Pipes and tubular conduits – With flow regulators and/or baffles – Restrictors
Patent
1992-03-06
1994-08-30
Bryant, III, James E.
Pipes and tubular conduits
With flow regulators and/or baffles
Restrictors
138 40, F15D 0102
Patent
active
053418484
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to flow conditioners.
The International Standard on the Measurement of Fluid Flow by Means of Orifice Plates (ISO 5167) states that acceptable flow conditions for metering purposes will be attained when at each point across a pipe cross-section the ratio of local axial velocity to maximum axial velocity at the cross-section agrees to within .+-.5% with that which would be attained in swirl-free flow at the same radial position at a cross-section located towards the end of a long length of straight pipe, that is a pipe the length of which exceeds 100 pipe diameters. Swirl free conditions are considered to exist when the swirl angle over the pipe cross-section is less than 2.degree..
Flow non-uniformities, affecting both mean flow, turbulence structure and swirl angle, make it extremely difficult to guarantee this standard of flow quality. Non-uniformities are introduced by bends, valves and other pipe fittings. Straight lengths of pipe of well over 100 pipe diameters in length would be necessary upstream of the metering point to achieve satisfactory swirl values and there is experimental evidence to suggest that even for mean flow levels such a length would not be sufficient.
Clearly to provide such a settling length, even if practical given the constraints of the pipe layout, requires a large capital outlay for pipework. Particularly for large diameter pipes this may outweigh the commercial returns to be gained from the metering project to be undertaken, even possibly making it non-viable. To reduce the settling length necessary to achieve an adequately uniform flow, it is known to introduce a flow conditioning device which is designed to produce the necessary flow conditions within a relatively short length of pipe. Three types of flow conditioner are generally considered, that is a tube bundle flow straightener, a Sprenkle flow straightener, and a Zanker flow straightener. These devices details of which can be obtained from the above-mentioned ISO Standard, partially block the pipe into which they are introduced, resulting in a significant loss in pressure, .DELTA. p, usually represented in terms of a loss coefficient, K=.DELTA.p/(1/2pu.sup.2).sub.1. Typical K values for the three conditioners specified above are 5, 15, and 5, respectively.
Even with the inclusion of such a flow conditioner it is recommended that 22 pipe diameters should be allowed downstream of the conditioner before the meter and that at least 20 straight pipe diameters between the pipe fitting producing the flow non-uniformity and the conditioner should be provided. Thus even with the above conditioning devices at least 42 pipe diameters is needed in the metering length.
A flow conditioner is described in British Patent Specification No. 1375908 which has considerable advantages over the devices previously mentioned. These advantages are: perforated plate consisting of 35 holes of the same diameter. Each hole has a diameter equal to 0.13.times. the pipe diameter. flow conditions. diameter, (that is the same as the hole size).
Despite these advantages the device described in British Patent Specification No. 1375908 is not ideal. Specifically the hole distribution is not axi-symmetric and therefore its effect on flow conditions is, at least in the early stages, sensitive to the orientation of the flow conditioner to the flow. Furthermore, although the low pressure loss coefficient is advantageous where pressure losses must be minimized, the attenuation of upstream flow non-uniformities is limited.
It is an object of the present invention to provide an improved flow conditioner.
According to the present invention there is provided a flow conditioner comprising an apertured circular plate intended to be placed in a conduit in an orientation substantially perpendicular to the axis of the conduit, wherein the apertures are circular and are arranged in a plurality of radially spaced circular arrays around a central aperture, the centre of central aperture and the centres of the circular arrays coincide with the
REFERENCES:
patent: 2600733 (1952-06-01), Clift
patent: 2825203 (1958-03-01), Bertin et al.
patent: 2929248 (1960-03-01), Sprenkle
patent: 3105570 (1963-10-01), Bezemes
patent: 3250469 (1963-08-01), Colston
patent: 3572391 (1971-03-01), Hirsch
patent: 3645298 (1972-02-01), Roberts et al.
patent: 3838598 (1974-10-01), Tompkins
patent: 4735224 (1988-04-01), Pluviose
Bryant III James E.
Salford University Business Services Limited
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