CFD simulations of compressed air two stage rotary Wankel expander - Parametric analysis

The CFD modelling was used to investigate the performance of the rotary device using air as an ideal gas with various port diameters ranging from 15 mm to 50 mm; port spacing varying from 28 mm to 66 mm; different Wankel expander sizes (r = 48, e = 6.6, b = 32) mm and (r = 58, e = 8, b = 40) mm both as single-stage and as two-stage expanders with different configurations and various operating conditions. Results showed that the best Wankel expander design for a single-stage was (r = 48, e = 6.6, b = 32) mm, with the port diameters 20 mm and port spacing equal to 50 mm. Moreover, combining two Wankel expanders horizontally, with a larger one at front, produced 8.52 kW compared with single-stage which gave 4.75 kW power output at the same operating conditions. Also, a maximum isentropic efficiency of 91% was calculated with inlet pressure of 6 bar and inlet temperature of 400 K at 7500 rpm for the two-stage compared to the 87.25% for the single-stage.