IGNITION EXPERIMENTS BY SHOCK WAVES: STUDIES ON METHANE-AIR MIXTURE IGNITION CAUSED BY SHOCK WAVES (2ND REPORT).

Described in this paper is the investigation of ignition of methane-air mixture by shock wave using the shock tube apparatus. Reaction between methane and oxygen is considered to advance rapidly, when concentration of methyl group ( left bracket CH//3 right bracket ) exceeds a certain threshold value. The time elapsed before reaching the threshold is called a delay time for ignition. And, in the experiment, practically ignition is recognized by ascending of pressure and flames sensed by a photo cell. Experimental conditions are as follows; (1) Velocity of shock waves: 2. 3 Mach approx. 3. 1 Mach (2) Concentration of CH//4 in the air: 3. 5 approx. 20% (3) Ignition will appear only near the end of shock tube, where the shock waves are reflected back and turn their propagation direction. Results obtained are, (1) Ignitions of CH//4 air mixture are sometimes yielded by shock waves, (2) The delay time from excitation to ignition is usually between 0. 3 and 1. 0 milli-seconds, and ignition temperature is assumed also 1,100 and 2,000 K. (3) Ignition is produced by adiabatic compression of gas mixture.