三维燃烧介质和壁面温度的非接触联合重建研究

温度分布在线实时测量对于燃烧过程优化和污染物控制具有重要意义, 针对以往非接触三维温度分布重建过程的耗时性问题和忽略壁面辐射的不足, 本文提出了一种新的离散重建模型, 用于三维吸收、 发射和散射性高温燃烧介质以及壁面温度的快速联合非接触测量. 该模型以四个CCD(Charge Coupled Device) 为测量传感器, 通过构建辐射逆问题求解方程, 从CCD输出的辐射投影图像重建温度分布. 介质中不同投影方向内的辐射传递过程通过离散传递法来描述, 介质的散射和壁面反射则通过离散坐标法来近似. 离散后计算局部辐射强度的病态方程通过最小二乘余量法来求解, 论文对其计算速度进行了优化. 通过非对称温度分布测量算例分析了该模型的有效性, 讨论了测量噪音、 介质和壁面辐射特性对重建精度的影响, 并与其他方法对比分析了模型的重建速度. 计算结果表明本文提出的离散模型可以有效地用于大型高温燃烧介质和壁面温度分布的联合非接触测量. 即使在有噪声的情况下, 该模型也能获得准确的测量结果, 与其他计算方法相比, 采用改进的最小二乘余量法, 能有效地提高温度分布的重建计算速度.

Research on simultaneous reconstruction of the temperature distribution of a 3D participating medium and its boundary

In-situ and nonintrusive 3D temperature measurement is very important for combustion diagnosis and controlling of pollutants. The temperature reconstruction technique based on radiation inverse analysis has received intensive attention. In order to reduce the computation cost and take boundary temperature into consideration, a discrete method is presented for 3D temperature distribution determination for an absorbing, emitting and scattering combustion medium and its boundary by using the emission image measured by four CCD cameras. First the radiative source term is retrieved through the discrete transfer method. Then, the temperature is inferred from the blackbody intensity obtained by subtracting the media scattering and boundary reflecting contribution from the source term by the discrete ordinate approximation. The least squares minimum residual algorithm is improved to solve the ill-posed reconstruction equations. The performance of the proposed method is examined by numerical test. The effects of measurement noise and radiative properties on the reconstruction accuracy are investigated. The results show that the method proposed in this paper is capable of reproducing the temperature of the medium and its boundary accurately, even with noise. The reconstruction time cost is reduced significantly compared with those of other methods.