EP1348871A1 - Low flow centrifugal pump with increased suction height - Google Patents

Abstract

The pump consists of a number of wheels mounted on the same shaft, each wheel having two flange faces (19) which contain channels and blades. The channels and blades conduct a fluid from an entry at the wheel hub to an output orifice (15) at the periphery. A specifically profiled indentation (17) is located on the flange opposite to entry to drive bubbles

Description

The invention relates to hydraulic pumps and in particular pumps hydraulics for large suction heights and low flow.

We consider that a suction height greater than 4 meters is a great suction height. Furthermore, it is considered that a flow rate less than 400 l / h is a low flow. A high suction head and a low flow rate are conditions for frequently encountered on pumps fitted with recovery of rainwater used to supply toilets or washing machines wash. The fluid flow rates are typically 50 to 400 l / h in such cases and the suction heights are between 4 and 7 m.

During suction, the pressure at the inlet of a pump is low. Pressure drops sometimes until air bubbles appear in the fluid. The fluid speed is reduced for low flow rates. The bubbles are then not entrained with the fluid in the pump. Sometimes there is an accumulation of bubbles at the inlet of the pump. The fluid can no longer flow and the inlet pressure drops. This then generates a pump priming.

It is also known to use a jet pump with hydro-ejector. This pump is not very sensitive to defusing under conditions of low flow and large suction height. However, this pump is particularly noisy, which is particularly disabling in certain applications.

GB-A-877 878 discloses a self-priming pump comprising a impeller provided at its periphery, in a radial direction, with a series of notches or irregularities in order to excite turbulence during priming. Such irregularities have little or no effect on normal pump operation after boot.

JP-A-10 318180 discloses a self-priming pump, comprising a impeller, fluid passages isolated from each other by walls and agitating parts open on the surface of the fluid inlet side. These parts mix the fluid with air from the fluid inlet side.

FR-A-742 839 discloses a pump rotor constituted by blades connected two two by side cheeks so as to form closed channels.

A disadvantage associated with such wheels is that the bubbles do not have the dimension as high as possible at a radial opening, so that their evacuation is not facilitated.

In addition, the geometries of these wheels do not favor the recovery of the fluid. coming out of a radial opening of the wheels.

Furthermore, the pump wheels described above are not particularly adapted to be mounted in a pump with a large suction height, i.e. greater than 4 meters.

In addition, these wheels are not particularly suitable for being mounted in a low flow pump, that is to say having a flow rate between 50 and 400 l / h.

The pumps described above are also single-cell pumps, that is to say with a wheel in a scroll.

There is therefore a need for a wheel and a pump which resolve one or more many of these problems.

The subject of the invention is therefore the design of a new wheel allowing a correct operation of the pump with high suction head and low flow rate, without hydro-ejector.

The invention thus relates to a hydraulic pump wheel comprising a fluid inlet on one side; a radial opening; at least one fluid channel joining the fluid inlet to the radial opening; a setback on the outskirts of the wheel, on the other face of the wheel, angularly offset from the opening.

According to a variant, the wheel of claim 1, characterized in that the angle leakage, between the offset and the periphery of the wheel in the direction of rotation of the wheel is between 10 and 40 ° and preferably between 15 and 25 °.

According to yet another variant, the angle of attack, between the offset and the periphery of the wheel in the direction of rotation of the wheel, is between 80 and 100 °.

According to another variant, the recess present, along the axis of rotation of the wheel, a thickness between 40 and 60% of the thickness of the channel.

According to yet another variant, the recess has a depth along a radius between 9 and 14% of the diameter of the wheel.

It can also be provided that the recess has an angular length corresponding to between 80 and 120% of the angular length of the fluid passage.

According to a variant, the blade defined between two adjacent channels presents at in the vicinity of the fluid inlet, a radius of curvature between 2 and 6 mm.

According to another variant, the wheel has a first flange on which the entrance is spared; a second flange on which the recess is provided; at least one blade and the first and second flanges delimiting one of said channels.

According to another variant, the channel has an angle of divergence understood between 7 and 15 °, preferably between 8 and 9 °.

The invention also relates to a pump having at least one such wheel.

According to a variant, the pump has a suction height greater than 4 meters.

According to another variant, the pump has a flow rate between 50 and 400 l / h

• figure 1, une vue en section transversale d'un exemple de pompe dans laquelle on peut monter une roue selon l'invention ;
• figure 2 et 3, des vues en perspective d'un exemple de roue de pompe selon l'invention ;
• figure 4, une vue en section transversale avant un décrochement d'une face d'évacuation de la roue ;
• figure 5, une vue en section transversale au niveau d'un décrochement d'une face d'évacuation de la roue ;
• figure 6, une vue en section transversale suivant un plan comprenant l'axe de la roue ;
• figure 7, un agrandissement d'un décrochement de la figure 5, représentant une géométrie préférentielle de ce décrochement.

Other characteristics and advantages of the invention will appear on reading the following description of embodiments of the invention, given by way of example and with reference to the accompanying drawings which show

• Figure 1, a cross-sectional view of an example of a pump in which a wheel according to the invention can be mounted;
• FIGS. 2 and 3, perspective views of an example of a pump wheel according to the invention;
• Figure 4, a cross-sectional view before a recess of a discharge face of the wheel;
• Figure 5, a cross-sectional view at a step of a discharge face of the wheel;
• Figure 6, a cross-sectional view along a plane comprising the axis of the wheel;
• FIG. 7, an enlargement of a recess in FIG. 5, representing a preferred geometry of this recess.

The invention provides in particular a hydraulic pump wheel having a improved entrainment of gas bubbles present in a fluid. The wheel includes a fluid inlet on one side, a radial opening, at least one fluid channel joining the fluid inlet to the radial opening, a step at the periphery of the wheel placed on the other side of the wheel and angularly offset from the opening.

Figure 1 shows a cross-sectional view of a pump 1 capable of receiving a wheel 2 according to the invention. This pump 1 is of the type multicellular: it has several successive wheels 2 to 6, driven by a shaft 13, and separated by fixed return channels 7 to 10. The pump is designed to suck a fluid from the intake 11 and discharge it to the exhaust 12.

Wheel 2 is the wheel closest to intake 11. It is therefore the wheel at level of which the fluid pressure is lowest and therefore the wheel which must potentially cause the most bubbles. The pump therefore uses at least one first wheel according to the invention. Although the embodiment of the pump described has several wheels, one can also consider in the context of the invention a pump having a single impeller as described below.

Figures 2 and 3 show perspective views of the wheel 2. The arrow represented in these figures represents the direction of rotation of the impeller 2 in the pump 1, in this case anti-clockwise by observing the wheel from the inlet 11. Figures 4 and 5 show cross-sectional views of the following wheel 2 different axial positions. Figure 4 is a section of the wheel before the recess. Figure 5 is a section of the wheel at the recess. The Figure 6 shows a section of the wheel along a plane containing the axis of the wheel. The wheel has a fluid inlet 14, a radial opening 15 and at least one fluid channel 16 joining the fluid inlet 14 to the radial opening 15. The fluid sucked through the opening 14 thus crosses the channel 16, and is expelled from the wheel by the radial opening 15. The wheel 2 has a recess 17 at the periphery of the wheel. The recess is produced on a face of the wheel opposite to the entry face. This recess is angularly offset from the radial opening. Because of this setback, the fluid flow is disturbed and the bubbles and the fluid at the periphery of the wheel. The bubbles present in the fluid are thus driven to the pump outlet or the next impeller, if applicable. Lag angular allows the recovery of the fluid leaving a radial opening 15 by a recess 17 arranged angularly following the opening. Although we could initially think that it would significantly deteriorate the hydraulic efficiency of the wheel without profit, it turns out that this hydraulic efficiency is not too strongly deteriorated and that the bubble training is however greatly improved.

In the example shown, the wheel has a fluid inlet face of the wheel formed by a first flange 18. Wheel 2 also has a second flange 19, forming the fluid discharge face of the wheel, in which the offset 17 is achieved. Several blades 20 are arranged between the flanges 18 and 19. The blades 20 delimit with the flanges 18 and 19 several channels 16.

The recess 17 preferably has a specific geometry, illustrated more specifically in Figure 7. The dotted lines represent the basic outline of a wheel 2 circular. The recess has a leading edge 21, which is angularly the closest to an opening 15 associated with the recess 17. It this is the leading edge in the direction of rotation of the wheel. This leading edge preferably forms an angle of attack, represented by α, between 80 and 100 ° with the periphery of the wheel. The periphery of the wheel is defined in the example by the circular outline of the wheel. This gives a good characteristic entrainment of bubbles by the fluid.

The recess also has a trailing edge 22, which is angularly farthest from the opening 15 associated with the recess 17. It this is the trailing edge in the direction of rotation of the wheel. This trailing edge forms preferably a leak angle, represented by β, greater than 10 °. We can thus provide training and therefore expulsion of effective bubbles. We use even more appropriately a leak angle greater than 15 ° to ensure a better expulsion of bubbles. The leak angle is preferably less than 40 ° so maintain good hydraulic efficiency of the wheel. In order to get one again better hydraulic efficiency, the leak angle is preferably less than 25 °. The best compromise found between hydraulic efficiency and bubble evacuation was obtained in the example with a leak angle of 20 °.

The recess preferably has a thickness along the axis of rotation of the wheel greater than 40% of the thickness of the channel along the same axis. Such a thickness allows to train enough fluid to evacuate bubbles. We preferably also uses a thickness along the axis of rotation of the wheel greater than 60% of the thickness of the channel along this same axis. Such a thickness helps maintain good hydraulic efficiency. The best compromise found between the hydraulic efficiency and the evacuation of bubbles was obtained with a thickness along the wheel axis equal to 50% of the thickness of the channel along the same axis.

The recess preferably has a thickness along a radius between 9 and 14% of the diameter of the wheel. The greater the thickness, the better is operation, to the detriment of hydraulic efficiency.

The recess preferably has a corresponding angular length at between 80 and 120% of the angular length of the fluid passage.

A specific geometry of a blade 20 is preferably such that it does not not transform bubbles present at the fluid inlet into bubbles of smaller dimensions at the radial opening. We use a blade between two adjacent channels with a radius of about curvature between 2 and 6mm. The bubbles thus present at the level of the radial opening as high a dimension as possible, so that their evacuation is facilitated.

It is also preferable to use a channel whose divergence is small. Thus, preferably a channel 16 is used whose divergence between the fluid inlet and the fluid outlet is between 7 and 15 °. We express the divergence by the difference between the angular length at the entrance and at the radial opening. This maintains good fluid guidance in the channel. It results that the detachments are limited. Recirculations, causing braking bubbles to be evacuated are thus avoided. Preferably a divergence between the entry and the radial opening between 8 and 9 ° to limit even better the detachments.

The wheel 2 is therefore particularly suitable for being mounted in a great suction height, that is to say greater than 4 meters. This wheel is by elsewhere particularly suitable for being mounted in a low flow pump, that is to say with a flow rate between 50 and 400 l / h.

The general problem of the operation of a pump with low flow and large suction head is different from that of pump operation during priming or pump performance. Wheel 2 improves the operation of a pump with a low flow rate and a large suction head, i.e. in aerated water. For example, wheel 2 can improve the evacuation of bubbles, for example example of air bubbles, in operation at low flow and this, outside the priming period.

A pump having several wheels as described above is a pump multicellular. It can have several wheels with return channels and broadcasters. For example, the pump may if necessary have a fixed diffuser sandwiched between two wheels. This diffuser can be smooth or have fins of in a manner known per se.

Of course, the present invention is not limited to the examples and methods of realization described and represented, but it is susceptible of numerous variants accessible to those skilled in the art.

Claims (12)

Impeller (2) of hydraulic pump (1) comprising: a fluid inlet (14) on one side; a radial opening (15); at least one fluid channel (16) joining the fluid inlet to the radial opening; a recess (17) at the periphery of the wheel, on the other face of the wheel, angularly offset relative to the opening. The wheel of claim 1, characterized in that the angle of flight, between the recess and the periphery of the wheel in the direction of rotation of the wheel, is between 10 and 40 ° and preferably between 15 and 25 ° . The wheel of claim 1 or 2, characterized in that the angle of attack, between the recess and the periphery of the wheel in the direction of rotation of the wheel, is between 80 and 100 °. The wheel of claim 1, 2 or 3, characterized in that the recess has, along the axis of rotation of the wheel, a thickness between 40 and 60% of the thickness of the channel. The wheel of one of the preceding claims, characterized in that the offset has a depth along a radius between 9 and 14% of the diameter of the wheel. The wheel of one of the preceding claims, characterized in that the recess has an angular length corresponding to between 80 and 120% of the angular length of the fluid passage. The wheel of one of the preceding claims, characterized in that the blade defined between two adjacent channels has, in the vicinity of the fluid inlet, a radius of curvature between 2 and 6 mm. The wheel of claim 7, characterized in that the wheel has: a first flange on which the entry is made; a second flange on which the recess is provided; at least one blade and the first and second flanges delimiting one of said channels. The wheel of one of the preceding claims, characterized in that the channel has an angle of divergence between 7 and 15 °, preferably between 8 and 9 °. A pump (1) having at least one impeller (2) according to one of the claims 1 to 9. The pump of claim 10, characterized in that it has a suction height greater than 4 meters. The pump of claim 10 or 11, characterized in that it has a flow rate between 50 and 400 l / h

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