Abstract: To explore the ignition characteristics of methane/air mixture generated by the pre-chamber turbulent jets, experimental studies were conducted in a large bore constant volume chamber. The flame image batch processing was conducted by using MATLAB software to obtain the flame characteristic parameters. By analyzing the pressure variations and flame images taken by a high-speed camera, the effects of air-fuel equivalence ratios and pre-mixed pressures on jet flame ignition process and flame propagation were studied. The results show that the jet flames in the main chamber are asymmetry, which can be even worse when the air-fuel equivalence ratio is lower due to the asymmetric orientation of the spark plug. As the initial pressure or air-fuel equivalence ratios increase, the flame propagation becomes slower. Furthermore, with the lower air-fuel equivalence ratio (λ=08), the flame propagation tends to be more sensitive to the back pressure variation.

Key words: constant volume chamber, jet flame, image processing, flame propagation