Structure and method for improving glide ratio of ram-air parachute

Abstract

The application discloses a method for improving glide ratio of a ram-wing parachute, and belongs to the technical field of ram-wing parachutes. The glide performance of the ram-wing parachute is improved by changing the shape of the parachute cloth through a mechanism method. The shape memory alloy is adopted. After the ram-wing parachute inlet parachute cloth is unfolded, the resistance wire is heated, the shape memory alloy wire props up the cover cloth at the leading edge cutout, and the shape memory alloy wire restores to a shape capable of cutting off the ram-air inlet. The leading edge air inlet is in a closed state. The method can solve the adverse effect of the ram-wing parachute leading edge air inlet on the glide performance of the ram-wing parachute, and improve the aerodynamic performance of the ram-wing parachute.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ram-air parachute, and particularly relates to a structure and method for improving glide ratio of ram-air parachute. BACKGROUND

[0002] Ram-air parachute has provided a new direction for the development of parachute since the 1960s. Unlike the super-large open parachute of the traditional parachute, the ram-air parachute mainly relies on the open leading edge to intake air, forms ram air during flight, and forms stagnation pressure in the cavity due to the low air permeability of the parachute material to maintain the shape of the canopy. After being filled with air, the ram-air parachute is similar to a curved wing, which can generate sufficient lift. At the same time, the ram-air parachute itself does not have a large mass because its material is mostly light fabric, and compared with the traditional parachute, the ram-air parachute has controllability and high gliding ability. With the rapid development of aerospace technology and the continuous expansion of related technical application fields, the ram-air parachute has a wide range of applications in precision air drop, spacecraft recovery and civilian fields.

[0003] Due to the influence of factors such as fabric air permeability and bulging, the glide ratio of the folded high-altitude inflatable wing parachute is generally about 1.5 to 3.2. At present, after the structure is optimized and high-performance fabric materials are selected, the glide ratio of this type of wing parachute can reach 4.8, but it is very difficult to be higher than this value. There are individual documents that mention that the highest glide ratio of the wing parachute reaches 6, but this state is only obtained at a certain angle of attack and a certain speed. In order to better improve the maneuverability and gliding ability of the wing parachute, improving the glide ratio is undoubtedly one of the important means. Most of the current wing parachute structure designs are conventional designs, and it is difficult to further improve the glide performance. SUMMARY

[0004] The application provides a structure and method for improving the glide ratio of a ram-air parachute, which can greatly improve the aerodynamic performance of the wing parachute, thereby improving the glide performance of the ram-air parachute.

[0005] To achieve the above object, the application adopts the following technical scheme:

[0006] A method for improving the glide ratio of a ram-air parachute, comprising the following steps: after the ram-air parachute intakes air to support the canopy, the leading edge intake port is blocked to form a closed state, so that the leading edge cutout no longer intakes air, and the flow directly bypasses the upper and lower wings of the wing parachute, and no longer mixes with the gas in the cavity.

[0007] In the above steps, the shape memory alloy is used at the leading edge cutout of the ram air wing parachute, connected with a piece of canopy cover cloth with appropriate shape and size, and serves as a closing role. When the ram air wing parachute is in air, the shape memory alloy wire is not heated, the leading edge cutout remains open, and the wing parachute can be rapidly inflated to form a wing parachute shape for gliding. When the wing parachute keeps open state and starts gliding, the shape memory alloy is heated by the electric heating wire, and the shape memory alloy deforms to restore the state. The small piece of canopy cloth at the leading edge cutout is supported by the shape memory alloy wire and serves as a closing role, so that the wing parachute becomes a closed wing parachute.

[0008] The structure for improving the glide ratio of the ram air wing parachute in the above method comprises: a canopy system and a hanging object system, the canopy system and the hanging object system are connected through a parachute rope, the canopy system is composed of upper and lower wings made of air impermeable coated fabric and wing ribs between the upper and lower wings, the upper and lower wings and the wing ribs form a plurality of air chambers, the shape memory alloy wire is adhered to the lower wing canopy and installed in each air chamber, the shape memory alloy wire is installed at the leading edge cutout of the ram air wing parachute and connected with a piece of canopy cover cloth with appropriate shape and size, the shape memory alloy wire is connected to the electric resistance wire laid in the canopy, the electric resistance wire is heated by a small generator and conducts heat to the shape memory alloy to control the deformation, the small generator is arranged in the hanging object system, and the electric resistance wire is connected to each air chamber through the parachute rope.

[0009] Beneficial effects: the structure and method for improving the glide ratio of the ram air wing parachute can improve the gliding performance of the ram air wing parachute by changing the canopy structure and shape of the ram air wing parachute through a mechanism method. The air inlet at the leading edge cutout of the ram air wing parachute greatly increases the drag of the wing parachute, reduces the lift of the wing parachute, and reduces the stall angle of attack of the wing parachute, so that the wing parachute stalls in advance. The shape memory alloy wire is used at the leading edge cutout of the ram air wing parachute and connected with a piece of canopy cover cloth with appropriate shape and size, which can serve as a closing role. When the ram air wing parachute is in air, the shape memory alloy wire is not heated, the leading edge cutout remains open, and the wing parachute can be rapidly inflated to form a wing parachute shape for gliding. When the wing parachute keeps open state and starts gliding, the shape memory alloy is heated by the electric heating wire, and the shape memory alloy deforms to restore the state. The small piece of canopy cloth at the leading edge cutout is supported by the shape memory alloy wire and serves as a closing role, so that the wing parachute becomes a closed wing parachute. After the ram air wing parachute inflates the canopy shape, the leading edge air inlet is blocked, the leading edge cutout is no longer in air, the flow no longer mixes with the gas in the cavity, but directly bypasses the upper and lower wings of the wing parachute, which can greatly improve the aerodynamic performance of the wing parachute, thereby improving the gliding performance of the ram air wing parachute. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is a structure schematic diagram of the wing parachute when the opening air inlet in the embodiment of the present application;

[0011] Figure 2The structure diagram of the wing parachute in the closed state without air intake in the embodiment of the present application;

[0012] Figure 3 The single air chamber diagram in the embodiment of the present application, wherein a is the air intake state and b is the gliding state;

[0013] Figure 4 The lift change rule diagram of the wing parachute in the embodiment of the present application;

[0014] Figure 5 The drag change rule diagram of the wing parachute in the embodiment of the present application;

[0015] Figure 6 The lift-drag ratio change rule diagram of the wing parachute in the embodiment of the present application;

[0016] Figure 7 The structure diagram of the test device in the embodiment of the present application. Embodiment

[0017] The present application will be described in detail below in combination with the drawings and specific embodiments:

[0018] The ram-air wing parachute system in the embodiment includes the canopy system and the hanging object system, the canopy system is mainly composed of the upper and lower wings made of the air impermeable coating fabric and the wing ribs between the wings, and the air chamber is formed after the ram air intake to maintain the wing shape; the lift of the wing parachute is almost provided by the canopy system, and the gliding performance of the ram-air wing parachute can be improved by changing the canopy structure shape of the ram-air wing parachute through the mechanism method; due to the influence of the leading edge air intake, the canopy aerodynamic performance of the ram-air wing parachute is greatly reduced, therefore, if the leading edge air intake port is blocked after the ram-air wing parachute air intake supports the canopy shape, the leading edge cut is no longer air intake, the coming flow is no longer mixed with the gas in the cavity, but directly bypasses the upper and lower wings of the wing parachute, the aerodynamic performance of the wing parachute can be greatly improved, thereby improving the gliding performance of the ram-air wing parachute.

[0019] The memory alloy wire is used at the leading edge cut of the ram-air wing parachute and connected with a canopy cover cloth with a proper shape and size, which can play the role of the closed state. As shown in Figures 1-3 When the ram-air wing parachute air intake, the memory alloy wire is not heated, the leading edge cut is kept open, and the wing parachute shape can be quickly inflated for gliding; when the wing parachute keeps the open state and starts gliding, the memory alloy is deformed and restored by heating the electric heating wire, the small piece of canopy cloth at the leading edge cut is supported under the action of the memory alloy wire, plays the role of the closed state, and makes the wing parachute become the closed wing parachute, thereby greatly improving the gliding performance.

[0020] Figure 7The device is fixedly installed below the test section of the wind tunnel, and sequentially comprises a fixed platform, a lifting platform, a rotating table, a three-dimensional force sensor, a support, and a rotatable flow dividing disc from bottom to top. The three-dimensional force sensor, also referred to as a strain type three-dimensional force sensor, can simultaneously detect the force value changes in the X-axis, Y-axis and Z-axis directions in space, and is a force measuring device based on the resistance strain principle. The three-dimensional force sensor can measure the X and Y direction forces of the parafoil model, i.e. the lift and drag of the parafoil, so as to obtain the lift-drag ratio of the parafoil, i.e. the glide ratio of the parafoil.

[0021] The rotating table can be pre-set by computer software, and multiple angles can be simultaneously given with a stable time length in a group of measurement experiments, so as to ensure the stability and continuity of a group of measurement results. A flow dividing plate is used as a symmetry plane of the half model parafoil in the test section, so as to reduce the influence of the air power on the device and the force measurement, and prevent the influence of the boundary layer effect of the bottom surface of the wind tunnel on the test results. In the experiment, each model is measured at multiple attack angles, i.e. α = -2°, 0°, 2°, 4°, 6°, 8°, 10°, 12°, 14°, 16°, 18° and 20°, and a total of 12 angles. The angle of rotation of the rotating table can simulate the attack angle of the parafoil, and finally the aerodynamic parameters of the parafoil at each attack angle are obtained.

[0022] The wind speed during the experiment is 20 m / s, simulating the flight condition of the parafoil in the movement process. Each model is measured twice, and each group of experiments is first carried out a group of zero working conditions without wind, and then a group of working conditions with wind, so as to eliminate the error of external factors on the experimental measurement. The final experimental results are corrected to obtain the drag D and lift L of the parafoil model in two states as shown in Figure 4 and Figure 5 and the lift-drag ratio as shown in Figure 6 It can be seen from the figure that the front edge closed without air intake can greatly improve the aerodynamic performance of the ram-air parafoil. The front edge closed without air intake can increase the stall attack angle of the parafoil, and the stall attack angle of the parafoil in the state of the front edge closed without air intake is about 16°, while the stall attack angle in the state of the front edge open air intake is about 14°. At the same time, when the attack angle of the parafoil exceeds the best attack angle, the front edge closed without air intake can have better lift than the front edge open air intake. In the whole attack angle range, the front edge open air intake can increase the drag of the parafoil, and finally the lift-drag ratio of the parafoil in the state of the front edge closed without air intake is better than that in the state of the front edge open air intake. The front edge closed can improve the lift-drag ratio of the parafoil by about 20%, which means that the glide performance of the parafoil is greatly improved.

[0023] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of increasing glide ratio of a ram-air parachute, characterized by, The ram air wing parachute comprises a canopy system and a suspension system, which are connected by a parachute rope; the canopy system is composed of upper and lower wings and wing ribs therebetween, the upper and lower wings and the wing ribs form a plurality of air chambers, one side of the air chamber is closed and the other side is open, a shape memory alloy is installed in each air chamber, a canopy cover cloth with appropriate shape and size is connected, and the cover cloth can close the air chamber opening when the shape memory alloy deforms; the shape memory alloy is installed at the leading edge cutout of the ram air wing parachute and connected with a canopy cover cloth with appropriate shape and size, when the ram air wing parachute is in air, the shape memory alloy is not heated, the leading edge cutout remains open, the ram air wing parachute is inflated to support the canopy, and after the ram air wing parachute generates enough lift to start gliding, the shape memory alloy is deformed by heating to restore the state, the small piece of canopy cloth at the leading edge cutout is supported by the memory alloy wire to close the leading edge cutout of the wing parachute, so that the leading edge cutout is no longer in air, and the flow directly bypasses the upper and lower wings of the wing parachute, and the gas in the cavity no longer mixes with each other, and the leading edge inlet of the wing parachute remains open when air is needed.

2. A ramwing parachute for improving glide ratio of a ramwing parachute, characterized by, The ram air wing parachute adopts the method of claim 1 to improve the glide ratio of the ram air wing parachute; the ram air wing parachute comprises a canopy system and a suspension system, which are connected by a parachute rope; the canopy system is composed of upper and lower wings and wing ribs therebetween, the upper and lower wings and the wing ribs form a plurality of air chambers, one side of the air chamber is closed and the other side is open, and the shape memory alloy is installed in each air chamber, a canopy cover cloth with appropriate shape and size is connected, and the cover cloth can close the air chamber opening when the shape memory alloy deforms.

3. Ram wing parafoil with improved glide ratio of the parafoil according to claim 2, characterized in that The shape memory alloy is connected to the resistance wire laid in each air chamber of the canopy, and the resistance wire is heated by a small generator to conduct to the shape memory alloy to restore the deformation.

4. Ram wing parafoil with improved glide ratio of the parafoil according to claim 3, characterized in that The small generator is placed in the suspension system, and the resistance wire is connected to each air chamber through the parachute rope.

5. The ram wing parafoil of claim 2, wherein, The canopy system is made of a gas-impermeable coated fabric.

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