Research On Temperature Measurements By Two-line PLIF In Flame

In order to study the combustion mechanism of gas turbines,improve combustion efficiency and reduce pollution emissions,certain measurement techniques are needed to study the combustion field inside the gas turbine.The development and research of flame temperature measurement and measurement technology is of great significance both for the theoretical basis of the combustion process,for the development of new combustion engines,and for the study of the gas turbine’s excellent characteristics.The qualitative or quantitative determination of the flame temperature and its distribution has an important guiding role for the in-depth understanding of the intrinsic characteristics of various combustion processes,combustion flow fields and combustion products,the establishment of a reasonable combustion model and accurate computer numerical simulation.In this paper,the dual-line hydroxy-laser-induced fluorescence technique(twoline OH-PLIF)is applied to measure the temperature distribution in methane/air laminar premixed planar flame under atmospheric pressure.The dual-line PLIF temperature measurement not only can avoid the influence of free radical concentration and fluorescence quenching,but also has high time and spatial resolution.It is of great significance for the study of flame combustion mechanism and process,development of more efficient,low-pollution combustion technology.Firstly,this paper systematically analyzes the theory of two-wire temperature measurement technology,briefly analyzes the influencing factors and error sources of the experimental calibration constants,and combines the theoretical analysis with LIFBASE simulation software to study the application of the two-line PLIF temperature measurement experiment.The laser wavelength calibrated electronic transitions and vibration-transfer levels.Secondly,a two-line PLIF temperature measurement experiment system is designed to set the instrument parameters used in the experiment.By measuring and collecting the output energy of the dye laser in real time,the energy of the experimental laser can be obtained synchronously during the temperature measurement experiment.The method of keeping the output wavelength of the laser accurately is studied.The wavelength drift of the laser is calibrated by comparing the intensity of the OH-PLIF signal;a wavelength monitoring system is designed to realize the direct observation of the wavelength drift of the output wavelength of the laser;The output energy distribution was tested and analyzed to correct the collected fluorescence signal.Finally,a single point flame temperature of 1.5 cm in the axial direction of the burner was measured using a thermocouple.The result was 1232.2±3.3 K.The flame temperature was simulated using the combustion dynamics simulation software.The highest burner output was 2000.19 K;Two-line OH-PLIF temperature measurement experiment was carried out.The OH radicals in the laminar premixed plane flame with a lasing excitation ratio of 1.0 were selected.The corresponding PLIF images were acquired and the OH-PLIF images were obtained.The axial distribution of the fluorescence was calculated,and the calibration constants of the three rotating excitation lines were calculated;the single-point temperature result errors obtained by the laser energy monitoring were compared.When the rotational excitation lin e combination is Q2(11)-P1(7),it is found that the relative error of flame temperature results calibrated using thermocouple and combustion dynamics software after laser energy correction is reduced by 5.11% and 8.04%,respectively;Two-dimensional temperature distribution in a flame with an even calibration condition and radial temperature distribution at a height of 1.5 cm.