Friction and leakage analysis of the blocker-type valve designed for a revolving vane expander

Abstract

Friction and leakage are two known issues that contribute to inefficiencies of rotary vane machines, and the Revolving Vane (RV) mechanism was introduced to reduce them. When used as an expander, a mechanism to determine the timing of the suction process in RV machine is required. In this study, a blocker-type valve is proposed for the suction control, and a simulation is carried out to investigate its friction and leakage characteristics. The valve comprises a stationary blocker that blocks high-pressure working fluid from entering the working chambers during expansion. In order to reduce friction, there should be a clearance between the rotary parts and the stationary blocker, which inevitably causes leakage of the working fluid into the working chambers. The leakage was modelled as a compressible flow through a convergent nozzle followed by a Fanno flow through an adiabatic constant cross-section channel. The results showed that the amount of leakage in the absence of lubricants is almost higher than ideal expander flow rate. However, this leakage demonstrated a positive contribution to the output torque as the results of the cylinder wall shear stress. The results suggested the importance of using lubricants in this valve design.