Patent Description:
In an aerospace gas turbine engine, pressurized air may be used as "muscle air" to control the operation of a pneumatically-operated compressor bleed valve that may be opened and closed to maintain the operability of the gas turbine engine. Depending on the operating conditions of the gas turbine engine and on the source of the pressurized air, some debris could potentially be carried by the pressurized air and the presence of such debris in the pressurized air delivered to the compressor bleed valve may not be desirable.

<CIT> discloses a prior art method as set forth in the preamble of claim <NUM>.

<CIT> discloses a prior art integral filter and regulator for a valve.

<CIT> discloses prior art systems for filtering particles from an airflow.

In one aspect, the disclosure describes a method of filtering pressurized air used to control a compressor bleed valve of a gas turbine engine as recited in claim <NUM>.

In another aspect, the disclosure describes a gas turbine engine system for filtering pressurized air used to control a compressor bleed valve of a gas turbine engine as recited in claim <NUM>.

The following description discloses systems and methods for filtering pressurized air used to control a pneumatically-operated compressor bleed valve of a gas turbine engine. In some situations, filtering the pressurized air upstream of the compressor bleed valve may prevent some of the debris carried by the pressurized air from being delivered to the compressor bleed valve. In some situations, filtering the pressurized air may promote reliability and consistency in the operation of the compressor bleed valve. In some embodiments, the filter may be disposed to encourage self-cleaning of the filter, which may reduce the need for maintenance or replacement of the filter. For example, the filter may be configured to encourage debris captured by the filter to be released from the filter and discharged to the ambient environment.

The term "connected" may include both direct connection (in which two elements contact each other) and indirect connection (in which at least one additional element is located between the two elements).

The term "substantially" as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

<FIG> illustrates an exemplary gas turbine engine <NUM> (referred hereinafter as "engine <NUM>"), which may be of a type preferably provided for use in subsonic flight of an aircraft. Engine <NUM> may comprise, in serial flow communication, propeller <NUM> through which ambient air is propelled, compressor <NUM> for pressurizing the air, combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and turbine section <NUM> including one or more turbines for extracting energy from the combustion gases. Compressor <NUM> of engine <NUM> may be a multi-stage compressor, and thus may comprise a plurality of axial and/or centrifugal compressor stages. Compressor <NUM>, combustor <NUM> and turbine section <NUM> may be operatively disposed along gas path <NUM> of engine <NUM>. In some embodiments, engine <NUM> may be a reverse-flow turboprop gas turbine engine. Even though <FIG> illustrates a turboprop engine, it is understood that the systems and methods described herein may be incorporated into other types of gas turbine engines including engines of the turbofan and turboshaft type. It is also understood that the systems and methods described herein may be incorporated into aircraft and ground-based gas turbine engine applications.

Engine <NUM> may include system <NUM> for filtering pressurized air that is used as "muscle air" to control a function of compressor bleed valve <NUM> (referred hereinafter as "bleed valve <NUM>") of engine <NUM>. Bleed valve <NUM> may be pneumatically-operated and may be opened to release air from compressor <NUM> to ambient environment <NUM>. Bleed valve <NUM> may be opened to relieve pressure in a portion of gas path <NUM> at a stage of compressor <NUM>. Bleed valve <NUM> may be a poppet valve having a hole, usually round or oval and a tapered plug, usually a disk shape on the end of a shaft. The shaft may guide the plug portion by sliding through a valve guide. A pressure differential may be used to seal the valve and, under certain operating conditions, open the valve. In some embodiments, bleed valve <NUM> may be similar to the type of air bleed valve disclosed in <CIT> (titled: AIR FILTRATION SYSTEM FOR GAS TURBINE ENGINE PNEUMATIC SYSTEM). System <NUM> may receive pressurized air from gas generator casing <NUM> of engine <NUM> and may distribute the pressurized air between bleed valve <NUM> and ambient environment <NUM> as explained below.

The function of bleed valve <NUM> may be controlled by forces acting on opposite sides of bleed valve <NUM> which may relate to the respective air pressures P1, P2 at different locations along gas path <NUM>. In some embodiments of bleed valve <NUM>, a spring may be provided to bias bleed valve <NUM> toward the open or closed position. In reference to <FIG>, pressure P1 may be taken in gas path <NUM> at an intermediate stage of compressor <NUM>, and P2 may be taken in gas path <NUM> downstream of the location of P1. For example, pressure P2 may be taken downstream of compressor <NUM> and upstream of combustor <NUM> so that pressure P2 may be higher than pressure P1. Pressure P2, or another pressure indicative thereof, may be acquired via bleed air taken from gas path <NUM> at the desired location along gas path <NUM>. The bleed air may be delivered to bleed valve <NUM> via orifice pack <NUM>. In some embodiments, pressure P2 may be taken at a location along gas path <NUM> providing the highest pressure within engine <NUM>. Changes in the P1/P2 pressure relationship may cause bleed valve <NUM> to move between the open and closed positions. During operation of engine <NUM>, bleed valve <NUM> may be controlled by P1/P2 to maintain the operability of engine <NUM>. In some situations, bleed valve <NUM> may, for example, prevent compressor stall at relatively low operating speeds of engine <NUM>.

<FIG> is a schematic view of an exemplary system <NUM>. System <NUM> may include first conduit <NUM> including inlet <NUM> for receiving the pressurized (e.g., bleed) air F, outlet <NUM> for releasing a first portion F1 of pressurized air F from first conduit <NUM>, and port <NUM> for releasing a second portion F2 of pressurized air from first conduit <NUM>. First portion F1 and second portion F2 of pressurized air F may be different from each other so that F = F1 + F2. Port <NUM> may be disposed between inlet <NUM> and outlet <NUM>. In some embodiments, first conduit <NUM> may define a diffusion chamber between inlet <NUM> and outlet <NUM>. The diffusion chamber of first conduit <NUM> may have a cylindrical configuration. Port <NUM> may be formed in a wall of the diffusion chamber defined by first conduit <NUM>.

In some embodiments, inlet <NUM> may include an inlet orifice defining a constriction (i.e., narrowing or reduced cross-sectional area of the available flow passage) relative to at least part of first conduit <NUM>. In some embodiments, outlet <NUM> may similarly include an outlet orifice defining a constriction relative to at least part of first conduit <NUM>. In some embodiments, the inlet orifice and the outlet orifice may be sized to provide a desired flow rate and pressure drop across each of the inlet orifice and the outlet orifice. Such sizing may be based on specific operating parameters of engine <NUM> and the desired operating behaviour of bleed valve <NUM>. In some embodiments, the inlet orifice and/or the inlet orifice may be configured as replaceable inserts to facilitate the use of orifice packs of similar configurations on different engines.

System <NUM> may include filter <NUM> for filtering second portion F2 of pressurized air F. Filter <NUM> may be in fluid communication with first conduit <NUM> via port <NUM> and an upward flow path <NUM> extending upwardly from port <NUM> to filter <NUM>. In various embodiments, upward flow path <NUM> may be shorter or longer and may include an interior of filter <NUM> where filter <NUM> has a cylindrical configuration for example.

System <NUM> may include second conduit <NUM> in fluid communication with filter <NUM> and disposed to direct second portion F2 of pressurized air F from filter <NUM> to bleed valve <NUM> after second portion F2 of pressurized air F has passed through filter <NUM>. In some embodiments, first conduit <NUM>, filter <NUM> and second conduit <NUM> may be integrated into orifice pack <NUM> which may include an assembly of components integrated as a module operatively connectable to bleed valve <NUM>. In some embodiments, part(s) (e.g., first conduit <NUM> and second conduit <NUM>) of orifice pack <NUM> may be machined from a block of metallic material and filter <NUM> may be removably installed at the desired location. In some embodiments, orifice pack <NUM> may be a line replaceable unit. First conduit <NUM> and second conduit <NUM> may be constructed from suitable tubing, pipe or channel made from suitable metallic or other material(s). In some embodiments, upward flow path <NUM> may be defined by a suitable conduit of similar or other construction.

During operation of system <NUM>, pressurized air F may be received into first conduit <NUM> via inlet <NUM>. First portion F1 of pressurized air F may be released out of first conduit <NUM> via outlet <NUM> of first conduit <NUM>. Second portion F2 of pressurized air F may be released from first conduit <NUM> via port <NUM> disposed between inlet <NUM> and outlet <NUM> relative to a streamwise direction along first conduit <NUM>. Second portion F2 of pressurized air F may be used as control (i.e., muscle) air for controlling the operation of bleed valve <NUM>. Second portion F2 of pressurized air F may be directed toward filter <NUM> along upward flow path <NUM> from port <NUM> to filter <NUM>. In some embodiments, port <NUM> may be disposed on an upper or lateral side of first conduit <NUM>. Second portion F2 of pressurized air F may pass through filter <NUM> and consequently be filtered by filter <NUM>. After filtering, second portion F2 of pressurized air F may be directed toward bleed valve <NUM> to control the operation of bleed valve <NUM>. In some situations, second portion F2 of pressurized air F may cause bleed valve <NUM> to open and to release some air from compressor <NUM> to ambient environment <NUM> to prevent compressor stall for example.

<FIG> illustrates a mode of operation where engine <NUM> is operative and pressurized air F is being supplied to first conduit <NUM> via inlet <NUM>. During this mode of operation, first portion F1 of pressurized air F may be greater than second portion F2 of pressurized air F. In some embodiments, first portion F1 of pressurized air F may be significantly greater than second portion F2 of pressurized air F. In some embodiments and situations, first portion F1 may represent about <NUM>% of pressurized air F, and second portion F2 may represent about <NUM>% of pressurized air F. <FIG> also shows a piece of debris <NUM> that could potentially find its way into first conduit <NUM> and be carried into upward flow path <NUM> by second portion F2 of pressurized air F. It is expected that debris <NUM> would be captured by filter <NUM> and prevented from reaching bleed valve <NUM> via second conduit <NUM>. Debris <NUM> could include a piece of sand or other foreign object that may be ingested by engine <NUM> for example.

In some embodiments, filter <NUM> may have a cylindrical shape where second portion F2 of pressurized air F is received into a central inner cavity of filter <NUM>, passes through filter <NUM> in radially outward directions, and is then directed to bleed valve <NUM> via second conduit <NUM>. Filter <NUM> may be cup-shaped or configured as a canister having opening 34A for receiving second portion F2 of pressurized air F and debris <NUM> entrained therewith. Opening 34A may be disposed downwardly to accommodate upward flow path <NUM> and also allow debris <NUM> collected in the internal cavity of filter <NUM> to fall out of filter <NUM> by the influence of gravity when engine <NUM> is shut down and the flow of pressurized air F into first conduit <NUM> is ceased or reduced as explained further below.

Vertical axis V is shown in <FIG> relative to the orientation of system <NUM> when installed in engine <NUM>. Vertical axis V shows the UP and DOWN directions. Even though upward flow path <NUM> is illustrated as being wholly vertical and upward from port <NUM> to opening 34A of filter <NUM>, it is understood that upward flow path <NUM> may be oriented at a non-zero angle from the vertical axis V. For example, upward flow path <NUM> may be oriented at an oblique angle to vertical axis V while still providing an upward flow path <NUM> from port <NUM> to filter <NUM>. In some embodiments, upward flow path <NUM> may include the internal cavity of filter <NUM>. In various embodiments, first conduit <NUM> may be oriented generally horizontally, vertically, or at an oblique angle from vertical axis V.

In some embodiments, filter <NUM> may be disc-shaped or may have other suitable configurations. The filtering medium of filter <NUM> may be a metallic mesh but other types of filtering media may also be suitable. In some embodiments, filter <NUM> may include a relatively fine mesh capable of filtering debris <NUM> as small as <NUM> microns in size for example.

<FIG> illustrates another mode of operation of system <NUM> where engine <NUM> is shut down and pressurized air F is no longer being supplied to first conduit <NUM> via inlet <NUM>. During this mode of operation, second portion F2 of pressurized air F may no longer be keeping debris <NUM> against an intake side of filter <NUM> and, in some situations, debris <NUM> may become dislodged from filter <NUM> and gravity may cause debris <NUM> to fall out of opening 34A, downwardly along upward flow path <NUM> and enter first conduit <NUM> via port <NUM>. <FIG> shows debris <NUM> in upward flow path <NUM> and falling downwardly toward first conduit <NUM>.

<FIG> illustrates another mode of operation where engine <NUM> is restarted after being shut down as shown in <FIG>. In this mode of operation, the supply of pressurized air F to first conduit <NUM> via inlet <NUM> is resumed. Since debris <NUM> has fallen into first conduit <NUM>, the flow of first portion F1 of pressurized air F may entrain debris <NUM> toward outlet <NUM> and cause debris <NUM> to be discharged from first conduit <NUM>. Hence the configuration of filter <NUM>, upward flow path <NUM> and first conduit <NUM> may promote self cleaning of filter <NUM> and reduce the need for maintenance or replacement of filter <NUM> in some situations. It is understood that the arrangement illustrated herein may not cause all debris to be removed from filter <NUM> and that some maintenance or replacement of filter <NUM> may still be required in some situations.

<FIG> is a perspective view of another exemplary system <NUM> for filtering pressurized air used to control bleed valve <NUM>. <FIG> is a cross-sectional view of system <NUM> taken along line <NUM>-<NUM> in <FIG>. System <NUM> may include components of system <NUM> described above. In relation to system <NUM>, like elements have been identified using reference numerals that have been incremented by <NUM>.

In some embodiments, first conduit <NUM> may be oriented to promote downward flow of first portion F1 of pressurized air F and consequently promote the expulsion of debris <NUM> shown in <FIG> to ambient environment <NUM>. Accordingly, outlet <NUM> of first conduit <NUM> may be lower than inlet <NUM> of first conduit <NUM> relative to vertical axis V.

In various embodiments, upward flow path <NUM> extending from port <NUM> to filter <NUM> may be defined by a single linear segment or by two or more linear segments as shown in <FIG>. It is understood that upward flow path <NUM> may be curved, or may include a combination of one or more linear segments (e.g., at non-zero angles of each other) and one or more curved segments. In various embodiments, upward flow path <NUM> may provide a downward path for debris <NUM> to fall back into first conduit <NUM> when engine <NUM> is shut down or the flow of pressurized air F into first conduit <NUM> is otherwise reduced or stopped.

In accordance with the invention, where filter <NUM> has a cylindrical configuration, filter <NUM> has an axis A1 of revolution oriented obliquely to a longitudinal axis A2 of first conduit <NUM> by angle α. Filter <NUM> may be disposed inside filter housing <NUM>. In some embodiments, first conduit <NUM> may be generally linear but may instead include one or more curved segments. In some embodiments, filter <NUM> and upward flow path <NUM> may be substantially coaxial. In some embodiments, port <NUM> may be disposed on a lateral side of first conduit <NUM>. In reference to <FIG>, second conduit <NUM> providing fluid communication between filter <NUM> and bleed valve <NUM> is disposed behind other structure of system <NUM> and is not visible.

The orientation of first conduit <NUM> depicted where outlet <NUM> is lower than inlet <NUM> and/or where angle α is obtuse may discourage debris <NUM> from entering upward flow path <NUM> due to the influence of gravity, the inertia of debris <NUM> flowing downwardly along first conduit <NUM>, and the magnitude of the change in course required by debris <NUM> to enter upward flow path <NUM>. The orientation of upward flow path <NUM> relative to first conduit <NUM> may require debris <NUM> to change course by an obtuse angle α in order to enter upward flow path <NUM>. In other words, the general flow direction of pressurized air F (i.e., F1+F2) or of first portion F1 in first conduit <NUM> and the general flow direction of second portion F2 of pressurized air F in upward flow path <NUM> may be at an obtuse angle α of each other. In some embodiments, obtuse angle α may be equal to or greater than <NUM>° for example. In some embodiments, obtuse angle α may be between <NUM>° and <NUM>° for example.

<FIG> is a perspective view of another exemplary system <NUM> for filtering pressurized air used to control bleed valve <NUM>, which falls outside the wording of the claims. <FIG> is a cross-sectional view of system <NUM> taken along line <NUM>-<NUM> in <FIG>. System <NUM> may include components of systems <NUM>, <NUM> described above. In relation to system <NUM>, like elements have been identified using reference numerals that have been incremented by <NUM>.

In reference to <FIG>, part of second conduit <NUM> providing fluid communication between filter <NUM> and bleed valve <NUM> is disposed behind other structure of system <NUM> and is only partially visible. First conduit <NUM> of system <NUM> may be substantially identical or similar to first conduit <NUM> of system <NUM>. In contrast with system <NUM>, system <NUM> may be configured so that axis A1 of revolution of filter <NUM> may be substantially parallel to longitudinal axis A2 of first conduit <NUM>. Filter <NUM> may be disposed inside filter housing <NUM>. A seal may be formed between filter housing <NUM> and filter <NUM> using a suitable (e.g., high-temperature) packing material.

Upward flow path <NUM> may comprise one or more linear segments providing fluid communication between filter <NUM> and first conduit <NUM>. The one or more segments of upward flow path <NUM> may each have an upward orientation relative to a streamwise direction of second portion F2 of pressurized air F. For example, upward flow path <NUM> may include a first segment extending from port <NUM> defined in first conduit <NUM> and extending transversely to longitudinal axis A2 of first conduit <NUM>. Upward flow path <NUM> may include a subsequent segment extending substantially coaxially with axis A1 of revolution of filter <NUM>. Similarly to systems <NUM> and <NUM>, upward flow path <NUM> may provide a downward path for debris <NUM> to fall from filter <NUM> and into first conduit <NUM> when engine <NUM> is shut down so that debris <NUM> may later be expelled via outlet <NUM>.

<FIG> is a flowchart illustrating an exemplary method <NUM> for filtering pressurized air used to control bleed valve <NUM> of engine <NUM>. Method <NUM> may be used with any one of systems <NUM>, <NUM>, <NUM> or with other system(s). Method <NUM> may be combined with steps or aspect of other methods described herein. Aspects of systems <NUM>, <NUM>, <NUM> may be incorporated into method <NUM>. In various embodiments, method <NUM> may include:.

Filtering second portion F2 of pressurized air F using filter <NUM>, <NUM>, <NUM> may include collecting debris <NUM> at filter <NUM>, <NUM>, <NUM>. Method <NUM> may include ceasing to receive pressurized air F in first conduit <NUM>, <NUM>, <NUM> via inlet <NUM>, <NUM>, <NUM>. This may occur when engine <NUM> is shut down or the flow of pressurized air F to first conduit <NUM>, <NUM>, <NUM> is switched off for example. As shown in <FIG> as an example, method <NUM> may include receiving debris <NUM> collected at filter <NUM>, <NUM>, <NUM> into first conduit <NUM>, <NUM>, <NUM> via upward flow path <NUM>, <NUM>, <NUM> and port <NUM>, <NUM>, <NUM>.

After receiving debris <NUM> into first conduit <NUM>, <NUM>, <NUM>, method <NUM> may include restarting to receive pressurized air F in first conduit <NUM>, <NUM>, <NUM> via inlet <NUM>, <NUM>, <NUM>. This may occur when engine <NUM> is restarted after a period of shutdown or the flow of pressurized air F to first conduit <NUM>, <NUM>, <NUM> is switched on for example. As shown in <FIG>, method <NUM> may include discharging debris <NUM> from first conduit <NUM>, <NUM>, <NUM> via outlet <NUM>, <NUM>, <NUM> of first conduit <NUM>, <NUM>, <NUM>.

Discharging debris <NUM> from first conduit <NUM>, <NUM>, <NUM> via outlet <NUM>, <NUM>, <NUM> of first conduit <NUM>, <NUM>, <NUM> may include entraining debris <NUM> out of first conduit <NUM>, <NUM>, <NUM> using first portion F1 of pressurized air F.

First portion F1 of pressurized air F may be greater (have a greater pressure) than second portion F2 of pressurized air F.

Upward flow path <NUM>, <NUM>, <NUM> extending from port <NUM>, <NUM>, <NUM> to filter <NUM>, <NUM>, <NUM> may include one or more linear segments and/or one or more curved segments.

Filter <NUM>, <NUM>, <NUM> has a cylindrical configuration. Filtering second portion F2 of pressurized air F using filter <NUM>, <NUM>, <NUM> may include collecting debris <NUM> inside filter <NUM>, <NUM>, <NUM>. Method <NUM> may include ceasing to receive pressurized air F in first conduit <NUM>, <NUM>, <NUM> via inlet <NUM>, <NUM>, <NUM>. Method <NUM> may include receiving debris <NUM> collected inside filter <NUM>, <NUM>, <NUM> into first conduit <NUM>, <NUM>, <NUM> via upward flow path <NUM>, <NUM>, <NUM> and port <NUM>, <NUM>, <NUM>.

In some embodiments of method <NUM>, a general flow direction of pressurized air F in first conduit <NUM>, <NUM>, <NUM> and a general flow direction of second portion F2 of pressurized air F in upward flow path <NUM>, <NUM>, <NUM> may be at an obtuse angle of each other.

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the attached claims.

Claim 1:
A method of filtering pressurized air used to control a compressor bleed valve (<NUM>; <NUM>) of a gas turbine engine (<NUM>), the method comprising:
receiving the pressurized air (F) in a conduit (<NUM>; <NUM>) via an inlet (<NUM>; <NUM>) of the conduit (<NUM>; <NUM>);
releasing a first portion (F1) of the pressurized air (F) out of the conduit (<NUM>; <NUM>) via an outlet (<NUM>; <NUM>; <NUM>) of the conduit (<NUM>; <NUM>);
releasing a second portion (F2) of the pressurized air (F) from the conduit (<NUM>; <NUM>) via a port (<NUM>; <NUM>) disposed between the inlet (<NUM>; <NUM>) and the outlet (<NUM>; <NUM>) of the conduit (<NUM>; <NUM>);
directing the second portion (F2) of the pressurized air (F) from the port (<NUM>; <NUM>) to a filter (<NUM>; <NUM>);
filtering the second portion (F2) of the pressurized air (F) using the filter (<NUM>; <NUM>); and
directing the second portion (F2) of the pressurized air (F) from the filter (<NUM>; <NUM>) toward the compressor bleed valve (<NUM>; <NUM>), wherein:
the filter (<NUM>; <NUM>) has a cylindrical configuration;
filtering the second portion (F2) of the pressurized air (F) using the filter (<NUM>; <NUM>) includes collecting debris (<NUM>) inside the filter (<NUM>; <NUM>); and
the method includes:
ceasing to receive the pressurized air (F) in the conduit (<NUM>; <NUM>) via the inlet (<NUM>; <NUM>); and
receiving the debris (<NUM>) collected inside the filter (<NUM>; <NUM>) into the conduit (<NUM>; <NUM>) via an upward flow path (<NUM>; <NUM>) and the port (<NUM>; <NUM>), wherein
the conduit (<NUM>) is substantially linear and has a longitudinal axis (A2),
characterised in that
the filter (<NUM>) has an axis of revolution (A1) oriented obliquely to the longitudinal axis (A2) of the conduit (<NUM>); and
the directing the second portion (F2) of the pressurized air (F) from the port (<NUM>; <NUM>) to the filter (<NUM>; <NUM>) is along the upward flow path (<NUM>; <NUM>).