EP1567773A1

EP1567773A1 - Centrifugal pump

Info

Publication number: EP1567773A1
Application number: EP03811565A
Authority: EP
Inventors: Anders Larsson
Original assignee: Volvo Lastvagnar AB
Current assignee: Volvo Truck Corp
Priority date: 2002-11-19
Filing date: 2003-11-07
Publication date: 2005-08-31
Also published as: SE0203433D0; WO2004046558A1; SE524642C2; BR0316422A; JP2006506578A; CN1714246A; SE0203433L; AU2003276796A1

Abstract

The invention relates to a centrifugal pump with an impeller (10) which is rotatable in a direction of rotation (14) in a pump housing. This impeller comprises an essentially circular-disk-shaped carrier (11) with a number of blades (13) arranged at an angle out from the disk plane. At least one of the blades (13) of the impeller extends with a first curved portion (15) which is concave in said direction of rotation (14) and a second curved portion (16) which is convex in said direction of rotation. The first curved portion extends from the inner radial edge (17) to the second curved portion. The second curved portion extends from the first curved portion in the direction of the outer radial edge (18).

Description

TITLE

Centrifugal pump

TECHNICAL FIELD

The present invention relates to a centrifugal pump with an impeller which is rotatable in a direction of rotation in a pump housing and comprises an essentially circular-disk-shaped carrier with a number of blades which are arranged at an angle out from the disk plane and extend in an essentially curved shape between an inner radial edge and an outer radial edge.

BACKGROUND

Centrifugal pumps have many areas of application, for example for pumping or pressurizing various media in a stationary manner, or for pumping coolant between heat sources and cooling devices in cooling systems in engine-driven land vehicles and craft. Within the area of application of heavy-duty vehicles, for example trucks, manufacturers can usually offer customers a model range which comprises a number of different engine sizes where each engine type comes in various power classes which can be adapted to requirements via equipment variants and where the selection of variant has a direct effect on the flow conditions of the cooling system. Examples of such equipment which is adapted to requirements are engine and gearbox oil coolers, charge-air coolers, coolers for EGR gas and coolers for retarders .

Centrifugal pumps are normally designed so that they are optimized for a given speed and for a given flow. If the pump operates outside its specifications, cavitation may occur. Alternatively, unnecessary power losses may occur. An assortment of different water pumps is therefore required in order to cover the requirements. It is moreover possible to adapt the ratio between driving shaft and pump, for example by gear ratio variation in a gear transmission. It is desirable for it to be possible for manufacturers of heavy-duty vehicles to use the same standard component, for example a water pump, for more variants than is currently possible. Moreover, it would be easier to modify a used vehicle, for example for adaptation to new environmental requirements or use conditions, if this adaptation did not involve exchange of the coolant pump.

SUMMARY OF THE INVENTION

One object of the invention is therefore to produce a centrifugal pump which is able to stand up to operating within a wide speed range, a wide flow range and with maintained high efficiency in such operating conditions .

To this end, the centrifugal pump according to the invention is characterized in that at least one of the blades of the impeller extends with a first curved portion which is concave in said direction of rotation and a second curved portion which is convex in said direction of rotation, in that the first curved portion extends from the inner radial edge to the second curved portion, and in that the second curved portion extends from the first curved portion in the direction of the outer radial edge. This design of the blade (s) of the impeller results in high efficiency at the same time within both a wide speed range and a wide flow range.

Advantageous illustrative embodiments of the invention emerge from the subclaims which follow.

BRIEF DESCRIPTION OF FIGURES

The invention will be described in greater detail below with reference to illustrative embodiments which are shown in the accompanying drawings, in which

FIG. 1 is a plan view of an impeller used in the centrifugal pump according to the invention; FIG. 2 is a section along the line II-II in Fig. 1, and FIG. 3 illustrates in graph form the relationship between efficiency and flow at different speeds for a pump installation with a centrifugal pump according to the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The impeller 10 shown in Fig. 1 comprises a circular disk-shaped carrier 11 with a central hub 12 and blades 13 arranged peripherally outside the hub. These project at an angle from the disk plane and extend in an essentially curved shape between an inner radial edge and an outer one. The impeller 10 is intended to be used in a pump housing (not shown) mounted with its hub 12 on a short driving shaft. In this connection, the inlet of the pump housing is directed essentially at right angles to the disk plane straight toward the impeller hub 12. The outlet of the pump housing is directed essentially tangentially out from the outer radial edge of the impeller, parallel to the disk plane . The impeller 10 is arranged to rotate in the direction indicated by the arrow 14 in Fig. 1. The blades 13 extend with a first curved portion 15 which is concave in said direction of rotation and a second curved portion 16 which is convex in the direction of rotation. The length of the first curved portion is approximately a third of the length of the second curved portion. The blades extend from an inner radius 17 to the outer edge 18 of the carrier 11. The inner radius 17 is located radially inside the inlet of the pump housing, which is illustrated by the dashed circle 19 in Fig. 1. The peripherally outermost tip part of the blades can be of tapering design. By virtue of the design of the blades 13 according to the invention, more effective feeding of liquid into the concave part of the blades takes place, which part is shaped so as to reduce the risk of cavitation. As can be seen from Fig. 2, the blades in the illustrative embodiment shown are inclined with an angle 20 of roughly 80° in relation to the disk plane of the carrier on that side of the blade which faces in the direction of rotation. The angle can be made smaller or larger than that shown. Alternatively, the blades can be of curved design in the direction of rotation. A number of variants are therefore possible; for example, the average inclination angle of the blades can be varied between roughly 45° and roughly

87°.

Furthermore, that edge of the blades opposite the carrier disk has an oblique bevel 21 with the tip directed in the direction of rotation. In the illustrative embodiment shown, the oblique bevel is at roughly 10° in relation to the disk plane of the carrier, but this angle 22 can be varied between roughly 3° and roughly 30°. It has been found that this bevel reduces the risk of cavitation at the same time as the efficiency increases .

In the illustrative embodiment described above, the impeller is arranged to rotate in the pump housing with the blades interacting with a pump housing wall which is parallel and close to the disk plane of the carrier. In an alternative illustrative embodiment (not shown) , the impeller can comprise a disk which is parallel to the disk plane of the carrier, connected to the blades and provided with a central inflow opening. In the case of an impeller which is "closed" in this way, the blades do not have to be inclined and beveled as described above.

The graph shown in Fig. 3 illustrates the relationship between efficiency and flow at four different speeds, from roughly 1500 rpm to roughly 3500 rpm. As can be seen from the graph, an efficiency of roughly 65% can be maintained with a flow Q varying between 6 1/s and 14 1/s. One and the same pump according to the invention can therefore be used in many different applications with varying flow/pressure drop, and, as the pump can operate with high efficiency over a wide speed range, the gear ratio of the pump does not have to be adapted specially to the different applications.

The invention is not to be considered as being limited to the illustrative embodiments described above, but a number of further variants and modifications are conceivable within the scope of the patent claims below. For example, all the blades 13 of the impeller do not have to have exactly the same shape, but it is conceivable, for example, that every other blade could be made shorter than shown, without the effect of the invention being lost completely.

Claims

PATENT CLAIMS

1. A centrifugal pump with an impeller (10) which is rotatable in a direction of rotation (14) in a pump housing and comprises an essentially circular-disk- shaped carrier (11) with a number of blades (13) which are arranged at an angle out from the disk plane and extend in an essentially curved shape between an inner radial edge (17) and an outer radial edge (18) , characterized in that at least one of the blades (13) of the impeller extends with a first curved portion (15) which is concave in said direction of rotation (14) and a second curved portion (16) which is convex in said direction of rotation, in that the first curved portion extends from the inner radial edge (17) to the second curved portion, and in that the second curved portion extends from the first curved portion in the direction of the outer radial edge (18) .

2. The centrifugal pump as claimed in claim 1, characterized in that the first curved portion (15) is shorter than the second curved portion (16) .

3. The centrifugal pump as claimed in claim 2, characterized in that the length of the first curved portion (15) is between 1/10 and 2/5 of the total length of the blade (13) .

4. The centrifugal pump as claimed in any one of claims 1 to 3 , characterized in that the blade (13) is, along at least part of its length, inclined with an angle (20) in relation to the disk plane of the carrier which is smaller than 90° on that side of the blade which faces in the direction of rotation (14) .

5. The centrifugal pump as claimed in claim 4, characterized in that said inclination angle (20) is between roughly 45° and roughly 87°.

6. The centrifugal pump as claimed in any one of claims 1 to 5, characterized in that that edge of the blade (13) opposite the carrier (11) has an oblique bevel (21) with the tip directed in the direction of rotation (14) .

7. The centrifugal pump as claimed in claim 6, characterized in that the oblique bevel (21) has an angle (22) in relation to the disk plane of the carrier which is between roughly 3° and roughly 30°.

8. The centrifugal pump as claimed in any one of claims 1-7, characterized in that the impeller (10) is arranged to rotate in the pump housing with the blades (13) interacting with a pump housing wall which is parallel and close to the disk plane of the carrier (11) .

9. The centrifugal pump as claimed in claim 1, characterized in that the impeller (10) comprises a disk which is parallel to the disk plane of the carrier (11), connected to the blades (13) and provided with a central inflow opening.