Butterfly valve for regulating an air flow, comprising a double-plate butterfly disc

Abstract

The invention relates to a butterfly valve (10) for regulating an air flow, comprising: a longitudinal valve body (11); a butterfly disc (20) mounted in the valve body (11) so as to be able to rotate about a rotation axis between a closed position, in which the butterfly disc (20) prevents any circulation of air from the air inlet to the air outlet, and an open position, in which the butterfly disc (20) allows the circulation of air from the air inlet to the air outlet; and a drive shaft (30) rotating perpendicularly to the valve body (11), the butterfly disc (20) comprising two parallel sealed plates (21a, 21b) longitudinally spaced apart from each other on either side of the rotation axis when the butterfly disc is in the closed position, the plates forming a central recess therebetween in the closed position and being transversely offset from each other in the valve body (11), the central recess defining a passage for the circulation of the air flow when the butterfly disc (20) is in the open position.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: BUTTERFLY VALVE FOR REGULATING AIRFLOW COMPRISING A DOUBLE-PLATE BUTTERFLY

[0003] Technical field of the invention

[0004] The invention relates to a fluid flow control valve, particularly for air flow. The invention more specifically relates to an air flow control valve arranged in an aircraft engine environment, said valve comprising a double-plate butterfly valve, and to an air intake system on an aircraft engine comprising at least one such valve.

[0005] Technological background

[0006] Aircraft air systems use valves for multiple functions. Among these valves, the most common is the single-plate butterfly valve.

[0007] One of the most commonly used butterfly valves is the inclined-axis butterfly valve. The inclined axis provides continuous sealing around the circumference of the butterfly. However, the sealing segments are arranged in a groove around the edge of the butterfly and rub against the valve body, which can cause hysteresis in the regulation, particularly near the closing position.

[0008] Such an inclined axis butterfly valve is frequently implemented in air sampling systems or systems where the loads induced by operating pressures are highest.

[0009] However, the temperatures of the sampling ports on recent engines have increased significantly. This results in a rise in the operating temperature of the valve, and in particular of the valve's rotating guides, whose operating temperature limits reach those of typical technologies in the most demanding applications.

[0010] There are straight-axis valve designs in which the sealing segment is offset from the axis of rotation to maintain a continuous seal around the periphery of the butterfly valve. This necessitates a spherical disc bearing surface.

[0011] RECTIFIED SHEET (RULE 91) ISA / EP of the butterfly valve to allow its rotation. This spherical bearing surface is generally located within a bore of the valve body and constitutes a manufacturing constraint, making this concept uncommon.

[0012] For all single-plate butterfly valves with internal sealing, it has been observed that the wider the airflow operating range, the closer the operating point at minimum flow is to full closure. Consequently, the friction induced by the dynamic sealing of the butterfly valve is greater, resulting in higher operating hysteresis for the control valves.

[0013] Furthermore, on some air sampling systems, the use of two single-plate butterfly valves in series can lead to pressure buildup between the two valves in the closed position, depending on their internal sealing level. This can be problematic when the accumulated pressure exceeds the lower pressure port pressure. Moreover, this pressure becomes a determining factor for the downstream valve and the pressure resistance of the intermediate pipe.

[0014] A butterfly valve device is known from document EP0625658, which describes a valve comprising a butterfly formed of two substantially parallel edges rigidly connected to define a discoidal structure. The butterfly according to this document includes a peripheral groove allowing, in the open position, the passage of airflow only at the periphery. The base of this groove is located centrally around the axis of rotation of the butterfly, thus limiting the flow circulation area to a peripheral portion of the disc. However, such a configuration presents several drawbacks. Due to the presence of a rigid central connection between the two plates, no fluid passage is possible in a central area of ​​the butterfly. The flow circulation is therefore constrained to the periphery, which generates a concentration of flow velocities and significant pressure losses.Furthermore, the airflow interacts markedly with the peripheral sealing surfaces, which can lead to premature degradation of these surfaces and limit the regulation efficiency over time.

[0015] RECTIFIED SHEET (RULE 91) ISA / EP The inventors therefore sought to develop a new type of butterfly valve to overcome the disadvantages of currently available solutions.

[0016] Objectives of the invention

[0017] The invention aims to provide, in at least one embodiment, a valve whose design offers better resistance under the stress of a driving air environment.

[0018] The invention aims to provide, in at least one embodiment, a valve enabling the flow velocity to be reduced at the opening angles of said butterfly.

[0019] The invention also aims to provide, in at least one embodiment, a valve enabling more effective degradation of the discharge coefficient at small butterfly opening angles.

[0020] The invention also aims to provide, in at least one embodiment, a valve that reduces the impact of friction on the performance of the valve.

[0021] The invention also aims to provide, in at least one embodiment, a valve whose geometry allows the aerodynamic torque of the circulating airflow to be reduced.

[0022] The invention also aims to provide, in at least one embodiment, a valve designed to reduce the operating delay when regulating the airflow.

[0023] The invention also aims to provide, in at least one embodiment, a valve to limit the accumulation of pressure downstream of the valve when the downstream permeability is almost zero and the valve is closed.

[0024] The invention also aims to provide an air sampling system equipped with such a valve.

[0025] The invention aims to provide a valve that increases the effective passage area of ​​the airflow, reduces pressure losses and preserves the integrity of the peripheral seal by avoiding excessive concentration of the flow at the edges or corners of openings.

[0026] RECTIFIED SHEET (RULE 91) ISA / EP Statement of Invention

[0027] To this end, the invention relates to a butterfly valve for regulating an airflow comprising:

[0028] - a valve body extending in a longitudinal direction and defining a circulation channel for said airflow comprising respectively an air inlet and an air outlet;

[0029] - a butterfly mounted to rotate in said valve body around an axis of rotation, between a first position, called the closed position, in which said butterfly prevents any circulation of air from said air inlet to said air outlet, and at least a second position, called the open position, in which said butterfly allows the circulation of air from said air inlet to said air outlet;

[0030] - a rotating drive shaft of said butterfly defining said axis of rotation.

[0031] The valve according to the invention is characterized in that said butterfly comprises two parallel sealing plates spaced longitudinally apart from each other, on either side of the axis of rotation, when said butterfly is in the closed position, said plates forming a central recess between them in said closed position and being offset transversely from each other in said valve body, said central recess defining a circulation channel for said airflow when the butterfly is in said open position.

[0032] The butterfly valve structure according to the invention allows for the formation of an airflow channel between the plates in the open position. This channel is formed by a central recess between the two butterfly plates. This central recess, as defined in the invention, is preferably an unobstructed space, meaning it is free of spacers or any other equivalent means of maintaining a distance between said plates. This feature of the invention eliminates the need for a visible axis in the flow when the butterfly is in the open position. However, a central recess comprising a space occupied by elements designed to improve the mechanical strength of the butterfly or

[0033] RECTIFIED SHEET (RULE 91) ISA / EP adapting the aerodynamic torque and / or the direction of the flow at the outlet of the throttle could be considered.

[0034] For the purposes of this invention, a flow channel is defined as a fluid passage formed between the inner faces of the two butterfly valve plates. Thus, the invention allows, when the valve is in the open position, for a central and predominant passage of airflow between the two plates, rather than around their periphery. In the closed position, any leakage flow is directed into a central recess.

[0035] The invention aims to provide a regulating butterfly valve that allows for better distribution of airflow through the valve in the open position, with reduced pressure losses and preservation of peripheral sealing areas. To this end, the invention provides a butterfly formed of two longitudinally spaced sealing plates, without a central connection, thus defining a clear central recess which, in the open position, forms an airflow channel extending between an inlet and an outlet of this channel, within the circulation channel of the valve body.

[0036] Thanks to this configuration, the flow can preferentially occur centrally, through the recess, without obstruction on the axis of rotation. This allows for a smoother, more homogeneous flow and reduces stress on the peripheral areas of the valve.

[0037] Furthermore, the sealing plates of the butterfly valve according to the invention are spaced longitudinally apart. In other words, the plates are offset longitudinally from the axis of rotation.

[0038] Furthermore, the plates are offset radially from each other relative to the flow direction and perpendicularly to the longitudinal direction of the valve body so that the seal of one plate does not interfere with the other plate during butterfly rotation. This allows for larger opening angles during butterfly rotation.

[0039] Throughout the text, it is understood that the plates are offset transversely or perpendicularly from each other in the said valve body.

[0040] RECTIFIED SHEET (RULE 91) ISA / EP when the butterfly is in the closed position.

[0041] The valve according to the invention can be controlled to be in an open or closed position depending on the respective positions of the butterfly valve, said position being a variant between fully closed and fully open. It is thus understood within the meaning of the invention that there are a plurality of open positions between a position, called fully open, corresponding to a maximum opening angle of the butterfly valve plates, ensuring a maximum flow rate of the air circulating in the passage formed between the two butterfly valve plates, and a position, called fully closed, corresponding to the closing angle of the butterfly valve plates, ensuring a flow rate, excluding internal leakage, substantially zero of the air flow in said passage.

[0042] For the purposes of this invention, an open position corresponds to a position where the plates are inclined relative to the longitudinal direction of the valve body so as to allow the airflow to pass through the circulation channel formed between said plates. The closed position corresponds to the position where the plates are substantially perpendicular to the direction of the valve body and the circulation channel formed by the latter.

[0043] During full closure, residual air pressure or leakage flow can accumulate in the central recess depending on the pressure upstream and downstream of the respective plate seals. This pressure differential can then increase the level of internal leakage and consequently cause valve malfunction.

[0044] When the butterfly valve is in the closed position, a leakage permeability can be created between the two butterfly plates, allowing the pressure built up during full closure between the two plates to be discharged into the central recess. The valve body is thus segmented by a plate upstream of the airflow and a plate downstream of the airflow. This arrangement reduces the level of internal leakage because the downstream segmentation is subject to a smaller pressure differential.

[0045] Indeed, the central hollow forms an intermediate chamber within the body

[0046] RECTIFIED SHEET (RULE 91) ISA / EP of valve, this chamber is thus isolated from upstream and downstream with respect to the circulating flow and constitutes an internal leakage reservoir whose pressure on the plate downstream will be much less important.

[0047] The opening angles of a valve are a critical factor when regulating airflow, particularly airflow from an aircraft engine environment.

[0048] With the proposed solution, the path of the air circulating in the circulation corridor formed between the plates, when the butterfly is in the open position, makes it possible to degrade the effective section by reducing the surface area crossed by the circulating flow, which results in larger opening angles at low flow rates and avoids friction on the valve seal.

[0049] Furthermore, the airflow path within the channel formed between the plates, when the butterfly valve is in the open position, advantageously creates different pressure fields on the upstream and downstream sides of the two plates. This helps to limit the impact of the aerodynamic torque of the air transmitted to the actuator shaft or to promote a driving torque during closing, for example. The reduction of aerodynamic torque also contributes to lessening its impact on the valve's operation and the expected operating conditions.

[0050] The invention thus proposes a double plate butterfly valve with a straight axis and having a double eccentricity for each of the plates advantageously allowing to reduce the operating hysteresis inherent in the air flow circulating in the valve in operation.

[0051] The solution proposed by the inventors makes it possible to offer twice as much surface area as a simple butterfly or single-plate and to reduce the passage cross-section at small opening angles while maintaining maximum permeability at full opening.

[0052] According to the invention, it is thus possible to modify the airflow through the valve by changing the geometry of the flow section using the double-plate butterfly. Modifying the geometry of the flow section by rotating the plates towards an open position allows for a reduction in the

[0053] RECTIFIED SHEET (RULE 91) ISA / EP discharge coefficient on small opening angles to allow the valve to benefit from larger opening angles at equal flow and thus reduce the impact of plate friction on the overall performance of the valve.

[0054] Furthermore, according to the invention, the butterfly plates can be of different shapes and are not limited to a circular disc shape.

[0055] Advantageously and according to the invention, said valve further comprises sealing means arranged peripherally between said butterfly and said valve body, said means being configured to compensate for the transverse offset of said plates relative to each other when the butterfly is in the closed position.

[0056] According to this advantageous variant, the seal is contained at the interface of each of the plates in the valve body.

[0057] Sealing means may be selected from sealing segments, O-rings, or any other suitable means designed to maintain the seal of a valve. It is understood that the sealing means may be shaped to the cross-section of the valve body and / or the geometry of said plates.

[0058] Advantageously and according to the invention, the airflow corridor formed between said plates has an angle of inclination of between 0° and 90° with respect to the longitudinal direction of said valve body when said butterfly is in said open position.

[0059] According to this advantageous variant, the valve allows for optimal regulation close to closure by limiting the flow area while promoting valve operation at low flow rates. Indeed, when the flow arrives at high speed, this helps to limit the stresses applied to the valve, particularly in the context of an aircraft engine environment.

[0060] Furthermore, with a double plate, the generated pressure field will be disturbed, thus favoring the aerodynamic torque in one direction of flow circulation or the other.

[0061] RECTIFIED SHEET (RULE 91) ISA / EP Advantageously and according to the invention, each of the plates has an asymmetric plate profile comprising two faces sealed to the airflow circulating with a first face, called the external face, and a second face, called the internal face.

[0062] According to this advantageous variant, it is possible to modify the pressure field applied between the two plates and therefore adapt the aerodynamic torque according to the need.

[0063] Advantageously and according to the invention, the valve body has a bulge arranged radially with respect to said circulation channel formed by the valve body, and in which said butterfly extends in the closed position.

[0064] The bulge is shaped to the spherical bearing surface of the butterfly valve plates according to the invention and includes sealing means.

[0065] Thus and according to this aspect of the invention, the bulge allows the circulation channel of the valve body to be segmented and the seal to be maintained when the butterfly is in the closed position while allowing a spherical bearing surface of the butterfly plates during rotation when said butterfly is in an open position.

[0066] Advantageously and according to the invention, said drive shaft comprises two trunnions, of which a first trunnion, called master trunnion, is configured to transmit the torque of an actuator to the second trunnion, called slave trunnion, said trunnions being coaxial and mechanically engaged with the two plates of said butterfly.

[0067] Thus, according to this advantageous variant, the butterfly valve is freed from an apparent axis in the flow, which helps to preserve the mechanical elements of the circulating airflow.

[0068] Advantageously and according to the invention, the valve further comprises an air pressure drainage system arranged between said sealing means on a portion of said valve body.

[0069] RECTIFIED SHEET (RULE 91) ISA / EP The drainage system may be arranged at the central cavity formed between the two plates of the butterfly when the latter is in the closed position.

[0070] The air pressure relief system can be passive or active. When the air pressure relief system is passive, the valve may include at least one orifice configured to connect the central recess to ambient air. It is understood that the central recess corresponds to the central cavity when the butterfly valve is in the closed position.

[0071] When the air pressure relief system is active, the valve may include an orifice in the axis of rotation of the trunnion opposite a vent port in the valve body. In this way, pressure relief occurs only when the valve is closed. The relief system can be active by being associated with an opening control element linked to the position of the butterfly valve or the valve actuation.

[0072] Thus, according to the invention, such a system makes it possible to reduce the intermediate pressure present between the two plates of the butterfly.

[0073] The drainage system can also be a system that can be activated in the closed position of the valve.

[0074] Advantageously and according to the invention, the air pressure drainage system is an active drainage system, in which the butterfly forms a central cavity in the closed position, said active drainage system comprising an air discharge channel through said valve body and configured to be able to spontaneously put into fluidic communication, when said butterfly is in said closed position, at least one air discharge orifice opening into said air discharge channel and said central cavity.

[0075] Thus, according to the invention, the valve may include a drainage system associated with an opening control element linked to the position of the butterfly or to the control of the valve.

[0076] Advantageously, and according to the invention, the pressure drainage system

[0077] RECTIFIED SHEET (RULE 91) ISA / EP of air is a passive drainage system comprising an air discharge channel through said valve body and configured to be able to spontaneously bring into fluidic communication an air discharge orifice opening into said air discharge channel and ambient air.

[0078] It is understood that ambient air is air external to the valve body and that fluid communication with ambient air can be achieved by any means known to a person skilled in the art.

[0079] According to this variant, the air evacuation orifice can be provided opposite the air discharge orifice and open into the central recess when the butterfly is in the closed position, the discharge channel being arranged on a portion of the valve body between the two butterfly plates.

[0080] According to another variant, the air vent can be provided on one end of a plate in order to form an internal air vent path in the plate to open directly into a discharge channel arranged opposite said vent when the butterfly is in the closed position.

[0081] According to one embodiment of the invention, each of said plates is formed by a disk with a circular profile. It should be understood that any other disk geometry may also be envisaged.

[0082] The invention also relates to an air sampling system on an aircraft engine comprising an air sampling channel in fluidic communication with said engine, characterized in that it comprises at least one butterfly valve for regulating an airflow arranged in said air sampling channel, said valve comprising all or part of the characteristics mentioned above.

[0083] Advantageously and according to the invention, the system comprises at least two butterfly valves arranged in series in said air intake channel.

[0084] According to this advantageous variant, the use of two butterfly valves according to

[0085] RECTIFIED SHEET (RULE 91) ISA / EP The invention, said valves being arranged in series, makes it possible to reduce the accumulated pressure that can be established between said valves when they are in the closed position.

[0086] Furthermore, the air sampling system according to the invention not only reduces the internal leakage flow at the outlet of the first valve, but also reduces the accumulation of depression between the first valve, called the upstream valve, and the second valve, called the downstream valve.

[0087] On an air sampling system as described above, the butterfly valve according to the invention advantageously reduces the internal leakage rate by 25% at the outlet of the first valve and reduces by 5% the pressure accumulated between two butterfly valves arranged in series in an air sampling system as described, compared with a conventional architecture using two single-plate butterfly valves arranged in series under the same air inlet pressure conditions and having the same leakage sections.

[0088] List of figures

[0089] Other objects, features and advantages of the invention will become apparent from the following description, given by way of non-limiting example only, and which refers to the accompanying figures in which:

[0090] - [Fig.1] represents a longitudinal section seen from above of a double plate butterfly valve according to an embodiment of the invention.

[0091] - [Fig.2] schematically represents the path of an airflow with a double plate butterfly valve according to an embodiment of the invention and with a single disc butterfly valve according to the prior art.

[0092] - [Fig.3] schematically represents a butterfly valve according to an embodiment of the invention when the butterfly is in the closed position.

[0093] - [Fig. 4] schematically represents a butterfly valve according to an embodiment of the invention when the butterfly is in a

[0094] RECTIFIED SHEET (RULE 91) ISA / EP open position.

[0095] Detailed description of an embodiment of the invention

[0096] In the figures, the scales and proportions are not strictly respected for the purposes of illustration and clarity.

[0097] In the entire detailed description that follows with reference to the figures, unless otherwise indicated, each element of the valve according to the invention is described as it is arranged in use.

[0098] Identical, similar or analogous elements are designated by the same references in all figures.

[0099] As shown in the figures, an airflow control valve 10 according to the invention comprises a valve body 11. The valve 10 is a straight-axis valve whose body 11 extends in a longitudinal direction. The valve body 11 of the valve 10 includes a butterfly 20 rotatably mounted within said valve body 11. Furthermore, said valve body 11 defines a circulation channel 11b for an airflow between portions 12 and 13 of said body 11, each of the portions 12 and 13 being respectively connected to an air inlet or outlet.

[0100] According to the embodiment shown, the valve 10 allows regulation of airflow in both possible directions, namely from portion 12 of the valve body 11 to portion 13 or vice versa. Furthermore, the valve 10 includes a butterfly 20 rotatably mounted within the valve body 11.

[0101] For this purpose, the valve body 11 includes a drive shaft 30 defining a rotation axis perpendicular to the butterfly 20 with respect to the longitudinal direction of said valve body 11. The shaft 30 includes two coaxial and transversely opposed trunnions 30a, 30b. Each of the trunnions 30a, 30b is arranged transversely on either side of the valve body 11 and is mechanically meshed with a pair of bearings 32 located outside the circulation channel. Each pair of bearings 32 is arranged in a plate outside the valve body 11. In the embodiment of the invention shown, the valve body 11 includes a first part located in the circulation channel, called the internal part, comprising the butterfly 20 mechanically connected to a portion of the trunnions 30a, 30b, and a second part,

[0102] RECTIFIED SHEET (RULE 91) ISA / EP, referred to as the external part, arranged outside the channel and comprising the bearings 32 and the plates. The bearings 32 are thus advantageously kept away from the airflow.

[0103] The butterfly 20 is a double-plate butterfly comprising two sealing plates 21a, 21b offset from the axis of rotation of the drive shaft 30. The two plates 21a, 21b are parallel to each other and spaced longitudinally in the direction of the valve body 11. In addition, the plates 21a, 21b are also offset transversely from each other in said valve body 11.

[0104] Each of the plates 21a, 21b of the butterfly valve 20 extends perpendicularly to the longitudinal direction of the valve body 11 when the butterfly valve is in the closed position, so as to prevent any circulation of airflow. In the closed position, the butterfly valve 20 forms a central recess 25 to collect any potential air leakage from the valve 10.

[0105] In this way, when the upstream plate opposes a higher air pressure likely to generate a higher potential leakage rate, when the butterfly 20 is in the closed position, the central recess 25 formed by the two plates 21a, 21b provides an internal leakage reservoir and thus helps to reduce the level of internal leakage by reducing the pressure exerted on the plate located downstream of the flow.

[0106] The downstream plate is thus subjected to a lower pressure differential, which reduces the risk of internal leakage of the valve 10. The invention thus allows a double segmentation of the air circulation channel aimed at reducing the pressure exerted on the plate downstream of the butterfly 20.

[0107] When the butterfly valve 20 is in an open position, the plates 21a, 21b form an airflow channel 22. This channel 22 is formed by the rotation of the butterfly valve 20 within the valve body 11. Furthermore, the channel 22 corresponds to an open position of the valve where the plates are no longer perpendicular to the direction of the body 11. More specifically, the airflow channel 22 corresponds to the formation of an angle of inclination α of each of the plates 21, 21b with respect to the longitudinal direction of the valve body 11 in an open position of the butterfly valve 20. This angle of inclination α corresponds to the opening angle of the butterfly valve.

[0108] RECTIFIED SHEET (RULE 91) ISA / EP Scion In the embodiment presented, the open position of the butterfly valve 20 allows the circulation of the airflow from the air inlet to the air outlet of the circulation channel formed by the valve body 11 and the channel 22 between the plates 21a and 21b of the butterfly valve 20. Each of the plates 21a and 21b has an asymmetrical profile comprising respectively an external face 23a, 23b and an internal face 24a, 24b. Thus, when the butterfly valve 20 is opened, corresponding to the opening of the valve 10, the particular geometry of the double-plate butterfly valve, according to the embodiment presented, makes it possible to reduce the discharge coefficient of the air circulating at small opening angles of the plates 21a, 21b, in order to allow operation with larger opening angles.

[0109] Furthermore, this helps to reduce the impact of butterfly friction 20 on the performance of valve 10.

[0110] A valve 10 as represented further includes sealing means 50 arranged peripherally between the butterfly 20 and the valve body 11.

[0111] Throughout the detailed description that follows, the 50 sealing means are sealing rings.

[0112] Furthermore, the sealing means 50 are arranged on the valve body and configured to provide internal sealing of the valve 10 when the butterfly 20 is in the closed position. These sealing means 50 are arranged in the valve body 11 around each of the plates 21a, 21b of the butterfly 20. When the valve 10 is closed, the butterfly is in the closed position and the plates 21a, 21b extend perpendicularly to the direction of the valve side 11 so as to rest on the seat formed by the sealing means 50. The sealing means 50 are configured to compensate for the transverse offset between the plates 21a and 21b.

[0113] In the closed position, the seal is thus ensured between the valve body 11 and each of the plates 21a, 21b of the butterfly 20.

[0114] A valve 10 equipped with a butterfly 20 also helps to reduce the pressure buildup that may occur downstream of said valve in the

[0115] CORRECTED SHEET (RULE 91) ISA / EP systems using two valves arranged in series, including air bleed systems on an aircraft engine.

[0116] In such a system, a double-plate butterfly valve according to the embodiment shown improves the valve's internal sealing performance and helps reduce pressure buildup between two valves arranged in series when they are in the closed position. Furthermore, the presence of a drainage system, in which an orifice is provided on the valve body 11, allows air passing through the valve body to be discharged to an orifice opening outside said valve body 11. This eliminates pressure buildup between two valves equipped with double-plate butterfly valves.

[0117] Figure 1 represents the valve 10 according to an embodiment of the invention in which the transmission of the rotational movement of the plates 21a and 21b of the butterfly 20 is ensured by a drive shaft 30 comprising two journals 30a and 30b. Each of said journals 30a, 30b is mechanically meshed with one end of the two plates 21a and 21b and respectively comprises an external portion guided in rotation by a pair of bearings 32, which can be considered as ball bearings. In addition, an element 31 provides the connection of one end of the two plates 21a, 21b with the journal 30a. An external actuator thus transmits the rotational movement to the butterfly 20 of the valve 10 via a master journal 30a configured to move a slave journal 30b.

[0118] Each of the plates 21a and 21b is thus offset with respect to the axis of rotation of the shaft 30, said axis being perpendicular to the circulation channel 11b of the valve body 11. The circulation channel 11b defined by the valve body 11 comprises the longitudinal portions 12 and 13 of said body 11 as well as the butterfly 20. In addition, the butterfly 20 is arranged inside said circulation channel 11b, the plates 21a and 21b extending perpendicularly to the longitudinal direction of the valve body 11 when the butterfly 20 is in the closed position.

[0119] In this figure, the butterfly 20 is in the closed position and the plates 21a, 21b

[0120] RECTIFIED SHEET (RULE 91) ISA / EP form a central recess 25 between them. Each of the plates 21a and 21b can be an upstream plate or a downstream plate depending on the direction of flow in the channel 11b. Indeed, if the air inlet is located on the side of the longitudinal portion 12 of the valve body 11, then plate 21a will form the upstream plate and plate 21b will form the downstream plate and vice versa.

[0121] Figure 2 schematically illustrates the difference in airflow circulation between a double-plate butterfly valve according to an embodiment of the invention and a conventionally used single-plate butterfly valve when the butterflies are in an open position.

[0122] According to this figure, the airflow circulates from plate 21b to plate 21a in the circulation channel 11b of the valve body 11. When using a double-plate butterfly valve according to the invention, the airflow discharge coefficient is significantly reduced, allowing, at the same flow rate, larger opening angles at the valve body 11 compared to a single-plate butterfly valve. In this figure, the airflow circulation in a valve according to this embodiment is represented by a solid arrow between the two plates 21b and 21a.

[0123] In contrast, for a conventional valve with a single-plate butterfly (210), the flow is split into two main streams at each end of the butterfly. This results, for an equivalent flow area, in an opening angle closer to the closed position, with an increased risk of friction on the closing seal. In this figure, the airflow in a conventional valve is represented by the two dashed arrows.

[0124] A valve according to the invention thus allows, for the same airflow rate, larger opening angles to be obtained, reducing friction hysteresis which is detrimental to the dynamic control of said valve. Furthermore, larger opening angles help maintain the valve's seal and consequently improve its service life.

[0125] Figure 3 schematically illustrates a valve 10 according to a mode of

[0126] RECTIFIED SHEET (RULE 91) ISA / EP embodiment of the invention with a butterfly 20 in the closed position. The valve body 11 is shown with a bulge 14 comprising sealing means arranged circumferentially between the valve body 11 and the butterfly 20.

[0127] In this figure, the sealing means 50 compensate for the transverse offset of the plates 21a and 21b relative to each other at their respective ends. Furthermore, this figure also illustrates the asymmetrical profile of the plates 21a and 21b of the butterfly valve 20, which respectively comprise an inner face 24a, 24b and an outer face 23a, 23b.

[0128] Figure 4 illustrates the embodiment of Figure 3 where the butterfly 20 is in the open position.

[0129] In this figure, a flow channel 22 is formed between plates 21a and 21b, more precisely between the inner faces 24a and 24b of said plates. The resulting openings 60 reduce the impact of butterfly friction on the sealing means 50 of the valve body 11. In the open position shown in this figure, the butterfly plates extend beyond the bulge 14 so that only one end of said plates is in contact with the sealing means 50. The transverse offset of plates 21a and 21b ensures that each does not interfere with the sealing of the other. When the valve is thus open, the flow in the flow channel 22 is also combined with peripheral flow at the ends of the plates and the valve body 11. This peripheral flow is, however, limited by the proximity of the plates to said body 11.

[0130] When the valve is in the open position, the central recess 25 forms the flow channel 22. The flow channel 22 extends between each of the plates 21a and 21b, along their length, so that the airflow can circulate from a channel inlet 61, formed between the lower ends of each plate, and a channel outlet 62, formed between the upper ends of each plate and the valve body. The airflow through the valve in the open position is therefore carried out by a main, central flow within the flow channel.

[0131] CORRECTED SHEET (RULE 91) ISA / EP

Claims

DEMANDS 1. Butterfly valve (10) for regulating an airflow comprising: - a valve body (11) extending along a longitudinal direction and defining a circulation channel for said airflow comprising respectively an air inlet and an air outlet; - a butterfly (20) mounted rotatably in said valve body (11) around an axis of rotation, between a first position, called the closed position, in which said butterfly prevents any circulation of air from said air inlet to said air outlet, and at least a second position, called the open position, in which said butterfly (20) allows the circulation of air from said air inlet to said air outlet; - a rotating drive shaft (30) of said butterfly defining said axis of rotation; said valve (10) being characterized in that said butterfly (20) comprises two parallel sealed plates (21a, 21b) spaced longitudinally apart from each other, on either side of the axis of rotation, when said butterfly is in the closed position, said plates (21a, 21b) forming a central recess between them in said closed position and being offset transversely from each other in said valve body (11), said central recess defining a circulation channel of said airflow when the butterfly is in said open position.

2. Valve according to claim 1, characterized in that it further comprises sealing means (50) arranged peripherally between said butterfly (20) and said valve body (11), said means (50) being configured to compensate for the transverse offset of said plates (21a, 21b) between them when the butterfly (20) is in the closed position.

3. Valve according to claim 1 or 2, characterized in that the airflow channel (22) formed between said plates (21) has an angle of inclination α between 0° and 90° with respect to the direction CORRECTED SHEET (RULE 91) ISA / EP longitudinal of said valve body (11) when said butterfly (20) is in said open position.

4. Valve according to any one of claims 1 to 3, characterized in that each of the plates (21a, 21b) has an asymmetrical plate profile comprising two faces sealed to the airflow circulating with a first face (23a, 23b), referred to as the external face, and a second face (24a, 24b), referred to as the internal face.

5. Valve according to any one of the preceding claims, characterized in that the valve body (11) has a bulge (14) arranged radially with respect to said circulation channel formed by the valve body (11) and in which said butterfly extends in the closed position.

6. Valve according to any one of the preceding claims, characterized in that said drive shaft (30) comprises two trunnions (30a, 30b), of which a first trunnion, called master trunnion (30a), is configured to transmit the torque of an actuator to the second trunnion, called slave trunnion (30b), said trunnions (30a, 30b) being coaxial and in mechanical contact with the two plates (21a, 21b) of said butterfly (20).

7. Valve according to any one of claims 2 to 6, characterized in that it further comprises an air pressure drainage system arranged between said sealing means (50) on a portion of said valve body (11).

8. Valve according to claim 7, characterized in that the air pressure drainage system is an active drainage system, in which the butterfly forms a central cavity in the closed position, said active drainage system comprising an air discharge channel through said valve body and configured to be able to spontaneously bring into fluidic communication, when said butterfly is in said closed position, at least one air discharge orifice opening into said air discharge channel and said central cavity.

9. Valve according to claim 7, characterized in that the air pressure drainage system is a passive drainage system comprising an air discharge channel passing through said valve body and configured to be able to spontaneously put into fluidic communication an air discharge orifice opening into said air discharge channel and ambient air. CORRECTED SHEET (RULE 91) ISA / EP 10. An air intake system for an aircraft engine comprising an air intake channel in fluidic communication with said engine, characterized in that it comprises at least one butterfly valve (10) for regulating an airflow according to any one of claims 1 to 9 arranged in said air intake channel.

11. A system according to the preceding claim, characterized in that it comprises at least two butterfly valves (10) according to any one of claims 1 to 9 arranged in series in said air intake channel. CORRECTED SHEET (RULE 91) ISA / EP

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