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喷气式发动机如何工作 – 译学馆
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喷气式发动机如何工作

Jet Engine, How it works ?

Jet engines have been the successful drivers of aircrafts for nearly a century now
近一个世纪以来 飞机普遍使用的是喷气发动机
In this video
本期视频
We will explain the technology behind the jet engine in a logical step-by-step manner
将为大家逐步解析 喷气发动机背后的技术原理
A jet engine keeps an aircraft moving forward using a very simple principle
喷气发动机推进飞机的原理非常简单
The same that makes an air-filled balloon move
好比气球装满空气 放手便飞出一样
Yes, Newton’s third law of motion
背后原理都是牛顿第三运动定律
Just like the reaction force produced by the air moves the balloon
就像气流产生反作用力 推动气球一样
The reaction force produced by the high speed jet at the tail of the jet engine makes it move forward
喷气发动机尾部的高速气流也产生反作用力推进飞机
So the working of jet engine is all about producing a
所以 喷气发动机的关键就是
high-speed jet at the exit
从出口处喷出高速气流
The higher the speed of the jet,the greater the thrust force
喷气速度越快 推力就越大
The thrust force makes an aircraft move forward
推力推进飞机向前移动
Such high-speed exhaust is achieved by a combination of techniques
得益于多项技术的联合运用 排气才如此高速
If you can heat the incoming air to a high temperature,
将吸入的空气加热到极高的温度
it will expend tremendously and will create the high velocity jet
空气体积将极大地膨胀 并产生高速气流
For this purpose,a combustion chamber is used
为了实现这点 燃烧室应运而生
An atomized form of the fuel is burnt in the combustion chamber
雾化形式的燃料在燃烧室中燃烧
Effective combustion requires air to be at moderately high temperature and pressure
空气需维持适宜温度与压力以达到有效燃烧
To bring the air to this condition
为使空气达到这种状态
A set of compressor stages are used
需要使用一组多级压气机
The rotating blades of the compressor add energy to the fluid
压缩机上的旋转叶片会增加气流通量
and its temperature and pressure rise to a level suitable to sustain combustion
气流温度与压力上升 到达维持燃烧的适宜水平
The compressor receives the energy for the rotation from a turbine
安装在燃烧室后面的涡轮
which is placed right after the combustion chamber
通过旋转为压气机提供能量
The compressor and turbine are attached to the same shaft
压气机和涡轮在同一根轴上
The High-energy fluid that leaves the chamber makes the turbine blades turn
燃烧室喷出的高能气流使涡轮叶片转动
You can see that
大家可以看到
the turbine blades have a special airfoil shape
涡轮叶片呈特殊的机翼形状
which creates lift force and make them turn
能产生升力 使得涡轮转动起来
As the turbine absorbs energy from the fluid
当涡轮从气流中吸收能量
its pressure drops
压力会下降
Through these steps
通过这几步
we have achieved our objective
我们的目标达到了
A really hot and high-speed air emitted from the exit of the engine
那就是 发动机出口排出高速热空气
The engine case becomes narrower towards the outlet
发动机匣朝出口方向逐渐变窄
which results in even greater jet velocity
因而会产生更大的喷射速度
In short
简而言之
the synchronized operation of the compressor combustion chamber and turbine makes the aircraft move forward
压气机 燃烧室和涡轮同步运作 推进飞机前进
Modern aircrafts use a slightly [improved] compressor turbine arrangement called a two spool
现代飞机使用的双轴发动机 对压气机涡轮布局稍有改进
Here two independent turbine compressor stages are used
采用两级独立的涡轮压气机
The shaft of the outer compressor turbine passes concentric through the inner one
外压气机涡轮轴穿过内压气机涡轮轴的轴心
The outer turbine is subjected to a low energy fluid and will run at a lower speed than the inner turbine
外涡轮受低压气流的影响 运转速度比内涡轮低
Low pressure blades are longer
低压区叶片更长
This [low-speed] helps to reduce centrifugal stress induced at the root
低速有利于减少来自尾部的离心力
Thus improving the blades life
从而提高叶片的使用寿命
Some modern aircrafts even use a three spool engine
部分现代飞机甚至使用三轴发动机
The engine we have discussed so far is more specifically called as turbo jet engine
这里讨论的发动机 更确切地说 叫涡轮喷气发动机
Turbo jet engines tend to Produce high levels of noise
涡轮喷气发动机往往会产生很大的噪音
Revolutionary Improvement was made to this engine by fitting a large fan with the low pressure spool
在低压轴上安装一个大风扇克服了这一缺点 可谓革新之举
Such engines are called Turbofan engines
这种发动机称为涡扇发动机
and almost every commercial aircraft run on them
几乎所有商用飞机使用的都是涡扇发动机
A Turbofan engine bypass is a huge amount of air
涡扇发动机旁通内有大量空气
The ever narrowing bypass duct provides a good jet velocity to the bypassed air
旁通空间不断变窄 旁通空气加速向外排出
In a turbofan engine,
在涡扇发动机内
the majority of the thrust force comes from the fans reaction force
主要的推力来自于风扇的反作用力
Further the fan greatly improves Airflow in the system by sucking in more air
而且 风扇吸入更多空气 大大增加了系统中的气流
Thus it helps to improve the thrust
因而增加了推力
This means high thrust creation with an expense of slightly more fuel
这意味着 稍加燃料 便可产生很大的推力
This is the reason why Turbofan engines are highly fuel economical
这便是涡扇发动机燃料经济性高的原因
The noise produced by a jet engine is highly dependent on the exit jet velocity
喷气发动机产生的噪音与出口处喷气速度密切相关
Since in a turbofan the bypassed cold air gets mixed with the hot air
这是由于涡扇旁通内冷热空气混合
it is possible to keep the outlet velocity within a limit
将出口处喷气速度降低在一个范围内
Thus it overcomes the noise problem
从而解决了噪音问题
With quieter exhaust and better fuel economy,
由于排气时更安静 燃料经济性也更高
the turbofan engines continued to dominate aircraft propulsion systems
目前 飞机的推进系统普遍使用涡扇发动机
We hope this provided a nice introduction to the working of jet engines.
希望这个介绍能帮助大家了解喷气发动机的原理
Thank you for watching this video
感谢收看本期视频

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视频概述

本期视频带领我们了解喷气式发动机背后的秘密,一起感受科学与智慧的魅力

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视频来源

https://www.youtube.com/watch?v=KjiUUJdPGX0

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