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

Abstract

The invention discloses a boundary layer inhalation type propeller using two-stage large and small blades. The boundary layer inhalation type propeller is installed at the tail of the aircraft, the propeller is provided with a large rotor and a small rotor, and the blades of the large rotor adopt The lower rotation speed produces the thrust of the main part to meet the climbing performance of the aircraft; the blades of the small rotor use a higher rotation speed, which can increase the root load, so that the propeller blade is close to the ideal load, and the downstream of the propeller is minimized. The energy contained in the air flow.

Description

Boundary layer inhalation thruster with two-stage large and small blades

technical field

The invention relates to the technical field of aeronautical aircraft propellers, in particular to a boundary layer inhalation propeller adopting two-stage large and small blades.

Background technique

Since the "Jet Age", air transportation has experienced explosive growth. The prosperous air transportation has promoted the progress of human society, but it has also brought heavy pressure on resources and the environment. The international community has clearly put forward stricter energy consumption and emission requirements, prompting people to explore energy-saving and emission-reduction technologies. Several studies on Boeing's blended wing-body BWB aircraft, MIT-Cambridge SilentAircraft, and MIT D8 aircraft show that BLI may reduce power consumption by 3 to 20% over existing aircraft technology. Such energy-saving potential could mean a technological revolution for the aviation industry.

Boundary Layer Ingestion BLI is an unconventional aircraft layout that belongs to the airframe/propulsion integration technology: a thruster (propeller or fan) installed at the rear of the airframe sucks in the airflow containing the airframe boundary layer, thereby reducing power consume. The basic principle of BLI energy saving is that the propeller inhales and accelerates the air flow of the boundary layer of the airframe, thereby suppressing the wake (including airframe wake and propeller jet) behind the aircraft, and suppressing the work contained in the wake (kinetic energy dissipation rate) ) is exactly the power saved.

In theory, in order to minimize power consumption, the thruster should try to capture the boundary layer airflow of the fuselage, while minimizing the wake downstream of the thruster (suppressing the energy in the downstream airflow, including the axial direction of the jet and wake). kinetic energy).

In order to achieve this effect, the injected momentum of the boundary layer airflow at the root (bottom) of the blade should be increased along the radial direction of the propeller blade, and the injected momentum into the airflow at the blade tip (external) should be reduced. During the design process, the following problems will occur:

(1) Existing propellers can attenuate the energy in the downstream airflow by adjusting the blade load distribution along the radial direction. However, the rotational linear speed at the root of the blade is much lower than the speed at the tip, which is difficult (at the root) The axial momentum is greatly increased to achieve the ideal energy saving effect.

(2) There are naturally shedding vortices at the root of the propeller blade, such as the horseshoe vortex at the root of the fan blade, the root vortex of the propeller blade, and the existing propeller, by adjusting the blade load distribution, the use of large load (circulation) at the blade root. The design may induce an increase in the blade root vortex strength, causing airflow separation at the blade root, which in turn significantly increases power consumption.

(3) The problem of air intake distortion. Since the inhaled air flow of the propeller contains boundary layer air flow, the uneven incoming flow causes air intake distortion, which poses a safety hazard to the rotating propeller blades.

Due to the above reasons, the inventors have conducted in-depth research on the existing boundary layer inhalation thrusters, expecting to design a new boundary layer inhalation thruster that can solve the above problems.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned problems, the inventors have conducted keen research and designed a boundary layer inhalation propeller using two-stage large and small blades. The boundary layer inhalation propeller is installed at the tail of the aircraft, and the propeller is provided with a Large rotor and small rotor, the blades of the large rotor use a lower rotation speed to generate the thrust of the main part to meet the climbing performance of the aircraft; the blades of the small rotor use a higher rotation speed, which can increase the root load, so that the propeller blades are close to ideal load to complete the present invention.

Specifically, the purpose of the present invention is to provide a boundary layer inhalation propeller using two-stage large and small blades, which is characterized in that:

The thruster is installed at the tail of the aircraft 1,

The propeller includes 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 have opposite directions of rotation and different rotational speeds.

Wherein, when the duct is set on the aircraft 1,

There are at least two ducts,

Preferably, the large rotor 2 is arranged in the large duct 3,

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

The small duct 5 is located inside the large duct 3 , and the small duct 5 and the large duct 3 are connected by the stator blade 4 .

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

Preferably, the ratio of the diameter of the large rotor 2 to the diameter of the aircraft fuselage section is between 4:1 and 1:2.

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

Wherein, when the flying speed of the aircraft is in the range of Mach 0.1 or more and less than Mach 0.85, the ratio of the rotational speed of the large rotor to the rotational speed of the small rotor is between 2:3 and 1:6.

The beneficial effects of the present invention include:

(1) According to the boundary layer suction propeller using two-stage large and small blades provided by the present invention, two-stage rotor blades are used instead of traditional single rotor blades, which provides a basis for realizing ideal blade circulation distribution;

(2) According to the boundary layer inhalation propeller using two-stage large and small blades provided by the present invention, the large rotor blade adopts a lower rotational speed to generate the thrust of the main part to meet the climbing performance of the aircraft; the small rotor blade adopts a higher rotation speed speed, which can increase the root load, thereby bringing the propeller blade closer to the ideal load;

(3) According to the boundary layer inhalation propeller using two-stage large and small blades provided by the present invention, in the place where the root air flow contains more boundary layer air flow, the large rotor and the small rotor work together to increase the axial momentum, thereby reducing the single-machine blade. load, which is conducive to tolerance of intake distortion;

(4) According to the boundary layer suction propeller using two-stage large and small blades provided by the present invention, the small duct and the large duct are connected by a stator blade, and the stator blade can also eliminate the downstream swirl flow of the large rotor, and at the same time The small rotor performs pre-rotation; in addition, the stator blade can also comb the root airflow, reduce the root vortex intensity, and help to suppress the airflow separation at the root of the blade;

(5) According to the boundary layer suction propeller using two-stage large and small blades provided by the present invention, the large rotor and the small rotor are respectively driven by independent motors, and the rotation directions of the large rotor and the small rotor are opposite to eliminate the swirl flow and further reduce the single Rotor load, which is beneficial to tolerate intake distortion.

Description of drawings

1 shows a schematic structural diagram of a boundary layer inhalation propeller using two-stage large and small blades arranged on an aircraft according to a preferred embodiment of the present invention;

2 shows a schematic diagram of the overall structure of a boundary layer suction propeller using two-stage large and small blades according to a preferred embodiment of the present invention, when the large rotor is in the front and the small rotor is behind;

3 shows a schematic diagram of the overall structure of a boundary layer suction propeller using two-stage large and small blades according to a preferred embodiment of the present invention, when the large rotor is in the rear and the small rotor is in the front.

Description of reference numbers:

1 - Aircraft

2 - Big Rotor

3-Big Duct

4-Stator blade

5-Small culvert

6- Small rotor

Detailed ways

The present invention will be further described in detail below through the accompanying drawings and embodiments. The features and advantages of the present invention will become more apparent from these descriptions.

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 various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

According to the present invention, a boundary layer inhalation thruster using two-stage large and small blades is provided, and the thruster is installed at the tail of the aircraft 1, as shown in FIG. 1 ,

The propeller includes a large rotor 2 and a small rotor 6, as shown in Figures 2 and 3; the large rotor 2 and the small rotor 6 are arranged coaxially, and the dashed lines in Figures 2 and 3 represent the large rotor 2 and the small rotor 6. The rotation center of the small rotor 6 is also the central axis of the aircraft, and the figure only shows part of the structure of the tail of the aircraft 1; the large rotor 2 and the small rotor 6 both include a rotating shaft and blades;

The rotations of the large rotor 2 and the small rotor 6 are opposite, and the rotational speed is different. Preferably, the rotational speed of the large rotor is smaller than the rotational speed of the small rotor. Taking 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 Figure 1, the large rotor is placed in front of the small rotor, the large rotor generates most of the thrust, and the small rotor generates more thrust. Small and large rotors make the transmission path of the main force shorter and the structural force more reasonable.

A duct may or may not be installed on the boundary layer suction thruster. The ducted and non-ducted thrusters are suitable for different types of aircraft.

In a preferred embodiment, when the aircraft 1 is provided with ducts, there are at least two ducts, and preferably, each rotor has a corresponding duct;

Preferably, the large rotor 2 is arranged in the large duct 3 , and the small rotor 6 is arranged in the small duct 5 . In this application, the ducted propeller is suitable for installation on a wide range of aircraft, the aircraft is a fixed-wing aircraft, and the range includes a civil airliner as large as 300 tons and a drone as small as 1 kg.

The small duct 5 is located inside the large duct 3, and the small duct 5 and the large duct 3 are connected by the stator blade 4. Specifically, one end of the stator blade 4 is connected with the inner wall of the large duct, and the other end is The outer walls of the small ducts are connected; a plurality of stator blades 4 are arranged in each large duct 3, and specifically, 2 to 50 of the stator blades can be arranged.

In a preferred embodiment, the ratio of the diameter of the large rotor 2 to the diameter of the small rotor 6 is 8:1 to 2:1. The most preferred ratio size is 3:1; the diameter of the small rotor is comparable to the diameter after diffusion of the fuselage boundary layer, so that the small rotor captures the boundary layer airflow; and the diameter of the large rotor is determined by the design disk load.

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

In a preferred embodiment, the distance dimension between the leading edge of the blades of the large rotor 2 and the leading edge of the blades of the small rotor 6 is 0.2-3R, preferably 0.5R, where R is the radius of the large rotor. When the distance between the leading edges of the rotor blades is less than this distance, the width of the stator blades is too narrow, which is not conducive to supporting the ducts in structure; at the same time, the distance is too close, so that the aerodynamic noise between the rotor blades and the stator blades is beyond a reasonable range; Added ineffective structural weight.

When the flying speed of the aircraft is in the range of Mach 0.1 or more and less than Mach 0.85, the ratio of the rotational speed of the large rotor to the rotational speed of the small rotor is 2:3˜1:6. The rotational speed of the large and small rotors is limited by the linear speed of the blade tip. Generally, the linear speed of the blade tip does not exceed Mach 0.8. If it is greater than this value, it will cause compressibility problems, and the shock resistance of the blade will increase sharply. The diameter of the blade disc determines the rotational speed between the two, respectively.

Example:

Install the boundary layer inhalation thruster with two-stage size blades on the aircraft, the aircraft is a C919 aircraft, the aircraft has a wingspan of 35 meters, a maximum take-off gross weight of 73 tons, and a cruising speed of Mach 0.7 to 0.84;

In the boundary layer suction propeller using two-stage large and small blades, the distance between the large rotor and the small rotor is 0.9m,

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

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

The aircraft has an economical fuel consumption rate of 2.7 t/h at 70 t payload and cruising at Mach 0.78.

Comparative ratio:

The C919 aircraft has a wingspan of 35 meters, a maximum take-off gross weight of 73 tons, a cruising speed of 0.7 to 0.84M, and the CFM56 turbofan engine is hoisted under the wing.

The aircraft has an economical fuel consumption rate of 2.9 t/h at a 70-ton payload and cruising at Mach 0.78.

It can be seen from the above comparison that the aircraft using the boundary layer inhalation propeller provided by the present invention using two-stage large and small blades can reduce the economic fuel consumption rate during cruise by about 7%.

The present invention has been described above with reference to the preferred embodiments, but these embodiments are merely exemplary and serve only for illustrative purposes. On this basis, various substitutions and improvements can be made to the present invention, which all fall within the protection scope of the present invention.

Claims (2)

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.

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