Investigation of effect of turbulance on flame development in a methane fuelled spark ignition engine

In this study, it is aimed to investigate the effects of in-cylinder turbulence on flame development and engine performance under various engine running conditions. In the study, the methane flame images captured from an optically accessed spark ignition engine fuelled with methane applying a laser sheet mie scattering method were used. Flame contours were extracted from methane flame images using image processing technique. A mathematical treatment of the wrinkles of flame surfaces have been made by applying the spectral analysis method to the co-ordinates of the flame contours. As a result of analysis made the integral length scale, turbulent flame brush thickness and mean flame radius have been measured. In addition, indicated mean effective pressure and mass fraction burn values were calculated from the pressure data captured simultaneously with flame images. Turbulent and pressure related parameters found for the engine running conditions of two different inlet port angle (0o and 40o swirl), two different spark plug locations (central and mid-radius ignition) and two different equivalence ratios (stoichiometric (?=1.0) and lean (?=0.8)) were compared as a function of crank angle.Findings have shown that the swirl created in the cylinder increases the turbulence intensity of the fluid, hence the turbulent flame brush thickness resulting an increase in combustion speed. The results also conceived that the structures (intensities and scales) of eddies appeared in the cylinder and their position according to the spark plug are quite worthy in terms of the combustion phases.Key Words: Combustion, Engine, Flame brush thickness, İntegral length scale, Spark plug location, Swirl, Turbulence