Application of quantitative schlieren method in flame temperature measurement

The frame temperature is measured using ‘Z’type schlieren by standard photomet-ric method.The relationship between the grayscale value of flame schlieren image and the deflec-tion angle is established through a calibration lens.The refraction index is obtained by using axi-symmetric assumption.Then by using the Gladstone-Dale relationship and the ideal gas law,the flame temperature is obtained.The comparison of involved inversion algorithms shows that,the direct integral method and the Abel inversion method can both achieve the least error,however, the Radon inversion strongly depends on the filter function and the algebraic reconstruction de-pends on the numbers of discrete points.The temperature reconstructed by the quantitative schlieren technique is compared to thermocouple measurements.The results prove the validation of this quantitative technique.