背景纹影定量化在层流轴对称火焰温度场测量中的应用研究

摘要

本文以本生型甲烷／空气层流预混火焰为研究对象，研究了背景纹影技术在层流轴对称火焰温度场测量中的应用。考虑到背景尺度对窗口和相机参数的限制问题，采用了多尺度小波噪点背景。比较各类运动图像处理技术的特点，选用变分光流法获取光线穿过火焰后的偏转角。搭建实验台并进行背景纹影火焰测温实验，实验中发现，在选用多尺度小波噪点背景的情况下，由变分光流算法获得的像素位移分布图的噪声小于同等条件下由互相关算法得到的结果。最后，假设火焰呈轴对称分布，结合Gladstone-Dale公式与理想气体状态方程分别获得了甲烷火焰当量比为1．06和0．83这2种实验条件下的温度场，所获得的温度分布与Raman-LIF法的测温结果相比，趋势基本一致。%Background Oriented Schlieren (BOS)is a new type of schlieren with the advanta-ges of being simple,flexible and cheap.The application of BOS in the measurement of the lami-nar axisymmetric flame temperature field is studied with the methane/air laminar premixed flame.Random or regular noise is usually used as the background of BOS,but this would limit the interrogation area size and camera parameters.Therefore the multi-scale wavelet noise back-ground is adopted in this paper.The cross-correlation method and the variational optical flow method under the constraint condition of Horn-Schunck and Lucas-Kanade are compared.A BOS experiment platform which can generate a methane/air laminar premixed flame is built,and BOS images are obtained.The pixel shift distribution is calculated from the BOS image and the result shows that the noise of the variational optical flow method is much smaller than that of the cross-correlation method under the same condition when the multi-scale wavelet noise background is used.Finally,under the axisymmetric assumption,the temperature distribution of the flame is obtained from deflection angle using the Gladstone-Dale relationship and the ideal gas state equa-tion.In the experiment,the flame temperature fields are measured at the equivalent ratios ofφ=1.06 andφ= 0.83,respectively.It is basically consistent with the result acquired by Raman-LIF.