Pii: 0167-6105(86)90023-1
نویسنده
چکیده
If the effects of fluid rotation are neglected, one-dimensional theory for a single actuator disc gives a maximum power coefficient of 16/27. This is the usual Betz limit for the power of horizontal-axis wind turbines. Tandem discs are a more appropriate representation for a vertical-axis, Darrieum, wind turbine and give more accurate predictions of turbine performance when used in conjunction with blade element theory. The maximum power coefficient for two discs in tandem is 16/25. In the present paper the case of n actuator discs is considered. It is shown that the maximum power coefficient is [8n(n+l)]/[3(2n+l)2]. The corresponding axial inflow factor for the rth disc is (2r-1)/(2r+1), and the outflow factor for the outer annulus of that disc is 2r / (2r+l ). For a very large number of discs the maximum power coefficient is thus 2/3, which is 13% larger than the maximum for a single disc. Some flow visualization experiments on flow through tandem screens are presented which indicate that the minimum spacing below which the theory begins to become inaccurate is about one half of a disc diameter.
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