GB2085125A - Check valve - Google Patents

Abstract

A low pressure drop check valve includes an apertured streamlined guide body 45 mounted on struts which accommodate thermal loading and also includes a streamline poppet or valve member 35 disposed within a housing 15. Forward flow through the valve unseats the valve member, which receives a face 50 of the guide body, allowing flow around the valve member and guide body. Reverse flow is accommodated by the apertures 60 in the guide body, flow through the apertures being applied to a surface of the valve member 35, thereby seating the valve member for blocking such reverse flow. The check valve is also provided with means for minimizing valve member oscillation and bounce. <IMAGE>

Description

SPECIFICATION Check valve This invention relates generally to fluid check val ve & and more specifically to such check valves adapted for use in a compressor bleed flow system in a gas turbine engine.

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 surge 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 ofthe 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 20 bar at temperatures of about 430"C 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 against the durability 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 is 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 Buckner 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 reverse flow checking over the Ohta valve.

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 wherein 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 controlied checking under reverse flow conditions. The check valve of the present invention is provided with an apertured aerodynamic guide body and an aerodynamic poppet or valve memberdis- posed within a housing such that in forward flow conditions, the valve element and guide body define a streamlined center body mounted on struts which readily accommodate thermal loading of the valve.

The valve body and the valve housing define a flow passage of generally constant cross sectional area along the valve. Forward flow through the valve opens the valve element which in the open position receives a leading face of the guide body. 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 damping cylinder and sleeve arrangement is received within the interior of the guide body, the poppet being secured to eitherthe cylinder 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 cylinder sleeve arrangement to prevent valve element 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 surfaces accommodating motion of the valve element within the check valve to prevent unwanted flutter or other vibration.

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.

Referring to the drawings, the check valve of the present invention is shown 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 interiorthereof 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 provides minimal opposition to forward flow. As best seen in Fig. 2, 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 sturts without overstressing of the attachment points of the struts to the housing and 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 apertures 60, both apertures 60 and 65 being disposed generally centrally of the leading and trailing faces.While this general 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 of fluid accommodated by the valve and the operating temperatures and pressures of that fluid.

The leading and trailing guide bodyfaces are of a conical or convergent shape and provide mounts for damping cylinder 70 disposed interiorly of the guide body generally centrally thereof. The cylinder is provided with a vent 75 at the downstream end thereof and accommodates a sleeve 85, generally contiguously to the cylinder interior. The cylinder and sleeve define a damping means or dashpot for minimization of valve element oscillation and impact. The vent softens or decreases the spring rate of 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.

Where as in the preferred embodiment, the cylinder and sleeve extend substantially the entire length of the check valve, it will be appreceiated that these two members define extensive bearing surfaces to slideably support the valve element while minimizing flutter or other unwanted vibration of the valve element.

The outermost portion of valve element 35 seals 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, positioning 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 body face 55 and the valve element 35 being generally conical, define a streamlined center body within the interior of the valve.This center body, and the interior of housing 15 define a passage 100 of generally uniform cross sectional or flow area from one end thereof to the other. It will be appreciated that this uniform flow area along with the streamlined shape of the center body defined by the guide body and valve element result in miminum 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 valve element 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 rapid reverse flow checking is enhanced by the concave shell construction ofthevalve 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 of any kind, the operation of the valve being controlled by the direction oftheflowtherethrough, 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 embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.

Claims (7)

1. Afluid check valve comprising: a housing (15), defining an outer wall of a fluid passage; a seat (30) disposed within said housing; a valve element (35) positionable within said housing by fluid flow therethrough, said valve element, by application thereto of reverse fluid flow being held in engagement with said seat for closing said check valve and, by application of forward fluid flow thereto, being unseated for opening said check valve and an apertured guide body (45) disposed within said housing and defining, with said valve element under conditions or normal fluid fiow, an inner wall of said fluid passage, said apertures accommodating reverse flow therethrough for application of said reverse flow to said valve element for seating said valve element and closing said check valve, said check valve being characterized by:: said guide body (45) being mounted within the interior of said housing by a plurality of spaced struts (40), each of said struts being disposed between said housing and guide body and extending in directions defined by directional components both radially outward from and tangential to said guide body.

2. A fluid check valve comprising: a housing (15), defining an outer wall of a fluid passage; a seat (30) disposed within said housing; a valve element (35) positionable within said housing by fluid flow therethrough, said valve element, by application thereto of reverse fluid flow being held in engagement with said seatforclosing said check valve and, by application of forward fluid flow thereto, being unseated for opening said check valve and an apertured guide body (45) including leading and trailing apertured, streamlined faces (50, 55) and disposed within said housing and defining, with said valve element under conditions of normal fluid flow, an inner wall of said fluid passage, said apertures (60,65) accommodating reverse flow therethrough for application of said reverseflowto said valve element for seating said valve element and closing said check valve, said check valve being characterized by said valve element (35) comprising a concave shell, forward fluid through said valve impinging on an exterior face of said valve element unseating said valve element such that said leading guide body face (50) is received at least in part interiorly of said valve element.

3. A fluid check valve according to claim 1 or 2 further characterized by said valve element (35) and guide body (45) defining a streamlined center body having generally conical leading and trailing surface portions.

4. Afluid check valve according to claim 1 or 2 further characterized by said fluid channel defined by said housing (15), said guide body (45) and said valve element (35) being of substantially uniform flow area throughout the length thereof.

5. Afluid check valve according to claim 1 or 2, and further characterized by: a sleeve (85) fixed to one of said valve element (35) and guide body (45) and a cylinder (70) receiving said sleevetherewithin, said cylinder being fixed to the other of said valve element and guide body, said sleeve and cylinder providing means for damping oscillations of said valve element.

6. A fluid check valve according to claim 5 further characterized by said cylinder (70) including a vent aperture (75) therein for relief of fluid pressure within said cylinder to prevent valve element bounce as said sleeve moves toward said vent aperture and to enhance the intake of fluid to said cylinder as said sleeve moves away from said vent aperture.

7. A fluid check valve according to claim 5 further characterized by said sleeve (85) being contiguous to the interior of said cylinder (70), said cylinder and sleeve defining bearing surfaces on which said valve element (35) is supported for movement relative to said seat (30).