Effect of CO2/H2O/N2 gas dilution on laminar flame speeds of syngas at elevated pressure

Syngas dilution combustion is an important mode of operation for gas turbines with high efficiency and low pollution. CO2, H2O and N2 were used as dilution gases to study the effect of dilution ratio on the laminar flame speed of syngas (CO/H2/CH4) at elevated pressures with numerical simulation, and the physical and chemical mechanisms of the three gases were also analyzed in radical concentration change, sensitivity value and ROP(rate of production) analysis. The results show that the laminar flame speed decreases with the increase of combustion pressure and dilution ratio, and the suppression of CO2 on the laminar flame speed is the most significant. The physical effect of the diluent gas on the laminar flame velocity is far greater than the chemical effect, but the chemical effects of CO2 and H2O cannot be ignored. The chemical effect is to affect SL by changing the concentration of H and OH radicals, where CO2 dilution reduces the H and OH radical concentration, and H2O dilution decreases the H radical concentration, thereby reducing the laminar flame velocity of the syngas. Further reaction kinetics analysis finds the main path of change of H/OH concentration at low and high pressure, and the chemical reaction rate diluted by H2O is more sensitive to pressure than CO2. © 2020, Chemical Industry Press Co., Ltd. All right reserved.