8. Performance Study of a Twisted Vaned Diffuser in a Compressor Stage

The current study compares the centrifugal compressor stage performance employed with vaneless and twisted vaned diffusers and in turn establishes the effect of diffuser parameters such as chord length and twist angle of the twisted vaned diffuser on its performance. The chosen diffuser has a uncambered aerofoil section with solidity varying due to blade twist from hub to shroud. To provide a twist to the diffuser blade, it is rotated in the direction opposite to that of the impeller, the origin being placed at the profile’s leading edge. The analysis is performed at 0.35 Mach at the tip of the impeller. For the analysis, chord length is varied from 80 to 120-mm insteps of 10 mm and the twist angle from 5° to 11° insteps of 2°. The mass flow rate is altered from 80 to 120% of design flow rate insteps of 10%, thus considering both design and off-design conditions. The overall stage performance is evaluated by means of different performance parameters like total-to-static stage efficiency, static pressure recovery coefficient, static head coefficient and power coefficient. The conclusion from the study is that using TVD results in better performance than VLD and TVD with chord length 100 mm, and twist 9° operating at design conditions results in the best performance for the chosen configuration.