EP3633205A1 - System for driving a pump impeller - Google Patents

Abstract

The invention relates to a drive system for a pump wheel (21), characterized in that it comprises a wheel (21), a drive motor and a shaft (20), the shaft (20). is formed by a hollow cylindrical tube, of circular section and has two ends, one of the two ends has a flare in the shape of a trumpet horn, the other remaining cylindrical to be connected to the drive motor, said wheel ( 21) has a surface adapted to be installed on the flare and in an integral manner.

Description

Technical field of the invention

The present invention relates to a drive system for a pump wheel.

A pump is made up of a mobile assembly, that is to say a wheel or propeller, subject to a shaft which drives the wheel; the moving element rotates in the pump body which constitutes a space of revolution around the axis of the shaft.

The fluid passes through the small diameter of the wheel and exits through the large diameter; at its exit from the wheel, the fluid is delivered at a higher pressure than at its entry.

The wheel consists of a set of blades, regularly implanted on a frustoconical type called hub.

Two successive blades of a wheel and the portion of the hub located between these two blades, as well as the portion of the pump body located between these two blades, constitute a channel: three sides of this channel (the two blades and their hub) are mobile, and driven by the tree. The fourth side, part of the pump body, is fixed.

The wheel therefore has as many channels as there are blades.

The rotation of the moving element has the effect of raising the pressure of the fluid.

Downstream of the impeller in the direction of fluid flow, the pump includes a rectifier.

A straightener consists of a set of vanes regularly spaced in a space of revolution around the axis of the shaft; the blades are located on a hub, or 'bulb'.

Two successive blades of a rectifier and the portion of the hub located between these two blades, as well as the portion of the outer casing located between these two blades, constitute a channel. All of these are fixed.

The rectifier has as many channels as there are blades.

On leaving the rectifier, the fluid, which has been 'screwed' during its travel in the wheel, is 'unscrewed' during its travel in the rectifier, so that it is ultimately 'quiet', that is to say in a slightly disturbed state (homogeneity of the speed vector in a cross section).

Prior art

Traditionally, this set of parts, namely the pump body, the impeller, the shaft, and the rectifier are metallic and heavy.

Trees :

• soit de façon tronconique mâle, l'entrainement en rotation s'effectuant à l'aide d'une clavette placée le long d'une génératrice du cône,
• soit de façon cylindrique, l'entrainement en rotation s'effectuant à l'aide de rainures (ou cannelures) sur toute la circonférence de l'arbre,
• soit de façon cylindrique également, mais l'arbre étant usiné parfaitement lisse, l'entrainement en rotation s'effectuant par serrage du moyeu sur l'arbre.

The two ends of each shaft are machined:

• either in a frustoconical male fashion, the rotary drive being effected by means of a key placed along a generator of the cone,
• either cylindrically, the rotational drive being effected by means of grooves (or grooves) over the entire circumference of the shaft,
• either cylindrically also, but the shaft being machined perfectly smooth, the rotational drive being effected by tightening the hub on the shaft.

• soit de façon tronconique femelle, à l'opposé de l'arbre (assemblage mâle femelle) et posséder également une rainure de clavetage parfaitement appairée à celle de l'arbre,
• soit de façon cylindrique et présenter des rainures parfaitement appairées à celles de l'arbre,
• soit de façon cylindrique et parfaitement lisse, et présenter une forme appropriée du moyeu permettant de le serrer sur l'arbre.

To be able to be driven, the wheel must be machined, if necessary,

• either frustoconically female, opposite the shaft (male female assembly) and also have a keyway perfectly matched to that of the shaft,
• either cylindrically and have grooves perfectly matched to those of the shaft,
• either cylindrical and perfectly smooth, and present an appropriate shape of the hub allowing it to be tightened on the shaft.

In order to be able to be driven, the shaft carries at its opposite end a cake which allows it to be connected to the motor, the latter carrying a counter cake perfectly opposite (male female assembly) to the cake carried by the shaft.

The connection between the shaft and the oil cake is in all respects similar to the connection between the shaft and the wheel.

The two ends of each shaft very generally end in a thread allowing a nut to exert a clamping pressure between the male cones of the shaft, and the female cones of the wheel or oil cake: these nuts prevent the female cones from breaking away from the male cones.

The wheels :

The communication of energy by the pump to the fluid takes place by a distance of each fluid particle from the axis of revolution of the pump. This distance is produced by the combined effect of the hub and the vanes, limited to the outside by the shape of the cage in which the wheel turns.

The wheels have a truncated cone on which the blades are located; they comprise a second hub, cylindrical, with a diameter of the order of one to two times the diameter of the drive shaft, in which the cone, or the cylinder, is machined, intended to receive the shaft d 'training.

Traditionally, the tapered hub, the vanes located on the tapered hub and the cylindrical shaft coupling hub are made in one piece of casting.

The cylindrical hub transmits the torque from the engine to the tapered hub; the frustoconical hub transmits its rotational movements to the blades.

Conversely, the blades transmit to the tapered hub the hydrodynamic forces created on the blades, which tapered hub transmits a torque and a thrust to the cylindrical hub which transmits this torque and this thrust to the shaft.

The rectifiers:

Downstream of the wheel in the direction of flow, the frustoconical hub of the wheel is extended by the rectifier bulb, hub on which the fixed vanes of the rectifier are located.

The shapes of the outer casing and of the bulb are combined so that the fluid leaving the wheel is very gradually accelerated until it leaves the rectifier.

Traditionally, the outer casing, the blades and the bulb are made in one piece of casting.

All these parts are subject to degradation over time, by exposure to corrosion, and to wear, by exposure to fluid flow rates.

Presentation of the invention

The present invention aims to remedy these drawbacks with a completely innovative approach.

To this end, the present invention relates to a drive system for a pump wheel, remarkable in that it comprises a wheel, a drive motor and a shaft, the shaft is formed from a hollow cylindrical tube , of circular section and comprises two ends, one of the two ends comprises a flare in the shape of a trumpet horn, the other remaining cylindrical to be connected to the drive motor, said wheel comprises a surface suitable for being installed on said flaring and integrally, the wheel has a hub whose shape corresponds to the shape of the trumpet horn of the shaft.

Conventionally, the trees are very generally full, while the forces to which they are subjected, torsion and buckling, require no material in the vicinity of their axis. In the present invention, the tree is therefore very advantageously hollow.

The execution of a hollow shaft allows to remove the material where it is of no use, without loss of resistance.

A pump shaft, when it transmits torsional forces, needs no material in the immediate vicinity of its axis of rotation.

A pump shaft, when it transmits thrust forces, needs no material in the immediate vicinity of its axis of rotation to cope with buckling, instability linked to its length and the inertia of its cross section in bending.

The material used is now useful everywhere.

The invention is based on the fact that the wheel and shaft are permanently assembled (integral) and can no longer be uncoupled, which constitutes a new approach without being a drawback.

The invention is advantageously implemented according to the embodiments and the variants set out below, which are to be considered individually or according to any technically operative combination.

In one embodiment, the end of the shaft connected to the drive motor is blocked.

In one embodiment, the tree is made of composite material.

Generally speaking, composite material is here used to mean any material comprising an assembly of at least two immiscible components (but having a high penetration capacity) whose properties complement each other.

In a variant, the shaft is made of thermoplastic material.

Here, we call thermoplastic material any material comprising a certain percentage of thermoplastic material constituting a matrix, whether it is a material consisting only of thermoplastic material or for example of a composite material such as those with continuous fibers and with matrix thermoplastic.

In one embodiment, the wheel is made of composite material.

The assembly of the shaft and the wheel lead to considerable lightening; an increase in service life is also expected by the use of composites, in particular because the resistance of thermoplastic materials (composites) to cavitation is generally better than that of metallic materials.

Thanks to these provisions, the production of a hollow shaft is easy and common in composite materials.

The realization of the tree in composite materials instead of metallic materials allows a clear weight gain.

In an exemplary embodiment, for an assembly composed of a shaft and a carbon wheel, the weight is 2.9 kg while for the same dimensions for a shaft and a metal wheel, the weight is close to 30 kg. The fact of changing the material leads to a weight gain close to 10 times the metallic version.

In addition, the use of composite materials leads to a considerable increase in the stiffness of the tree.

Hollow metal shafts are already well known, but their machining cannot be envisaged physically and is only accessible financially for trees at least 100 mm in diameter.

On the contrary, the manufacture of composite material trees, by winding around a mandrel, in principle eliminates the material located near its axis, therefore the axis of rotation of the assembly.

Consequently the physical shape of the shaft on the one hand, and that of the wheel on the other hand, obtained without there being any material around the axis of rotation, leads to a reduction in the mass of material implementation, without reducing the strength of the two parts.

In one embodiment, the wheel has a hub whose shape corresponds to the shape of the trumpet horn of the shaft, the assembly of the wheel on the shaft is carried out by gluing at the contact surface of the flare of the shaft and of the trumpet horn shape of the wheel hub.

The assembly of the gluing of the wheel on the shape of the trumpet horn of the shaft allows the removal of the frustoconical hub of the wheel, that is to say a new removal of material.

Furthermore, the direct assembly of the wheel on the trumpet does not lead to any additional mass, other than a film of glue.

In one embodiment, at the level of the contact surface between the trumpet horn of the shaft and the wheel, the shaft and the wheel each have at least one through hole opposite and filled with glue.

Thus the through holes resist the shearing forces caused by the rotation.

In one embodiment, the end opposite to the flaring of the shaft is connected to a motor shaft by tightening, said tightening being adapted to drive the shaft in rotation.

In one embodiment, the shaft has through holes adapted to allow a fluid to pass.

In addition, the hollow shaft makes it possible to circulate a fluid, for cooling or lubrication purposes, since the flare, open at its rear end, is subjected to the high pressure produced by the rotation of the wheel, and the skin of the tree (external surface), opened by holes drilled in its front part is subjected to the low pressure prevailing in the fluid inlet.

In one embodiment, the wheel has blades connected to each other by an outer casing called a belt.

Overall, all the weight reductions combined lead to dividing the weight of the tree by 10, compared to current materials.

Brief description of the figures

• [Fig. 1] la figure 1 représente une vue en perspective composée d'un arbre et d'une roue, objet de la présente invention ;
• [Fig. 2] la figure 2 représente une vue de face de l'arbre objet de la présente invention ;
• [Fig. 3] la figure 3 représente une vue de perspective de l'arbre objet de la présente invention ;
• [Fig. 4] la figure 4 représente une vue de perspective selon un côté d'une roue objet de la présente invention ;
• [Fig. 5] la figure 5 représente une vue de perspective selon un autre côté de la roue de la figure précédente montrant le moyeu tronconique ;
• [Fig. 6] la figure 6 représente une vue de perspective selon un côté d'une autre roue objet de la présente invention ;
• [Fig. 7] la figure 7 représente une vue de perspective selon un autre côté de la roue de la figure précédente ;
• [Fig. 8] la figure 8 représente une vue en coupe transversale de la ceinture et le corps de la pompe en statique ;
• [Fig. 9] la figure 9 représente une vue en coupe transversale de la ceinture et le corps de la pompe en dynamique ;
• [Fig. 10] la figure 10 représente une vue en coupe l'arbre, une roue avec une ceinture et le corps de la pompe ;
• [Fig. 11] la figure 11 représente l'arbre avec des trous traversants.

Other advantages, aims and characteristics of the present invention appear from the description which follows, given for explanatory purposes and in no way limiting, with reference to the appended drawings, in which:

• [ Fig. 1 ] the figure 1 shows a perspective view composed of a shaft and a wheel, object of the present invention;
• [ Fig. 2 ] the figure 2 shows a front view of the tree object of the present invention;
• [ Fig. 3 ] the figure 3 shows a perspective view of the tree object of the present invention;
• [ Fig. 4 ] the figure 4 shows a perspective view along one side of a wheel object of the present invention;
• [ Fig. 5 ] the figure 5 shows a perspective view on another side of the wheel of the previous figure showing the frustoconical hub;
• [ Fig. 6 ] the figure 6 shows a perspective view along one side of another wheel object of the present invention;
• [ Fig. 7 ] the figure 7 shows a perspective view on another side of the wheel of the previous figure;
• [ Fig. 8 ] the figure 8 shows a cross-sectional view of the belt and the pump body in static;
• [ Fig. 9 ] the figure 9 shows a cross-sectional view of the belt and the pump body in dynamics;
• [ Fig. 10 ] the figure 10 shows a sectional view of the shaft, a wheel with a belt and the body of the pump;
• [ Fig. 11 ] the figure 11 represents the tree with through holes.

Description of the embodiments

The figure 1 shows the assembly of a wheel 21 and a shaft 20. The shaft 20 is hollow and is formed of a tube of circular cylindrical shape. The hollow shaft 20 has two ends, one of which has a flare in the shape of a trumpet horn. The wheel 21 is installed on the flare in an integral manner.

The horn of the trumpet, made of fiber of composite materials, receives by gluing the wheel 21 which is made of a composite material. According to another embodiment, the wheel 21 is made of another material. The contact surface of the wheel 21 with the flaring of the shaft 20 in the shape of a trumpet horn is perfectly compatible with the latter.

The drive of the shaft 20 is achieved by clamping its smooth end (side opposite to the flare), end connected to a drive shaft not shown.

The figure 2 shows a front view on which the hollow shape of the shaft 20 is visible in dotted lines. The shaft is hollow from one end to the other. The opening of the hollow goes from one end to the other. The thickness of the shaft skin is constant from one end to the other of the circular cylindrical part of the shaft 20. The thickness of the shaft of the part in the shape of a trumpet horn is reduced to as we approach the largest diameter of the trumpet horn.

The figure 3 shows a perspective view of the hollow shaft 20 of the figure 2 .

The figures 4 and 5 show the frustoconical hub of a wheel 21 having a belt as in the figure 1 .

A wheel 21 of the closed type carries an outer envelope called a belt, connecting the ends of the blades to each other. A wheel 21 therefore consists of as many channels closed on four sides as there are blades.

• au fil du temps, car le passage du fluide entre la haute pression (intrados 22 de l'aube) et la basse pression (extrados 23 de l'aube) d'une roue 21 de type ouvert, engendre une usure d'autant plus rapide du bord de l'aube au contact de l'enveloppe extérieure que l'interstice entre l'aube et l'enveloppe est petit, alors que dans le cas d'une roue 21 de type fermé, cet interstice n'existe pas. Cette usure des roues 21 de type ouvert entraine une chute du débit, et donc une dégradation dans le temps de la poussée de l'hydrojet,
• en matière de résistance, car les aubes des roues 21 de type ouvert sont encastrées uniquement sur le moyeu, alors que les aubes des roues 21 fermées sont encastrées sur le moyeu et sur la ceinture.

The use of closed type wheels 21, despite a slight drop in flow, offers very particular advantages:

• over time, because the passage of the fluid between the high pressure (lower surface 22 of the blade) and the low pressure (upper surface 23 of the blade) of an open type wheel 21, causes wear all the more fast edge from the blade in contact with the outer envelope that the gap between the blade and the envelope is small, while in the case of a wheel 21 of the closed type, this gap does not exist. This wear of the open type wheels 21 causes a drop in the flow rate, and therefore a degradation in time of the thrust of the hydrojet,
• in terms of strength, because the blades of the open type wheels 21 are embedded only on the hub, while the blades of the closed wheels 21 are embedded on the hub and on the belt.

The tightness of a wheel 21 of the open type between the lower surface 22 and the upper surface 23 of the blades is obtained by a perfect fit between each blade and the outer casing, throughout the rotation of the wheel 21: this gap between the lower surface 22 and upper surface 23 causes a leakage rate throughout the quasi contact. The length of the leak is proportional to the number of blades of the wheel 21 and to the length of the quasi contact between the blade and the envelope.

A wheel 21 of the closed type being completely sealed between the lower surface 22 and the upper surface 23, the seal between the high pressure at the outlet of the wheel 21 and the low pressure at the inlet of the wheel 21 is effected by the gap between the part front of the belt and the outer envelope in which the wheel turns 21. The length of leakage is equal to the circumference of the belt.

A wheel 21 of the closed type has a higher mass inertia than a wheel 21 of the open type, due to the belt, which causes a reduction in the natural frequencies of rotation and bending of the shaft 20.

One application of this system is ship propulsion by water jet, or hydrojet, which uses pumps.

The front part of the belt, which seals between the high pressure prevailing between the belt and the interior of the pump body, and the low pressure prevailing upstream of the impeller 21 has a cylindrical shape whose outside diameter is very close to the inside diameter of a cylindrical zone belonging to the pump body.

The cylindrical shape of the front part of the belt, which prevails over a width of the order of 5% to 25% of the diameter of this cylinder, is called belt tread. The cylindrical shape of the pump body, not visible, facing the tread of the belt, and which prevails over the same width, is called the tread of the pump body. Between the two treads, subjected on the rear to a high pressure, that prevailing at the outlet of the wheel 21, and on the front at a low pressure, that prevailing at the entry of the wheel 21, a fluid bearing.

The hub of the wheel 21 has a frustoconical type shape perfectly matched with the shape of the trumpet mentioned above and allows the wheel 21 to be fixed on the trumpet.

The production of the wheel 21 is made of composite materials (instead of foundry of metallic materials), leading to considerable reductions, of the order of 8 to 10 times; their execution in composite materials on molds offers a great similarity of the channels between them, by an identical geometry for each, essentially avoiding balancing operations.

The lightening of the wheel 21, even of the closed type, considerably reduces its rotational inertia.

A moving assembly must be held at its two ends in the two transverse directions and at any point in its third direction, that is to say along the axis of rotation of the crew.

• à l'extrémité avant par un roulement à billes conventionnel, placé dans l'air,
• et à l'extrémité arrière par le palier fluide qui s'établit entre les deux bandes de roulement, et qui maintient l'arrière de l'équipage mobile dans les deux directions transversales : ce palier constitue très avantageusement l'appui arrière de l'équipage mobile.

According to an exemplary embodiment, the transverse behavior is ensured at the two ends of the shaft 20: it is produced,

• at the front end by a conventional ball bearing, placed in the air,
• and at the rear end by the fluid bearing which is established between the two treads, and which maintains the rear of the moving element in the two transverse directions: this bearing very advantageously constitutes the rear support of the mobile equipment.

The maintenance in the third direction, that is to say the prohibition of any translation of the movable assembly along its own axis, in one direction as in the other, is ensured by a stop integrated in the conventional ball bearing .

• à l'extrémité avant par le palier fluide qui s'établit entre l'arbre 20 creux et le corps de la pompe,
• et à l'extrémité arrière par le palier fluide qui s'établit entre les deux bandes de roulement, et qui maintient l'arrière de l'équipage dans les deux directions transversales : ce palier constitue très avantageusement l'appui arrière de l'équipage mobile.

According to another exemplary embodiment, the transverse behavior is ensured at the two ends of the shaft 20: it is produced,

• at the front end by the fluid bearing which is established between the hollow shaft 20 and the pump body,
• and at the rear end by the fluid bearing which is established between the two treads, and which maintains the rear of the crew in the two transverse directions: this bearing very advantageously constitutes the rear support of the crew mobile.

The maintenance in the third direction, that is to say the prohibition of any translation of the movable assembly along its own axis, in one direction as in the other, is ensured by a stop positioned at one end of the 'tree 20.

• un allègement considérable de la roue 21,
• à une insensibilité à la corrosion et à une très faible sensibilité aux conséquences de la cavitation,
• à un parfait centrage et à un quasi équilibrage de la roue 21 en rotation,
• à une réduction des efforts d'entrainement en rotation de la roue 21,
• à une réduction considérable de l'inertie en rotation de la roue 21.

This achievement leads to:

• considerable lightening of the wheel 21,
• insensitivity to corrosion and very low sensitivity to the consequences of cavitation,
• perfect centering and quasi-balancing of the rotating wheel 21,
• a reduction in the rotational drive forces of the wheel 21,
• a considerable reduction in the inertia in rotation of the wheel 21.

• un équipage mobile très léger, simplifiant les opérations de montage,
• à une réduction de la longueur de l'arbre 20 portant la roue 21, réduite à la distance entre l'appui avant et le petit diamètre du tronc de cône de la trompette,
• à une élévation considérable des fréquences propres de vibration de torsion de l'arbre 20 en rotation et de flexion de l'arbre 20, obtenue tant par un accroissement de la raideur de l'arbre 20 et par la réduction de la distance entre appuis, que par la réduction de l'inertie en rotation de la roue 21,
• à une simplification des opérations d'entretien (élimination de clavette, écrous, filetage, etc....), autorisant un démontage sans effort et navire à flot.

All of the arrangements described above lead to a combination of the individual advantages obtained on the shaft 20 and on the wheel 21, and in addition to:

• a very light mobile equipment, simplifying assembly operations,
• a reduction in the length of the shaft 20 carrying the wheel 21, reduced to the distance between the front support and the small diameter of the truncated cone of the trumpet,
• at a considerable increase in the natural frequencies of vibration of torsion of the shaft 20 in rotation and of flexion of the shaft 20, obtained both by an increase in the stiffness of the shaft 20 and by the reduction in the distance between supports, that by reducing the inertia in rotation of the wheel 21,
• a simplification of maintenance operations (elimination of key, nuts, threads, etc.), allowing effortless dismantling and afloat.

The figures 6 and 7 show an open type wheel 21 having blades. In this example, there is no belt.

The figures 8 and 9 show in cross section the belt tread of the wheel 21 and the tread of the pump body 24. The figure 8 shows statically, when the wheel 21 does not turn. The figure 9 shows dynamically when wheel 21 turns. The arrow indicates the direction of rotation.

The fluid bearing is from 4 to 10 × 10 ^-4 m, or between 1 and 2/1000 ^th of the inlet diameter of the wheel 21.

The difference between the radius of the tread of the pump body and the radius of the tread of the impeller 21 is called " radial clearance ".

The figure 10 shows in section the shaft 20 terminated by its trumpet, a wheel 21 with a belt and the body of the pump 24.

In this figure, it is visible the radial clearance between the impeller 21 and the body of the pump 24.

The figure 11 shows shaft 20 and through holes.

LIST OF REFERENCE SIGNS

[Tables 1] References Designations 20 tree 21 wheel 22 lower surface 23 extrados 24 pump body

Claims (9)

Drive system for a pump wheel (21), characterized in that it comprises a wheel (21), a drive motor and a shaft (20), the shaft (20) is formed by a hollow cylindrical tube, of circular section and comprising two ends, one of the two ends comprises a flare in the shape of a trumpet horn, the other remaining cylindrical to be connected to the drive motor, said wheel (21) has a surface adapted to be installed on said flare and in an integral manner, the wheel (21) comprises a hub whose shape corresponds to the shape of the trumpet horn of the shaft (20). System according to claim 1, in which the end of the shaft (20) connected to the drive motor is blocked. The system of claim 1, wherein the shaft (20) is made of composite material. The system of claim 1, wherein the wheel (21) is made of composite material. System according to claim 1, in which the assembly of the wheel (21) on the shaft (20) is carried out by gluing at the level of the contact surface of the flare of the shaft (20) and of the shape trumpet horn of the wheel hub (21). System according to claim 5, in which at the level of the contact surface between the trumpet horn of the shaft (20) and the wheel (21), the shaft and the wheel each comprise at least one through hole in screw opposite and filled with glue. System according to claim 1, in which the opposite end is connected to a motor shaft by tightening, said tightening being adapted to drive the shaft (20) in rotation. The system of claim 2, wherein the shaft (20) has through holes adapted to allow fluid to pass. System according to claim 1, in which the wheel (21) has vanes connected to each other by an outer casing called a belt.

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