Hi, everyone, and welcome to this new class in engine propulsion, specifically, we will discuss
with greater detail to our budgets and the funds.
So we discussed in previous classes the difference or the main differences between turbo jet to Aberfan
and turbo proponent.
So turbo jets.
Basically, they get some kind of air on the exterior and they get it from the exterior, they compress
it after that.
The temperature is also increased on the combustion chamber.
Then all of this energy is transformed in the turbine to velocity.
And finally, with a nozzle, we get a higher velocity, OK, which compared to the initial velocity,
will give a certain amount of thrust to the engine.
This is a main character, but it mainly works turbo fan.
The difference of the term of the term budget is that instead of having only one flow, we will have
to kind of float.
First, we will have something very similar to that budget in the interior.
But we also have some kind of low on the exterior like this, which will actually be named as called
flow.
OK, so this will be hot flow because the exhaust is at hot temperature, whereas this will be named
the contraflow.
The idea is that we have greater efficiency at supersonic flight due to a fund.
And finally, we have a turbo propeller, which instead of generating thrust due to the difference in
velocity on the exhaust and the inlet, we will actually have the creation of thrust due to the movement
of the compressor and turbine and therefore the shaft, and that, given a gearbox will be transformed
into propellant, kinetic energy.
So this means the velocity, a given specific velocity for the propeller will actually be able to generate
some thrust.
Now.
To get more into detail and to just, you know, get into all the topics and for you to get to know
exactly how this work, we will make a bit of a greater discussion.
OK, some more detailed discussion.
So, as I mentioned, jet engines, turbo jets, work based only on one floor.
And this flow is initially called at low pressure.
Now, pressure will be increased at the compressor in several stages, as we saw in the part of compressor,
where we will have is an actual compressor with different stages, and this different stages will actually
improve or increase the pressure part step.
All right.
So in the combustion chamber, we will get actually a very high pressure fluid.
The combustion chamber will hit the flow to a high temperature.
So not only will we have high pressure fluid, but actually a very high temperature and high pressure,
high pressure fluid, then the turbine over here will accelerate the flow by expanding it.
And this means that the turbine will actually decrease the pressure and therefore accelerate the flow.
And we will have the flow at higher acceleration at higher velocity.
OK, and at high temperature.
So the flow you can imagine at this point as
energetically speaking, has great conditions, OK, in this case, it will have the conditions of the
flow will be greater than those in the initial conditions.
So the velocity will actually be very much higher than the velocity in the Internet.
And this would provide the thrust.
Also, it's interesting to note to remember that the compressor is moved by the turbine.
So when the turbine starts to operate, it will translate the movement with the shaft to the compressor
and the compressor will start compressing or pressurizing the flow to the combustion chamber in order
to optimize the whole engine cycle.
Finally, flow is further accelerated by the nozzle due to the geometric conditions of the nozzle.
And we actually can use also an additional afterburner, right, as we discussed in previous classes.
So the idea is that the final flow is hot.
It will have quite a high temperature and will become also low pressure.
So this flow is basically optimized in order to be at high velocity.
Now, turbo fans and the main difference between Turbo fan and budget is that we have to fluffs.
Named hot and cold, the hot flow is basically the same or very similar or the configuration of the
internal part of the engine is very similar to the turbo charged.
However, in this case, we have a high pressure turbine.
OK, this one over here, a high pressure compressor, a low pressure compressor and a low pressure
turbine.
OK, and you may ask why.
Well, the idea is that high pressure turbine will actually move the high pressure compressor.
So, you know that the turbine will actually move.
And because of the movement of the turbine, we actually are able to move the compressor.
So high pressure turbine will move high pressure compressor and apart from that, the low pressure turbine.
OK, so just as a reminder, you know, that pressure at this point is relatively low.
Then it increases and it continues to increase.
So this is why this is the high pressure compressor and this is why this is the low pressure compressor,
OK, because of the flow at this point is at lower pressure conditions.
Now, as I was mentioning, that low pressure turbine, so this part of the hair, the exterior part
will actually move the low pressure compressor and also the fun.
Now, what's interesting of this and the main difference between the turbine and a turbine is that we
have the separation of high pressure elements and low pressure elements.
And this is interesting because because we have a low pressure turbine, we are able to move also the
fan and this fan.
What it will do is create or induce to the flow to the cold flow on the exterior, some kinetic energy
due to the movement of the fan.
And this will be transferred in the end as an increase of the velocity.
Not a lot of increase, but just substantial, a bit of increase.
And as you know, the thrust is just the product of the mass flow times, the velocity of that difference
of velocity between the, you know, the nozzle and the inlet.
So if we have a lot of mass around the cold.
OK, so a lot of cold mass, a lot of cold flow, which means a lot of mass flow, but with little difference
in velocity.
That's enough to cover a lot of thrust.
OK, just because we have a lot of the mass flow.
So even if the difference in velocity is not that high, the fact that we moving with this compressor,
we are able to move all of this flow will actually make the engine a bit more efficient.
And this is just the idea of the Turbo fan.
So Turbo fans are a bit more efficient in terms of supersonic flight because we also count with a fan,
OK, and this fan will generate a bit more velocity to the mass flow.
And because there's a lot of mass flow, this will be converted to an extra part of the thrust.
OK, so overall, trust can be higher due to high Mazzello.
Right.
So combining the hot flow and also the flow, as we mentioned, now efficiencies in this cases in server
funds are higher than turbo jets for supersonic flight.
There's actually a mathematical derivation that at very high hypersonic speeds, actually turbo jets
work better than underfunds.
So this is why you won't see turbo fans for, you know, supersonic aircraft.
It usually is turbo jets because of the efficiencies, OK?
It's simply more efficient in subsonic flight.
And in case of the supersonic flight, turbo charged will be more efficient.
So what else can you have some examples of what turbo jet engines look like?
So I would like you to check and, you know, be able to determine the different elements on this one,
for instance.
This one is this engine.
You can only see the exterior.
So it's not that obvious, the different elements, but you can see all the connections, all the further
the thermodynamic connections on electric connections, OK, that are required in order to fulfill all
of the characteristics that all of the potential OK.
That this engine can get.
So you can see different elements, some refrigerants, you know, just different elements of the off
the engine, which are quite interesting, to be honest, and which can be.
You know, it can be of your interest to determine the different elements, however, in this cause,
I will just focus on the different concepts, OK, that we can see over here.
So, first of all, you see that inlet on this part.
You see the different compressor stages, OK, you all you can also determine that these ones are a
bit different than the following ones.
In fact, you can see that airfoils in these cases are quite large compared to the larger cases.
And this is because the pressure in these and in, you know, in this stage of the aircraft or off the
engine is actually lower than in these cases.
This is high pressure conditions.
So due to the difference in pressure, we will need some corrective action or some other of the airfoils.
OK, that compounds the compressor.
So this is actually quite interesting to note.
All of this will be the first stages.
OK, and you have the inlet, as I mentioned, this is the shaft.
And in this case, you can see that combustion chamber is actually radial is on the outside due to the
fact that the flow will will move in this direction and it will be introduced in this point with the
combustion chamber.
And as you know, the combustion chamber will increase the temperature.
And after that.
You can see that the combustion chamber will move the flow towards the end, towards the turbine, the
turbine will expand the flow, so it will decrease the pressure and therefore create a higher velocity.
Right.
And after that, you just have the exhaust.
You have to not.
All right.
So this would be a typical configuration of a turbine that I wanted you to see.
Real case, OK, so that you can analyze the different elements if you are interested in that.
Now, turbo jet examples are mostly, as I mentioned, supersonic flight.
You can see this one in this case.
You can see it has afterburners.
All right.
With the arm, with, you know, it looks like fire is coming out.
In fact, you can also see that different all of these you can see that there's this continuous kind
of burning.
Can you see that?
That is related to the velocity at which, you know, the speed at which the fluid is coming out from
the from the engine itself.
And you can see that it is supersonic.
The speed of this fluid is supersonic because we have kind of shock waves and this are little shock
waves.
OK, that will appear a different, you know, a different time rates due to the velocity, the velocity
of their engine.
So if you if you see some you know, if you see this kind of element, you can you can determine it
is related to shock waves.
So it actually you can actually determine the velocity at which then the speed at which the velocity,
the speed at which the flow is actually coming out due to analysis of the flow.
All right.
So this is the first example.
This is the Blackbird from NASA.
This is actually this is quite interesting to note.
OK, I like this photograph because you can see that there's also more technology going on in the nozzle.
OK, depending on the amount of of thrust that you need, you can actually close.
I'm not sure if it's very visible, but you can see that this is closer.
OK, this surface is a bit smaller than this one over here.
So you can actually have a difference in in the amount of thrust that one motor or one engine is given
with respect to the other, which may serve for some kind of, you know, mechanics, some kind of rigid
body mechanics that can be useful to orient the spacecraft in one way or another.
OK, and it just means that the nozzle can perform and probably will automatically perform in the best
optimal way.
OK, so you can imagine that there's a lot of computers going on here, OK, in order to optimize how
this is closed, so how the nozzle is actually focusing the fluid going out of the of the aircraft.
OK, so it's quite interesting to note this technology is actually, you know, it is being developed
and it is quite useful, to be honest, in order to optimize the amount of thrust given by an engine.
And this one I like also you can see that I'm not sure if it's very visible, but this is the the main
axis of the of the engine.
And but you can also see that there's a change of the axis on this part of.
It's kind of looking downwards, isn't it?
And this is this is usually known as thruster vectoring.
And what it means is that you can actually point the nozzle to one direction or another in order to
get thrust in one direction or another.
And this can be also used in order to orient your aircraft and in some specific way or not.
So if you need to make a quick rotation of the aircraft, a quick maneuver, you can actually and probably
automatically the the whole computers in the in the aircraft will be capable of orienting the fluid
in one specific direction in order to get an impulse by Newton's third law, by the reaction in the
opposite direction.
So this is how complex some of these engines can actually get.
And this is the technology we actually looking for.
Right.
Also, I wanted to include some Turbay fine examples, so Aberfan, I'm sure you're probably more familiar
with if you are ever flown with an aircraft, with a commercial aircraft, you have almost for sure
seen one of the most fun engines.
OK, you just get to see the exterior.
But this is all the interior.
It's quite interesting to note that this is the fun.
Right.
And you get all these different compressor stages and also, you know, the shaft.
And, yeah, it's very it is difficult to note, but there's a combustion chamber here, OK, due to
the high pressure you get here, the combustion chamber, and then it is expanded with the turbine.
And therefore, you're actually able to transform the low pressure from so, you know, velocity and
actually accelerate the fluid, as we mentioned before, this is quite similar to the turbo jet.
And it is also interesting to note all of this space, OK, all of this part of here which will be covered
afterwards with.
You know, with some kind of mechanical element and what we'll do is actually have a call to flow right
around the engine.
So you have the combination of both.
And this is the idea for that.
This is the dimensions of and I'm not sure which model this is.
I think it's the model for them for the 787.
And this engine is quite efficient.
So you can just see the different elements as we saw the fun in this case.
This is covered, OK?
And this is the exterior.
You can also see all the refrigeration, different elements, key points, electronic connections,
all of that of the of the turbine itself.
And finally, this would be the example of what you would see on a term often you just get to see the
external cover, OK, and the fan usually so are the photo of a fan.
You will see the fan and the cover, that's all.
But you must know that the interior is what we described before.
So the interior of them, of the engine is actually like this.
And one thing to you know, I like this photo because apart from the dimensions, OK, which is quite
interesting to compare with her with a person who was walking about, it's quite interesting to note
that you can determine the flow, OK, where it will go, because there's actually you can see it's
void.
You know, there's no there's no there's no structure in this part.
You can see the fun.
But in this part over here, you can see that the family is actually empty on on on the posterior.
So you get the fan and you get the flow flowing and that's all.
And and also you get caught sight of the hot flow on the middle.
OK, in order to generate the maximum thrust.
So, well, it's a combination of both and it's like a turbo on this part.
And you actually have also the fan and the fan wouldn't move the coal flow on the surroundings.
So this is all right.
If you want to know also this, you may be interested in knowing why this is used.
They usually use this in order to recognize if an engine is working on it.
It's to kind of imagine that you a long distance from an aircraft and you don't know if that aircraft
is moving or not while moving, if the engine is operating.
So you can know easily you can easily know that if the engine is operating just by seeing if this element
in the center is actually moving or not.
And therefore you can see if the engine is operating.
This can be useful for, you know, controller purposes from the tower station or whatever.
OK, so I think this is all as always, if you have any questions, let me know.
And in addition to that, I tried to build a lot of effort into getting the most material, if I would
appreciate it.
If you if you feel like this content is is good and useful for you, I would appreciate it.
Good.
You know, a good review on your part.
And I am willing to to listen to all your petitions, OK?
And I would like to provide the best material for you.
So just let me know if you have any questions.
If you ever have any doubts, let me know and I'll try to look for a solution for that.
OK, so let's go to our next class.