Jet planes can fly up to 20,000 meters, so why can t propeller planes?

Because a jet can utilize his engine, a propeller plane doesn't have that feature. The highest flight record for a propeller aircraft is about 29,524 meters, which is about 1 5 times the altitude mentioned in this topic, and this record was achieved by an experimental team of NASA in 2001.

At that time, the team would break the record for continuous flight time for an aircraft powered by solar energy. They are looking at using solar energy to provide continuous energy to the aircraft so that the aircraft can stay in the air for the longest time. The plane itself is a flying solar panel with presumably 14 battery-powered electric motors driving the propellers to power the aircraft, and the total power of these 14 propellers is up to 40 kilowatts, compared to only 10 kilowatts when flying on batteries at night.

If you assign it to each engine, the wind blown by the engine is equivalent to an electric blower in a hair salon, and if you have friends who have carefully looked at this aircraft **, you may find that this is actually an aircraft with a high chord ratio, it is made of lightweight materials, and in this case, the plane can get enough lift even with a small thrust. This has nothing to do with propeller power, although thin propellers are less efficient at high air.

But a total thrust of 10 kilowatts is enough to keep the plane in the air, and in fact, a conventional propeller aircraft moves forward through the pull created by the propeller agitating the air. And because when the air is thin, the pulling force generated by each rotation will decrease, and it is necessary to increase the pulling force, in addition to changing the angle of the propeller, the best way is to increase the rotational speed, but because the propeller itself has a diameter.

As for the question of why propeller planes can't fly jets up to 20,000 meters, I will explain it here today.

Because at an altitude of 20,000 meters, the air is very thin, and the lifting force of the propeller cannot support the aircraft to reach such an altitude, so the jet plane can fly to 20,000 meters, but the propeller aircraft cannot.

There is no air at an altitude of 20,000 meters. The spiral plane takes off by relying on the gas in the air, and there is no gas in the atmosphere at an altitude of 20,000 meters.

Because propeller aircraft rely on the propeller rotation to generate an upward force in the air to lift the aircraft. The air at an altitude of 20,000 meters is thin and it is difficult to generate enough upward force.

We all know that propeller planes don't fly as fast as jets, but why is that? To understand this problem, we have to start with how the two work.

As we know, propeller aircraft use piston engines, and rely on the propellers to generate the pulling force of the aircraft. The piston engine used in airplanes is basically the same as the engine used in cars today, but it is lighter and more powerful. When the piston engine works, it drives the aircraft propeller to rotate and blows the air backwards, so that a reaction force is generated on the propeller.

This force is transmitted to the aircraft, and it becomes the pulling force that drives the aircraft forward. The power of the engine is small, and the pull force that makes the aircraft move forward is small, and the speed of the aircraft is bound to be not fast. In order to make the plane fly faster, people try to increase the power of the engine in every possible way.

However, when the power of the aviation piston engine is large enough to allow the aircraft to reach a speed of about 750 kilometers per hour, it is difficult to increase the speed of the aircraft even more. On the one hand, because the speed of the propeller is not unlimited; On the other hand, when the speed of the aircraft is so fast that the speed of the propeller relative to the air is close to the speed of sound, an air wave is generated in front of the propeller, like the bow wave that occurs when the ship is moving at high speed on the water, called a "shock wave". The drag caused by this shock wave is so great that the efficiency of the propeller immediately drops sharply.

No matter how powerful the engine is, the plane still does not fly fast. Therefore, to make the plane fly fast, to the speed of sound, the piston engine is powerless.

Jets are different. The jet engine is burned by air and gasoline, producing a large amount of high-temperature and high-pressure gas, which is injected backwards to produce thrust to move the aircraft forward. Jet aircraft are particularly suitable for high-speed flight because of the direct reaction force generated by the high-speed jet air flow to propel the aircraft to fly, unlike the propeller aircraft, which will decrease in efficiency when flying at high speeds.

At present, some jet fighters have reached a maximum speed of 3,000 kilometers per hour, which is equivalent to twice the speed of sound.

Defense News.

The propeller Luga airliner flies v-kilometer-hour in an early position.

v(1+2/5)=910

v=650 km hourly search.

Let's start by looking at how an airjet engine works. After the air flows into the jet engine, it passes through a compressor made up of many blades. After the air is compressed by the compressor, high-pressure air is formed into the combustion chamber, mixed with fuel and burned, becoming a high-temperature gas with a lot of energy and spraying back.

When these high-temperature and high-pressure gases are sprayed out of the hand, they will push the first-stage or multi-stage turbine to rotate at high speed, and will also drive the compressor to rotate. High-temperature and high-pressure gas flowing through the turbine is ejected outward at high speed from the tail nozzle. The backward ejection of gas exerts forward thrust on the engine, which is how the current turbojet engine (turbojet engine for short) works.

In order to further improve the efficiency of the jet engine, someone added a fan with a larger diameter in front of the turbojet engine to form a "turbofan engine" (referred to as the turbofan branch engine). A part of the air passing through the fan flows through the outer channel of the compressor, combustion chamber and other components, which is called "outer connotation airflow"; A part of the air flows through the compressor and combustion chamber as usual for combustion and is sprayed back at high speed, which is called "contrived airflow". The flow ratio of the outer airflow to the inner airflow is called the "bypass ratio".

Turbofan engines with small bypass ratios are mainly used in bombers and attack aircraft, and turbofan engines with large bypass ratios are mainly used in passenger aircraft and transport aircraft.

In 1946, the United States hoisted four turbojet engines on top of the original six piston engines and propellers of the B-36, which became the largest bomber at that time. However, it only flies at a speed of 300 km, carries 4,540 kg of bombs, and has a round-trip range of 8,450 km, but it is too slow to be attacked.

The other is the XP-81 single-seat lower wing fighter launched by the United States in 1945, which is also a mixture of a piston engine and a turbine engine.

The first floor of the master has already explained the mixed engine of the aircraft.

At present, some large military transport aircraft use turbofan engines, and fan blades are installed in front of the jet engine, and the advantage of this engine is fuel economy and high efficiency.