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ECN publication
Stall flag diagnostics of the Aerpac 43m rotor
Published by: Publication date:
ECN Wind Energy 1-4-2001
ECN report number: Document type:
ECN-C--01-042 ECN publication
Number of pages: Full text:
12 Download PDF  

This report concerns an Aerpac 43m diamter rotor designed for a turbine of 600 kW rated power. Above 16 m/s, the rotor produced even more than 700 kW. Therefore its cut-out wind speed was reduced from 25 to 16 m/s to prevent the turbine from overloading or overheating. The penalty was of course a production loss. The rotor also produced less than predicted below rated and in particular at approximately 10 m/s. Both deviations caused a production loss of approximately 10% relative to the design.The flow about the blades was visualised with stall flags during starts and stops of the turbine. The visualisations were analysed with image processing software and we came to the remarkable conclusion that two measures (based on general knowledge) taken to correct the problems made the situation worse! Using stall flags, we could clear up what really happened, why the corrections didn't help, and most importantly, what had to be done: 1. We removed the stall strips meant to reduce overpower, since they caused the production losses around 10 m/s. We shifted vortex generators between 0.45R and 0.65R towards the trailing edge. They should increase the power below rated but actually caused overpower. We added vortex generators between 0.65R and 0.8R since this entire range showed premature stalling and thus was responsible for the low production too. As a result of the adaptions the overpower vanished and the production increased by 8%.

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