Quantitative Measurement Of Chemiluminescence And Characterization Of Flame Properties

The chemiluminescence of flames is directly related to the combustion process,and the combustion diagnosis technology based on it has a good application prospect.However,the research mostly stays in the stage of qualitative characterization of flame characteristics by luminous intensity,which is not conducive to the real use of chemiluminescence.Therefore,it is of great significance to realize the quantitative measurement of chemiluminescence and establish the quantitative relationship between chemiluminescence and combustion characteristics.In this thesis,a quantitative measurement method of chemiluminescence based on standard light source is proposed,which is verified by the numerical simulation and experimental results of the methane-air jet diffusion flame.The results show that this method can realize the transformation from chemiluminescence intensity to radiation rate of excited radicals.On this basis,the chemiluminescence characteristics and characterization of different flames were studied.First,the jet diffusion flame with different velocity ratio is studied experimentally,and it is found that compared with the radiation distribution of CH*,OH* has one more secondary reaction zone located downstream of the flame.With the increase of velocity ratio,the reaction intensity in this area becomes weaker,while the reaction zone of OH*and CH* located in the middle and upper reaches of the flame are relatively enhanced.Second,using the GRI-Mech3.0 and the reaction mechanism of OH* and CH*,the plane premixed flame under different pressure,equivalence ratio and outlet velocity was simulated.By introducing the deep learning method,a neural network model used the number density of OH* and CH* to predict the heat release rate was established.Third,the chemiluminescence characteristics of the jet-premixed flame under laminar and turbulent conditions were investigated,and the characterization of equivalence ratio by chemiluminescence was discussed.In laminar state,the overall distribution of OH* is obviously higher than that of CH*,and the effect of turbulence makes them to be same.It is also found that with the increase of the equivalence ratio,if the axial peak value of OH* and CH* increases at first and then decreases,it is considered that the flame is in the laminar flow state,and if it increases monotonously,the flame is turbulent.In addition,a unified formula for characterizing the equivalence ratio by OH* and CH* at different velocities was obtained.Finally,the chemiluminescence characteristics of low swirl premixed flame were obtained,and the characterization of equivalence ratio and swirl number of chemiluminescence were studied.Compared with the distribution of CH*,OH* is more concentrated in the downstream of the flame,which is the same as the two jet flames.As the equivalence ratio increases,the chemical reaction tends to be intense,the position of the core reaction develops to the downstream,and the secondary reaction zone of OH* also appears downstream.With the increase of swirl number,the shape of OH* and CH* radiation distribution changes obviously.Based on this phenomenon,the fitting formulas of equivalence ratio and swirl number are obtained by using the axial peak value and distribution height of CH* radiation,respectively.