Effect of Roughness and Oncoming Fluctuations on Performance of Wind and Gas turbine Blades.

What is it about?

The external surfaces of turbomachinery blades, during their life cycle, often become rough due to the accumulation of combustion products, erosion, etc. In addition, the oncoming flow in these cases also contains relatively high levels of fluctuations due to the presence of free-stream turbulence. Our study experimentally investigates the combined effect of both free-stream fluctuations and surface roughness on aerodynamic performance using wind tunnel testing on a model surface. Results show that the combination of oncoming fluctuations and surface roughness will lead to underperformance, whose extent will be dependent on the location of the roughness. Further, by carefully designing the roughness, we can reduce the instances of 'hot-streaks', which cause thermal damage, and reduce the life cycle of turbomachinery devices.

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Photo by Felix Berger on Unsplash

Photo by Felix Berger on Unsplash

Why is it important?

Designing turbomachinery blades with rough surfaces is difficult and the present results provide some insight into effectively modeling such practical scenarios. Additionally, turbomachinery blades often have a reduced life cycle due to the thermal damage caused by 'hot-streaks' occurring over their surfaces. This work demonstrates that specially designed and strategically located roughness strips might be able to reduce the number of occurrences of 'hot-streaks', thereby increasing the life cycle of the device.

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