Effect of end-wall riblets on radial turbine performance

Khader, M. A. & Sayma, A. I. (2017). Effect of end-wall riblets on radial turbine performance. IOP Conference Series: Materials Science and Engineering, 232(012075), doi: 10.1088/1757-899X/232/1/012075

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Abstract

This paper presents a detailed study of the impact of manufacturing residual riblets at the rotor hub surface of a radial inflow turbine on the flow within the rotor passages and their contribution to drag reduction. Numerical analysis has been used to study the effects of those features at design point conditions. Riblets with different height and spacing have been examined to determine the riblet geometry where the maximum drag reduction is achieved. The relative height of the riblets to rotor inlet blade height was introduced to generalise the results. At the end of this study the results were compared with the available data in literature. It was found that the introduction of riblets could reduce the wall shear stress at the hub surface, while they contribute to increasing the streamwise vorticity within the rotor passage. For the geometries tested, the minimum drag was achieved using riblets with relative height hrel = 2.5% equivalent to 19.3 wall units. The results revealed that the spacing between riblets have a minor effect on their performance, this is due to the size of the streamwise vortex above the hub surface which will be discussed in this work.

Item Type: Article
Additional Information: This is an author-created, un-copyedited version of an article accepted for publication/published in IOP Conference Series: Materials Science and Engineering. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. This article is published under a CC BY licence. The Version of Record is available online https://doi.org/10.1088/1757-899X/232/1/012075.
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/18568

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