US3082695A

US3082695A - Impellers, especially single vane impellers for rotary pumps

Info

Publication number: US3082695A
Application number: US820506A
Authority: US
Inventors: Buschhorn Walther
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1959-06-15
Filing date: 1959-06-15
Publication date: 1963-03-26
Anticipated expiration: 1980-03-26

Description

March 26, 1963 w. B USCHHORN 3,

IMPELLERS, ESPECIALLY SINGLE VANE IMPELLERS FOR ROTARY PUMPS Filed June 15, 1959,

FIG.3

' INVENTOR.

WALTHER auscnnorm A TTOR N 3 PU BY mmbwi ga.

Unite 3,082,695 MELLERS, ESPEQIALLY SINGLE VANE IMPELLERS FOR ROTARY PUMPS Walther Buschhorn, Pegnitz, Upper Franconia, Germany, assignor to Klein, Sehanzlin & Becker Aktiengesellschaft, Frankenthal (Pfalz), Germany Filed June 15, 1959, Ser. No. 820,506 2 Claims. (Cl. 103115) The running of rotary pumps free from oscillations and vibrations is governed primarily by the construction of the impellers employed, whereby unequal distribution of the mass of the individual elements of the impeller in the course of their manufacture has a particularly disturbing eflect. Consequently the impellers are dynamically balanced on a special machine before being fitted in the pump housing. It is known that a dynamically well-balanced impeller, particularly one having only a single vane, is not capable of ensuring perfect running of the rotary pump. This is due to the fact that the transmission of energy to the liquid being pumped is not uniform along the impeller with the result that the reaction forces resulting therefrom cause one-sided pressure of the impeller against the stuffing-box bearing, packing gaps and the like, and premature wear at these points. This hydraulic unbalance of the rotary pumps is overcome in known manner by increasing the number of vanes of the impeller. Rotary pumps for delivering liquids permeated with long-fibrous and band-like impurities are preferably equipped with single vane impellers so as to avoid the danger of choking or clogging which has to be feared. It has hitherto been endeavoured to eliminate the hydraulic unbalance which is particularly apparent in the impellers, by arranging a suitable counterweight on the back of the impeller vane. This counterweight is naturally dependent upon the number of revolutions and the size as well as the total weight of the impeller and also upon the specific gravity of the liquid to be dealt with. As it is theoretically not determinable, it has to be ascertained empirically for each impeller. It has already been attempted to eliminate the hydraulic unbalance in the case of single vane impellers by twisting the vane in spiral shape. In this known type of impellers it is also necessary to determine the shape of the vane empirically for each impeller separately.

The object of the present invention is to produce an impeller which is not open to the above-mentioned objections. This is attained by plotting the curve of the vane so that the increase in work per vane element is the same on opposite sides of the impeller. This measure becomes particularly effective in the case of an impeller provided with only a single vane extending approximately through 360, because the shape of the vane which is mostly very complicated and was hitherto ascertained only empirically, can be determined already in the course of designing. Moreover, it is likewise advantageous to plot the thickness course of the vane so that its center of mass coincides with the axis of rotations. This renders unnecessary the simultaneous casting of suitable counterweights on the back of the impeller in the manner already practiced.

To ascertain the course of the vane of the impeller according to the invention, use is made of the known Euler fundamental equation In Equation I H =the theoretical lift of the pump,

w=the angular speed of the impeller,

g=the acceleration due to gravity,

r =the radius distance of the vane at the outlet in relation to the axis of rotation of the vane,

As a guiding device is not usually arranged in front of the impeller, the last term in the bracket of the Equatlolll I: r -c will be equal to zero, so that the general formu a is obtained. Herein r=the radius distance of a vane element, in relation to the axis of rotation of the impeller,

c =the tangential component of the absolute speed c at the point of the vane element having the radius distance r.

The work of the impeller according to the invention transmitted by the vane to the liquid being pumped can be expressed by the equation:

wherein k=a constant and go=llhe angle at the center, measured between the beginning of the vane and the vane element with the radius r.

The constant k is obtained by dividing the given total blade work H and the angle at the centre o between which the vane should or is to extend.

Thus with the Equation III it is found that the vane work H increases in proportion with the angle at the center. Thereby the condition is met at the same time that the same amount of work is transmitted to the liquid being pumped by vane elements opposite to each other.

If the Equation II is treated in the same way as Equation 111 and reduced according to the (p into the form the course of the vane is clearly determined.

The tangential component c is, according to FIGURE 1, dependent both upon the radius r and also upon the angle at the center to in the form:

are inserted, when in Equation Vb V=volume of the quantity delivered, b=the width of the vane, and the value for 0,, is inserted in IV, the result will be Equation VI represents a linear difierential equation of 1st order. Its solution reads 3 The integration constant C is for =Cg 1:2, is equal to g-21r-l7)-k+ C w-21r-b 71 w V g-21r-b-k+ If this value for C is inserted in Equation VII the final solution of the differential Equation VII reads:

vr-w 'l) 7'1 In FIGURES 1 to 3 of the drawing the subject matter of the invention and the above deductions are explained in detail. FIGURE 1 is a diagram of the values used for the deduction for determining the curvature of the vane. This figure shows in particular the relationship represented by the Equation V.

FIGURE 3 shows the result of an example calculated with the aid of the above developed relationships for a single vane impeller. Here the angle p dependent upon the radial distance of the vane elements is traced graphically. The example is based on a delivery quantity of V=446.4 cubic metres per hour, a speed of 1 100 rpm, a constant impeller width of b=130= nuns. and a distance 3 at the beginning of the blade equal to 110 mms. The shape of the vane is shown in FIGURE 4 as calculated from the values of FIGURE 3.

I claim:

1. An impeller for centrifugal pumps, substantially providing hydraulic equalization over the entire operating range, comprising an impeller, the passage of which is formed by a single vane extending in the form of a spiral approximately over 360, the curve of said spiral essentially conforming to the equation =the angle at the center, measured between the beginning of the vane and the vane element with the radius r,

r=the radius distance of a vane element in relation to the axis of rotation of the impeller,

r =the radius distance of the vane at the inlet in rela tion to the axis of rotation of the vane,

V=the volume of the quantity delivered,

g: the acceleration due to gravity,

b the width of the vane,

w=the angular speed of the impeller,

k=a constant equal to the quotient of the requested theoretical pressure head H and the angle at the center (p so that the work increase per vane element is the same on opposite sides of the impeller.

2. An impeller for centrifugal pumps substantially providing hydraulic equalization over the entire operating range, comprising an impeller, said impeller being formed by a single vane which extends in the form of a spiral over essentially 360 and defines a pumping passage extending from a point adjacent the axis of the impeller to the periphery thereof, said blade defining consecutive blade elements each having a radial distance r with respect to the axis of rotation of the blade assigned to a center angle measured from the leading edge of the blade to the respective blade element, the volume of said passage determined by said center angle being equal to the quotient of the product of a predetermined angular velocity of the impeller, said radial distance r of the respective blade element, and the tangential component c of the flow of circulation on this element and the product of the acceleration due to gravity and a constant k, which constant is equal to the quotient of a predetermined theoretical pressure head H and said center angle over which the blade is to extend so that the work increase per blade element is the same on opposite sides of the impeller in any radial plane.

References Cited in the file of this patent UNITED STATES PATENTS 450,491 Nicholas et al Apr. 14, 1891 963,378 Lorenz July 5, 1910 2,245,035 Hartman June 10, 1941 2,655,868 Lindau et al Oct. 20, 1953 2,853,019 Thornton Sept. 23, 1958 FOREIGN PATENTS 1,324 Great Britain of 1863 23,234 Germany Dec. 30, 1881 340,152 Great Britain Dec. 24, 1930

Claims

1. AN IMPELLER FOR CENTRIFUGAL PUMPS, SUBSTANTIALLY PROVIDING HYDRAULIC EQUALIZATION OVER THE ENTIRE OPERATING RANGE, COMPRISING AN IMPELLER, THE PASSAGE OF WHICH IS FORMED BY A SINGLE VANE EXTENDING IN THE FORM OF A SPIRAL APPROXIMATELY OVER 360*, THE CURVE OF SAID SPIRAL ESSENTIALLY CONFORMING TO THE EQUATION