Momentum-dominated Methane Jet Flame at Sub-atmospheric Pressure

AbstractThe influence of pressure and flow rate on momentum-dominated methane laminar flames’ flickering and radiation characteristics were experimental studied to provide a focused description of diffusion flame behavior at sub-atmospheric pressure of 50-100kPa. Measurement system consisted of CCD camera, high speed camera and schlieren system, radiation flux meter. Parameters including flame length, liftoff height, flickering frequency, and radiation intensity were compared and analyzed over the pressure range of 50-100kPa in a low pressure combustion cabin. The controlled fuel mass flow rates provided diffusion flames of 5.95-23.81mg/s stable at all ambient pressures considered. Experiment results indicated that for momentum-dominated jet flame, flame lengths were not dependent on pressure but linearly dependent on mass flow rate. As soot volume fraction was strongly influenced by pressure, when pressure descended, the radiation intensity declined resulted from reduction of soot formation. Lift off phenomenon of diffusion flames was not significant, however, liftoff heights also increased with increasing pressure and mass flow rate gradually. A semi-quantitative explanation on combined effect of pressure and velocity on flickering frequency was given as f = 0.227u0.18P∞1/3. All experiment data was in good agreement with theoretical analysis