Patent Application
20250116197
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-pressure and temperature core gas flow. The high-pressure and temperature core gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section may include low and high pressure compressors, and the turbine section may also include low and high pressure turbines.
Airfoils in the turbine section are typically formed of a superalloy and may include thermal barrier coatings to extend temperature capability and lifetime. Ceramic matrix composite (“CMC”) materials are also being considered for airfoils. Among other attractive properties, CMCs have high temperature resistance. Despite this attribute, however, there are unique challenges to implementing CMCs in airfoils.
An airfoil according to an example of the present disclosure includes an airfoil section that defines pressure and suction sides, a leading edge, and a trailing edge region including a trailing edge. The airfoil section is formed of a ceramic matrix composite that includes fiber plies disposed in a ceramic matrix. The fiber plies have core fiber plies that define a radial tube that circumscribes an internal cavity. The radial tube has a radiused end in the trailing edge region, and skin fiber plies define an exterior of the airfoil section and wrap around the core fiber plies from the pressure side of the trailing edge region, through the leading edge, and to the suction side of the trailing edge region. There is a filler element in the trailing edge region aft of the internal cavity and sandwiched between the skin fiber plies on the pressure side and the skin fiber plies on the suction side. At least one cooling passage has a first, inlet orifice section that opens to the internal cavity at a location forward of the radiused end and extends through the core fiber plies, and a second, outlet orifice section that extends through the trailing edge.
In a further embodiment of any of the foregoing embodiments, the at least one cooling passage includes a third, intermediate section connecting the first and second sections, and the third section is bound by at least one of the skin plies and the filler element.
In a further embodiment of any of the foregoing embodiments, the filler element includes a filler core and a filler skin ply on the filler core, and the filler skin ply partially bounds the third section.
In a further embodiment of any of the foregoing embodiments, the third section is bound by at least two of the skin plies.
In a further embodiment of any of the foregoing embodiments, the fiber plies include a number N of the core fiber plies each having a ply thickness t, and the location is forward of the radiused end by a distance D that is greater than the product of N, t, and a multiplier X that is from five to ten.
In a further embodiment of any of the foregoing embodiments, the location is toward the suction side of the core fiber plies.
In a further embodiment of any of the foregoing embodiments, the at least one cooling passage includes multiple cooling passages, for a first portion of the multiple cooling passages the location is toward the suction side of the core fiber plies, and for a second portion of the multiple cooling passages the location is toward the pressure side of the core fiber plies.
In a further embodiment of any of the foregoing embodiments, the multiple cooling passages each include a third, intermediate section connecting the first and second sections. The third section of the first portion of the multiple cooling passages extend adjacent the suction side between at least one of the skin plies and the filler element, and the third section of the second portion of the multiple cooling passages extending adjacent the pressure side between at least one of the skin plies and the filler element.
A gas turbine engine according to an example of the present disclosure includes a compressor section, a combustor in fluid communication with the compressor section, and a turbine section in fluid communication with the combustor. The turbine section has airfoils according to any of the foregoing embodiments.
Also disclosed is a method of fabricating an airfoil according to any of the foregoing embodiments.
In a further embodiment of any of the foregoing embodiments, prior to densifying, the core fiber plies and the skin fiber plies contain no ceramic matrix.
The present disclosure may include any one or more of the individual features disclosed above and/or below alone or in any combination thereof.
The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding elements. Terms such as “first” and “second” used herein are to differentiate that there are two architecturally distinct components or features. Furthermore, the terms “first” and “second” are interchangeable in that a first component or feature could alternatively be termed as the second component or feature, and vice versa.
The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, and the location of bearing systems 38 may be varied as appropriate to the application.
The low speed spool 30 generally includes an inner shaft 40 that interconnects, a first (or low) pressure compressor 44 and a first (or low) pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48 to drive a fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a second (or high) pressure compressor 52 and a second (or high) pressure turbine 54. A combustor 56 is arranged in the exemplary gas turbine 20 between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 may be arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 further supports bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded through the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path C. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may be varied. For example, gear system 48 may be located aft of the low pressure compressor, or aft of the combustor section 26 or even aft of turbine section 28, and fan 42 may be positioned forward or aft of the location of gear system 48.
The engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), and can be less than or equal to about 18.0, or more narrowly can be less than or equal to 16.0. The geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3. The gear reduction ratio may be less than or equal to 4.0. The low pressure turbine 46 has a pressure ratio that is greater than about five. The low pressure turbine pressure ratio can be less than or equal to 13.0, or more narrowly less than or equal to 12.0. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about five 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to an inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1 and less than about 5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.
A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10,668 meters). The flight condition of 0.8 Mach and 35,000 ft (10,668 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 lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. The engine parameters described above and those in this paragraph are measured at this condition unless otherwise specified. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45, or more narrowly greater than or equal to 1.25. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram° R)/(518.7° R)]0.5. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150.0 ft/second (350.5 meters/second), and can be greater than or equal to 1000.0 ft/second (304.8 meters/second).
The airfoil section 60 is formed of a ceramic matrix composite (CMC) 64. Referring to the cutaway section in
The fiber plies 66 include core fiber plies 68 and skin fiber plies 70. The core fiber plies 68 define a radial tube 72 that circumscribes and immediately borders the internal cavity 61. The skin fiber plies 70 define the exterior profile of the airfoil section 60 and wrap around the core fiber plies 68 from the pressure side 66d in the trailing edge region 63, through the leading edge 60a, and to the suction side 66c in the trailing edge region 63. In the illustrated example, there are four core fiber plies 68 and three skin fiber plies 70, although it is to be understood that the numbers of plies 68/70 can be varied.
The radial tube 72 has a radiused end 74 in the trailing edge region 63. Except for the inner-most one of the core fiber plies 68, all of the core fiber plies 68 wrap completely around the internal cavity 61. The inner-most one of the core fiber plies 68 terminates short of the radiused end 74, as the small radius may exceeds the capability of the ply to bend without fiber tow distress.
There is a filler element 76 in the trailing edge region 63 aft of the internal cavity 61. A filler element in general is often colloquially referred to as a “noodle” and serves as a non-structural space-filler, usually in an interstice where other fiber plies bend. Here, the filler element 76 fills in the region aft of the radiused end 74, sandwiched between the skin fiber plies 70 on the pressure side 66d and the skin fiber plies 70 on the suction side 66c. The filler element 76 may be formed of, but is not limited to, a bundle of densified ceramic fibers (a CMC) or a monolithic ceramic.
The sides 66c/66d and the trailing edge region 63 may require cooling. In that regard, the airfoil section 60 includes at least one cooling passage 78, but most typically a plurality of cooling passages 78, for a flow of cooling air. For example, the cooling air is bleed air from the compressor section 24 that is provided into the internal cavity 61 and flows from the internal cavity 61 into the cooling passage(s) 78. A sectioned view through one of the cooling passages 78 is shown in an enlarged view in
The radiused end 74 of the radial tube 72 is an area that may be under considerable stress in the airfoil section 60. For example, the core fiber plies 68 are under bending stresses from bending at the radius in the end 74, and dynamic stresses on the airfoil section 60 may concentrate at this area due to the bending. Such stresses on a CMC may tend to cause delamination between fiber plies. In this regard, the proposition of using an orifice in the radiused end is undesirable, as it would cause a discontinuity in the ceramic fibers and thereby potentially weaken the CMC in that area. Rather, the first section 78a of the passage 78 is at a location L that is axially forward of the radiused end 74, so as to circumvent the end 74 and thus avoid inclusion of a discontinuity in the end 74. For example, the radiused end 74 is demarked by a location P, at which the core fiber plies 68 begin to bend, and the location L is forward of location P. In one example, in order to provide a margin from the location P, the location L is positioned based on a number N of the core fiber plies 68 and a ply thickness t of the plies 68. For instance, the location L is forward of location P by a distance D (to the closest edge of the first section 78a) that is greater than the product of N and t. In a further example, in order to ensure an adequate margin from the location P, the distance is a multiple of N, t, and a multiplier X, where X is from five to ten.
The first section 78a extends through the core fiber plies 68. For example, the central axis of the first section 78a is locally substantially perpendicular to the core fiber plies 68 and the skin fiber plies 70, but could alternatively be at a non-perpendicular angle. The cooling passage 78 further includes a third, intermediate section 78c that opens on its forward end to the first section 78a and opens on its aft end to the second section 78b. The third section 78c is substantially straight and of uniform cross-section along its full length, though it could alternatively include turns and/or taper in cross-section upstream-to-downstream or diverge in cross-section upstream-to-downstream, and connects the first and second sections 78a/78b. In this example, each passage 78 has a single inlet (78a) and a single outlet (78b). The third section 78c is bound on its interior side by the filler element 76, on its outer side by one of the skin plies 70 (i.e., an intermediate ply between the inner-most and outer-most skin plies), and on its lateral sides by the inner-most one the skin plies 70.
Alternatively, as shown in
In further embodiments, the location L is substantially further forward of location P by a multiple of distance D. In such examples, the third section 78c is longer and thus runs over a longer distance along the suction side 66c (or pressure side 66d), thereby providing additional cooling of the side 66c (or 66d).
In the prior examples, the first section 78a (and thus the location L) is toward the suction side 66c of the core fiber plies 68 such that the third section 78c of the passage 78 runs along the suction side 66c. However, in additional examples, as depicted in dashed lines in
The disclosed methodology enables the passages 78/178 to be formed prior to densification. This not only eliminates a need for machining the passages into the final CMC but also enables enhanced densification of the CMC. For instance, densification depends to some extent on the ability of the matrix material or matrix precursor material (i.e., infiltrants) to flow into all depths of the preform during the densification process so that the preform becomes fully densified. In some cases, however, the thickness of the preform can exceed a depth at which the infiltrants can readily flow under practical processing conditions and times and achieve the desired density. As a result, the preform may be only partially densified in some regions, with pores or voids in the regions that the infiltrant cannot reach. The cutouts 80, slots 82, and though-slots 84 provide additional flow paths for the matrix material or matrix precursor material during densification and thereby can enhance densification in regions that may otherwise not be fully densified.
Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.
