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This paper describes a modeling method for electrohydraulic variable valve mechanism based on CATIA. It focuses on the principle of the mechanism and the models of some parts with oil circuits in the hydraulic system and the moving principle of the actuation system. The additional damping cavity is used for pressure compensation. The actual mechanism based on the model precisely provides the hydraulic force to drive the valve to move quickly and smoothly at the right time. The modeling is of great importance for the valve movement on variable valve timing. Electro-hydraulic variable valve mechanism has been used in ZS1105 gasoline engine, and has achieved CAI combustion on some EGR strategies. Experiment studies verify that the mechanism based on the model is credible.

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Based on the application of self-developed electrohydraulic variable valve train (VVT), Controlled Auto-Ignition( CAI ) was achieved with Negative Valve Overlap (NVO) strategy. This VVT system that replaced the original camshaft was mounted on the head of a modified single cylinder engine. The cycle-to-cycle variation of CAI Combustion was investigated under several different operating points with 100 consecutive cycles sampled and stored. The experimental results indicated that as the excess air coefficient increases, with fixed engine speed and valve event, the coefficient of variation of indicated mean effective pressure (CoV IMEP ) dropped firstly and then increased. The CoV IMEP had the minimum value when the excess air coefficient ranges from 1.1 to 1.3. The engine speed and the valve lift showed the potential to influence CoV IMEP . Increased engine speed led to a more intense mixing progress, which introduced high intensity turbulence into the cylinder and resulted in a higher level of charge homogeneity at the end of compression stroke, and finally a steady CAI combustion. Meanwhile, decreasing the valve lift had a relatively minor effect. The variation of IMEP was consequently suppressed to some extend.