Multi-stage inducer for centrifugal pumps

Abstract

An inducer assembly comprising at least two sets of rotating and non-rotating helical inducer vanes. As the fluid enters the inducer, the fluid moves up through a first set of rotating vanes, and gains rotational momentum. The fluid then enters a second set of non-rotating vanes that use the rotational momentum of the fluid to progress the fluid forward while removing the rotation and consequently decreasing the net positive suction head required. The inducer is positioned at the inlet of a cryogenic centrifugal pump. Embodiments of the cryogenic centrifugal pump use a vertical rotational axis and include a thrust equalizing mechanism device to balance hydraulic thrust.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application claims priority from provisional patent application Ser. No. 61 / 273,377, filed Aug. 3, 2009, which is hereby incorporated herein by reference in its entirety to be considered part of this specification.BRIEF DESCRIPTION OF THE INVENTION[0002]An inducer comprising at least two sets of rotating and non-rotating helical inducer vanes. As the fluid enters the inducer, the fluid moves up through a first set of rotating vanes, and gains rotational momentum. The fluid then enters a second set of non-rotating vanes that use the rotational momentum of the fluid to progress the fluid forward while removing the rotation, which consequently decreases the net positive suction head required. The inducer is positioned at the inlet of a cryogenic centrifugal pump. Embodiments of the cryogenic centrifugal pump use a vertical rotational axis and include a thrust equalizing mechanism device to balance hydraulic thrust.STATEMENTS AS TO THE ...

AI Technical Summary

Problems solved by technology

A common problem with spiral inducers used within centrifugal pumps and similar devices is that the fluid in the tank in which the centrifugal pump is installed will begin to rotate in the same direction as, and along with, the inducer blades.

When this occurs, the fluid does not move up through the inducer as efficiently.

This phenomenon can also result in a change in pressure near the inlet of the inducer and increase the amount of net positive suction head (NPSH) required to make the pump continue to work efficiently or properly.

In addition, cavitation causes noise, vibration, and erosion of material from the device.

Thus, the service life of a pump can be shortened due to cavitation.

While grooves have been used in inducer designs in the past, they have not been used to help efficiently move the fluid through the inducer.

Okamura et al. acknowledge, however, that increasing the specific speed of mixed-flow pumps has a tendency to make their performance curves unstable and to cause a big hump at low capacities, thus it is stated that it is doubtful that the illustrated technique would be effective for higher specific-speed (i.e., higher flow rate) pumps.

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