Performance investigation of a novel expander coupling organic Rankine cycle: Variable expansion ratio rotary vane expander for variable working conditions

•VERRVE is designed and proposed to be integrated into the ORC system.•The influence of the ER on VERRVE performance is studied using GT-SUITE.•For the WHR of automotive ESC working conditions, the ER control strategy is studied. Organic Rankine cycle (ORC) waste heat recovery (WHR) has been proven to be a promising method for low-grade energy reutilization. However, the working conditions can move far from the nominal conditions when the heat source energy varies. This paper presents an investigation of a novel expander for ORC, the variable expansion ratio rotary vane expander (VERRVE), adjusting its expansion ratio (ER) by regulating the outlet opening angle according to variable working conditions. A VERRVE with an adjustable ER range of 1.55–3.02 was first designed. Second, the VERRVE was modeled by GT-SUITE, and its performance at various ERs was investigated. Compared to inlet temperature, the inlet working fluid pressure is the more sensitive influencing factor. Third, this expander was applied to automotive ESC working conditions. An inlet mass flow rate controller was added to ensure that the inlet heat matched the engine exhaust. For the light load condition a50, the influence of the ER is more remarkable. When the ER decreases from 3.02 to 1.83, the output power and exergy efficiency increase by 61.81% and 56.09%, respectively. VERRVE introduces variable ER into ORCs, which is especially recommended for application to ORC WHR systems with variable heat sources.