Experimental study on ignition process for ethylene high speed jet

In order to investigate the ignition process with fuel-rich gas of scramjet combustor, a simplified burner with fuel-rich hot coflow and sonic nozzle jet was designed. Ignition process of sonic ethylene jet issuing into a coflow of hot exhaust products of a rich premixed ethylene/air flat flame was examined using the chemiluminescence. Three cases with the equivalence ratio of coflow varying from 1.4 to 1.6 and the injection pressure varying from 2atm to 3atm were examined. The results indicate that:(1) the ignition process of sonic ethylene jet in fuel-rich gas may be divided into four steps:(a) jet and coflow mixing; (b) strong chemical reactions between jet and surrounding air; (c) occurrence of extinction in the downstream of flame; (d) steady flame; (2) the equivalence ratio of coflow 1.4 was more effective than 1.6 for ignition process; (3) with the increase of jet velocity, flame luminosity is lowered due to incomplete burning in the higher speed steady flame.