METHOD FOR MANUFACTURING AN ENGINE COMPONENT WITH A COOLING DUCT ARRANGEMENT AND ENGINE COMPONENT

Abstract

The present invention relates to a method for producing an engine component having a cooling duct arrangement which has a plurality of cooling ducts, each having an inflow opening, the inflow openings being arranged according to a predefined pattern in an inflow surface of the engine component, and each cooling duct opening into a recess in a wall of the engine component, along which wall a cooling film is to be formed. According to the invention, the pattern is formed in at least one subregion of defined size of the inflow surface, from a plurality of identical isosceles triangles, which are defined by a minimum spacing (k) and by a mean diameter (a) of the inflow openings correlating to the minimum spacing (k). This procedure reduces the complexity of the design process.

Claims

1. A method for producing an engine component having a cooling duct arrangement which has a plurality of cooling ducts, each having an inflow opening, wherein the inflow openings are arranged according to a predefined pattern on an inflow surface of the engine component, and each cooling duct opens into a recess in a wall of the engine component, along which wall a cooling film is to be formed by means of a cooling fluid guided onto the wall via the cooling duct arrangement, wherein the method for determining the pattern for the inflow openings comprises the following steps: specifying a minimum spacing (k) between two adjacent inflow openings, determining a number n of cooling ducts and a mean diameter (a) for the inflow openings on the basis of a specified mass flow for the cooling fluid through the cooling ducts and on the basis of a length of extent (L) of the inflow surface along a first direction of extent of the inflow surface, defining an isosceles triangle, at the vertices of which in each case a central point of one of three inflow openings with the mean diameter (a) is provided, wherein, in the case of the isosceles triangle, the length of a base of the isosceles triangle, which base extends along the first direction of extent (x), corresponds to the specified minimum spacing (k), determining a maximum width (s) of a recess, each recess being assigned to a cooling duct, on the basis of the mean diameter (a), and building up the pattern in at least one subregion of specified dimensions of the inflow surface using a multiplicity of identical isosceles triangles, of which a row of triangles situated one behind the other along the first direction of extent defines n vertices, of which two adjacent triangles in each case have at least one vertex in common and at the vertices of which a respective inflow opening with the mean diameter is provided, which in each case leads to a cooling duct that leads into a recess with the maximum width (s).

2. The method as claimed in claim 1, wherein a height (h) of the isosceles triangle and hence a spacing between a tip of the isosceles triangle and the base is dependent on the specified minimum spacing (k).

3. The method as claimed in claim 1, wherein the bases of the triangles for the pattern extend parallel to one another.

4. The method as claimed in claim 1, wherein the pattern for the at least one subregion of the inflow surface on the basis of the triangles having common vertices extends along the first direction of extent (x) and along a second direction of extent (y) extending perpendicularly thereto.

5. The method as claimed in claim 1, wherein the minimum spacing (k) and the mean diameter (a) are specified as proportional to one another.

6. The method as claimed in claim 1, wherein, in at least one other specified subregion of the inflow surface, the pattern for the inflow openings is continued on the basis of the triangles having common vertices, but in this case the mean diameter (a) for the inflow openings of the other subregion is changed.

7. The method as claimed in claim 1, wherein, in at least one other specified subregion of the inflow surface, the pattern for the inflow openings is continued on the basis of the triangles having common vertices, but in this case the minimum spacing (k) is changed.

8. The method as claimed in claims 4, wherein the number of inflow openings for the at least one other subregion of the inflow surface is reduced along the second direction of extent (y) by increasing the minimum spacing (k) or just the height (h) of the isosceles triangles.

9. The method as claimed in claim 1, wherein the mean diameter (a) is in the range of from 0.2 mm to 2 mm.

10. The method as claimed in claim 1, wherein the following applies for a minimum spacing k in the case of a mean diameter a:
2a≤k≤8a.

11. The method as claimed in claim 1, wherein the following applies for a minimum spacing k in the case of a mean diameter a:
k=i*a, where i={2, 3, 4, 5, 6, 7, 8}.

12. The method as claimed in claim 1, wherein the following applies for a maximum width s of the recess in the case of a mean diameter a:
a≤s≤8a.

13. The method as claimed in claim 1, wherein the following applies for a maximum width s of the recess in the case of a mean diameter a:
s=j*a, where j={1, 2, 3, 4, 5, 6, 7, 8}.

14. The method as claimed in claim 1, wherein the pattern is determined in a computer-assisted manner, wherein the minimum spacing (k) for the definition of the triangle is a first input parameter, the mass flow for the cooling fluid is a second input parameter, and the direction of extent (L) of the inflow surface is a third input parameter for a calculation algorithm which is carried out by at least one processor and which builds up the pattern for the inflow openings in the inflow surface on the basis of the first, second and third input parameters and the isosceles triangles defined thereby.

15. The method as claimed in claim 1, wherein the minimum spacing (k) is based on the material from which the engine component is to be produced.

16. An engine component having a cooling duct arrangement which has a plurality of cooling ducts, each having an inflow opening, wherein the inflow openings are arranged according to a predefined pattern in an inflow surface of the engine component, and each cooling duct opens into a recess in a wall of the engine component, along which wall a cooling film is to be formed by means of a cooling fluid guided onto the wall via the cooling duct arrangement, wherein for at least one subregion of the inflow surface, the pattern for the inflow openings provides that the inflow openings are provided with a respective central point at vertices of identical virtual isosceles triangles which each have at least one vertex in common and in which the length of the bases of the triangles each correspond to a minimum spacing k, each inflow opening has an identical mean diameter a, a recess associated with a cooling duct in each case has a maximum width s and the following applies: 1. a={0.2 mm; 2 mm}; 2. 2a≤k≤8a; and 3. a≤s≤8a.

17. The engine component as claimed in claim 16, wherein a base angle (γ) in each case situated opposite the base of a triangle is in the range of from 50° to 100°, and the two identical leg angles (α, β) are in the range of from 35° to 70°, wherein the sum of the base angle (γ) and the two identical leg angles (α, β) corresponds to 180°.

18. The engine component as claimed in claim 16, wherein the engine component is a combustion chamber shingle.

19. An engine having at least one engine component as claimed in claim 16.

Description

IN THE FIGURES

[0044] FIG. 1 shows, in a front view, a segment of an inflow surface of a proposed engine component in which, in accordance with one variant embodiment of a proposed method, inflow openings in a specified pattern having different regions that differ in respect of a requirement for cooling fluid are arranged;

[0045] FIG. 2 shows, in plan view, a single cooling duct having an inflow opening and an associated recess into which the cooling duct opens;

[0046] FIG. 3 shows a sectional illustration of the cooling duct having the recess corresponding to FIG. 2;

[0047] FIG. 4 shows, in isolation, a triangle from which the pattern of FIG. 1 is built up and which has inflow openings at its three vertices;

[0048] FIGS. 5A-5C show different variants for the implementation of the pattern of FIG. 3 and of the recesses adjoining the cooling ducts;

[0049] FIG. 6 shows a flow diagram for the progress of one variant embodiment of a proposed method;

[0050] FIG. 7 shows, in a sectional view, an engine in which an engine component of FIG. 1 is used;

[0051] FIG. 8 shows, on an enlarged scale, a segment of a combustion chamber of the engine of FIG. 7 on which an engine component corresponding to FIG. 1 can be used;

[0052] FIG. 9 shows an engine component known from the prior art having a cooling duct opening into a pocket-like recess.

[0053] FIG. 7 illustrates, schematically and in a sectional illustration, an engine T in which the individual engine components are arranged one behind the other along an axis of rotation or central axis M, and the engine T is formed as a turbofan engine. At an inlet or intake E of the engine T, air is drawn in along an inlet direction by means of a fan F. This fan F, which is arranged in a fan casing FC, is driven by means of a rotor shaft S which is set in rotation by a turbine TT of the engine T. Here, the turbine TT adjoins a compressor V, which comprises for example a low-pressure compressor 111 and a high-pressure compressor 112, and possibly also a medium-pressure compressor. On the one hand, the fan F conducts air in a primary air flow F1 to the compressor V, and, on the other hand, to generate thrust, in a secondary air flow F2 to a secondary flow duct or bypass duct B. The bypass duct B here runs around a core engine comprising the compressor V and the turbine TT and comprising a primary flow duct for the air supplied to the core engine by the fan F.

[0054] The air conveyed into the primary flow duct by means of the compressor V passes into a combustion chamber portion BKA of the core engine, in which the drive energy for driving the turbine TT is generated. For this purpose, the turbine TT has a high-pressure turbine 113, a medium-pressure turbine 114 and a low-pressure turbine 115. Here, the energy released during the combustion is used by the turbine TT to drive the rotor shaft S and thus the fan F in order to generate the required thrust by means of the air conveyed into the bypass duct B. Both the air from the bypass duct B and the exhaust gases from the primary flow duct of the core engine flow out via an outlet A at the end of the engine T. In this arrangement, the outlet A generally has a thrust nozzle with a centrally arranged outlet cone C.

[0055] In principle, the fan F can also be coupled, via the rotor shaft S and an additional epicyclic planetary gear mechanism, to the low-pressure turbine 115 and can be driven by the latter. It is furthermore also possible to provide other, differently designed gas turbine engines in which the proposed solution can be used. For example, engines of this type may have an alternative number of compressors and/or turbines and/or an alternative number of rotor shafts. As an example, the engine may have a split-flow nozzle, meaning that the flow through the bypass duct B has its own nozzle, which is separate from and situated radially outside the core engine nozzle. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct B and the flow through the core are mixed or combined before (or upstream of) a single nozzle, which may be referred to as a mixed-flow nozzle. One or both nozzles (whether mixed or split flow) can have a fixed or variable area. While the example described relates to a turbofan engine, the proposed solution may be applied for example to any type of gas turbine engine, such as an open-rotor engine (in which the fan stage is not surrounded by an engine nacelle) or a turboprop engine.

[0056] FIG. 8 shows a longitudinal section through the combustion chamber portion BKA of the engine T. This shows in particular an (annular) combustion chamber BK of the engine T. A nozzle assembly is provided for the injection of fuel or an air-fuel mixture into a combustion space BR of the combustion chamber BK. Said nozzle assembly comprises a combustion chamber ring, on which multiple fuel nozzles D are arranged along a circular line around the central axis M. The nozzle outlet openings of the respective fuel nozzles D which lie inside the combustion chamber BK are here provided on the combustion chamber ring. Here, each fuel nozzle D comprises a flange by means of which a fuel nozzle D is screwed to an outer casing G of the combustion chamber portion BKA. Via an arm AM and a flange FL, an outer combustion chamber wall of the combustion chamber BK is also connected to this outer casing 22.

[0057] Combustion chamber walls of the combustion chamber BK may, depending on construction, be shielded from the combustion space BR with shingle components in the form of combustion chamber shingles. These combustion chamber shingles may, for example, be connected to inner and outer combustion chamber walls of the combustion chamber BK by means of fixing elements in the form of bolts and nuts. The combustion chamber walls normally have cooling holes and supply openings in the form of mixing air holes in order to be able to guide the air as a cooling fluid to the combustion chamber walls and the combustion chamber shingles. It is possible, in turn, for effusion cooling holes and/or cooling ducts to be provided in the combustion chamber shingles in order to produce a cooling film on a wall of the respective combustion chamber shingle facing the combustion space BR.

[0058] FIG. 9 shows a solution known from the prior art in EP 3 101 231 A1 for the design of a combustion chamber shingle 1 with a cooling duct arrangement. Here, FIG. 9 shows a segment of the combustion chamber shingle 1 with a wall 11, which faces the combustion space BR in the correctly installed state of the combustion chamber shingle. Provided in the wall 11 is a plurality of recesses 3, via which a cooling fluid, here in the form of cooling air, is brought up to the wall 11 in order to produce on the wall 11 a cooling film which is as homogeneous as possible. Just one pocket-like recess 3 is illustrated by way of example in FIG. 9. Starting from an outflow opening 21 in an end face 31 of the recess 31, this pocket-like recess 3 guides cooling fluid in the direction of a transition 32 of the recess 3 and up to the surface of the wall 11. In this case, mutually opposite side walls 33a and 33b, each adjoining the end face 31, are arranged at an angle to a central axis of the recess 3, with the result that the recess 3 widens like a diffuser, starting from the end face 31. Provided approximately in the center in the case of the recess 3 illustrated in FIG. 9 is an impact element 34 which, by way of example, is configured as a segment of an ellipsoid of rotation or a spoon back.

[0059] The outflow opening 21 provided in the end face 31 of the recess 3 is part of a cooling duct 2 formed within the combustion chamber shingle 1. The cooling fluid flows into this cooling duct 2 via an inflow opening 20 in an inflow surface 10 of the combustion chamber shingle 1. Via the cooling duct 2, the cooling fluid is guided into the recess 3, and is then guided along the surface of the wall 11 via the recess.

[0060] FIGS. 1 to 5C illustrate how, for a cooling arrangement 200 with a plurality of cooling ducts 2, associated inflow openings 20a-20b or 20.1-20.5 can be arranged in the inflow surface 10, following a specific pattern, enabling the pattern to meet the specific requirements for the necessary cooling mass flow demand while, at the same time, also facilitating automated specification of the positions of the inflow openings in the inflow surface 10.

[0061] Here, FIG. 1 shows, in a front view, the inflow surface 10 with a length of extent L along a first direction of extent x. Perpendicularly to the first direction of extent x, the inflow surface 10 extends along a second direction of extent y. The starting point for the production of a pattern having a plurality of pattern sections M1-M5 for the arrangement of a multiplicity of inflow openings 20a to 20c is the specification of a minimum spacing k between two inflow openings 20a and 20b adjacent to one another along the first direction of extent x, said spacing resulting, in particular, from a possible minimum wall thickness that is still allowed by the material for the combustion chamber shingle 1, for example. The material is, for example, an Ni- or Co-based alloy (e.g. C263, H286 or H230).

[0062] Furthermore, a maximum permissible mean diameter a for the inflow openings 20a or 20b is now assumed in order to determine how many inflow openings 20a, 20b with this mean diameter a are required to ensure a specified mass flow of cooling fluid via cooling ducts 2 to be provided over a partial length of the total length L while maintaining the specified minimum distance k. Here, by way of example, the number of equally distributed inflow openings 20a, 20b along the direction of extent x, which coincides, for example, with a circumferential direction, is obtained from the integer part of the quotient of the partial length of the length of extent L and the minimum spacing k in the case of the maximum diameter a.

[0063] Depending on the necessary or specified mass flow of cooling fluid which is to be delivered via the inflow openings 20a, 20b to the associated recesses 3, the mean diameter a that has actually to be specified may then also prove to be smaller. The decisive factor is first of all to determine how many inflow openings 20a, 20b must be provided spaced apart from one another by the minimum spacing k along the direction of extent x on the specified partial length in order to be able to form the desired mass flow of cooling fluid, wherein the minimum spacing k corresponds to the spacing between the central points of the inflow openings 20a and 20b.

[0064] In this context, it is furthermore worth noting that the mean diameter a and a maximum width s of a recess 3 which characterizes the spacing between the two side walls 33a and 33b are in a close parameter relationship. The mean diameter a of the inflow openings 20a, 20b and the maximum width s at the recess 3, which widens in a funnel shape and in the manner of a diffuser, starting from an outflow opening 21, are consequently correlated with one another.

[0065] On the basis of the determined minimum spacing k along the direction of extent x, an isosceles triangle 4 is now defined, the base of which has the minimum spacing k as a length and also the minimum section k as a height h and at the vertices 4a, 4b and 4c of which in each case a central point of one of three inflow openings 20a, 20b and 20c, each with the mean diameter a, is provided. This isosceles triangle 4 forms the starting point for the further buildup of the pattern with its pattern sections M1-M5. In this case, a pattern section M1 is assigned to a first zone or to a first subregion z1 on the inflow surface 10 for which the necessary mass flow of cooling fluid may be different from mass flows which may have to be made available over other zones or subregions z2 to z5 of the inflow surface 10.

[0066] For the (first) subregion z1, the pattern in pattern section M1 with the inflow openings 20a, 20b and 20c is in all cases first built up using a plurality of isosceles triangles 4, each having at least one vertex 4a, 4b or 4c in common. Specification by means of the isosceles (reference) triangle 4 and parallel alignment of the bases of these isosceles triangles with respect to one another gives rise in direction of extent y to successive rows of inflow openings 20a, 20b, 20c which, based on direction of extent x, are each offset with respect to one another by half the minimum spacing k and are spaced apart equidistantly by the minimum spacing k. By means of the specification of the minimum spacing k, which depends, in particular, on the material and the strength values thereof and, where applicable, also on production-related criteria, it is ensured in pattern section M1 of the built-up pattern that there always remains a dividing wall of defined wall thickness d between the edges of the individual inflow openings 20a, 20b, 20c in the inflow surface 10, said wall having a sufficient stability. In principle, the following applies for the height h (or y1) as a function of the minimum spacing k: 0.1 k≤h≤4 k.

[0067] For other subregions z2 to z5 of the inflow surface 10, the pattern is modified accordingly, depending on the mass flow of cooling fluid required. In this case, however, the basic model and thus the structure of the pattern based on the isosceles triangle 4 is retained. The individual inflow openings 20a, 20b and 20c continue to be provided at the vertices of isosceles triangles 4 of identical design. Consequently, in the example illustrated in FIG. 1, only the mean diameters a are correspondingly adapted, in this case reduced, in order to meet a lower cooling fluid requirement.

[0068] However, the possibility that the minimum spacing k will have to be changed in other regions, e.g. on account of the shape of the combustion chamber shingle 1, is not excluded here. Here too, however, the basic structure is retained, and only the distribution of the inflow openings and of the cooling ducts 2 and recesses 3 adjoining said openings changes. In this case, the distribution can change, for example, along a defined path p, which is a function of the engine axis, of the radial spacing perpendicularly to this engine axis and an angle at the circumference. Here, the engine axis can be defined by a spatial direction running perpendicularly to the two directions of extent x and y, for example.

[0069] In the case of the pattern M1-M5 illustrated in FIG. 1, a homogeneous cooling film with five different regions, in each of which different cooling air quantities are required, is achieved, wherein the pattern M1-M5 is built up in an automated manner using isosceles triangles 4 on the basis of a small number of defined input parameters and thus boundary conditions, beginning with the zone or subregion z1 that has the most densely packed inflow openings 20a, 20b and 20c. The arrangement of the inflow openings 20a, 20b and 20c for the further subregions z2 to z5 is then generated while retaining the basic structure and hence spacings x1=k and y1=k along the two directions of extent x and y.

[0070] The different geometrical relationships between the input parameters and the decisive geometrical relationships are illustrated once again here with reference to FIGS. 2, 3 and 4. By way of example, a mean diameter a of 0.2 mm to 2 mm is specified here, and 2a≤k≤8a applies to the minimum spacing k.

[0071] a≤s≤8a furthermore applies to the maximum width s of the recess 3 widening in the manner of a diffuser in the associated wall 11. According to FIG. 4, the angles of the specified isosceles triangle 4 are such that a base angle γ, which lies opposite a base of the isosceles triangle 4 is in the range of from 50° to 100°, while the leg angles α, β of the triangle 4 are each in the range of from 35° to 70°.

[0072] FIGS. 5A and 5B illustrate the arrangement along the longitudinal direction of extent x of adjacent inflow openings 20.1, 20.2, 2.3 with in this case respectively associated recesses 3.1, 3.2 and 3.3. Also illustrated in this context is a length I of the pocket-like recesses 3.1, 3.2 and 3.3 in the wall 11. It is thus possible, according to the variant embodiment in FIG. 5B, for the minimum spacing k and hence the resulting minimum wall thickness d.sub.min between the adjoining inflow openings 20.1/20.2 and 20.2/20.3 to be reduced to such an extent that a certain region of overlap is obtained between the mutually adjoining cooling ducts 2 and recesses 3.4, 3.5 of rows of inflow openings 20.4, 20.5 lying in the direction of extent y. However, by means of specification with the aid of the isosceles triangles 4, it is readily ensured, with the possibility of appropriate parametrization, that a minimum material thickness d.sub.min within the combustion chamber shingle 1 is not undershot.

[0073] In accordance with FIG. 5C, it is likewise readily possible to provide for recesses 3.1, 3.2 and 3.3 adjacent to one another in the first direction of extent x and located in the surface of the wall 11 to merge into one another up to a length of l/2 in the second direction of extent y.

[0074] The flow diagram in FIG. 6 illustrates once again the progress of a production method already explained above, by means of which a cooling duct arrangement 200 with inflow openings 20a-20c; 20.1-20.5 can be built up efficiently, following a defined pattern, and, in particular, can in this process be generated in a computer-assisted manner for manufacture, and is adaptable in a variable way.

[0075] After the start of a program sequence at a time S, a minimum spacing k that must exist between two adjacent inflow openings 20a, 20b is first of all specified in a method step A1 by the user or automatically by the computer system on the basis of stored material and/or manufacturing data.

[0076] On the basis of a specified mass flow for the cooling fluid through the individual cooling ducts 2 that is necessary for the cooling of the wall 11 in a certain region, and on the basis of a length of extent of the inflow surface 10 along the first direction of extent x, which corresponds, for example, to part or all of the total length of extent L, the number of cooling ducts 2 and the mean diameter a thereof that must be provided along this direction of extent x is then determined in a method step A2.

[0077] In a subsequent method step A3, a (first) isosceles (reference) triangle 4, at the vertices 4a, 4b and 4c of which in each case a central point of one of three inflow openings 20a, 20b and 20c with the mean diameter a is to be provided, is then defined. Here, the length of a base of the isosceles triangle 4, said base extending along the first direction of extent x, corresponds to the specified minimum standard k. In this case, the minimum spacing k also takes account of the fact that the maximum width s of a recess 3 respectively assigned to a cooling duct 2 is in a specific parameter relationship with the mean diameter a of its inflow opening 20a-20c. Accordingly, the maximum width s is determined in a method step A4, e.g. with the proviso that s =a . . . 8a applies. A specific pattern for the recesses 3 in the wall 11 to be cooled is thereby also specified in addition to the pattern for the inflow openings 20a, 20b, 20c in the inflow surface 10.

[0078] Finally, the pattern comprising all the pattern sections M1-M5 for the individual inflow openings 20a, 20b, 20c over the total specified inflow surface 10 is then built up in a method step A5 by means of a calculation algorithm that is run, taking into account the existing boundary conditions, optionally while taking into account the different cooling requirement for the individual subregions z1 to z5. Here, as explained, the pattern comprising the pattern sections M1-M5 is built up along the two directions of extent x and y by means of a multiplicity of isosceles triangles 4, which are identical and hence correspond to the first reference triangle. For the definition of the pattern M1-M5, the triangles 4 each have at least one vertex 4a, 4b or 4c in common. Starting from the (reference) subregion z1 with the most densely packed inflow openings 20a, 20b and 20c, using the basic model based on the use of isosceles triangles for example, the spacing of the inflow openings 20a, 20b and 20c with respect to one another in the other subregions z2-z5 is not changed, but the mean diameter a for the inflow openings 20a, 20b and 20c can vary depending on the respective subregion z2-z5.

[0079] After the end E of the program sequence, a computer-generated pattern for the arrangement of the inflow openings 20a, 20b, 20c and, by means of the latter, then also of the cooling ducts 2 and of the associated recesses 3 is thus available on the basis of a few boundary conditions to be specified. By means of a cooling fluid flowing in via such a pattern, it is possible to provide an efficient and homogeneous cooling film on the wall 11. Here, the procedure outlined above ensures that a cooling film of this kind can also be generated efficiently on engine components of different configurations and, in particular, without the need to specify entirely new modeling parameters for the arrangement of the cooling ducts 2 and of the inflow openings 20a-20c, 20.1-20.5.

LIST OF REFERENCE SIGNS

[0080] 1 Combustion chamber shingle (engine component) [0081] 10 Inflow surface [0082] 11 Wall [0083] 111 Low-pressure compressor [0084] 112 High-pressure compressor [0085] 113 High-pressure turbine [0086] 114 Medium-pressure turbine [0087] 115 Low-pressure turbine [0088] 2 Cooling duct [0089] 20, 20.1-20.5 Inflow opening [0090] 20a, 20b, 20c [0091] 200 Cooling duct arrangement [0092] 21 Outflow opening [0093] 3, 3.1-3.5 Recess [0094] 31 End face [0095] 32 Transition [0096] 33a, 33b Side wall [0097] 34 Impact element [0098] 4 Triangle [0099] 4a, 4b, 4c Vertex [0100] a (Mean) diameter [0101] A Outlet [0102] AM Arm [0103] B Bypass duct [0104] BK Combustion chamber [0105] BKA Combustion chamber portion [0106] BR Combustion space [0107] C Outlet cone [0108] D Fuel nozzle [0109] d, d.sub.min Material thickness [0110] E Inlet/Intake [0111] F Fan [0112] F1, F2 Fluid flow [0113] FC Fan casing [0114] FL Flange [0115] G Outer casing [0116] h Height [0117] k Minimum spacing [0118] L Length of extent [0119] l Length [0120] M Central axis/axis of rotation [0121] M1-M5 Pattern regions [0122] S Rotor shaft [0123] T (Turbofan) engine [0124] TT Turbine [0125] V Compressor [0126] z1-z5 Subregion/zone