Patent Description:
Gas turbine engines, such as those utilized in commercial and military aircraft, include a compressor section that compresses air, a combustor section in which the compressed air is mixed with a fuel and ignited, and a turbine section across which the resultant combustion products are expanded. The expansion of the combustion products drives the turbine section to rotate. As the turbine section is connected to the compressor section via a shaft, the rotation of the turbine section further drives the compressor section to rotate. In some examples, a fan is also connected to the shaft and is driven to rotate via rotation of the turbine as well.

Due to the potential for onboard fires, gas turbine engines include fire suppression systems. One exemplary fire suppression system included in some engines uses a gaseous fire suppressant to flood a compartment when a fire is detected. The fire suppressant is non-flammable gas, such as a noble gas. Increasing the amount of non-flammable suppressant in the compartment, decreases the concentration of oxygen within the compartment. By reducing the percentage of oxygen in the environment to prevent flammable fluid vapors igniting, the fire is extinguished.

Exemplary fire suppression systems are described hereafter. <CIT> describes a thermally actuated venting system which includes a thermally actuated vent for opening a vent outlet in a gas turbine engine associated compartment such as a core engine compartment, a fan compartment, or a pylon compartment. A passive thermal actuator is located in the compartment and the actuator may be operably connected to a hinged door of a vent for opening a vent outlet in the chamber. The actuator may be actuated by a phase change material disposed in a chamber and having a liquid state below a predetermined actuation temperature and a gaseous state above the predetermined actuation temperature. The actuator may include a thermal fuse for closing the hinged door during a fire. The thermal fuse may include at least a portion of piston rod or a cylinder wall of the actuator being made of a fuse material which has a melting point substantially above the predetermined actuation temperature.

<CIT> describes an aircraft engine. The aircraft engine includes a nacelle with an air inlet and an air outlet, a cavity defined within the nacelle, the cavity permitting ambient air to pass through the nacelle from the air inlet to the air outlet, a compressor region defined within the nacelle, the compressor region producing bleed air taken from at least one position between the air inlet and the air outlet, and a precooler disposed within the nacelle. The precooler defines an ambient air passage and a bleed air passage, the ambient air passes through the ambient air passage from an ambient air inlet to an ambient air outlet, the bleed air passes through the bleed air passage from a bleed air inlet to a bleed air outlet, and heat is transferred between the ambient air and the bleed air via heat exchange within the precooler. At least one pressure relief door is disposed within the cavity to create additional engine venting proximate to the air outlet, and a controller operatively connected to the pressure relief door, wherein the controller opens the pressure relief door based on a demand for increased flow of the ambient air through the ambient air passage.

<CIT> describes a core compartment ventilation device for a gas turbine engine is provided. The core compartment ventilation device comprises a fireproof sealing member for substantially sealing a core compartment in a nacelle of the gas turbine engine and a chimney configured to be in fluid communication with the fireproof sealing member. The chimney is for conducting hot air from the core compartment to the external atmosphere via the fireproof sealing member.

<CIT> describes a fire emergency ventilation shut-off system for an aircraft having at least one fire zone. The system includes at least one shut-off valve having an element disposed in an inlet of the fire zone, the valve element being movable between open and closed positions and being normally in the open position to permit air to enter the compartment, and a fuel actuator, operatively coupled to the valve stem, for moving the valve element to the closed position in response to a reduction in engine fuel pressure.

In one aspect of the present invention a gas turbine engine includes an engine core including a compressor, a combustor fluidly connected to the compressor, and a turbine fluidly connected to the combustor, the engine core defining an axis, a core nacelle disposed radially outward of the engine core, a cavity disposed between an inner surface of the core nacelle and an outer surface of the engine core, the cavity including a vent disposed at an aft end, wherein the vent includes at least one flap configured to be maintained in an unrestricted position and in a restricted position, the at least one flap being a normally unrestricted flap, an actuator configured to control the position of the at least one flap, and a controller configured to apply power to the actuator in response to a fire suppression action.

In an embodiment of any of the above embodiments the flap is pivoted radially inward in the restricted position, relative to the unrestricted position.

In an embodiment of any of the above embodiments the flap is pivoted radially outward in the restricted position, relative to the unrestricted position.

In an embodiment of any of the above embodiments the flap is extended axially in the restricted position, relative to the unrestricted position.

In an embodiment of any of the above embodiments the cavity includes a fore inlet configured to receive air from a fan stream, and defines a flowpath from the fore inlet to the vent.

In an embodiment of any of the above embodiments the at least one flap is a plurality of flaps distributed circumferentially intermittent about the vent.

In a second aspect of the present invention a method for suppressing an engine fire in a gas turbine engine comprises initiating a fire suppression action by releasing a fire suppressant into a gas turbine engine core cavity and restricting an aft vent of the gas turbine engine core cavity.

In an embodiment of any of the above embodiments the above method for suppressing an engine fire in a gas turbine engine restricting the aft vent of the gas turbine engine comprises allowing the at least one flap to enter a normally restricted position by mechanically disconnecting an actuator from the at least one flap.

In an embodiment of any of the above embodiments the method for suppressing an engine fire in a gas turbine engine restricting the aft vent of the gas turbine engine comprises causing the at least one flap to enter a restricted position from a normally unrestricted position by applying power to an actuator connected to the at least one flap.

In an embodiment of any of the above embodiments the method for suppressing an engine fire in a gas turbine engine restricting the at least one flap restricts airflow out of the core cavity, thereby decreasing a volume of fire suppressant required to lower a concentration of oxygen in the engine core cavity below an auto ignition level.

Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures, direct drive engines, or any other turbine engine configuration.

The inner shaft <NUM> is connected to the fan <NUM> through a speed change mechanism, which in the exemplary gas turbine engine <NUM> is illustrated as a geared architecture <NUM> to drive the fan <NUM> at a lower speed than the low speed spool <NUM>.

The engine <NUM> in one embodiment of the present invention is a high-bypass geared aircraft engine. The low pressure turbine <NUM> pressure ratio is pressure measured prior to the inlet of low pressure turbine <NUM> as related to the pressure at the outlet of the low pressure turbine <NUM> prior to an exhaust nozzle. The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including but not limited to direct drive turbofans.

"Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]^<NUM> (where °R = K x <NUM>/<NUM>).

The compressor <NUM>, combustor <NUM>, and turbine <NUM> sections define an engine core <NUM> that is contained within a static structure (core nacelle) <NUM>. Defined between the static structure <NUM> and the engine core <NUM> are one or more cavities <NUM> that can be subjected to fire hazards during operation of the gas turbine engine <NUM>. Each of the cavities <NUM> is connected to at least one fire suppressant supply in a corresponding wing or pylon of the aircraft via a nozzle <NUM>. A fire detection system may be attached to the inner wall <NUM>, attached to the engine case <NUM>, or positioned in any other appropriate location. The nozzles <NUM> are configured to disperse the fire suppressant in the case of a detected fire within the cavity <NUM>. At an aft end of the cavity <NUM>, relative to an expected fluid flow through the cavity <NUM>, is a vent <NUM> that allows air or other gasses within the cavity <NUM> to be expelled into an ambient atmosphere.

Current fire suppressant sources (e.g., fluid tanks, or bottles) are sized to overwhelm the vents <NUM>, as well as all other openings within the inlet/ventilation system (e.g. fluid drains and the like) with a sufficient concentration of halon or another similar fire suppressant. Multiple suppressant sources are used and take up a significant volume within the structure of the wing.

In an exemplary embodiment, the majority of the ventilation through the compartment <NUM> comes from the fan airflow B and is expelled through the vent <NUM> at the aft end of the compartment <NUM> via an airflow D. Sufficient airflow is maintained through the compartment <NUM> in order to prevent buildup of flammable fluid vapors and maintain a concentration of flammable vapors significantly below an auto-ignition point. The vent <NUM> is designed to maximize thrust recovery of the flow at cruise conditions. Further, the vent <NUM> is configured to be constricted, or relaxed, via a pivot <NUM>. Restricting the vent <NUM> further enhances the ability of the fire suppressant to reduce the concentration of oxygen within the cavity <NUM>.

When a fire is detected within the cavity <NUM>, an operator (such as a pilot) initiates a fire extinguishing system and pressurized gas within the fire suppressant source is released into the cavity <NUM> through the nozzles <NUM>. The volume of suppressant in a given fire suppressant source overwhelms the existing incoming and exhausting air ventilation flows and maintains a sufficiently low concentration of oxygen for a long enough period of time to extinguish the fire. Absent a restricting vent <NUM>, the fire suppressant is carried out of the compartment <NUM>, along with the incoming ventilation air, as the suppressant is being inserted, and the volume of fire suppressant that must be inserted to affect an oxygen concentration is substantially large.

In order to increase the concentration of suppressant in the core compartment <NUM> and thus reduce the amount of suppressant needed for suppressing a fire, the vent <NUM> includes a constricting vent door configured to be actuated by the actuator <NUM>. The actuator <NUM> is controlled by the same control system as the fire suppressant tanks, and constricts the vent <NUM> upon activation. In some examples, activation of the fire suppressant system, can simultaneously cause power to be provided to the actuator <NUM>, thereby activating the actuator and restricting the vent <NUM>. This configuration is referred to as a normally unrestricted vent, as the vent <NUM> is unrestricted absent an input of power.

With continued reference to <FIG>, <FIG> schematically illustrates an exemplary vent <NUM> including an actuator <NUM> configured to restrict and unrestrict a vent opening <NUM> via the actuation of a flap <NUM>. While in an unrestricted position, the flap <NUM> is maintained flush, or approximately flush, with the nozzle portion <NUM> of the static structure <NUM>. While in restricted position (i.e. when a fire suppression action is occurring), the flap <NUM> is pivoted closer to the engine core <NUM> by the actuator <NUM>, thereby restricting the volume of fluid that can pass through the vent <NUM>. The actuator <NUM> can be any know actuator type, and is not limited to the illustrated linear actuator. Further, in an alternative configuration, the flap <NUM> extends along the axis defined by the engine, rather than pivoting radially inward. In the alternative embodiment, the extension along the axis narrows the vent <NUM> opening <NUM>, and a similar restriction occurs.

With continued reference to <FIG> and <FIG> schematically illustrates another example vent <NUM> including an actuator <NUM> configured to actuate a flap <NUM> of the static structure <NUM>, thereby restricting the opening <NUM>. Unlike the example of <FIG>, the flap <NUM> of <FIG> is the end portion of the static structure <NUM>, and is connected to a remaining portion of the static structure <NUM> via a hinge, or similar attachment. During operation of the fire suppression action, the flap <NUM> is pivoted radially inward, and restricts the vent <NUM> in the same manner as the example of <FIG>.

With reference now to both <FIG>, in both examples, the restricted state of the flap <NUM>, <NUM> does not entirely seal the compartment <NUM> and a gas flow <NUM>, <NUM> is allowed to continue to pass through the compartment <NUM> and out the vent <NUM>, even while restricted. In some limited alternative examples, such as an intermittent flap construction described below, the flap <NUM>, <NUM> can be brought into contact with the engine core <NUM>, without sealing the vent <NUM>. In yet further examples, a construction is used where the restricted state of the flap <NUM>, <NUM> seals the opening <NUM>, <NUM>.

With continued reference to <FIG>, <FIG> schematically illustrates an aft view of the vent <NUM> including multiple flaps <NUM> in a restricted state and multiple flaps <NUM> in an unrestricted state. The circumferentially alternating state is referred to as being circumferentially intermittent. While illustrated as alternating restricted and unrestricted flaps <NUM>, <NUM>, it is appreciated that the circumferential intermittence can be achieved with any intermittent pattern, and alternating every other flap <NUM>, <NUM> is not required. By way of example, every third flap could restrict, every third flap could be left unrestricted, or any other similar intermittent configuration could be used.

With continued reference to <FIG>, <FIG> schematically illustrates a control sequence for suppressing a fire within the cavity <NUM>. Initially a fire is detected in a "Detect Fire" step <NUM>. Once detected, onboard systems notify the pilot and/or other operators of the aircraft of the fire, and the pilot or other operator initiates fire suppression in an "Initiate Fire Suppression" step <NUM>.

Once the fire suppression is initiated, the vent <NUM> is restricted in a "Restrict Vent" step <NUM> and at least one bottle of the fire suppressant is opened to be released into the cavity <NUM> in an "Open Fire Suppressant Bottle" step <NUM>. Both of these steps <NUM>, <NUM> occur simultaneously, or approximately simultaneously in order to ensure that the vent <NUM> is properly restricted when the initial rush of fire suppressant gas enters the cavity <NUM>. In alternative examples, step <NUM> may be sequenced ahead of <NUM> if timing of the actuation is desirable to achieve an optimum outcome.

In some examples, such as the normally unrestricted flaps <NUM>, <NUM>, restricting the vent <NUM> occurs by applying power to the actuator <NUM>, <NUM>, thereby causing the flap <NUM>, <NUM> to become restricted.

Once the flaps <NUM>, <NUM> have entered the restricted position, the fire suppressant is dispersed in a "Disperse Fire Suppressant" step <NUM>. The fire suppressant is dispersed until the source (e.g. a fire suppressant canister) is emptied. By utilizing the restricting flaps <NUM>, <NUM> at the vent <NUM>, the size of the fire suppressant source can be reduced relative to existing systems, thereby allowing for more fire suppressant sources to be incorporated or for a reduction in the weight of the aircraft. Alternatively a higher likelihood of extinguishing the fire may occur by creating a higher concentration of the noble gas in the core compartment for a longer period of time.

While illustrated as two distinct embodiments, it is appreciated that the flaps <NUM>, <NUM> of <FIG> can be utilized in conjunction with each other in a single embodiment. It is also appreciated that the flaps of <NUM>, <NUM> could be configured to be mounted to the core engine and act radially outward to close vent <NUM>. The combined embodiment can be achieved by one of skill in the art using any conventional modification to the disclosed systems.

Claim 1:
A gas turbine engine (<NUM>) comprising:
an engine core (<NUM>) including a compressor (<NUM>), a combustor (<NUM>) fluidly connected to the compressor (<NUM>), and a turbine (<NUM>) fluidly connected to the combustor (<NUM>), the engine core (<NUM>) defining an axis (A);
a core nacelle (<NUM>) disposed radially outward of the engine core (<NUM>);
a cavity disposed between an inner surface of the core nacelle (<NUM>) and an outer surface of the engine core (<NUM>), characterised in that the cavity including a vent (<NUM>) disposed at an aft end;
wherein the vent (<NUM>) includes at least one flap (<NUM>) configured to be maintained in an unrestricted position and in a restricted position, the at least one flap being a normally unrestricted flap;
an actuator (<NUM>) configured to control the position of the at least one flap (<NUM>); and a controller configured to apply power to the actuator (<NUM>) in response to a fire suppression action.