scholarly journals Thermographic Stall Detection by Model-Inspired Evaluation of the Dynamic Temperature Behaviour

2021 ◽  
Vol 11 (18) ◽  
pp. 8442
Author(s):  
Felix Oehme ◽  
Janick Suhr ◽  
Nicholas Balaresque ◽  
Daniel Gleichauf ◽  
Michael Sorg ◽  
...  

Model-inspired signal processing approaches with an enhanced detectability of flow separation on thermographic images are presented. Flow separation causes performance loss, structural loads and increasing acoustic emissions on wind turbine rotor blades. However, due to the low thermal contrast between turbulent and separated flow regions, the non-invasive thermographic visualisation of flow separation is currently only possible for wind tunnel measurements, which are characterised by a high thermal contrast and a small measuring distance. The state-of-the-art signal processing approaches evaluate the surface temperature fluctuation of thermographic image series. However, understanding of the signal measurement chain with a distinct consideration of the influences on the dynamic surface temperature is incomplete. Therefore, designing model-inspired signal processing approaches which provide a high interpretability and a maximum contrast is an open task. The proposed signal processing approaches evaluate the surface response selectively, by using the amplitude information of the surface temperature response to an oscillating input signal or gradient-based for a transient input signal. The approaches are applied to wind tunnel measurements on a rotor blade profile at a near thermodynamic steady state and a transient thermodynamic behaviour at Reynolds numbers that are representative for operational wind turbines. The gradient-based evaluation shows an improved contrast for the detection of flow separation, but is only applicable to profiles with transient thermodynamic behaviour. The amplitude evaluation provides a high degree of interpretability of the processed images based on flow-dependent features and enables for an unambiguous identification of flow separation by a global amplitude minimum close to the separation point. Additionally, an increased spatial resolution for surface modifications is shown, while the contrast between flow regions is significantly decreased. Hence, the proposed approaches allow for an improved identifiability of flow separation with regard to future applications on wind turbines in operation.

Author(s):  
G. Pechlivanoglou ◽  
S. Fuehr ◽  
C. N. Nayeri ◽  
C. O. Paschereit

The effects of distributed roughness on wind turbines are extensively investigated in this paper. The sources of roughness are identified and analyzed and their effects on airfoil are estimated from simulations and measured with wind tunnel measurements. In addition to the environmental and manufacturing induced roughness, several forms of roughness-related shape deviations are investigated and their effects on the aerodynamic performance of airfoils is qualitatively predicted through numerical simulations. The actual effects of roughness on wind turbine performance are also presented through power production measurements of wind turbines installed in sandy environments. These measurements are correlated with simulated power predictions, utilizing a steady state BEM code.


2020 ◽  
Vol 53 (2) ◽  
pp. 12638-12643
Author(s):  
Michael Sinner ◽  
Vlaho Petrović ◽  
Frederik Berger ◽  
Lars Neuhaus ◽  
Martin Kühn ◽  
...  

AIAA Journal ◽  
10.2514/2.841 ◽  
2000 ◽  
Vol 38 (10) ◽  
pp. 1879-1888 ◽  
Author(s):  
R. Yano ◽  
V. Contini ◽  
E. Plonjes ◽  
P. Palm ◽  
S. Merriman ◽  
...  

Author(s):  
Mark Reeder ◽  
Walt Allen ◽  
John Phillips ◽  
Robert Dimmick

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