EP3662164A1 - Impeller for wastewater pump - Google Patents

Abstract

The invention relates to a mobile wheel (2) for centrifugal pumps comprising at least one blade (12). The impeller (2) is used to transport fluids containing solids. The angle a designates an angle between an entry edge (17) of the blade (12) and a peripheral direction. The angle β here designates an angle between an entry edge (17) of the blade (12) and a southern direction. The angle α, β associated is made less than 90 °, preferably less than 70 °, especially less than 50 °, depending on the prevailing speed .

Description

 description

Impeller for wastewater pump

The invention relates to an impeller for centrifugal pumps with at least one blade for conveying solids-containing media. In the case of centrifugal pumps for conveying solids-containing media, different impellers may be used, for example, channel wheels, free-flow impellers or shovels. Channel wheels are open or closed wheels with a reduced number of blades. 1, 2 or 3 blades in radial or semi-axial impellers have proven successful.

Also, free-flow pumps are used to convey solids-containing media. Such free-flow pumps are also referred to as vortex pumps, the delivery rate of which is transferred to the flow medium by a rotating disc with shovels, the so-called free-flow impeller.

In addition, semi-open impellers are also used in the wastewater sector.

In the design of the wheels, the blade shape plays a crucial role. In particular, the construction of the leading edge is of great importance. In sewage pumps, the leading edge often fills with fibers present in the fluid being pumped. The fibers are often not removed from the impeller leading edge as Because of the flow resistance on the suction and pressure side, the respective resistance forces are in equilibrium. If there is an accumulation of fibers at the entrance edges, more fibers can accumulate, so that larger occupancies can form. This behavior is particularly favored when ensuring high ball passages. The ball passage is an important parameter for characterizing the usability of sewage pumps. The ball passage is also referred to as a free, unconstrained impeller passage and describes the largest permissible diameter of the solids to ensure a clog-free passage.

The necessary for a sufficient ball passage large flow cross sections favor the structure of assignments. Especially at partial load, for example small volume flows, large flow cross sections lead to non-perfused dead water zones. The dead water zones lead to blockages. In particular, when a large ball passage is required, such assignments of the blades often occur, especially at the entry edges.

In the case of scrapers, such assignments lead to a higher power being required to operate the centrifugal pump. With multi-blades, the occupancies can also lead to an asymmetrical flow in the channels. Such asymmetric flows not only affect the required performance, but also the delivered volume flow and the delivery head.

DE 40 15 331 A1 describes an impeller with only one blade. The Einschaufelrad produced by a casting process forms between a front cover plate and a rear support plate a channel whose cross-section decreases to the inlet of the Einschaufelrades to the outlet. The suction side forms on the first 180 ° of the rotation angle a concentric with the axis of rotation arranged semicircle. The impeller is designed to prevent the occurrence of cavitation erosion.

In contrast to single-bladed wheels, impellers with multiple blades are characterized by higher efficiency. However, such wheels also special requirements for the prevention of deposits by solid Ingredients provided. For multi-bladed wheels special measures must be taken to avoid blockages.

The object of the invention is to provide an impeller for a sewage pump, are effectively avoided in the deposits. In particular, an occupancy of the leading edges with fibers should be prevented. The impeller should also ensure the highest possible efficiency in the centrifugal pump used. Furthermore, the occurrence of cavitation erosion should be avoided. This object is achieved by an impeller with the features of claim 1. Preferred variants can be found in the subclaims, the description and the drawings.

According to the invention, α is an angle between an edge of the blade and a circumferential direction, and β is an angle between an edge of the blade and a meridional direction, the associated angle α and / or β being smaller than 90 °, preferably smaller than 70 ° executed, in particular less than 50 ° executed. The angle α is an angle between an entrance edge of the blade and a circumferential direction. The angle β is an angle between an entrance edge of the blade and a meridional direction.

In order to solve the problem of deposits on the blade, the flow resistance of the fibers is considered for their transport along the leading edge of the blades. In this case, the velocity impinging on the leading edge is decomposed into a normal component and a tangential component. The normal component has an impressive effect. The tangential component is responsible for transporting the fibers. In the fluidic view, both the rotating system and the non-rotating system can be considered. Since the relative velocity can be decomposed into the components of the circumferential direction and the meridional direction, these directions can also be assigned to specific force components. In a particularly favorable embodiment of the invention, the angle β is less than or equal to 45 °. Alternatively or additionally, the angle α may be less than or equal to 45 °. The approach according to the invention results in that in the inner regions of the angle ß no or equal to perform 45 ° and in the outer regions of the angle α is less than or equal to 45 °.

If one separates the respective dominating regions by the size of the respective velocity, for the condition c _m = u, a limit radius results for axial impeller entry using the flow rate φ = ^ to R _grenz = R _a · φ. Preferably, φ is in the range of 0.3 to 0.6. The speed u is the peripheral speed. The symbol R _a denotes the outer radius of the blade.

In the recirculation area, the meridional velocities in the inner area increase strongly, so that the angle ß in this direction has an increased importance.

The impeller according to the invention makes it possible to operate the centrifugal pump in an operating range with low specific speeds and small peripheral speeds. Due to the transient character, the flow characteristic generated by the impeller according to the invention has a positive effect on the co-conveying behavior.

By the inventive approach to move the fiber transport along the leading edge of the blades by the action of the tangential components of the respective dominant speed, an improvement in the performance of the pump and a better transport without blockages can be ensured both in Einschauflern as well as at Mehrschauflern. When shoveling in, the approach in connection with a diagonal meridian section is a known solution.

After being transported along the leading edge, the blades slide over the asymmetric and smooth hub directly into the blade channel. In semi-open multi-blades, the transport takes place in the direction of the blade tip, where guide or transport grooves can take over the further processing of the fibers.

In order to be able to exploit the effect of the proportion of speed which is greater in magnitude, small angles β, preferably less than 45 ° in the region smaller than the limiting radius R _g and small angles a, preferably smaller than 45 °, should dominate in the range greater than the limiting radius R _g .

In a particularly favorable embodiment of the invention, the impeller is made semi-open. Preferably, it proves to be advantageous if the impeller is designed as a radial wheel. The impeller may have one or more blades. In a particularly advantageous variant of the invention, the impeller has two blades.

Further features and advantages of the invention will become apparent from the description of embodiments with reference to drawings and from the drawings themselves.

Showing:

1 shows an axial section through a sewage pump,

2 shows a view of the suction mouth of the wastewater pump shown in FIG. 1, FIG. 3 shows a perspective partial sectional view of the suction mouth region, FIG. 4 shows a section through the suction mouth region,

FIG. 5 is a plan view of the impeller,

FIG. 6 shows one half of a perspective representation of the impeller,

Figure 7 in a schematic side view of the inlet region of the blade the

Definition of the angle ß, FIG. 8 shows a plan view of an impeller defining the angle a.

FIG. 1 shows a sectional view through a sewage pump. The centrifugal pump shown in FIG. 1 is a submersible pump. The wastewater mixed with admixtures enters the pump through the suction port 1. Impeller 2 is rotatably connected to a shaft 3, which sets the impeller 2 in rotation. The impeller 2 is arranged in a pump housing 4, which is designed in the embodiment as a spiral housing. In the suction port 1 of the pump projects into an insert 5, which is designed in the embodiment as a wear wall or wear ring. The shaft 3 is rotated by a drive 6 in rotation, which is designed in the embodiment as an electric motor. The drive 6 comprises a rotor 7 and a stator 8. The pump housing 4 is sealed by a housing cover 9. The housing cover 9 is sealed with a mechanical seal 10 with respect to the shaft 3. The shaft 3 is supported by bearing elements 1 1.

FIG. 2 shows a view of the centrifugal pump with a view of the suction mouth 1. As shown in FIG. 2, the impeller 2 comprises two blades 12. The impeller 2 has a hub 13 in its center and is connected to the shaft 3 via a fastening means via this hub 13.

About a discharge nozzle 14, the fluid leaves the centrifugal pump.

FIG. 3 shows a perspective partial sectional view of the components which form the suction mouth 1. The insert 5 is fixed to the pump housing 4. For this purpose, a plurality of bores 15 are provided on the insert 5. About the holes 15, the insert 5 can be fastened by means of fastening means on the pump housing 4. The impeller 2 rotates counterclockwise in view of the illustration according to FIG. The impeller 2 is equipped with two blades 12 which are mounted on a support plate 16. In the embodiments, the two blades 12 and the support plate 16 are integrally formed. The blades 12 have a curved course.

The mixed with solid admixtures medium flows axially through the suction port 1 to the impeller 2 and radially outward away from the impeller 2, so that the medium leaves through the discharge port 14, the centrifugal pump.

The blades 12 have a backward curved course. All blades 12 of the impeller 2 are formed congruent to each other and have the same shape. Each blade 12 extends radially outward from the hub 13 with a curvature. In the illustration according to FIG. 3, the two blades 12 are arranged offset by 180 ° relative to one another.

FIG. 4 shows a sectional view of the suction mouth region according to the representation in FIG. 3. The insert 5 is a stationary part. In the impeller 2 to a rotating component. The blades 12 extend radially outward from the hub 13 in a backward curved course.

This again shows the representation according to FIG. 5.

Figure 6 shows one half of the impeller 2 seen in a perspective view from the side. The area of the hub 13 is shown here purely to illustrate the structural design of the impeller two cylindrical body. In the design of the impeller 2, this cylindrical shape can be omitted. At the hub 13, an entry edge 17 sets at each blade 12. The leading edge 17 of each blade 12 extends between the two points A and B. FIG. 7 shows the region of the leading edge 17 shown in black. The angle β results between the two auxiliary lines 18 and 19. According to the invention, the angle β is less than or equal to 45 °. In this case, β represents an angle between an entry edge 17 of a blade 12 and a direction in the direction of dimension. In this case, β indicates the angle in the relative system. In the absolute system, the angle is given by α. In this case, α describes an angle between an entry edge 17 of a blade 12 and a circumferential direction. Both angles α or β are inventively less than or equal to 45 °.

FIG. 8 shows a plan view of an impeller defining the angle a. The angle a is measured between the circumferential direction, that is, a circular direction and a tangent at a point on the blade leading edge in the considered radius,

ei, the angle at the inner radius R ,, a _{g is} the angle α at the limit radius R _g and a _a the angle at the outer radius R _a .

Claims

claims Impeller for centrifugal pumps with at least one blade (12) for conveying solids-containing media, with an angle α between an inlet edge (17) of the blade (12) and a circumferential direction and an angle β between an inlet edge (17) of the blade (12) and a meridional direction, characterized in that depending on the dominant speed of the associated angle (a, ß) is designed to be less than 90 °, preferably less than 70 ° is executed, in particular less than 50 ° is executed. Impeller according to claim 1, characterized in that in an inner region of the angle ß is less than or equal to 45 °. Impeller according to claim 1 or 2, characterized in that in an outer region of the angle α is less than or equal to 45 °. Impeller according to one of Claims 2 or 3, characterized in that the ranges are given by the magnitude of the respective speed, with a limit radius R _g resulting from axial flow wheel entry using a flow rate φ = ^ to R _g = R _a * φ. Impeller according to one of claims 1 to 4, characterized in that the impeller (2) has exactly one blade (12). Impeller according to one of claims 1 to 5, characterized in that the impeller (2) has more than one blade (12), preferably exactly two blades (12). Impeller according to one of claims 1 to 6, characterized in that the impeller (2) is made semi-open. Impeller according to one of claims 1 to 7, characterized in that the impeller (2) is designed as a radial wheel.