CN113279859B

CN113279859B - Variable-boost-level-based ultra-wide adjustable-bypass-ratio turbofan engine structure

Info

Publication number: CN113279859B
Application number: CN202110685975.2A
Authority: CN
Inventors: 赵胜丰; 卢新根; 徐纲; 朱俊强
Original assignee: Institute of Engineering Thermophysics of CAS
Current assignee: Institute of Engineering Thermophysics of CAS
Priority date: 2021-06-21
Filing date: 2021-06-21
Publication date: 2022-10-21
Anticipated expiration: 2041-06-21
Also published as: CN113279859A

Abstract

The invention provides a variable-supercharging-stage-based super-wide adjustable bypass ratio double-shaft turbofan engine structure, which aims at the defects and shortcomings that the supercharging stage and a fan in the existing double-shaft turbofan engine are coaxial and rotate at the same speed, the cruising height of a platform is higher and higher, the characteristic Reynolds number of the supercharging stage is continuously reduced due to low characteristic speed and small size of the supercharging stage, the boundary layer of the supercharging stage is separated, and the performance is sharply attenuated, and the supercharging stage is in driving connection with a high-pressure shaft through a variable-speed-ratio reduction gear box; when the engine is in high-speed cruise, the variable reduction ratio gearbox is set to be a low reduction ratio, so that the rotating speed of the boosting stage is relatively high, the mass flow absorbed by the high-pressure compressor is large, and the bypass ratio of the engine is relatively small.

Description

Variable-supercharging-stage-based super-wide adjustable bypass ratio turbofan engine structure

Technical Field

The invention belongs to the field of aviation turbofan engines, relates to a variable supercharging stage-based bypass ratio ultra-wide adjustable turbofan engine structure, and particularly relates to a pneumatic layout structure form applied to a gear-driven supercharging stage in a double-shaft turbofan engine, and the reduction ratio is variable.

Background

In a medium bypass ratio turbofan engine for an unmanned aerial vehicle at high altitude and long endurance, a multi-stage low-pressure compressor (booster stage) is often arranged in a bypass flow passage behind a fan. Because the booster stage and the fan are coaxial and rotate at the same speed, and the radial size of the blade tip of the booster stage is much smaller than that of the blade tip of the fan, the tangential speed of the blade tip of the booster stage is low, the processing capacity is insufficient, the overall required pressure ratio is often realized by multiple stages, and the matching performance of the booster stage under the non-designed rotating speed is poor. And as the cruising height of the platform is higher and higher, the characteristic reynolds number of the booster stage is reduced continuously due to low characteristic speed and small size of the booster stage, so that the boundary layer of the booster stage is easy to separate, and the performance is reduced rapidly.

Taking a turbofan engine with a certain conventional layout as an example, as shown in fig. 1, a fan (2) and a booster stage (3) are connected with a low-pressure turbine (7) through a low-pressure shaft (4), and the work of the fan (2) and the booster stage (3) is provided by the low-pressure turbine (7); the high-pressure compressor (5) is connected with the high-pressure turbine (6) through a high-pressure shaft (8), and the work required by the high-pressure compressor (5) is provided by the high-pressure turbine (6); the low-pressure shaft (4) and the high-pressure shaft (8) both rotate about a center of rotation (1).

As can be seen in FIG. 1, the tip diameter of the booster stage (3) is about 60% of the tip diameter of the fan (2), and when the fan tip speed is limited by the existing material system (generally not more than 500 m/s), the tangential tip speed of the booster stage will also be limited (less than 300 m/s); and the size of the boost stage is also about 60% of the fan size; when the platform is cruising at 20km high altitude, the inlet airflow density is also greatly reduced to about 10% of the ground state, thereby causing the characteristic Reynolds number of the booster stage to be reduced to 10 ⁵ The Reynolds number is far lower than the self-modulus Reynolds number, has obvious Reynolds number effect, is easy to cause the surface separation of the blade, and causes the performance reduction or the stability reduction of a compression system, and is extremely dangerous.

Meanwhile, the existing platform often needs to work in several different states for a long time, and the aero-engine also needs to have a low fuel consumption rate in the states and can output sufficient thrust, so that the real-time adjustment of the engine state needs to be realized.

The Chinese patent application CN201911292493.X discloses a pneumatic layout structure of a turbofan engine with a high-pressure shaft directly driving a booster stage, which aims to further improve the bypass ratio of the double-shaft turbofan engine and reduce the noise level of the fan, improve the matching characteristic of the booster stage at a non-designed rotating speed under the condition of keeping the total pressure ratio of the booster stage unchanged, and ensure that the high-pressure shaft directly drives the booster stage by changing the driving mode of the booster stage and arranging a reduction gear device between the high-pressure shaft and the booster stage, the tangential speed of the blade tip of the booster stage is adjusted by the reduction gear device, the boosting capacity of the booster stage is enhanced under a higher tangential speed, and the total stage of the booster stage can be properly reduced under the condition of keeping the ratio of the booster stage unchanged, so that the bypass ratio of the double-shaft turbofan engine is improved and the noise level of the fan is reduced. However, the bypass ratio of the turbofan engine cannot be changed during the operation process, and when the flight platform flies at different heights and speeds, the bypass ratio of the turbofan engine cannot be changed to enable the engine to work at the optimal performance, so that the flight time and the flight range of the flight platform cannot be met at the same time. According to the analysis, the low Reynolds number effect of the supercharging stage can be restrained in the double-shaft turbofan engine for the unmanned aerial vehicle during high-altitude long-endurance, and the realization of adjustable performance is an important design problem at present.

Disclosure of Invention

The invention provides a variable-supercharging-stage-based super-wide adjustable turbofan engine structure, and particularly relates to a pneumatic layout structure form of a gear-driven supercharging stage applied to a double-shaft turbofan engine, wherein the pneumatic layout structure form is variable in reduction ratio.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a variable-supercharging-stage-based ultra-wide adjustable-bypass-ratio double-shaft turbofan engine structure comprises a fan, a supercharging stage, a low-pressure shaft, a high-pressure compressor, a high-pressure turbine, a low-pressure turbine and a high-pressure shaft, wherein the fan, the supercharging stage, the high-pressure compressor, the high-pressure turbine and the low-pressure turbine are sequentially arranged along the axial direction, the fan and the low-pressure turbine are directly connected with the low-pressure shaft in a driving manner, the high-pressure compressor and the high-pressure turbine are directly connected with the high-pressure shaft in a driving manner, and the variable-supercharging-stage-based ultra-wide adjustable-bypass-ratio double-shaft turbofan engine structure is characterized in that,

the supercharging stage is in driving connection with the high-pressure shaft through a variable speed ratio reduction gearbox, and when the engine is in low-speed cruising, the variable speed ratio reduction gearbox is set to be in a high speed reduction ratio, so that the rotating speed of the supercharging stage is relatively low, the total temperature and pressure of inlet airflow of the high-pressure compressor are relatively low, and the bypass ratio of the engine is relatively large; when the engine is in high-speed cruise, the variable reduction ratio gearbox is set to be a low reduction ratio, so that the rotating speed of the boosting stage is relatively high, the mass flow absorbed by the high-pressure compressor is large, and the bypass ratio of the engine is relatively small;

the booster stage is located on the inner side of a flow dividing island in the radial direction, a flow dividing cone is arranged on the lower portion of the flow dividing island, airflow passes through the fan and is divided into an inner duct and an outer duct by the flow dividing island, an inner contour line of the flow dividing island and a fan outlet hub form a booster stage flow channel, the airflow passing through the booster stage is divided into two airflows by the flow dividing cone, one airflow enters the inner duct, and the other airflow enters the outer duct from an axial gap between the flow dividing island and the flow dividing cone and is mixed with the outer duct airflow separated by the flow dividing island.

Preferably, the variable-speed-ratio reduction gearbox is a planetary gear reduction gearbox and at least comprises a sun gear, an inner gear ring and a plurality of layers of planetary gear sets arranged between the sun gear and the inner gear ring, wherein the sun gear is directly connected with the high-pressure shaft in a driving way, the inner gear ring is connected with the booster stage in a driving way, and the variable-speed reduction ratio is realized by meshing different planetary gear sets.

Further, in order to ensure uniform airflow at the inlet of the high-pressure compressor, the flow rate of the boosting stage is generally more than 10% greater than the flow rate sucked by the high-pressure compressor, and if the flow rate of the boosting stage is too large, the mixing loss of the culvert runner is increased, so that the uniformity of the culvert runner and the aerodynamic performance of the culvert runner need to be considered at the same time.

Preferably, the booster stage comprises a booster stage rotor and a booster stage stator, and a culvert stator is arranged upstream of the booster stage.

Preferably, outer culvert guide vanes which are uniformly distributed along the circumferential direction are arranged between the outer molded lines of the flow dividing island and the fan casing.

Compared with the prior art, the variable-supercharging-stage-based super-wide adjustable bypass ratio double-shaft turbofan engine structure has the advantages that the supercharging stage is in driving connection with a high-pressure shaft through a variable-speed-ratio reduction gear box, when the engine is in low-speed cruising, the variable-speed-reduction gear box is set to be a high speed reduction ratio, so that the rotating speed of the supercharging stage is relatively low, the total temperature and the total pressure of inlet airflow of a high-pressure compressor are relatively low, and the bypass ratio of the engine is relatively large; when the engine is in high-speed cruise, the variable reduction ratio gearbox is set to be a low reduction ratio, so that the rotating speed of the boosting stage is relatively high, the mass flow absorbed by the high-pressure compressor is large, and the bypass ratio of the engine is relatively small.

Drawings

FIG. 1 is a schematic view of a conventional turbofan engine rotor structure;

FIG. 2 is a schematic view of a variable boost stage super-wide adjustable bypass ratio turbofan engine configuration of the present invention;

FIG. 3 is a schematic diagram of a bypass ratio ultra-wide adjustable compression system with variable boost stages;

fig. 4 is a schematic view of a variable reduction ratio gear.

Description of the reference numerals:

the high-pressure turbine comprises a rotation center 1, a fan 2, a pressurizing stage 3, a low-pressure shaft 4, a high-pressure compressor 5, a high-pressure turbine 6, a low-pressure turbine 7, a high-pressure shaft 8, a variable reduction ratio gear 9, a culvert stator 10, a pressurizing stage rotor 11, a pressurizing stage stator 12, a culvert guide vane 13, a diversion island 14, a fan casing 15, a pressurizing stage culvert overflow 16, culvert airflow 17, culvert airflow 18 and an axial gap 19 between the diversion island and a diversion cone.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments, which are part of the present invention and are not intended to be all of the embodiments, are intended to illustrate the present invention and should not be construed as limiting the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 2, the variable boost stage-based super-wide adjustable turbofan engine structure comprises a fan 2, a boost stage 3, a low-pressure shaft 4, a high-pressure compressor 5, a high-pressure turbine 6, a low-pressure turbine 7 and a high-pressure shaft 8, wherein the fan 2, the boost stage 3, the high-pressure compressor 5, the high-pressure turbine 6 and the low-pressure turbine 7 are sequentially arranged along an axial direction, the fan 2 and the low-pressure turbine 7 are directly driven and connected by the low-pressure shaft 4, and the power required by the fan 2 is provided by the low-pressure turbine 7; the high-pressure compressor 5 and the high-pressure turbine 6 are directly connected by a high-pressure shaft 8 in a driving way, the power of the booster stage 3 and the high-pressure compressor 5 is provided by the high-pressure turbine 6, a variable speed ratio reduction gear box 9 is arranged between the booster stage 3 and the high-pressure shaft 8, and the tip tangential speed of the booster stage 3 can be adjusted in real time according to the flight working condition requirement in the running process of the engine through the variable speed ratio reduction gear box 9; when the variable reduction ratio gearbox 9 selects a high reduction ratio, the rotating speed of the boosting stage 3 is relatively low, the boosting capacity is relatively low, the total temperature and the total pressure of the inlet airflow 17 of the high-pressure compressor are relatively low, so that the mass flow entering the high-pressure compressor is reduced, the bypass ratio is relatively large, and the variable reduction ratio gearbox is suitable for cruising at a low rotating speed; when the variable reduction ratio gearbox 9 selects a low reduction ratio, the rotating speed of the booster stage 3 is relatively high, the boosting capacity is high, the total temperature total pressure of the inlet airflow 17 of the high-pressure compressor is relatively high, the mass flow absorbed by the high-pressure compressor is large, the bypass ratio of the engine is relatively low, the engine is suitable for cruising at a relatively high speed, and relatively large thrust can be improved. For example, when the speed reduction ratio is changed from 1.

The specific compression system configuration is shown in fig. 3, after the air flow passes through a fan 2, the air flow is divided into two culvert air flows, namely an outer culvert air flow 18 and an inner culvert air flow 17, by a diversion island 14 inner contour line and a fan outlet hub, the air flow passing through the pressurization level 3 is divided into two air flows by a following diversion cone, namely a pressurization level culvert overflow 16 and an inner culvert air flow 17, one inner culvert air flow 17 enters the inner culvert high pressure, the other pressurization level culvert overflow 16 enters the outer culvert through an axial gap 19 between the diversion island and the diversion cone and is mixed with the outer culvert air flow 18 divided by the diversion island, in order to ensure that the air flow at the inlet of the high-pressure compressor is uniform, the

flow

16 and 17 of the general pressurization level is more than 10% larger than the flow 17 sucked by the high-pressure compressor, if the flow of the pressurization level is too large, the mixing loss of the outer culvert air flow is increased, and the uniformity of the culvert air flow and the aerodynamic performance of the outer culvert air flow are both considered. The invention changes the culvert flow by changing the total temperature and the total pressure of the airflow at the culvert inlet, thereby changing the culvert ratio. If the pressure stage and the high-pressure compressor are the same duct, the matching problem of the pressure stage and the high-pressure compressor is serious in the process of changing the rotating speed of the pressure stage. And after the invention adopts the diversion island structure, the diversion cone is arranged at the back, so that the pneumatic problem faced by the above can be avoided. In the process of changing the rotating speed of the pressurizing level, the total temperature and the total pressure of an outlet are changed, the content flow is determined by the high-pressure pumping capacity, and part of flow of the pressurizing level can overflow to the content, so that the matching problem of main flow is not influenced.

The variable reduction gear box applied in the invention generally adopts double-layer I and II planetary gears as shown in figure 4, wherein a sun gear is directly connected with a high-pressure shaft, a planetary gear is fixed, an outer ring gear is connected with a boosting stage, and variable reduction ratio is realized by meshing different planetary gear sets. Because the gear only transmits the work required by the supercharging stage, the power is small, the heating problem is not large, the size and the quality of the variable reduction ratio gear are also controllable, and the variable reduction ratio gear is not limited by the design of the variable reduction gear, so that the ultra-wide adjustment of the bypass ratio of the turbofan engine can be realized.

The object of the present invention is fully effectively achieved by the above embodiments. Those skilled in the art will appreciate that the present invention includes, but is not limited to, what is described in the accompanying drawings and the foregoing detailed description. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications within the spirit and scope of the appended claims.

Claims

1. A variable-supercharging-stage-based double-shaft turbofan engine structure with an ultra-wide and adjustable bypass ratio comprises a fan, a supercharging stage, a low-pressure shaft, a high-pressure compressor, a high-pressure turbine, a low-pressure turbine and a high-pressure shaft, wherein the fan, the supercharging stage, the high-pressure compressor, the high-pressure turbine and the low-pressure turbine are sequentially arranged along the axial direction, the fan and the low-pressure turbine are directly connected with the low-pressure shaft in a driving manner, and the high-pressure compressor and the high-pressure turbine are directly connected with the high-pressure shaft in a driving manner,

the supercharging stage is in driving connection with the high-pressure shaft through a variable speed ratio reduction gear box, when the engine is in low-speed cruising, the variable speed ratio reduction gear box is set to be in a high speed reduction ratio, so that the rotating speed of the supercharging stage is relatively low, the total temperature and pressure of inlet airflow of the high-pressure compressor are relatively low, and the bypass ratio of the engine is relatively large; when the engine is in high-speed cruise, the variable-speed-ratio reduction gearbox is set to be in a low reduction ratio, so that the rotating speed of the boosting stage is relatively high, the mass flow absorbed by the high-pressure compressor is large, and the bypass ratio of the engine is relatively small;

the booster stage is radially positioned at the inner side of a flow dividing island, outer culvert guide vanes which are uniformly distributed along the circumferential direction are arranged between an outer molded line of the flow dividing island and a fan casing, a flow dividing cone is arranged at the lower part of the flow dividing island, an axial gap is arranged between the flow dividing island and the flow dividing cone, the flow dividing island and the flow dividing cone jointly form an inner culvert flow channel casing, an air flow channel between the outer sides of the flow dividing island and the flow dividing cone and the inner side of the fan casing integrally form an outer culvert, an air flow channel inside the flow dividing island and the flow dividing cone integrally form an inner culvert, and an inner culvert part between the inner molded line of the flow dividing island and a fan outlet hub forms a booster stage flow channel section,

after passing through the fan, the airflow enters the pressurizing stage flow channel sections of the outer duct and the inner duct respectively under the action of the flow dividing island, the airflow entering the pressurizing stage flow channel sections is divided into two airflows by the flow dividing cone after passing through the pressurizing stage, one airflow continuously flows in the inner duct and is introduced into the high-pressure compressor, the other airflow enters the outer duct from an axial gap between the flow dividing island and the flow dividing cone and is mixed with the outer duct airflow divided by the flow dividing island, and the flow rate of the airflow entering the pressurizing stage flow channel sections is more than 10% larger than the flow rate sucked by the high-pressure compressor.

2. The bypass ratio ultra-wide adjustable double-shaft turbofan engine structure based on variable supercharging stages of claim 1, wherein the variable speed ratio reduction gearbox is a planetary gear reduction gearbox and at least comprises a sun gear, an inner gear ring and a plurality of layers of planetary gear sets arranged between the sun gear and the inner gear ring, wherein the sun gear is directly in driving connection with the high-pressure shaft, the inner gear ring is in driving connection with the supercharging stages, and variable speed reduction ratio is realized by meshing different planetary gear sets.

3. The variable boost stage-based bypass ratio ultra-wide adjustable dual-shaft turbofan engine architecture of claim 1 wherein the boost stage comprises a boost stage rotor and a boost stage stator, and an inner bypass stator is disposed upstream of the boost stage.