Hi, everyone, and welcome to this new class in engine propulsion and specifically the design of compressors.
OK, so first thing we need to know is that compressors are used in all cases as as a noun, as the
same name.
OK, introduces to actually compress the flow and this means increasing the pressure of the flow.
Now, this is the first stage that we encounter after the inlet, OK?
And the idea is to get the flow to very high pressure state.
Now, mechanical work on the flow results in the increase of pressure.
So the idea is that the compressor is actually moving at very high speeds and this high speeds allow
the flow or force the flow OK to go from a low pressure state to a higher pressure state throughout
all of these stages.
OK, so imagine the flow is coming this way.
And actually, the flow is started is rotating this way and the pressure will increase due to the conversion
from the velocity through pressure due to the geometry of these several parts of the compress.
OK, so that's the definition by itself of how velocity is converted into pressure comes from binaural,
is the question.
OK, and it's just related to the fact that the compressor is rotating and the compressor therefore
has an internal energy, has a very, very high energy which is converted or is given or provided to
the flow and the flow becomes therefore highly pressured.
OK, so we just get the flow and higher pressure due to the movement and velocity of the compressor
itself.
Now, mechanical work, OK?
The rotation of the compressor, as we mentioned before, I think is actually the result of the rotation
of the turbine, which is located on the back.
And because the turbine is moving, we actually have the compressor moving.
And the fact that the compressor is moving actually allows for the fluid to be compressed.
Right.
OK.
So there are several types of compressor's, and mainly we will discuss actual compresses and centrifugal
compressors, so the idea for actual compresses is that the flow will go parallel to the rotation axis.
So you can imagine that flow is actually the rotating, rotating axis would be the center right.
This is over here because it is the decompresses rotating in regards to this axis and the flow will
therefore go parallel to the axis throughout the compressor.
Now, this is this kind of compresses.
The actual compressors are actually very common in modern Turkish jets and tuber funds.
OK, also to turbo propellers, because there are a very effective way to increasing a lot the pressure
of the of the fluid.
OK, but each row, OK, we will actually be able to provide something like one point fifteen to one
point six times the increase of pressure.
OK, so this means that the pressure over here will be actually one point five times, for instance,
the pressure over here.
OK, so multiply this by all the stages and you have a pretty decent increase of the pressure.
Right?
We can actually link several stages, in fact, a lot of stages.
And there are some new engines, which I think they are up to 40 times.
OK, so there in general terms, the pressure on them on the last one is actually 40 times bigger than
the pressure at the beginning, which is very high rate for pressure.
OK, as we mentioned before, the airflow goes in this direction.
What we have is a rotating rotor row, OK?
And this is actually translated into pressure by using a stationary vein like this.
OK, which will you can see that the airflow is forced to rotate and then it is forced to maintain some
kind of steady direction and then it is rotated again.
OK, and this is continuous.
And you can do this, as we mentioned, for several stages.
And in the end, we get very high pressure fluid.
OK, apart from the actual compressors, which are the most common, I would say, in modern engines
and specifically in commercial and commercial engines, we also have centuries of centrifugal compressors.
Which, in fact, the flow, instead of going parallel to the axis, right, it will actually move centrifugal.
So it starts pretty close to the center of rotation.
And due to the rotation of the of the compress, also, it will kind of move to the side and this will
give an increase of pressure.
Right.
So it's also interesting to use centrifugal compresses.
However, the main disadvantage is that due to the geometry, you can imagine that you can just use
only one, OK?
And using one, you may get a four times increase of pressure, but you can't get something like 40
times the amount of increase of pressure.
OK, so this is the main distinctive fact between axial compresses and centrifugal compresses, centrifugal
compress that you may find them in invalid or relatively small aircraft which don't demand that much
compression.
OK, or you can also find it in RC radio controlled aircraft.
OK, on and other kind of engines, but at least not for now.
It's not that common.
So commonly right now we have actual compressors.
OK, so as we mentioned before, actual compressors, what they do is rotating airfoil, OK, which
will basically create difference in pressure, the same as the wing similarly to the wing.
OK, but each stage will will be able to actually increase the pressure a bit and therefore the pressure
will be very much increased.
The fluid is parallel to the axis rotation.
There's a continuous flow of a compressed gas.
OK, so the gases at each stage, it is compressed a bit more and in general terms it has high efficiency,
OK, and large mass flows.
So it can cover a lot of mass flow in just one one road like this.
OK, and different stages.
You can just have a lot of pressure, an increase of pressure, which is very large and also for large
mass flows.
In addition to that, as we mentioned before, we have several rows of airfoils.
OK, and this is also combined to the fact that we have several, you know, compressor's lines of compressors.
So each row, each circle over this one is actually composed by many airfoils.
And this airfoils actually creates some difference in pressure, as we mentioned.
And because we have a lot, we are able to gather a lot of our high mass flow and we are able to pressurize
these large mass flow throughout the flight of an aircraft.
OK, and in centrifugal compresses, as we mentioned before, all we have is a rotating compressor,
again, enters in the axis of rotation, OK, or very close to the axis of rotation, but has a big
radial component when exiting the compressor.
So basically, it will go in this direction and then it will end up.
So it will end up going in this direction almost.
OK, so especially useful for high volumes, but little pressure, little pressure compression.
So it is also useful for large muscles even more.
OK, but the pressure given, as we saw before, is like four times and not 40 times.
And this kind of compressors are actually very common in other industries.
So specifically in for industrial purposes, a lot of compressors are based on this kind of geometry,
which is it's interesting because it's just simpler to design, it's simpler to maintain in general
terms.
OK, and it can be useful if you need just four times the amount of pressure, which is mostly, you
know, enough for a lot of industrial purposes.
But in the case of aircraft, we just need a very high compression in order to provide the maximum thrust
possible.
OK.
So this would be all we can go now to the next class.