【Aviation English-26】Why Are Airplane Engines So Big? ( 為什麼飛機發動機這麼大？ )

Scroll down to view the Simplified Chinese version (向下滚动查看简体中文版本)  Why Are Airplane Engines So Big? Airplane jet engines have gotten bigger and bigger over time - and it’s not just because planes are getting bigger: the Airbus A350 is a Smaller plane than the Boeing 747 but has bigger engines.
The reason?
Bigger engines are simply more efficient, up to a point.
Modern jet engines actually consist of two propulsion systems working together: the jet core, which provides the power and a small amount of thrust, and the fan, which is just a big propellor driven by the jet core that provides most of the thrust.
Pure jet engines can be incredibly powerful (which is why they’re used for fighter jets), but they’re also horribly inefficient because they shoot out their exhaust at super-high speeds, which equates to huge amounts of kinetic energy since kinetic energy is proportional
to the speed squared, so accelerating exhaust to twice the speed takes 4 times the energy.
In exchange for power, they literally blast energy away like a bunch of hot air. Of course, you do have to shoot some air out of the back of an engine to generate thrust, but it doesn’t have to have lots of energy.
Instead of accelerating a little bit of air a lot, you can achieve your desired thrust by accelerating a lot of air a little bit - you get the same momentum boost but save a ton of energy.
Essentially, if you make an engine too small, it has to accelerate the air so much as to be a waste of energy – kind of like using a machine gun to propel your car.
But if you make the engine too big, then it starts to cause too much drag.
An ideal engine is somewhere in between – rough estimation puts the ideal engine somewhere around 4 meters in diameter, which is just slightly bigger than the current largest engines.
So you can expect jet engines to continue growing in size... but not forever. Simplified Chinese version 飞机发机为何如此庞大？ 随着时间的推移，飞机喷气发动机变得越来越大 - 这不仅仅是因为飞机越来越大：空客 A350 比波音 747 小，但发动机更大。 原因是什么？ 在一定程度上，更大的发动机效率更高。 现代喷气发动机实际上由两个共同工作的推进系统组成：喷气核心，提供动力和少量推力，风扇，只是一个由喷气核心驱动的大型螺旋桨，提供大部分推力。 纯喷气发动机可以非常强大（这就是它们用于战斗机的原因），但它们的效率也非常低，因为它们以超高速度喷出废气，这相当于巨大的动能，因为动能与速度的平方成正比，因此将废气加速到两倍的速度需要四倍的能量。 作为动力的交换，它们实际上像一堆热空气一样将能量吹走。 当然，你确实需要从发动机后部喷出一些空气来产生推力，但这并不需要很多能量。 你不必大量加速少量空气，而是可以通过少量加速大量空气来实现所需的推力 - 你可以获得相同的动量提升，但节省大量能量。 本质上，如果你制造的发动机太小，它必须加速空气，以至于浪费能量 - 有点像用机关枪推动你的汽车。 但是如果你把发动机做得太大，那么它就会开始造成太大的阻力。 理想的发动机介于两者之间 - 粗略估计理想发动机的直径约为 4 米，略大于目前最大的发动机。 因此，你可以预期喷气发动机的尺寸会继续增大......但不会永远增大。 Discussion Questions (Airplanes) (1) What springs to mind when you hear the word ‘airplane'? (2) How important are airplanes? (3) What do you know about the history of airplanes? (4) What different kinds of airplanes are there? (5) How have airplanes changed over the years? (6) Would you like your own plane? (7) What is the best airplane in the world? (8) Is it better to travel by airplane or by cruise ship? Why? (9) What do you think when you see an airplane in the sky? (10) Would you like to work on an airplane? (11) How do airplanes work? (12) How dangerous are airplanes? (13) What will airplanes be like in the future? (14) Which is better, Boeing or Airbus? (15) What movies have you seen about airplanes? (16) Would you like to fly (pilot) an airplane? Why? (17) What effect do airplanes have on the environment? (18) How do airplanes get off the ground and fly? (19) How cool are airplanes? (20) What three adjectives describe airplanes?   Discussion Questions (Airports) How many times have you been to an airport? Do you like them? How far is the closest airport to you? What is it called? Do you think airports are over-priced? How much do you usually pay for a meal? Have you ever missed a flight? What happened, and what did you do? How early do you usually arrive at an airport before a flight? What things do you dislike most about airports? Do you like to talk to strangers at airports? How do you start a conversation? What things are cheap to buy inside airports? What is the best way to pass the time while waiting at airports? Have you ever been in a first-class lounge? What was it like inside? What is the first thing you do when you arrive at an airport? Do you feel relaxed or tense when you are at airports to catch flights? What things do people need to remove or take off at x-ray scanners? Would you like to work at an airport? What job  would you like to do? What things do you need to provide at airline check-in desks? What do you usually take in your carry-on baggage? Have you ever had to remove something from your bag at an airport? Why? What is the longest amount of time  you have ever spent at an airport terminal? Some people have lived in airports for months. Do you think you could do this? What are the best and worst airports you have been to? Are there any airport rules that you don’t agree with? What are they? Do you feel confident speaking English at airports? What kinds of problems can people experience inside airports? Have you ever had an interesting experience related to an airport? What was it? Discussion Questions (Flying) 1 –  Where do you prefer to sit on a plane? Do you prefer the window or aisle seats? 2-  Who do you like traveling with? When did you last go on a flight together? 3 –  What airlines have you flown with? Which one was best? Were the seats large enough? 4 –  Do you get scared or nervous on planes? What are you afraid of? 5 –  What is the longest flight you’ve ever taken? Did you enjoy the flight? 6 –  Would you like to be a pilot? How long does it take to become a pilot? 7-  Have you ever met an annoying person during a flight? What happened? 8 –  What do you think of airline food? Do you ever bring your own food on planes? 9 –  What things can’t you take on a plane? Have you ever had something confiscated? 10 –  Can you sleep  on planes? What can help you do this? 11 –  What things do you do to pass the time on plane flights? 12 –  How early do you go to the airport before a flight? Do you like airports? 13 –  What things do you take on flights? What are they for? 14 –  What 3 words would you use to describe planes? 15 –  Have you experienced turbulence? How did you feel? 16 –  Do you think flying is safer than driving ? 17  – Have you ever had your flight canceled or delayed? How long did you have to wait? 18 –  Do you enjoy takeoff and landing? 19 –  How far is the nearest airport from your home? Do you often see planes in the sky? 20 –  Are there any airlines you refuse to fly with? Why don’t you like them? 21 –  What movies have you seen about airplanes? 22 –  What do you usually buy at airports ? Are these things expensive? 23 –  How much baggage do you take when you fly? What kind of luggage do you use? 24 –  Have you ever lost your baggage or had something broken? What happened? 25 –  What are the best and worst airports that you have been to?