Abstract

The present experimental study is part of a comprehensive analysis accounting for heat transfer and aerodynamic losses on a highly loaded low pressure turbine blade with varying surface roughness. Whereas part I focuses on heat transfer measurements at airfoil midspan with different deterministic surface roughnesses, part II investigates surface roughness effects on aerodynamic losses of the same airfoil. A set of different arrays of deterministic roughness (the same as used in part I) is investigated in these experiments. The height and eccentricity of the roughness elements is varied, showing the combined influence of roughness height and anisotropy on the losses produced in the boundary layers. It is shown that the boundary layer loss is dominated by the suction side. Therefore, the investigations focus on measurements of the suction side boundary layer thickness at midspan directly upstream of the trailing edge. The experiments are conducted at several free-stream turbulence levels (Tu1 = 1.4% to 10.1%) and different Reynolds numbers. The measurements reveal that suction side boundary layer thickness is increased by up to 190% if surface roughness shifts the transition onset upstream. However, in some cases, at low Reynolds numbers and free-stream turbulence, surface roughness suppresses boundary layer separation and decreases the trailing edge boundary layer thickness by up to 30%.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.