Fluid-cooled mechanical face seal rotor

A fluid-cooled seal rotor is described for a seal assembly that includes a seal case, a seal stator, and wherein the rotor has a sealing face on a first side and a heat-transfer structure on a second side. The heat-transfer structure may be a roughened surface. The heat-transfer structure may have protrusions which may be fins, including fins with roughened surfaces. The heat-transfer structure may have additional heat-transfer structures thereon to create complex, including fractal, structures. The fins may be shaped as impellers to move oil over the heat-transfer structure. Channels between fins may have a width greater than twice the boundary layer thickness for the fluid engaged by the fins. The fluid-cooled rotor, the seal assembly having the fluid-cooled rotor, an air turbine starter having the seal assembly, air turbine starters and other machines with rotating shafts using the seal are within the scope of the invention.

FIELD OF THE INVENTION

The present invention relates to gas turbine engines and, more particularly, to a fluid-cooled seal rotor used in gas turbine engines, gas turbine engine starters, and auxiliary power units, that provides lower seal face temperatures and increased wear life compared to presently known seals.

BACKGROUND OF THE INVENTION

Many relatively large turbine engines, including turbofan jet engines, may use an air turbine starter (ATS) to initiate their rotation. The ATS is mounted by the jet engine, much as a starter for an automobile is located by the automobile's engine. The ATS may be coupled to a high pressure fluid source, such as compressed air, which impinges upon the turbine wheel in the ATS causing it to rotate at a relatively high rate of speed. The ATS includes an output shaft that is coupled, perhaps via one or more gears, to the jet engine. The output shaft rotation in turn causes the jet engine to begin rotating. The applicant for the present invention, Honeywell International, Inc., has for years successfully designed, developed and manufactured ATSs.

The ATS turbine wheel output shaft may be rotationally mounted within a housing using one or more bearing assemblies. The bearing assemblies, as well as the above noted gears, may be supplied with a lubricant, such as oil. Thus, the ATS may be mounted within a housing that is divided into at least two sections, the turbine section and the output section. The turbine section houses the turbine wheel and includes one or more passages through which the high pressure fluid source passes and impinges upon the turbine wheel, causing the turbine wheel to rotate. The output section, or gearbox, may house the turbine wheel output shaft, the gears, the bearing assemblies, and various other mechanical devices that utilize a lubricant. A seal assembly may be provided between the turbine section and output section of the ATS to substantially inhibit the lubricant used in output section from leaking out of the output section into the turbine exhaust section.

The seal assembly may be a face seal that includes a rotor, a stator, and a seal case. The rotor is mounted on the turbine wheel shaft and, thus, rotates with the turbine shaft, and has an axially facing flange, or sealing face, that extends radially away from shaft. The seal case is mounted to the ATS housing in the turbine section and surrounds the turbine wheel output shaft. The stator is housed within the seal case and sealingly engages the axially facing flange of the rotor. The rotor and stator flat annular faces sealingly engage under a biasing force imposed by a biasing mechanism in the seal case.

Face seal stators with carbon faces are known to be used as seals in engines, including air-turbine engines and air turbine aircraft engine starters. Carbon-stator face seals encounter high-temperature loads caused by friction between the carbon stator sealing face and the rotor face, which may be metal. Heat may cause the oil on the seal rotor and stator to solidify into coke as a result of the high temperatures at the face. The coke accumulations may compromise face seal performance and limit face seal life. Compromise of a face seal can result in sufficient loss of lubrication to the bearings, gears, and other lubricated components in the air turbine starter gearbox to cause damage to these components. It should be appreciated that ATS's with the above design are nonetheless safe for their intended use.

Carbon-stator face seals may additionally incorporate other technologies such as film-riding face geometries (Rayleigh, Spiral, and wave designs) as discussed in NASA/TM-1998-206961 AVT-PPS Paper No. 11 “Advanced Seal Technology Role in Meeting Next Generation Turbine Engine Goals”. Various film-riding echnologies are known in the art, and generally include shaped configurations of the sealing surfaces of either the stator or the rotor. The shaping of the sealing surface is specific to the task of maintaining a film of a fluid between the stator and rotor sealing surfaces to minimize friction while maintaining a seal. The fluid used may be, for example, air, oil, or an air-oil mixture.

Hence, there is a need for a seal assembly that reduces the rate and likelihood of coke accumulation between the stator sealing face and the seal rotor face, thereby reducing the likelihood of loss of lubrication to rotating components within the starter gearbox. The present invention addresses this need.

SUMMARY OF THE INVENTION

The present invention provides a seal assembly that reduces the rate and likelihood of coke accumulation on carbon face seals between the carbon-face stator and the metal-face rotor and on the stator ring and rotor outside of the contact face.

In one embodiment of the present invention, and by way of example only, an air turbine starter includes a housing having a fluid inlet port, a fluid outlet port, and a fluid flow passage extending therebetween; a turbine wheel having a turbine shaft rotationally mounted within the housing, the turbine wheel further having at least two turbine blades extending radially into the fluid flow passage; and a seal assembly mounted in the housing. The seal assembly includes: a seal case mounted on the housing; a seal stator mounted within the seal case, the seal stator having at least a first face and a second face; a seal rotor mounted on the turbine shaft, said seal rotor having a first side adapted to sealingly engage said seal stator first face and a second side having at least a partially roughened surface and one or more fins thereon.

In another exemplary embodiment, a seal assembly is disclosed for sealing an opening through which a rotating shaft extends, the seal assembly comprising a seal case mounted proximate the opening; a seal stator mounted within the seal case, the seal stator having at least a first face and a second face; and a seal rotor assembly adapted to be mounted on the rotating shaft, the seal rotor assembly having a first side adapted to sealingly engage said seal stator first face and a second side having at least a partially roughened surface and one or more fins thereon.

In yet another exemplary embodiment, a rotor for a face seal having a stator is disclosed, comprising a substantially annular body having a first side and a second side, the first side adapted to sealingly engage a face of the stator and one or more fins and at least a partially roughened surface on the second side of the body.

In still yet another exemplary embodiment, an apparatus is disclosed having a shaft rotationally mounted therein and extending between a first volume and a second volume, the apparatus comprising a web disposed between the first and second volumes, the web having an opening through which the shaft extends; a seal stator mounted on the web proximate the opening; and a seal rotor, mounted on the shaft and disposed at least partially within the first volume and proximate the opening, the seal rotor having a first side adapted to sealingly engage the seal stator and a second side having one or more fins and at least a partially roughened surface.

In an exemplary embodiment of a method of modifying an air turbine starter, an air turbine starter including a housing, a turbine wheel having a turbine shaft rotationally mounted within the housing, a seal rotor mounted on the turbine shaft, and a seal stator assembly mounted to the housing and surrounding the shaft and having at least a portion thereof sealingly engaging a face of the seal rotor, the method comprising removing the seal rotor from the turbine shaft; and mounting a new seal rotor on the turbine shaft, wherein the new seal rotor assembly includes said seal rotor having a first side adapted to sealingly engage said seal stator first face and a second side having at least a partially roughened surface and one or more fins thereon.

In other aspects of the present invention, one or more of the above elements can be used in a gas turbine engine, or other apparatus having a rotating shaft.

Other independent features and advantages of the preferred seal assembly will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Before proceeding with the detailed description, it should be appreciated that the present invention is not limited to use in conjunction with a specific type of rotating machine. Thus, although the present invention is, for convenience of explanation, depicted and described as being implemented in an air turbine starter, it should be appreciated that it can be implemented in numerous other rotating machines including, but not limited to, a gas turbine engine, a gas turbine auxiliary power unit (APU), a turbo-charger, an air cycle machine, a hydraulic pump, a water pump, or various other chemical and industrial pumps and other rotating machinery.

Turning now to the description, a cross-sectional view of an exemplary air turbine starter (ATS) that is used to initiate the rotation of a larger turbine, such as a turbofan jet engine, is depicted in FIG.1. The ATS100is enclosed within a housing assembly102that includes at least a turbine section104and an output section106. The housing assembly102may be made up of two or more parts that are combined together or may be integrally formed as a single piece. The housing assembly102includes an inlet plenum108, which directs compressed air into the housing assembly102. The compressed air received at the plenum108flows through an annular flow passage110and out a radial outlet port112. The annular flow passage includes an axial flow portion114and a substantially curved radial flow portion116. The axial flow portion114is formed through a stator assembly118that is mounted within the housing assembly turbine section104proximate the fluid inlet port108. The radial flow portion116, which flares the annular flow passage110radially outward, is formed between a portion of the housing assembly turbine section and an exhaust housing120that is mounted within the housing assembly102.

A turbine wheel122is rotationally mounted within the housing assembly turbine section104. In particular, the turbine wheel122has a shaft124that extends from a hub126, through the exhaust housing120, and into the housing assembly gearbox106. The turbine wheel output shaft124is rotationally mounted in the housing assembly gearbox106by bearing assemblies128. A gear132is coupled to the turbine wheel output shaft124, and meshes with a compound planetary gear train134. The compound planetary gear train134engages a ring gear138and a hub gear142, which is in turn coupled to an overrunning clutch144. During operation of the ATS100, this gearing configuration converts the high speed, low torque output of the turbine wheel output shaft124into low speed, high torque input for the overrunning clutch144.

The overrunning clutch144, as noted above, is coupled to the hub gear142, which is supported by another bearing assembly146. A drive shaft148extends from the overrunning clutch144, through the turbine housing output section106, and is coupled to a turbine output shaft152. The output shaft152may be coupled to, for example, a turbofan jet engine gearbox (not illustrated).

A face seal assembly160provides a fluid-tight seal between the rotating turbine wheel126and the fluids, such as air, inside of the housing assembly turbine section104and the lubricant, such as oil, in housing assembly gearbox106. The face seal assembly160includes a rotor assembly162, and a stator seal assembly164that includes a seal case166and a seal stator ring168. The rotor assembly162is mounted on the turbine wheel shaft124, and has an axially facing flange169that extends radially outwardly away from the turbine wheel output shaft124. The seal case166is mounted to the exhaust housing120and surrounds the turbine wheel output shaft124. The seal stator ring168is housed within the seal case166and sealingly engages the axially facing flange169of the rotor assembly162, providing the fluid tight seal between the rotating turbine wheel output shaft124and the fluids held inside of the turbine housing section104and gearbox106. Though not explicitly depicted, it should be appreciated that another face seal assembly160may also be included in the ATS100that seals the turbine output shaft152.

An exemplary embodiment of the seal stator assembly160is shown in cross section in FIG.2and will now be described. The seal stator assembly160includes the seal case166, the seal stator ring168, an O-ring202, a spring washer204, a retaining ring206, and may additionally include a seal washer208. Seal stator ring168includes a flat annular face, or sealing face167, which sealingly engages seal rotor assembly162. Seal stator ring168is mounted against rotation in seal case166and is preferably biased to contact rotor assembly162by spring washer208. Retaining ring206retains seal stator168in seal case166, and O-ring202seals the junction of the seal stator168and the seal case166. Seal case166is mounted against rotation in the housing proximate an opening through which shaft124extends. Other stators are known in the art and may be used with the seal rotor162of the present invention. The stator sealingly engages the seal rotor assembly162by rotationally sliding contact between the stator flat annular face167and an annular portion, or sealing surface306(FIG.3A), of the rotor301ofFIG. 3A, which is fixed to the rotating shaft. In some alternate embodiments, the stator164sealingly engages the seal rotor assembly162by riding a fluid film, such as an air film, between the stator flat annular face167and a sealing surface306adapted for film-riding. In other alternate embodiments, the stator sealing face167sealingly engages the seal rotor assembly162by riding a fluid film between the sealing surface306and the stator face167which is adapted for film-riding.

FIGS. 3A and 3Bshow an exemplary rotor assembly162first and second sides, respectively. As illustrated therein, the rotor assembly162includes a main rotor, or body,301, which has a first side302, a second side300, and a central opening320for mounting the rotor assembly162on the turbine shaft124. The rotor assembly162is shown as an annulus and the central opening320is shown as being circular. It will be appreciated that, in some embodiments, the central opening320need not have a circular cross-section and the rotor assembly162need not be an annulus. Rotor301also has a circumferential arc that is illustrated as a 360-degree arc co-extensive with outer peripheral surface304inFIGS. 3A and 3B. Fins308and channels310may be spaced apart in reference to the circumferential arc. Chord lengths, or angles subtended by chords may also be used for defining spacing for fins308and channels310. Preferably, the void space created by sum of the channels310comprises between one percent and eighty percent of the circumferential arc.

No matter the particular shape, at least a portion306of the rotor assembly first side302is adapted to sealingly engage the seal stator160. Hence, in the depicted embodiment, the rotor assembly first side302is substantially flat, as shown inFIGS. 3C and 3D, which are cross sections A-A′ through the rotor301ofFIGS. 3A and 3B. However, it will be appreciated that the first side302may alternatively include a sealing surface306that extends axially away from the first side302, and that additionally extends radially to a dimension to appropriately engage the seal stator160. The sealing surface306may be a different material than rotor301. For example, a chromium sealing surface306may be used on an steel alloy rotor301. The sealing surface306of the rotor301may be adapted for generating a film between the rotor sealing surface306and the seal stator face167for film-riding, as is known in the art.

The rotor assembly second side300may include a bearing engagement surface314which circumscribes the opening320and extends axially from the rotor assembly second side300. The bearing engagement surface314may engage, for example, a portion of the bearing assembly128depicted in FIG.1. In some embodiments, the bearing engagement surface314may be omitted.

The fin or fins308are preferably formed by machining radial channels310into the into the rotor assembly second side300, though it will be appreciated that various other methods and/or processes may be used to form the fins308. It will additionally be appreciated that the fins308could be separate structures, or part of a separate structure, that is coupled to the rotor assembly second side302. The fins308improve the heat transfer capacity of the rotor assembly by providing additional heat transfer surface. In addition, the fins308are preferably configured to impel motion of a fluid over the surface of rotor assembly second side302and the fins308thereon. As such, heat transfer from the seal stator160, through the seal rotor162, to the impelled fluid is further improved. In an alternate embodiment (not shown in FIG.3B), a single fin may be used. For example, a spiral fin1902as shown inFIG. 19may serve as a heat transfer structure.

Radial channels310are configured to comprise, in sum, between one and eighty percent, inclusive, of the circumferential arc of rotor second side300along at least the outer edge of the rotor301. The void space created by channels310is preferably measured along the circumferential arc coextensive with the outer peripheral surface304of rotor301. Void spaces in the range of one percent and eighty percent are preferred. Radial variation of the void space is included in the present invention (SeeFIG. 6, for example).

In addition to including a plurality of fins308, at least a portion of the rotor assembly second side302is roughened. It will be appreciated that either, or both, the channels310and the fins308may be roughened, and that all or a portion of the channels310and fins308may be roughened. In a particular preferred embodiment, substantially the entire rotor assembly second side302, except for bearing engagement surface314but including both the fins308and the channels310, is roughened. By roughening at least a portion of the surface of the rotor assembly second side302, the heat transfer surface area of the rotor assembly second side302is further increased. The roughened surface additionally increases the thickness of the fluid boundary layer at the fin or surface trailing tip which may increase heat transfer by heating more of the fluid flowing past the fin surface area. Thus, the heat transfer capability of the rotor assembly162is further improved.

At the same time, the roughened surface increases the thickness of the boundary layer adjacent to channel310and fin308surfaces. The thickness of this boundary layer can be determined, in each case, based upon the fluid properties, the fin308geometry, and the velocity of the fin308through the fluid. Because of the boundary layers on the channel310surfaces, the width of each channel310is preferably more than twice the thickness of the boundary layer.

The rotor assembly second side302may be roughened using any one of numerous methods and processes. For example, some or all of the rotor assembly second surface302may be roughened using heat treatment processing, acid etching, electrostatic plating, sputtering, plasma spray, HVOF (High Velocity Oxygen Fuel), coating, laser marking, bead blasting, and grit blasting. The skilled artisan will recognize that, depending on the particular process/method used, the rotor assembly second side302may be roughened by removing some material from, or by adding some material to, the surface of the rotor assembly second side302. In some embodiments, the roughening process may be controlled such that the roughened surface forms a fractal pattern. The roughness magnitude of the rotor assembly second side302may vary depending upon, for example, the properties of the fluid to which the rotor assembly second side302is exposed, and the speed at which rotor assembly162will rotate. In a particular preferred embodiment, the rotor assembly second side302is preferably roughened to a surface roughness Ra of greater than 125 micro-inches. Nonetheless, it will be appreciated that the determination of the proper roughness may be made in each particular case to optimize the heat transfer characteristics of the rotor assembly162.

In the depicted embodiment, the rotor assembly second side302additionally includes an annular well312, which is formed proximate, and substantially circumscribes, the bearing engagement surface314. It will be appreciated that in some embodiments the annular well312may be omitted. It will additionally be appreciated that, although the annular well312is shown as having a rectangular cross section, other cross sectional shapes are also contemplated. For example, a “V” or “U”-shaped groove or a shape adapted for conducting fluid into channels310between fins308may be used. The annular well312may additionally comprise heat-transfer features including, without limitation, roughening, machined surfaces, and thermally conductive coatings. For example, the interior axially-aligned walls of annular well312may be threaded to impel fluid into the bottom of the well in response to rotation of the rotor assembly162, the fluid so impelled finding its path outward through channels310, and the threads may be roughened to improve heat transfer to the impelled fluid.

InFIG. 3B, the fins308are depicted as being of equal size and radial orientation. It will be appreciated, however, that fins308may be of different sizes and different configurations. Exemplary and non-limiting alternative configurations are shown inFIGS. 4-6. For example, inFIG. 4, fins408on rotor second side402are oriented tangentially to the annular well412. In an alternate embodiment, each fin308or408may have a different orientation.

In the exemplary embodiment ofFIG. 5, fins508and channels510have a curved shape which provides improved fluid impelling capabilities. A preferred amount of curvature of fins508may be determined based on the particular fluid engaged and the rotational speed range of the fins508by methods known in the art of fluid dynamics.

InFIG. 6, this exemplary embodiment includes fins608of different sizes and branching channels610. The fins608, channels610, annular well612, and all surfaces thereof, may be shaped and adapted to maximize heat transfer from the rotor assembly162to the fluid. In alternate embodiments, any of the embodiments ofFIGS. 4-6may have fins crossing the fins608shown. (See FIG.20).

In each of the embodiments depicted and described above, the rotor assembly second side302,402,502, and602was at least partially roughened and had a plurality of fins308,408,508, and608formed thereon. Alternatively, by controlling the radial length of the channels and controlling the channel width, the ratio of boundary layer thickness at fin trailing tip to channel width can be optimized to reduce the need for surface roughening. Optimization will result in additional machining of radial space instead of producing a roughened fractal surface but optimization can be achieved that maximizes the heat transferred to the fluid flowing across the fins and in the holes of the rotor. In an alternative embodiment, such as that shown inFIG. 7, the rotor assembly second side702has a roughened surface708and no fins308on the second side702. As with prior embodiments, the rotor seal second side702may be roughened using any one of the previously mentioned processes and/or methods, and may form a fractal pattern.

Yet another alternative method of roughening the rotor assembly second side802is shown in FIG.8. In accordance with this exemplary embodiment, a pattern of holes808is formed in the rotor assembly second side802. The holes808may extend only partially through the rotor assembly162. A wide range of hole patterns may be used, so long as the rotor assembly162remains balanced. In yet another alternate embodiment (not depicted), the holes808may be threaded, and bolts of a material with a very high thermal conductivity, such as gold, may be threaded therein so that the bolt shaft acts as high-conductivity thermal path and the bolt heads serve as fins308.

The fins308may be of any one of numerous cross-sectional shapes. In the embodiment depicted inFIGS. 3A and 3B, the fins have a generally rectangular cross section. Some exemplary, and non-limiting, alternate cross sectional shapes are illustrated inFIGS. 9-12, some of which depict a roughened surface as well.FIGS. 9-12are elevation views through a section B-B′ as shown in FIG.3B. In particular,FIG. 9shows fins908with a “T”-shaped cross section, and with fins908and channels910all being the same size, shape, and orientation on a rotor body301. As was previously noted, the present invention is not limited to fins908and channels910all being the same size, shape, or orientation on a single rotor assembly162. Likewise, the cross-sectional size and shape may vary over the length of any fin908.

InFIG. 10the fins1008are oriented for a rotor assembly162rotating in the direction indicated by arrow1002. The fins1008impel fluid downward into channels1010where rotational motion of the rotor assembly162moves the fluid radially outward over the second-side surface of the rotor assembly162. A cross-sectional shape of the fins1008may be determined for each set of fluid properties and velocity ranges for which an embodiment may be made, using methods known in the art of fluid dynamics.

InFIG. 11, the exemplary cross sectional shape is substantially triangular and is roughened by including progressively smaller triangular-shaped protrusions on each fin1108. It will be appreciated that the progressively smaller protrusions may be configured to form a fractal pattern.FIG. 12depicts another exemplary fractal pattern for fins1208and channels1210based upon an inverted triangular cross section. An advantage of using the inverted triangular fins1208is the relatively short thermally conductive path through the rotor body301to the second side surface300and the larger area, as compared to embodiment1100, for which a short thermally conductive path is available. The wider fin1208tops may assist in keeping fluid in the channel1210and moving radially, as preferred, instead of axially away from the rotor assembly162.

As was noted above, the seal rotor depicted herein is not limited for use in an ATS, but may be used in any one of various machines.FIG. 13depicts an exemplary embodiment1300of a portion of a generic rotating machine and shows rotor assembly162in its relationship with stator assembly160, with a shaft1324and with bearing1328. In embodiment1300, rotor assembly162is mounted proximate a bearing through which oil flows, thereby providing a cooling fluid to the second side of rotor assembly162. In other embodiments, oil or oil aerosols may be the ambient fluid with no particular directionality other than that supplied by the rotor assembly162. In a particular embodiment, a flow of oil may be directed onto the rotor assembly162from an oil pump, oil cooler, or a conduit. Other fluids than oil, such as hydraulic fluid and air, may be used as a cooling fluid for rotor assembly162.

Stator assembly160includes seal case166mounted against rotation in stator casing164which is, in turn, mounted against rotation on web1302. Web1302may be any part of a housing, or may be independent of a housing. For example, for a seal for a mixer shaft extending through the wall of a chemical vat, the vat wall would be web1302.

Stator168is sealingly engaged by sealing surface1306on the first side of rotor assembly162. Sealing surface1306may be metal plating, such as chromium, in an annular depression formed in the rotor first side. The design of the radial extent of the sealing surface1306depends at least partially upon the contact load on the seal160, with higher loading requiring more sealing area.

Channels310are not limited to running parallel to the rotor first side302. For example,FIG. 14depicts exemplary embodiment1400having a channel1410extending axially through the rotor assembly to enable a cooling fluid, such as oil, to reach an outer annular region of the stator168for direct cooling of the stator168. For further example,FIG. 15depicts exemplary embodiment1500having a channel1510that deepens in the radially outward direction to provide a short thermal conduction path to the second side of rotor assembly162. Fin1508illustrates generally that the fin1508may be shaped to adapt to proximate objects or for fluid dynamic purposes. For yet another example,FIG. 16depicts exemplary embodiment1600having a channel1610that may minimize the thickness of the rotor assembly162above the stator168to provide a short thermal conduction path to the second side of rotor assembly162. Fin1608may have flange1611which extends into channel1610to establish flow characteristics within the channel1610.

Because it maximizes the heat transfer surface, many small fins308show significantly superior performance over a few large fins308. Experimentation in an ATS application has shown that20radial fins308produce a reduction of 30 degrees Fahrenheit in seal rotor301temperature. Considerable reductions in stator sealing face temperatures may thus be obtained by the disclosed method of maximizing the heat transferred to the fluid flowing through the fins, channels, and holes by optimization of the 1) roughness/fractal nature of the surfaces in contact with the fluid, 2) the channel width vs boundary layer thickness, 3) surface area exposed to the fluid, thereby reducing coke formation and extending seal life.

FIG.17A andFIG. 17Bshow an exemplary embodiment of seal rotor second side1700having radial holes1702drilled through the outer peripheral surface1710of the rotor which penetrate through the rotor body1705to the rotor second side surface1708. The holes1702form channels having a surface1704, which may be roughened to improve heat transfer to a fluid flowing therein. In an alternate embodiment, holes1702may penetrate, at least partially, rotor first side surface1706.

FIG.18A andFIG. 18Bshow an exemplary embodiment of seal rotor second side1800having radial holes1802drilled through the outer peripheral surface1810of the rotor which penetrate through the rotor body1805to the annular channel1812. The holes1802form channels having a surface1804, which may be roughened to improve heat transfer to a fluid flowing therein. In an alternate embodiment, fins may be added to seal rotor second side1800.

FIG. 19shows a diagram of an exemplary embodiment of a seal rotor second side1900having a single spiral fin1902. The fin1902is illustrated as having a triangular cross-section with a smooth filet between the base and the rotor surface, wherein the spiral line ofFIG. 19represents the apex of the fin1902. Fin1902may be of any cross-sectional shape. In an alternate embodiment, a fin1902may be formed by machining a spiral groove in the seal rotor second side1900.FIG. 20shows a diagram of an exemplary embodiment of a seal rotor second side2000having two spiral fins2002and2004that are offset rotationally by approximately ninety degrees. Additional fins2002and2004and additional or alternate offsets may be used, or the direction of rotation of the threads may be reversed on alternating threads of a multi-start thread design resulting in a fin pattern similar to that shown in FIG.20.

FIG. 21shows an exemplary section B-B′ fromFIG. 3Bfor an embodiment having fins2108and channels2110of different sizes on a second side of a single rotor body301. The sizes and shapes of fins such as fins2108and of channels such as channels2110may be adapted to particular needs for seal cooling given available fluid properties and mechanical constraints. In a preferred embodiment using radial or tangential fins, each seal rotor has more than ten fins.

FIG. 22is a diagram showing an exemplary pattern of holes2202through rotor body2205in an exemplary seal rotor second side2200. The holes penetrate the outer peripheral surface2210of rotor body2205at a first hole end, extend through the rotor body2205and penetrate the outer peripheral surface2210at a far hole end. The herringbone pattern illustrated inFIG. 22may also be used for fins.

It will be appreciated that there is significant economic advantage to combining film-riding technology with the fin technology disclosed herein to reduce the rate of oxidized oil filling of the hydrodynamic features of the film riding technologies. Oxidized oil filling of the hydrodynamic features of air film-riding seals has been noted in hardware returned from flight review and is a reliability and operating life concern for film-riding designs.