Application of quantitative background oriented schlieren in laminar axisymmetric flame temperature measurement

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.