EP2898220B1

EP2898220B1 - Pump device

Info

Publication number: EP2898220B1
Application number: EP13725717.6A
Authority: EP
Inventors: Allan JESSEN
Original assignee: Grundfos Holdings AS
Current assignee: Grundfos Holdings AS
Priority date: 2012-09-18
Filing date: 2013-05-30
Publication date: 2016-11-30
Anticipated expiration: 2033-05-30
Also published as: CN103930682B; KR20150032144A; US20150233383A1; CN103930682A; KR101727655B1; WO2014044422A1; EP2898220A1; RU2597382C1

Description

The invention relates to a pump device according to the preamble of claim 1 and a pump system.
Axial flow or mixed flow pumps are typically used where large amounts of water have to be moved, for example for removing water from flooded areas. These pumps may be equipped with motors with a power range from 10 kW to 1 MW and usually are placed inside a pipe or column pipe such that the pipe coaxially surrounds the pump. The column pipe in particular extends in vertical direction. At one end of the pipe the pump sucks water in, and at the other end of the pipe the water is pumped out with a throughput lying in the range from 5 m³/min to 700 m³/min and at lifting height between 2 meters and 9 meters. For example, a typical throughput may be 180 m³/min at a lifting height of 3 meters using an electrical pump with 140 kW power.
These large pumps consume a lot of electrical energy. Most of the energy is imparted as energy to the water to be pumped, but a part of the energy is lost due to turbulence of water in a gap between a guide tube (volute) of the pump and an inner wall of the pipe. As the water passes the end of the guide tube it experiences a sudden change (expansion) in diameter and turbulent flow arises, i.e. swirls that in some cases rotate in a direction against the pumping direction. Depending on the pipe and the pump this gap can be in the range of 40 millimeters to 80 millimeters.
However, in prior art pump systems, it is not possible to customize the diameter of the guide tube closely to the diameter of the inner wall of the pipe so as to close the gap and avoid turbulences. The reason for not having a cast iron guide tube diameter close to the inner pipe diameter is that the pump weighing between 2 and 10 tons typically has to be lowered into the pipe via a crane, up to 20 meters down in the pipe. If the fit is too narrow, then problems will arise during lowering the pump by means of the crane.
FR 1 121 319 discloses a pump mounted inside a pipe whereas the impeller is surrounded by a tubular housing. The tubular housing has a smaller outer diameter then the inner diameter of the pipe and in the ring shaped space between the housing and the pipe moveable flaps are arranged which allow to close the ring shaped gap when the pump is running and to open the gap when the pump is not running. However, this pump is not a large axial flow pump which is insertable into a pipe as described before. EP 2 378 127 A2 discloses a pump arranged inside a shut-off valve. This pump is not inserted through the inlet or outlet pipe as described above.
It is an object of the present invention to provide a pump device and corresponding pump system employing such a pump device according to which energy loss due to turbulences in the outlet flow of the pumped water is avoided.
This object is solved according to the present invention by a pump device having the features according to claim 1 and a pump system having the features according to claim 14. Preferred embodiments of the invention are defined in the respective dependent claims. According to the present invention, a pump device to be mounted coaxially in a pipe in particular a column pipe, is provided, the pump device comprising an axial or mixed flow pump with a volute or guide channel or guide tube, respectively, arranged around a propeller portion of the pump device and preferably being conically widened towards an outlet portion or outlet end of the guide tube and of the pump, wherein, in mounting position, a gap may be formed between an outlet end of the guide tube and the surrounding pipe. In case that the surrounding pipe is a column pipe extending in vertical direction, the outlet end of the guide tube is the upper end. The guide tube has an elastic portion at its outlet end, which elastic portion is bendable in radial direction relative to the longitudinal axis, i. e. the rotational axis of the pump device. This means the elastic portion is bendable towards the pipe in order to at least partially, in particular completely, close the gap during operation of the pump device. According to the inventive configuration, the outlet end of the volute or guide tube is made elastic and bendable towards the inner wall of the pipe. Thus, as the gap between the inner wall of the pipe and the guide tube is decreased or even disappears, the turbulence which usually would occur during operation of the pump when fluid, in particular water passes through the pump outlet in the vicinity of the gap is substantially decreased or even avoided. This makes the pump more efficient since the energy loss due to turbulences occurring at the gap is avoided, too. Specifically, computer simulations and practical measurements have shown that an increase in energy efficiency of up to 2 percent points may be achieved due to the inventive configuration.
According to a preferred embodiment, the elastic portion is bendable by a hydraulic pressure of a fluid being pumped to the outlet portion or outlet end.
According to a further preferred embodiment, the elastic portion is bendable against an inner wall of a surrounding pipe when the pump placed inside the pipe is running. However, it should be mentioned that it is a design option how far the elastic portion is deflected in radial direction and towards the inner wall or if it even is fully deflected so as to contact the inner wall and close the gap completely. Although full closure gives the best effect, it is not needed in order to obtain a reduction in the turbulent flow. A gap size of, for example, 10 to 20 mm between the expanded elastic portion and the inner wall of the pipe will still be able to reduce the turbulence of the flow. According to an example, a pump with a maximum pressure of 1 bar (relative to the input pressure) in the column pipe may comprise an elastic portion being designed to fully deflect at 0.2 bar.
According to yet a further preferred embodiment the elastic portion also is expandable.
Preferably, the elastic portion is formed by a rubber ring mounted at an outlet end of the volute or guide tube, respectively. The elastic ring is preferably mounted on the axial edge of the pump guide tube and is bendable and preferably expandable. With this configuration, the turbulent flow is transformed into laminar flow because the ring prevents a sudden change in diameter.
It is advantageous, if the elastic portion is bendable at a hydraulic pressure of at least 0.2 bar. Specifically, during no flow or low flow through the pump, the elastic portion will not deform, because the hydraulic forces are low. But during higher flow and higher pressure, as for example above 0.2 bar, or preferably between 0.5 and 5 bars, the ring will bend radially outwards due to a radial hydraulic force component from the pumped fluid. This force component will press the elastic portion towards the inner wall of the column. Hereby, the gap is closed, and turbulence is prevented.
Further, the walls or columns of the pipe are preferably made of steel, plastic, or concrete.
According to still a further preferred embodiment, the pipe has a diameter between 300 mm and 2500 mm, preferably between 500 mm to 2200 mm and the pump is dimensioned that it fits into such pipe. This means the diameter of the pump device may be adapted to a certain pipe diameter or to a range of pipe diameters. However, the dimension of the elastic portion depends on the specific diameter of the column pipe.
Preferably, the elastic portion has a height such that when the pump placed in a pipe is running it is able to contact the inner wall of the surrounding pipe.
Further, it is preferred that the elastic portion is made of an elastomer, for example rubber, in particular, of nitrile butadiene rubber or ethylene propylene diene monomer rubber or natural rubber due to their good abrasive properties. However, also other materials may be used as long as they are elastic and bendable and are able to withstand thousands of bendings over a period of time.
The elastic portion may preferably have a Shore A hardness in the range of 40 to 90 so as to have the right coefficient of expansion.
According to a further preferred embodiment, the elastic portion has a first axial end adjacent to the guide tube and an opposed second axial end, wherein the thickness of the elastic portion at the upper end is lower than at the lower end. When the pump device is arranged in a column pipe extending in vertical direction, the first axial end is the upper end and the second axial end is the lower end. Preferably the inner surface of the elastic portion follows the surface trajectory (the guide tube angle) of the guide tube. By this the elastic portion will not disturb the flow at only low flow where no or only small radial deflection occurs. By giving the elastic portion the same thickness as the guide tube in the contact area with the guide tube, mechanical fixation of the ring is facilitated.
According to yet a further preferred embodiment, the elastic portion is connected to the guide tube by gluing or by a mechanical connection, in particular, by screws or bolts. A further connection between the guide tube and the elastic portion may be to vulcanize the rubber directly onto the guide tube.
It may also be advantageous if the elastic portion has two parts, in particular two halves, each having the shape of half ring. Alternatively, the elastic portion may be one fully continuous ring. Typically, the ring will be mounted on a new pump from the factory, but retrofitting on old pumps may also be possible.
Further according to the present invention, a pump system comprising a pump device as outlined above and a surrounding pipe is provided, the pump device being mounted coaxially in the pipe, in particular the column pipe.
The above features and advantages of the present invention will become yet more apparent upon reading the following detailed description along with the accompanying drawings.

Fig. 1: is a side view of a pump system according to an embodiment of the invention;
Fig. 2: is a sectional view of a detail of the pump system shown in Fig. 1;
Fig. 3A - 3D: are illustrations of several flow situations with and without an elastic portion on the guide tube.

The pump system 1 comprises a pump device 2, which in this case is a submersible axial flow pump which is arranged in the center of a pipe in form of a column pipe 3. Specifically, the longitudinal axis 4 of the pump device 2 is arranged coaxially to the longitudinal axis of the pipe, in this case the column pipe 3. An axial flow pump in the meaning of the invention is a pump which propeller produces an axial flow. The invention may also be carried out with a mixed flow pump which uses an impeller which at least partly produces a radial flow which is deflected in axial direction by the surrounding volute or guide channel or guide tube, respectively. Thus the mixed flow pump is a combination or compromise between a radial and an axial flow pump. The pump device 2 comprises an inlet portion 5 at its first axial end, in this case the lower end at which water enters the pump. Inside the pump housing 6 a propeller portion with diffuser vanes and an axial propeller is arranged. Also, the pump device 2 comprises a volute or guide tube 7 which conically widens towards an outlet portion 8 of the pump device 2. Further, an electrical motor 10 is provided which may be connected to electricity via the electrical power supply cables 9, 9'. The guide tube 7 at its outlet end, in this case at its upper end at the outlet portion 8 of the pump device 2 is provided with an elastic portion 12. As can be seen particularly well in the portion surrounded by a circle on the left side of the drawing, there is a gap 11 between the elastic portion 12 and the inner wall 13 of the column pipe 3. During operation of the pump device 2, when fluid or water flows from the inlet portion 5 through the pump device 2 towards the outlet portion 8, the hydraulic forces will cause the elastic portion 12 to deflect radially outwards towards the inner wall 13 of the column pipe 3 so as to eventually contact the inner wall 13 and close the gap 11. When the gap 11 is closed or even if it is reduced in its width by deflection of the elastic portion 12, turbulences usually occurring in this region will be reduced or even completely prevented. Instead, a laminar water flow will occur when water leaves the pump device 2 at the outlet portion 8. Thereby, energy loss due to otherwise occurring turbulences is avoided and the pump device 2 may be operated more efficiently.
Fig. 2 is a sectional view of a detail of the pump system 1 shown in Fig. 1, specifically, illustrating the connection area between the guide tube 7 and the elastic portion 12. The guide tube 7 and the elastic portion 12 are connected to each other by gluing together two overlapping parts 14, 14' of the guide tube 7 and the elastic portion 12. As can be seen from the figure, the elastic portion 12 has a first axial end, the lower end 15 which is directly adjacent to and overlapping an upper end 16 of the guide tube 7, the thickness of which is higher than at an axial second end, the upper portion 17 of the elastic portion 12. The inner surface 18 of the elastic portion 12 follows the surface trajectory of the guide tube 7 and, thus, will not disturb the flow of fluid or water during operation of the pump device 2 when the flow is low and there is only low or no deflection of the elastic portion 12.
Fig. 3A to 3D are four illustrations showing several flow situations with and without an elastic portion 12 on the guide tube 7. Specifically, Fig. 3A shows a pump system 1 with a pump device 2 not according to the invention and having a guide tube 7 without an elastic portion 12 which is located within a column pipe 3. Here, the pump device 2 is not operated and there is no flow of water at all. However, in Fig. 3B, the same pump device 2 shown in Fig. 3A now is in operation where water is pumped by rotation of the diffuser vanes 20 from an inlet portion 5 to an outlet portion 8. In the area where the gap 11 is formed between the inner wall 13 of the column pipe 3 and the guide tube 7, the turbulences 18 will occur. In Fig. 3C, another pump system 1 is shown which differs from the one shown in Fig. 3A in that according to the invention an elastic portion 12 is provided at an upper end 16 of the guide tube 7. When the pump is not being operated, as shown in Fig. 3C, there will still be a gap 11 between the inner wall 13 of the column pipe 3 and the elastic portion 12. However, when the pump device 2 is operated, as shown in Fig. 3D, the hydraulic force of the water flowing from the inlet portion 5 towards the outlet portion 8 will press the elastic portion 12 towards the inner wall 13 of the column pipe 3 so that the gap 11 will disappear. Thus, instead of turbulences 18 occurring, there will be a laminar flow 19 of water in this area.

Claims

Pump device (2) to be mounted coaxially in a pipe (3), the pump device (2) comprising an axial or mixed flow pump with a guide tube (7) arranged around a propeller portion of the pump device (2) characterized in that the guide tube (7) has an elastic portion (12) at its outlet end (16) which elastic portion (12) is bendable in radial outward direction.
Pump device (2) according to claim 1, characterized in that the elastic portion (12) is bendable by a hydraulic pressure of a fluid being pumped to the outlet portion (8).
Pump device (2) according to claim 1 or 2, characterized in that the elastic portion (12) is bendable against an inner wall (13) of the surrounding pipe (3) when the pump device (2) is running.
Pump device (2) according to any of claims 1 to 3, characterized in that the elastic portion (12) is expandable.
Pump device (2) according to any of claims 1 to 4, characterized in that the elastic portion (12) is formed by an elastic ring mounted at the outlet end (16) the guide tube (8).
Pump device (2) according to any of claims 1 to 5, characterized in that the elastic portion (12) is bendable at a hydraulic pressure of at least 0.2 bar.
Pump device (2) according to any of claims 1 to 6, characterized in that pump device (2) has such an outer diameter that the pump device (2) fits in a pipe having a diameter between 300 mm to 2500 mm.
Pump device (2) according to any of claims 3 to 7, characterized in that the elastic portion (12) has a height such that when the pump device (2) is running it is able to contact the inner wall (13) of the pipe (3).
Pump device (2) according to any of claims 1 to 8, characterized in that the elastic portion (12) is made of rubber, in particular, of nitrile butadiene rubber or ethylene propylene diene monomer rubber or natural rubber.
Pump device (2) according to any of claims 1 to 9, characterized in that the elastic portion (12) has a Shore A hardness in the range of 40 to 90.
Pump device (2) according to any of claims 1 to 10, characterized in that the elastic portion (12) has a first axial end (15) adjacent to the guide tube (7) and an apposed second end (17) wherein the thickness of the elastic portion (12) at the second end (17) is lower than at the first end (15).
Pump device (2) according to any of claims 1 to 11, characterized in that the elastic portion (12) is connected to the guide tube (7) by gluing or by a mechanical connection, in particular, by screws or bolts.
Pump device (2) according to any of claims 1 to 12, characterized in that the elastic portion (12) has two parts, in particular two halves.
Pump system (1) comprising a pump device (2) having the features of any one of claims 1 to 13 and a surrounding pipe (3), the pump device (2) being mounted coaxially in the pipe (3).