Patent Description:
Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases. The hot gases expanded within the turbine section produce a gas stream across alternating rows of stationary turbine stator vanes and rotating turbine rotor blades produce power.

Internal secondary flow systems transfer cooling air that bypasses the combustor section to a turbine rotor assembly for subsequent distribution to the interior of the rotor blades through an on-board injector. Accelerating the cooling air through a nozzle and swirling the air with the rotation of the turbine rotor, reduces the temperature of the cooling air as it is injected on board the turbine rotor.

Various cast features within the engine are exposed to this air flow downstream of the on-board injector. The rotating air interacts with the cast features which increases air turbulence and the air temperature. The net result is that the air flowing to the interior of the rotor blades may be relatively hotter and thereby relatively less thermally efficient. <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose gas turbine engines with various cover plates.

In one aspect a turbulent air reducer assembly for a gas turbine engine is provided according to claim <NUM>.

A further embodiment of any of the foregoing embodiments of the present invention includes a fastener received within each of the first standoff and the second standoff.

A further embodiment of any of the foregoing embodiments of the present invention includes that the fastener is recessed within each of the first standoff and the second standoff.

A further embodiment of any of the foregoing embodiments of the present invention includes that the fastener retains a first component to a second component.

A further embodiment of any of the foregoing embodiments of the present invention includes that the first component is a cast component.

A further embodiment of any of the foregoing embodiments of the present invention includes that the first component is a tangential on board injector.

A further embodiment of any of the foregoing embodiments of the present invention includes that the second component is a vane support.

A further embodiment of any of the foregoing embodiments of the present invention includes that the windage cover is received within a recess formed in the tangential on-board injector.

An assembly for a gas turbine engine according to one disclosed non-limiting embodiment of the present invention includes an on-board injector with a multiple of recesses; and a turbulent air reducer assembly within each of the multiple of recesses.

A further embodiment of any of the foregoing embodiments of the present invention includes a fastener at least partially within the turbulent air reducer assembly.

A further embodiment of any of the foregoing embodiments of the present invention includes a fastener at least partially recessed within the turbulent air reducer assembly.

A further embodiment of any of the foregoing embodiments of the present invention includes that the fastener attaches the on-board injector to a vane support.

A further embodiment of any of the foregoing embodiments of the present invention includes that the first standoff and the second standoff comprise a flange attached to the windage cover, and a fastener recessed within the respective first and second standoff.

A further embodiment of any of the foregoing embodiments of the present invention includes that the first standoff and the second standoff abut a machined surface on the tangential on-board injector within each of the multiple of recesses, and the tangential on-board injector is a cast component.

In another aspect a method for vibration tuning the claimed turbulent air reducer assembly is provided according to claim <NUM>.

It should be appreciated, however, the following description and drawings are intended to be exemplary in nature and non-limiting.

<FIG> schematically illustrates a portion of a gas turbine engine <NUM>. Although depicted as a turbofan in the disclosed non-limiting embodiment, it should be appreciated that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbo machines.

The gas turbine engine <NUM> generally includes a compressor section <NUM> and a turbine section <NUM> mounted along a rotor shaft <NUM> to form a spool that rotates about an engine longitudinal axis A. In this disclosed non-limiting embodiment, the turbine section <NUM> is a high pressure turbine. A turbine <NUM> with a turbine rotor <NUM> that supports a multiple of rotor blades <NUM> is mounted on the shaft <NUM>. The blades <NUM> receive and expand the combustion products from the combustor <NUM>. Cooling air C flow such as bleed air from the compressor section <NUM> is directed to the turbine section <NUM> through a series of passages.

An on-board injector assembly <NUM> (also shown in <FIG>) which, in this disclosed non-limiting embodiment, is a tangential on-board injector (TOBI). The on-board injector assembly <NUM> surrounds the engine longitudinal axis A and directs the cooling air C toward the turbine rotor <NUM> for cooling. A cover plate <NUM> separates the on-board injector assembly <NUM> and the turbine rotor <NUM>. A multiple of cover plate apertures <NUM> are provided in the cover plate <NUM> to direct cooling air C from the on-board injector assembly <NUM> into the turbine rotor <NUM>, thence into the rotor blades <NUM>.

The on-board injector assembly <NUM> generally includes an on-board injector <NUM> with a multiple of recesses <NUM>, and a turbulent air reducer assembly <NUM> within each of the multiple of recesses <NUM> (also shown in <FIG>). The on-board injector <NUM> is typically a cast component with the multiple of recesses <NUM> cast therein. Tolerances typical of castings need to be accommodated by the turbulent air reducer assembly <NUM> which is mounted thereto. In one embodiment, the on-board injector <NUM> is a circular cast component with sixteen (<NUM>) recesses <NUM>. Each of the multiple of recesses <NUM> includes an aperture <NUM> through a machined surface <NUM> (<FIG>).

The on-board injector <NUM> is attached to a vane support <NUM> with fasteners <NUM> that are received within, and partially recessed, within a turbulent air reducer assembly <NUM>. Turbulent air reducer assemblies <NUM> create a smoother overall series of surfaces for rotating air flow F (<FIG>) to pass thereby than if just the on-board injector <NUM> is exposed. The turbulent air reducer assembly <NUM> provides a smoother series of surfaces that reduce air turbulence and temperature. This therefore increases efficiency of the turbine section <NUM> with negligible vibratory response.

The turbulent air reducer assembly <NUM> includes a first standoff <NUM>, a second standoff <NUM>, and a windage cover <NUM> attached to the first standoff <NUM> and the second standoff <NUM> (also shown in <FIG>). The windage cover <NUM> is tuned to a particular vibration response via vibe tune features <NUM> (<FIG>). The first standoff <NUM> and the second standoff <NUM> are cylindrical members to receive the fasteners <NUM> that attach the on-board injector <NUM> to the vane support <NUM>. The first standoff <NUM> and the second standoff <NUM> abut the machined surface <NUM>.

With reference to <FIG>, in one embodiment, the first standoff <NUM> and the second standoff <NUM> each include a respective flange <NUM> that is attached to an aft side (directed toward the aft end of the engine with respect to the engine longitudinal axis A) of the windage cover <NUM> via, for example, welding. The vibe tune features <NUM> may be located on a forward side (<FIG>; directed toward the front end of the engine with respect to the engine longitudinal axis A) of the windage cover <NUM>.

With reference to <FIG>, the vibe tune features <NUM> are utilized to tune the turbulent air reducer assembly <NUM> such that when the turbulent air reducer assembly <NUM> is located within each of the multiple of recesses <NUM>, the turbulent air reducer assembly <NUM> has a negligible vibratory response. The vibe tune features <NUM> may be manufactured with standard circular machine tools which have centers W that are located outside the outer periphery of the windage cover <NUM>. In one example, the windage cover <NUM> is between <NUM> - <NUM> inches (about <NUM>-<NUM>), more specifically, <NUM> inches (about <NUM>) thick sheet stock with vibe tune features machined down to between <NUM>-<NUM> inches (about <NUM>-<NUM>), and more particularly, <NUM> inches (about <NUM>) thick.

With reference to <FIG>, the vibration issues and corrective action are represented graphically in what is commonly known in industry as a Campbell, resonance, or interference diagram <NUM>. An engine rotor speed is plotted versus frequency. The operating speed range of the turbine <NUM> is defined as the speed range between idle (<NUM>) and maximum speeds (<NUM>).

In the design phase, the natural frequencies of the subject part of interest are determined typically by finite element analysis. These natural frequencies for each mode are plotted as horizontal lines in the diagram (<NUM>, <NUM>, <NUM>). The slope or decrease in frequency of the lines (<NUM>, <NUM>, <NUM>) with increasing speed is the result of higher operating temperatures at higher speeds. The diagonal line (<NUM>) represents the frequency of a vibratory excitation source often caused by a periodic pressure disturbance or pulsation impinging on the part of interest. A common example in turbo-machinery are the blades on a rotor which are an excitation source for the adjacent stationary vanes and vice versa. In this case, the pressure pulses exciting the windage cover <NUM> are caused by a set of the uniformly spaced cover plate apertures <NUM> (<FIG>). Because the excitation source is located on the rotor <NUM>, the frequency of the excitation is linearly proportional to the speed of the rotor <NUM>. Resonance occurs where the natural frequencies of the turbulent air reducer assembly <NUM> match that of the excitation source (<NUM>, <NUM>, and <NUM>).

In the resonance condition, when there is little to no damping, the vibratory stresses in the turbulent air reducer assembly <NUM> can reach levels in high cycle fatigue (HCF), potentially resulting in cracking or fracture. To avoid this, the turbulent air reducer assembly <NUM> is tuned by raising or lowering the natural frequencies to avoid resonances in the operating range of the engine (<NUM>). In this example, the first mode frequency (<NUM>) has been tuned to place the resonance (<NUM>) below idle where the engine spends minimal exposure time. Similarly, the third mode frequency (<NUM>) has been tuned to place the resonance (<NUM>) above maximum rotor speed, where the engine does not operate. However, the second mode frequency (<NUM>) in the example has a resonance (<NUM>) in the operating range and is therefore at risk of HCF damage unless it is tuned.

The natural frequency is proportional to the square root of the stiffness over mass. Tuning is accomplished by removing overhung mass to raise frequency. In the case of weight efficiency it is often more desirable to remove mass rather than to add material for stiffness. Tuning of the windage cover <NUM> is performed by removal of mass near the free edges of the windage cover in order to raise frequencies and, optionally, by removing mass in places where vibratory deflection is predicted. By reducing mass in specific places where motion will occur, the resonant frequencies can be significantly changed, more so than by just changing the mass of the entire part.

With reference to <FIG>, the vibe tune features <NUM> are determined so that the turbulent air reducer assembly <NUM> is tuned to provide a desired particular vibration response from the turbine rotor. A method <NUM> is illustrated for the tuning process during the design phase to provide the desired particular vibration response.

The natural frequencies of the turbulent air reducer assembly <NUM> are calculated (step <NUM>) then plotted (step <NUM>) on the resonance diagram (<FIG>). The results are then interrogated to determine if there are any resonance crossings (step <NUM>) in the operating range (<NUM>; <FIG>). If not, the design is acceptable (step <NUM>). If there are resonance crossings in the operating range ((step <NUM>)<NUM>; <FIG>) an iteration process (step <NUM>) is used to modify the geometry and re-calculate the frequencies and resonance crossings until the design is acceptable. This iteration process can be done by inspecting the mode shapes that are unique to each frequency to determine where changes to stiffness or mass should be made. The process can also be automated to optimize the design by reducing or trying to equalize the modal strain energy in the analytical model.

With reference to <FIG>, another embodiment of the turbulent air reducer assembly 64A includes a windage cover 74A with a radiused edge <NUM>. The radiused edge <NUM> is directed toward the first standoff <NUM> and the second standoff <NUM> which include segmented flanges <NUM> to accommodate the radiused edge <NUM>. The segmented flanges <NUM> are aligned with the radiused edge <NUM> so as to not extend therefrom.

With reference to <FIG>, another embodiment of the turbulent air reducer assembly 64B includes a windage cover 74B with an aft side <NUM> and U- shaped ends <NUM>, <NUM> which include respective forward side <NUM>, <NUM> with apertures <NUM>, <NUM> that match apertures <NUM>, <NUM> in the aft side <NUM> along axes <NUM>, <NUM> to receive the fasteners <NUM>.

Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

It should be appreciated that relative positional terms such as "forward," "aft," "upper," "lower," "above," "below," and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be appreciated that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

Claim 1:
A turbulent air reducer assembly (<NUM>) for a gas turbine engine (<NUM>) comprising a turbine rotor (<NUM>), a vane support (<NUM>), an on-board injector (<NUM>) with a multiple of recesses (<NUM>) mounted to the vane support by fasteners (<NUM>) received within turbulent air reducer assemblies (<NUM>) located in the recesses, the turbulent air reducer assembly (<NUM>) comprising:
a first standoff (<NUM>);
a second standoff (<NUM>); and
a windage cover (<NUM>) attached to the first standoff (<NUM>) and the second standoff (<NUM>), characterised by
the windage cover (<NUM>) being tuned for a particular vibration response related to a rotation of the turbine rotor (<NUM>), wherein the tuning is by removing mass near a free edge of the windage cover (<NUM>) by thinning a semi-circular area (<NUM>) of the windage cover (<NUM>).