Mutual effects between a gliding arc discharge and a premixed flame

Mutual effects between a gliding arc(GA)discharge at atmospheric pressure and a premixed CH_(4)/air flame were experimentally investigated.Effects of the flame on the GA were studied using simultaneous measurements of the current,the voltage,and the instantaneous images of the plasma columns.The GA in the flame has a thicker and more diffusive plasma column,and it is more frequently ignited at a smaller breakdown voltage than that in the air.The GA extension velocity and the gliding velocity in the flame are larger than those in the air.The electrode voltage drop of the GA discharge in the flame is about 160 V,whereas that in the air is about 220 V.Compared with the GA in the air,the different features of the GA in the flame can be explained by high-temperature,weakly ionized,and species-abundant environment that are generated by the premixed CH_(4)/air flame.Effects of the gliding arc discharge on the premixed flames were demonstrated using planar laser-induced fluorescence of hydroxyl radicals(OH)and formaldehyde(CH_(2)O).OH and CH_(2)O can be formed in the CH_(4)/air mixture in the presence of the GA due to kinetic effects,and the increase of OH and CH_(2)O shows the great potential of the GA for combustion enhancement.

MCGA-assisted ignition process and flame propagation of a scramjet at Mach 2.0

The ignition process and flame propagation with ethylene fuel in cavity-stabilized scramjet by a Multi-Channel Gliding Arc(MCGA)at Mach 2.0 were investigated.Effects of equivalence ratios on the MCGA-assisted ignition process and flame propagation of the scramjet were recorded by two high-speed cameras from different view angles.The discharge characteristics of MCGA are also collected synchronously with the high-speed cameras.The distributions of temperature,velocity,and equivalence ratios in non-reactive flows of the cavity were simulated by Reynolds Averaged Navier-Stokes(RANS)model.The results show that MCGA can achieve reliable ignition with the Global Equivalence Ratios(GER)between 0.06 and 0.17.The ignition process is composed of flame kernel generation,flame development,and stable combustion.The time from flame kernel generation to the establishment of global flame decreases as GER decreases from 0.17 to 0.08.In the streamwise direction,the flame first develops to the Cavity Leading Edge(CLE)because of the influence of the cavity recirculation zone and then uplifts into the cavity shear layer,and finally develops to the Cavity Trailing Edge(CTE).In the spanwise direction,the flame width is less than 50%of the width of the cavity before developing to CLE and begins to develop towards the two sides of the combustor after reaching CLE,which is affected by the angular recirculation zone on both sides of CLE.The ignition processes by MCGA in the scramjet combustor are significantly affected by local distributions of equivalence ratios and velocity in the cavity.