Patent Description:
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.

Rotors in the compressor section can be assembled from a disk that has a series of slots that receive and retain respective rotor blades. Another type of rotor is an integrally bladed rotor, sometimes referred to as a blisk. In an integrally bladed rotor, the disk and blades are formed from a single piece or are welded together as a single piece. As can be appreciated, due to the fabrication, stresses, and other factors, the design of an assembled rotor and the design of an integrally bladed rotor will differ.

Various prior art rotors are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

<CIT> discloses an integrally bladed rotor comprising a monolithic single-piece rotor body that includes a web joining a bore portion and a rim, blades that extend outwardly from the rim, and an arm that extends axially off of the rim, the arm including a cylindrical portion having a seal, a free end of the arm including a radial wall.

The invention is directed to an integrally bladed rotor as defined in independent claim <NUM>.

In a further embodiment the foregoing embodiment, the pocket is formed by the arm, the rim, and the web.

In a further embodiment of any of the foregoing embodiments, the pocket has a flat side.

In a further embodiment of any of the foregoing embodiments, the pocket has a curved side. A gas turbine engine according to an example of the present invention includes a compressor section, a combustor section in communication with the compressor section, and a turbine section in communication with the combustor section. The compressor section has an integrally bladed rotor as described above.

The various features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description.

Alternative engine designs can include an augmentor section (not shown) among other systems or features.

Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, the examples herein are not limited to use with two-spool turbofans and may be applied to other types of turbo machinery, including direct drive engine architectures, three-spool engine architectures, and ground-based turbines.

The engine <NUM> generally includes a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis A relative to an engine static structure <NUM> via several bearing systems <NUM>.

The inner shaft <NUM> is connected to the fan <NUM> through a speed change mechanism, which in 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>.

A combustor <NUM> is arranged between the high pressure compressor <NUM> and the high pressure turbine <NUM>. The mid-turbine frame <NUM> further supports the bearing systems <NUM> in the turbine section <NUM>. The inner shaft <NUM> and the outer shaft <NUM> are concentric and rotate via bearing systems <NUM> about the engine central longitudinal axis A, which is collinear with their longitudinal axes.

The engine <NUM> in one example of a high-bypass geared aircraft engine. 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 direct drive turbofans.

The flight condition of <NUM> Mach and <NUM>,<NUM> ft, with the engine at its best fuel consumption - also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')" - is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point.

In a further example, the fan <NUM> includes less than about <NUM> fan blades. In another non-limiting embodiment, the fan <NUM> includes less than about <NUM> fan blades. Moreover, in one further embodiment the low pressure turbine <NUM> includes no more than about <NUM> turbine rotors. In a further non-limiting example the low pressure turbine <NUM> includes about <NUM> turbine rotors. A ratio between the number of blades of the fan <NUM> and the number of low pressure turbine rotors 46a is between about <NUM> and about <NUM>. The example low pressure turbine <NUM> provides the driving power to rotate the fan section <NUM> and therefore the relationship between the number of turbine rotors in the low pressure turbine <NUM> and the number of blades in the fan section <NUM> discloses an example gas turbine engine <NUM> with increased power transfer efficiency.

<FIG> illustrates selected portions of the compressor section <NUM> of the engine <NUM>. The compressor section <NUM> includes an integrally bladed rotor <NUM>. The integrally bladed rotor <NUM> is formed of a single piece of material. The integrally bladed rotor is a monolithic piece that, in this example, is forged or machined from a solid piece.

The integrally bladed rotor <NUM> in this example is arranged axially downstream from a compressor vane <NUM> that forms a cavity <NUM> between the radially inner portion of the vane <NUM> (e.g., shroud 62a) and a portion of the integrally bladed rotor <NUM>. As will be described in further detail, the cavity <NUM> in this example is relatively radially compact to reduce windage in the cavity <NUM> from the core gas path C.

The integrally bladed rotor <NUM> includes a monolithic rotor body <NUM> that has a bore portion <NUM>, a rim <NUM>, and a web <NUM> that joins the bore portion <NUM> and the rim <NUM>. In this example, the web <NUM> is relatively axially thin in comparison to the bore portion <NUM> and rim <NUM>. However, the web <NUM> could alternatively have another radially connecting structure, such as but not limited to, a relatively thicker web, spokes, or other structure that supports the rim <NUM> relative to the bore portion <NUM>.

A plurality of blades <NUM> extend outwardly from the rim <NUM>. An arm <NUM> extends generally axially off of the rim <NUM>, with a pocket <NUM> on the radially inner side of the arm <NUM>. As shown, the integrally bladed rotor <NUM> in this example has two such pockets <NUM>, one on each axial side of the rotor <NUM>. As can be appreciated, the integrally bladed rotor <NUM> could alternatively have only a single pocket <NUM> on one axial side.

In this example, the pocket <NUM> is formed by a portion of the arm <NUM>, the rim <NUM>, and the web <NUM>. The geometry of the pocket <NUM> can be varied for manufacturability or other purposes, but in some examples the geometry can be selected in accordance with mechanical properties of the integrally bladed rotor <NUM>, such as to tune the geometry to reduce vibration. In one example, the pocket <NUM> includes a flat side 78a and a curved side 78b. In this example, the curved side 76b has a simple curve of constant radius of curvature. In other examples, the curved side 78b can have a compound curvature, with multiple radii of curvature. According to the invention, the straight-line radial depth of the pocket <NUM> is greater than or at least equal to half of the smallest straight-line radial thickness of the arm <NUM>.

The arm <NUM> includes a frustoconical portion 76a that is located between, and joins, a cylindrical portion 76b of the arm <NUM> and the rim <NUM>. According to the invention, the cylindrical portion 76b of the arm <NUM> is radially outboard of the web <NUM>. The forward, free end of the arm <NUM> includes a radial wall 76c that is attached to a neighboring rotor <NUM>. The cylindrical portion 76a of the arm <NUM> also includes at least one knife edge seal (or other type of seal) 76d, which engages the shroud 62a of the vane <NUM> to facilitate sealing the cavity <NUM>.

The extension of the arm <NUM> off of the rim <NUM> facilitates the reduction in the size of the cavity <NUM> such that windage throughout the cavity <NUM> is reduced. For instance, an arm that extends off of a web would provide a much larger cavity that is subject to greater windage. As air passes through such a cavity, windage increases the temperature of the air and the surrounding metal. However, by forming the arm <NUM> off of the rim <NUM> rather than the web <NUM>, the size of the cavity <NUM> can be relatively radially compact. Further, the compactness can be achieved without having pockets inside the cavity <NUM>, which would increase windage. Additionally, forming the arm <NUM> off of the rim <NUM> also provides an opportunity to reduce weight, by the presence of the pocket <NUM> rather than a solid portion in that volume. The reduction in weight can also enhance the thermal response of the integrally bladed rotor <NUM>. The pocket <NUM> may also enhance any air flow inboard of the arm <NUM>, which can facilitate thermal responsiveness of the bore portion <NUM>.

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this invention.

In other words, a system designed according to an embodiment of this invention will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures.

Claim 1:
An integrally bladed rotor (<NUM>) comprising:
a monolithic single-piece rotor body (<NUM>) that includes a bore portion (<NUM>), a rim (<NUM>), a web (<NUM>) joining the bore portion (<NUM>) and the rim (<NUM>), a plurality of blades (<NUM>) that extend outwardly from the rim (<NUM>), an arm (<NUM>) that extends axially off of the rim (<NUM>), and a pocket (<NUM>) on a radially inner side of the arm (<NUM>);
wherein the straight-line radial depth of the pocket (<NUM>) is greater than or at least equal to half of the smallest straight-line radial thickness of the arm (<NUM>), and the arm includes a frusto-conical portion (76a) that is between, and joins, a cylindrical portion (76b) of the arm and the rim (<NUM>), the pocket (<NUM>) being located on a radially inner side of the frusto-conical portion (76a);
wherein the cylindrical portion of the arm (76b) includes at least one seal (76d), and wherein a free end of the arm (<NUM>) includes a radial wall (76c), wherein the cylindrical portion (76b) of the arm (<NUM>) is radially outboard of the web (<NUM>).