Abstract
Many small wind turbines operate at high tip speed ratio and this gives rise to situations where compressibility may influence performance. The most important example is runaway, the operating point for an unloaded turbine where the rotational speed of the blades is maximised. Because compressibility significantly increases drag through the action of “shock-stall”, it may provide an inherent mechanism for overspeed protection. This possibility is tested computationally for a turbine with a high optimum tip speed ratio, having an aerofoil section (NACA 0012) whose behaviour in compressible flow is well known. Calculations of turbine performance for differing windspeeds, and hence Mach numbers, show that compressibility effects occur too slowly to prevent overspeeding. However, it is suggested that aerofoils could be designed to maximise the onset of shock stall.
Sign-in/Register to access full text options 
Free) 
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
