【作者】 杜胜华；

【导师】 夏新林；

【作者基本信息】 哈尔滨工业大学 ， 工程热物理， 2010， 博士

【摘要】 作为热量传递的三种基本方式之一,热辐射广泛存在于热能、动力与推进、太阳能利用、化工、材料制造、飞行器热控制与热防护等技术领域,并以不同的形式与导热、对流传热方式耦合,形成热量的传递和交换。另一方面,热辐射是由于热的原因而产生的电磁波,作为可见光和红外波段的探测信号,在光学测量、红外探测和遥感等领域得到广泛应用。其传播过程是一种具有光谱特征和特定空间分布的辐射能量在复杂背景和干扰环境中的定向传输行为,涉及复杂的几何系统、结构辐射特性和温度场。因此,热辐射调控与辐射定向传输问题研究具有重要的应用价值和学科交叉性理论意义。本文以高温热防护与空间红外探测两类技术领域为主要应用背景,通过机理模型分析、计算方法研究和数值模拟,对高温材料表面的热辐射调控特性和空间红外探测中的辐射定向传输特性进行了研究。首先对求解热辐射传递的蒙特卡罗法进行了改进研究。针对空间红外探测等定向传输系统复杂、几何尺度变化大、多辐射源的特点,研究了正反双向分段计算与蒙特卡罗法相结合的辐射定向传输计算方法,通过算例分析,验证了该方法相对于传统蒙特卡罗法的优越性。针对高温陶瓷材料内热辐射计算网格与导热计算网格疏密性要求的差异,开展了辐射换热源项的求解方法研究,构造了局部辐射网格法,通过计算比较,考察了计算方法的适用性及相关参数的影响。从介质辐射传递理论出发,考虑材料服役过程中的温度场,结合界面反射和折射关系,建立了高温陶瓷材料的表面发射率计算模型。基于该模型,采用反向蒙特卡罗法模拟分析了等温材料表面的热发射特性。采用双向蒙特卡罗法与控制容积法,结合谱带模型,模拟计算了气动加热下高温陶瓷材料的温度场;分析了在该温度作用下,陶瓷材料表面热辐射发射率及材料性质、表面状况和气动热流密度的影响。在上述计算方法和表面辐射特性研究基础上,从高温热防护结构内的热量输运分配和多量场耦合机制出发,建立了高温表面的两种热辐射调控系统模型。采用控制容积法、局部辐射网格法与蒙特卡罗模拟,计算分析了辐射散热调控特性及主要影响因素。以蒙特卡罗法为基础,采用正反双向分段计算,模拟了对地多光谱红外测量系统、空间目标光学探测系统、太阳能聚集系统三种辐射定向传输过程,分析了几何结构、元件辐射特性、温度以及背景环境等因素的影响。通过上述研究,掌握了表面热辐射调控与辐射定向传输特性的计算分析手段,从表面辐射特性、热量输运分配、辐射传输系统的方向性控制三个方面,深入分析了表面辐射的发射和传输调控特性,获得了细致的特性规律认识。为高温热防护和红外探测等相关技术应用,提供了必要的认识基础与理论依据。更多还原

【Abstract】 As one kind of heat transfer mechanism, thermal radiation can be found in many technical fields, such as the thermal engineering, power and propulsion, solar energy utilization, chemical engineering, material manufacturing, as well as the thermal control and thermal protection of space vehicles. It usually combines with the thermal conduction or the thermal convection by various ways to transport heat. On the other hand, thermal radiation is the electromagnetic wave caused by thermal effects. As the visible and infrared signals, it has been widely used in optical measurement, infrared detection and remote sensing technologies. In those applications, its propagating process is a kind of directional transfer behavior of the radiative energy characterized by spectral feature and given spatial distribution, which takes place in complex background and disturbing environment. The involved geometric structure, radiative properties and temperature field are usually complicated. Therefore, an investigation on the regulative characteristics of thermal radiation and the directional transfer is valuable to engineering application and theory development.In this thesis, two kinds of technical fields including the high temperature thermal protection and the spaceborne infrared detection are taken to be the main application backgrounds. The regulative characteristics of thermal radiation for high temperature material and the directional transfer of radiation in spaceborne infrared detection are investigated by the analysis of mechanism model, the development of calculation method and the numerical simulation.The Monte Carlo method to solve radiation heat transfer is improved. Aiming at characteristic of directional radiation transfer in spaceborne infrared detection caused by the complex system, the tremendous variety of geometric scale and the multi-source radiation, numerical method of forward-backward bidirectional calculation is put forward on the basis of Monte Carlo simulation. By comparing with typical cases, superiority of this method is verified with respect to traditional Monte Carlo method. Considering the different grid requirement between the thermal radiation calculation and the heat conduction solution of high temperature ceramic material, a local radiative grid method for thermal source term of radiative exchange is developed. By calculation and comparison, its applicability and effects of relevant parameter are analyzed. The calculating model of the ceramics surface emissivity in high temperature is constructed, including the temperature field in medium subjected to aeroheating as well as the reflection and refraction of the interfaces. Base on this model, the backward Monte Carlo method is used to simulate the thermal emission of the surface in isothermal ceramics. Moreover, the control volume method is combined with the bidirectional Monte Carlo method and the spectral band model to solve the temperature field of coupled heat transfer in ceramics. The effects of emissivity of surface radiation, material property, surface status as well as the effects of aeroheating are discussed.Base on above calculation method and characteristic research of surface radiation, two sorts of transporting models are put forward to regulate thermal radiation of high temperature surface from heat transport and redistribution and coupled mechanism in the thermal protection structure. The control volume method is combined with the local radiative grid method and the Monte Carlo simulation to investigate the regulative characteristics of surface thermal radiation under various conditions and main factors. The forward-backward bidirectional calculation with subsection is used to simulate the directional propagating processes in the multi-spectral infrared system for remote sensing of the earth-atmosphere, the spaceborne optical measurement system to detect moving objects in space and solar energy concentrator. The effects of the geometric structure, the radiative properties of surfaces and the temperature field as well as that of the background and environment are discussed.By the investigation, the numerical methods for thermal radiation regulating of high temperature surface and that for the directional transfer of radiation are obtained. The obtained knowledge on the emission and the regulative characteristics of surface thermal radiation is of theoretical support to the surface radiation characteristics, heat transport and redistribution and direction control of the radiation transfer systems. The understanding to radiation heat transfer of the high temperature thermal protection and the infrared detecting provides necessary base and theory reference.更多还原