Aerothermal Investigation of the Effect of Endwall Structures on Radial Turbine Heat Losses

M. A. Khader (), A. I. Sayma, Jafar Al-Zaili, Mohsen Ghavami and Hongwei Wu
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M. A. Khader: Department of Mechanical Engineering, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
A. I. Sayma: Department of Mechanical Engineering, Brunel University London, Kingston Lane, London UB8 3PH, UK
Jafar Al-Zaili: Department of Engineering, City St George’s, University of London, Northampton Square, London EC1V 0HB, UK
Mohsen Ghavami: Department of Engineering, City St George’s, University of London, Northampton Square, London EC1V 0HB, UK
Hongwei Wu: Department of Mechanical Engineering, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK

Energies, 2025, vol. 18, issue 16, 1-20

Abstract: This paper presents a detailed numerical investigation of the effect of hub-mounted riblets on the thermal and aerodynamic performance of a radial turbine rotor. While prior studies have shown that riblets reduce wall shear stress and improve aerodynamic efficiency, their influence on heat transfer and thermal losses remains underexplored. Using numerical simulations, this study examines the heat transfer characteristics within the rotor passage, comparing ribbed and smooth hub configurations under the same operating conditions. Results reveal that although riblets reduce frictional drag, they also enhance convective heat transfer—leading to a 6% increase in the heat transfer coefficient at the hub and 2.8% at the blade surfaces. This intensification of heat transfer results in a 4.3% rise in overall thermal losses, counteracting some of the aerodynamic gains. The findings provide new insights into the thermofluidic implications of surface modifications in turbomachinery and emphasise the importance of considering surface finish not only for aerodynamic optimisation but also for thermal efficiency. These results can inform future turbine design and manufacturing practices aimed at controlling surface roughness to minimise heat loss.

Keywords: riblets; radial turbine; heat transfer; shear stress reduction; micro gas turbines (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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