S1E6 – Nuclear Power Plants Essentials – Turbine and Generator Transcript

This is a transcript of the video S1E6 – Nuclear Power Plants Essentials – Turbine and Generator

G’day and welcome back to the Engineering All Sorts Video Courses – professional development for teachers, helping you to Engineer your Expertise. My name is Daniel, and I’m your navigator of all things Engineering. I’m also the founder of Engineering All Sorts, where we’re all about Engineering for Educators – stem education to help you to be confident in the details – over at engineeringallsorts.com.au.

In this video we’ll be looking at the building in the nuclear power plant, which houses the turbine and generator. This is where the hot steam gets turned into electricity to be supplied out to the electricity network. We’ll also look at some of the engineering considerations to make the system work efficiently.

At the end of this video you’ll be able to:

Identify the different components of a steam turbine in form and function
Describe the flow and conversion of energy through a steam turbine and generator
Identify the key phenomenon exploited in a steam turbine to generate rotational energy
Describe a typical layout of multistage steam turbines used in thermal power plants
Cite and quantify the key operating parameters of a steam turbine, such as operating temperature and pressure
Contrast key considerations in the creation and operation of a nuclear power plant, such as efficiency and physics

For the full list of learning outcomes, transcripts and worksheets for this series, check out the downloads section of the series at engineeringallsorts.com.au

But our turbine is running at full speed, so, let’s take it apart!

So here we have the key components of a single turbine, and below we have a multi-stage turbine, which we will get to later

This housing around the outside is there to hold all the steam inside, and has an inlet for the hot steam, and an outlet for the cool steam. There is a shaft out the back that is connected to the generator, which spins to create electricity. Inside the turbine are blades, some of which are fixed to the housing and don’t move, and the rest are fixed to the shaft and spin with it.

The turbine is used to convert the high-pressure steam coming from the reactor into mechanical energy, kind of like a pinwheel. This is a single stage turbine to explain the concept, but we can have multiple stages for greater efficiency. This one is one sided, but sometimes turbines can be two ended in a mirrored fashion, with steam injected in the middle.

The basic concept is that hot steam enters one end and immediately tries to expand, reducing its pressure and temperature, but increasing its speed. During this expansion it must move quickly past the blades, causing them to spin.

The physical phenomenon behind this effect is called Bernoulli’s principle, and basically means that if a fluid increases in speed, its pressure drops. It works both ways, so if the pressure is allowed to drop by allowing it to expand, it’s going to speed up.

The first set of blades are actually nozzles to give the steam an initial speed increase. From then on, the fixed blades guide the steam so it always flows nicely onto the rotating blades. The rotating blades in turn are shaped nicely so that they direct the steam efficiently down the stream. Both sets of blades increase in size giving the steam a place to expand further as it travels through the turbine.

The actual shape of each blade is unique for each section, and quite complicated. There are some pretty heavy geometry and fluid flow calculations needed to produce these unique shapes. This is done to extract every last bit of energy from the steam and make sure it’s an efficient transformation of heat energy to movement energy.

The shape is so complicated, it’s very hard to get an appreciation of this with a whiteboard and markers. As a break activity, pause this video and see if you can find a good photo or video showing the turbine blades. Start with the keywords “Nuclear Plant Turbine Blades” and see how you go.

Just pause the video to give yourself enough time, and then come back to us when you are done.

How did you go? Did you find a good video or photo showing the blades. If you have a good one, please share the link in the comments below. Did you find one that no-one else has so far?

Last of all the shaft of the turbine is connected to the generator, so all the spin energy can be converted into electricity. A generator works just like an electric motor in reverse – it has magnets and coils of wire on the inside, that generate electricity as the shaft spins moving the magnets and coils past each other.

Turbines can also be stacked with high pressure and low-pressure turbines on the same shaft. This is called a multistage turbine. Steam will first enter the high-pressure turbine, which is sized just right for this level of pressure and speed. Then it heads to the medium pressure turbine, which is again sized just right. Finally, the low pressure steam will head to the large low pressure turbine, to extract the final amount of energy from it, before leaving as cool steam. All these turbines are connected to the same shaft, and hence add mechanical energy to the shaft each time.

In this video we’ve covered the basic concept of turning hot expanding steam into mechanical energy in the turbine, and then turning this into electricity in the generator. We had a look at the Bernoulli principle and how this governs the shape of the blades in the turbine. And finally, we looked at how to arrange different sized turbines into a large multi-stage turbine.

Don’t forget you can check out the resources for this series and more professional development for teachers at engineeringallsorts.com.au, including learning outcomes, transcripts and worksheets.

If you haven’t left your comments below from the activity it would be great if you could also share that below, so we can all share our stem education

Thanks for watching and I hope you’re looking forward to the next video, where we look the next major component of the nuclear power plant, the Condenser! I’ll see you there!

This is a transcript of the video S1E6 – Nuclear Power Plants Essentials – Turbine and Generator