JPS61105266A - Dynamic pressure type hovercraft - Google Patents

Abstract

PURPOSE:To obtain a vehicle compact and light, and can hover and run over an uneven ground, by installing propellers on the lower part of the airframe, having an airfoil, the blade width ratio of which is larger than 0.1, and by producing dynamic pressure without restraining the airflow produced by the rotation of propellers. CONSTITUTION:The dynamic pressure type hovercraft 100 consists of a bumper 1 which forms an outer frame and prevents propellers 5 from touching obstacles, a frame 2 which corresponds to an airframe, a power source 3 mounted on the frame 2, rotation units 4 installed under the frame 2, propellers 5 having a large blade width ratio (chord length/diameter) airfoil, and so on. Also, a deflector 6 is provided, which controls position and direction of the vehicle depending on the airflow due to the propellers 5, on the frame 2 through a rotating shaft 7. And the blade width ratio of airfoil for the propellers 5 is set up between 0.1 and 0.5. Thus, the anticipated purpose can be achieved by use of the airflow due to the propeller 5 and the changes of aerodynamic characteristics due to the ground.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention relates to a hovercraft that can be used as a practical hovercraft or a play toy.

It is often difficult to move and transport objects on cleared roads during search and rescue operations at distress sites during disasters, and for forestry operations in forest areas. It is also often performed on soft ground, wetlands, or on water. In such an environment, normal vehicles cannot drive, so it is necessary to move and work through the air. Many of these tasks do not require flying high into the air, just slightly above the ground.

Furthermore, smaller vehicles are often more suitable for such environments. For example, when working in a forest area using a helicopter, it is difficult to descend from the air to the ground due to the obstruction of tree branches and leaves. It is also possible to fly through the forest while avoiding trees,
This is difficult because the rotor diameter is large. Therefore, the dimensions of the aircraft body including the rotor (or propeller) must be small.

[Conventional technology] Helicopters are often used for the above purposes.
Another possible vehicle is a hovercraft. Therefore, the problems with hovercraft and helicopter pigs will be clarified, and the effects of the present invention will be clarified.

A conventional hovercraft supports its own weight by maintaining an air cushion (static pressure) with a pressure higher than atmospheric pressure between the aircraft body and the ground surface, and belongs to a static pressure type hovercraft, using the term related to the present invention. In principle, it is difficult to float at a high altitude because in order to maintain a high pressure, the amount of air flowing out from the pressure chamber must be small.

However, the propulsion efficiency (support load per power) is better than other aircraft, and when the propulsion efficiency is constant, the flying height is proportional to the size of the aircraft. Current large hovercraft have a maximum flying height of about 1 m, and since the ground is uneven in the above application, it is even more difficult for small hydrostatic hovercraft to float. In other words, it is practically unusable on rough terrain.

Next, although a helicopter is a vehicle suitable for the above-mentioned purpose, its large rotor diameter poses an obstacle. Furthermore, when a helicopter is flown close to the ground, it is extremely difficult to control the helicopter due to the complex aerodynamic effects caused by the terrain. These characteristics of helicopters are due to the fact that they are not intended to fly close to the ground. That is, if the air density is ρ, the thrust is ρ, and the rotor radius is R, then the propulsion efficiency η when hovering at an altitude where there is no influence from the ground is η=RffdTm7t according to momentum theory. Therefore, when a predetermined thrust is obtained, the propulsion efficiency improves as R increases. Therefore, it is better to rotate a large rotor slowly, for example, with a payload of 9.5K.
(Even in J's unmanned helicopter, the rotor diameter is 1.6 m.
The rotor diameter of a 10-seater helicopter can reach 9 m. In addition, since the rotor's rotational speed is slow, in the case of a piston engine, the rotational speed is reduced to one-tenth to one-twentieth. Therefore, a two-stage or more reduction mechanism is required, and the weight G is 50 kg even for a small machine. I can't ignore it.

[Problems to be Solved by the Invention] As described above, it is difficult for conventional hydrostatic hovercraft and helicopters to operate in narrow places on uneven ground.

This invention was made in view of the above-mentioned circumstances, and aims to create a vehicle that is small and lightweight, can fly at a relatively high altitude near the ground, and can adapt to complex terrain even though it is difficult to fly high in the air. is necessary, and the present invention meets this need.

(b) Structure of the invention [Means for solving the problem] The present invention is similar to a helicopter in that thrust is obtained by rotating the propeller around a substantially vertical axis, but the change in aerodynamic characteristics due to the ground (hereinafter referred to as ground effect) The aim is to achieve terrain adaptability by reducing the size and weight of the propeller, making it possible to mount multiple propellers, in view of the relationship between engine characteristics and engine characteristics.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIGS. 1 and 2, 100 is a hydrodynamic hovercraft. Reference numeral 1 denotes a bumper, which has an annular shape and constitutes a luxurious outer shell of the hydrodynamic hovercraft 100.
prevent it from coming into contact with obstacles. 2 is a frame, which corresponds to the aircraft body. 3 is a power source such as a battery mounted on the frame 2, and is fixed to the frame 2. 4 is a rotating device attached below the frame 2; 5 is a propeller having blade elements with a large blade width ratio (chord length/diameter); four pieces are installed in order to obtain terrain adaptability. Reference numeral 6 denotes a deflection plate for adjusting the position and direction by receiving the air flow of the propeller, and is attached to the frame 2. 7 is the rotation axis of the deflection plate. 8 is an arrow indicating the rotation direction of the propeller, and 9 is the ground. The aircraft has a structure that does not obstruct the airflow of the propeller.

10 is a power device that drives the rotating device 4.

However, although the power source 3 is located at the center of the fuselage in the figure, it may not be located at the center of the fuselage as long as the center of gravity of the aircraft coincides with the center of thrust generated by the propeller. For example, if the power source 3 is a fuel tank of an engine, it may be around the fuselage.

Further, the direction of rotation of the propeller 5 does not necessarily have to be the direction shown in the figure, as long as the moment balance around the vertical axis can be balanced by the control mechanism. Further, although the case where there are four propellers 5 is shown, any number may be used.

Further, the position of the power device 10 (engine, motor, etc.) may be at the position of the rotating device 4, or may be at the center of the aircraft body. When the power plant 10 is placed in the position of the rotating device 4, the rotating device 4 can also be considered as a speed reduction mechanism, and when the propeller 5 is directly connected to the power device 10, the power device 10 also functions as a rotating device. . When one power unit 10 is placed at the center of the aircraft body, the rotating device 4 is driven via a belt or the like.

Further, the deflection plate 6 may be installed at a position where the flow velocity of the air flow of the propeller 5 is large, and does not necessarily need to be installed at the position shown in the figure. For example, it may be directly below the propeller 5. However, in this case, the flying height must be greater than the height of the deflection plate 7. In short, the deflection plate 7 serves to generate a horizontal force by inserting it into the air stream. Also, a plurality of deflection plates may be used. However, an attitude control mechanism other than the deflection plate may be used to generate horizontal force on the aircraft body. Such an attitude control mechanism was developed in 1982.
The technique described in Japanese Patent Application No. 175671 may be used.

The basics of the present invention, as mentioned in the previous section, are: - A propeller attached below the carrier. - A propeller with a large blade width ratio.
The goal is to use a structure that does not impede the propeller's airflow.

[Effect] The effects of the present invention will be explained in detail below.

When one propeller rotates near the ground, the lift-drag ratio (
It is known that the lift/drag force increases. That is, the airflow tube expands rapidly as it approaches the ground, as shown in FIG. In FIG. 3, 11 is a streamline, and 12 is a rotating surface of the propeller 5.

Under the condition that the flow rate is constant, if the cross-sectional area of the flow tube increases, the vertical component of the flow velocity decreases. That is, the flow velocity induced by the rotation of the propeller 5 is smaller than when there is no ground.

Figure 4 shows the effect of induced velocity on the lift and drag of the wing elements. However, frictional resistance due to air viscosity is not shown. For the (2) cord of r from the center of rotation,
There is a component of the horizontal flow velocity rω due to the rotation of the propeller. However, ω is the rotational angular velocity. Furthermore, since there is a component of the induced velocity U, the effective pitch angle for the blade element is the pitch angle α minus the angle β formed by U and rω. It is known that as the effective pitch angle (α-β) increases within a range that does not stall, both the Yang h1 drag force increases. In addition, when there is an induced speed U, the lift force is inclined with respect to the rotational axis Z as shown by the arrow shown by the ladder, its horizontal component becomes the induced resistance, and the Z component becomes the thrust force T. Therefore U
If is small, the induced resistance will decrease and the thrust will increase.

Therefore, overall, if the induced speed U is small, both thrust and drag increase due to an increase in the pitch angle (α-β), but the increase in drag is small by the amount of decrease in induced resistance. In summary, as the propeller approaches the ground, its effectiveness increases, but so does its lift-drag ratio.

The reason why a rotor with a large diameter is used in a helicopter is that, according to blade theory, the induced speed is generated by the blade tip vortex, so the larger the propeller diameter, the smaller the induced speed. Therefore, near the ground (the induced speed becomes small due to the veW of the ground, so even if the propeller diameter is reduced, the lift-drag ratio will not decrease.In reality, the induced speed will not become O, so the propeller diameter will become large) Although the lift-to-drag ratio is still large, the decrease in the lift-to-drag ratio by reducing the propeller diameter is smaller than when there is no ground.The area of the blade element at radius r is 81 speed. When v (-rω), the thrust and drag forces generated by the blade element are expressed by the following equations.

T-(1/2), QV”C7S D= (1/2>, Ov”C□ S However, C7 and C□ are the thrust and drag coefficients, which are determined by the blade shape and pitch angle. Rotation of the blade element The power P required for is determined by the following formula.

P=vD At this time, the propulsion efficiency η is 77=T/P=(C/button)(1/v)=(CT/
C[) ) (1/r ω). According to the above discussion, if there is no change in 0 and Cp depending on the propeller diameter due to the influence of the ground, the propulsion efficiency η is a function only of V. Therefore, for the propeller shown by the solid line in Figure 5, the radius is reduced by a times, the chord length is increased by 1/a times, and the rotational speed is increased by 1/a.
If the speed is doubled, the propulsion efficiency remains constant.

From the above, a propeller with a large blade width ratio can be used near the ground. Additionally, the propeller should be mounted below the fuselage so as to be close to the ground to create a ground effect, and the fuselage structure should be such that it does not hinder the spread of airflow.

As shown in FIG. 6, the engine characteristics are such that the output reaches its maximum at a certain rotation speed. The rotation speed at maximum output is 200ORPM~2
It is quite fast at 0000 PPM. Therefore, by rotating a propeller with a small diameter at high speed, there is no need for large decelerations like in a helicopter, and when using an engine with a relatively small maximum output speed, the propeller can be directly connected to the engine. It becomes possible.

It was idealized that the propulsion efficiency would be constant even with a propeller whose diameter is small due to the ground effect, but in reality it is necessary to maintain a floating height above a certain level, and the induced speed will not become O and the propulsion efficiency will decrease as the diameter becomes smaller. , so the reduction in diameter should be kept within an acceptable range in the design. Furthermore, since the chord length is limited by the propeller diameter, there is also a limit to the reduction of the propeller diameter.

In reality, it is desirable that the blade width ratio of the blade elements of the propeller is 0.1 to 0.5.

In addition, by taking advantage of the fact that the guidance and air flow speed increase due to a reduction in the propeller diameter, it is possible to insert a deflection plate to generate a force perpendicular to the plate and use that force to finely adjust the position and direction. . On the other hand, when the propeller diameter is large, the force acting on the deflection plate is so weak that it does not serve to adjust the position or direction.

The hydrodynamic hovercraft of this invention allows multiple propellers to be installed, making it possible to provide ground adaptability to complex terrain by attaching multiple propellers, and to respond to changes in ground effects due to terrain. Controlling the thrust of each propeller individually would further improve ground adaptability.

[Example 1] A model (body diameter: 3Qcm) having a structure similar to that shown in FIGS. 1 and 2 was produced. Number of propellers 4 Propeller blade width ratio 0.5, whole aircraft type 1i20KfJ
c')'fR1,cN: -Cd 74'rlJi (
60 (1) It was floated using a motor (20g each) in the power unit. The propeller is directly connected to the motor. Also, it naturally floats when a model engine is used.

(C) Effects of the Invention In this way, the hydrodynamic hovercraft of this invention utilizes the air flow from the propeller, uses a propeller with a large blade width ratio, and further utilizes the ground effect to reduce weight. So, it is small and 1. It also has high terrain adaptability, and can therefore operate on complex terrain such as rough terrain and in narrow spaces.

What is particularly important is that according to the present invention, it is possible to obtain a levitator using a propeller with a small diameter, which was conventionally considered to be disadvantageous based on common sense.

[Brief explanation of the drawing]

Fig. 1 is an explanatory plan view of the hydrodynamic hovercraft of the present invention, Fig. 2 is an explanatory side view of the hydrodynamic hovercraft of the invention, and Fig. 3 is an explanatory diagram showing airflow when the propeller is rotated near the ground. , Figure 4 is an explanatory diagram showing the influence of induced speed on the lift and drag of the blade element, Figure 5 is an explanatory diagram showing the radial length and circumferential length of the propeller, and Figure 6 is an explanatory diagram showing the engine output and rotation. It is a graph showing the relationship between numbers. 1...Bumper 2...Frame 3...Power source 4...Rotating device 5...Propeller 6...
・Deflection plate 7...Rotation axis of deflection plate 8...Arrow
9... Ground 10... Power device 11... Streamline
12...Rotation surface of propeller 100...Dynamic pressure type hovercraft Figure 3 Figure 4 Figure 5 Output maximum Maximum number of rotations procedure amendment (adjustment) July 22, 1985 1, Incident display □ Patent Application No. 226995 filed in 1982 2, name of the invention Dynamic Pressure Hovercraft 3, relationship with the case of the person making the amendment Patent Applicant Address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo (1)
14) Name: Director of the Agency of Industrial Science and Technology, etc. Ka Tatsu 4, Designated agent: 305 5, Date of amendment order: Voluntary 1, Specification ■) Letter M for amendment No. 1 in the column of detailed explanation of the invention
In the 8th line of page 3, [Weight 20K (JJ) is corrected to [Weight 160 (JJ).

Claims (1)

[Claims] A propeller having blade elements with a blade width ratio of more than 0.1 is attached below the fuselage, and is configured to generate dynamic pressure without restricting the air flow accompanying the rotation of the propeller. Pressure type hovercraft.