EP0752066B1 - Device for reducing noise in centrifugal pumps - Google Patents

Description

The invention relates to a centrifugal pump according to the The preamble of claim 1, as known from GB-A-112 292.

In the essay "Development of noise and vibration performance of building services pumps "from the WORLD PUMPS newspaper, June 1993, pages 23-28, the most diverse noise and Noise sources described when operating a centrifugal pump. One of the possible causes is fluid dynamic Sound developments due to flow turbulence, Flow separation and cavitation phenomena. For this counts also through the interaction between impeller and Subsequent control device noise. When the blade ends of an impeller run past the or at the leading edges of a downstream control device pressure pulsations occur in the medium. Overlay these the static pressure inside the pump housing. The The level of these pressure pulsations and their behavior are shown in the essentially from the distance between the impeller outlet and determined the entry into the control device. Small gaps cause large pressure pulsations caused by an enlargement the distance can be reduced, but below Acceptance of efficiency losses and negative Effects on the course of the characteristic. Will continue recommended to increase the number of such obstacles after an impeller change. Also a profile change of the back flank of the Impeller blades are suggested.

Other measures are from WO 91/13259 and DE-OS 24 22 364 known, with which pulsations of the flow of Centrifugal pumps with a spiral housing should be avoided. The WO 91/13259 provides an inclined position of the trailing edges the impeller blades and the use of additional Intermediate blades before. This with spatially curved Impeller blades inevitably set oblique course the impeller blade ends has a known cheaper one Pulsation behavior. This was done by tilting it chosen in which the transitions between the blade leading edge and the one impeller cover by the distance to one neighboring shovel on the opposite Impeller cover plate are arranged offset. In a way are the transition points between the blade leading edge and Cover disc parallel to the axis of rotation during the course of the Blade leading edge by the offset of a blade spacing runs diagonally between the transition points. Disadvantageous the opposite hydraulic and manufacturing limits. Because the curvature Exit angle of the impeller blades and their inclination can for hydraulic reasons only in a relatively small Angular range with respect to the axis of rotation can be changed because otherwise a desired operating point of the pump is not is achievable. Such changes can be too Loss of efficiency.

In contrast, in DE-OS 24 22 364 there is an impeller Use where the number by using a partition the blade channels and the number of blades is increased. By staggering the blades by half Blade pitch is twice as high Pulsation frequency compared to a guide device that with a normal impeller interacts. The underlying one Principle sees a reduction in the mass flow per Blade channel before, which reduces the pulsation energy becomes.

US-A-2 018 092 is a single-acting centrifugal pump known. A radial wheel rotates in a pot-shaped housing and conveys into an annulus. Extend into the annulus Sheets standing radially on the inner wall of the housing run helically to the pressure side wheel side space. The sheets are circular in shape and have the same diameter arranged. Due to the lack of coverage of these sheets there is therefore no increase in pressure behind the impeller. in the Sheets arranged on the wheel side guide the swirled Flow to an exit.

GB-A-112 292 is a measure to influence the Cavitation behavior of volute casing pumps disclosed. Compared to the usual spirals developing over 360 ° finds a spiral that only develops over 240 ° Use. 120 ° of the wheel circumference are covered. Here has the first half seen in the flow direction the impeller cover is gradually blocked Impeller outlet cross-section during the second half a complete blockage of the impeller outlet cross section causes. This blocking measure will make a noise causing pulsating pump operation.

US-A-2 362 514 teaches the use of a turbocharger Gap enlargement between impeller outlet and stator inlet. The gap has a wedge-shaped cross section. Consequently should secondary flows in the transition between running and Stator are influenced to avoid vibrations. This Measure causes loss of efficiency.

The invention is therefore based on the problem of a solution develop with the help of hydraulic noise behavior clearly without negative influence on the pump efficiency is reduced.

The solution to this problem is described in claim 1. In the guide device arranged downstream of an impeller, which the speed energy of the impeller Converts medium into a pressure energy, it can be a spiral with at least one leading edge or around one downstream stator with the leading edges of the respective Acting stator blades. Contrary to the usual Embodiments in which the leading edges parallel to The leading edges indicate the axis of rotation the guide device one with respect to the axis of rotation of the impeller sloping course. Their inclination, regardless of whether it is a spur forming a leading edge Spiral or leading edges of stator blades no adverse effects on the function of the control device. Because their task, by means of a Flow direction increasing cross-sectional enlargement Velocity energy of the medium in pressure energy converting is not due to the leading edge course influenced. The inclination of the leading edge is like this chosen that the gap between the impeller and leading edge remains largely the same size. Depending on the type of Guidance device one or more spatially curved, three-dimensional blades. Their use results in at the same time better hydraulic conditions.

For example, in the case of a stator, the wall surfaces of the Stator blades within the stator one of the Inclination of the leading edges following inclination. The vane channel formed between them therefore has - Put simply - a cross-sectional area that one Parallelogram resembles. The course of the process is crucial Leading edge. The subsequent course of the Blade surfaces of the guide device can be the usual Customs or rules of interpretation. Essential is a course that corresponds to the intended use of the Control device corresponds. In the same way, this applies to the spur of a volute casing designed as a single blade. With a guidance system, entry into the Guide device designed for optimal noise reduction be the guidance device itself for the desired one Pressure implementation and the exit of the Guide device for the most favorable inflow conditions downstream impeller. The control device itself is said to be between its bounding wall surfaces enable desired pressure ratios.

This design of the leading edges one Impeller subordinate guide can also be used explain another example. The assumption is that the arranged between two annular wall surfaces Guide vanes of a guide wheel or the leading edge or the Spur of a spiral telescopically changeable and wide are articulated to the wall surfaces over their length. The leading edges can then be passed through Twisting one wall surface against the other Create the wall surface and around its center axis. Here the course of the downstream of the leading edges changes Blade or spur surfaces in a corresponding manner. It can however also any other possible blade surface course be realized constructively, the intended Energy conversion through diffuser-like enlargement of the The leading channel cross section causes.

As an additional advantage of this type of design from The leading edges of a guide device have been found to be practical Surprisingly try their seriously improved Cavitation behavior shown. Compared to a usual one The leading edge course was evident that the same Operating conditions of the centrifugal pump, the Leading edge had no cavitation damage. In contrast, the conventional leading edge showed one Cavitation phenomena due to material removal. And as Another advantage has been found that so designed Shovels of a guide device a much lower one during operation showed dynamic blade loading. So that's it Possibility given higher guidance devices according to the invention Suspending loads or using heavy-duty centrifugal pumps equip a security benefit by putting the loads on whose leading edges are reduced.

In claims 2 to 8 further embodiments of the Invention described. A major advantage of the invention is the ability to change the radial distance between one or several leading edges of the guide device and the impeller smaller than usual. This results in hydraulic advantages. From the inclination of the leading edges any resulting larger forces can be Use axial thrust compensation.

When the trailing edges of the impeller blades run past there is no longer a linear, axially parallel encounter with the downstream leading edge (s) of the guide device. Instead, the edges meet each other point past each other. The resulting pressure pulse thus takes place over a significantly longer period of time and is on a much smaller spatial area limited. The build-up of sudden pressure pulsations thus reduced to a very decisive extent. Instead of an abruptly high dynamic load now arises a cyclical load with significantly lower Voltage level. The reason for this is a longer stay the blade leading edges in the area of the respective Leading edge of the guide device. By the invention Design promotes a blade channel of an impeller at the same time in two entry channels of a subordinate one Control device. This is also true for a spiral Guide to, since their spur-shaped leading edge then to Impeller outlet width runs diagonally and with a leading duct into the main spiral is.

In the case of a guide device according to the invention, regardless of whether it is a stator or a spiral are in Depending on the size of the impeller / guide device combinations used and the number of used Buckets a variety of possible inclinations of the Leading edge possible. The leading edge or edges can For example, be arranged so that they are of the same up to an opposite oblique position to the Impeller blade trailing edges run. So is a considerably greater freedom to influence the Noise development due to the interaction between the given blade edges passing each other. At a Arrangement of the blade edges of the impeller outlet and Guide device entrance with an inclination in the same Pay attention to an angular offset to one linear passage between the leading edge and the impeller blade to exclude. In the spiral casings, this points to the The leading edge of a spur following a wall surface fluid transition in the subsequent, unchanged Spiral room on.

When using a subordinate to the impeller Guide device according to the invention with narrow gaps between Impeller and guide device can be reduced noise pressure pulsations in the order of up to 20 dB determine. The inclined leading edges have over a length that is 0.1 to 1.2 times one Correspond to the impeller blade division at the impeller outlet. In Accordingly, the ends of the circumferential direction in the leading wall edges merging with each other staggered.

Depending on the geometry of the control device, for example when used in multi-stage pumps, it is also possible, a non-linear course for the leading edges to provide. This can also be useful when using Impellers whose blade trailing edges have a course which have a non-linear leading edge a guidance device makes sense. A arrow-shaped training, comparable to an arrow wing can have a positive or negative arrow is both at the leading edge as well as at the blade exit edge of the Impeller attachable. Allow appropriate combinations a serious one for a wide variety of applications Reduction of noise behavior. An arrow of the For example, leading edges can be used for double-flow Impeller designs make sense to avoid axial thrust forces let develop. With usual single-flow impellers can an influence due to the chosen course of an inclination be exerted on the axial thrust of an impeller. This can depend on the pressure distribution at an impeller outlet at the respective design point. Because depending on the design principles used with an impeller the resulting pressure component to the suction or pressure side Cover plate of the impeller to be moved. With the help of a according to the selected inclination of the leading edge or edges of a guide device is then also one It is possible to influence the pump characteristic. The point optimal Efficiency can then be too small or larger be moved. With the help of this inclination can as a positive side effect is the freedom of design a centrifugal pump.

Regarding noise reduction, the invention is Guide device independent of an impeller. It offers the possibility of retrofitting already installed systems, if these with a replaceable Guide device are provided or are adaptable accordingly.

Due to practical tests with a guidance device oblique leading edges was found that Changes in the gap between the impeller and Guide device the steepness of a pump characteristic influence. An increase in the gap has one Pump characteristic curve with a flatter increase. This additional positive side effect, however, has no negative Effects on noise. With very tight Columns that would otherwise be too strong in conventional control systems Pressure pulsations result in optimal Suction conditions with an extreme noise reduction.

A further embodiment provides that the distance between the cylinder planes on which the leading edges of the Guide device and the trailing edges of the blades lie, is different. This feature offers several Benefits. This means that there can be different distances on a stator between impeller outlet diameter and Guide vane leading edges are provided. You might as well a different distance between successive Guide vanes are provided, d. H. every second leading edge would then be the same distance.

On the one hand there are direct influences on the impeller and control device produced noise emissions possible and on the other hand, those acting on the guide device can Forces are better absorbed. The general Design rule, according to which the number of blades of an impeller Noise reasons with the number of blades of one A control device should be identical Centrifugal pump with a designed according to the invention Stator equipment is no longer observed.

Fig. 1

eine Leiteinrichtung als perspektivische Darstellung eines Leitrades, die

Fig. 2

einen Schnitt durch eine Kreiselpumpe mit einer Spirale als Leiteinrichtung, die

Fig. 3 - 5

verschiedene Schnitte durch die Spirale und die

Fig. 6 - 9

am Beispiel einer Anströmkante deren mögliche verschiedene Verlaufsformen.

Embodiments of the invention are shown in the drawings and are explained in more detail below. They show

Fig. 1

a guide device as a perspective view of a stator, the

Fig. 2

a section through a centrifugal pump with a spiral as a guide, the

3 - 5

different cuts through the spiral and the

6 - 9

using the example of a leading edge, its possible different course shapes.

1 is a perspective view as a guide device 1 Representation of a stator shown. For the sake of a better one The stator was shown openly. A guide wheel usually consists of two wall surfaces, between which connecting guide vanes are arranged. The one shown here Stator has a wall surface 2 with which several Stator blades 3 are firmly connected. The leading edges 4 of the In the example shown here, guide vanes 3 lie on one Cylinder surface that is concentric to the impeller axis of rotation is arranged. The follow on this cylinder surface Leading edges of the curvature of the cylinder surface and extend intersecting to the axis of rotation. Viewed in the meridian section, in this example, both the leading edges 4 and also the trailing edges 5 axially parallel. The meridian cut identifies the area that a blade at their rotation over the axis of rotation of the impeller.

In the illustration chosen here, the leading edges have an inclination or overlap which is equal to the blade pitch t of the guide device 1. The leading edge 4 extends from its one end point 6, which is located on the wall surface 2, to its other, here freely standing end point 7. The inclined position of the leading edge 4 was chosen so that the end point 7, in the direction seen on the plane of rotation axis of rotation, located above the end point 6 of an adjacent guide vane 3. The mutual offset of the end points 6, 7 of a leading edge 4 corresponds here to the simple one of a blade division. Depending on the size of the guide device as well as the number of blades and the design of the impeller used or depending on the specific speed n _{q of} the centrifugal pump, the inclination can correspond to 0.1 to 1.2 times a blade pitch t of an impeller. In the case of centrifugal pump impellers with a small nq, as are known from radial impellers, an inclined position is selected which corresponds to a maximum of one blade division at the impeller inlet. Usually, the inclination of such impellers will correspond to a smaller value in order to maintain the inlet cross-section of a correspondingly narrow guide device in terms of production technology. In the case of impellers with a larger nq, due to the larger impeller outlet width, which is usually also followed by a correspondingly wider guide device, an oblique position can be used which extends up to 1.2 times a blade pitch.

The assignment of the number of impeller blades and Division declared. If an impeller with 8 blades is used, then the impeller trailing edges would be at a circumferential angle of 45 °. An inclination of the Leading edges of a guide device with half Impeller blade division, would then, based on the Circumferential angle of 45 °, an inclination of 22.5 ° correspond. If the impeller had 9 blades, it would be Blade division on the outer circumference = 360 °: 9 = 40 °. At a Inclination corresponding to half an impeller blade division the start and end points of a leading edge would be one Guide device based on the circumferential angle of the impeller 20 ° to each other. It did multi-vane guide devices for hydraulic reasons found to be expedient if their number of blades is greater is the number of blades on the impeller.

The guide device 1 shown here is a for reasons better visibility than the so-called open idler shown. It could be installed directly and z. B. at a multi-stage pump with the open side on one Fit the stage housing wall. But it is also straightforward possible this stator as a so-called closed Training the stator. The blades would then be between two wall surfaces arranged.

Fig. 2 shows a sectional view of a housing 8 a Centrifugal pump. The guide device 1 is here as a spiral 9 educated. An impeller 10 is located within the housing 8 arranged. Whose blade leading edges 11 pass during of operation, the leading edge 12. This extends between the cutting lines H 1 - H 3 and runs obliquely to axis of rotation 13 perpendicular to the plane of the drawing The medium 10 emerging from the medium is shaped 14 partly in the pressure nozzle 15 and partly in the spiral 9 headed. For this purpose, the leading edge and the spiral about a more or less pronounced shape or Throat 16. In the exemplary embodiment, it was for reasons of better clarity shown enlarged. This Cross section change of the spiral is according to the desired Operating conditions designed. At the beginning of the leading edge 12 the formation or groove 16 develops like a Guide channel into the spiral. So that can be largely undisturbed distribution from the impeller into the pressure nozzle and with further rotation of the impeller the transition to Guide channel. This distribution of the flow in To a certain extent, the area of the leading edge enables one smooth silent transition in the spur area.

The inclination of the leading edge 12 located on the spur can reach up to a blade division of the impeller or with wide impeller outlet areas, it is also sufficient. Here too, it is essential to maintain an approximation even gap between the impeller outlet and Spiral start.

3 shows a view along the section line H 1 a look at the diagonal to the plane of the drawing Leading edge 12, which emerges from the spiral 9 medium conducts into the pressure port 15.

A line cut in the flow direction behind it H 2 is shown in Fig. 4. Leaving the impeller 10 Medium flows into the groove 16 on the one hand and further into it there the spiral 9. Another part passes along the shape 14 in the pressure port 15. Depending on the length or inclination the leading edge 12 can for the duration of the passage of a respective blade channel of an impeller 10 along the Leading edge 12, a small part of the medium from Get the impeller 10 directly into the pressure port 15. A Loss of efficiency is not to be expected and can if necessary by simple adjustments of the impeller be eliminated.

In Fig. 5 the cross section at the end of the leading edge is through the spiral 9 shown according to section H 3. From this point onwards the fluid emerging from the impeller 10 from the fillet 16 or molded into the subsequent spiral.

The course of a leading edge 4, 12 can, as in the Developments of FIGS. 6-9 using the example of each Leading edges 4, 12 is shown, also one of a straight Line have a different shape. This can be steady or inconsistent courses, sudden changes or the like his. Depending on the prevailing at an impeller outlet Pressure distribution profile can be a course of a Leading edge 4, 12 can be selected, the most favorable conditions in terms of stability, noise reduction and Offers axial thrust behavior. The ones shown in Figs. 6-9 Gradients are only exemplary and the subject of the invention is not limited to that. Here also result from the selected course no adverse effects on the Behavior of a stator channel or spiral space. Because of that Possibility for energy conversion is mainly through the whose cross-sectional relationships determined.

Claims (8)

1. Centrifugal pump in whose housing (8) at least one impeller (10) is arranged, a guide device (1) is arranged downstream of the impeller (10) for converting the flow energy of an impeller (10) into pressure energy, and flow-guiding surfaces of the guide device extending to larger diameters and having one or more leading edges (4,12) opposite an impeller outlet are provided, where a leading edge (12) or the leading edges (4) of the guide device (1) are arranged at an angle to the impeller axis (13), and where upon passing of the impeller blades a punctiform overlap is produced between the impeller blades and the respective leading edge (4, 12), characterized in that the guide device is constructed such that its flow channel or its flow channels widens or widen in the throughflow direction, starting from the leading edge (12) or the leading edges (4).
2. Centrifugal pump according to Claim 1, characterized in that the length of an obliquely extending leading edge (4, 12) is greater than the width of a guide device (1).
3. Centrifugal pump according to Claim 1 or 2, characterized in that the end points (6, 7) limiting the length of the leading edges (4, 12) are arranged offset with respect to one another by 0.1 to 1.2 times an impeller blade pitch.
4. Centrifugal pump according to one of Claims 1, 2 or 3, characterized in that an approximately constant gap is arranged between the impeller outlet and the leading edge.
5. Centrifugal pump according to one of Claims 1 to 4, characterized in that the respective leading edges (4, 12) have a nonlinear profile.
6. Centrifugal pump according to Claim 5, characterized in that the leading edge (4, 12) extends in the form of an arrow.
7. Centrifugal pump according to one of Claims 1 to 6, characterized in that the outlet edges of an impeller blade extend in the form of an arrow.
8. Centrifugal pump according to one or more of Claims 1 to 3 and 5 to 7, characterized in that the distance between the planes on which the leading edges (4, 12) of the guide device (1) and the outlet edges of the rotating blades respectively lie varies.

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