| The real-time accurate measurement of gas distribution is effective method in controlling the fuel combustion, optimizing the combustion process, reducing the pollutant emission and improving the utilization ratio of energy. Therefore-the research on the feasible method applying to reconstruct gas distribution in combustion is very important.With the advantages of fast response time, low detection limit, non-intrusive, no pollution and multi-parameters measurement, tunable diode laser absorption spectroscopy (TDLAS) has been widely used. The measurement system of single light system based on TDLAS is also used to measure the temperature and concentration in industrial combustion. Traditional TDLAS is a path integrated one-dimensional line-of-sight (LOS) measurement of gas properties made along the optical path. In order to realize on-line spectrum measurement of gas cross section distribution in the combustion process, we combine TDLAS technology with the Computed Tomography (CT) to form tunable diode laser algebra technique (TDLAT).In this study, we use H2O as target molecule to measure the temperature and concentration distribution, because that the H2O is abundant by-product generated in combustion process, and the technique of TDLAT has been theoretically researched and testified. The two-dimensional reconstruction of the gas temperature and concentration distribution was realized by the horizontal and vertical directions of light path and multi-angle parallel beam. The method was also evaluated by the error between the preset field distribution and the reconstruction, and was estimated by the different peak position and the magnitude of the peak distribution model simulated. Finally, in the field of the temperature reconstruction, the selected spectra were analyzed, and the results shown that the error of reconstruction dependent on the relative sensitivity of spectra. As a result the technique of TDLAT could be applied in the temperature and concentration reconstruction in combustion diagnosis.Experimentally, integrated absorption ratio of selected spectra (R(T)) in the interested temperature range that is obtained at the wavelength range of 7164.6cm-1 and 7166.4cm-1 by the experiment device of single temperature measurement. We obtain the spectral absorption signal of ten light path in the two orthogonal direction above the plane at a certain height, by the experiment device of flat flame furnace combustion gas reconstruction, finally using CT algorithm to realize reconstruction the gas distribution. Due to the limitation of the size of the detector, under the condition of the detector which are packed closely, the overall reconstruction area of the light path of 5*5 is 250 mm* 250 mm. The reconstruction area included combustion flame furnace of 60 mm diameter. Combustion flame furnace is placed in the different position of target area, two-dimensional distribution of the temperature and concentration has also been rebuilt. And also reconstruction the distribution of gas by changing the number of light path and the ratio of gas flow in flame furnace. Finally, on the basis of the above research, we analyze the stability of the combustion flame furnace applying the real-time acquisition of multiple sets of experimental data. From the results of the experiment, the reconstruction of the position and concentration of temperature range and the actual experimental environment has a certain consistency, which identifies the feasibility of combining tunable semiconductor laser absorption spectrum and calculated tomographic scanning to reconstruct the two-dimensional distribution of combustion by-products vapor temperature and concentration. |
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