Abstract: To investigate the effect of stroke-to-bore ratio on in-cylinder flow field, the stroke-to-bore ratio of a three-cylinder port fuel injection gasoline engine model is changed to 0.7 and 0.9 (set as scheme 1 and scheme 2) with the other conditions the same, and the stroke-to-bore ratio of the original engine is 1.05 (set as scheme 3). Transient numerical simulation on the intake and combustion process of the three computational schemes at 2000r/min low load and 3800r/min full load is conducted using the software AVL-Fire. The velocity field, turbulent kinetic energy field and heat release rate of the three different computational schemes are compared. Results show that within reasonable limits, the appropriate increase of stroke-to-bore ratio can enhance the intensity of in-cylinder tumble, and hence improve the intensity and distribution of turbulence at ignition timing, achieving greater heat release rate and faster combustion

Key words: gasoline engine, stroke-to-bore ratio, tumble, turbulence kinetic energy, numerical simulation