GB2464936A

GB2464936A - Butterfly valve

Info

Publication number: GB2464936A
Application number: GB0819801A
Authority: GB
Inventors: Peter David Hood
Original assignee: Intelligent Energy Ltd
Current assignee: Intelligent Energy Ltd
Priority date: 2008-10-29
Filing date: 2008-10-29
Publication date: 2010-05-05
Anticipated expiration: 2028-10-29
Also published as: GB2464936B; GB0819801D0

Abstract

A butterfly valve assembly comprises a valve body 110 having a fluid passage 115 defining a central axis 116. A planar baffle plate 150 is rotatably mounted within the passage about fulcrum 155. The baffle plate 150 has opposing vanes 150a, 150b and is rotatable between open and closed positions to respectively allow or restrict fluid flow through the passage 115. The baffle plate is elastically flexible to permit bending of the opposing vanes 150a, 150b during rotation from the closed to the open position.

Description

BUTTERFLY VALVE

The invention relates to valves, and particularly to valves of the type employing a pivoted vane or butterfly plate.

Butterfly valves are generally known in the art for controlling flow in various applications involving fluids. Typically, such valves comprise a circular or elliptical disk rotatably mounted within a circular cross-section of a valve housing, where rotation of the disk between a closed and open position allows control over the flow of fluid through the valve.

US 3,029,062 discloses a butterfly valve in which an elliptically-shaped disk is turned to and is tightened in a closed position, substantially at a right angle to the axis of the housing, and the disk is deformed in the direction of its major axis to a circular form. An improved seal around the disk is thereby achieved.

US 3,204,928 discloses a butterfly valve having adjustable means for a valveengaging surface, in which a rigid plate-like portion substantially co-extensive with and parallel to a flexible disc portion allows leakage to be prevented by flexing of the disc portion by means of thrust screws applying a force to the flexible portion.

When using such valves to control the flow of fluids containing water, such as liquid water or moisture-laden air, a problem can occur if the valve is subject to sub-zero (<0°C) temperatures. In such conditions the valve may freeze closed, particularly if residual water exists around the periphery of the butterfly plate. Given that the initial motion of the butterfly plate at least involves an element of shear between a periphery of the plate and the interior of the valve assembly, it may become difficult or impossible to break an ice formation through actuation of the valve until the valve has been sufficiently defrosted.

In the field of fuel cells, control of air flow to and from a fuel cell stack is important for proper and efficient operation of the stack. Application requirements for fuel cells, particularly in relation to automotive applications, can require reliable operation from starting in sub-zero conditions, which may be as low as -25°C or even lower. As the fuel cell system cools down from an operating temperature to a sub-zero temperature range, any residual water within the air inlet line will eventually freeze. This will cause ice to form, which may form around components such as valves. If a valve assembly configured to supply air to the fuel cell stack is unable to open during such conditions due to ice formation causing the valve assembly to seize, the fuel cell might not be able to generate sufficient heat to bring the temperature of the valve to above freezing point. Operation of the fuel cell system would consequently be delayed or prevented altogether while the temperature remains below freezing.

One solution would be to apply heat to the valve in the air inlet line, for example through use of a heating element around or within the valve. This would, however, add to the complexity to the system, and consume additional electrical power.

It is an object of the invention to solve one or more of the above mentioned problems,

In a first aspect, the invention provides a valve assembly comprising: a valve body having an inner cylindrical fluid passage defining a central axis therethrough; a planar baffle plate rotatably mounted within the passage about a fulcrum having a rotational axis orthogonal to the central axis, the baffle plate comprising opposing vanes extending from the fulcrum and being rotatable between a closed position to restrict fluid flow through the passage and an open position to allow fluid flow through the passage, in which an angle between the plane of the baffle plate and the central axis is less than 90 degrees in both the open and closed positions, wherein the baffle plate is elastically flexible to permit bending of the opposing vanes to separate a peripheral edge portion of each of the vanes from an inner surface of the valve body during rotation of the fulcrum away from the closed position and towards the open position.

The angle between the baffle plate and a plane orthogonal to the central axis is preferably greater than 2 degrees, and more preferably between 5 and 10 degrees, in the closed position. The valve assembly may further comprise a servo actuatable motor configured to rotate the fulcrum relative to the valve body about the rotational axis and bend the opposing vanes of the baffle plate to separate the peripheral edge portion of each of the vanes from the inner surface of the valve body during rotation of the fulcrum away from the closed position and towards the open position.

In a second aspect, the invention provides a method of operating a valve assembly according to the first aspect from an initial closed position, the method comprising: rotating the fulcrum about the rotational axis to cause the opposing vanes to flex; separating the peripheral edge portions of the vanes from the inner surface of the valve body; and rotating the vanes towards the open position.

A valve assembly according to the invention is thereby able to open from a fully closed position, and preferably operable as a proportional close-off valve in a sub zero environment (i.e. <0°C. and preferably <-25°C) in the presence of water ice.

The invention will now be described by way of example, and with reference to the enclosed drawings in which: figure 1 shows a schematic cross-sectional view of a valve assembly comprising a rotatable butterfly valve; and figure 2 shows a perspective view of a valve assembly comprising a rotatable butterfly valve.

Figure 1 shows a schematic cross-sectional view of a valve assembly 100 having a valve body 110, within which is mounted a butterfly valve 105. The valve body has an inner cylindrical fluid passage 115 defining a central axis 116 passing through the fluid passage 115. The butterfly valve 105 comprises a rotatable fulcrum 155 and a planar baffle 150. The planar baffle 150 comprises vanes 150a, 150b extending in opposing directions away from the fulcrum 155.

The baffle 150 is shown in figure 1 in three superimposed positions: a closed position 130, an open position 140 and an intermediate flexed position 160 between the closed 150 and open 140 positions. In the closed position 130, the baffle 150 restricts fluid from flowing through the fluid flow passage 115 in either direction by sealing against an internal surface 111 of the valve body 110. Rotation 156 of the baffle 150 from the closed position 130 towards the open position 140 allows fluid to pass through the inner cylindrical fluid passage 115 in the valve assembly 100, for example in an indicated flow direction 120 along the central axis 116 of the valve body 110.

During extended periods at sub-zero (<0°C) temperatures, ice may form on or around the baffle 150, typically as a result of residual liquid water that may be present within the valve assembly 100 as the valve assembly cools. Such residual liquid water may form from liquid droplets present in the fluid flow passage 115 and/or from water vapour condensing from the air within the fluid flow passage as the valve assembly 100 cools. Ice may prevent a conventional valve from operating, particularly if the ice forms where the edges of the baffle meet the internal surface of the valve body 110, as indicated by the ice formation 170 shown in figure 1. With a conventional baffle plate, rotation 156 of the baffle plate may be prevented, because the ice formation 170 prevents the edges of the baffle plate from shearing relative to the internal wall 111 of the valve body 110.

In the valve assembly 00 according to the present invention, however, flexibility of the baffle 150 allows rotation of the baffle 150 about the fulcrum 155 before the edges of the baffle plate separate from the internal surface of the valve body 110. This is achieved by the vanes 150a, 150b being flexible in bending. This flexibility allows for a progressive shearing action between the edges of the baffle plate relative to the internal surface 111 of the valve body 110. This progressive shearing action causes the vanes 150a, 150b to pull away from any ice formation 170 as the vanes 150a, 150b bend under the torque transmitted through the fulcrum 155. Preferably, the valve assembly comprises a servo-controllable motor connected to the fulcrum, the motor configured to apply the torque to the fulcrum to cause the baffle 150 to rotate and, if required, the vanes 150a, 150b to bend. Under normal use, i.e. with no ice formation, the vanes 150a, 150b do not bend appreciably, and the butterfly valve operates in a conventional way.

In order to ensure a combined shearing and pull-away action, the vanes of the baffle 150 are preferably oriented away from being orthogonal to the central axis

116, when in the closed position 130. This orientation also allows for an improved seal with the internal surface 111 of the valve body 110. In figure 1, the angle φ (shown exaggerated for clarity) is preferably greater than 2 degrees, optionally greater than 5 degrees and may be greater than 10 degrees. A particular preferred angle is around 5 degrees. The angle φ, alternatively described as a seat angle, ensures that when the valve is actuated rotation 156 about the fulcrum 155 causes the edges of the vanes 150a, 150b to be pulled inwards slightly in the initial process of separation from the internal surface 111 of the valve body 110. The effective baffle radius X consequently decreases, compared with an initial radius W, on initial rotation of the baffle as the vanes 150a, 150b flex. This flexing causes movement of the edges of the vanes 150a, 150b away from the internal surface 111 in a radial direction y and an axial direction z. A progressive release from the ice is thereby achieved without the need for excessive torque being applied through the fulcrum 155.

In a general aspect therefore, an angle between a plane defined by the baffle plate and the longitudinal axis 116 of the valve body 110 is less than 90 degrees in both the open position 140 and closed position 130. Alternatively, a seat angle φ is defined between the plane defined by the baffle plate and a plane orthogonal to the longitudinal axis 116, the seat angle being greater than 2 degrees, preferably around 5 degrees, and optionally less than 10 degrees.

Preferably, the vanes 150a, 150b of the baffle 150 are composed of a resiliently elastically flexible material, in which the required flexibility is present at sub-zero temperatures, preferably as low as -25°C. Polymeric materials are more preferable, in particular those having a glass transition temperature below this temperature. A particular preferred material is PTFE (polytetrafluoroethylene), although other materials may be suitable. To allow for sufficient flexibility, the vanes are preferably composed of a material having an elastic modulus less than 10GPa, optionally less than 5GPa and further optionally less than 2GPa, the elastic modulus preferably being greater than 0.1 GPa.

Shown in figure 2 is a perspective view of a valve assembly 100 having a construction in accordance with the valve assembly described above. The valve assembly 100 comprises a servo-actuatable motor 220 having an output shaft connected to or forming the fulcrum 155 about which the vanes 150a, 150b of the baffle are affixed. The baffle is shown in figure 2 in a partially open position, in which fluid can flow through the valve body 110 in the fluid flow direction 120 indicated. The servomotor 220 is operable to rotate the baffle 150 about the fulcrum axis 280, the fulcrum axis 280 being oriented generally orthogonal to the longitudinal axis 116 of the valve body 110.

Other embodiments are intentionally within the scope of the invention as defined by the appended claims.

Claims

CLAIMS 1. A valve assembly comprising: a valve body having an inner cylindrical fluid passage defining a central axis therethrough; a planar baffle plate rotatably mounted within the passage about a fulcrum having a rotational axis orthogonal to the central axis, the baffle plate comprising opposing vanes extending from the fulcrum and being rotatable between a closed position to restrict fluid flow through the passage and an open position to allow fluid flow through the passage, in which an angle between the plane of the baffle plate and the central axis is less than 90 degrees in both the open and closed positions, wherein the baffle plate is elastically flexible to permit bending of the opposing vanes to separate a peripheral edge portion of each of the vanes from an inner surface of the valve body during rotation of the fulcrum away from the closed position and towards the open position.
2. The valve assembly according to claim 1 wherein the angle between the baffle plate and a plane orthogonal to the central axis is greater than 2 degrees in the closed position.
3. The valve assembly according to claim 2 wherein the angle between the baffle plate and the plane orthogonal to the central axis is between 5 and 10 degrees in the closed position.
4. The valve assembly according to claim 1 further comprising a servo actuatable motor configured to rotate the fulcrum relative to the valve body about the rotational axis and bend the opposing vanes of the baffle plate to separate the peripheral edge portion of each of the vanes from the inner surface of the valve body during rotation of the fulcrum away from the closed position and towards the open position.
5. A method of operating a valve assembly according to claim 1 from an initial closed position, the method comprising: rotating the fulcrum about the rotational axis to cause the opposing vanes to flex; separating the peripheral edge portions of the vanes from the inner surface of the valve body; rotating the vanes towards the open position.
6. The method of claim 5 wherein flexing of the vanes causes the edges of the vanes to move away from the internal surface in a radial direction and an axial direction relative to the central axis.
7. The method of claim 5 or claim 6 wherein the valve assembly is operated at a temperature below 0°C.
8. A valve assembly substantially as described herein, with reference to the accompanying drawings.
9. A method of operating a valve assembly substantially as described herein, with reference to the accompanying drawings.