Electrohydraulic Valvetrain for Extreme Value Diesel Engine 2002-01-1282

One way to improve diesel engine performance and to reduce emissions is improving power density and combustion cycle efficiency. It can be done by increasing combustion pressure and engine speed drastically and also by improving the controllability of the engine. Besides of the fuel injection system the key element in improving controllability is the valvetrain.

Extreme combustion pressure and engine speed set special requirements for valvetrain design. As the pressure and engine speed are increased the load on the valve actuation mechanism becomes higher because of the higher pressure acting on the valve plate and also the need for higher acceleration. High instantaneous power required due to high load makes electrohydraulic system a natural choice for actuation mechanism.

An electrohydraulic camless valvetrain (IHAflex) for extreme value engine (EVE), developed by Institute of Hydraulics and Automation of Tampere University of Technology, uses neither cams, nor retainer springs. Both opening and closing is controlled by the means of the electrohydraulic system. Power consumption of the valvetrain is reduced by recovering the kinetic energy of the valve during deceleration. The electrohydraulic valvetrain has significant benefits in comparison to conventional design: valve motion can be controlled continuously and independently, space needed for valve actuation is reduced, valve opening and closing are faster and speed can be varied.

The first prototype of the IHAflex valvetrain will be installed on the experimental EVE at late 2001. Experimental engine used for testing has engine speed and combustion pressure approximately twice as high as in medium speed diesel engines currently in production. In the paper the first prototype system is introduced and its features are discussed. Also special features concerning electrohydraulic system and component design to meet these requirements are discussed in detail. Dynamic behaviour of the system is presented and discussed in the basis of simulation results.