颗粒浓度和光学厚度对火焰温度场重建的影响

Effects of particle concentration and optical thickness on flame temperature field reconstruction

利用彩色CCD摄像机重建火焰三维温度场分布是一项具有广泛应用前景的研究课题。目前,此项研究的重点集中于在假设燃烧中颗粒的浓度已知的条件下,求取温度的分布。但是,这样的模型没有考虑到火焰中颗粒的浓度(对应于光学厚度)对测量带来的影响。基于CCD摄像机得到的辐射能图像,本文利用三维吸收、发射和各向异性散射介质温度场重建的模型,根据燃煤锅炉数值计算结果,主要考察了颗粒浓度和光学厚度对温度场重建的影响。采用最小二乘QR分解(LSQR)对重建方程进行了求解,较好的克服了重建问题的病态性对结果的影响。结果表明,在一定的颗粒浓度范围内,随着颗粒浓度和光学厚度的增大,重建误差呈现了开始稍微减小然后又增大的趋势,重建温度场总体上能够较好的再现假设温度场的特征。

Three-dimensional flame temperature reconstruction based on CCD camera is the study that has wide application prospect. Now this study is focused on temperature field reconstruction under the assumption that particle concentration in the combustion system is known. But the effects of particle concentration （corresponding to optical thickness） on the measurement are not considered. The study of the effects of particle concentration and optical thickness on the temperature field reconstruction was performed in the paper. Three-dimensional temperature field reconstruction model in absorbing, emitting and anisotropically scattering medium was used based on radiative energy images captured by CCD camera. Least square QR decomposition （LSQR） method was introduced to solve the reconstruction matrix equation and it can overcome the effects of ill-posed characteristics of the reconstruction problem on the results. Results show that in the certain range of particle concentration, as the increase of particle concentration and optical thickness, the reconstruction error firstly decreased and then increased and reconstructed temperature field can reproduce the assumed temperature field well.