Numerical Analysis of a New Concept Variable Valve Actuation System

The present work concerns the analysis of a concept for a new variable valve actuation system for internal combustion engines, denoted HVC (Hydraulic Valve Control system). The system is an electro-hydraulic device which aims at minimizing the power consumption required for the valve actuation. Unlike lost motion devices, where the excess pumped oil is wasted in order to control the lift profile, the HVC system uses a reduced quantity of energy to ensure the actual lift profile. For that reason interesting potentialities to increase the global fuel conversion efficiency of the engine are expected, in addition to the benefits deriving from the control flexibility. The HVC system has been modeled by means of an hydraulic simulation tool, useful for the dynamic analysis of mechanical and hydraulic systems. In this work the main elements of the device will be described and their relevant modeling parameters will be discussed. The model has been validated by means of experimental lift data obtained in a prototype test bench. In order to properly tune the numerical model various operating conditions have been concerned. The system shows a high flexibility in the control of the lift and timing. The predicted power consumption is very attractive. The main effects of the oil pressure and of the oil temperature are discussed.