Research On Concentration Measurement Of Hydroxyl Radical In Pressurized Premixed Flame Using Planar Laser-induced Fluorescence

In this paper,a method of quantitative measurement of the concentration distribution the flame was de veloped by using the laser spectroscopy technique combined with numerical modeling method.In order to meet the industrial need for the distribution of flame components in high-pressure environment,this method can be applied in high-pressure environments in engineering environments rather than in laboratory environments,By analyzing and deducing of the expression of the fluorescence signal,whe n measuring the hydroxyl group(OH group),the intensity of the fluorescence signal can be simplified.It was concluded that,in a certain temperature range,the intensity of the fluorescence signal is proportional to the concentration of OH groups of interest,by selecting the appropriate excitation level and ensuring the same fuel,pressure,and equivalent ratio.Further analysis provided the quantitative measurement of the concentration of OH groups,PLIF technique was then applied to measure the flame fluorescence intensity under high pressure,and we got the experimental results,by combined with chemical kinetics modeling,obtained calibration factor.This calibration factor was obtained under steady-state conditions.In order to fully promote the practicability of the calibration factor and make it more widely used in the project,this calibration factor can be used in turbulence flames,such as during ignition.By measuring the intensity of the fluorescence signal during the ignition process,the OH group concentration can be reversed,the process is simple and easy to operate.In order to obtain the chemical kinetics simulation results of the calibrated flame used in this paper,the numerical calculation software CHEMKIN,which has a high degree of recognition in the field of combustion,was chosen to calculate the calibration flame,and the perfect GRI-Mech3.0 mechanism was selected.The accuracy of CHEMKIN calculation was analyzed before the core calculation was carried out.The calculation result of this paper was compared with the calculated data in the published literature,which proves the feasibility and accuracy of this paper.When the calibration of flame was carried out by plane laser induced fluorescence technique,and the OH-PLIF(Planar Laser-Induced fluorescence of Hydroxyl)fluorescence signal with higher signal-to-noise ratio was obtained.The image was processed to obtain the fluorescence intensity distribution in the axial direction.By Combining with the results calculated by CHEMKIN,the fluorescence signal images were processed to obtain the calibration factor at the flame front.The concentration of OH in the experiment was determined by using the calibration factor,and the similarity,which was obtained by comparing with the theoretical calculation results.Finally,the OH concentration distribution images were reproduced by the calibration constant,which is consistent with the published results in the same condition.