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The effect of superimposed Rankine and forced vortices on conical diffuser performance

Published online by Cambridge University Press:  04 July 2016

R. S. Neve  and
A. Thakker
R. S. Neve
Affiliation:
Department of Mechanical Engineering, The City University, London
A. Thakker
Affiliation:
Department of Mechanical Engineering, The City University, London
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Extract

It is not always possible for a designer to accommodate a conical diffuser giving the greatest possible pressure recovery for a given area ratio because this usually involves a long version with a total conical angle of about 7 degrees. Considerable efforts have therefore been made to improve the performance of diffusers with total conical angles up to at least 30 degrees by adopting various techniques listed in Ref. 1. One suggestion was the addition of whirl to the flow in the inlet pipe; that is, to superimpose a vortex coaxial with the pipe and diffuser axis. However, Refs. 1 and 2 show the amount of published research on this topic to have been meagre.

A previous paper has dealt with the case of adding a forced vortex whirl velocity distribution to the incoming flow and showed that improvements were possible, certainly in static pressure recovery and even in so-called efficiency, using a restricted definition of the latter. Because of mechanical vibration problems, the maximum swirl angle that could be added to the flow was about 15 degrees, corresponding to a forced vortex rotation rate of about 28 rad/s. This led to a beneficial redistribution of axial velocity components and a diminished tendency for flow separation from the walls.

Type
Research Article
Information
The Aeronautical Journal , Volume 85 , Issue 845 , June 1981 , pp. 234 - 239
Copyright
Copyright © Royal Aeronautical Society 1981 

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References

1. Introduction to design and performance data for diffusers. ESDU Data Sheet 76027, November 1976.Google Scholar
2. Tvlakker, A. An investigation of conical diffuser performance with swirling inlet flow. PhD Thesis, City University, London, 1980.Google Scholar
3. Neve, R. S. and Wirasinghe, N. E. A. Changes in conical diffuser performance by swirl addition. Aeronautical Quarterly, 29 pp 131–143, August 1978.Google Scholar
4. Patterson, G. N. Modern diffuser design. Aircraft Engineering, 10, pp 267–273, September 1938.Google Scholar
5. Cockrell, D. J. and Markland, E. A review of incompressible diffuser flow. Aircraft Engineering, October 1963.Google Scholar