Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Radial flow devices
Patent
1991-06-20
1993-11-02
Kwon, John T.
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Radial flow devices
F01D 514
Patent
active
052579107
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a centrifugal pump impeller.
The British patent publication 575,346 A and the German patent publication 1,249,693 C describe single-piece impellers for centrifugal pumps, which operate in the range of minimum specific speeds of rotation. Such impellers have the feature that the actual vane ducts are produced by machining tools, having a straight form and along their entire length have constant circular cross section. In comparison with other known impellers with a vane duct widening like a diffusor, they have the advantage of simple manufacture but have the disadvantage of poor hydraulic efficiency.
Another design is illustrated in the Russian patent publication 620,674 A. This has a so-called open impeller, in the case of which the vane duct remains open along its entire length. It represents an unusual design to the extent that in this case the vane ducts are open drilled impeller ducts provided with a longitudinal slit. At the discharge port this design has the feature that the delivery part is made very much narrower than the vane ducts so that there are substantial pressure losses. The hydraulic efficiency is accordingly greatly impaired. Furthermore, the open impeller leads to an axial thrust towards the intake end.
SUMMARY OF THE INVENTION
One object of the invention is to provide a centrifugal pump impeller for small delivery rates and large delivery head, which furthermore provides for an increase in the pressure number and also an improvement in efficiency.
Owing to the design in accordance with the invention there is the substantial advantage over conventional centrifugal pump impellers with closed cover plates of an increase in the pressure coefficients specific to the impeller. As a consequence of the vane ducts being left open at the impeller delivery part, there is an exchange of momentum between the liquid in the duct and the liquid in the impeller side space. This in turn leads to a increase in energy, the consequence of this being an increase in the delivery head and an increase of the pressure coefficient. In contradistinction to side duct pumps there is in this case a substantial improvement in efficiency, since the forms of loss typical for side duct pumps are no longer able to occur.
According to one embodiment of the invention, there is an oblique intersection of the respective vane ducts. This renders possible different slopes of the impeller cover plate and/or the vane ducts. This in turn leads to as gradual opening of the vane ducts, owing to which there is an advantageous effect on the liquid flowing within the vane ducts. In this connection it is possible to adopt the feature with which the distance between the impeller cover and the opposite housing wall is at the most equal to the difference between the vane duct depth as measured at the impeller outlet in the axial direction and a vane duct depth as measured at the outward projection of the vane duct wall at the external diameter of the impeller. In accordance with another embodiment of the invention, the configuration of the vane duct openings, renders possible a smooth, controlled effect on the flow within the vane ducts. The designs in accordance with the invention are responsible for comparatively stable characteristics accompanied by equally satisfactory intake properties. There is also the further advantage that owing to the design of the impeller it is possible to do without the conventionally utilized projecting suction opening in centrifugal pumps and the choke gaps provided at this position. Dependent on the method of production of the vane ducts, be it by machining or by a suitable casting process, it is possible for such impellers to be utilized in a delivery rate range of up to 15 m.sup.3 /h (with n equal to 2900 rpm).
According to an additional embodiment of the invention, the vane ducts widen from their inlet ends to the outer diameter of the impeller continuously. This feature means that there is a gentle start of exchange of momentum which slowly increa
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patent: 1986836 (1935-01-01), Macneille
patent: 1988875 (1935-01-01), Saborio
patent: 2074650 (1937-03-01), Holdaway
patent: 2956503 (1960-10-01), Neidl
patent: 3244109 (1966-04-01), Barske
Hergt Peter
Nicklas Alexander
Scianna Salvatore
Kontler Peter K.
KSB Aktiengesellschaft
Kwon John T.
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