【作者】 艾青；

【导师】 夏新林；

【作者基本信息】 哈尔滨工业大学 ， 工程热物理， 2009， 博士

【摘要】 在许多涉及热传递与流动的工程技术中,热辐射与对流换热往往同时存在、相互影响,形成辐射与对流耦合换热,对过程的进程与特性产生重要影响。辐射与高速流耦合换热不仅涉及热辐射、对流换热两种基本传热方式的相互作用,而且涉及传热、流动、传质等几种物理过程的复杂耦合关系。目前,对辐射与高速流耦合换热的过程机制、特性规律与影响因素还缺乏足够的研究认识。随着航空航天技术的发展,热辐射与高速流的耦合换热研究正变得越来越重要。本文在研究复杂形体及介质内热辐射传输求解方法的基础上,建立了高速流场与复杂结构的传热耦合模型;采用数值模拟的方法,研究了复杂结构表面高速流、通道内高速两相燃气流、通道内超临界流三类不同的辐射与高速流耦合换热问题。主要研究内容包括以下四个方面:(1)热辐射传输求解的蒙特卡罗方法研究。针对蒙特卡罗法适应性强,但计算与存贮量大的特点,从提高计算效率、解决大光学厚度计算存贮需求两方面开展了蒙特卡罗法改进研究。发展完善了吸收、散射性介质中辐射传输的双向蒙特卡罗法(BDMC);提出了求解大光学厚度介质中热辐射传输的移动区域蒙特卡罗法(MCMD);编制了计算程序。对双向蒙特卡罗法,将纯随机抽样(SPS)、比率抽样(PPS)与热辐射传输的特点相结合,导出了均匀及非均匀介质的辐射传递系数,从误差分析与性能参数两方面,研究了该方法计算性能。对移动区域蒙特卡罗法,建立了该方法的实施模型,分析了计算域与人工边界对计算精度的影响。为复杂条件与大光学厚介质内的耦合换热研究提供了热辐射传递数值求解手段。(2)复杂形体的高速流与表面辐射耦合传热研究。对于热边界条件随热交换过程动态变化的耦合传热过程,通过建立边界面热流函数库,实现了流场和结构传热的解耦计算;采用区域分解思想结合边界面热流函数库,建立了大型复杂形体的高速对流与表面辐射耦合传热模型。采用商用CFD软件结合蒙特卡罗法与热网络法,对高速飞行器整体瞬态热分析进行了数值模拟研究,考察了耦合换热中各种参数的作用特性与影响程度。(3)通道内非均匀参与性介质的热辐射与高速流耦合换热研究。建立了组分热物性、液滴蒸发与辐射换热的计算模型,编制了计算模块。通过与商用软件FLUENT结合,数值模拟了通道内两相燃气流中的热辐射与高速流耦合传热。通过对温度场、液相浓度和壁面热流分析,分析了壁面及介质热辐射特性的影响;比较了不同壁面热边界条件对通道内热环境的影响;结合超音速燃烧室的热设计,建立了热边界非均匀温度分布模型,探讨了影响热环境的主要因素及其作用特性。(4)高温冷却通道内耦合传热研究。针对高温燃烧室的热防护,采用有限体积法结合蒙特卡罗法及对流换热实验关联式,数值模拟了高温冷却通道内超临界燃料液体的辐射与对流耦合换热,分析了热辐射的作用及影响因素。基于高温燃烧室的非均匀热流条件与冷却结构材料特性,提出了以壁面温度控制为约束的高温冷却面板热设计方法,分析了该方法的可靠性。通过本文研究,建立了热辐射与高速流耦合换热的数值模拟方法,对热辐射与高速流的三类耦合换热过程形成了比较深入细致的认识,得出了一些对工程应用有价值的结论与解决方案。更多还原

【Abstract】 In many engineering fields related to high temperature heat transfer and flow, thermal radiation and convection usually take place simultaneously and to form coupled heat transfer of radiation and convection. This coupled thermal behavior will cause an important impact on the process characteristics. In a coupled radiation and high-speed flow heat transfer process, not only the interaction of thermal radiation and convection heat transfer but also the combination of heat transfer, fluid flow and mass transfer are involved. So far, our knowledge on mechanism, characteristics and influencing factors of coupled radiation and high-speed flow heat transfer is far from the requirement of developing new technologies in aviation and aerospace engineering fields. The research on coupled thermal radiation and high-speed flow heat transfer is becoming important.On the basis of investigating numerical methods of thermal radiation transfer in participating medium with complex geometry, the analytical model for coupled heat transfer of high-speed flow field with complex structures is established. Three kinds of coupled heat transfer problems of high-speed flow with thermal radiation have been investigated by numerical simulation, which are that on complex structure surface, that in high-speed two-phase channel flow and that in supercritical channel flowThe main work of in this dissertation includes the following four aspects.(1) Investigation on the Monte Carlo method for solving thermal radiation transfer problems. The Monte Carlo method is flexible to complex problems, but it costs large amount of memory space and computational time. Aiming at those characteristics, investigations on elevating the computational efficiency and on diminishing memory request are conducted. As a results, the Bidirectional Monte Carlo method (BDMC) for solving radiative heat transfer in absorbent and scattering medium is improved and a Monte Carlo method with mobile domain (MCMD) is put forward to solve the thermal radiation in medium with large optical thickness, and the computational programs for those two kinds of Monte Carlo methods are developed.For the Bidirectional Monte Carlo method, the characteristics of thermal radiation transfer is combined with the simple random sampling (SPS) and the probability sampling proportionate to size (PPS) respectively to derive the radiative transfer coefficients, which are used for the homogeneous medium and inhomogeneous medium, respectively. The computational performance of the method is evaluated by error analysis and comparison of performance parameters.For the Monte Carlo method with mobile domain, the numerical model and implementation scheme is established and the influences of computational domain and artificial boundary on calculation accuracy are analyzed numerically. All of that provided a powerful method of solving thermal radiation transfer, which is needed for analyzing coupled heat transfer in large optical thickness media.(2) Investigation on the coupled heat transfer of surface radiation with high–speed flow across complex shape of bodies. For the heat transfer process with transient coupled thermal boundary conditions, the concept of wall heat flux function is introduced to decouple the calculation of heat transfer in solid structure from that of the flow field. By employing the domain decomposition calculation and resorting to the heat flux functions database of bounding surface, the analysis model for the coupled heat transfer of surface radiation with high–speed flow across complex shape of bodies is developed. A commercial CFD software is combined with the Monte Carlo method and thermal network method to simulate the transient coupled heat transfer of a high-speed aircraft numerically, and the effects of various parameters are analyzed.(3) Investigation on the coupled heat transfer of thermal radiation with high-speed flow of non-uniform participating medium in channels. By combining FLUENT software with programs for calculating thermal properties, droplet evaporation and radiation heat transfer, numerical simulation of the coupled heat transfer of thermal radiation with high-speed flow of non-uniform participating medium in channels was carried out. By analyzing the temperature field, the liquid phase concentration and the wall heat flux, the influences of thermal radiation properties were investigated. For the thermal design of supersonic combustion chamber, the influence of wall boundary condition was analyzed to give the thermal boundary model with non-uniform temperature distribution. The flexibility of this model for supersonic combustion chamber and the main factors affecting the thermal environment in supersonic combustion chamber were discussed.(4) Investigation on coupled heat transfer in high-temperature cooling channel. For the thermal protection of high-temperature combustion chamber, the Monte Carlo method and the experimental correlations for convection heat transfer were used to numerically simulate the coupled radiation and convection heat transfer of supercritical fuel liquid in a high-temperature cooling channel. The effects of thermal radiation were analyzed and the thermal design method for cooling panel was presented based on the allowed temperature of materials and the non-uniform distribution of heating flux. The reliability of the design method is examined numerically. By the investigations in this thesis, the numerical methods have been developed to analyze the coupled heat transfer of thermal radiation with high-speed flow. The detailed knowledge on the three kinds of coupled heat transfer was obtained, which can give some valuable conclusions and design references.更多还原