Patent Description:
During operation of an aircraft, atmospheric conditions may lead to the formation of ice on the surfaces of the aircraft. Ice formation on aircraft surfaces, such as on the inlet of a gas turbine engine nacelle, is undesirable and can lead to potentially compromised flying conditions. For example, the formation and accretion of ice on aircraft surfaces may adversely affect the performance of the aircraft by altering the shape of various aerodynamic surfaces of the aircraft. Further, ice accretion on the nacelle inlet surfaces of a gas turbine engine may detach and be drawn through the engine, resulting in the potential for damage to the engine.

To address the above concerns, aircraft may include anti-icing systems to prevent ice formation and accretion on, or to remove ice from, aircraft surfaces. One method of implementing such anti-icing systems is to direct heated gases from the gas turbine engine (e.g., engine bleed air) to interior or exterior surfaces of the aircraft, thereby increasing the temperature of the targeted surfaces. These anti-icing systems may use a double duct configuration to transmit heated gases from the gas turbine engine to the targeted aircraft surface, thereby minimizing the risk of damage to aircraft components (e.g., the acoustic composite structure defining an inner wall of a nacelle inlet) as a result of a ruptured duct.

Although risk of damage may be minimized, an undetected leak may result in damage if left unaddressed. In this regard, an undetected leak in the anti-icing air duct may result in permanent nacelle component damage, airplane delays, and/or flight cancellations.

<CIT> relates to anti-ice systems used in aircraft nacelles that surround gas turbine engines.

<CIT> relates to non-resettable, overtemperature sensing devices for indicating when a predetermined temperature limit has been reached in a fluid conduit.

According to a first aspect of the invention, an inlet cowl is as claimed in claim <NUM>.

According to another aspect of the invention, a method for installing an overtemperature indication assembly is as claimed in claim <NUM>.

Various embodiments of the invention are set out in the dependent claims.

The following detailed description of various embodiments herein refers to the accompanying drawings, which show various embodiments by way of illustration.

Referring to <FIG> and <FIG>, an aircraft <NUM> includes a gas turbine engine <NUM> mounted to, for example, a wing <NUM> of the aircraft <NUM>. The gas turbine engine <NUM> includes a nacelle <NUM> defining a housing of the gas turbine engine <NUM> about a longitudinal axis <NUM>. The longitudinal axis <NUM> extends through the center of the gas turbine engine <NUM> between a forward end <NUM> and an aft end <NUM> of the gas turbine engine <NUM>. The gas turbine engine <NUM> generally includes a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. The nacelle <NUM> includes an inlet cowl <NUM>. The inlet cowl <NUM> comprises an inlet surface <NUM> for directing an air flow <NUM> toward the fan section <NUM> and through an inlet section <NUM>. Because the inlet surface <NUM> is located at the forward end <NUM>, and therefore not heated directly by the gas turbine engine <NUM>, the inlet surface <NUM> is prone to the accumulation of ice, especially along a forward lip surface <NUM> (i.e., the leading edge of the nacelle <NUM>).

The inlet cowl <NUM> of the nacelle <NUM> includes a forward bulkhead <NUM> and an aft bulkhead <NUM>, both of which are annularly arranged about the longitudinal axis <NUM>. The inlet cowl <NUM> comprises a forward plenum <NUM> and an aft plenum <NUM>. The forward plenum <NUM> is defined axially in the inlet cowl <NUM> between the forward lip surface <NUM> and the forward bulkhead <NUM> and radially between a radially inner wall <NUM> of the inlet cowl <NUM> and a radially outer wall <NUM> of the inlet cowl <NUM>. The aft plenum <NUM> is defined axially in the inlet cowl <NUM> between the forward bulkhead <NUM> and the aft bulkhead <NUM> and radially between the radially inner wall <NUM> of the inlet cowl <NUM> and the radially outer wall <NUM> of the inlet cowl <NUM>. The forward plenum <NUM> is configured to receive a heated gas that flows through the forward plenum <NUM> to perform the anti-icing function. The heated gas is directed to the forward plenum <NUM> via a fluid conduit <NUM> configured to bleed the heated gas from the compressor section <NUM>. The fluid conduit <NUM> extends from a tap <NUM> at the compressor section <NUM> and extends to a duct system <NUM> that extends through the aft plenum <NUM> from the aft bulkhead <NUM> to the forward bulkhead <NUM>.

In various embodiments, the duct system <NUM> may comprise a double-walled duct. In various embodiments, an anti-icing system <NUM> is configured to deliver the heated gas (e.g., hot air bled from the compressor section <NUM> of the gas turbine engine <NUM>) to the forward plenum <NUM> to prevent the formation of ice on the forward lip surface <NUM>.

The nacelle <NUM> comprises a detection system <NUM> coupled to the inlet cowl <NUM>. The detection system <NUM> is configured to provide a physical indicator in response to a temperature in the aft plenum <NUM> exceeding a temperature threshold. In this regard, the detection system <NUM> may be configured to be in a retracted state during normal operation of the gas turbine engine <NUM> and in a deployed state in response to being activated (i.e., in response to the aft plenum <NUM> exceeding the temperature threshold). In various embodiments, the detection system <NUM> may be disposed on the radially outer wall <NUM> of the inlet cowl <NUM>. However, the present disclosure is not limited in this regard. For example, the detection system <NUM> may be disposed on the aft bulkhead <NUM> in a location that would be visible during maintenance. In various embodiments. the detection system <NUM> is disposed proximal the fluid conduit <NUM> extending through the aft plenum <NUM>. In various embodiments, a portion of the detection system <NUM> extends into the aft plenum <NUM> as described further herein.

Referring now to <FIG>, a cross-sectional view of a partition of the anti-icing system <NUM> along section line A-A from <FIG> is illustrated, in accordance with various embodiments. The anti-icing system <NUM> further comprises the detection system <NUM>. The detection system <NUM> includes an over-temperature indication assembly <NUM>. The overtemperature indication assembly <NUM> comprises a housing <NUM>, a plunger <NUM>, a biasing mechanism <NUM>, and a thermally sensitive valve <NUM>.

In various embodiments, the housing <NUM> is coupled to the radially outer wall <NUM> of the inlet cowl <NUM>. In various embodiments, the housing <NUM> is bonded to (e.g., via an adhesive or the like), or mechanically fastened to (e.g., via nut plates, rivets, etc.) the radially outer wall <NUM>. In various embodiments, the housing <NUM> comprises an elongated portion <NUM> extending radially inward (i.e., as defined relative to the longitudinal axis <NUM> from <FIG>) from a flange <NUM> to a radially inner end <NUM>. The elongated portion <NUM> extends through an aperture <NUM> in the radially outer wall <NUM> of the inlet cowl <NUM>. The radially inner end <NUM> is disposed proximate the fluid conduit <NUM> disposed in the aft plenum <NUM>. "Proximate", as referred to herein is within a "zone" in the aft plenum <NUM>. The zone is defined as being between -<NUM> degrees and <NUM> degrees (i.e., circumferentially) of a line <NUM> extending in a radial direction from the longitudinal axis <NUM> from <FIG>, through a centerline <NUM> of the fluid conduit <NUM> and swept axially along the centerline <NUM> of the fluid conduit <NUM>. Thus, the radially inner end is disposed as close to the fluid conduit <NUM>, in accordance with various embodiments.

The housing <NUM> further comprises a blind recess disposed in the flange <NUM> and extending radially inward to the radially inner end <NUM> of the housing. In various embodiments, the plunger <NUM> comprises a plunger head <NUM> and a rod <NUM> extending from the plunger head <NUM> to the thermally sensitive valve <NUM> disposed adjacent to the radially inner end <NUM>. In various embodiments, the plunger <NUM> further comprises a flange <NUM> and a stop <NUM>. The flange <NUM> may extend radially outward (i.e., radially outward in a radial direction defined from a centerline of the rod <NUM>) from the rod <NUM>. The stop <NUM> may be spaced apart axially (i.e., axially along an axis defined by the rod <NUM>) from the flange). The biasing mechanism <NUM> may be disposed axially between the stop <NUM> and the flange.

In various embodiments, the plunger head <NUM> and the flange <NUM> may add minimal, or negligible drag impact to the inlet cowl <NUM> of the nacelle <NUM>.

In various embodiments, the biasing mechanism <NUM> may be a spring <NUM> (e.g., a compression spring, a torsion spring, a tension spring, etc.). Although illustrated in a compression spring configuration, the present disclosure is not limited in this regard. For example, various biasing mechanisms can be envisioned that would bias the plunger <NUM> in a radially outward (i.e., radially outward from the longitudinal axis <NUM>) direction and be within the scope of this disclosure.

In various embodiments, the thermally sensitive valve <NUM> is disposed adjacent to the radially inner end <NUM> of the housing <NUM>. In this regard, the thermally sensitive valve <NUM> is disposed proximate the fluid conduit <NUM>. In various embodiments, the thermally sensitive valve <NUM> can be a simple insert configured to be disposed in the cavity <NUM> of the housing <NUM>. The simple insert may be made of a metal that melts at a desired temperature (e.g., a threshold temperature). The simple insert may be made of eutectic or fusible alloys with low melting points, including alloys of lead, bismuth, and tin, and commonly known by names like Wood's Metal, Rose Metal, and Lipowitz's Alloy. Such metals are used in fire sprinkler valves, preventing pressurized water from exiting a pipe until triggered by heat, at which time the alloy softens sufficiently to release the plunger <NUM>.

Thus, in response to being exposed to a temperature above a threshold temperature (e.g., during a leakage event of fluid conduit <NUM>), the thermally sensitive valve <NUM> is configured to melt. In response to the thermally sensitive valve <NUM> melting, the rod <NUM> of the plunger <NUM> may be decoupled from the thermally sensitive valve <NUM>. In this regard, the biasing mechanism <NUM> is configured to transition the plunger <NUM> from a retracted state (e.g., <FIG>) to a deployed state (e.g., <FIG>). In various embodiments, the plunger <NUM> may be configured in a manner to ensure that the plunger <NUM> is visible during a crew walkaround or during a scheduled maintenance in accordance with various embodiments. In this regard, the detection system <NUM> is configured to deploy in response to a hot air duct leak from the fluid conduit <NUM> in the aft plenum <NUM> of the inlet cowl <NUM>. In response to deploying, the detection system <NUM> is configured to provide an indicator (e.g., the deployed plunger as shown in <FIG>) for indication during a crew walkaround or a during scheduled maintenance.

In various embodiments, the design of the detection system <NUM> from <FIG> allows for a retrofitting process on typical inlet cowls. For example, a retrofitting process <NUM> for retrofitting a detection system <NUM> onto an inlet cowl <NUM> from <FIG> is illustrated in <FIG> in accordance with various embodiments. The retrofitting process <NUM> comprises drilling an aperture through a wall (e.g., radially outer wall <NUM> or aft bulkhead <NUM>) of an inlet cowl <NUM> of a nacelle <NUM> (step <NUM>). In response to drilling the aperture, an external environment of the inlet cowl <NUM> may be temporarily fluidly coupled to an aft plenum <NUM> of the inlet cowl <NUM>.

In various embodiments, the retrofitting process <NUM> further comprises coupling an over-temperature indication assembly <NUM> to the wall (e.g., radially outer wall <NUM> or aft bulkhead <NUM>) (step <NUM>). In various embodiments, coupling the over-temperature indication assembly <NUM> to the wall may result in a portion of a housing for the overtemperature indication assembly <NUM> to be disposed proximate a fluid conduit disposed through the aft plenum <NUM>. The fluid conduit may be a component within an anti-icing system <NUM> as described previously herein.

Claim 1:
An inlet cowl (<NUM>) for a nacelle for a gas turbine engine (<NUM>) having a longitudinal axis (<NUM>), the inlet cowl (<NUM>) comprising:
a forward bulkhead (<NUM>) annularly arranged about the longitudinal axis (<NUM>);
an aft bulkhead (<NUM>) annularly arranged about the longitudinal axis (<NUM>) and spaced apart axially aft of the forward bulkhead (<NUM>);
an annular structure having a radially inner wall (<NUM>) spaced apart from a radially outer wall (<NUM>); and
a fluid conduit (<NUM>) extending axially through an aft plenum (<NUM>) defined axially between the aft bulkhead (<NUM>) and the forward bulkhead (<NUM>), the aft plenum (<NUM>) defined radially between the radially inner wall (<NUM>) and the radially outer wall (<NUM>),
characterised in that:
the inlet cowl (<NUM>) further comprises an over-temperature indication assembly (<NUM>) coupled to the radially outer wall (<NUM>) and/or the aft bulkhead (<NUM>), the overtemperature indication assembly (<NUM>) configured to transition from a retracted state to a deployed state in response to a portion of the over-temperature indication assembly (<NUM>) exceeding a temperature threshold.