Evaluation Approach Of The Intake System By The In-cylinder Flow At Compression End

The steady flow in two different diesel engine intake-port are studied and compared by AVL steady flow test rig and simulation calculation. Then the transient simulation calculation during intake and compress stroke of rated conditon is conducted. The swirl motion in cylinder and combustion at any time during intake and compress stroke bowl is analyzed by the transient swirl ratio which is a non-dimensional parameter. Basing on the above study, it is found that the ability of forming swirl under small valve lift and medium valve lift has a greatly effect on the swirl motion of the compression end in cylinder and combustion bowl. The existing steady evaluation method can not embody this feature and shouled be improved.There are three kinds of flowing type in diesel in-cylinder:Swirl, Squish, Turbulence. Basing on above flowing characteristic, F.Payri devises the non-dimensional parameters:Transient Swirl Ratio and Transient Turblent Ratio to incarnate the in-cylinder swirl intensity and turbulent intensity in different crankshaft angle under certain engine speed, which have a good correlation with test. According to his design method, the non-dimensional parameter:Transient Squish Ratio is devised in this paper.With above 3 transient parameters, the transient simulation calculation of 3 different diesel engine, during intake and compress stroke of rated condition is conducted in this paper. Study found that the swirl in compression end has no significant effect on the tubulence in chamber. The tubulence in compression end is mainly determined by the maxmium tubulence motion strength during intake stroke and the squish strength in the compression end.In order to prove above finding ulteriorly, one diesel engine with 5 different kinds of combustion chambers is simulated, which shows the close relationship among turbulence, chamber shape and squish acceleration.