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

Theory and aerodynamic calculation of windmills. G. Sabinin. The theory of windmills presented in this volume is a combination of the method which was applied by Djewietzky to the calculation of cirscrews and the theory of the ideal windmill which was published by the author in 1927 in the Transactions of the C. A. H. J . ' ) No 32. The original feature of this theory consists in that the thrust is determined from the impulse of forces that are required for the generation of the vortex solenoid, the area of the vortex ring being calculated for the vortex ring in that portion of the solenoid where tnis^ by spreading out^ has assumed a cy ­ lindrical shape. The impulse of the force required for the generation of one vortex ring (Fig. 1) . P^t = ^F^V, where p = density, = area of t h e vortex ring, and Г = velocity circulation of one vortex ring. The thrust is determined as the sum of impulses required to generate all the vortex rings formed per unit time, and is expressed thus; P = 9F, [V- ' ' -I )V, , (3) where V = velocity far ahead of the windmill and — increase in velocity far behind the windmill. This expression can be written in the form P = [ p f i ( l / — f 2 = + / е д . (4) where — disc area of the windmill. Expression (4) can be interpreted thus: the thrust is numerically equal to the mass of fluid carried away by the windmill times the increase in velocity far behind the windmill, the mass of fluid carried away being the sum of the mass of fluid passing through the disc and the attached mass sucked in by the end of the solenoid (the shaded portion within the solenoid in Fig. 2). To deduce the relation between and is formed the equation of the balance of energy (oti + /Иа) J — P{V — Vy) — ( «1 + OTa) — т^ Ц = 0, in which the first term represents the »communicated t o the windmill kinetic energy o f t h e mass of fluid carried away, the second term is t he useful work of t he ideal windmill, t he third term —the kinetic energy of the carried away mass of fluid at the end of the working cycle, and the last term—the lost kine ­ tic energy of t he attached mass. 1) „The theory of an ideal windmill" by G. Sabinin.