In view of the problems of combustion instability and low combustion efficiency in the presence of engine cold start

the flame characteristics in an engine cylinder were analyzed to explore the effect of enhanced intake swirl on cycle-to-cycle variability and power output

on the basis of adjusting the intake swirl of a single cylinder visualization engine under cold start conditions. The test engine was of a 4 valve design

including two intake and two exhaust valves

wherein an intake port was provided with a swirl control valve to control swirl ratio. A high speed camera was used to obtain the combustion flame images through an optical window on the piston. With the help of post-processing tools

the flame propagation area flame boundary

flame propagation speed and other information were calculated and analyzed. At the same time

the cylinder pressure

combustion heat release rate and other characteristics were measured and recorded simultaneously by using a combustion analyzer. Though the comparison and analysis from different point of view

the relationship between the combustion flame state and the macro performance of the engine was revealed

and the different flame propagation properties under different swirl intensity were effectively explored. Results explain from the angle of the combustion flame that the increase of swirl ration can improve the combustion stability of cold start and promote the combustion process of the engine. Tests also show that the more concentrated

the late flamer kernel distribution with smaller fluctuation

the less the cycle-to-cycle variability

and the instantaneous heat release rate calculated from the cylinder pressure has a good linear relationship with the flame propagation area.