The design and performance results of simple flat plate low solidity vaned diffusers

Vaned diffusers for centrifugal compressors have decades of development history, but most of it is of a proprietary and empirical nature. Centrifugal compressor designers are continuously searching for a diffuser system that combines the good dualities of vaneless and vaned diffuser systems. Vaneless diffusers are known to possess wide operating range with relatively low efficiency while current conventional vaned diffusers have narrow range and high efficiency. The low solidity vaned diffuser (LSVD) has shown good performance from both range and efficiency standpoints. Its relatively high efficiency and wide flow range potentials are strong current factors, leading the compressor manufacturer to seriously consider it as the best compromise diffuser that has been sought through the years. This paper discusses the design and experimental performance results of eight flat plate LSVDs. These diffusers had a solidity of 0.9, 0.8, 0.7 and 0.6. Eight low solidity vaned diffusers (LSVD1 to LSVD8) and for comparison purposes two vaneless diffusers (VNL1 and VNL2) and a conventional vaned diffuser (CVND) were all tested downstream of the same impeller at three speeds.