Key washer for a gas turbine engine

A gas turbine engine comprising: a shaft about an axis; a first turbine assembly mounted to the shaft, a first flow path and a second flow path extending through first turbine assembly along the axis. The second flow path is located radially inward of the first flow path relative to the axis. A second turbine assembly is about the axis downstream of the first turbine assembly, with a gap defined between the first turbine assembly and the second turbine assembly, the gap in fluid communication with the first flow path and the second flow path. A washer is downstream of the first turbine assembly. The washer has an annular body including a deflector between the first turbine assembly and the second turbine assembly, the deflector obstructing the first flow path and extending toward the second flow path.

TECHNICAL FIELD

The application relates generally to gas turbine engines and, more particularly, to key washers for turbine assemblies of gas turbine engines.

BACKGROUND OF THE ART

Operation of gas turbine engines results in temperatures that may vary from ambient at the inlet to well above 1000 C downstream therefrom, for example inside the combustion section. Conventionally, cooling systems are used to compensate for combustion temperatures exceeding that which some components of the engine are designed to endure. For instance, a turbine rotor may be cooled by circulating air from relatively cooler portions of the engine, either axially through its hub or radially along its disc. Nonetheless, thermal gradients occur across some engine components, resulting in stresses that may undesirably affect engine efficiency and component life. Moreover, in practice, these thermal gradients may vary over the life of the engine, both in terms of location and magnitude. Improvements are therefore desirable.

SUMMARY

In accordance with an embodiment, there is provided a gas turbine engine comprising: a shaft about an axis; a first turbine assembly mounted to the shaft, a first flow path and a second flow path extending through first turbine assembly along the axis, the second flow path located radially inward of the first flow path relative to the axis; a second turbine assembly about the axis downstream of the first turbine assembly, with a gap defined between the first turbine assembly and the second turbine assembly, the gap in fluid communication with the first flow path and the second flow path; and a washer downstream of the first turbine assembly, the washer having an annular body including a deflector between the first turbine assembly and the second turbine assembly, the deflector obstructing the first flow path and extending toward the second flow path.

In accordance with another embodiment, there is provided a method of redirecting a flow in a gas turbine engine, the method comprising: directing a first flow through a first flow path of a first turbine disc along an axis of the gas turbine engine; directing a second flow through a second flow path of the first turbine disc inward the first flow path relative to the axis along the axis; and deflecting the first flow downstream of the first turbine disc to direct the first flow toward the second flow downstream of the first turbine disc.

In accordance with yet another embodiment, there is provided a washer for a gas turbine engine, the washer comprising: a first ring portion; at least one first keying feature extending outwardly from a peripheral surface of the first ring portion; at least one second keying feature extending from an upstream surface of the first ring portion transverse to the peripheral surface; and a second ring portion radially inward of the first ring portion, the second ring portion defining a deflector surface transverse to an axis of the first ring portion.

DETAILED DESCRIPTION

FIG. 1illustrates a gas turbine engine10of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication along an axis12of the engine10an inlet section14through which ambient air enters the engine10, a compressor section16for pressurizing the air, a combustion section18in which pressurized air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section20for extracting energy from the combustion gases. In this embodiment, the turbine section20includes a first turbine22, a second turbine24and a power turbine26. Other embodiments with fewer or more turbines are possible. The first turbine22may be a high-pressure turbine drivingly connected to a first impeller28of the combustion section18via a hollow first shaft22a collinear with the axis12. The second turbine24may be a low-pressure turbine drivingly connected to a second impeller30of the compressor section16via a hollow second shaft24a. The second shaft24aextends coaxially inside the first shaft22a. The power turbine26may be a two-stage power turbine drivingly connected to a propeller (not shown) disposed upstream of the inlet section14via a hollow third shaft26a. The third shaft26aextends coaxially inside the second shaft24a. The first, second and third shafts22a,24a,26aare rotatable relative to one another about the axis12of the engine10with their respective turbines.

A washer32of the first turbine22(in this case a key washer, characteristics of which will be described in more detail hereinbelow), is disposed along the axis12upstream of the second turbine24. Referring toFIG. 2, the washer32is shown in more detail. The washer32has opposite upstream and downstream sides along a washer axis. The washer32has a first ring portion32asurrounding the washer axis. In an embodiment, the washer axis is collinear or minimally offset from the axis12when the washer32is installed in the engine10. The first ring portion32ais circumscribed between an inner diameter and an outer diameter that lay in a plane to which the washer axis is normal. The washer32may be configured to rotationally engage with other components of the engine10via the first ring portion32aupon rotation about the washer axis. For instance, the first ring portion32amay have one or more anti-rotational features (i.e., first keying features) disposed about the washer axis. In this embodiment, the first ring portion32ahas an outer peripheral surface32bfrom which first keys32cof the washer32extend outwardly relative to the washer axis. The first keys32cmay have a shape complementary to that of a component of the engine10so as to be engageable therewith. The first keys32cmay be evenly spaced around the washer axis. In this embodiment, a total of four first keys32cis provided, oriented radially relative to the washer axis and angularly spaced relative to one another by about 90 degrees. In other embodiments, the first keys32cmay be provided in different amounts, may be spaced otherwise, and may be oriented in ways other than substantially radially. In yet other embodiments, a sole first key32cmay be provided. It shall be understood that the first keys32cdefine first keying features of the washer32, i.e., anti-rotational features of the washer32configured to hinder rotation thereof about the washer axis relative to a first component of the engine10interfacing therewith. In some embodiments, anti-rotational features other than the first keys32cmay be used to hinder rotation, such as fasteners or other shapes which may adequately mesh with a corresponding complementary shape of the first component of the engine10.

Further, the first ring portion32amay have an annular ridge32ddisposed about the washer axis inward of the outer surface32b. The annular ridge32dmay otherwise be flush with the outer surface32b. The annular ridge32dmay have one or more anti-rotational features (i.e., second keying features) disposed about the washer axis. The annular ridge32dmay extend from an upstream surface of the first ring portion32aoriented transversely to the outer surface32band in a generally axial direction, such as by being parallel to the washer axis. The annular ridge32dmay have a shape complementary to that of components of the engine10so as to be engageable therewith. For example, the annular ridge32dmay have a plurality of slots32edisposed circumferentially such that a remainder of the annular ridge32dforms a crenelated pattern facing away from the upstream side of the washer32. In this embodiment, the slots32emay be described as keying slots, and the remainder of the annular ridge32dmay be described as defining a plurality of second keys32f. The slots32emay be evenly spaced around the washer axis. For example, a total of ten slots32emay be provided and be angularly spaced relative to one another by about 36 degrees. In other embodiments, the annular ridge32dmay be oriented in ways other than parallel. The slots32emay be provided in different amounts and may be spaced otherwise. In yet other embodiments, a sole slot32emay be provided. It shall be understood that the annular ridge32ddefines second keying features of the washer32, i.e., anti-rotational features of the washer32configured to hinder rotation thereof about the washer axis relative to a second component of the engine10interfacing therewith. In some embodiments, anti-rotational features other than the slots32eand the second keys32fmay be used to hinder rotation, such as fasteners or other shapes which may adequately mesh with a corresponding complementary shape of the second component of the engine10.

It shall also be understood that the first and second keying features together form an anti-rotational feature of the washer32configured to hinder rotation of any one of the first component and the second component of the engine10relative to the other about the washer axis. In some embodiments, anti-rotational features other than the first and second keying features may be used to hinder rotation between components of the engine10interfacing with the washer32.

The washer32has a deflector32gforming a second ring portion inward the first ring portion32arelative to the washer axis. As such, the first ring portion32amay form an outer diameter of the washer36defined relative to the washer axis, and the deflector32gmay form an inner diameter of the washer32inward the outer diameter relative to the washer axis. The first ring portion32aand the deflector32gmay be interconnected, such that the washer32forms a unitary piece. The unitary piece the washer32defines may be a monolithic body. In other embodiments, the first ring portion32aand the deflector32gmay be separate components arranged to be attachable to one another or otherwise rotationally engageable relative to one another about the washer axis.

The deflector32ghas a deflector surface32hfacing upstream and configured to redirect a flow directed thereagainst. The deflector surface32his shaped to redirect the flow in a desired direction. The flow may for example be directed against the deflector surface32hin a path generally parallel to the washer axis. The desired direction may for example be inward from the deflector32g, i.e., away from the deflector32gtoward the washer axis. The annular ridge32dand the deflector32gmay be successively disposed along the washer axis. The deflector surface32hmay have an upstream boundary32iflush with an inner surface of the annular ridge32dand extend therefrom to a downstream boundary32jso as to ramp away from the annular ridge32dof the first ring portion32atoward the washer axis. For instance, a normal of the deflector surface32hmay be directed toward the washer axis at its upstream boundary32i. The normal of the deflector surface32hmay be directed upstream and parallel to the washer axis at its downstream boundary32j. At the downstream boundary32j, the normal of the deflector surface32hmay otherwise be directed upstream at an angle relative to the washer axis. The angle may be for example 45 degrees. The deflector32ghas a deflector surface32kopposite the deflector surface32h. In this embodiment, the deflector surfaces32h,32kmeet at the downstream boundary32jso as to form a vertex of the deflector32g. In other embodiments, the deflector surfaces32h,32kmay be spaced away from one another.

Referring toFIG. 3the first turbine22is shown in more detail. The first turbine22may include a first disc22b, the washer32, disc covers34, a first nut36and a second nut38. The first disc22bhas a first hub defining opposite ends of the first disc22b. The first hub22cdefines a first disc bore22dbetween its opposite ends. A first web22eextends generally radially from the first hub22cto a blade22f(not shown in detail) of the first disc22b. An upstream hub portion is disposed around the first shaft22awhereas a downstream hub portion is cantilevered relative to the first shaft22a. An upstream cover34aand a downstream cover34bmay be disposed on either sides of the first disc22band fastened to the upstream and downstream hub portions, respectively.

The first nut36is disposed downstream of the first disc22band joined thereto. For example, the first nut36may be fastened to the downstream hub portion of the first disc22b. The first nut36has an outer, circumferential wall36aand opposite upstream and downstream sides as delimited by a transverse nut wall36b. Upstream and downstream outer bores36c,36dof the first nut36extend coaxially from either sides of the first nut36toward the transverse nut wall36bthereof. An inner bore36eof the first nut36coaxial with the outer bores36c,36dextends through the transverse nut wall36b.

The first nut36is shown in a fastened position relative to the first disc22b. A downstream end of the first hub22cis received by the upstream outer bore36c, to which the first nut36is fastened via threading. The downstream cover34band the first nut36may be successively disposed downstream of the first web22esuch that the downstream cover34bis fastened to the first disc22bby the first nut36. The first nut36is screwed relative to the first hub22csuch that an annular flange34cof the downstream cover34bis held between the upstream side of the first nut36and a shoulder of the first hub22c. The first nut36may be configured such that in the fastened position, the transverse nut wall36bis spaced away from the downstream end of the first hub22c.

The first nut36may be configured so as to be engageable with the washer32via its downstream side. For instance, the transverse nut wall36dmay be shaped so as to define a socket36fat the bottom of the downstream outer bore36dadjacent the inner bore36e. The socket36fmay be sized for receiving the annular ridge32fof the washer32. The first nut36may have one or more first slots36gdisposed downstream of the socket36fand outward from the downstream outer bore36d. The one or more first slots36gmay have a shape complementary to that of the one or more first keys36cof the washer32so as to be engageable therewith. The first nut36may be configured to engage with the washer32via the one or more first slots36gupon rotation about the axis12, to hence block rotation of the assembly. Any one of the first slots36gof the first nut36may be engageable with any one of the first keys32cof the washer32.

The second nut38has a downstream nut portion38aand an upstream nut portion38bopposite the downstream nut portion38a. The second nut38may be configured so as to interface with the first nut36via the downstream nut portion38a. For example, the downstream nut portion38amay have a periphery38chaving a shape generally matching that of the socket36fof the first nut36so as to be receivable thereby. The periphery38cmay be circumscribed by a diameter greater than that of the inner bore36eof the first nut36. The upstream nut portion38bmay be circumscribed by a diameter lesser than that of the inner bore36e. Thus, the second nut38may interface with the first nut36upon the upstream nut portion38bbeing inserted through the inner bore36eand upon the downstream nut portion38abeing received by the socket36f.

The second nut38may be configured so as to be engageable with the washer32via its downstream nut portion38a. For example, the second nut38may have an anti-rotational feature, such as one or more keys38dinward of the periphery38c. The one or more keys38dmay have a shape complementary to that of the one or more second keying features of the washer32so as to be engageable therewith. Any one of the keys38dof the second nut38may be engageable with any one of the slots32eof the washer32.

The second nut38may be configured so as to be fastenable with the first shaft22avia its upstream nut portion38bupon its downstream nut portion38abeing disposed downstream of the first disc bore22dand the first shaft22abeing disposed inside the first disc bore22d. For example, the upstream nut portion38bmay be circumscribed by a diameter lesser than that of the first disc bore22aand may have a length corresponding to a distance between opposite ends of the upstream and downstream hub portions. The second nut38is shown in a fastened position relative to the first shaft22a, the first disc22aand the first nut36. In this position, the downstream nut portion38ais received by the socket36f. The second nut38extends from the downstream nut portion38athrough the inner bore36eto its upstream nut portion38bdisposed inside the first disc bore22a. The upstream nut portion38bis fastened to the first shaft22avia threading. The second nut38is screwed relative to the first shaft22asuch that an annular flange22gof the upstream hub portion is held between an upstream side of the second nut38and a downstream-facing shoulder of the first shaft22a. The second nut38is configured such that in the fastened position, the second nut38is coaxial with the first shaft22aand the first disc bore22d. The second nut38may also be configured such that a peripheral surface38eupstream of its downstream portion38aforms a gap39relative to the inner bore36eof the first nut36upon the nuts36,38being in their respective fastened positions, the gap39forming a portion of the first flow path44(e.g., of annular shape considering the annularity of the components defining the flow path44). The nuts36,38may be structured and arranged relative to one another such that dimensions of the gap39remain within desirable ranges despite thermal deformation occurring as the engine10is operated under certain conditions. As such, the gap39may be said to be a controlled gap.

The washer32is shown in an engaged position (i.e., in this case, a keyed position) relative to the first and second nuts36,38. In the engaged position, the washer32may be coaxial with the first and second nuts36,38and the washer axis may be collinear with the axis12of the engine10. Further, rotation of either the first nut36or the second nut38about the axis12relative to the first disc22bmay be blocked by the first and second nuts36,38and the washer32being in the engaged position. Indeed, the threading which fastens the first nut36and the threading which fastens the second nut38may be of an opposite handedness. The washer32being rotationally engaged with both nuts36,38may thus prevent the nuts36,38from rotating about the axis12relative to the first disc22b, either with one another or independently. Further, upon mounting the first disc22babout the first shaft22a, fastening the first nut36to the first disc22b, and fastening the second nut38to the first shaft22a, placing the washer32in the engaged position may block any movement between the first disc22band the first shaft22a. The first disc22b, the disc covers34, and the nuts36,38may be said to form a first turbine assembly, of which the washer32may block rotation relative to the first shaft22aabout the axis12.

A retaining ring40may be disposed downstream of the washer32about the axis12. The retaining ring40may be configured so as to hinder translation of the washer32along the axis12relative to the first nut36. For example, upon the washer32being in the engaged position, the retaining ring40may be joined to the first nut36(for example via retention in a circumferential groove surrounding the downstream outer bore36cor via friction) so as to retain the washer32in position relative to the first nut36.

Still referring toFIG. 3, annular gaps in serial flow communication are formed around the second nut38relative to the first disc bore22aand to the inner nut bore36e, respectively. The annular gaps are in fluid communication with upstream and downstream interior spaces40,42of the turbine section20via a first inlet44aof the upstream hub portion and a first outlet44bof the downstream nut portion38a, defining a first flow path44of the first turbine22therebetween. The upstream interior space40is heated due to thermal energy transferred from the combustion section18. As such, a first flow44c(FIG. 4) of air flowed from the upstream interior space40and throughout the first flow path44is substantially hot.

The keys38dof the second nut38may be disposed outward of the first outlet44brelative to the axis12such that upon engagement of the one or more slots32etherewith, the annular ridge32dis clear of the first flow44c. The keys38dmay be configured such that upon engagement of the one or more slots32etherewith, the deflector36gis positioned downstream of the first flow path44so as to faces the first flow44c. The downstream nut portion38amay be configured to rotationally engage with the washer32via the keys38dupon rotation about the axis12.

A second flow path46of the first turbine22is defined by annular gaps in serial flow communication formed around the second shaft24arelative to an interior wall of the first shaft22aand an interior wall of the second nut38, respectively. The second flow path46is in fluid communication with an interior space of the compressor section16via a second inlet46a(FIG. 1) and with the downstream interior space42via a second outlet46b. The second outlet46bis formed in part by the downstream nut portion38aand located radially inward of the first outlet44b. The interior space of the compressor section16being at a temperature generally greater than ambient temperature and lesser than a second impeller temperature downstream of the second impeller30. Thus, a second flow46c(FIG. 4) of air flowed from the compressor section16and throughout the second flow path44is generally colder relative to the first flow44c. The second impeller temperature may for example be inside a diffuser conduit30ain downstream serial flow communication with the second impeller30. The interior space of the compressor section16may be heated up via the diffuser conduit30ayet remain relatively cooler due to thermal losses via other adjacent media disposed between the compressor section16and an environment exterior to the engine10.

Turning now toFIG. 4, a configuration of the washer32for redirecting the first flow44ctoward the second flow46cwill be described. A portion of the upstream interior space42located radially inward of the first hub22cand of a second hub24cof the second disc22bdefines a gap42a. With the washer32in the engaged position, its deflector32gis disposed inside the gap42a. The washer32is configured such that, in the engaged position, the deflector32gforms a third flow path in fluid communication with the first flow path44cand directed toward the second flow path46c. The deflector surface32his shaped to redirect a flow toward a desired location. Indeed, the upstream deflector surface32hredirects the first flow44ctoward the second flow46csuch that the flows44c,46ccross at the desired location represented by intersection42b. Deflection of the first flow44cresults in a mixed flow50flowing downstream from the intersection42b. The mixed flow50has a temperature between that of the first and second flows44c,46c. Hence, thermal gradients in portions of the first and second turbines22located downstream of the intersection42bmay be desirably reduced upon exposure to the mixed flow50. Reduction of thermal gradients and corresponding thermal stresses in such turbine components may, under certain circumstances, desirably increase a lifespan of such turbine components. Thus, the washer32is configured such that the intersection is located inside the gap42aand upstream of some such turbine components. For example, in this embodiment, the washer32is configured such that the intersection42bis located upstream of an inlet52aof a fourth flow path52defined by the second turbine24, such that a portion of the mixed flow50may flow through the fourth flow path52.

With reference toFIG. 5a method60of redirecting the first flow44cin the gas turbine engine10will now be described.

The method60starts at step62with directing the first flow44cfrom the first flow path44of the first turbine disc22bto downstream thereof along the axis12. In some embodiments, the method60may provide controlling at least one of a flow rate and a temperature of the first flow44cupstream of the first turbine disc22b. The flow rate and the temperature may respectively be controlled to be at a predetermined value or within a predetermined range of values.

From step62, the method60goes to step64with directing the second flow46cfrom the second flow path46of the first turbine disc22binward the first flow path44to downstream thereof along the axis12. In some embodiments, the method60may provide controlling at least one of a flow rate and a temperature of the second flow46cupstream of the first turbine disc22b. The flow rate and the temperature may respectively be controlled to be at a predetermined value or within a predetermined range of values.

From step64, the method60goes to step66with deflecting the first flow44cdownstream of the first turbine disc22bto direct the first flow44ctoward the second flow46cdownstream of the first turbine disc22b. In some embodiments, the method60may provide deflecting the first flow44cupstream of the gap42aprior to deflecting the first flow44cdownstream of the first turbine disc22b.

In some embodiments, the method60further comprises mixing the first flow44cand the second flow46cinto the mixed flow50at the intersection42blocated downstream of the first turbine disc22bupon deflecting the first flow44c.

In some such embodiments, the intersection42bis located in the gap42adefined between the first turbine disc22band the second turbine disc24bdownstream of the first turbine disc22b. The intersection42bmay be located upstream of the inlet52aof the flow path52defined by the second turbine24.

In some embodiments, the method60further comprises placing a washer having a deflector such as the deflector32gdownstream of the first turbine disc22bsuch that its deflector faces the first flow44cto deflect the first flow44c. In some such embodiments, the washer may have no first and second keying features such as the keys32cand the slots32eprovided that the deflector remains positioned so as to face the first flow44cto deflect the first flow44cupon operating the engine10.

In some embodiments, the method60further comprises placing the washer32downstream of the first turbine disc22bsuch that the deflector32gfaces the first flow44cto deflect the first flow44c.

In some such embodiments, the method60further comprises removing an existing key washer from downstream of the first turbine disc22bprior to placing the washer32downstream of the first turbine disc22b. The existing key washer may have no deflector such as the deflector32g, and may be keyed relative to the first turbine disc22band to the first shaft22a.

In some embodiments, the method60further comprises controlling the deflection of the first flow44cto redirect the first flow44cfrom toward the location of the intersection42bto toward a desired location downstream of the first turbine disc22b. Thus, the first flow44cand the second flow46cmay be mixed into the mixed flow50at the desired location. For example, one may control the deflection of the first flow44cby replacing a first washer having a first deflector configured for directing the first flow44ctoward the location of the intersection42bwith a second washer having a second deflector configured for directing the first flow44ctoward the desired location.