EP1977114B1 - Impeller - Google Patents

Abstract

The width of a blade channel continuously increases from the feeding point of a flow into an impeller to a discharge point for the flow from the impeller from a perspective of a meridian section so that the ratio between the width (b2) at the discharge point and the width (b1) at the feeding point ranges between 1.01 and 1.2.

Description

The invention relates to closed impellers for centrifugal pumps for the promotion of homogeneous fluids, in particular for use in automotive cooling systems.

In the prior art, various designs of closed wheels are described above.

For example, in the DE-PS 843 812 a design of an impeller for centrifugal pumps for the promotion of inhomogeneous substances (substances with increased gas or solids content) described above, which is characterized by a special channel and impeller design by means of the usual entemischende effect of Zentripedalfeldes centrifugal pumps is trying. This arrangement presented there is characterized in particular by at most four main blades between which mixing blades are arranged on the outer periphery.

This arrangement represents a compromise for the promotion of inhomogeneous substances DE-PS 843 812 However, presented arrangement and Schaufelradauslegung can not under any circumstances optimum delivery of liquids, for example, in terms of the efficiency of the Pressure build-up, the characteristic stability, etc. are realized. In addition, such an impeller is expensive to manufacture and also can not be made in one piece as a closed impeller.

Another design of a paddle wheel for the promotion of inhomogeneous substances is in the CH-PS 269 595 described above as the closest prior art. Here, an additional cross-sectional increase from the inlet to the outlet of the impeller channel is proposed to promote gas-containing media in all practically existing consistencies in addition to a (by an angle α) negative blade coverage to consciously in the channel by detachment to force a vacuum zone, then a promotion of Gas-containing fluids in virtually all occurring consistencies allows. However, even this arrangement does not allow optimal promotion of homogeneous liquids in particular with regard to their operating parameters such as efficiency, suction behavior, pressure build-up, head, characteristic stability, etc ..

All in the prior art for the promotion of homogeneous liquids above-described closed wheels, whether in the design as a radial blade wheels with two- or three-dimensionally curved blades or in the design as Francis, or Diagonalschaufelräder with exclusively three-dimensional, spatially curved blades have, to cause an increase in the flow velocity of the fluid in the impeller, in section through the axis of rotation and the flow channel, ie in the meridian section always over a comparison with the inlet width (b1) reduced outlet width (b2) of the blade channel.

One of these designs with simply curved blades and rectangular flow channel cross-section is, for example, in the DE-PS 195 747 presented.

In another, for example in the DE-PS 897 801 In the closed-loop design presented, the channel width initially remains the same in the region of the flow inlet and then tapers toward the outlet of the flow.

As a result of this, in the meridian section compared to the inlet width (b1) reduced outlet width (b2) of the blade channel, the production of closed impeller designs for centrifugal pumps with a significantly increased production costs compared to the relatively uncomplicated production of open impeller molds for the centrifugal pump systems connected.

The open impeller designs are usually made in one piece in the plastic injection molding process, for example, from a thermoplastic or a thermoset material.

The closed design of the wheels can be made of plastic.

But for this purpose, first an open paddle wheel with one or two-dimensional curved blades must be made which is then connected in a subsequent step with a separately manufactured cover plate to a closed impeller.

On the other hand, closed wheels with one or two-dimensional curved blades but also with the help of split slides, for example, be made in one piece as plastic injection molded parts.

Although it then eliminates a step of assembling the cover plate, but then inevitably occur significantly higher tooling costs.

In general, closed impellers with spatially curved blades have closed impellers with two-dimensionally curved blades (eg with a rectangular flow channel cross section, as in FIG DE PS 195 747 presented) at the same capacity on a larger specific diameter, a poorer suction behavior and an increased cavitation hazard.

In addition, the achievable hydraulic efficiency of closed impellers with single curved blades is a maximum of 70%.

In contrast, with closed (high-speed) impellers with spatially curved blades, a hydraulic efficiency of up to 87% can be achieved.

The main obstacle to the large-scale use of closed high-speed wheels with spatially curved blades, for example, for use as wheels in coolant pumps in engine and automotive, however, has always been their very complicated, and therefore costly production.

The inevitably relatively small and also very complicated construction of impellers with their spatially curved blades for coolant pumps had to be made very expensive due to their complicated mold release predominantly as investment casting in lost wax casting or sand casting and were therefore unsuitable for mass production.

Added to this was that the possibilities for cleaning and polishing the casting surfaces inside the impeller are very limited in these relatively small designs, so that beyond the achievable surface quality was also very limited.

As a result of these production-related inevitably remaining, relatively high surface roughness and the maximum achievable efficiency was severely impaired.

The applicant of the present invention was therefore in the DE 197 42 023 B4 proposed a novel design for closed high-speed wheels with spatially curved blades, which in addition to precisely defined blade shapes, a high blade surface quality, good concentricity properties, high reliability, minimized manufacturing and assembly costs and high efficiency is.

This in the DE 197 42 023 B4 proposed and proven in practice often proven design is characterized by a segmentation of the impeller, the division of the respective impeller always takes place in the field of blades and thereby leads to easily demoldable, for example, also inexpensive plastic to be manufactured impeller segments.

These individual impeller segments are assembled after their production in a separate step to an impeller with spatially curved blades and clamped together by means of a bottom plate and / or a clamping ring with each other.

The mostly used in series production impeller material plastic allows not only a cost-effective production of the individual components and a relatively inexpensive achievable, high surface quality, low friction, high corrosion resistance to the pumped medium as well as a high resistance to cavitation phenomena.

The cavitation arises in the operating condition of the impeller in areas of low pressure level, i. at a pressure below the vapor pressure of the fluid being conveyed, the effects of cavitation, i. the implosion of the cavitation bubbles and the wear resulting from this implosion, however, the cavitation erosion always occurs only in the areas of elevated pressure, i. mostly after the wheel up.

These arranged there, the impeller in the flow direction "downstream" components and assemblies are the pump housing and / or by integrating the pump in the engine, the timing case cover, the cylinder crankcase, the cylinder head oa ..

However, these "downstream" components are usually made of cast aluminum in modern engines.

Compared to the plastic, the aluminum casting has a much poorer resistance to cavitation erosion, so that cavitation building up in areas with low pressure levels in the impeller leads to damage due to cavitation erosion on the components and assemblies made of cast aluminum downstream of the impeller, which then become longer Continuous operation can lead to a total failure of these components / assemblies.

The invention is therefore based on the object to overcome the aforementioned disadvantages of the prior art and to develop a novel design of closed impellers for centrifugal pumps for the promotion of homogeneous fluids, especially for use in coolant pumps, which allows both closed wheels with single curved Shovels, as well as closed wheels with spatially curved blades cost to manufacture, to minimize the effects of Kavitationsverschleißes on the impeller downstream components / assemblies, while improving the hydraulic efficiency and the suction behavior of the respective impeller design significantly.

According to the invention this object is achieved by means of an impeller according to claim 1. The width of the blade channel in the meridian section increases continuously from the flow entering the impeller to the flow outlet from the impeller such that the ratio of the outlet width (b2) to the inlet width (b1) is in the range between 1.01 and 1.2.

As a result of this continuously widening exit width (b2), a significant reduction of the flow speed to the impeller outlet is effected both with closed impellers with simply curved blades, as well as with closed impellers with spatially curved blades.

This reduction of the flow velocity in the impeller obtained in accordance with the invention, taking into account the energy balance (P / ρ + w ² = constant, with P static pressure, ρ density of the flow medium, w flow velocity), inevitably causes an increase in the static pressure inside the impeller.

Due to the pressure increase desired according to the invention in the interior of the impeller, the area of the implosion of the cavitation bubbles and thus becomes also the resulting from this implosion of cavitation bubbles wear, the cavitation erosion from the impeller downstream components and assemblies laid in the impeller made of plastic.

Since the plastic of the impeller in comparison to the aluminum casting (the downstream of the impeller components) has a much higher resistance to cavitation erosion, the solution according to the invention due to the inventive effect of the displacement of the range of cavitation erosion in the impeller inevitably the effects of Kavitationsverschleißes to the Impeller downstream components / assemblies reduced to a minimum, or completely avoided.

Depending on the flow rate required for pressure build-up and the respective exit angle, the exit width (b2) can be dimensioned in a skilled manner (for example, according to the "speed triangle"). In this case, the larger exit width can be compensated by other parameters such as, for example, a smaller exit angle, the blade thickness, etc.

All required by the user performance data such as delivery and flow rate can be considered according to the usual in the art calculation methods for dimensioning the respective impeller, so that achieved by means of these novel, inventively designed wheels reliably all requested by the user performance data and by means of the invention Solution can be exceeded.

According to the invention, the ratio of the outlet width (b2) to the inlet width (b1) should always be in the range between 1.01 and 1.2, since with increasing outlet width (b2) increased recirculations occur in the impeller, which then lead to a separation of the flow.

Such recirculations are known in the prior art in various types of wheels for the promotion of inhomogeneous substances brought about, however, inevitably have the result that this worsens the suction and reduces the efficiency.

Manufacturing technology is particularly noteworthy in this context that due to the specially designed impeller geometry with a continuously increasing width of the blade channel in the meridian section from the flow entering the impeller to the flow outlet from the impeller demolding of closed wheels with simple and spatially curved blades, and thus a manufacture of the wheels according to the invention as one-piece plastic parts is possible, so that the production cost of the wheels according to the invention over the production of conventional wheels significantly simplified, with the solution according to the invention even small sizes with a high hydraulic efficiency and high suction easily and inexpensively are.

Below, the solution according to the invention will now be explained in more detail with reference to three embodiments in conjunction with twelve figures.

Figur 1:

die Draufsicht auf ein Radialschaufelrad;

Figur 2:

die Seitenansicht eines Radialschaufelrades nach Figur 1 im Schnitt bei A-A gemäß einer Bauform nach der DE 197 42 023 B4 ;

Figur 3:

die Seitenansicht des Radialschaufelrades nach Figur 1 im Schnitt bei A-A nach der erfindungsgemäßen Bauform;

Figur 4:

die Draufsicht auf ein Francisschaufelrad;

Figur 5 :

die Seitenansicht eines Francisschaufelrades nach Figur 4 im Schnitt bei B-B gemäß einer Bauform nach der DE 197 42 023 B4 ;

Figur 6:

die Seitenansicht des Francisschaufelrades nach Figur 4 im Schnitt bei B-B nach der erfindungsgemäßen Bauform;

Figur 7:

die Draufsicht auf ein Diagonalschaufelrad;

Figur 8:

die Seitenansicht eines Diagonalschaufelrades nach Figur 7 im Schnitt bei C-C gemäß einer Bauform nach der DE 197 42 023 B4 ;

Figur 9:

die Seitenansicht des Diagonalschaufelrades nach Figur 7 im Schnitt bei C-C nach der erfindungsgemäßen Bauform.

The show:

FIG. 1:

the top view of a Radialschaufelrad;

FIG. 2:

the side view of a radial impeller after FIG. 1 on average at AA according to a design after the DE 197 42 023 B4 ;

FIG. 3:

the side view of the radial impeller after FIG. 1 in section at AA according to the design according to the invention;

FIG. 4:

the top view of a Francis paddle wheel;

FIG. 5:

the side view of a Francis paddle wheel behind FIG. 4 in section at BB according to a design after the DE 197 42 023 B4 ;

FIG. 6:

the side view of the Francis paddle wheel FIG. 4 in section at BB according to the design according to the invention;

FIG. 7:

the top view of a Diagonalschaufelrad;

FIG. 8:

the side view of a Diagonalschaufelrades after FIG. 7 in section at CC according to a design after the DE 197 42 023 B4 ;

FIG. 9:

the side view of Diagonalschaufelrades after FIG. 7 in section at CC according to the inventive design.

In the FIG. 1 is designed as a radial impeller with simply curved blades 3 impeller 1 is shown in plan view.

The FIG. 2 now shows the side view of a radial impeller after FIG. 1 on average at AA according to the in the DE 197 42 023 B4 above-described "segmented construction" with the bottom 2, the blades 3, a ceiling 4 and the blade segments interconnecting clamping ring 5, and as usual in the art, a relation to the entrance width b1 significantly reduced exit width b2.

In the FIG. 3 is the side view of the radial impeller after FIG. 1 in section AA at the design according to the invention, in one piece, with the bottom 2, the blades 3 and the ceiling 4, wherein (contrary to the usual in the art sizing) the outlet width b2 according to the invention compared to the inlet width b1 is increased.

In the FIG. 4 is designed as a Francis paddle wheel with spatially curved blades 3 impeller 1 is shown in plan view.

The FIG. 5 now shows the side view of a Francis paddle wheel FIG. 4 on average at BB according to the in the DE 197 42 023 B4 above-described "segmented construction" with the bottom 2, the blades 3, a ceiling 4 and the blade segments interconnecting clamping ring 5, and as usual in the art, a relation to the entrance width b1 significantly reduced exit width b2.

In the FIG. 6 is the side view of the Francis Schaufelrades after FIG. 4 in section at BB according to the inventive design, in one piece, with the bottom 2, the blades 3 and the ceiling 4, wherein (contrary to the usual in the art sizing) the outlet width b2 according to the invention is increased compared to the inlet width b1.

In the FIG. 7 is a designed as a diagonal vane with spatially curved blades 3 impeller 1 is shown in plan view.

The FIG. 8 now shows the side view of a Diagonalschaufelrades FIG. 7 on average at CC according to the in the DE 197 42 023 B4 above-described "segmented construction" with the bottom 2, the blades 3, a ceiling 4 and the blade segments interconnecting clamping ring 5, and as usual in the art, a relation to the entrance width b1 significantly reduced exit width b2

In the FIG. 9 is the side view of the diagonal paddle wheel FIG. 7 in section at CC according to the inventive design, in one piece, with the bottom 2, the blades 3 and the ceiling 4, wherein (contrary to the usual in the art sizing) the outlet width b2 according to the invention compared to the inlet width b1 is increased.

Due to this invention enlargement outlet width b2 compared to the inlet width b1 succeeded, due to this specially designed impeller geometry with a continuously increasing width of the blade channel in meridian section from the flow entering the impeller to the flow outlet from the impeller, both closed impellers with single curved blades, as well as closed wheels with spatially curved blades to produce inexpensive as one-piece plastic parts to minimize the effects of Kavitationsverschleißes on the impeller downstream components / assemblies, while improving the hydraulic efficiency and the suction performance of the respective impeller design significantly.

REFERENCE SYMBOL

1

Wheel

2

ground

3

shovel

4

blanket

5

clamping ring

b1

entry width

b2

exit width

Claims (1)

1. An impeller in closed design for centrifugal pumps for conveying homogeneous liquids, in particular for use in cooling systems of motor vehicles, characterized in that the impeller is manufactured as a one-piece plastic part, wherein its width of the blade channel continuously increases along the meridian section from the feeding point of the flow into the impeller to the discharge point of the flow out of the impeller in such a manner that the ratio between the width (b2) at the discharge point and the width (b1) at the feeding point ranges from 1.01 to 1.2.

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