Control and Influence of Valve Condition on Compression Stroke of Hydraulic Free Piston Engine

Abstract

Though the two-cylinder four-stroke hydraulic free piston engine (HFPE) has advantages over the traditional HFPE in terms of fuel consumption and exhaust, its effective compression stroke which defines the compression ratio and the combustion is susceptible to the conditions of the intake valve. The force balance of the free piston assembly, the energy equation of the ideal gas in the combustion chamber and the relationship between the piston displacement and the angle of the intake valve were developed. The key parameters of the intake valve that influences the performance of the compression process were analyzed. The control flow chart of the intake valve was established according to the intake valve condition. The test rig was set up to verify the effectiveness and feasibility of the control. The results showed that no matter the initial angle of the intake valve is, the piston displacement almost overlaps and the piston can reach TDC almost at the same time. The angle of the intake valve and the servo motor are within the preset range when the intake valve closes and the piston reaches TDC despite of the changing of the initial angle of the intake valve.