Simulation And Optimization Of Si Engines With Variable Valve Timing

A lot of technical solutions were developed to achieve better vehicle dynamic characteristics and oil consumption value, and to meet continuously improved exhaust emission regulation. Gasoline direct injection, lean burn and variable valve technology are especially concerned for SI engines.VVT are widely used in the last two decades. At the beginning, only cam timing can be adjusted. Nowadays, fully variable valve technique is adopted in newly developed engines. Even electrohydraulic control camless valve train is studied. VVT technique changes engine performance more and more effectively, both low and high speed, load. It also helps reduce emission such as NOx.Common thermodynamics calculation can’t satisfy the requirement made by modern research of advanced engines. Computer aided simulation help people raise produce rate, lower cost and improve quality. GT-POWER is the most popular software when simulating vehicle engine performance. All of the engine simulation in this paper is base on GT. Two-zone combustion model are applied and verified by experiment, it turns out that two-zone model are reliable in combustion simulation. Different VVT structure leads to different VVT strategy. The difficulty to decide VVT strategy grows with complication of structure, due to the enlargement of variable number. Optimum algorithm must be considered. This paper couples algorithm to engine simulation. Cams of a 4 cylinder 1.6L engine are redesigned through this method. Dynamic performance of is also confirmed. Optimum Results are verified in real engine test and an extra 3kW power is acquired. This indicates a new method of cam optimum design.A series of VVT strategies are simulated and optimized for two SI engine. Optimum method greatly shortens the period of engine development.