GB297803A - Improvements in and relating to bladed wheels - Google Patents

Abstract

297,803. Voith, W., Voith, H., and Voith, H., (trading as Voith, J. M. [Firm of]). Sept. 28, 1927, [Convention date]. Propelling.-Paddle wheels for use in air and water acting as propellers, of the kind wherein the blades are feathered about axes parallel to the main axis and are always immersed in the medium, are characterized by the feature that the ratio of curvature of the middle crosssectional surfaces of the blades is smaller than the arithmetical mean and greater than the geometrical mean of the ratio of curvature of relative flow determined at those two points of the circle traced by the blade axis which lie on a diameter perpendicular to the direction of relative translational motion between the wheel and the fluid medium. The blades are pivoted on their axes and carry arms on the ends of which are rollers engaging a cam 5, Fig. 2, and the radius R, = PM2, Fig. 3, to which the median line of the cross-section is curved is obtained by determining first the instantaneous centre M1 for the blade P and roller Q and thence obtaining the centre M2 by imposing the translational velocity, the value M1, M2 being obtained by multiplying PM1 by the translational velocity V divided by the peripheral velocity u. This value of R is obtained at the positions C, A on a diameter perpendicular to the direction of translational motion and the final selected ratios for the blade lies between the arithmetical mean and geometrical mean of these two calculated values. The ratio is to be regarded as that for the median line of the blade section as indicated in Fig. 4. In taking the different crosssections, those of the middle surfaces of the blade lie within the limits stated above, but at the inner and outer ends these limits may be departed from.