Steam turbines lie at the heart of these power plants.

蒸汽輪機是這些發電廠的核心。

They convert thermal energy in the steam to mechanical energy.

它們將蒸汽中的熱能轉化為機械能。

This video will explain the inner workings of the steam turbines and why they are constructed in the manner they are in a step-by-step logical manner.

本視頻將以循序漸進的邏輯方式解釋蒸汽輪機的內部構造以及其構造方式的原因。

To understand its basic workings, let's first observe one of their blades.

為了瞭解它的基本工作原理，我們先來觀察一下它的一個葉片。

You can see that the blade of a steam turbine has an airfoil shape.

您可以看到，蒸汽輪機的葉片呈翼形。

When the high-energy fluid passes over it, this airfoil shape will create a pressure difference.

當高能流體經過它時，這種翼面形狀會產生壓力差。

This will subsequently create lift force.

這樣就會產生升力。

The lift force will rotate the turbine.

升力將使渦輪機旋轉。

In short, the energy in the fluid transfers to the mechanical energy of the rotor.

簡而言之，流體中的能量轉移到轉子的機械能上。

To further understand steam turbine operation, let's understand fluid energy in greater depth.

為了進一步瞭解蒸汽輪機的運行，我們先來深入瞭解一下流體能。

A fluid has three forms of energy due to its speed, pressure, and temperature.

流體因其速度、壓力和溫度而具有三種形式的能量。

As the blades absorb energy from the fluid, all three forms of energy come down.

當葉片從流體中吸收能量時，所有三種形式的能量都會下降。

The low-velocity jet is of no use to produce effective lift force.

低速射流無法產生有效的升力。

To increase velocity, the fluid is passed through a stator section.

為提高流速，流體通過定子部分。

The stator set is stationary and attached to the turbine casing.

定子組固定不動，與渦輪機機殼相連。

You can see that flow area decreases along the stator and the speed thus increases.

您可以看到，定子上的流通面積減小，速度是以增加。

In short, the stator acts like a nozzle.

簡而言之，定子就像一個噴嘴。

As the speed of the jet increases in the stator, kinetic energy increases.

隨著定子中射流速度的增加，動能也隨之增加。

As there is no net energy transfer in the fluid in stator section, the pressure and temperature of the jet should decrease to keep the total energy constant.

由於定子部分的流體中沒有淨能量轉移，是以射流的壓力和溫度應降低，以保持總能量不變。

Now, the next row of rotors is added.

現在，添加下一排轉子。

The stator also makes sure that the flow coming out of it will be at an optimum angle of attack to the next rotor set.

定子還能確保流出定子的氣流與下一組轉子的最佳夾角。

After that, another nozzle set is added.

之後，再添加一套噴嘴。

Many such sets are used in a steam turbine.

蒸汽輪機中使用了許多這樣的機組。

There is an important term while designing steam turbines, namely degree of reaction.

在設計蒸汽輪機時，有一個重要的術語，即反應度。

This term is calculated by dividing pressure and temperature energy by the total energy change in the rotor.

這一術語的計算方法是將壓力和溫度能量除以轉子中的總能量變化。

Pressure and temperature energy together is called enthalpy.

壓力能和溫度能合在一起稱為焓。

The degree of reaction decides what type of steam turbine it is.

反應程度決定了蒸汽輪機的類型。

As the pressure of the steam undergoes a drastic reduction during steam turbine operation, its volume increases proportionally.

在蒸汽輪機運行過程中，蒸汽壓力會急劇下降，其體積也會相應增加。

To accommodate such an expanded steam, we have to increase the flow area.

為了容納這種擴大的蒸汽，我們必須增加流通面積。

Otherwise, the flow speed will become too high.

否則，流速會過高。

This is the reason why the steam turbine blades are too long towards the outlet.

這就是蒸汽輪機葉片向出口方向過長的原因。

You can see how long the last stage turbine blades are compared to the first stage blades.

您可以看到最後一級渦輪葉片與第一級葉片相比有多長。

The tips of such long blades will have very high velocity compared to the root.

與根部相比，這種長葉片的尖端速度非常高。

A twist is given to it so that all blade cross-sections will remain at an optimum angle of attack.

對其進行扭曲，使所有葉片橫截面都保持在最佳攻角。

This kind of large turbine uses two such symmetrical units.

這種大型渦輪機使用兩個這樣的對稱單元。

You can see how the steam is equally divided between these units.

您可以看到蒸汽是如何在這些單元之間平均分配的。

High-capacity power plants use different stages of steam turbines, such as high-pressure turbine, intermediate pressure turbine, and low-pressure turbines.

大容量發電廠使用不同級別的蒸汽輪機，如高壓汽輪機、中壓汽輪機和低壓汽輪機。

All these units are attached to a single rotating shaft.

所有這些裝置都連接在一個旋轉軸上。

The shaft in turn is connected to a generator.

軸又與發電機相連。

The reason for such different stages is quite interesting.

造成這種不同階段的原因非常有趣。

With greater steam temperature comes greater power plant efficiency.

蒸汽溫度越高，發電廠的效率就越高。

This is according to the second law of thermodynamics.

這符合熱力學第二定律。

But we cannot have temperature greater than 600 degrees Celsius since the turbine blade material will not withstand temperature more than that.

但我們不能讓溫度超過 600 攝氏度，因為渦輪葉片材料無法承受超過這個溫度。

Temperature of the steam decreases as it flows along the rows of the blade.

蒸汽在葉片上流動時溫度會降低。

Consequently, a great way to increase power plant efficiency is to add more heat after the first stage.

是以，提高發電廠效率的一個好辦法就是在第一階段之後增加熱量。

So after the first stage, the steam is bypassed to the boiler and more heat is added.

是以，在第一階段之後，蒸汽會被旁路輸送到鍋爐，並增加熱量。

This is known as reheating.

這就是所謂的再加熱。

This will increase the steam temperature again, leading to higher power plant efficiency and output.

這將再次提高蒸汽溫度，從而提高發電廠的效率和產量。

One challenging problem in power plant operation is to keep the speed of the steam turbine constant.

發電廠運行中的一個難題是保持蒸汽輪機的轉速恆定。

This is important since frequency of the electricity produced is directly proportional to the generator speed.

這一點非常重要，因為發電頻率與發電機轉速成正比。

However, depending on the load or power demand, the steam turbine speed will vary.

然而，根據負荷或電力需求的不同，蒸汽輪機的轉速也會不同。

To keep the steam turbine speed constant, a steam flow governing mechanism is used.

為了保持蒸汽輪機轉速恆定，採用了蒸汽流量調節機制。

If the steam turbine rotates at a higher speed, the control valve will automatically reduce the steam flow rate to the turbine until the speed becomes normal.

如果汽輪機轉速較高，控制閥會自動降低汽輪機的蒸汽流量，直到轉速恢復正常。

If the turbine rotates at a low speed, the inverse will be done.

如果渦輪機低速旋轉，則反之。

In this way, the balance of power demand and power supply will be perfectly synchronized.

這樣，電力需求和電力供應的平衡將完全同步。

To learn more about degree of reaction and its implications, please check the next video.

要了解有關反應程度及其影響的更多資訊，請觀看下一段視頻。

Please help us at patreon.com so that we can add one more member to the team and we will be able to release two educational videos per month.

請在 patreon.com 上為我們提供幫助，這樣我們就能為團隊增加一名成員，每月就能發佈兩部教育視頻。

Thank you!

謝謝！