Prediction of Swirl Velocity of In-Cylinder Flow of an Engine by a Simplified Simulation Model (4th Report, Evaluation of Valve Timing)

Improving combustion of the spark ignition engines contributes largely to decreasing fuel consumption, especially under the conditions of medium or low speed and low load. In this paper, valve timing is evaluated from the viewpoints of swirl velocity as well as the volumetric efficiency, burned gas fraction in a fresh mixture charge, and pumping loss at intake stroke by using the predictions of the simplified simulation model. As a result, the timing of intake valve opening and closing is considerably affected by the swirl velocity. It is also confirmed that the mean swirl velocity controlled by the valve timing is higher than that controlled by the conventional throttling system under the same volumetric efficiency condition.