Patent Description:
A gas turbine engine typically includes one or more bleed valves to bleed airflow from the compressor section. For example, such bleed valves may bleed airflow from the compressor section at a high pressure compressor or at a low pressure compressor of the gas turbine engine. The bleed valves are opened at operating conditions such as engine start to remove excess airflow from the core flowpath, and also opened during operation for, for example, engine surge avoidance.

One example of such a bleed valve is a low pressure compressor exit bleed valve, which when open allows airflow to bleed from the low compressor section. The bleed valve is an annular ring covering a bleed duct, the bleed duct extending from the compressor flow path. To open or close the bleed valve, the annular ring is moved axially and circumferentially. This axial motion of the valve requires additional axial space around the valve location to accommodate the axial travel of the valve. Thus, placement of flanges and/or other features of the compressor may be limited by the need for this additional axial space.

<CIT> discloses a bypass valve system wherein valve doors move in an axial and radial direction when actuated by circumferential travel of an actuation ring.

According to a first aspect, a bleed system for a gas turbine engine includes a bleed duct having a duct inlet for locating at a flowpath of a gas turbine engine, and a duct outlet for locating outside of the flowpath, the bleed duct extending circumferentially around a central longitudinal axis. A plurality of bleed doors are located at the duct reed outlet and are arrayed along a circumferential length on the bleed duct. Each bleed door includes a first circumferential end, and a second circumferential end. The plurality of bleed doors are arrayed such that when the plurality of bleed doors are in a closed position the first circumferential end is located at the second circumferential end of an adjacent bleed door of the plurality of bleed doors. Each bleed door includes a pivot, such that each bleed door rotates about the pivot from the closed position covering the duct outlet to an opened position for allowing a bleed airflow to pass through the duct outlet. When the plurality of bleed doors are in the opened position, the bleed doors extend from their pivots in a circumferential swirl direction of the bleed airflow through the bleed duct.

Optionally, the bleed system includes a synchronization ring, and a linkage arm extending from the synchronization ring to a bleed door of the plurality of bleed doors such that circumferential movement of the synchronization ring about the central longitudinal axis urges rotation of the bleed door about the pivot between the closed position and the open position.

Optionally, the linkage arm is connected to the bleed door between the pivot and the first circumferential end of the bleed door.

Optionally, the pivot is located at or near the second circumferential end of the bleed door.

Optionally, the first circumferential end of each bleed door of the plurality of bleed doors circumferentially overlaps the second circumferential end of the adjacent bleed door of the plurality of bleed doors.

Optionally, each bleed door of the plurality of bleed doors includes a perimetrical seal to seal the bleed door to the duct outlet when the bleed door is in the closed position.

Optionally, each bleed door of the plurality of bleed doors includes an inner radial surface extending through the duct outlet into the bleed duct when the bleed door is in the closed position.

Optionally, the inner radial surface is profiled to allow for smooth egress of the bleed airflow from the duct outlet.

According to another aspect, a gas turbine engine includes a combustor, a turbine driven by combustion gases output from the combustor, and a compressor driven by the turbine, the compressor including the bleed system described above.

Optionally, the pivot is secured to a fixed structure of the gas turbine engine.

The following descriptions of exemplary embodiments are by way of example only and should not be considered limiting in any way.

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than about five <NUM>: <NUM>. 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 disclosure is applicable to other gas turbine engines including direct drive turbofans.

Referring now to <FIG>, illustrated is a partial cross-section of the low pressure compressor <NUM>. The low pressure compressor includes one or more low compressor rotors <NUM> disposed in a compressor case <NUM> or other static structure. An inner wall <NUM> of the compressor case <NUM> at least partially defines core flowpath C through the low pressure compressor <NUM>. The low pressure compressor <NUM> further includes one or more bleed ducts <NUM> extending outwardly from the core flowpath C to selectably direct bleed airflow <NUM> from the core flowpath C to a location outside of the low pressure compressor <NUM>, such as to the turbine section <NUM> to be utilized for component cooling, or overboard. The bleed duct <NUM> extends from a duct inlet <NUM> at the core flowpath C to a duct outlet <NUM> radially outboard of the core flowpath C. Further, the bleed duct <NUM> has an upstream duct wall <NUM> defining an upstream extent of the bleed duct <NUM> relative to the engine central longitudinal axis A, and a downstream duct wall <NUM> opposite the upstream duct wall <NUM> thereby defining an axial width <NUM> of the bleed duct <NUM>. The upstream duct wall <NUM> and the downstream duct wall <NUM> extend circumferentially about the engine longitudinal axis A. In some embodiments, one or more duct struts <NUM> extend from the upstream duct wall <NUM> to the downstream duct wall <NUM> to provide structural support to the bleed duct <NUM>, and divide the bleed duct <NUM> into a plurality of circumferential bleed duct segments <NUM>, as best shown in <FIG>.

Referring now to <FIG>, <FIG> and <FIG>, illustrated is an embodiment of a bleed door system <NUM>. The bleed door system <NUM> includes a plurality of bleed doors <NUM> arrayed circumferentially about the bleed duct <NUM>. In some embodiments, each bleed door <NUM> of the plurality of bleed doors is located at a corresponding bleed duct segment <NUM> of the plurality of bleed duct segments <NUM>. The plurality of bleed doors <NUM> are located at the duct outlet <NUM>, closing the duct outlet <NUM> when the bleed doors <NUM> are in a closed position as in <FIG>, and allowing bleed airflow <NUM> to pass through the duct outlet <NUM> when the bleed doors <NUM> are in an open position as shown in <FIG>.

Each bleed door <NUM> has an inner door surface <NUM> closed to the duct outlet <NUM> and an outer door surface <NUM> opposite the inner door surface <NUM>. The bleed door <NUM> includes a first circumferential end <NUM> and a second circumferential end <NUM> opposite the first circumferential end <NUM>. The bleed doors <NUM> are circumferentially arrayed such that a first circumferential end <NUM> of a bleed door <NUM> abuts a second circumferential end <NUM> of an adjacent bleed door <NUM>. In some embodiments, the first circumferential end <NUM> includes a lip <NUM>, which overlaps the second circumferential end <NUM> of the adjacent bleed door <NUM>, as shown in <FIG>. In some embodiments, a seal (not shown) extends around a perimeter of the bleed door <NUM> to improve sealing to the duct outlet <NUM> when the bleed doors <NUM> are in the closed position. While in some embodiments, the bleed door <NUM> seals to the duct outlet <NUM>, in other embodiments the adjacent bleed doors <NUM> may seal to each other in addition to or as an alternative to sealing to the duct outlet <NUM>.

The bleed door system <NUM> further includes a synchronization ring <NUM> that is driven circumferentially about the engine central longitudinal axis A, by an actuator (not shown). The synchronization ring <NUM> is operably connected to each of the bleed doors <NUM> such that the circumferential movement of the synchronization ring <NUM> moves the bleed doors <NUM> between the closed position and open position as shown in <FIG> and <FIG>.

The synchronization ring <NUM> is connected to the bleed doors <NUM> by a linkage arm <NUM> extending between the synchronization ring <NUM> and the bleed doors <NUM>. The bleed doors <NUM> each include a pivot <NUM> at which the bleed door <NUM> is rotationally connected to a static structure, such as case <NUM>. In some embodiments the pivot <NUM> is located at or near the second circumferential end <NUM>. The linkage arm <NUM> connects to the bleed door <NUM> between the pivot <NUM> and the first circumferential end <NUM>. In some embodiments, the bleed door <NUM> includes ribs or protrusions <NUM> extending from the outer door surface <NUM> to accommodate the pivot <NUM> and attachment of the linkage arm <NUM>. As shown in <FIG>, circumferential rotation of the synchronization ring <NUM> urges the bleed doors <NUM> to each rotate radially outwardly about their respective pivot <NUM> and move from the closed position to the open position, thereby allowing the bleed airflow <NUM> therethrough.

As shown in <FIG>, the bleed airflow <NUM> in the bleed duct <NUM> has a circumferential component, or swirl. The bleed doors <NUM> are oriented such that when in the opened position, the bleed doors <NUM> extend from the pivot <NUM> in the swirl direction. This orientation reduces flow losses when the bleed doors <NUM> are open. Further, referring again to <FIG>, when the bleed doors <NUM> are closed, the synchronization ring <NUM> is aligned so that maximum mechanical advantage from the corresponding position of the linkage arms <NUM> is applied to the bleed doors <NUM> during high load conditions, thus maintaining closure of the bleed doors <NUM>. Conversely, motion of the linkage arms <NUM> increases in the opening direction when air is required to be dumped quickly.

In some embodiments, such as shown in <FIG> and <FIG>, the inner door surface <NUM> extends at least partially into the bleed duct <NUM>, reducing an effective length of the bleed duct <NUM> from the duct inlet <NUM> to the inner door surface <NUM>. This reduction in effective length increases an effective acoustic frequency of the bleed duct <NUM> consistent with the length reduction when the bleed door <NUM> is in the closed position, as shown in <FIG>. Further, the inner door surface <NUM> may be contoured or profiled to allow smooth egress of the bleed airflow <NUM> when the bleed door <NUM> is in the open position, as shown in <FIG>.

The bleed door system <NUM> configurations illustrated and described herein require less axial space than the typical axially-opening bleed valve configuration and reduces or removes axial design constraints due to the bleed valve. Further, the bleed doors <NUM> may be configured to extend radially into the bleed duct <NUM> to provide frequency tuning solutions to address flowpath resonance issues.

Claim 1:
A bleed system for a gas turbine engine (<NUM>), comprising:
a bleed duct (<NUM>) having a duct inlet (<NUM>) for locating at a flowpath of a gas turbine engine, and a duct outlet (<NUM>) for locating outside of the flowpath, the bleed duct extending circumferentially around a central longitudinal axis;
a plurality of bleed doors (<NUM>) located at the duct outlet and arrayed along a circumferential length on the bleed duct, each bleed door including:
a first circumferential end (<NUM>);
a second circumferential end (<NUM>), the plurality of bleed doors arrayed such that when the plurality of bleed doors are in a closed position the first circumferential end is located at the second circumferential end of an adjacent bleed door of the plurality of bleed doors; and
a pivot (<NUM>), such that each bleed door rotates about the pivot from the closed position covering the duct outlet (<NUM>) to an opened position for allowing a bleed airflow (<NUM>) to pass through the duct outlet;
characterized in that, when the plurality of bleed doors (<NUM>) are in the opened position, the bleed doors extend from their pivots (<NUM>) in a circumferential swirl direction of the bleed airflow (<NUM>) through the bleed duct (<NUM>).