Patent Application
20130014512
The disclosure relates to turbine engine combustors. More particularly, the disclosure relates to vane rings.
Ceramic matrix composite (CMC) materials have been proposed for various uses in high temperature regions of gas turbine engines.
US Pregrant Publication 2010/0257864 of Prociw et al. discloses CMC use in duct portions of an annular reverse flow combustor. US Pregrant Publication 2009/0003993 of Prill et al. discloses CMC use in vanes.
One aspect of the disclosure involves a combustor/vane assembly having an outer support ring (e.g., metallic), an inner support ring (e.g., metallic), an outer liner ring (e.g., CMC), an inner liner ring (e.g., CMC), and a circumferential array of vanes. Each vane has a shell (e.g., CMC) extending from an inboard end to an outboard end and at least partially through an associated aperture in the inner liner ring and an associated aperture in the outer liner ring. There is at least one of: an outer compliant member compliantly radially positioning the vane; and an inner compliant member compliantly radially positioning the vane.
In various implementations, the outer compliant member may be between the outboard end and the outer support ring; and the inner compliant member may be between the inboard end and the inner support ring. Each vane may further comprise a tensile member extending through the shell and coupled to the outer support ring and inner support ring to hold the shell under radial compression. Each tensile member may comprise a rod extending through associated apertures in the outer support ring and inner support ring. Each inner compliant member or outer compliant member may comprise a canted coil spring. Each canted coil spring may lack a seal body energized by the spring. Each canted coil spring may be at least partially received in a recess in the inner support ring or outer support ring.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
The turbofan engine has an upstream fan 40 receiving the inlet air flow 26. Downstream of the fan along the core flowpath 30 are, in sequential order: a low pressure compressor (LPC) section 42; a high pressure compressor (HPC) section 44; a combustor 46; a gas generating turbine or high pressure turbine (HPT) section 48; and a low pressure turbine (LPT) section 50. Each of the LPC, HPC, HPT, and LPT sections may comprise one or more blade stages interspersed with one or more vane stages. The blade stages of the HPT and HPC are connected via a high pressure/speed shaft 52. The blade stages of the LPT and LPC are connected via a low pressure/speed shaft 54 so that the HPT and LPT may, respectively, drive rotation of the HPC and LPC. In the exemplary implementation, the fan 40 is also driven by the LPT via the shaft 54 (either directly or via a speed reduction mechanism such as an epicyclic transmission (not shown)).
The combustor 46 receives compressed air from the HPC which is mixed with fuel and combusted to discharge hot combustion gases to drive the HPT and LPT. The exemplary combustor is an annular combustor which, subject to various mounting features and features for introduction of fuel and air, is generally formed as a body of revolution about the axis 500.
A downstream portion 90 of the inboard wall structure 72 is formed by an inner support ring 92 and an inner liner ring 94 outboard thereof (between the inner support ring and the main interior portion 94 of the combustor). The outboard wall structure 74, similarly, comprises an outer support ring 96 and an outer liner ring 98 inboard thereof. There is, thus, an inner gap 140 between the inner support ring and inner liner ring and an outer gap 142 between the outer support ring and outer liner ring.
The inner support ring 92 extends from a forward/upstream end/rim 100 to a downstream/aft end/rim 102 and has: a surface 104 which is an outer or exterior surface (viewed relative to the combustor interior 144) but is an inboard surface (viewed radially); and a surface 106 which is an inner or interior surface but an outboard surface. Similarly, the inner liner ring 94 has a forward/upstream end/rim 110, a downstream/aft end/rim 112, an inboard surface 114, and an outboard surface 116. Similarly, the outer support ring 96 has a forward/upstream end/rim 120, a downstream/aft end/rim 122, an inboard surface 124 (which is an inner/interior surface), and an outboard surface 126 (which is an outer/exterior surface). Similarly, the outer liner ring 98 has an upstream/forward end/rim 130, a downstream/aft end/rim 132, an inboard surface 134, and an outboard surface 136.
Exemplary support rings 92 and 96 are metallic (e.g., nickel-based superalloys). Exemplary liners are formed of CMCs such as silicon carbide reinforced silicon carbide (SiC/SiC) or silicon (Si) melt infiltrated SiC/SiC (MI SiC/SiC). The CMC may be a substrate atop which there are one or more protective coating layers or adhered/secured to which there are additional structures. The CMC may be formed with a sock weave fiber reinforcement including continuous hoop fibers.
Each of the exemplary vanes comprises a shell 180. The exemplary shell may be formed of a CMC such as those described above for the liners. The exemplary shell extends from an inboard end (rim) 182 to an outboard end (rim) 184 and forms an airfoil having a leading edge 186 and a trailing edge 188 and a pressure side 190 and a suction side 192 (
In operation, with operating temperature changes, there will be differential thermal expansion between various components, most notably between the CMC components and the metallic components. As temperature increases, the metallic support rings 92 and 96 will tend to radially expand so that their spacing may expand at a different rate and/or by a different ultimate amount than the radial dimension of the shell. An exemplary metal support ring has approximately three times the coefficient of thermal expansion as the CMC shell. However, in operation, the exemplary CMC shell is approximately three times hotter than the metal shell (e.g., 2.5-4 times). Thus, the net thermal expansion mismatch can be in either direction. This may cause the gaps 200 and 202 between the respective inboard end and outboard end of the shell and the adjacent surfaces 106 and 124 to expand or contract.
Accordingly, radially compliant means may be provided at one or both of the ends of the shell. The exemplary implementation involves radially compliant members 210 and 212 at respective inboard ends and outboard ends of the shells 180. For each vane, the exemplary member 210 is between the inboard end 182 and the support ring 92 whereas the exemplary member 212 is between the outboard end 184 and the support ring 96. The exemplary members 210 and 212 respectively circumscribe the associated ends 182 and 184 and are respectively at least partially accommodated in recesses 214, 216 in the associated surfaces 106, 124. The exemplary members 210 and 212 are held under compression. Exemplary means for holding the members 210 and 212 under compression comprise tensile members 220 (e.g., threaded rods) extending through the shell 180 from end to end and also extending through apertures 222 and 224 respectively in the support rings 92 and 96. End portions of the rods 220 may bear nuts or other fastening means to radially clamp the support rings 92 and 96 to each other and hold the shell 180 and members 210, 212 in radial compression.
Exemplary members 210 and 212 are canted coil springs. These are compressed transverse to the spring coil axis/centerline. Canted coil springs are commonly used for energizing seals. The canted coil spring provides robustness and the necessary spring constant for a relatively compliant or conformable seal material. However, by using the canted coil spring in the absence of the seal material (e.g., with each turn of the spring contacting the two opposing surfaces (vane rim and support ring)), an air flowpath may be provided through the spring (between turns of the spring) while allowing cooling air to pass into or out of the airfoil shell. As is discussed further below, this allows air to pass from the spaces 140, 142 through the canted coil springs and radially through the ends 182 and 184 into the vane interior 196 and, therefrom, out the outlets 194. Canted coil springs provide a relatively constant compliance force over a relatively large range of displacement compared with normal (axially compressed) coil springs of similar height. The exemplary canted coil spring materials are nickel-based superalloys. Alternative radially compliant members are wave springs (e.g., whose planforms correspond to the shapes of the adjacent vane shell ends 182, 184). Such wave springs may similarly be formed of nickel-based superalloys. As long as such a spring is not fully flattened, air may flow around the wave. Additionally, grooves or other passageways may be provided in the vane shell rims to pass airflow around the springs.
Other considerations attend the provision of the cooling airflows to pass through the canted coil springs. The exemplary bulkhead bears a circumferential array of nozzles 240 having air inlets 242 for receiving an inlet airflow 244 and having outlets 246 for discharging fuel mixed with such air 244 in a mixed flow 248 which combusts.
In a rich-quench-lean combustor, dilution air is introduced downstream.
The rings 260, 262 may have further passageways for introducing air to the spaces 140 and 142 and, forward thereof, the space 280 between a CMC inner layer 282 of the dome structure and a metallic outer layer 284. The inner layer 282 combines with the liner rings 94 and 98 to form a liner of the combustor; whereas the outer layer 284 combines with the support rings 92 and 96 to form a shell of the combustor.
In the exemplary implementation, the inner ring 260 has a passageway 320 for admitting an airflow 322 to the space 140 (becoming an inner airflow within/through the space 140). The passageways 320 each have an inlet 324 and an outlet 326. The exemplary inlets 324 are along the inboard face of the ring 260, whereas the outlets 326 are along its aft/downstream face. Similarly, the outboard ring 262 has passageways 350 passing flows 352 (becoming an outer airflow) into the space 142 and having inlets 354 and outlets 356. The exemplary inlets 354 are along the outboard face of the ring 262 and exemplary outlets 356 are along the aft/downstream face. Part of the flows 322, 352 pass through the respective canted coil springs 210, 212 as flows 360, 362. The remainder passes around the shells and passes toward the downstream end of the respective space 140, 142 which is blocked by a compliant gas seal 370, 372. Holes 374, 376 are provided in the liner rings 94, 98 to allow these remainders 378, 380 to pass into the downstream end of the combustor interior 144 downstream of the vanes.
The exemplary implementation, however, asymmetrically introduces air to the space 280. In the exemplary implementation, air is introduced through passageways 390 in the outboard ring 262 and passed into the combustor interior via passageways 392 in the inboard ring 260. This airflow 394 thus passes radially inward through the space 280 initially moving forward/upstream until it reaches the forward end of the space and then proceeding aft. This flow allows backside cooling of the CMC liner and entry of the cooling air into the combustion flow after this function is performed. Thus, in operation, the inner CMC liner handles the majority of thermal loads and stresses and the outer metal shell/support handles the majority of mechanical loads and stresses while cooling air flowing between these two controls material temperatures to acceptable levels.
One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when implemented in the remanufacture of the baseline engine or the reengineering of a baseline engine configuration, details of the baseline configuration may influence details of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.
