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.

Within the compressor and turbine portions of the gas turbine engine are multiple rotors constructed together as a rotor assembly. The rotors within any given rotor assembly are spaced apart using classified spacers (i.e. multiple spacers having distinct classes of thickness) in order to achieve a desired axial length of the compressor or turbine rotor assembly. The classified spacers include varying average axial thicknesses and varying out of square angles due to manufacturing variations. The varying thicknesses and angles either mitigate rotor stack angles or contribute to rotor stack angles depending on the as-manufactured tolerances of the specific engine in which the classified spacers are included.

<CIT> discloses a prior art multi-ring spacer according to the preamble of claim <NUM>, and a prior art method for assembling a gas turbine engine according to the preamble of claim <NUM>.

<CIT> discloses a prior art method of balancing a spool of a gas turbine engine.

According to a first aspect of the present invention, there is provided a multi-ring spacer as set forth in claim <NUM>.

In another example of any of the above described multi-ring spacers each of the first ring and the second ring have an identical average axial length, relative to a shared axis.

In another example of any of the above described multi-ring spacers each of the first ring and the second ring have distinct average axial lengths.

In another example of any of the above described multi-ring spacers the first first kink angle has a first grade, the second kink angle has a second grade, and the first grade and the second grade are identical.

In another example of any of the above described multi-ring spacers the first kink angle has a first grade, the second kink angle has a second grade, and the first grade and the second grade are different.

According to a further aspect of the present invention, there is provided a method for assembling a gas turbine engine as set forth in claim <NUM>.

In another example of the above described method for assembling a gas turbine engine the first and second co-rotating components include at least one rotor stack assembly.

In another example of any of the above described methods for assembling a gas turbine engine the first and second co-rotating components include two co-rotating rotor stack assemblies.

In another example of any of the above described methods for assembling a gas turbine engine the first ring and the second ring are identical.

In another example of any of the above described methods for assembling a gas turbine engine grades of the first kink angle and the second kink angle are distinct.

With continued reference to <FIG>, <FIG> schematically illustrates a partial rotor stack assembly <NUM> including a rotor stack assembly spacer <NUM> and a corresponding rotor <NUM> in the rotor stack assembly <NUM>. The rotor <NUM> includes a rotor arm <NUM> that extends axially (relative to an engine <NUM> axis). The rotor arm <NUM> is sealed to a corresponding rotor assembly arm <NUM> via contact seals <NUM>. In order to properly position the rotor <NUM> axially, and to compensate for any out of square angle included within the as-manufactured engine, the rotor stack assembly spacer <NUM> is positioned between facing surfaces of the rotor assembly arm <NUM> and the rotor arm <NUM>. As used herein, as-manufactured refers to the actual manufactured dimensions of the engine components. In contrast "nominal" refers to the designed specifications of the engine components and does not account for tolerances or other manufacturing variations that may impact the as-manufactured dimensions.

Existing systems utilize individual spacer rings that are manufactured to a nominal design and then measured to determine the as manufactured average thickness and out of square angle of the spacer. The measured as manufactured dimensions are then used to classify (i.e. categorize) the spacers. When a new engine is constructed, the as manufactured engine is measured and a "best fit" spacer is selected from the classified spacers. The best fit spacer is the spacer that best matches the out of square angle and spacing requirements of the as-manufactured rotor assembly.

With continued reference to <FIG>, <FIG> schematically illustrates a zoomed in view of the spacer <NUM> according to one arrangement outside of the wording of the claims. A nominal spacer <NUM> (i.e. a spacer with no variation from the design specification) would include surfaces <NUM>, <NUM> aligned with the radius of the engine. The surfaces <NUM>, <NUM> aligned with the radius of the engine are normal to the axis of the engine. The normality of the surface, relative to the axis of the engine is referred to as being square with the engine. Due to the manufacturing variance, however, the slot for including the spacer includes an angled surface <NUM> that is out of square with the axis of the engine. The angle by which the surface <NUM>, <NUM> is out of square is referred to herein as the "kink". The particular grade of the kink is highly exaggerated in the illustration to demonstrate the concept. In one practical example, the grade kink can be within the range of <NUM> inches to <NUM> inches (<NUM>) across the face such that the axially longest portion is less than or equal to <NUM> inches (<NUM>) longer than the axially shortest portion. The spacer <NUM> in the illustrated example utilizes two spacer rings, with the rings being able to be rotated relative to each other during installation. Rotating the rings relative to each other alters the kink of the combined spacer <NUM>, allowing any spacer <NUM> to be precisely matched to a kink of an as-manufactured engine without requiring a best fit match.

With continued reference to <FIG> and <FIG>, and with like numerals indicating like elements, <FIG> illustrate exemplary rings that can be used to create the multi-ring spacer <NUM> of <FIG> and <FIG> illustrates a nominal ring <NUM>, with <FIG> illustrating an out of square ring <NUM>. The nominal ring <NUM> has a uniform axial thickness <NUM>, and each axial facing surface <NUM>, <NUM> of the nominal ring is normal to the axis <NUM>. In contrast to the nominal ring <NUM>, the out of square ring <NUM> includes a varying thickness <NUM>. The out of square ring <NUM> also includes an out of square surface <NUM> with the surface <NUM> having a kink angle <NUM> relative to the axis <NUM>. The kink angle <NUM> is oblique to the axis <NUM>, and is the result of the varying thickness <NUM>.

By pairing the nominal ring <NUM> with the out of square ring <NUM>, a two ring spacer is created that allows an average thickness to be controlled by selecting a desired nominal ring, and the average kink angle to be controlled by the out of square ring <NUM>.

With continued reference to <FIG> illustrates a further example rotor spacer <NUM>. <FIG> illustrates an axial view of the spacer <NUM>. The rotor spacer <NUM> includes two rings <NUM>, <NUM> each of which includes an out of square surface <NUM>, with the out of square surfaces <NUM> facing each other. In the example of <FIG>, the rings <NUM>, <NUM> are identical. In addition, each ring <NUM>, <NUM> includes a clocked position. In some examples, the clocked position can be indicated by a surface mark. In other examples, the clocked position is indicated by an indent, or other physical structure on each of the rings <NUM>, <NUM>. When the clocked positions are offset by <NUM> degrees, the total kink angle of the spacer <NUM> is minimized. In an example, such as <FIG>, where the out of square surfaces are at identical angles, the total kink angle while <NUM> degrees offset is zero. The rotation of one ring relative to the other ring is referred to as the angular offset <NUM>, <NUM>', <NUM>''. In contrast, when the clocking positions <NUM> of the rings <NUM>, <NUM> are aligned (e.g. have a zero degree angular offset), the kink angle is maximized and is a sum total of the kink angle of each ring <NUM>, <NUM>. Rotating the rings <NUM>, <NUM> relative to each other does not alter the average thickness of the spacer <NUM>, allowing the axial length that will be compensated for by the spacer <NUM> to remain fixed.

In another example, illustrated in <FIG>, the rings <NUM>, <NUM> are not identical, and the out of square surfaces <NUM> have different kink angles. In such an example, the range of possible kink angles can be changed by selecting a second ring <NUM> surface <NUM> with a desired kink angle, and the spacer itself is fine-tuned by rotating the rings <NUM>, <NUM> relative to each other. As with the other examples, the maximum kink angle occurs when the clocking positions have an angular offset of <NUM> degrees.

According to the invention, the axial thickness of the multi-ring spacer is further tuned by inclusion of an additional nominal thickness spacer ring, such as the ring <NUM> illustrated in <FIG>. In such an example, the kink angle is controlled by.

the angular offset of the out of square rings, and the axial thickness of the spacer is the sum of the average axial length of the out of square rings and the axial length of the nominal ring.

While described herein with specific regards to a rotor stack spacer, it should be appreciated that the axial spacer can be applied in alternative positions within the gas turbine engine where two co-rotating components are interfaced.

With continued reference to the examples disclosed in <FIG>, an exemplary method for assembling a gas turbine engine includes initially installing a plurality of rotor stacks and defining a gap between a first rotor stack and a second rotor stack in the plurality of stacks. Measuring an average axial length of the gap and measuring an out of square angle of the gap. Once the axial length and out of square angle have been measured, a multi-ring rotor stack spacer is selected, and the out of square rings of the multi-ring spacer are angularly offset to match the kink angle of the measured gap kink angle. According to the invention, a third nominal ring is added to increase the axial length of the multi-ring spacer.

Claim 1:
A multi-ring spacer (<NUM>) for co-rotating components of a gas turbine engine, the multi-ring spacer (<NUM>) comprising:
a first ring (<NUM>; <NUM>) defining an axis, the first ring (<NUM>; <NUM>) having a first axially facing out of square surface (<NUM>; <NUM>) having a first kink angle relative to the axis and a first clocking position (<NUM>);
a second ring (<NUM>; <NUM>) coaxial with the first ring (<NUM>; <NUM>) and having a second axially facing out of square surface (<NUM>; <NUM>) having a second kink angle relative to the axis and a second clocking position (<NUM>), the first axially facing out of square surface (<NUM>; <NUM>) facing the second axially facing out of square surface (<NUM>; <NUM>);
wherein the first ring (<NUM>; <NUM>) and the second ring (<NUM>; <NUM>) are rotatable relative one another to define an angular deviation, a total kink angle of the multi ring spacer (<NUM>) is dependent on an angular deviation of the second ring's clocking position (<NUM>) relative to the first ring's clocking position (<NUM>), and the total kink angle is maximized at an angular deviation of <NUM> degrees,
characterized in that:
the multi-ring spacer (<NUM>) further comprises a third ring (<NUM>) coaxial with the first and second ring, the third ring (<NUM>) having a consistent axial length, wherein each axial facing surface (<NUM>, <NUM>) of the third ring is normal to the axis.