Okay, so to look at the air system, what I actually want to do is give you a bit of a case study and an example. Really speaking, if you want to talk about the air system, I suppose we could just say yeah has to get to the combustion chamber because we need the oxygen from the air. And then after that gets burnt and turns into exhaust guests, so that's pretty much it, you need to get the air to the combustion chamber, and that's its job then finished. Let's have a look at a working example though. For this particular 3d model, we're going to have a look at an engine with a turbocharger and turbo charges are quite common on diesel engines. So let me run you through the system quickly.

And then we'll run through it in a bit more detail afterwards. So here is a turbo charger. It's got this snail like shape, come around here and see from this angle. See a very unique shape. It's quite a lot happening. Hear, blue signifies air was sucking air into the turbocharger, because the turbocharger is actually rotating, and I'll explain to you how that works in a moment, we suck the air in through what we call a compressor or compressor wheel, and we compress the air and then we force it around this snail shape called a volute.

So the snail shape is called a volute casing. And what we're actually doing there is we're changing the velocity of the air and converting it to pressure energy. So from kinetic energy to pressure energy, so we've increased the pressure of the air. And I'll explain to you why we do that in a moment as well. Yeah, it comes along down here. It's going to come along here and then we go into an air cooler.

We call the air down slightly. We send it then to the combustion chamber. See From the top comes off goes to air inlet valves they open and the air is forced in because the pressure of the air within the air inlet manifold is higher than in the combustion space. And that's what allows the air to flood in and we get a little bit of valve overlap so something flows out the exhaust gas port, flush the bit of exhaust gas out, and then our system is finished. to completely understand the model though, let's follow the exhaust gas system. So we have the two exhaust gas valves coming out here, cause gas comes along and then rather bizarrely come along they come down here and the exhaust gas connects on to the turbocharger.

So is the exhaust gas manifold, and he joins onto the turbocharger goes around and then exits out of the turbocharger. turbine. So that's quite interesting. Why would we do that? Well, let's have a look at the system in greater detail. When the exhaust gas comes out, it's going to pass over this turbine, and it's going to cause the turbine to rotate.

When the turbine rotates, it's actually on a common shaft. So let's come along here you can see it's on the same line. As the compressor we'll be coming along, the shaft runs through the middle. So when the turbine rotates, the compressor wheel rotates. That means the more the turbine rotates, the more the compressive wheel rotates. Imagine you had two wheels connected on a common shaft.

Now you spin one wheel, the other wheel is going to spin as well. And that's exactly what's happening here. So we're drawing more arion because the turbine is going faster. we compress the air and when we compress it, the temperature increases. Remember we said earlier if you compress the gas, the temperature increases as does the pressure. Because we increased the temperature, we take the air and we call it down, we call it down because the more we call it down, the more air we can get into the combustion space, which means we have more oxygen available for combustion.

That's the purpose in this whole turbocharger setup, we want to compress the air so we can get more of it into the combustion space. And we want to cool the air once again so we can get more of it into the combustion space, the air comes out and then it goes through the combustion space. And after that, we get the exhaust gas out. See if we can line this up better. exhaust gas comes out and goes back to the turbocharger. Now if you've ever heard of a concept called turbo lag, the reason we have turbo lag is because it takes a while to get more air to the engine.

And then it takes a while to get more hot exhaust gas to the turbine. turbocharged engines take a while typically a second or two to really get into motion and to get the turbine rotating very quickly. And until that turbine is rotating very quickly, we can't suck more air into the compressor wheel, which means we don't have the oxygen available in order to release more power. So that's turbo lag. The other thing that you're going to see on all engines normally is an air filter. Filters are a big part of engineering.

You install them because you want to remove particles from a system or prevent them entering a system in the first place. Now we don't want to suck just normal ambient air into our engine. There might be bits of dust floating around there might be bits of sawdust. Who knows? Imagine you drove past a wood chippings factory or some other sort of factory All of that dust in the air will get sucked into your engine unless you have a filter. If you have a filter, you'd install it shortly before the turbocharger.

And this means that as you draw air into the system, it's going to be filtered and we end up with clean air going into the engine. If the engine doesn't have a turbocharger, then you'll install the air filter simply on the main air inlet. And you have to change this filter periodically the same as with a lube oil filter, which is a lubrication or filter and a fuel filter. So filters are very important if you want to own and operate your engine for a very long period of time. Now I was going to do a separate video to the exhaust gas system but I don't think that's really required. The exhaust gas system will usually be at least a medium sized engines simply an exhaust gas system like that shown especially for medium sized diesels and it will go to the turbo charger and then It passes through some sort of noise reduction apparatus or component, sometimes called a silencer or a muffler.

And this means that we're not creating a lot of noise with our exhaust gas system. When it comes out of the exhaust gas pipe on engines that don't have a turbocharger then you can discharge the exhaust gas directly to atmosphere. important to realize though, that the larger the engineers, the more complicated the exhaust gas system will become. If you have an exhaust gas system with a very large diesel engine, exhaust gas may have to be cleaned before it is discharged to atmosphere. That's just modern common practice. You can't just dump exhaust gas into the atmosphere like we used to do 100 years ago.

So in order to comply with environmental pollution, legislation and laws, you'll sometimes have to clean the exhaust gas which means taking the burnt carbon out of the air for example, before you discharge it to atmosphere, but anyway I hope you now understand how the system works and some of the components you're likely to encounter. And I will also understand exactly how the exhaust gas system works. They're relatively simple systems. But as with many things in engineering, the bigger the system becomes, the more complicated it becomes. And the more complicated all the components become. So we've covered four systems.

Let's go and have a look now at the cooling water system.