Effect of DC electric field on laminar premixed spherical propagation flame at elevated pressures up to 0.5 MPa

摘要

The effects of DC electric field on laminar premixed CH4/air spherical propagation flames with excess air ratio =1.0, 1.2, 1.4 were investigated in a constant volume combustion chamber at elevated pressures up to 0.5MPa. Mesh electrodes were used to generate electric field inside the chamber. The flame front structure, flame displacement speed, and pressure-related combustion parameters were derived to evaluate the effects of electric field on flame propagation. The results show that the mean flame displacement speed increases in the electric field direction with the increase of applied voltages and it is more significant at lean conditions. The mean flame displacement speed decreases in the direction perpendicular to the electric field with the voltage at low pressures, while it increases with voltage due to flame instability induced by the electric field at higher pressures. The effect of electric field on flame displacement speed is more obvious with pressure rise. Electric-induced flame instability combined with the hydrodynamic instability both promoted at high pressure lead to much more cracked structure and enhance the flame displacement speed. An obvious acceleration stage during the flame propagation under electric field is also observed. The combustion peak pressure slightly increases and the timing of peak pressure is in advance with the increasing of applied voltage. The flame initiation time derived from pressure decreases with voltage and it is more obvious at higher pressures. In this study, a new ionic wind velocity calculation method was developed based on the ionic wind development degree and conservation of momentum. As pressure increases, the corrected ionic wind velocity decreases, and the tendency is consistent with the experimental results about increment of flame displacement speed at elevated pressures.