inspection of impurity effects on the methane laminar flame speed under lean and diluted conditions

In the present work, the experimental study was performed to investigate the flame propagation and combustion characteristics of methane (ch4)-air mixture in a constant-volume combustion vessel (cv) under lean (φ= 0.7) and diluted engine-like condition. in addition, propane (c3h8) in two volume fractions of 20% and 40% was added to methane as the impurity and egr gas. schlieren photography of propagating spherical flame using a high speed camera and edge finding of flame pictures via a matlab code was used to find the rate of flame instantaneous radius. the unstretched flame propagation speed and markstein lengths were obtained via a nonlinear methodology in different chamber pressures. flame speed modeling was performed using an improved version of kinetics model. the result showed that adding propane to methane increases the laminar flame speed and propensity of instability. the cellular instabilities for the diluted methane/propane–air flames were interpreted and evaluated in the viewpoint of the hydrodynamic and diffusional-thermal instabilities.