对称与非对称碳氢火焰温度场重建实验研究

为了测量碳氢火焰的截面温度场分布,根据火焰烟黑辐射传递特性,提出了基于火焰发射辐射能图像的温度场重建模型,使用最小二乘QR矩阵分解法（LSQR法）求解该模型。数值模拟重建了轴对称和非对称分布的两类温度场,重建结果精度较高。进而对实验室的甲烷扩散火焰截面二维温度场进行了重建,结果与已有文献相比符合较好,特别是对非对称火焰,能准确还原其温度场分布特征,实验得到了较好的结果。     

利用火焰图像同时重建温度场和浓度场的试验研究

煤粉火焰图像是火焰辐射经过发射、衰减和散射等过程后到达摄像机靶面的投影。火焰发射出的辐射强度与火焰自身的温度密切相关，而辐射强度的衰减则取决于弥散介质的特性和浓度。该文首先研究了辐射衰减系数与粒子浓度场的关系，提出了对温度场和浓度场进行同时重建的控制方程。最后，在小型燥粉炉上进行断面温度场和浓度场的重建试验。图ll参l2     

基于火焰辐射图像的温度分布与浓度分布联合重建

讨论了基于火焰辐射图像的截面温度分布和碳粒浓度分布的重建测试方法。分析并建立了测试系统理模型和优化模型，设计了相应的求解算法，针对电站锅炉燃煤火焰进行了实际测试。计算结果与实际测试结果进行比较和分析，温度分布和浓度分布与模型重建结果比较接近，表明重建结果合理、可信。     

声学CT算法重建炉内三维温度场的仿真研究

为了实现炉内温度场的实时在线监测,提出了2种声学CT算法:代数重建法(ART)和同步迭代重建法(SIRT).采用2种CT算法分别对炉膛火焰分布的单峰模型、双峰模型和四峰模型进行了温度场重建仿真实验,并对2种算法的仿真结果进行了比较,分析了2种算法的抗噪声能力.结果表明:2种算法均可用于炉膛三维温度场重建且各有优劣,对于燃烧情况复杂的电站锅炉,抗噪声能力更强的SIRT算法具有更好的稳定性.     

运用代数迭代技术由火焰图像重建三维温度场

在运用图像处理的方法测量火焰温度场的研究中,从摄像机获取的二维累积图像中重建出包含每个断面温度分布的三维温度场,是关系到能否投入实际应用的关系问题,结合扇形计算机断层成像原理和火焰辐射传递方程,推导出辐射强度随投影路径衰减的控制方程。将火焰断面网格化之后,运用代数重建技术对离散方程温度和辐射衰减系数同时迭代求解。在油煤混烧的燃烧器上运用该方法进行实验研究,并结合算法的数值模拟,对其可能误差和改进方     

模型燃烧室壁面与火焰温度光学测量方法研究

为研究燃气轮机燃烧室壁面温度与火焰燃烧的关系,实验研究了模型燃烧室壁面温度发生改变前后火焰的燃烧特性.采用磷光测温技术对壁面温度进行测量,利用辐射层析技术结合双色测温法对火焰的三维结构及温度场进行了重建.实验时壁面温度在200℃附近,火焰的温度范围是1 500～2 000 K.实验结果表明:当气流冲击壁面时,壁面温度发...     

基于炉内火焰辐射图像的断面温度场的重建方法研究

讨论了面向炉膛火焰的基于辐射图像的三维断面温度场测量;在分析了测量的辐射物理模型的基础上,提出了优化重建模型,进而提出了将罚函数法、模拟退火法、单纯形法结合起来的切实可行的重建算法。并在某电厂的锅炉上者了验证性的试验。     

火焰参数对辐射图像法不同测温模型的影响

对火焰温度分布的实时测量能够了解燃烧过程、验证燃烧机理、预防工业事故、优化燃烧设备。图像法测温在工业现场的火焰三维温度测量上有明显的优势,但通常均考虑火焰为均匀折射率介质,给测温结果带来了不可避免的误差。本文建立了梯度折射率介质下火焰的辐射成像模型和图像法测温模型,验证了方法的正确性,分析了火焰尺寸对成像的影响及炭黑颗粒浓度对温度场重建的影响。得出随着火焰尺寸的增大,图像强度随火焰尺寸出现先增大后减小的趋势,梯度介质模型与均匀介质模型的差异逐渐增大,随着炭黑颗粒浓度的增加,两种模型的重建精度逐渐下降。     

炉膛燃烧温度场三维可视化监测方法模拟研究

为了利用火焰图像监测装置检测到的炉膛燃烧辐射能分布图像信息重建三维燃烧温度场，作者提出了一种针孔成像条件下的快速方法计算CCD（Charge-Coupled Device，电荷耦合器件）靶面接收的辐射能。成像像素接收到的系统网格单元的辐射能的份额的计算结果和辐射能图像计算结果均体现了成像过程的方向选择性和辐射能传递规律的作用。针对炉膛燃烧三维温度场重建的严重病态问题建立了一种基于Tikhonov正则化的求解方法，对于单峰型三维温度分布重建模拟计算结果表明，即使辐射图像检测包含均方差达到0.11的误差，温度场重建误差仍能维持与测量误差基本相当的水平，温度分布可视化质量较高，各种图像检测组合方式的重建结果比较显示，炉膛四角沿高度方向每隔5m左右交叉对角布置两个辐射图像采集装置，能够获得较好的全炉膛温度场可视化结果。     

燃煤气单元玻璃熔窑火焰空间数值模拟

通过建立火焰空间三维数学模型来模拟燃煤气单元玻璃熔窑火焰空间内的流动、燃烧、传热等过程。针对煤气的燃烧特点，单元窑的火焰特征等进行了较深入的研究。结果表明，该三维数学模型能够比较全面地反映火焰空间速度场、温度场分布的规律；模型具有通用性好，不易受环境波动影响的优点，具有一定的实用意义。     

GREEN'S FUNCTION APPROACH TO THREE-DIMENSIONAL HEAT CONDUCTION EQUATION OF FUNCTIONALLY GRADED MATERIALS

A Green's function approach based on the laminate theory is adopted to solve the three-dimensional heat conduction equation of functionally graded materials (FGMs) with one-directionally dependent properties. An approximate solution for each layer is substituted into the governing equation to yield an eigenvalue problem. The eigenvalues and the corresponding eigenfunctions obtained by solving an eigenvalue problem for each layer constitute the Green's function solution for analyzing the three-dimensional transient temperature. The eigenvalues and the corresponding eigenfunctions are determined from the homogeneous boundary conditions at outer sides and from the continuous conditions of temperature and heat flux at the interfaces. A three-dimensional transient temperature solution with a source is formulated by the Green's function. Numerical calculations are carried out for an FGM plate, and the numerical results are shown in tables and figures.     

THERMAL BENDING ANALYSIS OF COMPOSITE LAMINATED CYLINDRICAL SHELLS USING A REFINED FIRST-ORDER THEORY

The problem of deducing two-dimensional theory from three-dimensional theory for a thermoelastic isotropic body is investigated. Based on thermoelasticity theory, the refined plate theory is derived by using Biot's solution of thermoelasticity and Lur'e method without ad hoc assumptions. For the homogeneous boundary conditions, the exact equations and solutions are derived and the equations can be decomposed into four governing differential equations: the biharmonic equation, the shear equation, the transcendental equation and the temperature equation. Moreover, the approximate equations and solutions for the plate under anti-symmetrical transverse loadings and temperature distribution are derived directly from the refined plate theory. By omitting coupling effect and higher-order terms, the refined plate theory can be degenerated into other well-known elastic and thermoelastic theoretical models.     

Optimal configuration of discrete heat sources in a vertical duct under conjugate mixed convection using artificial neural networks

This paper reports the results of a numerical investigation of the problem of finding the optimum configuration for five discrete heat sources, mounted on a wall of a three-dimensional vertical duct under mixed convection heat transfer, using artificial neural networks (ANN). The objective is to locate the positions for the five heat sources in such a way that the maximum temperature of any of the heat sources in a given configuration is a minimum. The three-dimensional governing equations of mass, momentum and energy equations for the fluid flow and the energy equation for the solid regime have been solved by using FLUENT 6.3 and a database of temperature versus configuration was generated. The temperature database developed from CFD simulations is used to train the neural network. The trained neural network predicts the temperature of the heat sources very accurately and much faster than the CFD software. With the use of this network, an exhaustive search for all possible configurations was done that resulted in a global optimum for the problem.     

Mixed convection heat transfer in horizontal rectangular ducts with radiation effects

The study of mixed convection heat transfer in horizontal ducts with radiation effects has been numerically examined in detail. This work is primarily focused on the interaction of the thermal radiation with mixed convection for a gray fluid in rectangular horizontal ducts. The vorticity–velocity method is employed to solve the three-dimensional Navier–Stokes equations and energy equation simultaneously. The integro-differential radiative transfer equation was solved by the discrete ordinates method. The attention of the results is focused on the effects of thermal buoyancy and radiative transfer on the development of temperature, the friction factor and the Nusselt number. Results reveal that radiation effects have a considerable impact on the heat transfer and would reduce the thermal buoyancy effects. Besides, the development of temperature is accelerated by the radiation effects.     

Novel approach to the solution of temperature distribution in thestator of an induction motor

In this paper a three-dimensional thermal model of an induction motor is presented. Excepting for providing a more accurate representation of the problem, the proposed model can also reduce computing costs. The finite element method is used to solve the three-dimensional steady-state and/or transient heat flow equation which describes the thermal model. A temperature-time method is employed to evaluate the distribution of loss in various parts of the machine. Using these loss distributions as an input for finite element analysis, more accurate temperature distributions can be then obtained. The validity and accuracy of the proposed method are checked by comparing the results with those obtained from test     

Analytical solution for a transient,three-dimensional temperature distribution due to a moving laser beam

This paper presents an analytical solution of the transient temperature distribution in a finite solid when heated by a moving heat source. The analytical solution is obtained by solving the transient three-dimensional heat conduction equation in a finite domain by the method of separation of variables (SOV). Meanwhile previous studies focus on analytical solutions for semi-infinite domains, here an analytical solution is provided for a finite domain. The non-homogeneous equation is solved by using the Laplace transform for a unit impulse and then convoluted with the actual heat source. Two different distributions are used: a Gaussian distribution and a spatially uniform plane heat source.     

Simulation of SOFC performance using a modified exchange current density for pre-reformed methane-based fuels

Numerical simulations can be used to visualize and better understand various distributions such as gas concentration and temperature in solid oxide fuel cells (SOFCs) under realistic operating conditions. However, pre-existing models generally utilize an anode exchange current density equation which is valid for humidified hydrogen fuels – an unrealistic case for SOFCs, which are generally fueled by hydrocarbons. Here, we focus on developing a new, modified exchange current density equation, leading to an improved numerical analysis model for SOFC anode kinetics. As such, we experimentally determine the exchange current density of SOFC anodes fueled by fully pre-reformed methane. The results are used to derive a new phenomenological anode exchange current density equation. This modified equation is then combined with computational fluid dynamics (CFD) to simulate the performance parameters of a three-dimensional electrolyte-supported SOFC. The new modified exchange current density equation for methane-based fuels reproduces the I–V characteristics and temperature distribution significantly better than the previous models using humidified hydrogen fuel. Better simulations of SOFC performance under realistic operating conditions are crucial for the prediction and prevention of e.g. fuel starvation and thermal stresses.     

Inverse radiation problem of temperature field in three-dimensional rectangular enclosure containing inhomogeneous,anisotropically scattering media

An inverse radiation analysis is presented for determining the three-dimensional temperature field in an inhomogeneous, absorbing, emitting and anisotropically scattering media of known radiative properties from the knowledge of the exit radiative energy received by charge-coupled device (CCD) cameras at boundary surfaces. The forward Monte Carlo method was employed to describe the radiative energy propagation. The inverse problem was formulated as an ill-posed matrix equation and solved by least square QR decomposition (LSQR) method. The measured data were simulated by adding random errors to the exact solution of the direct problem. The effects of measurement errors, combinations of CCD cameras, concentration distributions of particles, and coefficient fluctuating errors on the accuracy of the inverse problem were investigated. The results show that the three-dimensional temperature field can be estimated accurately, even for the noisy data.     

EXACT THERMOELASTIC SOLUTION FOR AN AXISYMMETRIC PROBLEM OF THICK CLOSED LAMINATED SHELLS

Giving up any assumptions about displacement models and stress distribution, the mixed state equation for the axisymmetric problem of thick closed orthotropic cylindrical shells is established. An exact three-dimensional solution of a thick closed laminated shell subjected to mechanical loading, temperature variation, and transient thermal loading is presented. Every equation of elasticity can be satisfied, and all elastic constants can be taken into account. Some numerical results are obtained and compared with those calculated using SAPS.     

Thermo-Mechanical Bending of Functionally Graded Plates

In this work the deformations of a simply supported, functionally graded, rectangular plate subjected to thermo-mechanical loadings are analysed, extending Unified Formulation by Carrera. The governing equations are derived from the Principle of Virtual Displacements accounting for the temperature as an external load only. The required temperature field is not assumed a priori, but determined separately by solving Fourier's equation. Numerical results for temperature, displacement and stress distributions are provided for different volume fractions of the metallic and ceramic constituent as well as for different plate thickness ratios. They correlate very well with three-dimensional solutions given in the literature.