GB348032A - Improvements in or relating to rotors for axial flow hydraulic machines - Google Patents

Abstract

348,032. Hydraulic pumps ; turbines. GILL, J. H. W., 33, Earl's Court Gardens, London. Feb. 4, 1930, No. 3736. [Classes 110 (i) and 110 (iii).] In an axial-flow screw pump or reaction turbine a rotor carries blades in which the pitch gradually increases inwards from a chosen valve K at the periphery at such a rate that the pitch at any radius r is not greater than KR/r and greater than KR<a>/r<a> where R is the peripheral radius and a is the ratio of the radius of the boss to the peripheral radius. The preferred form of blade follows the law of pitch=K (R/r)<0.75> from periphery to midblade and from mid-blade inwards the pitch approaches to a higher valve KR/r which it reaches at the boss. The pitch may also vary in an axial direction one edge of a rotor blade changing according to a curve in the above region and in the neighbourhood of the other edge the pitch having a constant value equal to K. Several types of hydraulic machines are described which embody the above features. In Fig. 6 each blade K has a trunnion K<2> which is tightly gripped in the boss of the rotor which is in two halves L, L<1> bolted together by bolts L<2>. The rotor blades may be rotated slightly on either side of their normal position, when the boss is unbolted, to suit varied conditions of working and to co-operate with the outlet guide blades N which are rotatable on spindles N'. An alternative means of supporting the blades is by a slotted flange which is bolted on to the boss, the slots permitting adjustment of the blades. The blades N are designed to recover pressure energy and the curvature of the blades follows the law S tan gamma = (1ÀS) tan # where and gamma represent the angles made with a surface normal to the stream at any radius by the outlet edge of the rotor blade and by the inlet edge of the outlet guide blade, respectively, S being the slip ratio at any radius. The cross-sections of the guide blades are stream-lined. The spacing between the rotor and guide blades is normally small but may be increased where solid matter is suspended in the fluid flowing through. In Fig. 9, each outlet guide blade is formed in two parts O, O<1>, the upper part being fixed in the casing whilst the lower part O<1> is provided with a circular flange O<2> for slight rotational adjustments or for removal of the part O<1> for replacement purposes. Where solids are contained in the fluid each inlet blade is made up of a series of tongues P bolted to narrow plates P<1> extending radially inward from the casing and joined together at the axis. Fig. 5 illustrates a reaction turbine the rotor G of which is designed according to the variable pitch law of the invention. The inflow through the annular passage H<1> is controlled by guide blades J which are simultaneously adjustable by means of a rotatable slotted crown J<1>. The rotor is adjustable axially as indicated by lotted lines. In pumps and turbines of the above types the inlet and outlet guide blades may be fixed to a removable liner or the inlet guide blades may be arranged so that the rotor may be withdrawn axially between them. In a modified pump outlet guides are dispensed with and the casing is trumpetshaped with a central core. The inlet guide blades are adjustable. In a further arrangement the pump rotor discharges fluid into an oppositely-rotating rotor the two rotors being coaxial. The inlet and outlet casings which are suitably curved are provided with stream-lined fins which are fixed diametrically across the casings. The radius of the rotor boss lies between one-fifth and three-quarters of the peripheral radius.