Design of a Small-Scale, High-Rotational-Speed Centrifugal Compressor Operating with R-290

The current work highlights key challenges in the design of small-scale, high-rotational-speed centrifugal compressors for R-290 at domestic application scale on the basis of a single-stage demonstrator unit that is currently developed by ebm-papst. The demonstrator is operated in a vapor-compression cycle at a total pressure ratio up to 3, a maximum rotational speed of 240 krpm, and with maximum power supply of 3.2 kWe. Emphasis is placed on challenges related to aerodynamic stage design, impeller back wall sealing, and impeller thrust force balancing. Appropriate measures are proposed to overcome these challenges and compressor performance is quantified to evaluate the prospects of small-scale, centrifugal compressors for R-290 application in a wider context. Considerations related to mechanical design and manufacturing are briefly illustrated. Main design and performance assessments are conducted through 3D CFD RANS calculations.