Effect of background turbulent field on ion current characteristics of methane-air premixed combustion

Abstract

Ion current detection technology has a broad application prospect in natural gas engines. The effect of background turbulent environment on ionic current characteristics of methane - air mixture premixed combustion needs further study. The premixed combustion of methane-air mixtures under different turbulence intensities was studied on the constant volume combustor with controllable turbulence intensities. The effects of turbulence intensity on flame image, combustion pressure and ion current signal during combustion were analyzed. The ion current calculation model was built by coupling Cantera chemical reaction calculation program in the MATLAB environment. The variation of the concentration of the main species under different conditions was analyzed and the ion current signals under different turbulent conditions were simulated. The results show that in turbulent environment, the flame front appears fold and cellular structure, which increases the flame front area and accelerates the combustion speed. With the increase of turbulence intensity, the peak of combustion pressure increases and the peak time is advanced. The ion current appeared earlier in turbulent environment, and the duration of ion current decreased with the increase of turbulence intensity. When the equivalent ratio is near 1, the species concentration change greatly due to the influence of incomplete combustion. The concentration of species except water and carbon dioxide increases with the increase of temperature. The ion current calculation model can predict the overall trend of ion current signal in turbulent premixed combustion, but the simulation results of ion current signal in the later stage of combustion are too large.