Throttling ball valve

A throttling ball valve with an array of closed spaced horizontal plates secured across the flow passage through the ball. The leading edges of the plates are streamlined so that the flow stream will be divided into a plurality of laminar flow streams, each with a boundary layer across a surface of the plate. Energy is absorbed in the boundary layer phenomenon. The array of horizontal plates is preferably contained in a cylindrical sleeve which is inserted and secured into the cylindrical flow passageway through the valve ball.

BACKGROUND OF THE INVENTION 
Plug valves, including ball valves, which are rotated through ninety 
degrees between their full open and closed positions, have long been used 
for flow control purposes. If the plug is intermediate its extreme 
positions, i.e. partially open, it provides two orifices in series, which 
are connected by a fixed volume. This throttles gas flow through the valve 
and is particularly effective where a low pressure differential exists 
across the valve element. There are, however, many services wherein the 
valve is required to absorb large amounts of energy and to effect 
substantial pressure drops. This could occur, for example, in the case of 
pipeline gas flow to a storage tank or to atmosphere or in a variety of 
flow control requirements involving high rangeability. 
Conventional ball and plug valves create very high fluid velocities when 
throttling under high differential conditions, and these high velocities 
may result in turbulence, cavitation and noise at excessive and damaging 
levels. 
OBJECTS OF THE INVENTION 
It is an object of this invention to provide a throttling valve with means 
for effectively limiting velocity. 
It is a further object of this invention to provide means for enabling the 
use of a conventional plug valve to throttle gas flow through a 
substantial pressure differential while limiting velocities therethrough 
so as not to exceed a safe level. 
It is a further object of this invention to provide a conventional plug 
valve to be used as an effective control valve under high differential 
pressure and high flow conditions. 
It is a further object of this invention to adapt a conventional ball valve 
to alter its performance curve radically so as to provide significantly 
closer control over flow rate. 
Other objects and advantages of this invention will become apparent from 
the description to follow, particularly when read in conjunction with the 
accompanying drawings. 
SUMMARY OF THE INVENTION 
In carrying out this invention, a series of generally parallel plates are 
disposed across the through-passage of a conventional plug or ball valve. 
The plates are closely spaced and their forward edges are streamlined to 
function as air foils wherein boundary layers are created across the 
surfaces thereof. These boundary layers of relatively stationary gas 
further confines the effective flow space between the plates and produces 
a frictional drag on gas flow between them. Because of the multiplicity of 
narrow flow channels, each with fully developed boundary layers, the valve 
creates an high impedence. Much of the pressure head across the valve is 
converted to frictional energy losses, rather than high velocity. 
Consequently, the valve generates little noise, is free from damaging 
cavitation and exhibits a flow characteristic more suitable to stable 
control. At the same time, many of the advantages of the ball type valve 
are retained. The air foils are conveniently disposed and welded across a 
sleeve so that they may be installed as a unit in the flow passageway of 
the ball valve.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The Embodiment of FIGS. 1 to 3 
Referring now to FIG. 1 with greater particularity, the ball valve 10 of 
this invention includes a valve body which may comprise an annular body 
band 12 to the ends of which end closures 14 are secured, as by means of 
bolts 16. Integral with the end closures are hubs 18 and suitable means, 
such as mounting flanges 20, for securing the valve into a pipeline (not 
shown). 
Top and bottom bearing blocks 22 and 24 are positioned as by means of pins 
26 and 28 and clamped between the end closures 14. The bearing blocks 
rotatably receive a rotatable plug, such as the sphere 30 shown, same 
being rotatable between the fully closed position shown in FIG. 1 and a 
fully open position ninety degrees therefrom, as by means of a stem 32, 
rotation of the ball 30 being facilitated by thrust and rotary bearings 34 
and 36. 
As a special feature of this invention, a cylindrical sleeve insert 38 is 
secured in the conventional, cylindrical through-passageway 40 of the 
valve ball 30. The cylindrical insert may be secured by any suitable 
means, such as a weld 41 (FIG. 3). Welded or otherwise secured within the 
sleeve 38 is a series of closely spaced plates 42 with confined flow 
passages 44 between them. The provision of a sleeve 38 to contain the air 
foil plates, rather than installing the plates separately, greatly 
facilitates handling during manufacturing, particularly in the larger ball 
valve sizes. 
Referring now to FIG. 2, the plates 42 divide a gas stream impinging upon 
them, and their leading edges 46 are streamlined so that the gas flows 
smoothly over the top and bottom surfaces 42a and 42b. With the air foil 
configuration 46 the gas flowing over them generates a boundary layer 
illustrated by the velocity V arrows in FIG. 2 wherein there is a boundary 
layer, i.e. a sheet of zero velocity, along the surfaces 42a and 42b. Also 
as illustrated, the laminar flow over the air foils 46, 42 extends to some 
thickness on both surfaces 42a and 42b, leaving an extremely restricted 
flow path 44a between the laminar flow zones 48. Thus, the fully developed 
fluid boundary layers V create high impedence so that much of the pressure 
head across the restricted flow paths 44a is converted to frictional 
energy losses, rather than high velocity. 
Referring now to FIG. 3 specifically, the cylindrical insert or sleeve 38 
may extend only partially through the flow passageway 40, or it may extend 
completely through the passageway. In some cases, two inserts 38 and 50 
may be employed, with the air foil plates 52 on the downstream insert 50 
staggered with respect to those on the upstream 38, whereby there is a 
further division of flow streams creating another energy-absorbing change 
in flow direction, as well as subsequent further energy losses resulting 
from frictional drag over the second set of air foil plates 52. 
As shown in FIG. 4, the provision of air foil plates radically alters the 
performance curve of a ball valve. In the conventional valve there is an 
initial sharp rise in flow rate C.sub.V as the valve is first opened, as 
shown by curve A, and this increase with valve angle continues at a steep 
rate until the valve is near full open. With the boundary layer influence 
of this invention, the flow rate increases at a low rate until the valve 
approaches full open, as shown by curve B. Even at full open there is a 
significantly reduced C.sub.V. The performance characteristics illustrated 
by curve B provide much closer control over flow rate than is possible 
with a conventional ball valve. 
The Embodiment of FIG. 5 
In this embodiment, the sleeve insert 54 has a plurality of pairs of 
parallel air foil plates 56 and 58, which are interconnected by a series 
of vertical vanes 59. As in the embodiment of FIGS. 1 to 3, the parallel 
plates may have a streamlined leading edge 62 to generate the boundary 
layer above described, and in addition, the vanes themselves 60 may have 
streamline leading edges 64 to generate boundary layers along the sides 
thereof. Hence, the vanes 60 provide additional frictional drag and also 
produce changes in flow direction in the flow passageways between each 
adjacent vane 60 for further energy absorption. 
The Embodiment of FIGS. 6 and 7 
Here, the sleeve insert 66 has a plurality of air foil plates 68, the 
leading edges 70 of which are disposed in parallel relationship. However, 
the parallel relationship is not maintained over the length of the plates 
68 so that there are both diverging 70 and converging 72 flow passageways 
between the plates 68. 
The Embodiment of FIGS. 8 and 9 
In this embodiment, the insert sleeve 74 has two sets of parallel plates 76 
and 78 which are disposed at angles to each other. For example, as shown, 
the leading plates 76 may be disposed normal to the axis of rotation of 
the ball 30, while the trailing edges 78 are disposed parallel thereto. 
Any angle between perpendicular relationship may also be chosen to provide 
desirable direction changes as well as frictional losses. 
While this invention has been described in conjunction with preferred 
embodiments thereof, it is obvious that modification and changes therein 
may be made by those skilled in the art to which it pertains, without 
departing from the spirit and scope of this invention, as defined by the 
claims appended hereto.