Bleed deflector for a gas turbine

BACKGROUND OF THE INVENTION

The present invention relates to a bleed deflector for use in a gas turbine engine.

Current high pressure compressor bleed discharge designs consist of either a tube or a vaned deflector which directs high temperature engine bleed air into a fan duct. Such an arrangement often leads to structural problems caused by the bleed air plume impacting the inner and outer fan duct walls, exceeding their temperature limits. Typical bleed discharge air is up to 800°F to 1000°F (427-538°C), while fan air is up to 240°F (120°C). Duct material temperature limits are on the order of 300°F to 350°F (149°-177°C).

In the past, a silencer for high velocity gas flow in a gas turbine engine has been proposed. One such silencer is shown in U.S. Patent No. 4,537,277 to Bryce. As shown therein, the Bryce silencer includes a flow passage and a domed perforated plate which terminates the flow passage. The perforated portions of the plate are distributed over the plate so as to direct gas from the passage as a plurality of divergent jets, so that noise is produced with a frequency at maximum intensity in a range of the audible spectrum at which human auditory perception is relatively insensitive. The domed plate portion of the silencer is mounted flush with the inner wall of the bypass duct.

It has been found that devices which utilize flush outlets cause inner duct wall burns because cooler fan air cannot get immediately downstream of the outlet to dilute the hot discharge flow from the device.

Attempts have been made to develop a bleed deflector which avoided the problem of inner duct wall burns. One such attempt is shown in FIGS. 1 and 2. In this bleed deflector, an aerodynamically shaped deflector 10 has outlets 12 in its side walls which separate the bleed air discharge into two lateral plumes 14 and 16. Each of the outlets 12 has discrete holes which can be angled to direct the jets in a desired direction. This deflector however did not work because it was not possible to jet enough flow out of the bleed deflector. Thus, there remains a need for a bleed deflector which adequately discharges the bleed air from a compressor of a gas turbine engine.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention in preferred embodiments at least to provide an improved bleed deflector for use in a gas turbine engine.

It is a further object of the present invention in preferred embodiments at least to provide a bleed deflector which substantially eliminates wall burns in a fan duct.

In accordance with the present invention, a bleed deflector broadly comprises an inlet portion for receiving bleed air, an outlet portion for discharging the bleed air into a duct, and means for positioning said outlet portion above an inner wall of the duct and for creating a linear flow path for the discharge air between the inlet portion and the outlet portion.

Other details of the bleed deflector of the present invention, as well as other advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

<ul id="ul0001" list-style="none" compact="compact"><li>FIG. 1 is a perspective view of a prior art bleed deflector.</li><li>FIG. 2 is a fan duct cross section showing the prior art bleed deflector positioned within a fan duct.</li><li>FIG. 3 is a perspective view of a bleed deflector in accordance with the present invention.</li><li>FIG. 4 is a plan view of the bleed deflector of FIG. 2 installed within a fan duct.</li><li>FIG. 5 is a fan duct cross section showing the bleed deflector of the present invention.</li><li>FIG. 6 is a sectional view of the bleed deflector of FIG. 3 taken along a plane extending from one side to another side of the bleed deflector.</li><li>FIG. 7 is a sectional view of the bleed deflector of FIG. 3 taken along a plane extending from a leading edge of the bleed deflector to a trailing edge of the bleed deflector.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to FIGS. 3 through 7, a bleed deflector 20 in accordance with the present invention is illustrated. The bleed deflector 20 has an inlet portion 22 for receiving bleed air from a compressor stage (not shown) of a gas turbine engine. The bleed deflector 20 further has an outlet portion 24 and a member 26 for positioning the outlet portion 24 above an inner wall 28 of a fan duct 30.

The positioning member 26 is aerodynamically shaped to minimize drag and to allow for a maximum amount of dilution air, generated by the engine fan (not shown), beneath the outlet portion 24. This eliminates contact of the hot bleed gasses with the duct inner wall 28 during low and high power operation of the engine, or should the bleed valve (not shown) leak.

As can be seen from FIGS. 3 - 5, the positioning member 26 comprises a strut having a leading edge 32, a trailing edge 34, and arcuately shaped, non-linear, side surfaces 36 and 38 each extending between the leading edge 32 and the trailing edge 34. Further, the positioning member 26 has a height h sufficient to insure that the plume 27 from the outlet portion 24 does not contact the inner wall 28.

The outlet portion 24 includes a base portion 40 integrally formed with or joined to the upper end of the positioning member 26. The base portion 40 is arcuately curved along its lower surface 42 to further improve the air flow within the duct 30.

The outlet portion 24 further includes a dome shaped perforated top plate 44 through which the bleed air is discharged into the duct 30. The perforated top plate 44 includes a plurality of discrete holes 46. Each hole 46 is sized to prevent the bleed air discharge from contacting the outer wall 48 of the fan duct 30. Further, each hole 46 is not perpendicular to the surface of the perforated top plate 44. Instead, each hole 46 is angled to enhance turning of the exhaust plume 27 in a circumferential direction when looking from the front or rear of the engine. The interior shape of the side surfaces 36 and 38, as shown in FIGS. 6 and 7, is such that the bleed air is fed to all of the holes 46.

The perforated top plate 44 has been found to be useful in diffusing the bleed air as it travels from the inlet portion 22 to the outlet portion 24. The perforated top plate 44 also distributes the hot bleed discharge gasses over an area that produces an optimum plume shape and size.

The bleed deflector of the present invention has particular utility with composite nacelles because such nacelles burn much more easily than metallic nacelles. The bleed deflector of the present invention is quite beneficial during idle times when compressor bleed discharge temperature is quite hot.

It is apparent that there has been provided in accordance with the present invention a bleed deflector for a gas turbine engine which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Therefore, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.