Patent Application
20160348689
The present disclosure relates to gas turbine engines, and, more specifically, to a fan blade attachment root with an improved strain response to impact events.
Aircraft may collide with birds while in flight. In some instances, birds may collide with a gas turbine engine. In gas turbine engines having a fan, the fan blades may absorb the brunt of an impact. The impulse from impact may result in temporarily elevated strain in the fan blades. The area subjected to the increased strain may be the transition zone on the leading edge of the fan blade below the sheath. Stiff fan blades, for example, may be susceptible to damage at such area during an impact event.
A fan blade may include a leading edge, an attachment root extending aft of the leading edge, and a trench formed in a surface of the attachment root. In various embodiments, the trench may comprise a cylindrical trough and an end surface having a spherical geometry. The trench may further comprise a first sidewall and a second sidewall parallel to the first sidewall with the first sidewall and the second sidewall extending tangentially from the cylindrical trough. The trench may comprise a spherical recess. The trench may be offset from the leading edge. A height of the trench equals a width of the trench. An axial length of the trench may be at least half an axial length of the attachment root. The surface of the attachment root may comprise a bottom surface of a dovetail.
An attachment root may comprise a leading edge, a dovetail extending aft of the leading edge, and a trench formed in a surface of the dovetail. In various embodiments, the trench may comprise a cylindrical trough and an end surface having a spherical geometry. The trench may further comprise a first sidewall and a second sidewall parallel to the first sidewall with the first sidewall and the second sidewall extend tangentially from the cylindrical trough. The trench may comprise a spherical recess. The trench is offset from the leading edge. A height of the trench may equal a width of the trench. An axial length of the trench may be at least half an axial length of the attachment root.
A gas turbine engine may comprise a compressor section configured to rotate about an axis, a combustor aft of the compressor section and a turbine section aft of the compressor section and configured to rotate about the axis. A fan may be disposed forward of the turbine section and include a blade. The blade may have a trench formed in an attachment root.
In various embodiments, the blade may comprise a leading edge with the trench extending aft from the leading edge. The trench may comprise a cylindrical trough and an end surface having a spherical geometry. A height of the trench may equal a width of the trench. The trench may comprise a cylindrical trough and an end surface having a spherical geometry.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the figures, wherein like numerals denote like elements.
The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the exemplary embodiments of the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein. Thus, the detailed description herein is presented for purposes of illustration only and not limitation. The steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented.
Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
As used herein, “aft” refers to the direction associated with the tail (e.g., the back end) of an aircraft, or generally, to the direction of exhaust of the gas turbine. As used herein, “forward” refers to the direction associated with the nose (e.g., the front end) of an aircraft, or generally, to the direction of flight or motion.
As used herein, “distal” refers to the direction radially outward, or generally, away from the axis of rotation of a turbine engine. As used herein, “proximal” refers to a direction radially inward, or generally, towards the axis of rotation of a turbine engine.
In various embodiments and with reference to
Gas-turbine engine 20 may generally comprise a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A-A′ relative to an engine static structure 36 via several bearing systems 38, 38-1, and 38-2. Engine central longitudinal axis A-A′ is oriented in the z direction on the provided xyz axis. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, including for example, bearing system 38, bearing system 38-1, and bearing system 38-2. In various embodiments, bearing system 38, bearing system 38-1, and bearing system 38-2 may be contained within a bearing housing and/or integrated into an oil delivery system, as described in further detail below.
Low speed spool 30 may generally comprise an inner shaft 40 that interconnects a fan 42, a low pressure (or first) compressor section 44 and a low pressure (or first) turbine section 46. Inner shaft 40 may be connected to fan 42 through a geared architecture 48 that can drive fan 42 at a lower speed than low speed spool 30. Geared architecture 48 may comprise a gear assembly 60 enclosed within a gear housing 62. Gear assembly 60 couples inner shaft 40 to a rotating fan structure. High speed spool 32 may comprise an outer shaft 50 that interconnects a high pressure (or second) compressor 52 and high pressure (or second) turbine 54. A combustor 56 may be located between high pressure compressor 52 and high pressure turbine 54. A mid-turbine frame 57 of engine static structure 36 may be located generally between high pressure turbine 54 and low pressure turbine 46. Mid-turbine frame 57 may support one or more bearing systems 38 in turbine section 28. Inner shaft 40 and outer shaft 50 may be concentric and rotate via bearing systems 38 about the engine central longitudinal axis A-A′, which is collinear with their longitudinal axes. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine.
The core airflow C may be compressed by low pressure compressor section 44 then high pressure compressor 52, mixed and burned with fuel in combustor 56, then expanded over high pressure turbine 54 and low pressure turbine 46. Turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
Gas-turbine engine 20 may be, for example, a high-bypass ratio geared aircraft engine. In various embodiments, the bypass ratio of gas-turbine engine 20 may be greater than about six (6). In various embodiments, the bypass ratio of gas-turbine engine 20 may be greater than ten (10). In various embodiments, geared architecture 48 may be an epicyclic gear train, such as a star gear system (sun gear in meshing engagement with a plurality of star gears supported by a carrier and in meshing engagement with a ring gear) or other gear system. Geared architecture 48 may have a gear reduction ratio of greater than about 2.3 and low pressure turbine 46 may have a pressure ratio that is greater than about five (5). In various embodiments, the bypass ratio of gas-turbine engine 20 is greater than about ten (10:1). In various embodiments, the diameter of fan 42 may be significantly larger than that of the low pressure compressor section 44, and the low pressure turbine 46 may have a pressure ratio that is greater than about five (5:1). Low pressure turbine 46 pressure ratio may be measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of low pressure turbine 46 prior to an exhaust nozzle.
Fan 42 may comprise blades 43 that rotate about the engine central longitudinal axis A-A′. Blades 43 may be airfoils coupled to a rotating hub by an attachment root. As described in further detail below, the attachment root of blades 43 may have trenches or recesses that increase flexibility of blades 43. In that regard, blades 43 with trenches may absorb impact while limiting damage from any resulting strain.
With reference to
In various embodiments, attachment root 100 may comprise leading surface 120 at leading edge 106 of attachment root 100. A dovetail 122 of attachment root 100 may flare out in a circumferential direction to provide a contact surface and retain blade 43 using a dovetail-type joint. Trench 104 may comprise a cylindrical trough 124 formed in surface 102 (i.e., the bottom surface of dovetail 122) and terminating at end surface 108 having a spherical geometry. Cylindrical trough 124 may have a width W1 and join sidewall 110 and sidewall 112, with each sidewall extending tangentially away from cylindrical trough 124 and sidewall 110 being parallel to sidewall 112. Sidewall 112 and sidewall 110 may be oriented orthogonally to surface 102. Trench 104 may have a height H1 from surface 102 into attachment root 100. The rounded contour of cylindrical trough 124 and the spherical contour of end surface 108 may limit stress concentrations in trench 104. However, trench 104 may be rectangular, trapezoidal, triangular, multi-radial, or any other shape to reduce strain concentrations resulting from impact events.
In various embodiments, height H1 and width W1 may be equal. For example, height H1 and width W1 may each be a half inch (1.27 cm). The height H1, width W1, and length L1 of trench 104 may be selected based on a desired flexibility. A greater height H1, width W1, and/or length L1 will result in greater flexibility compared to a trench with smaller dimensions. In that regard, trench 104 having a greater volume may result in increased flexibility compared to a trench 104 having lower volume. With reference to
With reference to
With reference to
An attachment root with recesses formed in the attachment root may provide reduced strain concentrations in response to an impact event. Added flexibility may allow a fan blade to give and spread the impulse of the impact event over a greater time period at lower force. In that regard, an attachment root with a trench formed in the attachment root may be resistant to damage resulting from impact events.
Benefits and other advantages have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, and any elements that may cause any benefit or advantage to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.
Systems, methods and apparatus are provided herein. In the detailed description herein, references to “various embodiments”, “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.
Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f), unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
This application is a nonprovisional of, and claims priority to, and the benefit of U.S. Provisional Application No. 62/167,100, entitled “FAN BLADE ATTACHMENT ROOT WITH IMPROVED STRAIN RESPONSE,” filed on May 27, 2015, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62167100 | May 2015 | US |
