The described subject matter relates generally to turbofan gas turbine engines, and more particularly to an intermediate case of a turbofan gas turbine engine.
Aircraft turbofan engines typically have a segmented case assembly including, for example a fan case, an intermediate case, a compressor case, a gas generator case, a turbine case and a turbine exhaust case, all positioned about an engine central axis. A splitter structure may extend forwardly of struts in the intermediate case. The intermediate case is conventionally cast with struts and the splitter structure integrally cast therein. However, casting is a process which is difficult to control and which requires minimum weight thicknesses to achieve acceptable quality because the structure not only performs aerodynamic functions but must also bear thrust loads. There is also a need for using interior spaces of a splitter and strut structures for services for air/oil systems, instrumentation and maintenance activities such as borescope inspections.
Accordingly, there is a need to provide an improved intermediate case of an aircraft turbofan engine.
In one aspect, the described subject matter provides a casing for an aircraft turbofan bypass engine comprising: an outer ring and an inner hub defining an annular space therebetween, the inner hub configured for connection to at least one spool bearing, the outer ring configured for connection to at least one engine mount; a plurality of hollow radial struts arranged in a circumferential array mounting the inner hub to the outer ring; and an annular splitter box disposed between the inner hub and outer ring and configured to be connected with an upstream annular splitter tip structure to divide an air flow through the annular space into a core air flow and a bypass air flow, the splitter box defined by an inner wall and an outer wall, the splitter box further having an intermediate wall extending downstream conically inward from said outer wall, the splitter box having openings in each of said inner, outer and intermediate walls for receiving said struts passing therethrough, each of said splitter box walls terminating at a downstream end configured for connection to a downstream engine case, the struts being mounted to said splitter box with a respective peripheral weld or braze between the intermediate wall and the struts at the openings of the intermediate wall.
In another aspect, the described subject matter provides an aircraft turbofan bypass engine comprising: a fan assembly, a compressor assembly, a combustion gas generator assembly and a turbine assembly; and a fabricated case having an annular splitter box supporting an upstream annular splitter tip structure, the annular splitter tip structure dividing a fan driven inlet air flow into a bypass air flow and a core air flow, the fabricated case including: an outer ring and an inner hub defining an annular space therebetween, the inner hub configured for connection with at least one spool bearing, the outer ring configured for connection with at least one engine mount; a plurality of load-bearing hollow radial struts arranged in a circumferential array to mount the inner hub to the outer ring, an annular splitter box disposed within the annular space and including an annular outer wall and an annular inner wall, the annular inner wall being disposed within the annular outer wall, the annular splitter box being connected to the upstream annular splitter tip structure and a downstream engine case, the annular outer wall in combination with the outer ring defining a section of a bypass air duct for directing said bypass air flow, the annular inner wall in combination with the inner hub defining a section of a core fluid path of the engine for directing said core air flow, the annular outer and annular inner walls defining a plurality of respective circumferentially spaced openings for allowing the individual struts to radially extend therethrough, and an annular intermediate wall extending downstream conically inward from the outer wall and connected to the downstream engine case, the intermediate wall having a plurality of circumferentially spaced openings receiving the individual struts to radially extend therethrough, the annular intermediate wall being affixed to the struts by welding or brazing along a periphery of a respective one of said openings in the annular immediate wall, an upstream end of the annular intermediate wall being welded or brazed to the annular outer wall and a downstream end of the annular intermediate wall being welded or brazed to a plurality of circumferentially spaced brackets, each bracket being welded or brazed to a corresponding one of the respective struts.
Further details of these and other aspects of the described subject matter will be apparent from the detailed description and drawings included below.
Reference is now made to the accompanying drawings depicting aspects of the described subject matter, in which:
Referring to
The terms “axial”, “radial” and “circumferential” used for various components below are defined with respect to the main engine axis shown but not numbered in
Referring to
An annular portion of the engine core casing 13, as shown in the circled area 2 in
The annular outer wall portion 44 which is a connected section of an inner annular boundary of the bypass air duct 28 and the annular inner wall portion 46 which is a connected section of an annular outer boundary of the core fluid path 30, define a plurality of circumferentially spaced openings 50, 52, respectively, for allowing the individual struts 42 to radially extend therethrough. Welding or brazing may be applied along the periphery of the respective openings 50, 52 to connect the struts 42 to the respective annular outer and inner wall portions 44, 46.
According to this embodiment, an annular intermediate wall 54 may be provided between the annular outer and inner wall portions 44, 46. A plurality of circumferentially spaced openings 56 may also be defined in the annular intermediate wall 54 for allowing the individual struts 42 to radially extend therethrough. The annular intermediate wall 54 may be affixed to the struts 42 for example by welding or brazing along a periphery of the respective one of the openings 56.
According to this embodiment, an upstream end (not numbered) of the annular intermediate wall 54 may be connected to the annular outer wall portion 44, for example by being welded or brazed to the annular outer wall portion 44 at an axial location adjacent to leading edges 58 of the respective struts 42. The annular intermediate wall 54 may extend from an upstream end (not numbered) to a downstream end (not numbered) thereof axially, inwardly away from the annular outer wall portion 44 and therefore the downstream end of the annular intermediate wall 54 may be radially spaced apart from both the annular outer and inner wall portions 44, 46, thereby providing convenient access to the annular space between the annular outer and inner wall portions 44, 46.
According to this embodiment, a plurality of circumferentially spaced brackets 60 may be provided, each connecting the annular intermediate wall 54 to a corresponding one of the respective struts 42. Each of the brackets 60 may be formed with a plate (not numbered) having a substantially U-shaped slot 62 to receive a trailing edge portion 64 of the corresponding strut 42. The brackets 62 may be affixed to the corresponding strut 42 by welding or brazing along an edge of the slot 62. The annular intermediate wall 54 may further include an annular flange 66 extending radially inwardly from the downstream end of the annular intermediate wall 54. The respective brackets 62 may be connected to the downstream end of the annular intermediate wall 54 by being welded directly to the annular flange 66.
The upstream end of the respective annular outer and inner wall portions 44, 46 may be provided with connecting features, such as annular flanges 68, 70 for connection with the upstream annular splitter tip structure 48. The downstream end of the respective annular outer and inner wall portions 44, 46 (the downstream end of the annular inner wall portion 46 is only schematically shown in
The annular intermediate wall 54 may have a web (not numbered) which is thicker than the annular skin of the respective annular outer and inner wall portions 44, 46. The annular intermediate wall 54 extends substantially in the axial direction and is integrated by welding or brazing to the annular outer wall portion 44 and all struts 42. Therefore, the annular intermediate wall 54 functions as a single stringer within the annular splitter box, shown in the circled area 2 in
The substantially axial orientation of the annular intermediate wall 54 with the downstream end thereof radially spaced apart from both annular outer and inner wall portions 44, 46, provides axial access to the annular space defined between the annular outer and inner wall portions 44, 46. This axial access makes it convenient to provide services within the annular splitter box for air/oil systems, instrumentation and maintenance activities of the engine. For example, a service port 72 may be provided on the trailing edge portion 64 of one hollow strut 42 which may allow air/oil service lines to be inserted into the hollow strut 42 or may allow borescope inspection therethrough.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departure from the scope of the described subject matter. For example, the turbofan gas turbine engine as illustrated, is an example taken to illustrate the application of the described subject matter and does not limit the various features and structures of the engines to which the described subject matter may be applicable. Furthermore, the intermediate case may include various other components which are not described. Still other modifications which fall within the scope of the described subject matter will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
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