GB2054748A

GB2054748A - Pump impeller

Info

Publication number: GB2054748A
Application number: GB8013566A
Authority: GB
Original assignee: Deutsche ITT Industries GmbH; ITT Industries Inc
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1979-04-27
Filing date: 1980-04-24
Publication date: 1981-02-18
Also published as: GB2054748B; IT8021666A0; FR2455197B1; SE426976B; IT1193387B; FI800864A; NL8002322A; FR2455197A1; JPS55160195A; SE7903729L; JPH0128234B2; DE3015188A1; CA1146809A

Abstract

In order to diminish the risk of clogging during pumping of, for instance, sewage, the vane (1) is formed with a varying thickness along its length. The speed reduction in the flow channel between the vane inlet and the vane outlet is then limited, since the channel only increases in cross-section by a predetermined limited amount towards the outlet and pressure decreases within the channel are minimised. The vane (1) can be made hollow to decrease balancing problems. <IMAGE>

Description

SPECIFICATION Pump Impeller The invention relates to an impeller for centrifugal and axial pumps, and in particular 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 a part of one or several turns. The channel which is formed by the vane axially limited by cover discs which are parts of the impeller or the surrounding pump housing.

Pump impellers of the type referred to are above all used for pumping of liquids containing solid bodies, for instance sewage water. The advantage is that the risk for clogging decreases il one instead of several vanes are used. Sometimes a certain minimum size of through passage in a pump impeller for sewage pumps is prescribed by Authorities. This can only be fulfilled by single vane impellers if resonable dimensions should be kept.

In previously known impellers of the single vane type, the vane is formed with a constant thickness from the leading edge by the pump inlet to the trailing edge by the pump outlet. One such impeller is shown in the Swedish published patent application 7806198-3.

Such impellers have however certain disadvantages. As the vane thickness is constant, the channel which is formed by the vane has an essentially increasing cross-section towards the pump outlet. This increase, which is most significant shortly after the inlet, means a reduction of flow speed and a local pressure decreases (diffusion) which creates undesirable turbulence and sometimes cavitation. Besides, the risks increase that solid bodies will stick to the vane, especially on its leading edge, and thus decrease the free through passage which means risks for clogging and decreasing efficiency. With clogging of the impeller the load on the driving unit increases, thus sometimes releasing the overload protection and generating expensive stoppages and service work.

An object of the present invention is to provide an impeller of the single-vane type in which the speed reduction of the flow is reduced as much as possible.

According to the present invention there is provided a single vane impeller for use in centrifugal and axial pumps, wherein the thickness of the vane varies such that a channel defined by the vane and cover discs of the impeller or a surrounding pump housing has cross-section which increases towards the outlet by a predetermined limited amount whereby diffusion of the pumped medium within the impeller is prohibited.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows an axial section through an embodiment of impeller according to the present invention; Fig. 2 shows a radial section taken along line Il-Il of Fig. 1, and Fig. 3 shows a perspective view of the impeller of Figs. 1 and 2 when inverted.

In the drawings, an impeller vane 1 has a leading edge (inlet edge) 2 and a trailing edge (outlet edge) 3. A channel 4 is formed by the vane 1 and cover discs 5. There is a hole 6 for an impeller shaft (not shown).

Unlike known impellers of the single vane type, the impeller according to the present invention has a vane 1 with varying thickness in the flow direction. This means that the channel 4, which is formed by the vane 1 and the cover discs 5, has a cross-section which only increases towards the outlet by a limited amount thus diminishing the risks of clogging.

Known impellers of the single vane type often accumulate a layer of particles near the leading edge 2. This layer often gives the vane a new profile which is somewhat like the vane profile according to the present invention. The disadvantages, except for the clogging tendency, are that the risks for overloading increase considerably and that a strong unbalance occurs in the impeller which brings about increasing strain on the bearings etc., causing a shorter length of life. According to the present invention, the right profile is formed from the beginning and the impeller is balanced accordingly.

In a preferred embodiment the vane is hollow in order to diminish its weight and thus the need for balancing material.

The vane 1 may be formed differently according to the needs. Different optimal conditions are valid for different types of pumped medium, impeller speed, volume flow and head.

Depending on these criteria the impeller is formed with a more or less expressed bulb form and with single or double bent sides. The vane may have a single bent outside and a double bent inside, or single bent in- and outsides, or double bent in and outsides. A common feature for all embodiments is the varying thickness of the vane. The bulb form may be such that the greatest thickness of the vane is between 200 and 400 from the leading edge 2.

The impellers of the present invention involve radically diminished clogging risk, an increased liquid flow through the impeller with a resultant improved efficiency and an improved balancing of the impeller without abandoning the minimum free through passage dimensions.

Claims

1. A single vane impeller for use in centrifugal and axial pumps, wherein the thickness of the vane varies such that a channel defined by the vane and cover discs of the impeller or a surrounding pump housing has cross-section which increases towards the outlet by a predetermined limited amount whereby diffusion of the pumped medium within the impeller is prohibited.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pump Impeller The invention relates to an impeller for centrifugal and axial pumps, and in particular 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 a part of one or several turns. The channel which is formed by the vane axially limited by cover discs which are parts of the impeller or the surrounding pump housing. Pump impellers of the type referred to are above all used for pumping of liquids containing solid bodies, for instance sewage water. The advantage is that the risk for clogging decreases il one instead of several vanes are used. Sometimes a certain minimum size of through passage in a pump impeller for sewage pumps is prescribed by Authorities. This can only be fulfilled by single vane impellers if resonable dimensions should be kept. In previously known impellers of the single vane type, the vane is formed with a constant thickness from the leading edge by the pump inlet to the trailing edge by the pump outlet. One such impeller is shown in the Swedish published patent application 7806198-3. Such impellers have however certain disadvantages. As the vane thickness is constant, the channel which is formed by the vane has an essentially increasing cross-section towards the pump outlet. This increase, which is most significant shortly after the inlet, means a reduction of flow speed and a local pressure decreases (diffusion) which creates undesirable turbulence and sometimes cavitation. Besides, the risks increase that solid bodies will stick to the vane, especially on its leading edge, and thus decrease the free through passage which means risks for clogging and decreasing efficiency. With clogging of the impeller the load on the driving unit increases, thus sometimes releasing the overload protection and generating expensive stoppages and service work. An object of the present invention is to provide an impeller of the single-vane type in which the speed reduction of the flow is reduced as much as possible. According to the present invention there is provided a single vane impeller for use in centrifugal and axial pumps, wherein the thickness of the vane varies such that a channel defined by the vane and cover discs of the impeller or a surrounding pump housing has cross-section which increases towards the outlet by a predetermined limited amount whereby diffusion of the pumped medium within the impeller is prohibited. An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows an axial section through an embodiment of impeller according to the present invention; Fig. 2 shows a radial section taken along line Il-Il of Fig. 1, and Fig. 3 shows a perspective view of the impeller of Figs. 1 and 2 when inverted. In the drawings, an impeller vane 1 has a leading edge (inlet edge) 2 and a trailing edge (outlet edge) 3. A channel 4 is formed by the vane 1 and cover discs 5. There is a hole 6 for an impeller shaft (not shown). Unlike known impellers of the single vane type, the impeller according to the present invention has a vane 1 with varying thickness in the flow direction. This means that the channel 4, which is formed by the vane 1 and the cover discs 5, has a cross-section which only increases towards the outlet by a limited amount thus diminishing the risks of clogging. Known impellers of the single vane type often accumulate a layer of particles near the leading edge 2. This layer often gives the vane a new profile which is somewhat like the vane profile according to the present invention. The disadvantages, except for the clogging tendency, are that the risks for overloading increase considerably and that a strong unbalance occurs in the impeller which brings about increasing strain on the bearings etc., causing a shorter length of life. According to the present invention, the right profile is formed from the beginning and the impeller is balanced accordingly. In a preferred embodiment the vane is hollow in order to diminish its weight and thus the need for balancing material. The vane 1 may be formed differently according to the needs. Different optimal conditions are valid for different types of pumped medium, impeller speed, volume flow and head. Depending on these criteria the impeller is formed with a more or less expressed bulb form and with single or double bent sides. The vane may have a single bent outside and a double bent inside, or single bent in- and outsides, or double bent in and outsides. A common feature for all embodiments is the varying thickness of the vane. The bulb form may be such that the greatest thickness of the vane is between 200 and 400 from the leading edge 2. The impellers of the present invention involve radically diminished clogging risk, an increased liquid flow through the impeller with a resultant improved efficiency and an improved balancing of the impeller without abandoning the minimum free through passage dimensions. Claims

2. An impeller as claimed in claim 1, wherein the vane has a bulb form with its greatest thickness 20---40" from the leading edge of the vane.

3. An impeller as claimed in claim 1 or claim 2, wherein the vane is hollow.

4. An impeller as claimed in claim 1 or claim 2, wherein the vane is solid.

5. An impeller as claimed in claim 1, wherein the vane has a single bent outside and double bent inside.

6. An impeller as claimed in claim 1, wherein the vane has single bent in- and outsides.

7. An impeller as claimed in claim 1, wherein the vane has double bent in- and outsides.

8. A single vane impeller for use in centrifugal and axial pumps substantially as herein described with reference to and as illustrated in the accompanying drawings.

9. A pump including a single vane impeller as claimed in any one of the preceding claims.