Research On The Combustion Characteristics Of Methane/dimethyl Ether Binary Fuels In Gas Turbines

During the rapid development of gas turbine technology,exploring more efficient and energy-saving as well as low pollutant emission combustion methods has been the focus of research by experts and scholars at home and abroad.The excellent performance of binary fuel blends in CI engines has aroused interest in the application of fuel blends in gas turbines.Dimethyl ether(DME,CH3OCH3)is considered as a good fuel additive because of its high cetane number and excellent atomization and ignition performance.In this paper,based on the summary of domestic and international research progress of methane dimethyl ether binary fuel,a zero-dimensional homogeneous steady-state flame surface model is used to numerically simulate the combustion of dimethyl ether blended with different degrees of fuel in a gas turbine combustion chamber under different pressure gradients,and the temperature field,typical intermediate and final products and pollutant emission distribution in the combustion chamber are selected for comparative analysis to obtain the objective law of pressure and dimethyl ether The objective law of the effect of pressure and DME blending ratio on combustion is obtained.The results show that the combustion process is more sensitive to the effect of pressure;the addition of DME effectively improves the reactivity of methane and contributes to the pyrolysis process of the fuel;moreover,the pollutant emission index is higher with the increase of pressure under the guarantee of a certain calorific value of fuel input,but it is not sensitive to the amount of blended DME.Based on above research,the mechanism of methane/dimethyl ether chemical reaction was reduced by genetic algorithm,which could effectively enhance the calculation speed and decrease the calculation cost meanwhile ensuring the calculation accuracy.The ignition delay time and steady-state temperature of the reaction under various operating conditions were chosen as the comprehensive optimization indexes to guide the genetic algorithm to ensure that the final reduced mechanism could fully describe the combustion characteristics of the methane/dimethyl ether fuel mixture.The reduced methane/dimethyl ether reaction mechanism was composed of 45 species,119 steps,whose ignition delay time was in large consistency with the experimental results.In addition,there was a coherent evolution tendency in the prediction of methane/dimethyl ether turbulent combustion characteristics comparing the reduced mechanism with the original mechanism.Which meant that both mechanisms had slight relative errors in the prediction of temperature profile,radicals,and final products under various experimental conditions.The current investigation provided technological supporting for advancing reduced mechanisms in methane/dimethyl ether combustion systems.