Control of Unstable Flow Using Rough Surfaces

Abstract:

The function of centrifugal blowers/compressors is limited at low-mass flow rates by fluid flow instabilities leading to rotating stall. These instabilities limit the flow range in which they can operate. An experimental investigation was conducted to investigate a model of radial vaneless diffuser at stall as well as stall-free operating conditions. The speed of the blower was kept constant at 2000 RPM, while the mass flow rate was reduced gradually to investigate the steady and unsteady flow characteristics of the diffuser. These measurements were reported for diffuser diameter ratios, D_o / D_i, of 1.5, 1.75 and 2.0 with diffuser width ratio, b / D_i, of 0.055. The rotating stall pattern with one stall cell was dominant over the pattern with two cells which appeared at flow rates lower than the critical. In addition, the instability in the diffuser was delayed to a lower flow coefficient when rough surfaces were attached to one or both walls of the diffuser with the lowest values achieved by attaching the rough surface to the shroud wall. Results show that the roughness has no significant effect on stall cell frequencies.

• Periodical: Applied Mechanics and Materials (Volume 431)
• Pages: 155-160
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.431.155
• Online since: October 2013
• Authors: Saad Ahmed*
• Keywords: Centrifugal Compressor, Rotating Stall, Vaneless Diffuser

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