WO2019221610A1

WO2019221610A1 - Centrifugal pump

Info

Publication number: WO2019221610A1
Application number: PCT/NO2019/050109
Authority: WO
Inventors: Tore Hystad
Original assignee: Tore Hystad
Priority date: 2018-05-16
Filing date: 2019-05-16
Publication date: 2019-11-21
Also published as: NO344723B1; EP3810314A4; NO20180691A1; EP3810314A1

Abstract

A centrifugal pump in which a centrally placed impeller/shaft system is eliminated and replaced by one or more active propellers placed tangentially in the fluid-filled pump casing. The axial force from the propeller system sets the fluid into rotation, both directly in the propeller jet and by viscous forces in the rest of the pump casing, so that tangential and radial velocity arises through the pump and thereby pressure and capacity. A method for using the centrifugal pump and a unit to be connected to the centrifugal pump are described as well.

Description

CENTRIFUGAL PUMP

The invention relates to improvements related to centrifugal pumps and, more specifi cally, to a centrifugal pump, a related method and a unit.

According to the prior art, centrifugal pumps are simple and reliable machines consist- ing of: 1) a fixed pump casing with an inlet and an outlet and a bearing housing placed centrally; 2) an impeller supported in the bearing housing and brought to ro- tate by a motor. The pumping medium is carried axially into the impeller and by way of the latter kinetic energy is imparted in the form of tangential and radial velocity. Part of the velocity is retarded in the spacious peripheral part of the casing; thereby there is a pressure rise in the medium.

A known problem with the prior art is that the impeller easily becomes clogged or damaged if the pumping medium contains larger solid or tough elements. If the solid elements are fragile, these are also easily damaged when passing the impeller. The problem has previously sought to be solved by withdrawing the impeller, with open blades, out of the fluid stream, so that it creates a rotating vortex in the pump casing that transmits the rotation to the fluid stream by viscous forces, which results in poor efficiency.

A known problem with the prior art is also that large-capacity centrifugal pumps be- come very costly to buy and operate: A low number of revolutions and high output require a strong shaft/bearing/seal system; a powerful gear box is often necessary for optimal operation. Casting and accurate machining of large metal parts such as the impeller, pump casing and shaft are expensive; maintenance/service is expensive as well.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

According to a first aspect, the invention relates to a centrifugal pump without a con- ventional, centrally placed impeller in which rotation and thereby pressure increase in the fluid is obtained by one or more active propellers placed inside the pump casing with the propeller vector approximately tangential to the rotated fluid.

The propeller may have an adapted grating on the inlet side, and the propeller with the grating on the inlet side may act directly on a limited part of the fluid, so that harmful or fragile elements in the fluid may pass the pump unobstructedly and without contact with the propeller.

The propeller, or propellers, may be placed at an optimal distance from the pump cen- tre, regardless of the pump-casing diameter. In some embodiments, the propeller(s) may be placed in a pocket (pockets) or a pipe (pipes) in the casing side or casing periphery or where a propeller nozzle or equivalent surrounds the propeller.

The centrifugal pump may have a propeller with a shaft, a bearing, a bushing, a seal, a mounting flange and a motor / motor coupling fitted together as a unit which can easily be released from the pump casing by releasing the mounting flange, so that servicing and inspection of these parts is simplified.

The centrifugal pump may have a fast-rotating propeller with an optimized pitch di- rect-coupled to a fast-rotating drive unit, so that it is possible to have a hydrodynamic step-down gearing system. The pump may be submerged in the fluid, while the motor is placed above the liquid surface on an extended propeller shaft.

The propeller may have twistable blades, possibly twistable guide blades, so that the propeller pitch can be adjusted for different or varying operating conditions.

According to a second aspect, the invention relates to a method for pumping a medi- um by using a centrifugal pump according to the first aspect of the invention. The method may comprise activating the propeller into rotating about an axis so that the fluid from the inlet is set into rotation in the pump casing and is driven out of the out- let from the pump.

According to a third aspect, the invention relates to a unit to be coupled to a pump casing for providing a centrifugal pump according to the first aspect of the invention, the unit comprising one or more of the following : a propeller, a shaft, a motor, a mounting flange, a bushing, a seal, a coupling for coupling the motor to the shaft. Examples of embodiments will now be described with reference to the accompanying drawings, in which:

Figure 1A is a section along A-A in Figure IB through a centrifugal pump according to one embodiment; Figure IB is a section along B-B in Figure 1A;

Figure 2 is a section in larger scale, showing part of a centrifugal pump according to a further embodiment;

Figures 3A to 3D are side representations, in smaller scale, of centrifugal pumps ac- cording to further embodiments with different propeller placements; Figure 4 is a sectional representation of a centrifugal pump according to a further embodiment, in which a unit is detachable from the pump casing; and

Figure 5 is a sectional representation of a centrifugal pump according to a further embodiment in use and in smaller scale.

A centrifugal pump 100 according to the invention as shown in Figures 1A and IB has a generally conventional pump casing 1, with an inlet 2 for the fluid at the centre and an outlet 3 at the periphery. An impeller/shaft system at the centre is eliminated. One (or more) motor-driven propeller(s) 4 is (are) placed in the fluid tangentially to the casing 1. When the propeller is activated in the fluid, the latter is set into rotation in the casing 1, both directly by the propeller jet and by viscous forces in the rest of the casing volume. The centrifugal force and a certain retardation of the fluid at the outlet produces pressure increase and capacity. The propeller 4 has a pitch which is adapted to the pump characteristics and the number of revolutions of the motor; a smaller fast-running motor with no step-down gearing may be used. The shaft/bearing/seal system, too, is reduced in size and simplified. The pump casing 1 is simplified and re- quires little machining.

A grating 5 as shown in Figure 2 may be placed on the inlet side of the propeller 4 and formed in such a way that larger solid, tough or fragile elements avoid contact with the latter.

Alternative placements of the tangential propeller 4 are shown in Figures 3A to 3D. As shown in Figure 4, the propeller 4 with a shaft 11, a bearing, a bushing 10, a seal 12, a mounting flange 8 and a motor / motor coupling 13 may easily be built as a unit 6 which can be easily taken out of the pump casing 1 for service/cleaning/inspection by releasing the mounting flange 8.

To optimize the pump 100 for different or continuously varying operating conditions, the propeller 4 may have a settable or continuously adjustably pitch, or adjustable guide blades 14.

The pump 100 is not self-suctioning; when placed above the liquid surface, a suction line must normally have a check valve.

When placed below the liquid surface, a watertight motor may be used, or the motor 9 may be mounted above the liquid surface with an extended shaft 15, as shown in Fig-

Claims

C l a i m s

1. A centrifugal pump without a centrally placed impeller, wherein rotation and thereby pressure increase and capacity in the fluid is obtained by one or more active propellers placed inside the pump casing with the propeller vec- tor approximately tangential to the rotated fluid.

2. A centrifugal pump according to claim 1, wherein the propeller with an

adapted grating on the inlet side acts directly on a limited part of the fluid, so that harmful or fragile elements in the fluid may pass the pump without obstruction and without contact with the propeller.

A centrifugal pump according to claim 1 or 2, wherein propellers may be placed at an optimal distance from the pump centre, regardless of the pump-casing diameter.

4. A centrifugal pump according to any one of the preceding claims, wherein the propeller is placed in a pocket or a pipe in the casing side or the casing periphery or wherein a propeller nozzle or equivalent surrounds the propel- ler.

5. A centrifugal pump according to any one of the preceding claims, wherein the propeller with a shaft, a bearing, a bushing, a seal, a mounting flange and a motor / motor coupling are fitted together as a unit which can easily be released from the pump casing by releasing the mounting flange, so that servicing and inspection of these parts is simplified.

6. A centrifugal pump according to any one of the preceding claims, wherein a fast-rotating propeller with an optimized pitch is direct-coupled to a fast- rotating drive unit, so that a hydrodynamic step-down gearing system is provided.

7. A centrifugal pump according to any one of the preceding claims, wherein the pump is submerged in the fluid, while the motor is placed above the liq uid surface on an extended propeller shaft.

8. A centrifugal pump according to any one of the preceding claims, wherein the propeller has twistable blades, possibly twistable guide blades, so that the propeller pitch may be adapted for different or varying operating condi- tions.

9. A method of pumping a medium by using a centrifugal pump according to any one of the preceding claims.

10. A method according to claim 9, which further comprises activating the pro- peller to rotate about an axis, so that the fluid from the inlet is set into rota- tion in the pump casing and driven out of the outlet from the pump.

11. A method according to claim 9 or 10, wherein the pump casing is located be- low the water surface.

12. A unit to be coupled to a pump casing for providing a centrifugal pump ac- cording to any one of claims 1 to 8, wherein the unit comprises: a propeller, a shaft, a motor, and a mounting flange for mounting of the unit to the pump casing.