Note: Descriptions are shown in the official language in which they were submitted.
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Description
Check Valve
Technical Field
This invention relates generally to fluid check valves
and more specifically to such check valves adapted for use
in a compressor bleed flow system in a gas turbine engine.
Background Art
It is a common practice to bleed compressor discharge
air from the compressor section of a gas turbine engine
employed as a propulsion means for jet aircraft. Air is
bled from the compressor to prevent surgé of the engine
during starting and acceleration conditions, for heating
the aircraft cabin and for warming wing sections and other
surfaces of the aircraft to prevent icing thereof. Systems
for bleeding air from the compressor discharge typically
employ check valves which prevent reverse flow through the
systems which would occur, for example, when the bleed
systems from multiple engines communicate with one another
and one of the engines becomes inoperational. Without
reverse flow checking, such a condition would cause air
bled from operational engines to flow to any inoperational
engine, thereby interfering with the performance of the
auxilliary heating equipment referred to hereinabove. The
check valves employed in such bleed systems must be capable
of passing air at pressures in the neighborhood of 300 psi
at temperatures of about 800~F and must be capable of
rapidly closing under reverse flow conditions.
Prior art compressor bleed check valves have typically
been of the flapper variety. However, such flapper
valves are characterizied by a minimum of valve element
bearing area in comparison to the flow area of the valve.
Such lack of bearing area militates asainst the durability
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of the valve, causing premature wear of the valve seats
due to fluttering impact between the valve and the
seats. Examples of a prior art flapper type compressor
bleed check valve are found in U.S. Patent No. 2,925,825
to Staiger. While various other one-way or check valves
are known in the prior art, such valves often define
flowpaths therethrough which are restricted, tortuous or
otherwise contribute to undesirable pressure drop through
the valve, U.S, Patent Nos. 2,927,604 to Johnson and
2,928,417 to suckner et al are illustrative of alternate
prior art check valve arrangements. While U.S. Patent
No, 3,134,394 to Ohta illustrates a check valve having
lower pressure drop characteristics than other of the
check valves discussed hereinabove, it is believed that
the check valve of the present invention represents
significant advances in pressure drop characteristics
and rapid rever~e flow checking over the Ohta valve.
Disclosure of Invention
It is therefore an object of the present invention
to provide an improved check valve having a valve
element supported on bearings of substantial area where-
in flutter and wear through fluttering impact are
minimized.
It is another object of the present invention to
provide an improved check valve wherein the flow through
the valve is characterized by minimal restrictions and
a generally non-tortuous flowpath.
It is another object of the present invention to
provide an improved check valve wherein the pressure
drop across the valve is minimized.
It is another object of the present invention to
provide an improved check valve characterized by rapid
but controlled checking under reverse flow conditions,
In accordance with a particular embodiment of the
invention, there is provided a fluid check valve. The
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valve includes a housing, defining an oute~ portion of
a fluid channel and a seat disposed within the housing.
A valve element is positionable within the housing by
fluid flow therethrough, the valve element, by applica-
tion thereto of reverse fluid flow being held inengagement with the seat for closing the check valve
and, by application of forward fluid flow thereto,
being unseated for opening the check valve. An
apertured guide body is disposed within the casing
and defines, with the valve element under conditions
of normal fluid flow, an inner wall of the fluid
passage, The apertures accommodate reverse flow
therethrough for application of the reverse flow to
the valve element for seating the valve element and
closing the check valve. The check valve is character-
ized by the guide body being mounted within the interior
of the housing by a plurality of spaced struts. Each of
the struts is disposed between the housing and guide
body and extends in directions defined by directional
components both radially outward from and tangential to
the guide body.
In accordance with a fuxther embodiment of the
invention, there is provided a fluid check valve The
valve includes a housing, defining an outer portion of
~25 a fluid channel and a seat disposed within the housing.
A valve element is positionable within the housing by
fluid flow therethrough, the valve element, by applica-
tion thereto of reverse fluid flow being held in
engagement with the seat for closing the check valve and,
by application of forward fluid flow thereto, being un-
seated for opening the check valve. An apertured guide
body includes leading and trailing apertured, streamlined
faces and is disposed within the casing and defines, with
the valve element under conditions of normal fluid flow,
an inner wall of the fluid passage The apertures
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accommodate reverse flow therethrough for application
of the reverse flow to the valve element for seating
the valve element and closing the check valve. me
check valve is characterized by the valve element
comprising a concave shell, forward fluid flow through
the valve impinging on an exterior face of the v lve
element unseating the valve element such that the lead-
ing guide body face is received at least in part in-
teriorly of the valve element.
The above and other objects which will become more
apparent from the following detailed description taken
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in connection with the appended claims and accOJnpanying
drawings are achievea by the check valve of the present
invention which is provided with an apertured aerodynamic
- guide body and an aerodynamic poppet or valve member dis-
posed within a housing such that in forward flow condition~,
the valve element and guide body define a streamlined
center body which, with the valve housing, define a flow
passage of generally constant cross sectional area there-
along. Reverse flow through the valve is accommodated
by the apertures in the guide body, the reverse flow being
applied to an expansive concave surface of the poppet
which rapidly seats under the influence of the reverse
flow, thereby blocking flow through the valve. A dampîng
piston and sleeve arrangement is received within the
interior of the guide body, the poppet being secured to
either the piston or sleeve such that relative movement
therebetween damps the poppet, thereby minimizing unwanted
poppet oscillation and impact loads. The cylinder is
vented to reduce the spring rate of the piston-sleeve
arrangement to prevent piston bounce under valve opening
conditions. The vent also reduces the magnitude of the
vacuum drawn by the cylinder which would otherwise
hamper valve closing. In the preferred embodiment, the
sleeve is contiguously received within the cylinder,
the cylinder and sleeve providing extensive bearing sur-
faces accommodating motion of the valve element within
the check valve to prevent unwanted flutter or other
vibration.
Brief Description of the Drawings
Fig. 1 is a side elevation in partial cross section
of the check valve of the present invention.
Fig. 2 is an end elevation of the valve.
Fig. 3 is an elevation of the opposite end of the
check valve.
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Referring to the dra~ings, the check valve of the
present invention is sho~m generally at 10 comprising a
housing 15 having mounting flanges 20 and 25 at opposite
ends thereof for mechanically connecting the valve to a
pair of opposed duct ends. The housing also includes at
the interior thereof an annular seat 30 which engages
poppet or valve element 35 for closing the valve under
conditions of reverse flow (flow to the right in Fig. 1).
Disposed within housing 15, and supported on struts
40 is a streamlined, aerodynamic guide body 45 which pxo-
vides minimal opposition to forward flow. ~s best seen in
Fig. 3, the struts are disposed between the housing and
guide body and extend in directions defined by components
both radially outwardly from, and tangential to the guide
body, such strut orientation allowing thermal and fluid
pressure loading to be accommodated by a bending of the
struts without overstressing of the attachment points of
the struts to the housing ana guide body.
Guide body 45 comprises leading and trailing (with
respect to forward flow) faces 50 and 55, respectively,
joined at 58 by any suitable means such as welding,
brazing or similar bonding or suitable fasteners such as
rivets or the like. Leading face 50 is apertured at 60
while trailing face 55 is apertured at 65, the apertures
readily accommodating reverse flow through the valve for
application of such reverse flow to valve element 35 for
the seating thereof. (See phantom lines in Fig. 1.) As
shown, apertures 65 are substantially smaller than
30 apertures 60, both apertures 60 and 65 being diposed gen-
erally centrally of the leading and trailing faces. While
this genera-l relative sizing and spacing of the apertures
is suitable for a compressor bleed air check valve for a
gas turbine engine, it will be understood that the check
valve of the present invention is not so limited, the size
and spacing of the apertures being dictated by the type
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of fluid accommodated by the valve and the o~erating
temperatures and pressures of that fluid.
The leading and trailing guide body faces are of a
conical or convergent shape and provide mounts for damping
cylinder 70 disposed interiorly of the guide body generall~
centrally thereof. The cylinder is provided with a vent
75 at the downs-tream end thereof and accommodates a
sleeve 85, generally contiguously to the cylinder interior.
The cylinder and sleeve define a damping means or dashpot
f~r minimization of valve element oscillation and impact.
The vent softens or decreases the spring rate o the sleeve-
cylinder arrangement to prevent valve element bounce when
- the valve is opened. The vent also aids in the draw of
fluid into the cylinder under checking conditions, thereby
militating against the formation of a vacuum within the
cylinder which would interfere with the closing of the valve.
Valve element 35 is of a conical or convergent shape
and is fixed to the end of sleeve 85 by any suitable means
such as bolt 90 and mating nut 95. ~1here as in the pre-
ferred embodiment, the cylinder and sleeve extend substan-
tially the entire length of the check valve, it will be
appreciated that these two members define extensive bear-
ing surfaces to slideably support the valve while minimizing
flutter or other unwanted vibration of the valve element.
The outermost portion of valve element 35 seals with
the outermost edge of trailing face 55 when the valve is
open, and with seat 30 (as shown in phantom lines) when
the valve is closed. As best seen in Fig. 1, valve element
35 comprises a concave shell, forward fluid flow through
the valve being applied directly to the outer or convex
valve element surface thereby opening the valve, position-
ing the valve element such that the leading guide body
face is received in part interiorly of the valve element.
Reverse (checking) flow is applied through apertures 65
and 60 in the guide body to the inner (concave) face of
the valve element for seating against seat 30 thereby
closing the valve. As best seen in Fig. 1, trailing guide
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body face 55 and the valve element 35 being generally con,-
cal, define a streamlined center body within the interior
of the valve. This center body, and the interior of
housing 15 define a passage 100 sf generally uniform cross
sectional or flow area from one end thereof to the other.
It will be appreciated that this uniform flow area alony
with the streamlined shape of the center body defined by
the guide bo~y and valve element result in minimum pressure
drop across the check valve of the present invention.
Accordingly, it is noted that the check valve of the
present invention is characterized by a minimization of
pressure drop across the valve. The reciprocation of the
valve element between open and closed conditions is damped
by the sleeve-cylinder damping mechanism which, due to its
disposition within the interior of the valve provides
extensive bearing surfaces for the reciprocation of the
poppet. The cylinder vent militates against piston bounce
and hindrance of checking due to creation of a vacuum
within the cylinder. Being disposed within the guide body,
the cylinder and sleeve bearing surfaces are protected
from contamination over substantially their entire length.
The apertures provided in the leading and trailing faces
of guide body 45 allow rapid checking at low reverse flows.
Additionally, such low reverse flow checking is enhanced
by the concave shell construction of the valve element
itself, such structure providing effective capture of
reverse fluid flow.
While the check valve of the present invention is
illustrated without actuators or assists o any kind, the
operation of the valve being controlled by the direction
of the flow therethrough, it will be appreciated that
springs, actuators or other assists may be employed as
desired.
Although this invention has been shown and described
with respect to detailed embodi~ents thereof, it will be
understood by those skilled in the art that various
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changes in form and detail thereof may be made ~7ithout
departing from the spirit and scope of the claimed inve~-
tion.
.
