Проблема использования энергии ветра. Ч. 4 : Теория и аэродинамический расчет ветряных двигателей

— 70 - В' — Load on the disc area . ««'P Y Г — Velocity circulation. Cp—Profile drag" coefficient of the aerofoil. Су —Lift coefficient. D — Diameter of windmill in meters. —Thickness of aerofoil. e —Ve l oc i t y d r o p coefficient i n the p l ane of t h e windmill у . — Disc area of windmill in sq. m' • — Area of cross-section of the stream far behind the windmill. i —Number of blades. M—To r q u e developed b y the windmill. — Nondimenslonal torque —~тж • u. = p —Pr e s sur e in kg. per sq. m. P — Projection of aerodynamic forces of the axis of the windmill. rj — Density of air in kg. sec. ® m~*. r —Rad i us in m. /'о —Ins i de radius of windmill. —Out s i de radius of windmill. i — Time in seconds. T —Powe r in kgm. per sec.; also absolute temperature in degrees centigrade. 7] —Powe r of the ideal windmill. Tf —L o s s in p owe r d u e t o induced drag of t h e blades, — Loss in power due to twisting of the stream. T^, —L o s s in power due to profile drag of the blades. — Circumferential velocity of rolation of the stream in the plane of the windmill. «2 — Circumferential velocity of rotation of the stream behind the windmill. —Increase in velocity of flow in the plane of the windmill in m. per sec. z/2 —Increase in velocity of flow far behind the windmill. V — Velocity of fl ow far ahead of windmill in m. per sec. W — Relative velocity of the stream. г —N u m b e r of moduli a t radius • 2,, —Number of relative moduli = . " . V — $ — Efficiency. — Efficiency of the ideal windmill, 7] —Relative efficiency of the windmill. 0) —T i p velocity of the windmill.