Modification of Centrifugal Impeller and Effect of Impeller Extended Shrouds on Centrifugal Compressor Performance

Efficient, compact centrifugal compressors with higher pressure ratios along with adequate surge margins are required for the future. Achieving these necessitates development of newer non-conventional diffuser designs and rotating vaneless diffusers is one such concept. One method of reducing the shear losses on the stationary vaneless diffuser sidewalls, with probable improved efficiency and flow range of low-to-medium specific speed stages, is the use of a “rotating diffuser”. A particular type of rotating vaneless diffuser is forced rotating vaneless diffuser, in which the rotational speed equals that of the impeller and the rotating vaneless diffuser is integral with the centrifugal impeller which is created by extending the impeller disks beyond the blades. In the present paper, the effect of extended shroud by 10% with impeller exit diameter are analysed on flow diffusion and performance and compared with stationary vaneless diffuser. The higher static pressure rise with reduced losses and increased efficiency is achieved by shroud extension.