Investigation Of Combustion Instability In Syngas Combustor Of Gas Turbine

Gas turbine burning coal-derived syngas fuel is a key part of the IGCC clean coal power plant. One of the obstacles of designing ultra-low NO_X syngas combustor is combustion instability. The dissertation focuses on one of the obstacles of designing ultra-low NO_X syngas combustor, combustion instability of syngas combustor.The traditional commercial syngas heavy-duty gas turbine adopts dilution-diffusion combustion to reduce the NO_X emission to 25ppm@15%02. The combustion oscillations play the critical rule in component failure. To reach the next generation's NO_X emission control regulations of 3ppm@15%O₂, the promising ultra-low NO_X syngas combustion technologies like lean-premixed, RQL and catalytic combustion are all face the combustion instability problem. The author experimentally studied the syngas diffusion combustion instability and syngas premixed combustion instability. This dissertation is organized as follows:â‘ Mechanisms of combustion oscillation and the compare of diffuse and premixed combustion instability;â‘¡Investigation of the syngas diffusion combustion instability base on the experimental results of medium pressure full scale rig test and full pressure site test;â‘¢Investigate the syngas premixed combustion instability of model combustor.Base on the experimental results of medium pressure full scale rig test and full pressure site test, the amplitude and frequency characteristics of diffusion combustion instability are analyzed. The increase of combustor heat load can intensify the unsteadiness while the increase of nozzle pressure ratio can improve the combustor steadiness. The magnitude and frequency of combustor dynamic pressure are competition results of both two elements. The results also indicate that the frequency of combustion instability relate to geometry dimension, heat load and flow field pattern.The dependence of syngas premixed combustion instability on some parameters of combustion system is studied by experiments of atmospheric-pressure rig. The following conclusions can be achieved:â‘ The geometric form of combustor is the most important factor that affects combustion instability;â‘¡The magnitude of oscillation energy is susceptible to variety of equivalence ratio, and sometimes is affected by the flowrate of premixed gas and the mole fraction of H₂ in syngas;â‘¢The nature frequencies of combustion oscillation are related to combustor heat load;â‘£The flashback of syngas premixed combustion is found to be strong related to combustion oscillation.The mechanism of both diffusion and premixed combustion instability could be explained by Rayleigh criterion. The combustion style and the composition of fuel could have influence on combustion intensity and frequency by transfer wave energy among pressure, equivalent ratio (vortex breakdown), and heat release.