Pipes and tubular conduits – With flow regulators and/or baffles – Restrictors
Patent
1996-04-05
1998-06-09
Brinson, Patrick F.
Pipes and tubular conduits
With flow regulators and/or baffles
Restrictors
138 40, F15D 102
Patent
active
057621071
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a flow conditioner.
In order to make accurate measurements of the rate of flow of a fluid passing along a pipe, it is necessary to measure the fluid flow at a position along the pipework where that fluid flow is stable. When a fluid passes around a bend in pipework or passes a restriction in the pipework in the form of for example a valve, the fluid flow is disturbed and unpredictable flow velocity, turbulence and swirl results. If the fluid continues to flow along a straight pipe, flow conditions gradually settle until a "fully developed condition" is established. The term "fully developed condition" is used to indicate flow conditions which will not change significantly, assuming that the flow continues along a straight pipe of constant cross-section and uniform internal surface.
It is generally thought that in a straight pipe a fully developed condition can only be relied upon downstream of a bend or other disturbance in a pipe at a distance from the disturbance equal to at least one hundred times the pipe diameter. Flow velocity and turbulence can generally be relied upon to have stabilised after this distance, but swirl can require an even longer settling distance. In many circumstances it is desirable to be able to, for example, measure a flow at a distance of less than one hundred times the pipe diameter from a disturbance, and accordingly it is normal practice to include a flow conditioning device downstream of a disturbance so as to reduce the pipe distance required for the establishment of fully developed flow conditions.
Many flow conditioning devices have been proposed. A useful summary of various designs of flow conditioning devices is contained in the publication "Flow Measurement Engineering Handbook" by R. W. Miller, McCraw Hill Publishing Company. This document describes various conditioning units which are referred to as tube bundles, plate conditioners, Sprenkle conditioners, Etoile conditioners and Zanker conditioners.
Tube bundles are conditioners in the form of a simple bundle of tubes which occupy the full diameter of the main pipe. Typically there will be of the order of twenty pipes in the bundle. Such conditioners are effective in reducing or removing swirl but are not particularly effective at stabilising flow velocity or reducing turbulence. Etoile conditioners are in the form of an array of vanes which meet along the main pipe axis and extend radially to abut the inside wall of the main pipe. Such conditioners are also reasonably effective against swirl, but produce a very poor downstream flow distribution as the solid geometry at its centre gives rise to a distinct wake along the pipe axis which is extremely slow to develop. Plate conditioners are in the form of simple apertured plates of limited axial length, for example of the order of one eighth of the pipe diameter. One such plate conditioner is described in British Patent No. 1375908. In that plate conditioner, the apertures in the plate are not axi-symmetric and therefore the downstream flow conditions are sensitive to the orientation of the flow conditioner relative to the flow. This problem is overcome in the plate flow conditioner described in International Patent Specification No. WO 91/01452 which is axi-symmetric and in which the apertures are arranged such that the impedance to flow presented by the plate increases with the radius on which a given array of apertures is arranged.
The flow conditioner described in WO 91/01452 has been demonstrated to be capable of producing a downstream flow quality which is close to fully developed flow in a relatively short pipe length. For example if the plate conditioner is positioned three pipe diameters downstream of a source of disturbance, the flow quality is close to fully developed flow at a distance of nine pipe diameters downstream from the conditioner. This has enabled the plate conditioner to meet exacting International standards with respect to the time mean flow distribution. This plate conditioner is not so effective, however, in dea
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Relevant Portions of "Flow Measurement Engineering Handbook", R.W. Miller, pp. 5-41, 5-42, 5-44, 5-46, 8-6-8-9.
Brinson Patrick F.
Den Norske Stats Oljeselskap A.S.
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