ROTARY WANKEL ENGINES AS EXPANSION DEVICES IN STEAM RANKINE-CYCLE ENGINES

Rotary Wankel engines offer several advantages compared with turbines and other positive-displacement machines as the expansion devices in low-power-output Rankine-cycle engines. So a Wankel expander was selected as the most appropriate device for a steam Rankine engine, operating principally, as a mini combined heat-and-power unit with a mechanical power output of 5-20 kW. Predictions of the performances of some of the commercially-available designs of Wankel engines when operating as steam expanders are compared. Two of the machines considered are suitable for the application envisaged. However, the design parameters and operating conditions of these devices need to be optimised.