Numerical Simulation of Flow Field in Cylinder of Natural Gas Engine

Abstract

In order to study the flow field in the cylinder, the intake and compress stroke of a four valve natural gas engine was studied by numerical simulation in this paper. The results of the simulation show that the tumble in the cylinder of the four valve engine is formed at the end of the intake stroke. The mean turbulence kinetic energy in the cylinder first increases during the intake stroke. During the compression stroke the turbulence kinetic energy decreases, while the turbulence kinetic energy in the center of the cylinder increases as a result of the crash of the tumble at the end of the compression stroke. The increased turbulence kinetic energy is good for increasing the velocity of flame propagation and improving the gas engine burning velocity. Both the position of the tumble center and the flow velocity gradient has a great effect on the evenness of the flame spreading along the radius and the flame forward side is asymmetric from the effects of the in-cylinder tumble.