Patent ID: 12228032

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG.1shows a piston seal ring (PSR) formed as a split ring seal20having a first circumferential end24, a second circumferential end26, an inner diameter (ID) face28, an outer diameter (OD) face30, a first axial end face32, and a second axial end face34. The PSR has a nominal central longitudinal axis (centerline)500shared with the members it seals when in a nominally centered condition. In the example, first circumferential end24and second circumferential end26form a joint or junction40. The example joint40is a butt joint. An alternative is a shiplap joint.

In central axial or longitudinal section (FIG.3), the seal20is formed as a bent sheet (discussed further below) having a first face42, a second face44, and first46and second48rims or section ends/edges joining the faces. The cross-section is shaped somewhat similarly to the numerals “6” or “9” or the lowercase Greek letter sigma “o” but in both cases with an open, rather than closed, loop or bulb50and rotated so that the extension or ascending portion (ascender or tail)52is directed generally axially away from the loop. This is not to be confused with the uppercase Greek letter “E” which is sometimes used alternatively to describe an E-seal.

A gap54is formed between the rim46and the surface44so that the loop50is partially open with an interior56. Thus, the surface44is an interior surface and the surface42is a generally exterior surface. Thickness between the faces42and44is shown as TS. As is discussed below, this thickness may be generally uniform reflecting bending of the seal cross-section from an original precursor piece of plate or sheet stock of uniform thickness.

Example seal material is an alloy (e.g., steel, such as stainless steel) alone or as a substrate having a full or partial coating such as a hard coating, lubricious coating, or the like.

Rims46,48may be chamfered or beveled and/or may themselves be chamfers or bevels. In the illustrated example, as discussed below, the rim48is essentially at an acute angle θ2relative to the outer face42to itself be a bevel. Thus, the rim48and outer face42converge to a tip or edge60. The tip or edge60may itself be rounded for minimization of stress and damage.

The rim46is shown at an angle θ1relative to the outer surface42. Example 01 is close to 90° and may reflect an original 90° angle of source material, subject to slight deformation during the forming of the cross-sectional shape.

In this example condition, the seal has an inboard radial extreme70along the loop50and an outboard radial extreme72along the extension52. The example outboard radial extreme72is at or near the edge60. Similarly, one axial extreme74of the seal (a low pressure side extreme as discussed below) is also along the surface42of the loop50. The opposite axial extreme76of the seal (high pressure side extreme) is at or near the edge60. The locations72and76may thus be very close to each other along the rounding of the edge60. In alternative embodiments, the cross-sectional shape may cause a greater departure such as if the extension52curved back radially inward near the rim48so that the outward radial extreme72was further away from the edge60along the surface42.

Additionally, the loop50has its own axial extreme78(high pressure side extreme) opposite the common low pressure side axial extreme74of the loop and overall seal. As is discussed further below, the extremes70,74, and78are along regions80,84, and88of reduced cross-sectional radius of curvature (tighter inward concavity (toward the interior56) than portions of the loop aside the regions). In the example, each of these regions are of tighter curvature than the two of regions90,91,92,93on either side of them. Region90is between end46and region88; region91is between regions88and80; region92is between regions80and84; region93extends from region84through the remainder of the loop50and extension52to end48. Such tight curvature is of the two faces and the mean between them. Also, for the face42it ignores slight local flattening at the contact location from compression or wear.

Thus, in the example, the seal central axial cross-section passes: from the end46radially inward and axially in a first direction (aft) along the region90and adjacent (e.g., radially outer) portion of the region88; then radially inward and axially opposite the first direction (forward) along a further (radially inner) portion of the region88, the region91and a/an (aft) portion of the region80; then radially outward and axially opposite the first direction along a (forward portion of the region80, the region92, and the adjacent (e.g., radially inner) portion of the region84; and then radially outward and axially in the first direction along a further (radially outer) portion of the region84through the extension52.

An example radial height or span of the seal is shown as HS. An example axial length of the seal is shown as LS. An example axial length of the loop is shown as LSB.

Example TSis about 0.23 millimeter, more broadly, 0.21 millimeter to 0.25 millimeter or 0.20 millimeter to 0.5 millimeter or 0.20 millimeter to 2.0 millimeters or 0.15 millimeter to 7.0 millimeter.

Example θ2is about 25°, more broadly, 20° to 30° or 15° to 35°. Nevertheless, much higher maxima are possible particularly with rounding and even substantially cantilevering the rim48at an obtuse angle may be used to create a particular elastic response.

Example RIis about 5.0 centimeters to 7.0 centimeters for some applications, more broadly, 3.0 centimeters to 10.0 centimeters or 2.0 centimeters to 15.0 centimeters.

Example HS. is about 3.3 millimeters, more broadly, 2.0 millimeters to 5.0 millimeters or 2.0 millimeters to 10.0 millimeters.

Example LSis about 6.1 millimeters, more broadly, 4.0 millimeters to 12.0 millimeters or 3.5 millimeters to 30 millimeters.

Example LSBis about 3.8 millimeters, more broadly, 3.0 millimeters to 6.0 millimeters or 2.5 millimeters to 12.0 millimeters.

In terms of proportions, the example overall axial length LS, is at least 130%, more narrowly at least 140% or at least 150% of said axial length LSBof the loop with optional alternative example upper limits of 180%, 200%, 220% or 250% for any such lower limits. The example overall radial span HSis 75% to 120%, more narrowly 80% to 100% or 80% to 95% of the axial length LSBof the loop.

In the installed condition ofFIG.4B, a number of dimensions are shown using the prime symbol to indicate there may be a change relative to the relaxed condition ofFIG.3. Similarly, for the locations of the extremes, the prime symbol is also used because there may be slight shifts in locations along the surface42particularly for the loop extremes70′,74′, and78′. The example configuration may have much smaller, if any, departure of the extremes72′ and76′ from their relaxed counterparts.

FIG.4Bshows the seal20seated in an outer diameter groove100in an inner member (e.g., shaft or shaft section)98and sealing against an ID surface110of an outer member112(e.g., a seal runner shown formed as a “bore foot”). The groove100has a first sidewall or end wall102, a second sidewall or end wall104, and a base106joining the two. The groove has a transverse centerplane503. In the example gas turbine engine, the first sidewall is an aft sidewall and the second sidewall is a forward sidewall. Example junctions between the sidewalls and the base are shown as quarter-rounds, chamfers, or bevels108. However, right angle junctions or other transitions are possible. The groove100extends radially inward from an outer diameter (OD) surface section or portion101of the inner member.

FIG.4Ashows the seal20in a gas turbine engine rotor150including the shaft section98. The example rotor is the high pressure compressor (HPC) portion of a high pressure spool of a two-spool engine. The rotor includes a stack of blade disks152. Each blade disk includes a protuberant inner diameter (ID) bore154having an ID surface156. A radial web158extends outward from the bore to a rim structure160. A circumferential array of blades162(shown with airfoil tips cut away) may be mounted to the rim (e.g., via fir tree or dovetail mounting). Or, blade airfoils may be unitarily formed with the rim and the rest of the disk (e.g., an integrally bladed rotor (IBR)).

The example seal20seals between the rotor shaft section98and one of the disk bores154as they rotate as a unit. The PSR accommodates small excursions between the two members it seals due to dynamic or static loading, thermal effects, and the like. The example seal runner112is unitarily formed with the particular disk bore and protrudes axially from the disk bore near the ID surface thereof to a free distal end/rim of the seal runner. This is one non-limiting example of one baseline.

FIG.4Ashows the sealing between a first region or volume600and a second region or volume602. In an example dynamic operating condition, the first region is a high pressure region and the second region is a low pressure region.

In the installed condition, the loop forms three contact points70′,74′,78′ with the groove base106and two side wall surfaces104,102, respectively. The ascending portion52of the cross-section forms a contact point72′ with the ID surface110of the outer member. All four of these contact points are along convex portions of the cross-section of the first face42. In this example, the cross-section of the first face is entirely convex and, thus, the cross-section of the second face44is entirely concave in the central longitudinal section. Clearly, they are also respectively convex and concave in transverse cross-section.

The loop50extends from the first end/rim46to a transition to the extension52which, in turn, extends to the second end/rim48. The loop is generally radially inboard of the extension. A portion of the first face on the loop forms a radial inboard extreme70′ and a portion of the first face on the extension forms a radially outboard extreme72′. In this example, the second end/rim48forms one axial outboard extreme and a portion of the first surface along the loop forms an opposite axial extreme74′. Due to strain of the seal when installed, there may be a slight departure of the locations of the radial outboard extreme, radial inboard extreme, first axial extreme, and second axial end extreme between relaxed/uninstalled and compressed/installed conditions and further slight operational changes once installed.

In an example installation, the seal20is installed to the inner member from what will become the high pressure side via axial translation (e.g., forward translation in the example). The first surface44, along the loop inboard of the second axial end cams/wedges against an outboard end (e.g., a bevel surface122) of the high pressure wall120radially expanding the seal such as by circumferentially expanding a gap at the joint40. Eventually, the seal will slide over an apex of the high pressure wall120(e.g., with contact at an instant radial minimum at or near the ultimate radial minimum). The seal will then snap into the groove. This will at least partially close the gap/joint40.

In the example, the bore foot112has an ID bevel130at a forward or low pressure side. This allows the outer member (disk) to similarly be inserted/installed from the high pressure side by a translation relative to the inner member. The outer member will thus contact the first surface42along the extension52and compress the extension radially inward by a camming/wedging action. Ultimately, the seated installed/compressed condition is achieved.

In operation, there may be varying degrees of relative movement such as slight axial sliding of the outer member along the seal and uniform or local radial displacements. For example, thrust loading and/or differential thermal expansion may produce essentially uniform and constant axial shifts and uniform and constant radial shifts whereas vibration or asymmetric stimulus may cause temporally varying excursions and/or non-uniform radial excursions (e.g., inner and outer members closing at one circumferential location and opening at diametrically opposite). Additionally, torque and twist may cause slight circumferential displacements accommodated by sliding interaction of the outer member relative to the seal and/or the inner member relative to the seal.

In the installed condition, the extension52is axially cantilevered extending past the groove100out over the high pressure sidewall120. This can provide several benefits. First, it provides a relatively compliant interaction versus a stiff interaction of otherwise similar C-seal (e.g., similar material, similar thickness). The local thickness TSis shown between the faces and may represent thickness of the original sheetstock subject to minor losses from polishing and/or increases from plating/coating. The example seal is formed from an alloy (e.g., stainless steel). The example seal is uncoated. However, alternative seals may have coatings for one or more purposes such as a lubricious coating or anti-wear coating along the first face and/or a corrosion coating along the second face.

The open loop cross-section (gap54) exposes the seal surface44to high side pressure opposite all four contact points. This helps bias the seal into sealing engagement at the contact points. Additionally, the cantilevered axial protrusion of the extension52helps allow radially outward flexing of the extension so that centrifugal loading biases the contact point72′ into sealing engagement the ID surface110of the outer member. The axial protrusion of the extension may synergize with the lack of the extension curving back radially inward to provide such case of flexing.

FIG.1shows a radial span between the radial minimum and radial maximum.FIG.1further shows an overall axial span of the seal; an axial span between the low pressure side axial extreme and the radial maximum; an axial span between the radial maximum and the high pressure side overall axial extreme (the first end). Example deformations are relatively small.

An example height HGAPof a radial gap spanned by the extension52between the outer member high pressure sidewall OD surface and outer member ID surface is about 0.48 millimeter, more broadly, 0.40 millimeter to 0.55 millimeter or 0.30 millimeter to 2.0 millimeters.FIG.4Balso shows a groove depth or height HG and a groove length LG. A groove base radius is R′Iand an outer member inner radius is R′O.

Example H′Sis 90% to 95% of HS, more broadly 80% to 96% or 75% to 98%. Example L′SBis similarly about 90% to 95% of LSB, more broadly 80% to 96% or 75% to 98%. Example L′Smay have very little departure from LS. Thus, Example L′Sis 100% to 105% of LS, more broadly, 99% to 105% or 98% to 110%. Accordingly, given these small departures, the broad example relaxed dimensions and proportions may be used as proxies to alternatively define compressed dimensions and proportions in the claims below. Thus, as a general matter, it may be appropriate to claim a given value of dimension or proportion without reference to condition and then alternatively in dependent claims, reference that dimension (or proportion) as either a relaxed dimension (or proportion) or a compressed/installed dimension (or proportion).

Example seal manufacture may start with a strip of spring steel (or other alloy) of the desired thickness TS.

The loop or bulb (or precursor thereof) is formed over a guide or mandrel (e.g., by rolling) the exterior surface of which is shaped to form the loop precursor interior. An example guide has a rounded-corner triangular cross-section so that the corners form theFIG.3tight radius regions88,80, and84.

To form into a ring, the circumferential radius of the seal ring about its axis500is formed to the required dimensions by rolling (e.g., parallel to the ultimate axis500) the ascender/tail about a second guide. This step may further deform the loop or bulb section precursor to the ultimate cross-sectional shape of the loop or bulb.

The seal may optionally be heat treated to obtain desired properties (e.g., heat treatment can modify the grain structure adding durability or can relieve some residual stresses from cold forming the part around the aforementioned guides).

The rim angle θ2may be ground.

The edge60may be abrasively blunted for durability as is done to knife edges.

Among further opportunities for tuning seal performance involve the nature of the joint40. At one extreme, dimensions may be such that there is a complete gap between ends24and26in all installed circumstances. This extreme, for example, would include all conditions such as differential radial expansion of the bore and shaft due to heating or centrifugal loading and non-axisymmetric variations such as slight departures of the shaft and disk from concentricity or slight departures of either from circularity.

Another extreme may involve securing the joint such as via welding (e.g., after installing to the shaft but before outer member (disk) installation). The lack of ability to open or close a gap will influence elastic behavior of the seal. It may be selected along with material and dimensions (particularly thickness) to achieve a desirable sealing contact in particular conditions of interest.

Other variations involve non-uniform gaps and/or non-consistent gaps. For example, a gap may fully close in some conditions but fully open in other conditions or the gap may open in some locations between the rims46and48but not others. This latter option may, particularly, be relevant if the circumferential ends24and26are machined to be other than parallel to each other in a central longitudinal plane.

In addition to the illustrated butt joint and alternative joints more resembling shiplap joints or miter joints, further alternatives may involve an interfitting where one end portion24or26is inserted/received in another. For example, a portion at one of the ends24and26may be deformed/shrunk to telescopically interfit with the other end portion so that the outer surface42of the shrunk portion slidingly contacts or closely faces the inner surface44of the other end portion into which the former is received. The shrinking of the inserted end portion may be achieved by deforming in a die.

Alternatively, one end24or26may be internally beveled and the other end externally beveled so as to be partially receivable in the former. For example, with such a bevel, even if the circumferential gap is the same as a straight butt, the angling of the gap may impose greater resistance to leakage. Furthermore, the circumferential gap may be reduced relative to the straight butt because any interference would simply provide a wedging interaction of the externally beveled end into the internally beveled end. This wedging would merely potentially open up gaps with the contact surfaces of the groove and runner but would not overly stress the seal. In yet other hypothetical embodiments, there may be no pre-shrinkage but merely one end inserted into the other to telescope thus opening up gaps at the contact locations along a small circumferential extent.

FIG.4shows an example gas turbine engine800as a two-spool turbofan engine. Although shown as a high bypass turbofan, a low bypass turbofan may have similar features. The engine800has an engine case822surrounding a centerline or central longitudinal axis500. An example engine has a fan section824including a fan826within a fan case828. The example engine includes an inlet830at an upstream end of the fan case receiving an inlet flow along an inlet flowpath520. The fan826has one or more stages832of fan blades (typically one in a high bypass turbofan and more in a low bypass turbofan). Downstream of the fan blades, the flowpath520splits into an inboard portion522being a core flowpath and passing through a core of the engine and an outboard portion524being a bypass flowpath exiting an outlet834of the fan case.

The core flowpath522proceeds downstream to an engine outlet836through one or more compressor sections, a combustor, and one or more turbine sections. The example engine has two axial compressor sections and two axial turbine sections, although other configurations are equally applicable. From upstream to downstream there is a low pressure compressor section (LPC)840, a high pressure compressor section (HPC)842, a combustor section844, a high pressure turbine section (HPT)846, and a low pressure turbine section (LPT)848. Each of the LPC, HPC, HPT, and LPT comprises one or more stages of blades which may be interspersed with one or more stages of stator vanes. In many low bypass turbofan configurations, the core and bypass flows rejoin to exit a nozzle (e.g., a variable nozzle).

In the example engine, the blade stages of the LPC and LPT are part of a low pressure spool mounted for rotation about the axis500. The example low pressure spool includes a shaft (low pressure shaft)850which couples the blade stages of the LPT to those of the LPC and allows the LPT to drive rotation of the LPC. In the example engine, the shaft850also drives the fan. In the example implementation, the fan is driven via a transmission (not shown, e.g., a fan gear drive system such as an epicyclic transmission) to allow the fan to rotate at a lower speed than the low pressure shaft.

The example engine further includes a high pressure shaft852(of which the shaft section198forms a section) mounted for rotation about the axis500and coupling the blade stages of the HPT to those of the HPC to allow the HPT to drive rotation of the HPC. In the combustor844, fuel is introduced to compressed air from the HPC and combusted to produce a high pressure gas which, in turn, is expanded in the turbine sections to extract energy and drive rotation of the respective turbine sections and their associated compressor sections (to provide the compressed air to the combustor) and fan.

Alternatively to sealing a disk bore to a shaft, such a seal may be applied to static structures such as cases. Alternatively, applications beyond gas turbine engines include pumps, turbochargers, and other turbomachines.

The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description.

One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.