Hi, everyone, and welcome to this new class in engine propulsion and specifically the design of turbines
and the knothole.
So let's begin by doing a little overview of what the turbine does, so turbines, what they do is decrease
the pressure.
OK, so expand the flow, which means the same, decreasing the pressure in order to accelerate it,
to accelerate the flow to higher velocities.
So the turbine converts basically convert pressure to velocity using the equation.
You can see that the pressure is always related to velocity.
And if we have high pressure, it means low velocity and low pressure.
It means high velocity.
So a way to increase the velocity of rejection of our fluid, what we need to do is decrease the pressure.
OK, so the flow going through the turbine has also a high temperature.
And this is due to the reaction in the combustion chamber, which has taken part between the compression
part, the compression zone and the turbine.
So when the flow arrives to the turbine, it is actually high temperature due to the combustion chamber
and high pressure due to the compressor.
Right.
It's also interesting to note that one of the main
objectives of the turbine is not only to accelerate the flow, but actually to provide rotation through
the shaft to the compressor.
And by providing this rotation to the compressor, the compressor will be able to pressurize the fluid
and therefore reacting correctly in the combustion chamber and optimizing the complete engine cycle.
Now, an overview of the nozzles is pretty straightforward, the idea of a nozzle is that the flow is
furthermore accelerated.
It's not only accelerated due to the turbine, but also accelerated a bit more due to simple geometry,
OK, by using a conversion nozzle in case of a supersonic flight.
So you can see that this is just a graph that I found is quite intuitive.
Do you have a velocity going, a mass flow going in this at this velocity?
OK, and due to the conservation of the mass flow, we will have higher velocities just because the
the total area is decreased.
So we will have an increase of the velocity due to Gell-Mann geometric constraints, that's all.
So you can see a bit of the of the nozzle.
It's it doesn't have the ideas that you cannot do it too much because of the properties, the energy
properties and kinetic properties of the gas.
But you can actually provide a bit more velocity due to converting not OK as before as happened in the
same case as the nozzle.
There's no work, there's no difference of pressure on the fluid due to the nozzle.
So it is simply a way to accelerate the flow with no different pressure.
OK, one on one topic that I wanted to discuss also on the afterburners with some of you may know from
aircraft specifically, mostly from military aircraft, which is kind of, you know, interesting to
note that you can actually provide an additional propellant.
OK, so an additional burning part of you know, but you can actually provide more energy to the fluid
by burning the fluid and the nozzle.
And this is actually known as afterburner.
So my definition would be that some aircraft introduce additional propellants, OK, so that the flow
at the nozzle is burned again.
And this what actually does, as you can see, is create this kind of interesting, you know, fact
that some of the fluid is seen as if it were burned or after burned.
And it's well, you know, you've probably seen it for supersonic flight.
And this kind of afterburners are quite unusual in supersonic aircraft.
And what they do is provide additional thrust.
However, the main drawback is fuel efficiency, because you're basically burning more fuel in order
to get a bit more thrust.
In general terms, you won't find this in commercial aircraft.
It could be done.
But it's not efficient.
It's not fuel efficient.
And so this is not the case unless we need extra thrust or we need very high thrust, which is what
usually happens for supersonic aircraft.
OK, so I think we can go to the next topic.