Compact turbofan engine case

Abstract

The invention provides a compact turbofan engine case. The compact turbofan engine case comprises a case head end part and a case tail end part, the casing tail end part comprises a transition section casing and a low-pressure turbine casing, the head end of the transition section casing is connected with the tail end of the casing head end part, and the tail end of the transition section casing is connected with the low-pressure turbine casing; the outer wall of the head end of the casing is flush with the outer wall of the outer culvert channel inner ring, the outer wall of the tail end of the low-pressure turbine casing is connected with the inner wall of the outer culvert channel inner ring in a sleeved mode, and the outer diameter of the head end of the low-pressure turbine casing and the outer diameter of the tail end of the transition section casing are smaller than the outer diameter of the tail end of the low-pressure turbine casing so that a containing cavity can be formed. And a nozzle mounting seat is arranged on the side wall of the transition section casing. According to the compact turbofan engine case, the split type case design is adopted, the head end of the case and the tail end of the case are produced in a split mode, the case structure is divided into two structures, and the production difficulty is lowered; meanwhile, the transition section case and the low-pressure turbine case are integrally designed, and the containing cavity is arranged to contain the fuel nozzle and the fuel header pipe, so that the influence on external culvert airflow is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of engine casings, and particularly relates to a compact turbofan engine casing. Background Art

[0002] Aeroengine casings mainly include diffuser casings, combustion chamber casings, and turbine casings. Among them, the combustion chamber casing and the diffuser casing often adopt a split design, while the combustion chamber casing itself adopts an integrated design, with a relatively complex structure and a large processing difficulty, resulting in a high processing cost and a large structural space. Moreover, the fuel nozzles and the fuel manifold installed on the combustion chamber casing are generally arranged on the surface of the combustion chamber casing, resulting in poor coordination of the overall structural layout.

[0003] In the currently commonly used engine casings, due to the relatively small number of combustion chamber heads, the number of fuel nozzles is small, the structure of the fuel manifold is relatively simple, the fuel nozzles and the fuel manifold are directly arranged at the head of the combustion chamber casing, and the radial position of the fuel manifold pipeline is generally higher than the cylinder body of the combustion chamber casing. Although it is directly exposed to the bypass air flow, a high requirement is imposed on the structural compactness of the engine casing, and it is required that the structural layout on the casing surface be kept simple to avoid affecting the bypass air flow, thereby ensuring the safe operation of the engine.

[0004] However, with the increase in the number of combustion chamber heads or the application of dual - fuel - path fuel nozzles, the fuel manifold pipeline becomes more and more complex, and the influence of the pipeline on the bypass air flow becomes greater and greater, unable to meet the requirements of the safe operation of the engine. Summary of the Invention

[0005] In view of the above problems, the present invention provides a compact turbofan engine casing, comprising: a casing head end and a casing tail end arranged coaxially;

[0006] The casing tail end includes a transition section casing and a low - pressure turbine casing. The head end of the transition section casing is fixedly connected to the tail end of the casing head end, and the tail end of the transition section casing is connected to the head end of the low - pressure turbine casing;

[0007] The outer wall of the casing head end is flush with the outer wall of the inner ring of the bypass passage, the outer wall of the tail end of the low - pressure turbine casing is sleeved with the inner wall of the inner ring of the bypass passage, and the outer diameters of the head end of the low - pressure turbine casing and the tail end of the transition section casing are smaller than the outer diameter of the tail end of the low - pressure turbine casing to form a receiving cavity;

[0008] The side wall of the transition section casing is provided with a nozzle mounting seat facing the receiving cavity.

[0009] Furthermore, the transition section casing includes: a combustion chamber casing head, a first straight section, and a second straight section, which are connected in sequence from the head end to the tail end;

[0010] The outer diameter of the first straight section is smaller than the outer diameter of the second straight section, and the outer diameters of the first straight section and the second straight section are smaller than the outer diameter of the tail end of the transition section casing.

[0011] Furthermore, the head of the combustion chamber casing includes: an upper head profile and a lower head profile;

[0012] The tails of the upper head profile and the lower head profile are butted, the heads of the upper head profile and the lower head profile form a predetermined angle, the head of the upper head profile is fixedly connected to the tail of the head end of the casing, and a plurality of nozzle mounting seats are arranged in a circumferential array on the outer wall of the upper head profile.

[0013] Furthermore, a flange is provided at the head of the lower head profile, and a flared self-locking nut is installed in the mounting hole of the flange.

[0014] Furthermore, the low-pressure turbine casing includes a turning section and an outward expanding section connected end to end. The head of the turning section is connected to the tail of the transition section casing, the outer wall of the tail of the outward expanding section forms a socket joint with the inner wall of the inner ring of the outer bypass passage, and a plurality of threaded holes are provided on the end face of the tail of the outward expanding section.

[0015] Furthermore, the head end of the casing includes: a diffuser casing, a combustion chamber casing, and a combustion chamber flange connected end to end in sequence;

[0016] The diffuser casing extends towards the axis direction of the head end of the casing. The diffuser casing and the combustion chamber casing jointly form a semi-enclosed inner cavity for installing the diffuser, and the combustion chamber flange is connected to the head of the transition section casing.

[0017] Furthermore, the side wall of the diffuser casing is provided with a first flange and a second flange. The first flange and the second flange assemble the diffuser through bolts, so that a first chamber, a second chamber, and a third chamber are formed between the diffuser casing and the diffuser, and the first chamber is communicated with the third chamber;

[0018] A positioning step adapted to the diffuser is provided on one side of the side wall of the diffuser casing facing the first chamber.

[0019] Furthermore, an air extraction mounting seat connecting the first chamber is provided on the side wall of the diffuser casing, and the air extraction mounting seat is located between the first flange and the second flange.

[0020] Furthermore, the combustion chamber flange includes a ring body portion, a plurality of threaded holes are circumferentially arrayed on the side wall of the ring body portion, and a stop is provided on the inner wall of the ring body portion;

[0021] A protruding ring block adapted to the stop is provided at the head of the upper head profile.

[0022] Furthermore, valve mounting seats, spark plug mounting seats, and fixed pin mounting seats are provided on the outer wall of the combustion chamber casing;

[0023] The fixed pin mounting seat adopts a hollow cylindrical structure, and internal threads are provided on the inner wall of the hollow inner cavity of the fixed pin mounting seat.

[0024] Compared with the prior art, the embodiments of the present invention have at least the following advantages:

[0025] 1. The compact turbofan engine casing of the present invention adopts a split casing design, separating the production of the front end of the casing from the rear end of the casing and fixedly connecting them. The complex casing structure is split into two simple structures, greatly reducing the overall machining difficulty of the casing, thereby improving the overall machining efficiency of the casing and realizing the integrated design of the engine casing.

[0026] 2. Among them, the transition casing and the low-pressure turbine casing adopt an integrated design. On the basis that the outer wall of the front end of the casing is flush with the inner wall of the outer annulus channel and the outer wall of the rear end of the low-pressure turbine casing forms a socket joint with the inner wall of the outer annulus channel, a receiving cavity is formed between the transition casing and the inner wall of the outer annulus channel to receive the fuel nozzle and the fuel manifold, avoiding the exposure of the fuel nozzle and the fuel manifold in the outer annulus of the engine, avoiding the influence on the outer annulus airflow, and improving the applicability of the engine casing for turbofan engines.

[0027] Other features and advantages of the present invention will be described in the following specification, and, in part, will become apparent from the specification or will be understood by practicing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 Shows a cross-sectional schematic view of the compact turbofan engine casing in the embodiment of the present invention;

[0030] Figure 2 Shows a cross-sectional schematic view of the front end of the casing in the embodiment of the present invention;

[0031] Figure 3 Shows a three-dimensional schematic view of the rear end of the casing in the embodiment of the present invention;

[0032] Figure 4 Shows a partial cross-sectional schematic view of the rear end of the casing in the embodiment of the present invention;

[0033] Figure 5 Shows a schematic view of the use state of the compact turbofan engine casing in the embodiment of the present invention.

[0034] In the figure, the front end portion 1 of the casing, the combustion chamber casing 11, the valve mounting seat 111, the fixed pin mounting seat 112, the spark plug mounting seat 113, the combustion chamber flange 12, the threaded hole 121, the stop 122, the ring body portion 123, the diffuser casing 13, the first flange member 131, the second flange member 132, the positioning step 133, the bleed air mounting seat 134, the rear end portion 2 of the casing, the transition section casing 21, the head portion 211 of the combustion chamber casing, the upper head surface 2111, the lower head surface 2112, the protruding ring block 2113, the first straight section 212, the second straight section 213, the nozzle mounting seat 214, the third flange member 215, the flared lock nut 216, the low-pressure turbine casing 22, the turning portion 221, the outward expansion portion 222, the fastening screw 3, the storage cavity 4, the first chamber 5, the second chamber 6, the third chamber 7, the diffuser 81, the fuel nozzle 82, the fuel manifold 83, the bypass duct 84. Detailed implementation manners

[0035] The following description provides many different embodiments or examples for implementing different features of the present invention. The elements and arrangements described in the following specific examples are only used to concisely express the present invention, and they are only examples and are not intended to limit the present invention.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] It should be added that with reference to Figure 5 ..., an outer bypass duct 84 is provided on the outer ring of the casing of the aero turbofan engine. To reduce the influence of the surface structure of the casing on the airflow in the bypass duct 84, it is required that the structure of the engine casing be as compact and simple as possible. Therefore, it is required that the number of mounting seats on the casing surface be small and the structure be simple.

[0038] Among them, the fuel nozzle 82 and the fuel manifold 83 are the main structures arranged on the surface of the combustion chamber casing. And as the number of combustion chamber heads increases, the number of fuel nozzles 82 also increases correspondingly, or due to the application of dual-path fuel nozzles 82, the pipeline of the fuel manifold 83 becomes more and more complex. To avoid the influence of the complex fuel manifold 83 and fuel nozzles 82 on the airflow in the bypass duct 84.

[0039] Meanwhile, the engine casing includes a diffuser casing, a combustion chamber casing, and a turbine casing. Among them, the diffuser casing is used to enclose the diffuser 81; the combustion chamber casing is used to enclose the flame tube and form a secondary air inlet passage of the combustion chamber in combination with the outer wall surface of the flame tube; the turbine casing is used to enclose the transition section and the high-pressure turbine.

[0040] The present invention provides a compact turbofan engine casing, which is used to be installed in the bypass duct 84 and is also used for assembling the fuel manifold 83 and the diffuser 81. Figure 1 The sectional schematic diagram of the compact turbofan engine casing in the embodiment of the present invention is shown. Figure 1 In this, the compact turbofan engine casing includes: a casing head end portion 1 and a casing tail end portion 2 arranged coaxially. The casing head end portion 1 is equivalent to a combined component of a diffuser casing and a combustion chamber casing, and the casing tail end portion 2 is equivalent to a combined component of the head of the combustion chamber casing and a turbine casing.

[0041] The casing tail end portion 2 includes a transition section casing 21 and a low-pressure turbine casing 22. The head end of the transition section casing 21 is fixedly connected to the tail end of the casing head end portion 1 through fastening screws 3, and the tail end of the transition section casing 21 is connected to the head end of the low-pressure turbine casing 22.

[0042] The outer wall of the casing head end portion 1 is flush with the inner wall of the outer ring of the bypass duct 84. The outer wall of the tail end of the low-pressure turbine casing 22 is sleeved with the inner wall of the inner ring of the bypass duct 84. The outer diameters of the head end of the low-pressure turbine casing 22 and the tail end of the transition section casing 21 are smaller than the outer diameter of the tail end of the low-pressure turbine casing 22 to form a receiving cavity 4.

[0043] The side wall of the transition section casing 21 is provided with a nozzle mounting seat 214 facing the receiving cavity 4, and the nozzle mounting seat 214 provides an installation position for the fuel nozzle 82, so that the fuel nozzle 82 and the corresponding fuel manifold 83 are received in the receiving cavity 4, avoiding the fuel manifold 83 and the fuel nozzle 82 from being exposed to the bypass air flow.

[0044] The compact turbofan engine casing of the present invention adopts a split casing design, separates the production of the casing head end portion 1 and the casing tail end portion 2, and completes the fixed connection through the fastening screws 3. The complex casing structure is split into two simple structures, greatly reducing the overall processing difficulty of the casing, and further improving the overall processing efficiency of the casing, realizing the integrated design of the engine casing. At the same time, the transition section casing 21 and the low-pressure turbine casing 22 adopt an integrated design. On the basis that the outer wall of the casing head end portion 1 is flush with the inner wall of the outer ring of the bypass duct 84 and the outer wall of the tail end of the low-pressure turbine casing 22 is sleeved with the inner wall of the inner ring of the bypass duct 84, a receiving cavity 4 is formed between the transition section casing 21 and the inner wall of the inner ring of the bypass duct 84 to receive the fuel nozzle 82 and the fuel manifold 83, avoiding the fuel nozzle 82 and the fuel manifold 83 from being exposed to the bypass duct of the engine and avoiding the influence on the bypass air flow, and improving the applicability of the engine casing for the turbofan engine.

[0045] In this embodiment, referring to Figure 2 , the specific structure of the casing tail end portion 2 is as follows:

[0046] Among them, the transition section casing 21 includes a combustion chamber casing head 211, a first straight section 212, and a second straight section 213 that are sequentially connected at the head and tail ends;

[0047] Considering that there is a certain height difference in the radial direction between the inlet of the return combustion chamber and the gas outlet, correspondingly, the outer diameter of the first straight section 212 is smaller than the outer diameter of the second straight section 213, and the outer diameters of the first straight section 212 and the second straight section 213 are smaller than the outer diameter of the tail end of the transition section casing 21, forming a receiving cavity 4 between the first straight section 212, the second straight section 213 and the inner wall of the inner ring of the outer bypass passage 84.

[0048] Among them, the combustion chamber casing head 211 includes: an upper head surface 2111 and a lower head surface 2112;

[0049] The tail ends of the upper head surface 2111 and the lower head surface 2112 are butted, and the head ends of the upper head surface 2111 and the lower head surface 2112 form a predetermined angle. Among them, the extending direction of the head end of the upper head surface 2111 forms an angle of +42 to +50° with the horizontal plane, and the extending direction of one end of the lower head surface 2112 forms an angle of -48 to -52° with the horizontal plane. Exemplarily, the extending direction of the head end of the upper head surface 2111 forms an angle of +46° with the horizontal plane, the extending direction of one end of the lower head surface 2112 forms an angle of -50° with the horizontal plane, and the side walls of the butted ends of the upper head surface 2111 and the lower head surface 2112 adopt a rounded corner transition, increasing the overall strength of the engine casing through the inclined plane design.

[0050] The head end of the upper head surface 2111 is fixedly connected to the tail end of the casing head portion 1 by fastening screws 3, and a plurality of nozzle mounting seats 214 are arranged in a circumferential array on the outer wall of the upper head surface 2111 for installing fuel nozzles 82 to supply fuel to the combustion chamber.

[0051] Among them, a third flange member 215 is provided at the head end of the lower head surface 2112, and a flared self-locking nut 216 is installed in the mounting hole of the third flange member 215 for corresponding assembly with the transition section.

[0052] It should be added that the tail end of the transition section casing 21 and the head end of the low-pressure turbine casing 22 are connected by electron beam welding.

[0053] Among them, considering that there is a certain height difference in the radial direction between the inlet of the return combustion chamber and the gas outlet, on the basis of making a corresponding structural design for the transition section casing 21.

[0054] The low-pressure turbine casing 22 includes a turning portion 221 and an outwardly expanding portion 222 that are connected at the head and tail. The head end of the turning portion 221 is connected to the tail end of the transition section casing 21, the outer wall of the tail end of the outwardly expanding portion 222 forms a socket with the inner wall of the inner ring of the outer bypass passage 84, and a plurality of threaded holes are provided on the end face of the tail end of the outwardly expanding portion 222.

[0055] As a result, the upper head profile 2111, the first straight section 212, the second straight section 213, the turning part 221, the outward expansion part 222 and the inner wall of the inner ring of the outer duct 84 jointly form the receiving cavity 4.

[0056] Correspondingly, several T45 probe mounting seats can be arranged on the first straight section 212 according to actual needs for installing the T45 probe leads, so that the T45 probe leads are also received by the receiving cavity 4, avoiding the mutual influence between the T45 leads and the outer duct air flow.

[0057] Similarly, those skilled in the art can add other devices in the receiving cavity 4 in combination with the technical principle of the present invention to reduce the influence on the outer duct air flow.

[0058] In this embodiment, referring to Figure 1 、 Figure 3 and Figure 4 , the specific structure of the front end part 1 of the casing is as follows:

[0059] Among them, the front end part 1 of the casing includes: a diffuser casing 13, a combustion chamber casing 11, and a combustion chamber flange 12. The front and rear ends of the diffuser casing 13, the combustion chamber casing 11, and the combustion chamber flange 12 are sequentially connected by electron beam welding.

[0060] It should be added that before welding the front and rear ends of the combustion chamber casing 11 and the combustion chamber flange 12 by electron beam welding, the diffuser 81 needs to be assembled with the front end part 1 of the casing first. On the one hand, it avoids that after the combustion chamber casing 11 and the combustion chamber flange 12 are welded, the diffuser 81 and the combustion chamber flange 12 are in contact, resulting in the diffuser 81 being unable to be installed normally; on the other hand, the welding of the combustion chamber flange 12 is after the assembly operation of the diffuser 81. On the basis that the combustion chamber flange 12 and the diffuser 81 are in contact, the relative position of the diffuser 81 and the front end part 1 of the casing is limited, so that the diffuser 81 and the casing of the present application form an integral body.

[0061] The diffuser casing 13 extends towards the axis direction of the front end part 1 of the casing. The diffuser casing 13 and the combustion chamber casing 11 jointly form a semi-surrounding inner cavity for installing the diffuser 81. The combustion chamber flange 12 is connected to the front end of the transition section casing 21 by fastening screws 3.

[0062] Integrated design of the combustion chamber casing 11 and the diffuser casing 13 enables the diffuser 81 to directly form an integral body with the front end part 1 of the casing after being installed in the semi-surrounding inner cavity, realizing the integrated effect and further improving the simplicity of the overall structure of the engine.

[0063] Among them, the side wall of the diffuser casing 13 is provided with a first flange member 131 and a second flange member 132; wherein, the second flange member 132 and the first flange member 131 are arranged in an inner and outer ring on the side wall of the diffuser casing 13. The first flange member 131 and the second flange member 132 are assembled with the diffuser 81 through bolts 30, so as to form a first chamber 5, a second chamber 6 and a third chamber 7 between the diffuser casing 13 and the diffuser 81. Among them, the first chamber 5 and the second chamber 6 are not communicated with each other to prevent air flow from directly entering the combustion chamber without passing through the diffuser 81, and the first chamber 5 and the third chamber 7 are communicated with each other.

[0064] At the same time, a positioning step 133 adapted to the diffuser 81 is provided on one side of the side wall of the diffuser casing 13 facing the first chamber 5, so as to position the installation of the diffuser 81 and improve the sealing performance between the first chamber 5 and the second chamber 6.

[0065] Correspondingly, an air extraction mounting seat 134 connecting the first chamber 5 is provided on the side wall of the diffuser casing 13 for extracting air from the front section of the diffuser 81. The air extraction mounting seat 134 is located between the first flange member 131 and the second flange member 132 to limit the air flow direction. Exemplarily, the number of the air extraction mounting seats 134 is two.

[0066] In addition, the combustion chamber flange 12 includes a ring body portion 123, a plurality of threaded holes 121 circumferentially arranged on the side wall of the ring body portion 123, a stop 122 is provided on the inner wall of the ring body portion 123, and a protruding ring block 2113 adapted to the stop 122 is provided at the head of the upper head surface 2111 to improve the convenience of assembling the upper head surface 2111 and the combustion chamber flange 12 and the positioning accuracy.

[0067] In the present invention, the outer wall surface of the combustion chamber casing 11 serves as the inner ring surface of the outer bypass passage 84 of the turbofan engine, and together with the outer ring surface of the bypass passage, forms the outer bypass passage 84 of the engine combustion chamber section; the inner wall surface of the combustion chamber casing 11 serves as the outer ring surface of the secondary air passage of the combustion chamber, and together with the outer wall surface of the flame tube, forms the secondary air inlet passage of the combustion chamber.

[0068] Correspondingly, the outer wall of the combustion chamber casing 11 is provided with a valve mounting seat 111, a spark plug mounting seat 113 and a plurality of fixed pin mounting seats 112 circumferentially arranged around the axis of the combustion chamber casing 11;

[0069] Exemplarily, the valve mounting seat 111 is located directly below the combustion chamber casing 11 and is used to install an oil drain valve to drain the remaining oil in the combustion chamber casing after the engine stops.

[0070] Two spark plug mounts 113 are respectively located on both sides of the valve mount 111, and the central angle between the two spark plug mounts 113 and the valve mount 111 is 45°, which is used to install the combustion chamber ignition spark plugs.

[0071] Six fixing pin mounts 112 are arranged on the outer wall of the combustion chamber casing 11 and are arranged in a circumferential array about the axis of the combustion chamber casing 11, which is used to install fixing pins to connect the combustion chamber casing and the flame tube.

[0072] Among them, the fixing pin mount 112 adopts a hollow cylindrical structure, and the inner wall of the hollow inner cavity of the fixing pin mount 112 is provided with internal threads. The overall structure is simple and there are no right angles, sharp edges, etc., so as to reduce the influence of the fixing pin mount 112 on the bypass duct air flow.

[0073] In the present invention, the integrated design of the combustion chamber casing 11 and the diffuser casing 13, and the integrated design of the transition section casing 21 and the low-pressure turbine casing 22 provide an engine casing with a compact structure, high strength and easy processing, and the structural layout is reasonable; at the same time, the fuel nozzle 82 and the fuel manifold 83 are prevented from being exposed in the engine bypass duct.

[0074] The engine casing provided by the present invention has a more compact structure, better machinability and higher strength than the existing engine casing solutions. At the same time, the pipelines and leads on the casing surface are separated from the bypass channel 84 to avoid affecting the bypass air flow. Therefore, the engine casing of the present invention is more suitable for turbofan engines.

[0075] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0076] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection; it can be a mechanical connection, an electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside multiple components or the interaction relationship of multiple components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] In the description of the present invention, it should be understood that all terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as a limitation to the present invention.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact turbofan engine casing, used for installation in an outer duct (84), equipped with a fuel manifold (83) and a diffuser (81), characterized in that: include: A coaxially arranged casing head end portion (1) and casing tail end portion (2); The casing tail end (2) comprises a transition section casing (21) and a low-pressure turbine casing (22), the head end of the transition section casing (21) is fixedly connected to the tail end of the casing head end (1), and the tail end of the transition section casing (21) is connected to the head end of the low-pressure turbine casing (22); The outer wall of the casing head end (1) is flush with the inner ring outer wall of the outer culvert channel (84), the outer wall of the low-pressure turbine casing (22) tail end is sleeved with the inner ring inner wall of the outer culvert channel (84), and the outer diameters of the low-pressure turbine casing (22) head end and the transition section casing (21) tail end are smaller than the outer diameter of the low-pressure turbine casing (22) tail end to form a receiving chamber (4); The side wall of the transition section casing (21) is provided with a nozzle mounting seat (214) facing the storage chamber (4).

2. The compact turbofan engine casing according to claim 1, characterized in that: The transition section casing (21) comprises: a combustion chamber casing head (211), a first straight section (212), and a second straight section (213) which are sequentially connected at the head and tail ends; The outer diameter of the first straight section (212) is smaller than the outer diameter of the second straight section (213), and the outer diameters of the first straight section (212) and the second straight section (213) are smaller than the outer diameter of the rear end of the transition section casing (21).

3. The compact turbofan engine casing according to claim 2, characterized in that: The combustion chamber casing head (211) comprises: an upper head profile (2111) and a lower head profile (2112); The tail ends of the upper head profile (2111) and the lower head profile (2112) are butted against each other, the head ends of the upper head profile (2111) and the lower head profile (2112) form a predetermined angle, the head end of the upper head profile (2111) is fixedly connected to the tail end of the casing head end (1), and a plurality of nozzle mounting seats (214) are arranged in a circular array on the outer wall of the upper head profile (2111).

4. The compact turbofan engine casing according to claim 3, characterized in that: A flange member (215) is provided at the head end of the lower head profile (2112), and a flared self-locking nut (216) is installed in the mounting hole of the flange member (215).

5. The compact turbofan engine casing according to claim 2, characterized in that: The low-pressure turbine casing (22) comprises a turning portion (221) and an outward expansion portion (222) connected at the head and tail, wherein the head end of the turning portion (221) is connected to the tail end of the transition section casing (21), the outer wall of the tail end of the outward expansion portion (222) is sleeved with the inner wall of the inner ring of the outer duct (84), and a plurality of threaded holes are provided on the end surface of the tail end of the outward expansion portion (222).

6. The compact turbofan engine casing according to claim 3, used for assembling a diffuser (81), characterized in that: The casing head end (1) comprises: a diffuser casing (13), a combustion chamber casing (11), and a combustion chamber flange (12) which are sequentially connected at the head and tail ends; The diffuser casing (13) extends toward the axial centerline of the casing head end (1); the diffuser casing (13) and the combustion chamber casing (11) together form a semi-enclosed inner cavity for installing the diffuser (81); and the combustion chamber flange (12) is connected to the head end of the transition section casing (21).

7. The compact turbofan engine casing according to claim 6, characterized in that: The side wall of the diffuser casing (13) is provided with a first flange (131) and a second flange (132), and the first flange (131) and the second flange (132) are assembled with the diffuser (81) by bolts (30), so that a first chamber (5), a second chamber (6) and a third chamber (7) are formed between the diffuser casing (13) and the diffuser (81), and the first chamber (5) and the third chamber (7) are communicated with each other; A positioning step (133) adapted to the diffuser (81) is provided on the side of the side wall of the diffuser casing (13) facing the first chamber (5).

8. The compact turbofan engine casing according to claim 7, characterized in that: The side wall of the diffuser casing (13) is provided with an air bleed mounting seat (134) connected to the first chamber (5), and the air bleed mounting seat (134) is located between the first flange member (131) and the second flange member (132).

9. The compact turbofan engine casing according to claim 6, characterized in that: The combustion chamber flange (12) comprises an annular body (123), a plurality of threaded holes (121) are arranged in a circumferential array on the side wall of the annular body (123), and a stopper (122) is arranged on the inner wall of the annular body (123); The head end of the upper head profile (2111) is provided with a protruding ring block (2113) adapted to the stop (122).

10. The compact turbofan engine casing according to any one of claims 6 to 9, characterized in that: The outer wall of the combustion chamber casing (11) is provided with a valve mounting seat (111), an electric nozzle mounting seat (113) and a fixing pin mounting seat (112); The fixing pin mounting seat (112) adopts a hollow columnar structure, and the inner wall of the hollow inner cavity of the fixing pin mounting seat (112) is provided with an internal thread.

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