Aircraft information

Classification: social livelihood >> Military

Problem description:

Go, go, go, go, go, go, go, go, go, go, go, go.

Analysis:

First of all, the buoyancy of the wing:

0 1. Bernoulli principle: In a fluid, when the flow rate increases, the pressure will decrease, and vice versa. So, something in the fluid.

Experience moving to a fast-moving place.

02. The principle of wing profile:

A. the typical wing profile is shown in figure 1. The upper distance is relatively short.

It's a long, short distance down there. The air streamline is divided according to the wing profile.

Divided into two parts, the two airflow speeds behind the wing are the same.

Speed, so the air passes through it faster, air.

The pressure is very small, forming an upward lift. (see figure 1.

The observation of airflow passing through the wing can be tested in the "smoke hole". )

B Normally, gas has a certain viscosity, that is, when it passes through an object, it will act along the tangential force on the surface of the object.

On an object, the speed of the nearest air streamline is zero, and the speed of air to the rear returns to the original speed.

The airflow with the velocity from zero to the original velocity is called boundary laminar flow, which is separated from the wing surface at the rear.

The separation point is called the separation point, where the airflow forms turbulence (~ ~).

C. Mode of contact with air:

Take kites as an example. If the layout is perpendicular to the wind direction, kites can only

Go straight ahead (as shown in Figure 2- 1), if it is at an angle with the wind direction, then

Will continue to rise. The angle between the wind direction and the wing is called angle of attack.

(Angle α in Figure 2-2). In Figure 2-2, a is the upward force,

B is the forward thrust, and C is the friction parallel to the kite layout.

Friction (that is, resistance), the resultant force of A and B is lift.

And the resistance is a component of a pair of mutually perpendicular winds).

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Aircraft flight principle

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At a certain angle, the greater the angle of attack, the greater the lift.

The force coefficient is linearly proportional to the angle of attack; Exceeding this feature

At a fixed angle, the lift drops sharply and the drag increases. This special

The angle varies with the shape of the object. This relationship can be represented by a chart.

3. At a glance, I don't consider other variable assumptions, _ _ _ _ _ _

Surface version, _ _ _ _ _ surface lift (that is, the resultant force of A and B), _ _ _ _ _ _

Table 2 shows a mutually perpendicular lift component (i.e. the force shown in Figure 3).

These two parts are perpendicular to each other, that is, they can be triangular parts.

The hypotenuse and height indicate. ) and the angle is less than 45 degrees.

The greater the angle, the greater the lift, and the angle of 45 degrees can be regarded as

The specific angle of this situation. But on the other hand, the plane's

The greater the angle of attack, the more the separation point moves forward and the greater the disturbance.

The pressure of air flow is compared with that of steady air flow (laminar flow).

Large, so when the angle is greater than a certain angle, the lift will be very urgent.

There is also a saying that resistance rises when it drops sharply.

Resistance is caused by friction between air and the surface of an object.

Surface friction resistance, surface friction resistance in turbulent flow Figure 4. (Excerpted from Note 2)

It is much larger than laminar flow, so the above-mentioned situation that lift decreases and resistance increases is called stall.

The principle of wing stall is related to the descent angle of the aircraft. In fig. 4, Cl represents the lift coefficient, which increases with the increase of angle of attack.

In addition, the lift coefficient also increases (Cl = A α, where a is the slope of the lift line) until it reaches the maximum value L of the lift coefficient.

The force coefficient decreases to form stall.

D the above wing profile principle is also applicable to rotorcraft (such as helicopter).

On the rotor and wing of an airplane.

Figure 5. →

Second, the engine power:

There are two kinds of 0 1. aircraft, one is called light aircraft, which uses gas lighter than air to fly; The other is heavy aircraft, that is,

Fly at speed (that is, relative airspeed).

A. Generally speaking, if other factors are not considered, the initial speed will only

It will increase the flight distance and will not stay in the air.

Time increases, as shown in Figure 6.

B: Like a paper plane with wings, it is buoyant and relative.

The speed of air (bernhard's principle) makes paper airplanes.

Can stay in the air, but relative to the resistance caused by lift

This force slows down the speed of the paper plane and eventually leads to lift. Figure 6. (simulating flash photography per unit time)

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Aircraft flight principle

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Not enough to overcome gravity and fall, or even fall.

C. Therefore, the Wright brothers installed an engine on the plane to provide sustained speed for the plane to overcome the resistance and make human beings stable.

To realize the dream of flying.

02. The principle of the engine:

A. turbojet engine

Figure 7. (reprinted from the structure of jet engine on page 9/kloc-0 of Aircraft Rocket)

The core of turbojet engine can be divided into: compression section, combustion chamber and turbine. The compression part consists of many blades that can transport air.

After compression, it is sent to the rear, and the combustion chamber has a pipeline to send fuel and air for mixed combustion. Turbines are also made up of many blades.

Air is blown in from the compression section, and the gas is heated and pressurized by the compressor, then sent to the post-combustion chamber to be mixed with fuel and burned at high temperature and high pressure.

The gas suddenly ejects backward, creating pressure and generating forward thrust. At the same time, high temperature and high pressure gas blows to the vortex.

Blade of the turbine, the rotation of the turbine drives the rotation of the front compressor.

The advantage of using jet engine is that it can reach very fast speed, even supersonic speed, which was mainly used in military aircraft in the early days.

B. turbofan engine

Figure 8. (Schematic diagram of turbofan engine on page 27 of Xinzhi 2 12 Flight Century)

Although the turbojet engine is fast, it consumes too much fuel for low-speed civil aircraft, so some people say it is turbojet.

A fan is added in front of the engine, which is connected with the turbine, and the turbine drives the fan to rotate. When the fan rotates, it also increases in size.

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A lot of air is sent to the back. The power of this engine mainly depends on the airflow generated by the front blades. As for the principle, I think it should be

This is because the fan rotates to suck in a large amount of air to increase the thrust, and on the other hand, the suction of a large amount of air also reduces the air resistance in front.

Forward. Probably similar to the principle of propeller. The specially shaped pages make the air in front faster than that in the back, so the air pressure in front is high.

The advantage of this kind of engine is that it doesn't consume oil, but its speed is relatively slow. In addition, it can be used at a slower speed.

In this case, more thrust will be generated.