Ram filter purge system

An aircraft nacelle includes a forward cruise inlet, a forward-cruise-inlet conduit coupled to the forward cruise inlet and operable to supply air from the forward cruise inlet to an engine housed by the aircraft nacelle, an inlet barrier filter, an inlet-barrier-filter compartment coupled to the inlet barrier filter, a plurality of gills coupled between the inlet-barrier-filter compartment and the engine and operable to be in an open state and a closed state, a filter-purge door coupled to the inlet-barrier-filter compartment and operable to be in a closed state and an open state. When the plurality of gills are in the closed state and the filter-purge door is in the open state, air from the filter-purge door flows from the inlet-barrier-filter compartment through the inlet barrier filter.

TECHNICAL FIELD

This disclosure relates in general to the field of aircraft, and more particularly, but not by way of limitation, to filter systems for engines in aircraft.

BACKGROUND

Aircraft such as helicopters and tiltrotor aircraft often use pleated filter panels to protect engines of the aircraft when the aircraft are operating in environments in which contaminants such as sand & dust can be damaging to the engines during, for example, landing and takeoff. Gas turbine engines often used in such aircraft consume a considerable amount of air; as a result, panels of filters used to protect the gas turbine engines from contaminants can become plugged quickly when the aircraft are operating in a challenging environment.

In some aircraft, if a filter becomes plugged with contaminants, a bypass door opens to allow contaminated air to bypass the filter and enter the engine; however, allowing such air to enter the engine unfiltered can cause wear on the engine and reduced engine power. For a single landing, use of a bypass door may be acceptable, but if the aircraft has to sustain operations in challenging environments or conduct multiple landings, the filter will likely need to be bypassed multiple times, which could result in increased maintenance expense and reduced engine performance.

SUMMARY

An aircraft nacelle includes a forward cruise inlet, a forward-cruise-inlet conduit coupled to the forward cruise inlet and operable to supply air from the forward cruise inlet to an engine housed by the aircraft nacelle, an inlet barrier filter, an inlet-barrier-filter compartment coupled to the inlet barrier filter, a plurality of gills coupled between the inlet-barrier-filter compartment and the engine and operable to be in an open state and a closed state, a filter-purge door coupled to the inlet-barrier-filter compartment and operable to be in a closed state and an open state. When the plurality of gills are in the closed state and the filter-purge door is in the open state, air from the filter-purge door flows from the inlet-barrier-filter compartment through the inlet barrier filter.

An aircraft nacelle includes a forward cruise inlet, a forward-cruise-inlet conduit coupled to the forward cruise inlet and operable to supply air from the forward cruise inlet to an engine housed by the aircraft nacelle, an inlet barrier filter, an inlet-barrier-filter compartment coupled to the inlet barrier filter, a plurality of gills coupled between the inlet-barrier-filter compartment and the engine and operable to be in an open state and a closed state, and an adjustable air-diversion door operable to divert air from the forward cruise inlet selectively between the forward-cruise-inlet conduit and the inlet-barrier-filter compartment.

An aircraft nacelle includes a forward cruise inlet, a forward-cruise-inlet conduit coupled to the forward cruise inlet and operable to supply air from the forward cruise inlet to an engine housed by the aircraft nacelle, an inlet barrier filter comprising a filter panel hinged at an end thereof opposite the forward cruise inlet, an inlet-barrier-filter compartment coupled to the inlet barrier filter, and a plurality of gills coupled between the inlet-barrier-filter compartment and the engine and operable to be in an open state and a closed state.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various illustrative embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a Figure may illustrate an illustrative embodiment with multiple features or combinations of features that are not required in one or more other embodiments and thus a figure may disclose one or more embodiments that have fewer features or a different combination of features than the illustrated embodiment. Embodiments may include some but not all the features illustrated in a figure and some embodiments may combine features illustrated in one figure with features illustrated in another figure. Therefore, combinations of features disclosed in the following Detailed Description may not be necessary to practice the teachings in the broadest sense and are instead merely to describe particularly representative examples. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not itself dictate a relationship between the various embodiments and/or configurations discussed.

Referring toFIGS.1A-1B, a tiltrotor aircraft is schematically illustrated and generally designated100. The tiltrotor aircraft100includes a fuselage112and a tail section114including rotatably mounted tail members114a,114bhaving control surfaces operable for horizontal and/or vertical stabilization during forward flight. A wing116is supported by the fuselage112. Located at outboard ends of the wing116are propulsion assemblies118a,118b. The propulsion assembly118aincludes a fixed nacelle120athat houses an engine122and a transmission. In addition, the propulsion assembly118aincludes a pylon assembly124athat is rotatable relative to the fixed nacelle120abetween a generally horizontal orientation, as best seen inFIG.1A, and a generally vertical orientation, as best seen inFIG.1B. The propulsion assembly118aalso includes a proprotor assembly126athat is rotatable relative to the pylon assembly124aresponsive to torque and rotational energy provided by a rotor hub assembly and drive system mechanically coupled to the engine122and the transmission. Similarly, the propulsion assembly118bincludes a fixed nacelle120bthat houses an engine and transmission, a pylon assembly124bthat is rotatable relative to the fixed nacelle120band a proprotor assembly126bthat is rotatable relative to the pylon assembly124bresponsive to torque and rotational energy provided via a rotor hub assembly and drive system mechanically coupled to the engine and transmission housed by the fixed nacelle120b. As used herein, the term “coupled” may include direct or indirect coupling by any means, including moving and/or non-moving mechanical connections.

FIG.1Aillustrates the tiltrotor aircraft100in airplane or forward flight mode, in which the proprotor assemblies126a,126bare rotating in a substantially vertical plane to provide forward thrust enabling the wing116to provide a lifting force responsive to forward airspeed, such that the tiltrotor aircraft100flies much like a conventional propeller-driven aircraft.FIG.1Billustrates the tiltrotor aircraft100in helicopter or vertical takeoff and landing (“VTOL”) flight mode, in which the proprotor assemblies126a,126bare rotating in a substantially horizontal plane to provide a lifting thrust, such that the tiltrotor aircraft100flies much like a conventional helicopter. It should be appreciated that the tiltrotor aircraft100can be operated such that the proprotor assemblies126a,126bare selectively positioned between forward flight mode and VTOL flight mode, which can be referred to as a conversion flight mode. Even though the tiltrotor aircraft10has been described as having one engine in each of the fixed nacelles120a,120b, it should be appreciated by those having ordinary skill in the art that other engine arrangements are possible and are within the scope of the present disclosure including, for example, alternatively or additionally having an engine housed within the fuselage112that provides torque and rotational energy to both of the proprotor assemblies126a,126b.

It should be appreciated that the tiltrotor aircraft100is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. Other aircraft implementations can include hybrid aircraft, tiltwing aircraft, quad tiltrotor aircraft, unmanned aircraft, gyrocopters, airplanes, jets, helicopters, and the like. As such, those of ordinary skill in the art will recognize that systems such as those set forth herein can be integrated into a variety of aircraft configurations. It should be appreciated that even though aircraft are particularly well-suited to implement embodiments of the present disclosure, non-aircraft vehicles and devices can also implement the embodiments, including, but not limited to, automobiles or land-based vehicles. Moreover, even though various features of the disclosed embodiments are described below in reference to the tiltrotor aircraft100, principles thereof are not limited to being employed in such an aircraft.

FIG.2is a partial perspective view of an aircraft nacelle. A nacelle200has formed therein a forward cruise inlet202. The nacelle200may be employed, for example, as the nacelle120a. The forward cruise inlet202serves as an inlet for air to the engine122during cruise operations in which the tiltrotor aircraft100is operating in airplane mode, in which mode the tiltrotor aircraft100is not encountering dust, dirt, or other debris.

The nacelle200also includes an inlet barrier filter204. The inlet barrier filter204provides an alternate air inlet to the engine122, for example, when the tiltrotor aircraft100is in a challenging environment, such as during takeoff and landing in a dusty environment. The inlet barrier filter204is shown as including filter panels206(1)-(4). Air drawn through the inlet barrier filter204is filtered and then passes through a plurality of gills illustrated inFIGS.3-4and into the engine122. In contrast, when the forward cruise inlet202is utilized, air passing therethrough to the engine122does not pass through the plurality of gills. It is thus apparent that the inlet barrier filter204and the forward cruise inlet202are alternative paths for air to reach the engine122.

FIG.3is a cut-away view of the aircraft nacelle ofFIG.1in a first operating mode. InFIG.3, a portion of the nacelle200is illustrated with the filter panels206(1)-(4) removed. Removal of the filter panels206(1)-(4) exposes a plurality of gills302. Also shown is an external surface of a forward-cruise-inlet conduit304through which air may flow to the engine122from the forward cruise inlet202. The plurality of gills302are shown in an open position in order to allow air to flow through the filter panels206(1)-(4) and into an inlet-barrier-filter compartment306. From the inlet-barrier-filter compartment306, air flows through the plurality of gills and to the engine122.

When the plurality of gills302are open as shown inFIG.3, thereby allowing air to flow through the inlet barrier filter204and to the engine122, a path for air to flow from the forward cruise inlet202to the engine122is closed. In contrast, when a path for air to flow from the forward cruise inlet202to the engine122is open, the plurality of gills302are closed as illustrated below inFIG.4. Thus, as discussed above, the two paths for air to reach the engine122operate as alternatives to one another.

FIG.4is a cut-away view of the aircraft nacelle ofFIG.1in a second operating mode. InFIG.4, a portion of the nacelle200is illustrated with the filter panels206(1)-(4) removed. Removal of the filter panels206(1)-(4) exposes the plurality of gills302. Also shown is the external surface of the forward-cruise-inlet conduit304through which air may flow to the engine122from the forward cruise inlet202. The plurality of gills302are shown in a closed position in order to allow air to flow through the filter panels206(1)-(4) and into the inlet-barrier-filter compartment306.

When the plurality of gills302are closed as shown inFIG.4, thereby preventing air from flowing through the inlet barrier filter204and to the engine122, a path for air to flow from the forward cruise inlet202to the engine122is open. A forward-cruise-inlet door402that can be opened and closed to control air flow through the forward cruise inlet202is shown in an open position, which position allows air to flow through the forward cruise inlet202, through the forward-cruise-inlet conduit304, and to the engine122. Those having skill in the art will recognize that the air flow to the engine122via the forward cruise inlet202can be controlled at other locations and by other mechanisms along a flow path therebetween besides the forward-cruise-inlet door402.

FIG.5is a cut-away view of an aircraft nacelle that employs a filter-purge system.FIG.5illustrates a nacelle500that includes filter-purge doors502and504. The plurality of gills302are shown in a closed position, thereby preventing air from flowing through the inlet barrier filter204into the inlet-barrier-filter compartment306. The forward cruise inlet202is open so as to allow air to flow via the forward-cruise-inlet conduit304to the engine122.

If, during operation of the tiltrotor aircraft100in a challenging environment, the inlet barrier filter204becomes completely or partially clogged with dirt, dust, or other debris, the filter-purge doors502,504may be opened in order to reverse air flow through the inlet barrier filter204in order to purge the debris from the inlet barrier filter204. When, for example, the aircraft is in airplane mode, ram air flows into the forward cruise inlet202. When the filter-purge doors502,504are opened, ram air similarly flows into the inlet-barrier-filter compartment306. In such a circumstance, because the plurality of gills302are closed, ram air that flows into the filter-purge doors502,504flows into the inlet-barrier-filter compartment306and outward from the inlet-barrier-filter compartment306through the inlet barrier filter204. As such, the reverse flow of air, for example, through the filter panels206(1)-(4) of the inlet barrier filter204serves to dislodge debris from the inlet barrier filter204.

Although the filter-purge doors502,504are illustrated in being two in number, a single filter-purge door or more than two filter-purge doors may be employed as required by design considerations. In a typical embodiment, the filter-purge doors502,504are arranged so as to be flush with an external surface of the nacelle500when not engaged so as to purge the inlet barrier filter204and to pop up when engaged so as to purge the inlet barrier filter204.

FIGS.6A-Billustrate an aircraft nacelle that employs a filter-purge system.FIGS.6A and6Beach illustrate a nacelle600that includes the forward cruise inlet202. In contrast to the nacelle500, the nacelle600utilizes the forward cruise inlet202to feed both the engine122and to provide reverse air flow through the inlet barrier filter204in order to perform a filter-purge operation.

FIG.6Aillustrates the nacelle600in cruise operation in which a selectively adjustable air-diversion door602in a first state in which all ram air entering the forward cruise inlet202enters the engine122and no ram air entering the forward cruise inlet202enters the inlet-barrier-filter compartment306.FIG.6Billustrates the nacelle600in cruise operation in which the selectively adjustable air-diversion door602is in a second state in which no ram air entering the forward cruise inlet202enters the engine122and all ram air entering the forward cruise inlet202enters the inlet-barrier-filter compartment306and exits the inlet barrier filter204so as to purge debris from the inlet barrier filter204.

InFIG.6B, in the state of the adjustable air-diversion door602shown, the plurality of gills302must be opened to a sufficient degree in order to allow ram air to reach the engine122. If it is not desired to partially open the plurality of gills302during a filter-purge operation in order to feed air to the engine122, the adjustable air-diversion door602could be positioned in an intermediate position between the positions shown between those shown inFIG.6AandFIG.6Bsuch that sufficient air flows to the engine122and, at the same time, sufficient air flows to dislodge debris from the inlet barrier filter204.

FIG.7is a partial perspective view of an aircraft nacelle that employs a filter purge system.FIG.7shows a nacelle700that employs hinged filter panels702(1)-(3). The hinged filter panels702(1)-(3) open at an end opposite the forward cruise inlet202and are operable to open when the tiltrotor aircraft100is in cruise operation in order to force ram air through the filter panels in order to dislodge debris therefrom. The plurality of gills302are shown in a closed position and ram air is fed to the engine122via the forward cruise inlet202and the forward-cruise-inlet conduit304. Although an angle of opening of the hinged filter panels702(1)-(3) is shown to be on the order of 30-45° to illustrate the effective principle of operation, in a typical embodiment, the angle of opening would be substantially less than what is shown.

In a typical embodiment, the hammer effect, in which pressure is turned from an on position to an off position abruptly, may be utilized to further enhance the ability of solutions disclosed herein to dislodge debris from the inlet barrier filter204. Pilot-actuation or flight-control-computer actuation, or a combination of the two, may be employed to achieve inlet-barrier-filter purge operations. In a typical embodiment, a determination that the inlet barrier filter has become clogged may be determined by detection of a pressure differential between the inlet-barrier-filter compartment and the ambient environment near the nacelle. Those having skill in the art will appreciate that features disclosed above relative toFIGS.5-7can be combined with one another in various combinations without departing from the principles set forth herein.

As used herein, the terms connect, connection, connected, in connection with, and connecting may be used to mean in direct connection with. Similarly, the terms couple, coupling, and coupled may be used to mean coupled directly or via one or more elements. Conditional language used herein, such as, among others, can, might, may, e.g., and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include such elements or features.

The terms substantially, approximately, and about are each defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. The extent to which the description may vary will depend on how great a change can be instituted and still have a person of ordinary skill in the art recognized the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding, a numerical value herein that is modified by a word of approximation such as substantially, approximately, and about may vary from the stated value, for example, by 0.1, 0.5, 1, 2, 3, 4, 5, 10, or 15 percent.