Measurement of gas temperature distributions in a test tube using spectral remote sensing

Abstract

Measurement of a temperature profile of a hot gas is made using the Spectral Remote Sensing (SRS) method. Emphasis is placed on the accuracy of the SRS method in a test furnace with intense radiation emerging from the walls. Kerosene is used as the fuel and a 2m long STS tube is employed as the test section for experimental investigation. Spectral intensities emitted from the combustion gas are measured at $7cm^{-1}$ intervals from 2045 to $2451cm^{-1}$. When viewing the hot rear wall through the hot gas, spectral intensities are generally increased by the strong emission from the wall; however, they are diminished by the gas for the range where the strong $CO_2$ absorption band exists. In calculating spectral intensity, the CK-based WNB model is used for the advantage of saving computation time without sacrificing accuracy compared with the LBL (line-by-line) method. By minimizing the error between the measured spectral intensities and the computed ones, the temperature profile along the line-of-sight is recovered. To demonstrate the SRS method, the recovered temperatures are compared with measured temperatures using thermocouples. As a result, the recovered temperature profile and measured temperatures are in good agreement within an error of 4%. Especially, the hot rear wall is found to affect the overall performance of the SRS method significantly through heavily weighted Plank distribution there. The SRS method proves to be more promising in determining the temperature distribution of the gas with a reasonable accuracy when applied to industrial furnaces with the hot rear wall.