How big is the jet engine of an airplane?

ByClément Alloing

The size of the jet engine used for airplanes is designed based on the calculation of propulsive power and fuel consumption. In recent years, although it is a jet engine of an airplane which tends to increase in diameter, "How much can it be possible to scale up" and "What is the mechanism of a jet engine in the first place" is explained in a movie with illustration.

Why Are Airplane Engines So Big? - YouTube


The jet engine of an airplane is getting bigger and faster as it becomes fresher.


On the other hand, the size of the airplane is not increasing together.Boeing 747While the total length is 70.6 meters, the state-of-the-artAirbus A 350The total length is only 60.7 meters. However, even though the aircraft is small, the jet engines installed are bigger than the 747 aircraft.


Should the engine of the airplane grow bigger and bigger? Speaking of it, it is not so, it is up to a certain size that can maintain high efficiency.


The modern jet engine combines two propulsion mechanisms. A fan (propeller) was added to the core turbojet engine, and "Turbo fan engineIt is called.


On the other hand, the pure "jet engine" used in passenger aircraft and fighter aircraft of ancient times is terribly inefficient instead of realizing super high speed. Kinetic energy is proportional to the square of speed, so if you accelerate to twice the speed of a passenger aircraft, you actually need four times more energy.


Instead of getting powerful power, the majority of energy is sparged as enormous thermal energy, so fuel efficiency gets worse.


Of course, in order to obtain propulsive power with a jet engine, it is necessary to discharge combustion gas from the rear of the engine, but there are also methods that do not necessarily require a large amount of energy.


How can we make the efficiency better than the jet engine? Instead of taking in a little air and discharging it at ultra-high speed, if we can take in a large amount of air and discharge it at such a reasonable rate, we should be able to obtain hope's driving force while suppressing energy consumption. That is the aim of the turbofan engine.


The size of the engine of the airplane is made by calculating the above efficiency, and if the engine is too small, it is forced to release a lot of air as energy to accelerate it. For example, it's like shooting a machine gun backwards to get the driving force of a car.


On the other hand, if the engine is too big, the air resistance generated by the engine itself will be too great and the efficiency will be lowered.


In other words, the ideal size of the engine was taken in the middle "not too big, not too small." Approximately "engine with 4 meters in diameter" is the most efficient.


Speaking of 4 meters in diameter, it is slightly larger than the world's largest engine at present. Therefore, although it is expected that the jet fan engine will continue to grow in the future, it will not be increased in size forever.