高超声速飞行器的气动力和气动热进行数值模拟,为飞行器的气动设计及热防护提供了可靠的数据.     

圆锥标模高超声速俯仰自由振动试验与分析

为解决自由振动式动导数试验技术在大尺度高超声速风洞中,高气动载荷环境与低频率模拟要求之间的突出矛盾,进一步提高高超声速飞行器较低气动阻尼的测量精度,发展了基于组合式动导数天平的Ф 1 m量级高超声速风洞自由振动试验技术.设计组合式动导数天平,轴承组件承载模型轴向和法向气动力,弹性应变梁提供系统恢复力矩,并可根据减缩频率的要求调整系统自由振动频率,有效提高了天平承载能力,拓展了试验频率模拟范围.在中国空气动力研究与发展中心Ф 1 m高超声速风洞,利用本系统进行了10°半锥角不同钝度圆锥标模俯仰动导数校测试验,所测俯仰动导数与文献结果最大相对误差在6%以内,验证了试验系统和测试结果具有较好的稳定性与重复性.      

应用Duhamel定理确定固体界面上的瞬时热流密度

一、前言 在许多工程实际问题中,常常需要确定固体界面上的瞬时热流密度。由于直接测量十分困难,一般通过测量物体内部某些点的局部温度来推算界面热流密度。这类问题称为导热反问题。但是求解反问题时,总是利用衰减后的数值来计算边界上的热流密度,加上测点位置的误差,计算精度较差。利用高灵敏度微型表面热电偶测出的界面温度直接     

Stagnation point transient heat flux measurement analysis from coaxial thermocouples

The transient heat flux measurement at stagnation point is a significant solicitation at highly compressed flow field environment. In aerodynamics surface heating point of view, the estimation of stagnation heat fluxes at the tip of a blunt body is very imperative. When the blunt body is exposed to high-speed flow field environments, at the stagnation point heat transfer would be maximum. The coaxial surface junction thermocouples (CSJTs) are convenient for short duration time scale due to the fast response in the range of millisecond or less (?0.1 ms). These robust CSJTs have the tractability of intensifying them directly on any type of surface and can be used for routine measurement in ground-based impulse amenities as a temperature measuring devices where rapid heat loads are anticipated. In this work, three different types of coaxial thermocouples K-type, E-type, and J-type have been designed and contrived. The microstructural analysis of measuring surface property has been carried out to see the surface morphology using field emission scanning electron microscopy (FESME) and chemical characterization of these CSJTs materials using energy dispersive X-ray analysis (EDXA) technique is used to verify qualitatively appraise the CSJTs materials composition. The thermal coefficient of resistance (TCR) and sensitivity (S) of each coaxial thermocouple have been determined by using oil-bath calibration technique with the linear variation of resistance corresponding to the variation of temperature and found that these coaxial thermocouples are highly sensitive and suitable for highly transient heat transfer measurements. For this purpose, these three types of CSJTs have been tested under highly compressed heated air 310 K temperature for 100 ms at pressure 6.1 bar with Mach number unity (M = 1) using compressor test rig. Numerical simulation has also been carried out with these three RTDs to satisfy the experimental parameters using Ansys Fluent 15.0 and typical transient temperature recorded. Surface heat fluxes recovered from experimental and numerical transient temperatures histories using semi-infinite heat conduction modeling having good agreement with accuracy ±3% or less. This study divulges the expertise of these handmade coaxial thermocouples for transient surface heat flux measurement for short durations at highly compressed air facilities.     

Magnetic Field Effect on the Volt‐Equivalent of Arc Spot Heat Flux

The results of an experimental study of the arc spot heat flux on the copper cathode of a coaxial Electric Arc Heaters (EAH), with magnetically driven arc, in air are presented. The three rings method was used for indirect separation of arc spot heat flux from total heat entering the electrode. As a result of joint generalizing new and previously published data, the linear dependence of the volt equivalent of arc spot heat flux on magnetic field was obtained for the range B = 0.01 – 1 Tesla and atmospheric pressure. A method, which allows to improve the measurement of the volt equivalent in highly unsteady arc spots, is proposed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

热强度试验中热电偶调理模块的设计与应用

热强度试验现场环境复杂,会对热电偶、热流等微弱电压信号产生较大电磁干扰,影响测量精度甚至控制信号精度。本文描述了热电偶调理模块的设计,对小信号进行隔离放大,有效抑制热强度试验存在的干扰,提高了系统的精度。     

Mathematical modeling of contact thermocouple

The contact thermocouples introduce method errors into the thermal test results. The influence of the parameters, like the density of the incident thermal flux, the inaccuracy of the thermocouple position in the investigated construction element groove, and thermal characteristics of the groove materials, on the method error is given. The obtained results allow the increase of the precision of temperature measurement at the construction unit thermal tests. The text was submitted by the authors in English.     

工作于非标准环境下体吸收型激光能量计的研制

研究了能直接工作于非标准环境下的体吸收型激光能量计.由能量计热传导、热对流、热辐射的单位时间热交换方程推导出单位时间内能量计升温过程中热能损失的数学模型,根据数学模型对能量计整个升温过程的热损失进行补偿,使得能量计对于不同脉冲长度入射激光的测量结果重复性由4.7%提高到了0.6%,消除了能量计热损失给测量带来的不利影响.针对环境温度从-40℃变化到70℃测温用铜-康铜热电堆对1℃温差响应电压剧增30%的问题,在环境试验箱进行不同环境温度下的激光能量测量实验,得出了能量计不同环境温度下测量结果的修正系数,并利用最小二乘法建立了修正系数同环境温度之间的函数关系,使得环境温度对测量结果的影响得到了修正.     

Investigating the thermal conductivity of materials by analyzing the temperature distribution in diamond anvils cell under high pressure

Investigating the thermal transport properties of materials is of great importance in the field of earth science and for the development of materials under extremely high temperatures and pressures. However, it is an enormous challenge to characterize the thermal and physical properties of materials using the diamond anvil cell (DAC) platform. In the present study, a steady-state method is used with a DAC and a combination of thermocouple temperature measurement and numerical analysis is performed to calculate the thermal conductivity of the material. To this end, temperature distributions in the DAC under high pressure are analyzed. We propose a three-dimensional radiative-conductive coupled heat transfer model to simulate the temperature field in the main components of the DAC and calculate in situ thermal conductivity under high-temperature and high-pressure conditions. The proposed model is based on the finite volume method. The obtained results show that heat radiation has a great impact on the temperature field of the DAC, so that ignoring the radiation effect leads to large errors in calculating the heat transport properties of materials. Furthermore, the feasibility of studying the thermal conductivity of different materials is discussed through a numerical model combined with locally measured temperature in the DAC. This article is expected to become a reference for accurate measurement of in situ thermal conductivity in DACs at high-temperature and high-pressure conditions.     

Modelling of the plasma-substrate interaction and prediction of substrate temperature during the plasma heating

Temperature of the substrate during plasma heating and spraying plays an important role on quality of the substrate and coating. In this study a three dimensional numerical model is developed to simulate the Ar-N₂ plasma jet and conjugate heat transfer between plasma and substrate. The influencing of operating parameters on thermal flux from the plasma to the substrate and substrate temperature are discussed. Transient simulations are carried out to predict the substrate temperature with heating time. The arc current, gas flow rate, stand-off distance, substrate material and environment around the substrate significantly affect the thermal flux to the substrate. Heat flux to the substrate cannot be neglected in the coating built-up models. Present model is validated by comparing the results of present model with previous predictions and measurements.