Patent Description:
Gas turbine engines are known, and typically include a fan delivering air into a bypass duct as propulsion air. Air is also delivered into a compressor where it is compressed and delivered into a combustor. In the combustor the air is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. The turbine rotors drive the fan and compressor rotors.

As is known, the turbine section of a gas turbine engine sees very high temperatures. As such, various steps are taken to ensure components in the turbine section can survive the high temperatures. One recent development is the use of ceramic matrix composites ("CMC") for components in the turbine section. One such component is a stator vane, which are mounted circumferentially spaced in rows that are axially intermediate rotating turbine blade rows.

A CMC vane typically has an internal metal spar providing additional structural support. An outer surface of the spar defines a cooling air flow path in combination with an inner surface of a cooling channel in the CMC stator body.

A prior art gas turbine engine stator vane combination, having the features of the preamble of claim <NUM>, is disclosed in <CIT>. Further prior art stator vane combinations are disclosed in <CIT>, <CIT> and <CIT>.

In an aspect of the present invention, a gas turbine engine stator vane combination is provided, as claimed in claim <NUM>.

In an embodiment, the stator vane body has platforms at each of two radial ends of the airfoil, and the spar extends through the cooling air channel and beyond each of the platforms.

In another embodiment according to any of the previous embodiments, the spar has a leading (front) edge end, a trailing (aft) edge end, a suction wall face and a pressure wall face all associated with corresponding structure on the stator vane body. A first axial distance is defined between the front edge end and the aft edge end of the spar. A second axial distance is defined between the leading edge of the stator vane body and the trailing edge of the stator vane body and the first distance being between <NUM> and <NUM>% of the second distance.

In another embodiment according to any of the previous embodiments, there are enlarged surface portions formed in the cooling air path to further provide a reduction in cross-sectional area of the cooling air path at localized areas.

In another embodiment according to any of the previous embodiments, the enlarged surface portions are formed on the inner peripheral surface of the stator vane body.

In another embodiment according to any of the previous embodiments, the enlarged surface portions are formed on the outer peripheral surface of the spar.

In another embodiment according to any of the previous embodiments, the enlarged surface portions have ramped portions leading from thinner portions into thicker portions to vary the cross-sectional area.

In another embodiment according to any of the previous embodiments, the enlarged surface portions have discrete steps to change the cross-sectional area.

In another embodiment according to any of the previous embodiments, the enlarged surface portions are formed on the inner surface of the stator vane body.

In another embodiment according to any of the previous embodiments, there are enlarged surface portions formed in the cooling air path to provide a reduction in cross-sectional area of the cooling air path at localized areas.

In another embodiment according to any of the previous embodiments, the enlarged portions have ramped portions leading from thinner portions into thicker portions to vary the cross-sectional area.

In another embodiment according to any of the previous embodiments, the enlarged portions have discrete steps to change the cross-sectional area.

In another aspect of the present invention, a gas turbine engine is provided, as claimed in claim <NUM>.

The fan section <NUM> may include a single-stage fan <NUM> having a plurality of fan blades <NUM>. The fan blades <NUM> may have a fixed stagger angle or may have a variable pitch to direct incoming airflow from an engine inlet. The fan <NUM> drives air along a bypass flow path B in a bypass duct <NUM> defined within a housing <NUM> such as a fan case or nacelle, and also drives air along a core flow path C for compression and communication into the combustor section <NUM> then expansion through the turbine section <NUM>. A splitter <NUM> aft of the fan <NUM> divides the air between the bypass flow path B and the core flow path C. The housing <NUM> may surround the fan <NUM> to establish an outer diameter of the bypass duct <NUM>. The splitter <NUM> may establish an inner diameter of the bypass duct <NUM>. The engine <NUM> may incorporate a variable area nozzle for varying an exit area of the bypass flow path B and/or a thrust reverser for generating reverse thrust.

The inner shaft <NUM> is connected to the fan <NUM> through a speed change mechanism, which in the exemplary gas turbine engine <NUM> is illustrated as a geared architecture <NUM> to drive the fan <NUM> at a lower speed than the low speed spool <NUM>. The inner shaft <NUM> may interconnect the low pressure compressor <NUM> and low pressure turbine <NUM> such that the low pressure compressor <NUM> and low pressure turbine <NUM> are rotatable at a common speed and in a common direction. In other embodiments, the low pressure turbine <NUM> drives both the fan <NUM> and low pressure compressor <NUM> through the geared architecture <NUM> such that the fan <NUM> and low pressure compressor <NUM> are rotatable at a common speed. Although this application discloses geared architecture <NUM>, its teaching may benefit direct drive engines having no geared architecture.

The low pressure compressor <NUM>, high pressure compressor <NUM>, high pressure turbine <NUM> and low pressure turbine <NUM> each include one or more stages having a row of rotatable airfoils. Each stage may include a row of vanes adjacent the rotatable airfoils. The rotatable airfoils are schematically indicated at <NUM>, and the vanes are schematically indicated at <NUM>.

The engine <NUM> may be a high-bypass geared aircraft engine. The bypass ratio can be greater than or equal to <NUM> and less than or equal to about <NUM>, or more narrowly can be less than or equal to <NUM>. The geared architecture <NUM> may be an epicyclic gear train, such as a planetary gear system or a star gear system. The epicyclic gear train may include a sun gear, a ring gear, a plurality of intermediate gears meshing with the sun gear and ring gear, and a carrier that supports the intermediate gears. The sun gear may provide an input to the gear train. The ring gear (e.g., star gear system) or carrier (e.g., planetary gear system) may provide an output of the gear train to drive the fan <NUM>. A gear reduction ratio may be greater than or equal to <NUM>, or more narrowly greater than or equal to <NUM>, and in some embodiments the gear reduction ratio is greater than or equal to <NUM>. The fan diameter is significantly larger than that of the low pressure compressor <NUM>. The low pressure turbine <NUM> can have a pressure ratio that is greater than or equal to <NUM> and in some embodiments is greater than or equal to <NUM>. All of these parameters are measured at the cruise condition described below.

The flight condition of <NUM> Mach and <NUM>,<NUM> ft (<NUM>,<NUM> meters), with the engine at its best fuel consumption - also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')" - is the industry standard parameter of Ibm of fuel being burned divided by Ibf of thrust the engine produces at that minimum point. The engine parameters described above, and those in the next paragraph are measured at this condition unless otherwise specified.

"Fan pressure ratio" is the pressure ratio across the fan blade <NUM> alone, without a Fan Exit Guide Vane ("FEGV") system. A distance is established in a radial direction between the inner and outer diameters of the bypass duct <NUM> at an axial position corresponding to a leading edge of the splitter <NUM> relative to the engine central longitudinal axis A. The fan pressure ratio is a spanwise average of the pressure ratios measured across the fan blade <NUM> alone over radial positions corresponding to the distance. The fan pressure ratio can be less than or equal to <NUM>, or more narrowly greater than or equal to <NUM>, such as between <NUM> and <NUM>. "Corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]<NUM>. The corrected fan tip speed can be less than or equal to <NUM> ft / second (<NUM> meters/second), and can be greater than or equal to <NUM> ft / second (<NUM> meters/second).

<FIG> shows a stator vane body <NUM> and an internal spar <NUM> as a combined element <NUM>. Stator vanes typically include platforms <NUM> and <NUM> at opposed ends of an airfoil <NUM>. Applicant has discovered that the heating load on the airfoil <NUM> is not uniform, and may be highest adjacent a midspan <NUM>.

The stator vane body <NUM> may be formed of ceramic matrix composites ("CMCs").

In embodiments, the ceramic matrix components could be formed of CMC material or a monolithic ceramic. A CMC material is comprised of one or more ceramic fiber plies in a ceramic matrix. Example ceramic matrices are silicon-containing ceramic, such as but not limited to, a silicon carbide (SiC) matrix or a silicon nitride (Si3N4) matrix. Example ceramic reinforcement of the CMC are silicon-containing ceramic fibers, such as but not limited to, silicon carbide (SiC) fiber or silicon nitride (Si3N4) fibers. The CMC may be, but is not limited to, a SiC/SiC ceramic matrix composite in which SiC fiber plies are disposed within a SiC matrix. A fiber ply has a fiber architecture, which refers to an ordered arrangement of the fiber tows relative to one another, such as a 2D woven ply or a 3D structure. A monolithic ceramic does not contain fibers or reinforcement and is formed of a single material. Example monolithic ceramics include silicon-containing ceramics, such as silicon carbide (SiC) or silicon nitride (Si3N4).

As mentioned above, there is a cooling channel <NUM> that receives cooling air from a source <NUM> such as a compressor section in the <FIG> engine. The air is delivered through conduits <NUM> into a cooling channel <NUM> and, optionally, into a second cooling channel <NUM>. Of course, additional cooling channels may be used. The internal spar <NUM> may be formed of an appropriate metal, and provides additional structural ability to the combination <NUM>. As shown, the spar <NUM> has a remote end <NUM> which extends beyond the platform <NUM>. An outer surface <NUM> of the spar <NUM> is generally shaped as an airfoil.

Spar <NUM> is illustrated in a schematic manner to show the cooling features. The actual spar may itself have internal cooling passages. Further, its outer shape may differ. Also, some attachment structure will typically be included.

<FIG> shows the cooling channels <NUM> and <NUM> extending through the stator vane body <NUM>.

<FIG> shows a cross-section through the combination <NUM>. In particular, the spar <NUM> has its outer surface <NUM> spaced away from an inner surface <NUM> of the stator vane body <NUM>. Between the surfaces <NUM> and <NUM> a cooling air path is defined.

The stator vane body <NUM> has a leading edge <NUM> and a trailing edge <NUM>. Spar <NUM> has a front edge <NUM> and an aft edge <NUM>. In an embodiment, a length measured between the front edge <NUM> and aft edge <NUM> is greater than or equal to <NUM>% and less than or equal to <NUM>% of a distance measured between leading edge <NUM> and trailing edge <NUM>. In other embodiments it may be greater than or equal to <NUM>% and less than or equal to <NUM>% of the distance. In further embodiments, it may be greater than or equal to <NUM>% and less than or equal to <NUM>% of the distance.

As mentioned above, Applicant has recognized that the cooling load is not constant along the surfaces <NUM> or <NUM>. Applicant also has recognized that there may be localized hot spots especially adjacent a midspan location <NUM>.

<FIG> shows a combination <NUM> with structure to "focus" cooling on localized areas that are most in need. As shown, the spar <NUM> has a front edge that varies in thickness from a relatively small portion <NUM> to a ramped portion <NUM> that leads to an enlarged area <NUM>, and back to a ramped portion <NUM> that leads to the end <NUM> of the spar <NUM>. The aft edge has a similar series of changes in its length.

<FIG> shows the combination <NUM>, and the spar <NUM> also having similarly small outer portions <NUM> leading into a ramped portion <NUM>, and enlarged portion <NUM>, another ramped portion <NUM> and a smaller end portion <NUM>. While this is shown on the suction side of the stator vane body <NUM> a similar shape would be found on the pressure side. As mentioned above, there is a cooling path defined between the outer surface of the spar <NUM> and an inner surface of the channel <NUM>.

<FIG> shows the front edge <NUM> and the aft edge <NUM> of the spar <NUM> through a section taking at the point where the thinner portion <NUM> merges into the ramped portion <NUM>. As can be appreciated, due to the ramped portions found along each of the pressure and suction sides, and adjacent the front and aft edges, the cross-sectional area defined between the outer surface of the spar <NUM> and the inner surface <NUM> of the channel <NUM> will decrease as the cooling air moves toward a midspan region. This will increase the velocity of the air flow, and result in more concentrated cooling along this midspan portion.

<FIG> shows another embodiment <NUM> (outside the wording of the claims) where the spar <NUM> may have a relatively constant outer shape, but an inner surface <NUM> of the channel <NUM> has ridges or steps <NUM>, <NUM>, <NUM> and <NUM> formed along the suction side, leading edge, pressure side and trailing edge, respectively.

As can be seen in <FIG>, the steps or ramps <NUM> will decrease the cross-sectional area of the flow adjacent a midspan area <NUM> by having a ramp portion <NUM> leading into thicker portions <NUM> and <NUM>, and to another ramp <NUM>.

As shown in <FIG>, the ridges or steps <NUM> need not be spaced by a constant axial distance. Instead, there is a greater axial distance between adjacent ramps <NUM> as shown at <NUM> compared to a distance shown at <NUM> between the ridges or steps <NUM>. This can allow further tailoring of the cooling air flow to specific areas.

<FIG> shows an alternative embodiment (outside the wording of the claims) wherein the ridges or steps <NUM> are formed by a plurality of discrete incremental steps <NUM>/<NUM>/<NUM>/<NUM> away from the inner surface <NUM>. This is in contrast to the ramped increases as shown in <FIG>. It may be easier to manufacture such a shape on the CMC stator body <NUM>.

<FIG> shows an embodiment <NUM> having a stator vane body <NUM> where the spar <NUM> again has the surfaces <NUM>/<NUM>/<NUM>/<NUM>/<NUM> adjacent both the front edge and an aft edge.

<FIG> shows that the combination <NUM> includes surfaces on the spar <NUM> such as previously described in <FIG>, and in particular surfaces <NUM>/<NUM>/<NUM>/<NUM> and <NUM>.

However, as shown in <FIG>, the spar <NUM> has additional ridges or steps <NUM> similar to those found in the embodiment of <FIG>, but now on the spar <NUM>. As can be seen in <FIG>, the steps <NUM> have a chevron shape with a ramped portion <NUM> leading into a thicker portion <NUM> and then into another ramp portion <NUM> such that the flow cross-section varies along a length of the spar <NUM>.

<FIG> shows yet another embodiment <NUM> which essentially combines a spar <NUM> which may be similar to the <FIG> spar. In addition, a stator vane body <NUM> has ridges or steps <NUM> extending from an inner surface <NUM>.

<FIG> shows the steps <NUM> on the body <NUM>, and again show the ramps <NUM> leading into outwardly extending sections <NUM>, inwardly extending sections <NUM> and another ramped portion <NUM>. Essentially, this embodiment combines the features of the <FIG> and <FIG>.

Now, the several embodiments can be utilized to provided localized cooling to an area of the stator vane body which is most in need of cooling airflow.

While embodiments have been disclosed, a worker of skill in this art would recognize that modifications within the scope of this invention.

Claim 1:
A gas turbine engine stator vane combination (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising:
a stator vane body (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) having an airfoil (<NUM>) with a leading edge (<NUM>), a trailing edge (<NUM>), a suction side and a pressure side, and having at least one internal cooling air channel (<NUM>), said stator vane body (<NUM>...<NUM>) being formed of ceramic matrix composite materials;
a spar (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) received within said at least one cooling air channel (<NUM>) and formed of a metal, and said spar (<NUM>...<NUM>) having an outer peripheral surface (<NUM>) spaced from an inner peripheral surface (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) of the cooling air channel (<NUM>) to define a cooling air path, with said cooling air path having a varying cross-sectional area through the cooling air channel (<NUM>),
characterised in that:
said variable cross-sectional area is achieved by said spar (<NUM>...<NUM>) having a variation in said outer peripheral surface (<NUM>), with a first thinner portion (<NUM>; <NUM>) leading into an outwardly first ramped portion (<NUM>, <NUM>) at each of a leading edge end (<NUM>; <NUM>), trailing edge end (<NUM>; <NUM>), suction wall face and pressure wall face of said spar (<NUM>...<NUM>) to change the cross-sectional area; and
there is a second ramped portion (<NUM>, <NUM>) beyond said first ramped portion (<NUM>, <NUM>), and said second ramped portion (<NUM>, <NUM>) ramps back to a second thinner portion (<NUM>, <NUM>) such that the cross-sectional area of the cooling air path decreases at the first ramped portion (<NUM>, <NUM>) and increases at the second ramped portion (<NUM>, <NUM>).