Determination of flame characteristics in a low swirl burner at gas turbine conditions through reaction zone imaging

Chemkin;LIF modeling;LSB;CH PLIF;Swirl combustor

Periagaram, Karthik Balasubramanian ; Aerospace Engineering

University:Georgia Institute of Technology

Department:Aerospace Engineering

关键词: Chemkin;    LIF modeling;    LSB;    CH PLIF;    Swirl combustor;   

Others  :  https://smartech.gatech.edu/bitstream/1853/45828/1/periagaram_karthik_b_201212_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

This thesis explores the effects of operating parameters on the location and shape of liftedflames in a Low Swirl Burner (LSB). In addition, it details the development and analysis ofa CH PLIF imaging system for visualizing flames in lean combustion systems. The LSB isstudied at atmospheric pressure using LDV and CH PLIF. CH* chemiluminescence is usedfor high pressure flame imaging.A four-level model of the fluorescing CH system is developed to predict the signal intensityin hydrocarbon flames. Results from imaging an atmospheric pressure laminar flame are usedto validate the behavior of the signal intensity as predicted by the model. The results showthat the fluorescence signal is greatly reduced at high pressure due to the decreased numberof CH molecules and the increased collisional quenching rate. This restricts the use of thistechnique to increasingly narrow equivalence ratio ranges at high pressures. The limitationis somewhat alleviated by increasing the preheat temperature of the reactant mixture. Thesignal levels from high hydrogen-content syngas mixtures doped with methane are found tobe high enough to make CH PLIF a feasible diagnostic to study such flames. Finally, themodel predicts that signal levels are unlikely to be significantly affected by the presence ofstrain in the flow field, as long as the flames are not close to extinction.The results from the LSB flame investigation reveal that combustor provides reasonablyrobust flame stabilization at low and moderate values of combustor pressure and referencevelocities. However, at very high velocities and pressures, the balance between the reactantvelocity and the turbulent flame speed shifts in favor of the former resulting in the flamemoving downstream. The extent of this movement is small, but indicates a tendency towardsblow off at higher pressures and velocities that may be encountered in real world gas turbineapplications. There is an increased tendency of relatively fuel-rich flames to behave likeattached flames at high pressure. These results raise interesting questions about turbulentcombustion at high pressure as well as provide usable data to gas turbine combustor designersby highlighting potential problems.