Reed Valve Evaluation and Selection for the Compressor Cylinder in Double Compression Expansion Engine (DCEE) Concept

Abstract

This paper shows the potential benefits of implementing four configurations of reed valves at the inlet of the two-stroke compressor used in the double compression expansion engine (DCEE) concept or 8-stroke engines over the conventional poppet valves used in 4-stroke internal combustion engines. To model the reed and poppet valve configurations, the discharge coefficient was estimated from RANS computational fluid dynamics simulations using ANSYS Fluent 2020 R1, with a pressure difference up to 0.099 bar. The calculated discharge coefficients for each case were then fed in a zero-one dimension model using GT-Power to understand the valve performance i.e. the volumetric efficiency of the compressor cylinder and the mean indicated pressure during the compression process at 1200 rpm. The results showed that for reed valve configurations, the discharge coefficient and mass flow rate were higher, the pressure drop was lower and the response with negative pressure difference was faster compared to poppet valves. In addition, all the reed valve cases showed improvement in volumetric efficiency and a drop in mean effective pressure than poppet valves. In particular, the optimum reed valve geometry in the present study resulted in a volumetric efficiency improvement of 7.2 percentage points and a mean effective pressure reduction of 3.2 percentage points compared to conventional poppet valves.