CN113443124B

CN113443124B - Boundary layer suction type propeller adopting two-stage large and small blades

Info

Publication number: CN113443124B
Application number: CN202110821383.9A
Authority: CN
Inventors: 吕佩剑; 莫雳; 张福彪; 范世鹏; 黄璐; 林德福
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-07-20
Filing date: 2021-07-20
Publication date: 2022-08-19
Anticipated expiration: 2041-07-20
Also published as: CN113443124A

Abstract

The invention discloses a boundary layer suction type propeller adopting two stages of large and small blades, which is arranged at the tail part of an aircraft, wherein a large rotor and a small rotor are arranged on the propeller, and the blades of the large rotor adopt lower rotating speed to generate thrust of the main part, thereby meeting the climbing performance of the aircraft; the blades of the small rotor adopt higher rotating speed, the root load can be increased, so that the blades of the propeller are close to the ideal load, and the energy contained in the airflow downstream of the propeller is reduced to the maximum extent.

Description

Boundary layer suction type propeller adopting two-stage large and small blades

Technical Field

The invention relates to the technical field of aviation aircraft propellers, in particular to a boundary layer suction type propeller adopting two stages of large and small blades.

Background

Since the "jet era", air transportation has experienced explosive growth, and the thriving air transportation has promoted human social progress, but also has brought a heavy pressure on resources and the environment. The international society clearly puts forward more strict energy consumption and emission requirements, and prompts people to explore energy-saving and emission-reducing technologies. Multiple studies of Boeing wingbody fusion BWB Aircraft, MIT-Cambridge Silent Aircraft, and MIT D8 Aircraft have shown that BLI may reduce power consumption by 3-20% over existing Aircraft technologies. Such energy saving potential may represent a technological revolution for the aviation industry.

Boundary Layer suction propulsion (Boundary Layer induction BLI) is an unconventional aircraft layout, belonging to the airframe/propulsion integration technology: a propeller (propeller or fan) installed at the rear of the body sucks an air flow containing a boundary layer of the body, thereby reducing power consumption. The basic principle of BLI energy conservation is that thrusters suck and accelerate boundary layer airflows of the airframe, thereby suppressing wakes (including airframe wakes and thruster jets) behind the aircraft, and the work (kinetic energy dissipation rate) contained by the suppressed wakes is just the power saved.

In theory to minimize power consumption, the propellers should try to capture the boundary layer flow of the fuselage while minimizing the wake downstream of the propeller (to suppress the energy in the downstream flow, including the axial kinetic energy of the jet and wake).

In order to achieve such an effect, the injection momentum of the boundary layer airflow at the root (bottom) of the blade should be increased and the injection momentum of the boundary layer airflow at the tip (outside) of the blade should be decreased along the radial direction of the blade of the propeller, but such a requirement causes the following problems in the propeller design process:

first, the conventional propeller can reduce the energy in the downstream airflow by adjusting the blade load distribution along the radial direction, however, the rotational linear speed of the blade root is far lower than the tip speed, so that it is difficult to greatly increase the axial momentum (at the root) to achieve the ideal energy-saving effect.

The existing propeller adopts a large load (ring amount) design at the blade root to possibly induce the strength increase of the blade root vortex by adjusting the load distribution of the blade, so that the airflow separation of the blade root is initiated, and further the power consumption is obviously increased.

And thirdly, the problem of intake distortion is that the intake distortion is caused by uneven incoming flow because the airflow sucked by the propeller contains boundary layer airflow, and the intake distortion forms a potential safety hazard to the rotating propeller blades.

For the above reasons, the present inventors have made intensive studies on the existing boundary layer suction type propeller in order to design a new boundary layer suction type propeller capable of solving the above problems.

Disclosure of Invention

In order to overcome the problems, the inventor of the invention carries out intensive research and designs a boundary layer suction type propeller adopting two stages of large and small blades, the boundary layer suction type propeller is arranged at the tail part of an aircraft, a large rotor and a small rotor are arranged on the propeller, and the blades of the large rotor adopt lower rotating speed to generate thrust of the main part so as to meet the climbing performance of the aircraft; the blades of the small rotors adopt higher rotating speed, and the root load can be increased, so that the propeller blades are close to the ideal load, thereby completing the invention.

Specifically, the invention aims to provide a boundary layer suction type propeller adopting two stages of large and small blades, which is characterized in that,

the propeller is mounted at the tail of the aircraft 1,

the propeller comprises a large rotor 2 and a small rotor 6;

the large rotor 2 and the small rotor 6 are coaxially arranged,

the large rotor 2 and the small rotor 6 rotate in opposite directions and rotate at different speeds.

Wherein, when a duct is provided on the aircraft 1,

at least two ducts are arranged in the main body,

preferably, said greater rotor 2 is arranged in a greater duct 3,

the small rotor 6 is arranged in a small duct 5.

Wherein, little duct 5 is located big duct 3 inside, and connects through stator blade 4 between little duct 5 and the big duct 3.

Wherein the ratio of the diameter size of the large rotor 2 to the diameter size of the small rotor 6 is 8:1 to 2: 1;

preferably, the ratio of the diameter dimension of the large rotor 2 to the aircraft fuselage cross-sectional diameter is between 4:1 and 1: 2.

The distance between the front edge of the blade of the large rotor 2 and the front edge of the blade of the small rotor 6 is 0.2-3R, and R is the radius of the large rotor.

When the flying speed of the aircraft is more than 0.1 Mach and less than 0.85 Mach, the ratio of the rotating speed of the large rotor to the rotating speed of the small rotor is between 2:3 and 1: 6.

The invention has the advantages that:

(1) according to the boundary layer suction type propeller adopting the two-stage large and small blades, provided by the invention, the two-stage rotor blades are adopted instead of the traditional single-rotor blades, so that a foundation is provided for realizing ideal blade circulation distribution;

(2) according to the boundary layer suction type propeller adopting the two stages of large and small blades, the large rotor blades adopt lower rotating speed to generate the thrust of the main part, so that the climbing performance of an aircraft is met; the small rotor blades adopt higher rotating speed, and the root load can be increased, so that the blades of the propeller are close to ideal load;

(3) according to the boundary layer suction type propeller adopting the two stages of large and small blades, the large rotor and the small rotor act together to increase the axial momentum at the place where the root airflow contains more boundary layer airflows, so that the load of a single-machine blade is reduced, and the tolerance of intake distortion is facilitated;

(4) according to the boundary layer suction type propeller adopting the two stages of the large blades and the small blades, the small duct is connected with the large duct through the stator blade, the stator blade can eliminate the downstream rotational flow of the large rotor and pre-rotate the small rotor; in addition, the stator blade can also comb blade root airflow, reduce the strength of root vortex flow and is beneficial to inhibiting the airflow separation at the root part of the blade;

(5) according to the boundary layer suction type propeller adopting the two stages of large and small blades, the large rotor and the small rotor are respectively driven by the independent motors, the rotating directions of the large rotor and the small rotor are opposite to eliminate rotational flow, the load of a single rotor is further reduced, and the tolerance of intake distortion is facilitated.

Drawings

FIG. 1 is a schematic diagram of a boundary layer suction propeller with two stages of large and small blades on an aircraft according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram showing the overall structure of a boundary layer suction type propeller with two stages of large and small blades, wherein a large rotor is arranged in front of a small rotor and the small rotor is arranged behind the large rotor;

fig. 3 is a schematic view showing the overall structure of a large rotor when a rear small rotor is in front in a boundary layer suction type propeller using two stages of large and small blades according to a preferred embodiment of the present invention.

The reference numbers indicate:

1-aircraft

2-big rotor

3-big duct

4-stator blade

5-Small duct

6-small rotor

Detailed Description

The invention is explained in more detail below with reference to the figures and examples. The features and advantages of the present invention will become more apparent from the description.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

According to the invention, a boundary layer suction propeller with two stages of large and small blades is provided, which is mounted at the tail of an aircraft 1, as shown in figure 1,

the propeller comprises a large rotor 2 and a small rotor 6, as shown in fig. 2 and 3; the large rotor 2 and the small rotor 6 are coaxially arranged, the dotted lines in fig. 2 and 3 represent the rotation centers of the large rotor 2 and the small rotor 6, which are also the central axis of the aircraft, and only part of the structure of the tail part of the aircraft 1 is shown in the figure; the large rotor 2 and the small rotor 6 both comprise a rotating shaft and blades;

the large rotor 2 and the small rotor 6 are opposite in rotation direction and different in rotation speed, and preferably, the rotation speed of the large rotor is smaller than that of the small rotor. With the traveling direction of the aircraft as the front, the large rotor can be placed in front of or behind the small rotor, preferably as shown in fig. 1, the large rotor is placed in front of the small rotor, the large rotor generates most of thrust, the small rotor generates less thrust, the large rotor makes the force transmission path of the main acting force shorter in the front, and the structural stress is more reasonable.

The boundary layer suction type propeller can be provided with a duct or not, and the propeller provided with the duct and the duct which is not provided is suitable for different types of aircrafts.

In a preferred embodiment, when a duct is provided on the aircraft 1, there are at least two ducts, preferably one for each rotor;

preferably, the large rotor 2 is arranged in a large duct 3 and the small rotor 6 is arranged in a small duct 5. In this application, the propeller that is provided with the duct is applicable to more extensively on the aircraft of installation, and this aircraft is the fixed wing aircraft, and the scope contains big to 300 tons civil aviation passenger planes, little unmanned aerial vehicle to in 1 kilogram.

The small duct 5 is positioned inside the large duct 3, and the small duct 5 is connected with the large duct 3 through the stator blades 4, specifically, one end of each stator blade 4 is connected with the inner wall surface of the large duct, and the other end of each stator blade 4 is connected with the outer wall surface of the small duct; a plurality of stator blades 4, specifically, 2 to 50 stator blades, are provided in each large duct 3.

In a preferred embodiment, the ratio of the diameter size of the large rotor 2 to the diameter size of the small rotor 6 is 8:1 to 2: 1. the most preferred scale size is 3: 1; the diameter of the small rotor is equivalent to the diameter of the diffused boundary layer of the machine body, so that the small rotor can capture the boundary layer airflow; while the large rotor diameter is determined by the design disc load.

Preferably, the ratio of the diameter dimension of the large rotor 2 to the aircraft fuselage section diameter is between 4:1 and 1: 2; when the aircraft is a fuselage with a non-circular section, the diameter of the section of the fuselage is the diameter of the maximum characteristic circle;

in a preferred embodiment, the distance between the blade leading edge of the large rotor 2 and the blade leading edge of the small rotor 6 is 0.2-3R, preferably 0.5R, and R is the radius of the large rotor. When the distance between the front edges of the rotor blades is smaller than the distance, the width of the stator blades is too narrow, and the structure is not beneficial to supporting the duct; meanwhile, the distance is too close, so that the pneumatically generated noise between the rotor blade and the stator blade exceeds a reasonable range; distances greater than this increase the ineffective structural weight.

When the flying speed of the aircraft is more than 0.1 Mach and less than 0.85 Mach, the ratio of the rotating speed of the large rotor to the rotating speed of the small rotor is 2: 3-1: 6. The rotating speeds of the large rotor and the small rotor are limited by the linear speed of the blade tips, the linear speed of the blade tips does not exceed 0.8 Mach generally, and if the linear speed of the blade tips is larger than the linear speed of the blade tips, the compressibility problem is caused, and the shock wave resistance of the blades is increased violently; under the limitation of the linear speed of the blade tip, the rotating speed between the large blade disc and the small blade disc is respectively determined by the diameters of the large blade disc and the small blade disc.

The embodiment is as follows:

installing a boundary layer suction type propeller with two stages of large and small blades on an aircraft, wherein the aircraft is a C919 airplane, the aircraft has a wingspan of 35 meters, the maximum total takeoff weight is 73 tons, and the cruising speed is 0.7-0.84 Mach;

in the boundary layer suction type propeller adopting two stages of large and small blades, the distance between a large rotor and a small rotor is 0.9m,

the diameter of the large rotor is 1.8m, and the diameter of the small rotor is 0.6 m;

the design rotating speed of the large rotor is 5000RPM, and the design rotating speed of the small rotor is 8000 RPM;

the economic fuel consumption of the aircraft at 70 ton capacity and cruising at mach 0.78 was 2.7 ton/hour.

Comparative example:

the C919 airplane has an airplane wing span of 35 meters, a maximum total takeoff weight of 73 tons, a cruising speed of 0.7-0.84M, a CFM56 turbofan engine hung below wings,

the economic fuel consumption of the aircraft at 70 ton capacity and at 0.78 mach cruise was 2.9 ton/hour.

Through the comparison, the aircraft adopting the boundary layer suction type propeller with two stages of large and small blades provided by the invention can reduce the economical fuel consumption rate by about 7% during cruising.

The present invention has been described above in connection with preferred embodiments, but these embodiments are merely exemplary and merely illustrative. On the basis of the above, the invention can be subjected to various substitutions and modifications, and the substitutions and the modifications are all within the protection scope of the invention.

Claims

1. A boundary layer suction type propeller adopting two stages of large and small blades is characterized in that,

the propeller is arranged at the tail part of the aircraft (1),

the propeller comprises a large rotor (2) and a small rotor (6);

the large rotor (2) and the small rotor (6) are coaxially arranged, and the rotation centers of the large rotor (2) and the small rotor (6) are the central axes of the aircraft; the large rotor (2) and the small rotor (6) both comprise rotating shafts and blades;

the large rotor (2) and the small rotor (6) have opposite rotation directions and different rotating speeds;

the aircraft (1) is provided with a duct,

at least two ducts are arranged;

the small duct (5) is positioned inside the large duct (3), and the small duct (5) is connected with the large duct (3) through the stator blades (4);

the ratio of the diameter size of the large rotor (2) to the diameter size of the small rotor (6) is 8:1 to 2: 1; the diameter of the small rotor (6) is equivalent to the diameter of the diffused boundary layer of the machine body, so that the small rotor (6) captures the boundary layer airflow;

the distance between the front edge of the blade of the large rotor (2) and the front edge of the blade of the small rotor (6) is 0.2-3R, and R is the radius of the large rotor (2);

when the flight speed of the aircraft is in the range of more than 0.1 Mach and less than 0.85 Mach, the ratio of the rotating speed of the large rotor (2) to the rotating speed of the small rotor (6) is between 2:3 and 1: 6;

the big rotor (2) is arranged in the big duct (3),

the small rotor (6) is arranged in the small duct (5).

2. The boundary layer suction type impeller with two-stage large and small blades according to claim 1,

the ratio of the diameter size of the large rotor (2) to the diameter of the cross section of the aircraft fuselage is between 4:1 and 1: 2.