Enhancement of Flow Diffusion in a Centrifugal Compressor Stage with Backward Curved Impeller by Shroud Extension – A Numerical Study

Abstract:

Efficient, compact centrifugal compressor with higher pressure ratios along with adequate surge margins necessitates developing non-conventional diffuser designs. A method of reducing shear losses on the stationary vaneless diffuser sidewalls is by rotating the side walls of vaneless diffuser. Forced rotating vaneless diffuser, a type in which the diffuser is integral with impeller and rotates at same speed, is obtained by extending the impeller disks beyond the blades. In this paper, the conventional stationary vaneless diffuser is redesigned to act as a ‘forced’ rotating vaneless diffuser. The effect of shroud extension is analyzed for the backward curved centrifugal impeller with shrouds extended by 40% with impeller exit diameter on flow diffusion and compared to an impeller with stationary vaneless diffuser. A higher static pressure rise by around 10% along with reduced losses is achieved by shroud extension configuration, RVD-ES. This indicates that the rate of diffusion is higher in the extended shroud configuration.

• Periodical: Advanced Materials Research (Volumes 984-985)
• Pages: 1102-1107
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.984-985.1102
• Online since: July 2014
• Authors: Sivamani Seralathan*, D.G. Roy Chowdhury, Anil Kumar Jaswal
• Keywords: Backward Curved, Centrifugal Impeller, Shroud Extension, Vaneless Diffuser

References

[1] J. Novak, Glatter Diffuser bei Zentrifugal pumpen, Vaneless Diffuser in Centrifugal Pumps, Zeitschrift fuer das gesamte Turbinenwesen Heft 24 (1907).

[2] L. Sapiro, Effect of impeller-extended shrouds on centrifugal compressor performance as a function of specific speed, ASME Journal of Engineering for Power, 105 (1983) 457-465.

DOI: 10.1115/1.3227437

[3] M. Govardhan, S. Seralathan, Effect of forced rotating vaneless diffusers on centrifugal compressor stage performance, Journal of Engineering Science and Technology, 6 (2011) 558-574.

[4] S. Seralathan, D.G. Roy Chowdhury, Modification of centrifugal impeller and effect of impeller extended shrouds on centrifugal compressor performance, Procedia Engineering, 64 (2013) 1119-1128.

DOI: 10.1016/j.proeng.2013.09.190

[5] S. Seralathan, D.G. Roy Chowdhury, Effect of extended impeller disks of inlet/exit ratio 1. 3 on centrifugal compressor performance part 1- stage performance and diffuser performance: submitted to Procedia Engineering (2014).

DOI: 10.1016/j.proeng.2013.09.190

[6] S. Seralathan, D.G. Roy Chowdhury, Effect of extended impeller disks of inlet/exit ratio 1. 3 on centrifugal compressor performance part 2- flow through centrifugal compressor: submitted to Procedia Engineering (2014).

DOI: 10.1016/j.proeng.2013.09.190

[7] R. Ajith Kumar, Exit flow studies on some centrifugal impellers, M. Tech. thesis report, Department of Mechanical Engineering, Indian Institute of Technology Madras, India, (1990).