CA1146809A

CA1146809A - Impeller

Info

Publication number: CA1146809A
Application number: CA000350663A
Authority: CA
Inventors: Magnus Erikson
Original assignee: ITT Industries Inc
Current assignee: ITT Inc
Priority date: 1979-04-27
Filing date: 1980-04-25
Publication date: 1983-05-24
Also published as: IT1193387B; FI800864A; FR2455197A1; GB2054748B; SE7903729L; JPS55160195A; JPH0128234B2; FR2455197B1; GB2054748A; NL8002322A; DE3015188A1; SE426976B; IT8021666A0

Abstract

M. Erikson-l (Revision) ABSTRACT OF THE DISCLOSURE
The invention is related to an impeller for a single vane type of centrifugal pump. In order to diminish the risk of clogging of the pump when pumping a fluid having a large impurity content, a vane having varying thickness is provided. In this manner, the speed reduce in the channel is limited resulting in a favorable flow pattern. Addition-ally, the vane may be made hollow in order to reduce unbalance problems.

Date: March 17, 1980

Description

M. Erikson-l 1146~UD9 (Revision) IMPROVED IMPELLER
BACKGROUND OF THE INVENTION
This invention is directed to an impeller for centrifugal pumps particularly for use in pumping of fluent media. More precisely, the invention is directed to an impeller of the so called single vane type, which means that the impeller is provided with one single vane which goes helically around the impeller either partly or entirely and perhaps more than once around the im-peller. The channel which is formed by the vane in the surrounding pump housing is axially limited by cover discs which are parts of the impeller.
Pump impellers of the type referred to are primarily ; used for pumping liquids containing solid bodies, for instance, sewerage water. The advantage of this config-uration i8 that the risk of clogging decreases if only one vane is used. In some instances, a certain minimum thrulet in a pump impeller for sewerage pumps is pre-scribed by Governmental regulation. Such thrulet can only be fulfilled by a single vane impeller if reason-able dimensions are to be maintained.
Previously known impellers of the single vane typehave the vane formed with constant thickness from the leading edge near the pump inlet to the trailing edge near the pump outlet. One such impeller of this type is shown in the Swedish published patent application number 7,806,198-3.

-2- M Erikson-l Such impellers have certain disadvantages. As the vane thickness is constant, the channel which is formed by the vane has a constantly increasing cross-section towards the direction of the pump outlet. This steady increase is most pronounced near the inlet. This rapid increase in cross-sectional area results in a rapid decrease in fluid velocity and local pressure which may cause an undesirable turbulence and possible cavitation. Additionally, an increased risk of solid body collection exists especially at the leading edge of the vane which would result in a decreased cross-sectional area at that location causing increased probability of clogging and/or decreased pump efficiency.
Any clogging of the impeller results in an increased load on the driving unit, which sometimes triggers the overload protection devices resulting in work stoppage and requiring servicing of the pump.
OBJECTS OF THE INVENTION
It is an object of this invention to obtain an impeller of the single channel type where the speed reduction of the fluid flow is avoided as much as possi-ble.
Another object of the invention is to achieve elimination of fluid diffusion in the area near the impeller.
SUMMARY OF THE INVENTION
This i8 achieved according to the invention in that an impeller for use in a centrifugal pump comprises cover discs connected to each other by a single vane in that the discs and the vane define a channel having an inlet coaxial with the impeller axis of rotation and an outlet eccentric to this axis, and in that the thickness of the vane varies in the direction of flow such that the cross section of the channel taken normal to the axis of flow through the channel is at most only slightly increasing.

- 11468~9 M. Erikson-l

3 (Revision) BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described more specifically here-inafter with reference to the enclosed drawings wherein:
Fig. 1 shows an axial section through an impeller, according to the invention.
Fig. 2 shows a radial section; and Fig. 3 shows a perspective view of the impeller.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the drawings, 1 designates the impeller vane having a leading edge (inlet) 2 and a trailing edge (outlet) 3, 4 designates the channel formed by the vane 1 and the cover discs 5, and 6 designates a hole through which the impeller shaft extends.
Unlike previously known impellers of the single vane type, an impeller according to the present invention has a vane 1 with varying thickness in the direction of flow. Ihis means that, as previously mentioned, the channel 4, which is formed by the vane 1 and the cover discs 5, has a cross-section which is only slightly in-creasing in the direction of the outlet, thus reducingthe aforementioned risks of clogging.
Known impellers of the single channel type often get a layer of p~rticles accumulating near the leading edge 2. This layer often gives the vane a new profile which is undesirable because of the increased clogging tendency, resulting in the risk of overload. In addi-tion to the overload risk, such deposits often result in unbalancing of the impeller resulting in increased strain and wear on the bearings resulting in shorter life span.
According to the invention, 8 proper profile is formed initially in the valve with the result that no deposits form on the impeller resulting in potential c~ogging or rapid deterioration of the pump.
In a preferred embodiment of the invention, the vane is hollow in order to diminish its weight and thus the need for careful balancing of the pump parts.

~ .!

` ~146809 M Erikson-l The vane 1, may be formed differently according to the optimal design conditions of the pump. Different conditions may be required where the pump medium, impeller speed, volume of flow and fluid head are varied. Depend-ing on these criteria, the impeller is formed with a moreor less pronounced bulbform near the leading edge of the vane 1 and with double or single bent sides. A
common feature for all embodiments are the different thicknesses of various portions of the vane. In a pre-ferred embodiment, the vane 1 has a bulb form having itsgreatest thickness located at a portion of the vane 1 between 20 to 40 displaced from the front edge 2 of the vane 1.
According to this invention, an impeller may be designed which has a radically diminished risk of clogging, and increased liquid thruput, having better flow efficiency and a better balancing of the impeller without abandoning the minimum free thrulet.

Claims

M. Erikson - 1 WHAT IS CLAIMED IS:

1. An impeller for use in a centrifugal pump, said impeller comprising cover discs connected to each other by a single vane, said discs and said vane defining a channel having an inlet coaxial with the impeller axis of rotation and an outlet eccentric to said axis, the thickness of said vane varying in the direction of flow such that the cross-section of the channel taken normal to the axis of flow through the channel is at most only slightly increasing.

2. The impeller according to claim 1 wherein the vane has a bulbform having its greatest thickness located at a portion of the vane between 20° to 40°
displaced from the front edge of the vane.

3. An impeller according to claim 1 wherein the vane is hollow.

4. An impeller according to claim 1 wherein the vane is solid.

5. An impeller according to claim 1 wherein the vane has a single curved pressure surface and a double curved suction surface.

6. The impeller claimed in claim 1 wherein the vane has a single curved suction surface and a single curved pressure surface.

7. The impeller according to claim 1 wherein the vane has a double curved suction surface and a double curved pressure surface.