Investigation on the matching performance of a small cryogenic air turboexpander

The matching performance of a turboexpander is essential for a small reverse Brayton air refrigerator, especially when it works under varied operation parameters. Generally, an appropriate brake pressure is required when the turboexpander works under different operation parameters. In this paper, the matching performance of a turboexpander supported by a bump journal foil bearing and a pressurized thrust gas bearing is studied. A centrifugal blower is used as a brake. The performance curve is analyzed through a numerical simulation using CFX. The matching calculations were carried out with different brake blowers under both room temperature and low temperature. A brake pressure feedback control is applied in the experimental study. A thermal performance of the refrigerator is tested. The results indicated that the appropriate brake blower and brake pressure facilitate the system thermal performance under both room and low temperature. The simulation agrees well with the experimental results.