Experimental investigation of a prototype semi-dry revolving vane expander: Design challenges and performance criteria

Abstract

The current study focuses on the design and use of a modified revolving vane expander (M-RVE). It was designed to overcome the limitations of a previous Revolving Vane expander design (RV-I) with the eventual aim of its use in an Organic Rankine Cycle (ORC). The M-RVE is a semi-dry prototype with no active lubrication system. The prototype functioned well for a range of pressure differences of up to 6.5 bar(g) and speeds of up to 600 rpm, in test that used compressed air as the working fluid. Compared to the RV-I, the M-RVE prototype generated higher torque (as much as 3 times that of the RV-I), exhibited higher isentropic efficiencies of up to 41%, but with lower volumetric efficiencies of less than 3%. The low volumetric efficiency was mainly due to the lack of an active lubrication system. Analysis of the internal leakages demonstrated severe leakages at the suction valve (blocker) and vane endface clearance gaps. The ratio between the ideal and the total leakage mass flow rates was between 1.2% and 7.3% at a suction pressure of 6.5 bar(g).