The intake and compression process for a gasoline
direct injection engine were simulated with CFD software and the change law of
incylinder flow field under different maximum valve lifts and timings
was analyzed. The results show that the gas velocity and turbulent kinetic
energy significantly increase with the decrease of maximum valve lift in the
intake stroke, but the tumble ratio is small at the end of the compression
stroke. For a small valve lift, the early opening or late closing of intake
valve will lead to the significant increase of turbulent kinetic energy in the
intake stroke. Correspondingly, the maximum average turbulent kinetic energies
at three cross sections of 5 mm, 10 mm,
and 15 mm away from TDC increase by 28.29% and 43.47%, 20.7% and 40.81%, 23.07% and 49.58% respectively. However, the
early opening or late closing of intake valve has little effect on the average
turbulent kinetic energy at the end of the compression stroke. In addition, the
opening time of intake valve has a great influence on the distribution of
turbulent kinetic energy at the end of compression, and the advance or delay of
intake timing will promote the homogeneity of incylinder
turbulent kinetic energy.
