WO2017146028A1

WO2017146028A1 - Rotor blade, drone, and helicopter

Info

Publication number: WO2017146028A1
Application number: PCT/JP2017/006310
Authority: WO
Inventors: 原田　正志
Original assignee: 国立研究開発法人宇宙航空研究開発機構
Priority date: 2016-02-23
Filing date: 2017-02-21
Publication date: 2017-08-31
Also published as: JP6778440B2; JPWO2017146028A1; WO2017145563A1

Abstract

[Problem] To be able to provide a high figure of merit and increase flight time and payload weight when used, for example, in a drone or a helicopter. [Solution] A rotor blade 1 has a solidity of 10% or less. The shape of the rotor blade 1 is as follows: (1) the rotor blade has a maximum chord length near the base, and the value thereof is at least twice the minimum value of the chord length within a range from 50% to 90% in radius; (2) the tip end gradually narrows; and (3) the angle of incidence of the base decreases toward the base within a region from around 30% or less in radius.

Description

Rotor blades, drones and helicopters

The present invention relates to a rotor blade used in a drone, a helicopter, etc., and a drone and a helicopter having such a rotor blade.

In recent years, a drone called a drone with four or more rotor blades is actively used for photographing and observation purposes. The drone usually uses a plastic two-bladed fixed-pitch rotor, and the weight of the payload and the flight time are affected by the performance of this rotor blade. The rotor blade shape varies, and the chord length of the root is wide, which seems to have applied the classical propeller theory (Non-patent Document 1) from simple taper, and the chord length is sharply reduced from there to the tip. There is a transition to a smaller taper ratio, with rounded tips.

Also, a fixed pitch blade is used as in GEN H-4 (Non-patent Document 2) developed by GEN CORPORATION as a manned small helicopter, and a simple taper is adopted for the rotor blade. In the field of helicopter, Westland Linx in the UK has achieved a world speed record using a rotor blade with an enlarged tip chord length called BERP (Non-patent Document 3, Patent Document 1) and a receding angle. Yes. This rotor blade functions as a dog tooth used in an airplane with a discontinuous leading edge with an enlarged chord at the tip, generating a vertical vortex and suppressing peeling of the upper surface, earning a lift coefficient on the reverse side, The purpose is to reduce the wave resistance on the forward side by the receding angle of the tip.

The helicopter has to trade off the maximum speed with the figure of merit (non-patent document 4) obtained by dividing the actual lift by the theoretical maximum lift calculated from the simple motion theory, rotor rotation area and input power. A rectangular shape or a shape with a weak taper at the tip is often used. On the other hand, since the drone takes a long time to hover, there is a high demand to increase the flight time and the payload by using a rotor blade having a high figure of merit.

US Pat. No. 5,174,721

There is a method by Adkins et al. (Non-Patent Document 1) as an effective method for designing a rotor blade having a large figure of merit. However, the method of Adkins et al. Could not reflect the contraction (reduction in the radius of the cylindrical flow) or the vortex (roll-up) observed in the actual wake of the rotor blade. Therefore, the figure of merit was not the maximum.

In view of the circumstances as described above, an object of the present invention is to provide a rotor blade capable of increasing the figure of merit, a drone having such a rotor blade, and a helicopter.

In order to solve the above problems, a rotor blade according to the present invention is a rotor blade having a solidity of 10% or less, has a maximum chord length near the root, and the value of the maximum chord length is from a radius of 50%. It is more than twice the minimum value of the chord length at 90%, the tip is gradually narrowed, and the attachment angle of the root decreases as it goes to the root in a region with a radius of about 30% or less.
The rotor blade according to the present invention has a shape reflecting the contracted flow (reduction in the radius of the cylindrical flow) and the swirl (roll-up) found in the wake of the actual rotor blade, so that the figure of merit is increased. I can do things.
The rotor blade according to the present invention has a maximum chord length near the root, and the value of the maximum chord length is more than twice the minimum value of the chord length at a radius of 50% to 90%, The attachment angle of the base decreases in the region where the radius is about 30% or less as it goes to the base. This is a shape obtained by optimizing using the accurate rotor wake while keeping the chord length at a feasible value, and the figure of merit can be increased.

The drone which concerns on another form of this invention has the rotor blade of the said structure.
A helicopter according to still another embodiment of the present invention has the rotor blade having the above-described configuration.

The figure of merit is high according to the present invention, and if used for drones, helicopters, etc., flight time and payload weight can be increased.

It is a top view of the rotor blade which concerns on one Embodiment of this invention. The trajectory of the blade tip vortex of the rotor blade is shown. a) is a trajectory of the blade tip vortex of the rotor blade by the method of Adkins et al., and b) is a trajectory of the blade tip vortex of the rotor blade by the Harada vortex method of the present inventor. It is a graph which shows the roll-up of the discharge | released vortex modeled. It is a graph which shows the optimal chord length distribution of a conventional method. It is a graph which shows the optimal attachment angle of the conventional method. It is a graph which shows the characteristic of the chord length distribution of this invention. It is a graph which shows the characteristic of the attachment angle of this invention. It is a graph which shows the characteristic of the chord length distribution of this invention more preferable. It is a graph which shows the characteristic of the mounting angle of this invention more preferable. It is a figure for demonstrating Harada's vortex method, and has shown the coordinate system and discharge | emission vortex of a propeller. It is a figure for demonstrating Harada's vortex method, and has shown the enlarged view of the 1st blade in FIG. It is a figure for demonstrating Harada's vortex method, and has shown the cross section and inflow velocity of a blade. It is a figure for demonstrating Harada's vortex method, and has shown the force which acts on a blade blade element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a top view of a rotor blade according to an embodiment of the present invention.
As shown in FIG. 1, the rotor blade 1 is provided on a hub 2 having a shaft hole 3.

Here, the method of Adkins et al. Can handle only a wake having a constant pitch and a constant radius, as shown in FIG. On the other hand, in the Harada vortex method (which will be described later), which is the present inventor, the vortex radius contracts as in the experiment as shown in FIG. By applying a discharge vortex model in which the vortex to be concentrated is concentrated at the blade tip and the center of rotation by rolling up behind, a rotor blade 1 having the following form is obtained, and by using such a rotor blade 1 A high figure of merit is obtained.
The rotor blade 1 has a solidity of 10% or less.
The shape of the rotor blade 1 is as follows.
(1) It has a maximum chord length near the root and its value is at least twice the minimum chord length at a radius of 50% to 90%.
(2) The tip is gradually becoming thinner.
(3) The attachment angle of the base should be reduced toward the base in an area with a radius of about 30% or less.
FIG. 4 shows the chord length distribution when the Harada vortex method of the present inventor is optimized using the vortex model of FIG. 2 a), and FIG. 5 shows the mounting angle. Here, the calculation conditions are shown in Table 1.

As shown in FIG. 4, the chord length of the root has reached 7.5 cm, which is not practical. Some commercially available drones cut the chord length at the base of this rotor blade to about 4 cm.
FIG. 6 shows the chord length distribution when the Harada vortex method of the present inventor is optimized using the vortex model of FIG. 2 b), and FIG. 7 shows the mounting angle. The figure of merit at this time is 78.8%.

The tangent line AB at the tip of the obtained chord length has a negative slope, the tangent line CD at a radius of 65% has a positive slope, takes a local minimum value F at a point E near a radius of 60%, and is near the root. The maximum value H is taken at point G.

This H value is more than twice F. Also, the obtained tangent IJ near the tip of the mounting angle has a positive value, takes a minimum value N at a point M near a radius of 60%, takes a maximum value P at a point O near a radius of 30%, and near the base. The tangent line KL has a negative value. Even with this shape, the chord length is 7 cm near the base of the wing.

Since Harada's vortex method, which is the present inventor, obtains a solution by minimizing the evaluation function, for example, a penalty function that increases when the chord length exceeds 4 cm is added to the evaluation function to limit the chord length. Can be imposed. The chord length at this time is shown in FIG. 8, and the mounting angle is shown in FIG. The figure of merit at this time is 78.6%.

Similar to the previous result, the tangent line AB at the tip of the obtained chord length has a negative gradient, the tangent line CD at a radius of 65% has a positive gradient, and a local minimum at a point E near a radius of 60%. Take F and take the maximum value H at point G near the root.

This H value is more than twice F. Also, the obtained tangent IJ near the tip of the mounting angle has a positive value, takes a minimum value N at a point M near a radius of 60%, takes a maximum value P at a point O near a radius of 30%, and near the base. The tangent line KL has a negative value.

Here, when calculated using the specifications of a typical drone rotor, from the viewpoint of practicality, when the chord length is limited to twice the minimum value, the figure of merit is reduced by 0.3%. When the chord length was limited to 1.5 times the minimum value, the figure of merit was reduced by 1.0%. On the other hand, in the rotor blade 1 according to the present invention, the mounting angle is optimally set so as to maximize the figure of merit while limiting the chord length in this way, that is, attaching the root By reducing the angle toward the root in a region with a radius of about 30% or less, the figure of merit reduction due to chord limitation can be minimized in this section.
Therefore, the rotor blade 1 according to this embodiment has a high figure of merit, and if used in a drone, helicopter, etc., the flight time and payload weight can be increased.
The present invention can be applied to a fixed pitch coaxial double reversing rotor type manned helicopter, a fixed pitch coaxial double reversing rotor type unmanned helicopter, and the like.

Next, the Harada vortex method described above will be described.
FIG. 10 shows the propeller coordinate system and the discharge vortex. It is considered that the propeller moves in the x-axis direction while rotating, and a discharge vortex is left in the moved locus.
FIG. 11 shows an enlarged view of the first blade. There are i-th representative point from the axis of rotation on r _i apart blades, j-th emission vortices are discretized into short line segments as shown in Fig white circles. Assuming that the induced velocity in the x direction caused by the discharge vortex of the j-th unit intensity at the i-th representative point is X _ij and the induced velocity in the z-direction is Z _ij , the induced velocity u in the x-direction caused by the i-th representative point u. _{The i} and z-direction guiding speeds w _i are respectively u _i = ΣX _ij г _j (1)
w _i = ΣZ _ij г _j (2)
Given in. Here, X _ij and Z _ij are constants obtained from Biosavart's law, and г _j is the j-th emission vortex.

FIG. 12 shows the cross section of the blade and the inflow speed. When the tangential component of the air flowing into the blades and _{U T} _{U T} is _{_{_{U T = r i Ω-w}}} i (3)
Given in. Here, Ω is the rotational angular velocity of the propeller. Further, when the axial component of the air flowing into the blades and _{U P} _{U P} is _{_{U P = U-u i (}} 4)
Given in. Here, U is the propeller forward speed. The inflow angle φ _i and the inflow speed V _i are given by the following equations, respectively.
_{^{_{_{φ i = tan -1 (U P}}}} / U T) (5)
_{_{^{_{V i = √ (U P 2}}}} + U T 2) (6)

FIG. 13 shows the force acting on the blade blade element. The local lift dL _i acting on the i th blade element is given by the Kutta-Jukovsky theorem as follows: dL _i = ρV _i г _i db (7)
Given in. Here, ρ is the air density, and db is the width of the blade element. Or, using the lift coefficient C _L , dL _i = 1/2 · ρV _i ² C _L c _i db (8)
It is represented by Here, c _i is the chord length of the i th blade element. (7), _{c i} from equation (8) is given by the following equation.
_{_{_{c i = 2г i / C L}}} V i (9)
The local resistance dD _i acting on the i th blade element is given by the following equation using the resistance coefficient C _D.
_{dD i = 1/2 · ρV} i 2 C D c i db (10)
C _D but is a function of the Reynolds number and C _L, using a constant C _L, C _D is good as a constant as a insensitive to Reynolds number.
The axial component of the resultant force of the local lift dL _i and the local resistance dD _i is the local thrust dT _i , and the tangential component is dN _i .
_{_{_{dT i = dL i cosφ i -dD}}} i sinφ i (11)
dN _i = dL _i sin φ _i + dD _i cos φ _i (12)
It becomes. Since the local absorption power dP _i is dN _i r _i Ω, it is given by the following equation.
dP _i = (dL _i sin φ _i + dD _i cos φ _i ) r _i Ω (13)
Eventually, the thrust and absorption power are calculated from the equations (11) and (13) respectively. T = BΣdT _i (14)
P = BΣdP _i (15)
Given in. Here, B is the number of blades.

The optimal design problem for the propeller is C _L , C _D , Ω, design power P ₀ , and гi as an unknown,
[Condition]: P = P ₀
[Objective function]: -T
This results in an optimization problem that minimizes.

1 Rotor blade 2 Hub 3 Shaft hole

Claims

A rotor blade with a solidity of 10% or less,
The shape of the rotor blade is
It has a maximum chord length near the root, and the value of the maximum chord length is more than twice the minimum value of the chord length at a radius of 50% to 90%,
The tip is gradually getting thinner
The attachment angle of the root decreases in the area below a radius of 30% or less as it goes to the root.
A drone having the rotor blade according to claim 1.
A helicopter having the rotor blade according to claim 1.