EP3922855A1 - Rotor for a centrifugal pump - Google Patents

Abstract

The impeller (10) for a centrifugal pump, with which liquids containing solids in particular can be conveyed, comprises a hub body (11), a plate (15) which is arranged around the hub body and has a plate surface (16) on the front, and blades (20) , 20 '), which are arranged on the plate surface. The respective blade has a leading edge (24, 24 ') which rises from a hub contact point (23, 23') on the hub body to an apex (25, 25 ') and which, when viewed from above, is opposite to the direction of rotation (D) of the The impeller is curved. The following parameters are given for the respective leading edge (24, 24 '): - a level plane N, which is perpendicular to the axis of rotation (R) of the impeller and in which the hub contact point of the leading edge lies, - a straight line L, which passes through the hub contact point and the vertex of the leading edge passes through, and an angle of inclination (a) between the level plane N and the straight line L, which is selected to be greater than 0 degrees and less than 15 degrees.

Description

The present invention relates to an impeller for a centrifugal pump.

Impellers of this type are used in centrifugal pumps in order to be able to convey liquids containing solids in particular. The aim is to provide the largest possible cross-sections between the blade surfaces so that large solid bodies can also pass through.

However, the flow conditions can also be such that the solid material, e.g. if it is in a flexible, flat form, does not get over the leading edge of a blade, but rather sticks to the leading edge and is only whirled around by the impeller. Such material accumulates in front of the impeller until the pump is finally completely clogged.

It is an object of the invention to provide an impeller which counteracts clogging in a centrifugal pump.

An impeller that solves this problem is specified in claim 1. The further claims indicate preferred designs of the impeller and a centrifugal pump with an impeller.

According to claim 1, the impeller comprises blades, the leading edges of which rise from a hub contact point to an apex, are curved against the direction of rotation of the impeller when viewed from above and have an angle of inclination of less than 15 degrees. The shape of the blade facilitates the entry of particularly flexible, flat material into the impeller, so that the risk of clogging is reduced. The impeller can be designed in such a way that the blades have pronounced surfaces so that a correspondingly good pumping effect can be achieved.

In the case of the impeller, there is preferably an axis A for the respective leading edge which passes through the hub contact point and the axis of rotation of the impeller and which is perpendicular to this axis of rotation, the leading edge going away transversely to axis A, so that the tangent (T ) at the leading edge has an angle (ε) to the axis A, which is in the range of 45 degrees to 90 Degrees, preferably in the range 60 degrees to 90 degrees, particularly preferably in the range 70 degrees to 90 degrees.

A centrifugal pump is preferably provided with an impeller and with a wall which has grooves on the inside. When viewed from above, these can be straight or curved. The grooves also facilitate the passage of flexible, flat material, so that this is carried away and the centrifugal pump is thereby self-cleaning. It is not necessary to provide a cutting device which shreds the material.

• Fig. 1 ein Ausführungsbeispiel eines Laufrads in einer perspektivischen Ansicht;
• Fig. 2 das Laufrad gemäss Fig. 1 in einer ersten Seitenansicht;
• Fig. 3 das Laufrad gemäss Fig. 1 in einer zweiten Seitenansicht;
• Fig. 4 das Laufrad gemäss Fig. 1 in einer Draufsicht;
• Fig. 5 das Laufrad gemäss Fig. 1 geschnitten in der Ebene V-V gemäss Fig. 6;
• Fig. 6 dieselbe Draufsicht wie in Fig. 4;
• Fig. 7 das Laufrad gemäss Fig. 1 in einer Unteransicht;
• Fig. 8 das Laufrad gemäss Fig. 1 zusammen mit einem Teil einer Schleisswand in einer teilweise geschnittenen Seitenansicht, wobei jedoch von den Schaufeln die Kontur zu sehen ist, welche diese beim Drehen beschreiben;
• Fig. 9 einen Teil einer Kreiselpumpe mit einem Laufrad gemäss Fig. 1 in einer geschnittenen Seitenansicht;
• Fig. 10 die Schleisswand aus der Kreiselpumpe gemäss Fig. 9 in einer Draufsicht;
• Fig. 11 die Schleisswand gemäss Fig. 10 in einer perspektivischen Ansicht;
• Fig. 12 das Pumpengehäuse der Kreiselpumpe gemäss Fig. 9; und
• Fig. 13 das Pumpengehäuse gemäss Fig. 12 in einer teilweise geschnitten Draufsicht gemäss der Linie XIII-XIII.

The invention is explained below on the basis of exemplary embodiments with reference to figures. Show it

• Fig. 1 an embodiment of an impeller in a perspective view;
• Fig. 2 the impeller according to Fig. 1 in a first side view;
• Fig. 3 the impeller according to Fig. 1 in a second side view;
• Fig. 4 the impeller according to Fig. 1 in a plan view;
• Fig. 5 the impeller according to Fig. 1 cut in level VV according to Fig. 6 ;
• Fig. 6 same plan view as in Fig. 4 ;
• Fig. 7 the impeller according to Fig. 1 in a bottom view;
• Fig. 8 the impeller according to Fig. 1 together with part of a wear wall in a partially sectioned side view, but the contour of the blades can be seen which they describe when turning;
• Fig. 9 a part of a centrifugal pump with an impeller according to Fig. 1 in a sectional side view;
• Fig. 10 the wear wall from the centrifugal pump according to Fig. 9 in a plan view;
• Fig. 11 the Schleisswand according to Fig. 10 in a perspective view;
• Fig. 12 the pump housing of the centrifugal pump according to Fig. 9 ; and
• Fig. 13 the pump housing according to Fig. 12 in a partially sectioned plan view along the line XIII-XIII.

Fig. 1 shows an impeller 10 for a centrifugal pump, for example as shown in FIG Fig. 9 is shown. The impeller 10 has a hub body 11 around which a plate 15 with two blades 20, 20 'is arranged. The hub body 11 is provided with a central bore 12 into which the drivable shaft 60 can be inserted at the rear and the end of a fastening screw 61 can be inserted at the front (cf. Fig. 9 ). The central bore 12 has a longitudinal groove 13 in which a bar on the shaft 60 can grip for the rotationally fixed connection.

The plate 15 has a plate surface 16 on the front side which slopes continuously towards the periphery of the plate 15, preferably in a convex curvature.

The two blades 20, 20 ′ are configured identically here and are arranged circumferentially offset by 180 degrees on the plate surface 16. The first blade 20 is explained in more detail below. The explanation applies in an analogous manner to the second blade 20 '.

The blade 20 extends from the hub body 11 with a radially outward curvature and has a suction-side blade surface 21 and a pressure-side blade surface 22. As well as Fig. 2 shows, the blade surfaces 21, 22 are arranged inclined to the axis of rotation R of the impeller 10.

On the inlet side of the impeller 10, the transition from the blade surface 21 to the blade surface 22 is given by a leading edge 24. This extends from a hub contact point 23 on the hub body 11 to an apex 25. The leading edge 24 adjoins the end face 26 of the blade 20, which extends from the apex 25 to the trailing edge 27.

The leading edge 24 here has a round profile (cf. in this regard in Fig. 2 the profile of the leading edge 24 'of the second blade 20' at the apex 25 '). The wall thickness of the blade 20 is reduced in the peripheral region of the plate 15 in that the blade surface 22 is beveled towards the blade surface 21. Seen in the side view, the trailing edge 27 is curved forward, ie in the direction of rotation D of the impeller 10 (cf. Fig. 2 ).

The second blade 20 'has the same structure as the first blade 20 and has the analogous elements 21'-27', which correspond to the elements 21-27 of the first blade 20.

In Fig. 2 a level plane N is indicated, which is perpendicular to the axis of rotation R and is at the level of the hub contact point 23 or 23 '. The level plane N runs in the vicinity of the end face of the hub body 11, so that it only extends slightly above the level plane N. The leading edge 24, 24 'rises from the hub contact point 23, 23' to the apex 25, 25 ', from where the end face 26, 26' drops, here below the level level N. As can be seen, the leading edge 24, 24 'is strongly from inclined away from the axis of rotation R, so that the vertex 25, 25 'is closer to the level plane N than to the axis of rotation R.

The angle of inclination α of the leading edge 23 with respect to the level plane N can be defined, for example, as follows, cf. Fig. 3-5 : A defines the axis which passes through the hub contact points 23 and 23 'and P the plane of projection which is perpendicular to the axis A and passes through the hub contact point 23. Rp defines the axis which lies in the projection plane P and runs parallel to the axis of rotation R of the impeller 10. Furthermore, the point 25p is the vertex 25 projected onto the projection plane P, in that it is rotated about the axis Rp until it comes to lie on the projection plane P. The points 25 and 25p thus have the same radial distance from the axis Rp.

Lp defines the straight line that goes through the hub contact point 23 and the vertex 25p projected onto P. (Lp thus runs in the projection plane P.) The angle of inclination α is the angle between the level plane N and the straight line Lp and is selected to be greater than 0 degrees and less than 15 degrees. Preferably the angle is in the range of 5 to 10 degrees.

The angle α can alternatively also be defined as the angle between the level plane N and the straight line L which goes through the hub contact point 23 and the vertex 25.

Analogously, the leading edge 24 'is inclined with respect to the level plane N at an angle α, which is the angle between the level plane N and the straight line that goes through the hub contact point 23' and the vertex 25 '.

In the present exemplary embodiment, the leading edge 24 lies on a surface of revolution which results when the straight line L is rotated about the axis Rp. The leading edge 24 thus lies on a cone with the tip at the hub contact point 23. Analogously, the leading edge 24 'lies on a cone with the tip at the hub contact point 23'.

Like the top view in Fig. 4 further shows, the plate 15 has a circular edge 17. The plate surface 16 is free of cutouts so that it extends all the way to the edge 17.

The end face 11a of the hub body 11 has a circular edge with a diameter D1. This corresponds to the distance D1 between the two hub contact points 23 and 23 '. D1 is selected here to be relatively small in relation to the diameter D2 of the plate 15. Typically D1 is at most 30% of D2, preferably at most 25%, and / or at least 15% of D2; e.g. D1 is in the range of 20% -25% of D2.

The leading edge 24, 24 'is curved backwards when viewed in the radial direction, ie opposite to the direction of rotation D. Seen in the top view, the vertex 25, 25 'is thus arranged offset in relation to the hub contact point 23, 23' by an angle γ in the circumferential direction of the axis of rotation R, cf. Fig. 6 . The angle y, also called looping, is typically at least 90 degrees, preferably at least 100 degrees and / or at least 110 degrees.

The angle of wrap of the entire blade 20, 20 ', ie from the hub contact point 23, 23' to the foremost end of the trailing edge 27, 27 ', when viewed from above, is at least 180 degrees, at least 200 degrees, at least 225 degrees, at least 250 degrees with increasing preference , at least 270 degrees.

Seen in the top view, the leading edge 24, 24 'does not go perpendicularly away from the hub body 11, but hugs it as tangentially as possible. T defines the tangent of the leading edge 24 to the hub contact point 23. The axis A corresponds to the normal to the end face 11a of the hub body 11 in the plan view. The angle ε between A and T is preferably selected to be greater than 60 degrees, particularly preferably greater than 70 degrees.

Analogously, the leading edge 24 'has an angle ε, which is the angle between the tangent of the leading edge 24' to the hub contact point 23 'and the axis A.

In order to reduce the resultant of the axial forces which act on the impeller 10 during operation, the impeller 10 shown here has back blades 40 on the rear of the plate 15, cf. Fig. 7 . A respective back vane 40 extends from the entry point 41 with a radial curvature to the exit point 42. The entry point 41 is arranged at a distance from the hub body 11. The exit point 42 is located here on the edge 17 of the plate 15. In the present example, four back blades 40 are provided, each of which is evenly distributed in the circumferential direction of the axis of rotation R on the back of the plate 15. The number can also be chosen differently and can be, for example, one, two, three or more.

In Fig. 8 a further illustration of the impeller 10 together with part of an annular wear wall 50 is shown. The hub body 11 and the plate 15 of the impeller 10 are shown here in section, while the contour of the blades 20, 20 ', 40 is drawn, which is the free edge of a blade 20, 20', 40 seen in the side view during a rotation draws 360 degrees. With such a rotation, the leading edges 24, 24 ', the end faces 26, 26' and the trailing edges 27, 27 'generate a profile which is defined by the lines 24r, 26r, 27r in FIG Fig. 8 is shown. Furthermore, 23r and 25r denote the point where the hub contact point 23, 23 'and the vertex 25, 25' come to lie.

The leading edge 24, 24 'is shaped here in such a way that the line 24r is straight.

The wear wall 50 is arranged in a stationary manner. A gap, which is preferably less than 2 mm, is provided between the contour line 26r and the wear wall 50.

The impeller 10 can be produced in one piece, e.g. as a cast part, e.g. from cast iron or cast steel. When viewed from above, the blades 20, 20 'have undercuts. However, the arrangement and shape of the blades 20, 20 ′ are selected such that a sand casting mold can be created which enables the model to be removed from the mold.

Fig. 9 shows the impeller 10 arranged in the pump housing 70, which is fastened to the shaft 60 by means of a screw 61. The head of the screw 61 is formed by a front plate 62 which rests against the end face of the hub body 11. The front plate 62 has a flat central region 62a which is surrounded by a rounded edge region 62b. This connects to the hub body 11.

An annular wear wall 50 is also shown, which is replaceably attached to the inlet in the pump housing 70. The wear wall 50 has a round one Inside 51, which, viewed in the direction of flow, widens in diameter. As Figures 10 and 11 show more precisely, the inside 51 is provided with grooves 52, here with three. Depending on the design, fewer or more than three grooves 52 can also be provided. A groove 52 extends from a starting point 52a, which is located adjacent to the inlet-side end of the inner side 51, with a curved, widening course to the end point 52b, which is located at the outlet-side end of the inner side 51. The curvature of a groove 52 is spiral-shaped here as seen in plan view. The widening of a groove 52 is V-shaped here.

The pump housing 70 is in the Figures 12 and 13 more clearly visible. As an inlet, it has a suction connector 71 which is connected to the pressure connector 73 (outlet) via a spiral housing 72. The volute casing 72 is dimensioned such that the cross section increases in the direction of flow.

The operation of the centrifugal pump is, for example, as follows:
The suction nozzle 71 is connected to the suction line and the pressure nozzle 73 to the pressure line. The centrifugal pump, which is not self-priming here, is filled with liquid. The shaft 11 is driven by means of a motor. The medium to be conveyed, for example a liquid containing solids, is sucked in via the suction nozzle 71 and hits the impeller 10. Due to the special design of the inlet edges 24, 24 ', in particular, material that is flat and flexible will enter the area between the Shovels 20, 20 'made easier. The medium is conveyed by the impeller 10 along the spiral housing 72 and discharged via the pressure connection 73.

The provision of one or more grooves 52 causes the centrifugal pump to clean itself. The rotation of the impeller 10 drives flat or elongated material to the periphery, for example, so that it gets between the grooves 52 and the impeller 10 and is gradually pulled through a groove 52 until it finally gets completely between the blades 20, 20 ' and is transported away.

Impeller and centrifugal pumps as described here can be used in a variety of ways to convey different types of media, e.g. municipal and industrial wastewater, fiber-containing sludge, activated and return sludge and digested sludge as well as multi-phase mixtures with gas proportions that can also be high.

Numerous modifications are accessible to the person skilled in the art from the preceding description without departing from the scope of protection of the invention, which is defined by the claims.

In the figures, an impeller is shown in which two blades 20, 20 ′ are arranged on the plate surface 16. The number of blades can also be different, e.g. three or more. If the number is lower, e.g. two or three, then large cross-sections can be provided between the blade surfaces so that even large solid bodies can pass through.

If necessary, the impeller can be changed by turning it, e.g. if the impeller is a cast part. When turning, only the blades 20, 20 'are preferably turned off at the periphery, so that the respective trailing edge comes to lie closer to the axis of rotation, while the plate 15 is left with the original outer diameter.

In Figures 10 and 11 grooves 52 are shown, in each of which the starting point 52a and end point 52b are arranged offset from one another both radially and circumferentially. It is also conceivable to design the grooves in such a way that they only run in the radial direction. The starting point of a groove is located, for example, at the starting point 52a of the groove 52, while the end point of the groove is arranged radially offset thereto. Analogous to that seen in plan view Fig. 10 the radial groove is thus straight.

Claims (15)

An impeller (10) for a centrifugal pump, with which, in particular, liquids containing solids can be conveyed, comprising
a hub body (11),
a plate (15) which is arranged around the hub body and has a plate surface (16) on the front side, and
Blades (20, 20 ') which are arranged on the plate surface,
wherein the respective blade has a leading edge (24, 24 ') which rises from a hub contact point (23, 23') on the hub body to an apex (25, 25 ') and which, when viewed from above, is opposite to the direction of rotation (D) of the The impeller is curved, and the following values are given for the respective leading edge (24, 24 '): - a level plane N, which is perpendicular to the axis of rotation (R) of the impeller and in which the hub contact point of the leading edge lies, - A straight line L, which passes through the hub contact point and the apex of the leading edge, and - An angle of inclination (α) between the level plane N and the straight line L, which is selected to be greater than 0 degrees and less than 15 degrees. Impeller according to Claim 1, the respective leading edge (24, 24 ') having a wrap angle (γ) of at least 90 degrees, preferably of at least 100 degrees, particularly preferably at least 110 degrees, when viewed from above. Impeller according to one of the preceding claims, wherein the hub contact points (23, 23 ') of the leading edges (24, 24') lie in the same level plane N and / or the leading edges have the same angle of inclination (α) and / or the angle of inclination of the respective leading edge at least Is 5 degrees and / or the angle of inclination of the respective leading edge is at most 10 degrees. Impeller according to one of the preceding claims, wherein an axis A is given for the respective leading edge (24, 24 ') which passes through the hub contact point (23, 23') and is perpendicular to the end face (11a) of the hub body (11), wherein the leading edge (24, 24 ') goes away transversely to the axis A, so that the tangent (T) going through the hub contact point (23, 23') to the leading edge has an angle (ε) to the axis A that is in the range of 45 degrees to 90 degrees, preferably in the range 60 degrees to 90 degrees, particularly preferably in the range 70 degrees to 90 degrees. Impeller according to one of the preceding claims, wherein the end face (11a) of the hub body (11) has a maximum diameter D1 and the plate (15) has a maximum diameter D2, D1 being at most 30% of D2, preferably at most 25% of D2. Impeller according to one of the preceding claims, wherein the respective leading edge (24, 24 ') lies on a rotational surface, the axis of rotation (Rp) of which is arranged parallel to the axis of rotation (R) of the impeller (10) and through the hub contact point (23, 23') the leading edge, preferably the surface of revolution is a cone with the hub contact point (23, 23 ') as the tip. Impeller according to one of the preceding claims, wherein the respective blade (20, 20 ') adjoining the leading edge (24, 24') has a blade face (26, 26 ') which slopes down from the apex (25, 25'), preferably the face of the blade drops continuously. Impeller according to one of the preceding claims, which has at least one of the following features A1-A9 A1) the respective blade (20, 20 ') has the same shape, preferably the blades are arranged on the disc surface (16) offset by the same angle in the circumferential direction of the axis of rotation (R) of the impeller (10), A2) the respective blade (20, 20 ') is curved against the direction of rotation (D) of the impeller (10) when viewed from above, the respective blade preferably has a wrap angle of at least 180 degrees when viewed from above, particularly preferably that Wrap angle in increasing preference at least 200 degrees, at least 225 degrees, at least 250 degrees, at least 270 degrees, A3) based on the level on which the end face (11a) of the hub body (11) is located, the highest point of the respective blade (20, 20 ') is through the apex (25, 25') of the leading edge (24, 24 ') given, A4) the leading edge (20, 20 ') has a round profile, A5) the plate (15) is free of recesses, so that it has a circumferential circular edge (17), A6) the plate surface (16) drops continuously from the hub body (11) to the periphery of the plate (15), preferably in a convex curvature, A7) on the back of the plate (15) there is at least one back blade (40) which is preferably curved against the direction of rotation (D) of the impeller (10), A8) the impeller (10) is made in one piece, preferably as a cast part, A9) there are exactly two or exactly three blades (20, 20 ') arranged on the plate surface. Centrifugal pump for conveying liquids, in particular liquids containing solids, with an impeller (10) according to one of the preceding claims. Centrifugal pump according to claim 9, wherein a stationary wall (50) is provided in the inlet, which partially covers the blades (20, 20 ') of the impeller (10), preferably the wall has an inner side (51) which is opposite to the blades is arranged and which has a round contour. Centrifugal pump according to Claim 10, the inside (51) of the wall (50) having grooves (52) to form an additional free space between the blades (20, 20 ') and the wall (50). Centrifugal pump according to Claim 11, the respective groove (52) running straight or curved when viewed from above on the wall (50). Centrifugal pump according to Claim 11 or 12, the respective groove (52) widening in the direction of flow, preferably the widening is V-shaped. Centrifugal pump according to one of Claims 9-13, in which the wall is part of an exchangeable annular wear wall (50). Centrifugal pump according to one of Claims 9-14, in which the impeller (10) is arranged in a spiral housing (72).

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