Simulation Of Engine Performance With Fully Variable Valve Hydraulic Actuation System

As the valve lifting and valve timing of tranditional engine can't be changed, it can not take into account all the high speed and low speed condition, as a result of that, it can't meet the demand of fuel consumption, emission and power. Meanwhile the pumping lost by throttle in low and middle load result in greater fuel consumption and engine emission deterioration, therefore, studying of fully variable valve train which can change the valve lift from 0 to maximum and make the valve timing change in 180°CA after TDC instead of throttle controlling air input will be greatly significant.The intake valve of fully variable valve train studied in this paper is controlled open by intake cam, while the hydraulic mechanism controlles it down at an appropriate time. This control is continuous variable in order to achieve the full-variable valve movement. In this paper, K157FMI engine is for experimental prototype, we carry out a series of simulation studies of engine performance with fully variable valve train. The main contents include the following:First, analyse and use the reasonable methmetical model and physical model, including intake and exhaust mass velocity model, cylinder heat transfer model, combustion model, friction loss and so on. Seting the theory base of engine performance simulation.Second, set up the correct engine cycle simulation model with BOOST according to the real situation. Analyse the paremeters of every parts of model, including connecting pipes, air clearner, muffler, carburetor, structure paremeters of cylinder, valve motion and valve timing, heat release, heat transfer and flow efficient. The result of engine bench test proves the reliability of the model.Third, based on the cycle simulation model, use the valve motion dates of fully variable valve train instead of the original ones to realize the engine performance simulation. The result indicates that the engine with fully variable valve train could improve fuel economy and power in the condition of low and middle load by redusing the pumping loss comparing with the engine which control the air intake by throttle.Final, based on the fully variable valve train, we predict the engine performance which use miller cycle.