A turbofan engine and a method of driving a turbofan engine

Abstract

The application provides a turbofan engine and a method for driving the turbofan engine. The turbofan engine comprises a fan, a compressor, a combustion chamber and a high-pressure turbine arranged in sequence from front to back. The rotors of the fan and the compressor and the rotor of the high-pressure turbine share a rotor shaft. The turbofan engine further comprises a planetary gear reducer and a central transmission gear assembly, and the planetary gear reducer and the central transmission gear assembly are arranged on the rotor shaft. The structure of the engine is simplified, and the weight is reduced.

Description

Technical Field

[0001] This invention relates to the field of aero-engines, and particularly to a turbofan engine and a method for driving a turbofan engine. Background Technology

[0002] Aero engines have complex structures, numerous and varied parts, and require high precision in manufacturing. The large number of parts results in a high overall weight, which greatly limits further improvements in thrust-to-weight ratio. At the same time, the large number of parts also leads to poor overall reliability, and the manufacturing and assembly processes are long and difficult. Summary of the Invention

[0003] The purpose of this invention is to provide a turbofan engine.

[0004] Another object of the present invention is to provide a method for driving a turbofan engine.

[0005] According to one aspect of the present invention, a turbofan engine includes a fan, a compressor, a combustion chamber, and a high-pressure turbine, arranged sequentially from front to back; the rotors of the fan, the compressor, and the high-pressure turbine share a single rotor shaft; the turbofan engine further includes a planetary gear reducer and a central drive gear assembly, the planetary gear reducer and the central drive gear assembly being disposed on the rotor shaft; in the starting state of the turbofan engine, a starter motor drives the rotor shaft through the central drive gear assembly, the rotor shaft drives the fan through the planetary gear reducer, and the rotor shaft drives the compressor; in the operating state of the turbofan engine, the high-pressure turbine drives the rotor shaft, the rotor shaft drives the compressor, and the rotor shaft drives the fan through the planetary gear reducer.

[0006] The technical solution of this application simplifies the engine structure, reduces the number of engine parts, and lowers the engine weight by setting up a planetary gear reducer and a central transmission gear assembly, eliminating the fan supercharger stage and low-pressure turbine unit, and adopting a single rotor. The high-pressure turbine drives the fan through the planetary gear reducer. This facilitates a higher thrust-to-weight ratio, reduces assembly difficulty, and improves assembly reliability. Simultaneously, the high-bypass turbofan engine receives 80% of its power from the fan, reducing internal efficiency while maximizing fan efficiency, increasing the bypass ratio, and enhancing external bypass efficiency.

[0007] In one or more embodiments of the turbofan engine, the diameter of the fan is 3.5-4 meters.

[0008] In one or more embodiments of the turbofan engine, the turbofan engine further includes a first pivot bearing, a second pivot bearing, an intermediate casing, and a rear casing. The intermediate casing is located behind the fan, and the rear casing is located behind the high-pressure turbine. The first pivot bearing is disposed on the front journal of the rotor shaft and supports the front journal and the fan. The outer ring of the first pivot bearing is connected to the intermediate casing. The second pivot bearing is disposed on the rear journal of the rotor shaft and supports the rear journal. The outer ring of the second pivot bearing is connected to the rear casing.

[0009] In one or more embodiments of the turbofan engine, the turbofan engine further includes a fan rectifier disposed in the intermediate casing.

[0010] In one or more embodiments of the turbofan engine, the central drive gear assembly includes a driving bevel gear and a driven bevel gear, the driving bevel gear being connected to the rotor shaft and the driven bevel gear being connected to the accessory housing of the turbofan engine to drive the accessory housing.

[0011] In one or more embodiments of the turbofan engine, the planetary gear reducer includes a sun gear and planet gears, the sun gear being connected to the rotor shaft and the planet gears being connected to the fan.

[0012] In one or more embodiments of the turbofan engine, the reduction ratio of the planetary gear reducer may be selected as 3-6.

[0013] In one or more embodiments of the turbofan engine, the compressor has 6-9 stages and the high-pressure turbine has 2-4 stages.

[0014] In one or more embodiments of the turbofan engine, the front journal is provided with a bearing housing that is connected to the inner ring of the first pivot bearing, and the rotor shaft is connected to the planetary gear reducer by a first spline structure and to the central transmission gear assembly by a second spline structure.

[0015] In one or more embodiments of the turbofan engine, the front journal is further provided with a first thread and a second thread. The first thread is located on the front side of the bearing housing and is connected to a first clamping nut. The first clamping nut is used to clamp the planetary gear reducer in the axial direction. The second thread is located between the first spline structure and the second spline structure and is connected to a second clamping nut. The second clamping nut is used to clamp the central transmission gear assembly in the axial direction.

[0016] According to another aspect of the present invention, a method for driving a turbofan engine includes:

[0017] Eliminate the fan booster stage and the low-pressure turbine, increase the fan diameter, and install a planetary gear reducer and a central drive gear assembly on the rotor shaft;

[0018] The high-pressure turbine outputs a first power to the rotor shaft, which in turn drives the compressor. The rotor shaft outputs a second power through the planetary gear reducer to drive the fan, and the rotor shaft outputs a third power through the central transmission gear assembly to drive the accessory housing. Attached Figure Description

[0019] The above and other features, properties, and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features. It should be noted that these drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of protection actually claimed by the present invention, wherein:

[0020] Figure 1 A schematic diagram of the structure of a turbofan engine for comparison.

[0021] Figure 2 This is a schematic diagram of the structure of a turbofan engine according to one embodiment;

[0022] Figure 3 This is a schematic diagram of the structure of the front journal of a rotor shaft according to one embodiment;

[0023] Figure 4 This is a schematic diagram of the structure of a central transmission gear assembly according to one embodiment;

[0024] Figure 5 This is a schematic diagram of the sun gear of a planetary gear reducer according to one embodiment.

[0025] Figure label:

[0026] 100 - Fan blade, 200 - Fan booster stage, 300 - Fan rectifier, 400 - Core engine, 4001 - Core engine stator, 4002 - Core engine rotor, 500 - Low-pressure turbine, 5001 - Low-pressure turbine stator, 5002 - Low-pressure turbine rotor, 61, 62, 63, 64, 65 - Support points, 71, 72, 73 - Load-bearing casing;

[0027] 1-Fan, 2-Compressor, 3-Combustion chamber, 4-High-pressure turbine;

[0028] 5-Rotor shaft, 52-Rear journal;

[0029] 51-Front journal, 511-Bearing housing, 512-First thread, 513-Second thread;

[0030] 6-Planetary gear reducer, 601-Sun gear;

[0031] 7-Central drive gear assembly, 701-Driving bevel gear, 702-Driven bevel gear;

[0032] 8-First pivot bearing, 9-Second pivot bearing;

[0033] 10-Intermediate casing, 11-Rear casing;

[0034] 12-Shoulder;

[0035] 13-First spline structure, 131-External spline, 132-Internal spline;

[0036] 14 - Second spline structure, 141 - External spline, 142 - Internal spline. Detailed Implementation

[0037] Reference will now be made in detail to various embodiments of the invention, examples of which are shown in the accompanying drawings and described below. Although the invention will be described in conjunction with exemplary embodiments, it should be understood that this specification is not intended to limit the invention to those exemplary embodiments. Rather, the invention is intended to cover not only these exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of the invention as defined by the appended claims.

[0038] In the following description, the orientation or positional relationship indicated by the terms "axial", "front", "rear", "inner", "outer" or other directional terms is based on the orientation or positional relationship shown in the accompanying drawings and is only for the purpose of facilitating the description of the invention and simplifying the description, and is not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0039] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment" and / or "one embodiment" refers to a particular feature, structure, or characteristic associated with at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0040] With the increasing demand for improving the thrust-to-weight ratio of engines, there is a need to further reduce engine weight.

[0041] The inventors of this application discovered through research that conventionally configured aero-engines currently have complex structures, with the support system alone typically involving 5-8 support points, and the load-bearing casing generally requiring 3-4. For example... Figure 1 The existing engine shown includes fan blades 100, a fan booster stage 200, a fan rectifier 300, a core engine 400, a low-pressure turbine 500, five pivot points 61, 62, 63, 64, and 65, and three load-bearing casings 71, 72, and 73. The core engine 400 includes a core engine stator 4001 and a core engine rotor 4002, and the low-pressure turbine 500 includes a low-pressure turbine stator 5001 and a low-pressure turbine rotor 5002. It is evident that the complex structure, numerous types of parts, and large overall weight significantly limit further improvements in thrust-to-weight ratio. Furthermore, the large number of parts leads to poor overall reliability and increases the difficulty and time required for manufacturing and assembly.

[0042] Based on the above considerations, the inventors, after in-depth research, designed a turbofan engine. By incorporating a planetary gear reducer and a central transmission gear assembly, the fan supercharger stage and low-pressure turbine unit are eliminated. A single rotor is used, with the high-pressure turbine driving the fan via the planetary gear reducer. This simplifies the engine structure, reduces the number of engine parts, lowers engine weight, facilitates a higher thrust-to-weight ratio, reduces assembly difficulty, and improves assembly reliability. Simultaneously, the high-bypass turbofan engine utilizes the fan for 80% of its power, minimizing internal efficiency while maximizing fan efficiency, thereby increasing the bypass ratio and enhancing external bypass efficiency.

[0043] In addition, this application increases the fan diameter and reduces the fan speed to maximize the fan's advantages, increase the bypass airflow, further increase the engine bypass ratio, and increase the bypass thrust.

[0044] In addition, this application only requires the use of a first pivot bearing, a second pivot bearing, an intermediate casing, and a rear casing, reducing the five pivots in the comparative scheme to two pivots at the front and rear, and reducing the three load-bearing casings to two load-bearing casings, further reducing the number of engine parts, reducing weight, improving engine efficiency, and improving assembly reliability.

[0045] Although the turbofan engine disclosed in this application is applicable to turbofan engines to achieve the effect of simplifying the structure and reducing weight, it is not limited thereto. Whether it is a military aero engine or a civil aero engine, it can also be applied to the structural design and manufacturing of ground gas turbines, marine gas turbines or gas generators. A gas generator usually refers to a structure including a low-pressure compressor (if present), a core engine, a low-pressure turbine (if present), etc. As long as the purpose is to simplify the structure and improve the thrust-to-weight ratio, the structural concept of the turbofan engine disclosed in this application can be applied.

[0046] Figure 1 The turbofan engine and components shown in the accompanying drawings of the embodiments of this application are all radially symmetrical. Figures 1 to 5 For the sake of brevity, only the radial half of the relevant component is shown.

[0047] refer to Figure 2 As shown, in one embodiment, the turbofan engine 1000 may have the following specific structure: a fan 1, a compressor 2, a combustion chamber 3, and a high-pressure turbine 4, arranged sequentially from front to back; the rotors of the fan 1, the compressor 2, and the high-pressure turbine 4 share a single rotor shaft 5; the turbofan engine 1000 also includes a planetary gear reducer 6 and a central transmission gear assembly 7, which are disposed on the rotor shaft 5; in the starting state of the turbofan engine 1000, the starter (not shown in the figure) drives the rotor shaft 5 through the central transmission gear assembly 7, the rotor shaft 5 drives the fan 1 through the planetary gear reducer 6, and the rotor shaft 5 drives the compressor 2; in the operating state of the turbofan engine 1000, the high-pressure turbine 4 drives the rotor shaft 5, the rotor shaft 5 drives the compressor 2, and the rotor shaft 5 drives the fan 1 through the planetary gear reducer 6.

[0048] "Fan 1" here refers to a single-stage fan, excluding the fan booster stage.

[0049] Here, "compressor 2" refers to the high-pressure compressor, excluding the low-pressure compressor or fan booster stage.

[0050] Here, "combustion chamber 3" refers to the component where air enters the compressor 2 via fan 1, is pressurized, and then mixes with fuel to produce combustion gas. The resulting high-temperature, high-pressure gas enters the high-pressure turbine 4, expands, and performs work to drive the high-pressure turbine 4 to rotate the compressor 2.

[0051] The "planetary gear reducer 6" mentioned here refers to a gear assembly that is generally composed of a sun gear and multiple planet gears. The sun gear receives the rotational speed of the rotor shaft and transmits it to the planet gears. The planet gears reduce the rotational speed and output to drive the fan. The size and number of teeth of the sun gear are smaller than those of the planet gears, so as to achieve the purpose of speeding up the fan.

[0052] The "central drive gear assembly 7" here refers to the assembly where the driving gear receives the rotor shaft's rotational speed and transmits it to the driven gear. The driven gear then outputs its rotational speed to drive the accessory housing, completing the power transmission. When the engine starts, the starter motor drives the accessory housing, which in turn drives the driven gear. The driven gear then transmits torque to the driving gear, driving the rotor shaft to rotate the compressor.

[0053] The beneficial effects of this embodiment are that by setting a planetary gear reducer and a central transmission gear assembly, eliminating the fan supercharger stage and low-pressure turbine unit, and adopting a single rotor, with the high-pressure turbine driving the fan through the planetary gear reducer, the engine structure is simplified, the number of engine parts is reduced, the engine weight is lowered, which is conducive to improving the thrust-to-weight ratio, reducing assembly difficulty, and improving engine reliability. At the same time, the high-bypass turbofan engine provides 80% of its power to the fan, weakening the internal efficiency, maximizing the fan efficiency, increasing the bypass ratio, and improving the external bypass efficiency.

[0054] Continue to refer to Figure 2 As shown, in some embodiments, the specific structure of fan 1 can be such that the diameter of fan 1 is 3.5-4 meters. The beneficial effect of this configuration is that... Figure 1 The comparative design shown has a maximum fan diameter of 3.4 meters. Increasing the fan diameter and reducing the fan speed maximizes the fan's advantages, increases the bypass airflow, further improves the engine's bypass ratio, and increases bypass thrust. It can be understood that... Figure 2 The fan shown is half the radial direction of a complete fan, i.e. Figure 2 Only the radius of fan 1 is shown.

[0055] refer to Figure 1 Combination Figure 2 As shown, in some embodiments, the specific structure of the turbofan engine 1000 may include a first pivot bearing 8, a second pivot bearing 9, an intermediate casing 10, and a rear casing 11. The intermediate casing 10 is located behind the fan 1, and the rear casing 11 is located behind the high-pressure turbine 4. The first pivot bearing 8 is disposed on the front journal 51 of the rotor shaft 5 and is used to support the front journal 51 and the fan 1. The outer ring of the first pivot bearing 8 is connected to the intermediate casing 10. The second pivot bearing 9 is disposed on the rear journal 52 of the rotor shaft 5 and supports the rear journal 52. The outer ring of the second pivot bearing 9 is connected to the rear casing 11. The beneficial effect of this configuration is that, compared to the five support points 61, 62, 63, 64, 65 and three load-bearing housings 71, 72, 73 in the comparative scheme, this embodiment only needs to use the first support bearing 8, the second support bearing 9, the intermediate housing 10, and the rear housing 11, reducing the five support points in the comparative scheme to two support points at the front and rear, and reducing the three load-bearing housings to two load-bearing housings, further reducing the number of engine parts, reducing weight, improving engine efficiency, and improving assembly reliability.

[0056] refer to Figure 2As shown, in some embodiments, the turbofan engine 1000 may include a fan rectifier (not shown) disposed in the intermediate casing 10. The advantage of this configuration is that, by eliminating the booster stage and pivots 61 and 62, placing the fan rectifier in the intermediate casing 10 further reduces the axial distance between the fan 1 and the intermediate casing 10, compared to... Figure 1 The comparative scheme shown can reduce the axial dimension by about 500mm, saving the space occupied by the fan rectifier itself and making the axial structure of the turbofan engine more compact.

[0057] In some embodiments, the fan rectifier and the intermediate casing support plate are integrated into a design. Specifically, the blades of the fan rectifier and the support plate of the intermediate casing are arranged in an alternating manner. The advantage of this arrangement is that it saves space and makes the overall structure more compact.

[0058] refer to Figures 2 to 4 As shown, in some embodiments, the specific structure of the central drive gear assembly 7 may include a driving bevel gear 701 and a driven bevel gear 702. The driving bevel gear 701 is connected to the rotor shaft 5, and the driven bevel gear 702 is connected to the accessory housing (not shown in the figure) of the turbofan engine 1000 to drive the accessory housing. Specifically, when the engine starts, the starter drives the accessory housing, outputting torque to the driving bevel gear 701 through the driven bevel gear 702. The driving bevel gear 701 drives the rotor shaft 5 to rotate, and the rotor shaft 5 drives the compressor 2 to rotate. When the engine is running, the rotor shaft 5 drives the driving bevel gear 701, and the driving bevel gear 701 transmits power to the accessory housing through the driven bevel gear 702. The accessory housing drives accessories such as hydraulic pumps and generators mounted on the accessory housing to ensure the normal operation of aircraft hydraulic equipment, electronic components, etc. The beneficial effect of this embodiment is that the central lip-driven gear assembly has a simple structure, fewer parts, further reduces the engine weight, and is easy to manufacture and assemble.

[0059] refer to Figure 2 , Figure 3 , Figure 5 As shown, in some embodiments, the planetary gear reducer 6 may specifically include a sun gear 601 and planet gears (not shown in the figure). The sun gear 601 is connected to the rotor shaft 5, and the planet gears are connected to the fan 1. Specifically, the rotation of the rotor shaft 5 drives the sun gear 601, which in turn drives the planet gears to output torque to the fan 1, thus driving the fan 1 to rotate. The advantage of this configuration is that it facilitates the adjustment of the speed range of the reducer's output to the fan, reducing it to the most suitable fan speed and maximizing the fan's efficiency.

[0060] refer to Figure 2As shown, in some embodiments, the specific structure of the planetary gear reducer 6 can also be such that the reduction ratio of the planetary gear reducer 6 can be selected as 3-6. The reduction ratio is adjusted according to the rotor speed of the high-pressure turbine to determine the specific value, which helps to maximize the efficiency of the fan.

[0061] Continue to refer to Figure 2 As shown, in some embodiments, the turbofan engine 1000 may have a compressor 2 with 6-9 stages and a high-pressure turbine 4 with 2-4 stages. The advantage of this configuration is that, since the high-pressure turbine output power is redistributed to the fan and compressor via the rotor shaft, adjusting the number of stages in the compressor and high-pressure turbine—appropriately reducing the compressor stages and appropriately increasing the high-pressure turbine stages—can help to appropriately reduce the rotor speed and turbine inlet temperature, thus contributing to higher bypass thrust.

[0062] refer to Figure 2 Combination Figure 3 As shown, in some embodiments, the specific structure of the front journal 51 may include a bearing housing 511 that is connected to the inner ring of the first pivot bearing 8. The rotor shaft 5 is connected to the planetary gear reducer 6 using a first spline structure 13 and to the central transmission gear assembly 7 using a second spline structure 14. Specifically, the sun gear 601 of the planetary gear reducer 6 is connected to the rotor shaft 5 using the first spline structure 13, and the driving bevel gear 701 of the central transmission gear assembly 7 is connected to the rotor shaft 5 using the second spline structure 14. The advantage of this configuration is that using a spline structure connection for torque transmission is easier to install and position compared to using a bearing connection, and the torque transmission effect is better with less force loss. Furthermore, the direct connection between the torque transmission components eliminates the need for additional parts, resulting in a simple structure and no added weight.

[0063] In some embodiments, such as Figures 2 to 5 As shown, the rotor shaft 5 has external splines 131 and 141 of a first spline structure 13 and a second spline structure 14. The inner ring of the sun gear 601 has an internal spline 132 of the first spline structure 13 that mates with the external spline 131. The inner ring of the drive bevel gear 701 has an internal spline 142 of the second spline structure 14 that mates with the external spline 141. This configuration is simple and easy to manufacture. It can be understood that the sun gear 601 and the drive bevel gear 701 could also have external splines 131 and 141 respectively, and the rotor shaft 5 could have internal splines 132 and 142 that mate with the external splines 131 and 141.

[0064] refer to Figure 3As shown, in some embodiments, the front journal 51 may have a specific structure in which it is further provided with a first thread 512 and a second thread 513. The first thread 512 is located on the front side of the bearing housing 511 and is connected to a first clamping nut (not shown in the figure). The first clamping nut is used to clamp the first pivot bearing 8 axially. The second thread 513 is located between the first spline structure 13 and the second spline structure 14 and is connected to a second clamping nut (not shown in the figure). The second clamping nut is used to clamp the central transmission gear assembly 7 axially. The beneficial effect of this arrangement is that it prevents axial movement of the first pivot bearing, planetary gear reducer, and central transmission gear assembly, making the structure more stable. The use of threaded nuts results in a simple structure, low manufacturing cost, easy assembly, and high reliability.

[0065] In some embodiments, such as Figure 2 Combination Figure 3 As shown, the front journal 52 is also provided with a shoulder 12, which is located on the rear side of the second spline structure 14 to stop the central transmission gear assembly 7 in the axial direction, making the entire torque transmission structure more stable and reliable.

[0066] In one embodiment, the specific steps of the method for driving a turbofan engine may include:

[0067] Eliminate the fan booster stage and the low-pressure turbine, increase the fan diameter, and install a planetary gear reducer and a central drive gear assembly on the rotor shaft;

[0068] The high-pressure turbine outputs the first power to the rotor shaft, which in turn drives the compressor. The rotor shaft outputs the second power through the planetary gear reducer to drive the fan, and the rotor shaft outputs the third power through the central transmission gear assembly to drive the accessory housing.

[0069] The advantages of this design are that by using a single rotor, with the fan driven by a high-pressure turbine through a planetary gear reducer, only two support points (front and rear) and two load-bearing casings are needed for support, simplifying the engine structure. Compared to the comparative design, it reduces the number of parts by nearly half and the weight by nearly half, which is beneficial for improving the thrust-to-weight ratio. It also reduces assembly difficulty and improves engine reliability. At the same time, increasing the fan diameter and reducing the fan speed maximizes the fan's advantages. In a high-bypass turbofan engine, the fan provides 80% of the power, weakening the internal efficiency and increasing the external airflow, further increasing the engine's bypass ratio and improving the external thrust.

[0070] In summary, the beneficial effects of the turbofan engine 1000 and the method for driving the turbofan engine 1000 described in the above embodiments include, but are not limited to, one or a combination of the following:

[0071] 1. The turbofan engine of this application simplifies the engine structure, reduces the number of engine parts, and lowers the engine weight by setting up a planetary gear reducer and a central transmission gear assembly, eliminating the fan supercharger stage and low-pressure turbine unit, and adopting a single rotor. The high-pressure turbine drives the fan through the planetary gear reducer. This facilitates a higher thrust-to-weight ratio, reduces assembly difficulty, and improves assembly reliability. Simultaneously, the high-bypass turbofan engine receives 80% of its power from the fan, weakening internal efficiency while maximizing fan efficiency, increasing the bypass ratio, and enhancing external bypass efficiency.

[0072] 2. The method for driving a turbofan engine in this application employs a single rotor, with a high-pressure turbine driving the fan via a planetary gear reducer. Support is achieved using only two pivot points (front and rear) and two load-bearing casings, simplifying the engine structure. Compared to comparative solutions, this reduces the number of parts by nearly half and the weight by nearly half, improving the thrust-to-weight ratio, reducing assembly difficulty, and enhancing engine reliability. Simultaneously, by increasing the fan diameter and reducing the fan speed, the advantages of the fan are maximized. In a high-bypass turbofan engine, the fan provides 80% of the power, reducing internal efficiency and increasing external airflow, further improving the engine's bypass ratio and external thrust.

[0073] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A turbofan engine, characterized in that, The turbofan engine includes a fan, compressor, combustion chamber, and high-pressure turbine, arranged sequentially from front to back. The rotors of the fan, compressor, and high-pressure turbine share a single rotor shaft. The turbofan engine also includes a planetary gear reducer and a central drive gear assembly, which are mounted on the rotor shaft. In the starting state of the turbofan engine, the starter drives the rotor shaft via the central drive gear assembly, the rotor shaft drives the fan via the planetary gear reducer, and the rotor shaft drives the compressor. In the operating state of the turbofan engine, the high-pressure turbine drives the rotor shaft, the rotor shaft drives the compressor, and the rotor shaft drives the fan through the planetary gear reducer; The turbofan engine further includes a first pivot bearing, a second pivot bearing, an intermediate casing, and a rear casing. The intermediate casing is located behind the fan, and the rear casing is located behind the high-pressure turbine. The first pivot bearing is disposed on the front journal of the rotor shaft and is used to support the front journal and the fan. The outer ring of the first pivot bearing is connected to the intermediate casing. The second pivot bearing is disposed on the rear journal of the rotor shaft and supports the rear journal. The outer ring of the second pivot bearing is connected to the rear casing.

2. The turbofan engine according to claim 1, characterized in that, The fan has a diameter of 3.5-4 meters.

3. The turbofan engine according to claim 1, characterized in that, The turbofan engine also includes a fan rectifier disposed in the intermediate casing.

4. The turbofan engine according to claim 1, characterized in that, The central transmission gear assembly includes a driving bevel gear and a driven bevel gear. The driving bevel gear is connected to the rotor shaft, and the driven bevel gear is connected to the accessory housing of the turbofan engine to drive the accessory housing.

5. The turbofan engine according to claim 1, characterized in that, The planetary gear reducer includes a sun gear and planet gears. The sun gear is connected to the rotor shaft, and the planet gears are connected to the fan.

6. The turbofan engine according to claim 5, characterized in that, The reduction ratio of the planetary gear reducer can be selected as 3-6.

7. The turbofan engine according to claim 1, characterized in that, The compressor has 6-9 stages, and the high-pressure turbine has 2-4 stages.

8. The turbofan engine according to claim 1, characterized in that, The front journal is provided with a bearing seat, which is connected to the inner ring of the first pivot bearing. The rotor shaft is connected to the planetary gear reducer by a first spline structure and to the central transmission gear assembly by a second spline structure.

9. The turbofan engine according to claim 8, characterized in that, The front journal is also provided with a first thread and a second thread. The first thread is located on the front side of the bearing housing and is connected to a first clamping nut. The first clamping nut is used to clamp the planetary gear reducer in the axial direction. The second thread is located between the first spline structure and the second spline structure and is connected to a second clamping nut. The second clamping nut is used to clamp the central transmission gear assembly in the axial direction.

10. A method for driving a turbofan engine, characterized in that, For driving the turbofan engine as described in claim 1, comprising: Eliminate the fan booster stage and the low-pressure turbine, increase the fan diameter, and install a planetary gear reducer and a central drive gear assembly on the rotor shaft; The high-pressure turbine outputs a first power to the rotor shaft, which in turn drives the compressor. The rotor shaft outputs a second power through the planetary gear reducer to drive the fan, and the rotor shaft outputs a third power through the central transmission gear assembly to drive the accessory housing.

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