US 3678963 A
An adjustable, cavitation suppressing, flow impedance for use in liquid flow systems comprising a series of thin barriers spaced in the direction of flow, each barrier having an abundance of penetrations and being associated with means for altering the effective area each barrier presents to the liquid flow.
Description (OCR text may contain errors)
United States Patent Betts et al. [451 Jul 25 .1972
 LIQUID FLOW CONTROL DEVICES  References Cited  Inventors: Colin Betts, Altrincham; Alfred Edward UNITED STATES PATENTS C lli W ,b th f d amngm Eng! 707,318 8/1902 Geyeret al. ..138/46  Assignee: United Kingdom Atomic Energy Authority, lo97'g77 5/1914 James 138/46 London, England 2,473,674 6/1949 Boehm..... ....l38/46 3,529,628 9/1970 Cummins ..l38/46  Filed: Oct. 20, 1970 Primary Examiner-Houston S. Bell Jr. 21 A LN 82416 l 1 pp 0 Atrorney-Larson, Taylor and Hinds  Foreign Application Priority Data  ABSTRACT Oct. 22, Great Britain An adjustable, cavitation pp g flow impedance for use in liquid flow systems comprising a series of thin barriers i i I I I I "138/41, 13 spaced in the direction of flow, each barrier having an t  Fieido;;;.';i;1::1.. ....'1::1""'11111i11'i38amnnnnnnnnn nnnnnnnnnnn and being nnnnnnnnnn nnn nnnnn for altering the effective area each barrier presents to the liquid flow.
3 Claims, 2 Drawing Figures .Patentad July 25,1972 3,678,963
2 Sheets-Sheet 2 LIQUID FLOW CONTROL DEVICES BACKGROUND OF THE INVENTION This invention relates to liquid flow control devices and it is concerned with the problem of cavitation, especially cavitation arising from impedances inserted in fluid flow channels in order to regulate the pressure drop in said channels.
In the context of nuclear reactors it is known to put impedances (or gags) in the coolant flow channels associated with the reactor core so that pressure drop can be regulated in the channels and thereby coolant flow can be related to heat generation in the channel s. Known forms of gags have customarily been of the orifice plate type and these give rise to cavitation, especially with large flows and large pressure drops across the gags. Cavitation in a gag can set up vibration which may cause fatigue failures in components and also set up noise to interfere with measuring instruments dependant on noise detection.
SUMMARY OF THE INVENTION According to the invention, an axial flow, cavitation sup I pressing, flow impedance comprises a hollow body member and a stack of sets of first and second plate members alternately arranged in the stack, the stack being supported inside and co-axially with the body member with the first plate members fixed to the body member and the second plate members secured to a rotatable shaft so that the second plate members can be rotated together relative to the first plate members, the
DESCRIPTION OF THE DRAWINGS One form of the invention suitable for use in a liquid flow channel will now be described with reference to the accompanying drawings in which:
FIG. I is a longitudinal sectional view of an adjustable flow impedance valve according to the invention, and
FIG. 2 is a sectional view along the line 11-11 in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings a flow impedance valve 1 is shown in which a cylindrical pressure vessel 2 houses a series of fixed annular mesh plates 3. The mesh plates 3 are equally spaced apart by their thickened rims 4 which contact the inner surface of the pressure vessel 2 and are secured to the rims 4 of adjacent plates 3 by screws 5. The complete assembly of mesh plates 3 being secured in the pressure vessel 2 by screws 6 engaging the end mesh plate 3 with a shoulder 7 formed inside the pressure vessel 2.
Each mesh plate 3 comprises a backing plate 8 having 16 equally spaced flow ports 9 machined in it. The flow ports 9 each accommodate a thin woven wire mesh window 10. The wire mesh windows 10 being secured in position by being trapped between the backing plate 8 and an insert plate 11 that is welded into the backing plate 8 and is provided with ports matching the flow ports 9 in the backing plate 8.
In front of each mesh plate 3, with respect to the direction plates 12. The ends of the shaft 13 are sup orted within the end support members 14 and 15 by thrust an journal bearings The shaft 13 is actuated by a rotatable spindle 19 being fitted with a rack 20 which engages in a pinion 21 on the end of the shaft 13, so that movement of the spindle 19 rotates the shaft 13 at a uniform velocity ratio. The spindle 19 extends into a sealed housing 23 in the pressure vessel 2. The sealed housing 20 prevents leakage of any liquid along the spindle 19.
In operation, rotation of the spindle 19 allows the masking plates 12 to occupy in one extreme a position in which their ports are in alignment with the wire mesh windows 10 in their associated mesh plates 3 to give the maximum presented flow area through the wire mesh windows 10 and in the'other extreme a position in which the masking plates 12 almost fully mask the wire mesh windows 10 to give a minimum presented flow area. Between these extremes a variety of precise presented flow areas are attainable. Thus the shaft 13 need only rotate over an area equivalent to the masking of the wire mesh windows 10.
Adjustment of the range of impedances offered by the valve 1 may be made by varying the spacing of the mesh plates 3 or by making it non-uniform along the length of the spindle 13. In addition the mesh or weave of the wire mesh windows 10 can be altered and the effective area and shape of the windows 10 and the ports in the masking plates 12 can also be varied. The number of mesh plates 3 and associated masking plates 12 may also be altered.
The flow impedance valve 1 described above is suitable for use in liquid metal flows and in this context is of value to provide gags in the fuel channels associated with the core of a nuclear reactor operating in the fast neutron region and cooled by liquid sodium.
1. An axial flow, cavitation suppressing, flow impedance comprising a hollow body member and a stack of sets of first and second plate members alternately arranged in the stack, the stack being supported inside and co-axially with the body member with the first plate members fixed to the body member and the second plate members secured to a rotatable shaft so that the second plate members can be rotated together relative to the first plate members, the plates of one of the sets of plate members having apertures covered by abundantly perforated material for liquid flow devoid of cavitation creation, through the apertures, and the plates of the other set of plate members being in the form of masking shutters for the plate members having the apertures covered by perforated material.
2. A flow impedance as claimed in claim 1 wherein said perforated material is wire mesh.
3. A flow impedance as claimed in claim 2 wherein said masking shutters each contain apertures that are complimentary to the apertures of said one set of plate members.
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