Hello and welcome to this lecture series on
turbomachinery aerodynamics. Today’s
lecture is the first lecture of this forty-odd
lecture series on turbomachinery
aerodynamics, where we are going to cover
various aspects of the aerodynamics
associated with the different types of turbo
machines like axial compressors, axial
turbines, and centrifugal compressors, and
radial turbines.
So, we will, of course, be discussing the
details of the syllabus and the course contained
in in this particular lecture series. My name
is Pradeep and along with me Professor
Baskar Roy; both of us are from the department
of aerospace engineering I.I.T, Bombay.
We shall be taking up this course, which we
shall be covering in about 40 lectures or
so.
So, in today’s lecture, which is basically
an introductory lecture, I shall take you
through
the syllabus, the course contents of this
course as well as the text books or reference
and
additional reading material that we feel could
be appropriate for this course. And
subsequently, we will also quickly go through
the lecture wise schedule of this particular
course, where I shall explain what are the
course contents that we shall be covering
in
each of the next term several lectures.
So, this course on turbomachinery aerodynamics
is a course, which will basically be
looking at the aerodynamics of the flows associated
with turbo machines, the various
types of turbo machines and the theory behind
working of these different types of turbo
machines. So, as I mentioned, there are two
of us who will be handling this course,
Professor Bhaskar Roy and me - Pradeep - both
of us from the Aerospace Engineering
Department I.I.T.,Bombay. And this course
is basically a video course, were we shall
be
taking up all the lecture contents through
video lectures, and also of course, the the
transcript of the lecture material also would
be available on the NP-TEL website.
So, in this particular course on turbomachinery
aerodynamics, as I mentioned, we shall
be covering different aspects associated with
the aerodynamics of many of the
components, which constitute let us say an
aircraft engine. For example, there are
different components, which continental aircraft
engine. Two of the most important
components are the compressors and the turbines.
These are the basic turbo machines,
which constitute a gas turbine engine. Similarly,
of course, turbo machines can be found
in various other applications and the main
intent of this particular course is to introduce
the various concepts, the working principle
and the theory behind many of these turbo
machinery components. And so, let us take
a very quick look at, what are the different
topics that we going to cover in this lecture
series.
So, the course outline is what I will be discussing
in the next few slides. We will, of
course, begin the lecture series with an introduction
to turbo machines, which we will
start in this second half of those lectures,
which Professor Roy will be covering. He will
begin the introduction to various aspects
of turbo machines in this lecture itself.
So,
subsequently we will start our course with
discussion, a detail discussion on axial flow
compressors and fans. We will be discussing,
the Aero-Thermodynamics of flow through
axial flow compressors.
We will also be discussing in detail, the
losses associated with axial flow compressors
stage. And once we have looked at the different
losses and which constitute an axial flow
compressor, we will also look at how we can
estimate these losses and how these losses
affect the performance of an axial flow compressor
stage.
And then the different aspects of the three-dimensional
flow, which constitute an axial
flow compressor stage like secondary flows,
the tip leakage flow and the flow scrubbing,
which are basically some of the laws generating
mechanisms, which are constituents of
an, which are inherent part of an axial flow
compressor machine. We will also be
carrying out certain amount of 3-D flow analysis,
the radial equilibrium and the
associated equation, which constitute the
3-D flow analysis of an axial flow compressor
stage. We will be spending quite some time
in understanding the compressor
characteristic, we will be looking at the
axial flow compressor, the single stage as
well as
the multi stage characteristics of an axial
flow compressor.
This is very important, because the way in
which the compressor performance is
expressed is basically through the compressor
characteristics and it is a very important
ingredient, which is required by an aircraft
engine designer to understand the compressor
characteristic carefully.
We shall be also looking at the certain fundamental
aspects of compressor blade design.
We will begin with 2-D blade designs and Airfoil
Data will subsequently take up, the
axial flow track design and also the characteristics
as I just mentioned. Now, most of the
modern day compressors, in fact many of the
modern day compressors are not
necessarily low speed, there are essentially
at transonic compressor.
So, we it is also important that we understand
the working principle, behind transonic the
high speed compressor or the transonic compressor
stages. So, we will spend some time
in understanding aerodynamics of the transonic
compressor stages. We will also look at
the shock structure associated with a transonic
compressor blade and also the
characteristics of a transonic compressor.
We will then move on to the 3-D blade design
of rotors and stators, because the aspect
of
related to the airfoil data and and all those
things are basically limited to twodimensional
blades, but most of the modern blades are
three-dimensional in nature. So,
we will also look at the 3-D blade design
of both rotors as well as stators. We will
then
spend a substantial amount of time in discussing
about the instabilities of axial
compressors, where different instability mechanisms
of axial flow compressors and it is
necessary that we understand these instabilities
in detail, so, us to enable us to design an
axial compressor, which is more efficient.
So, we will look at the instabilities and
the laws of stability margin, and the associated
problems with laws of stability margin, in
axial compressors. We will also spend time
in
understanding, the noise problems associated
with axial flow compressors and fans.
Because modern day engines are required to
have or to limit noise to certain levels,
which are very stringent, then getting stricter
every year or so, and it is necessary and
most of this the major junk of this noise
is originating from the axial fan and the
compressor.
So, it is necessary that we understand, the
noise generating mechanism of these axial
flow compressors. Now, once we have understood
and covered the axial flow
compressors in detail; we shall then now look
at another component, which is also an
axial flow component, but it is a turbine.
So, we will also look at the design and the
performance characteristics of Axial flow
turbines. So, that would be the second module
of this particular course of Axial flow
turbines. We shall understand, what constitutes
a turbine stage and the turbine 2-D
analysis will look at Work Done and Degree
of Reaction in detail, and then we will
understand, the laws mechanism losses and
the efficiencies of an axial flow turbine.
We
look at the flow passage and the flow track
in multistage turbines, same way as we have
done for axial compressors. Will then look
at, the three different types of or classes
of
turbines: the subsonic, the transonic and
the supersonic turbines.
And in terms of characteristics, how we can
understand and analyze the performance of
axial turbines, in a very similar manner as
we carried out for axial compressors. So,
we
will look at multi-staging of axial turbines,
the exit flow conditions and very important
aspect of turbine flow is the turbine blade
cooling. So, we will spend some time in
understanding the various mechanisms, which
are used for a cooling of turbine blades,
because as we know that a higher turbine inlet
temperature is always desired for better
efficiency and thrust of an aircraft engine
for example.
But it is the material that limits very high
temperatures from being used in axial in in
turbines in general. So, one of the ways or
methods of extending or enabling higher
turbine inlet temperature is to use certain
cooling mechanisms, and so, it is necessary
that
we understand, the various types of turbine
blade cooling mechanisms, which are used.
We will then spend some time on understanding
turbine blade design, and we will start
with airfoil design, and it is profile construction
and so on. And then, we will extend that
theory to 3-D blade design, the same way,
which we carried out for the axial flow
compressors. So, this would complete the second
module of this course, which is an axial
turbines. So, once we have covered the axial
compressor and the axial turbines, we will
then move on move towards, the other components,
the other counter part of these the
the centrifugal compressors and the radial
turbines.
So, the third module that we are going to
cover in this course is on Centrifugal
Compressors. So, in Centrifugal Compressors,
we will start with some fundamentals of
centrifugal compressors and we will basically
be talking about the different components
of centrifugal compressors; the Inlet Duct,
the Impeller and of course the inducer and
related components. We will then understand,
what is meant by Slip factor and its effect
on the performance. We will be discussing
about the Concept of Rothalpy and the Ideal
and real work done. We will also spend some
time discussing about the incidents and the
lag angles, and the different types of diffusers,
which are used in centrifugal
compressors.
And subsequently, we will spend time discussing
about the centrifugal compressors
characteristics, and we will be talking about
the serge margin, which is an important
performance characteristics characteristic
associated with centrifugal compressors. We
will then be discussing about serge and rotating
stall in detail, which we also covered in
terms of the instability mechanisms in axial
compressors. We will also be discussing
about the similar instability mechanisms,
which affect a centrifugal compressor and
then
we will also discuss about the different variants
of centrifugal compressors of modern
day centrifugal compressors. So, this would
complete the third module of this course,
which was on centrifugal compressors.
And the fourth module is on radial turbine.
So, we will begin with some introduction to
radial turbine. Then, we will also talk about
the Thermodynamics and Aerodynamics of
radial turbines and of course, the Radial
Turbine Characteristics; Losses and efficiency;
and Design of radial turbine. So, radial turbine
as you can see will also complete some
elementary aspects of radial turbine.
But, we would probably not be spending too
much time on radial turbine, as compared
let say axial turbine. Primarily, because
of the fact that we would be dealing with
axial
turbines more commonly than radial turbines;
and towards the end of this course, we will
also spend may be a lecture of two on discussion
of on the use of computational fluid
dynamics in turbomachinery design and analysis.
So, this is a computational fluid
dynamics or CFD is increasingly being popularly
used in design, as well as in analysis of
turbomachines, and the computational tools
are getting better day by day, in terms of
their accuracy and ability to accurately predict
the complex three-dimensional flow in
turbo machine. So, we will discuss some of
the aspects associated with the use of CFD
in
modern day turbomachine design and analysis.
So, these are some of the topics or the modules
that we shall we covering in this course
on turbomachinery aerodynamics. As you can
see the discussion is purely on
aerodynamics of these components, we shall
not really be discussing the mechanical
design aspects of turbomachines. So, that
is purely out of scope of this particular
course,
which is also evident from the title of the
course, which is turbo machinery
aerodynamics. So, we will only be discussing
about the aerodynamic aspects of design,
as well as analysis of these components, and
the mechanical aspects of design will not
really be covered in this course.
So, before we move further, it is necessary
that also mention that the that there is a
certain Pre-requisite required for those of
you, who plan to take the take up this course,
because it is dealing with aerodynamics of
turbo machines.
It is necessary that one should have undergone
a full course in aerodynamics, before
attempting to take up this course. So, the
Pre-requisites for this course is essentially
a full
course in Aerodynamics, and therefore, it
is expected that students would be conversant
with the various fundamental aerodynamic theories,
many obviously or directly used in
this course. And it is also desirable that
you have undergone some course in the
fundamentals of thermodynamics, because that
also would be part of many of the
discussions that we are going to take up in
this particular course.
So, we will be assume that you have already
undergone a course in aerodynamics, and
you also have some fundamental understanding
of thermodynamics, because these are
going to be used very frequently throughout
this course. Now, let us now take a look at
what are the text books that we recommend,
that you read while taking up this course,
you will also suggest some additional reading
material, which you can take up as in
when you required the need for that.
So, Text book and References, because we will
begin with compressor. The different
types of compressors, one of the very fundamental
text books, which deal with
Compressor Aerodynamics in great detail is
by Nicholas Cumpsty, on Compressor
Aerodynamics published in the year 2004 by
Kreiger Publications, USA, this another
book on Axial Flow Compressor, which is basically
kind of a report published by
NASA, and it is by Johnson I.A., and Bullock.
The report number is NASA-SP-36 on
Axial Flow Compressors; this was released
in the year 2002, and similarly for turbines
we have a NASA report NASA-SP-290 on axial
flow turbines; this was also released in
the year 2002. There are two classical text
books, if I am I call this on turbo machines
Axial Flow Compressors by J H Horlock, this
was published as you can see way back in
1958, but it is still considered as a very
good book dealing with the fundamental
aerodynamics of compressors.
Another book which was published by the same
author by J H Horlock is on axial flow
turbines, published in the year 1965. A text
book, which deals with both the aspects of
Fluid Mechanics, as well as the Heat Transfer
in turbomachineries was published in the
year 1995 by B Lakshminarayana, and this is
also considered as a very good text book,
which can give you a great in depth analyses
of many of the fundamentals of turbo
machines in terms of both the aerodynamics
as well as the heat transfer, and also this
book will also give you some idea about, how
to use computational fluid dynamics or
numerical techniques, how they can be used
in analysis design an analysis of turbo
machines.
So, Lakshminarayana’s book is also highly
recommended in terms of not only as a text
book for covering fundamental aspects of aerodynamics
of flow, as well as heat
transferred, but also for understanding of
the use of numerical techniques in design
and
analysis of turbo machines. So, these are
some of their fundamental text books that
we
would recommend that you should try and read
as you undergo this course.
Besides, this there are a few additional text
books that we might suggest two of them are
listed here. One of the books is by Gordon
Oates; it is on Aerothermodynamics of
Aircraft Engine Components and it is AIAA
series publication; which was published, in
the year 1985. Another series of, another
text book on aerodynamics of gas turbine
engines was published by the international
gas turbine institute, which is affiliated
to the
American Society of Mechanical Engineers (ASME).
The design of Gas Turbine Engine
Thermodynamics and Aerodynamics, basically
chapters 8 and 10, which are of interest
to us; this was published in the year 2005
by ASME and of it also comes with few video
lectures, on covering various aspects of these
courses.
So, we recommend and suggest that some of
these text books, obviously are would be of
great interest to you can also go through
some of the advance text books, specially
by
Lakshminarayana of some of these additional
text books that we have suggested would
be of interest to you as you as undergo this
course. So, you may want to go through these
courses, these text books as you undergo this
course and various chapter of this particular
course.
So, what I am going to do now is to take you
through the lecture wise schedule of this
course and what is it that we shall be covering
in each of these of lectures, during this
entire lectures series.
So, let me go through the lecture schedule,
we will start with lecture number 1, which
is
basically today’s lecture, primarily to
do with introduction: Syllabus, References
and this
schedule. So, I am as I mention professor
Roy is going to take up some of the
fundamental and introduction to turbomachineries.
The second lecture is on is where we will
start with the Axial flow compressors and
Fans. The first of that lecture would be on
Introduction to compressor
aerothermodynamics, which will be covered
by me. The third lecture would be on the
two-dimensional analysis of axial flow compressors
and fan basically the cascade
aerodynamics, which will also be covered by
me. Next lecture would be on the loss
estimation, 2-D Losses in axial flow compressor
stage - the primary losses and what are
the loss mechanisms, which will again be covered
by me.
So, the next lecture we shall be taking up
a tutorial, we will solve certain examples,
and
also I shall give you some tutorial problems,
which you can solve later on. The next
lecture would be to do with the three- dimensional
flows. We deal with 3-D flow in
Blade passages, Secondary flows and Tip leakages,
blade Scrubbing and so on.
So, Professor Roy is going to take up this
course of this particular lecture. The next
lecture, lecture number 7 would be 3-D flow
analysis-the Radial Equilibrium concept,
which will be covered by Professor Roy, and
then we will take up the Classical blade
design laws-the free vortex and other Laws,
which are used in design of axial flow
machines; professor Roy is going to again
take up this particular lecture. So, end of
this
the next lecture, lecture number 9 would be
devoted to a tutorial. The second tutorial
of
this course solid examples and tutorial problems,
and we will also have a quiz, during
this particular lecture that would be lecture
number 9.
And then on lecture 10, we have the radial
equilibrium equation, the full radial
equilibrium equation and the streamline curvature
theory, which will be covered by
Professor Roy. Lecture 11, which I shall be
handling would be on axial compressor
characteristics-Single stage as well as multi-stage
and multi-spool characteristics. So,
basically lecture 11 is on compressor characteristics
of both single as well as multi-stage
types.
Lecture 12 will be on Instability in Axial
Compressors and whatever the different types
of distortions, which can effect and compressor
performances. Lecture 13 would be the
discussion on Inlet Distortion and Rotating
Stall and what is the effect of distortion
on
Rotating Stall. Lecture 14, which will be
covered by Professor Roy would on
Compressors Instability and control mechanisms.
Lecture 15 would be Design of
compressor blades, starting with Airfoil Design
and then we also be covering subsonic,
transonic and supersonic profiles, because
a blades as you will see would be quite
different as it goes it from subsonic to supersonic.
Lecture number 16 is on Transonic Compressors
and Shock Structure models and also
some characteristics of transonic compressors.
Lecture 17 would be Axial Flow Track
Design; Inter-spool duct; 3-D Blade shapes
of Rotors as well as Stators. Lecture 18 will
devote to Noise problem in Axial Compressors
and Fan. The origin of noise and what is
it that probably could be done prevent or
control the levels of noise.
And then after we have covered the axial compressor
in detail, we will move onto the
axial flow turbines, as we have discuss during
the syllabus. The second module is the
turbine, axial flow turbine.
Axial flow turbine: the Introduction to turbine
aerothermodynamics will be covered by
Professor Roy and the 2-D analysis of turbine
blades, the cascade analysis of axial flow
turbines to be covered by me. And then lecture
number 21 would be axial turbines, the
the Work Done, Degree of Reaction, Losses
and Efficiency. Subsequently, we will take
up axial flow turbine in terms of the Blade
and the Axial Flow Passages and the Exit
flow matching with the nozzle.
Lecture 23 would be a quiz, a well a tutorial
on axial flow turbines, which again will be
covered by me. Lecture number 24 would be
Multi-staging and Multi-spooling of axial
turbines, to be covered by Professor Roy.
Lecture 25 is 3-D flow in axial turbines:
the 3D flow theories-the Free vortex theories
etcetera and Lecture 26 would be the forth
tutorial, which would cover the 3-D flows
in Axial low Turbines.
And then we will spend some time in understanding
the cooling or the effect of blade
cooling on performances. We will understand,
what are different types of blade cooling
techniques? The fundamentals of heat transfer
and blade cooling and which will continue
on the next lecture, that is lecture 28, we
will continue with Blade Cooling Technologies.
Lecture number 29 is Turbine Blade Design
- Turbine Profiles: Airfoil Data, profile
construction etcetera, which will be covered
by Professor Roy. Lecture 30 is Turbine
Blade Design - 3-D blade shapes. And then
from lecture 31 to 32, we shall be taking
up
centrifugal compressors in detail. Lecture
number 33 is the fifth tutorial, which will
be
on centrifugal compressor, which again I shall
be covering.
We shall also have some lectures devoted towards
to Design of Centrifugal
Compressors: the impeller Design. And lecture
35, we will take up the other components
of Centrifugal Compressors, the subsonic and
supersonic, vaned diffusers, vaneless
volutes etcetera. Radial turbine, we shall
start in lecture number 36, Thermodynamics
and Aerodynamics of radial turbines followed
by radial turbine characteristics in lecture
37. Lecture 38 is the sixth tutorial on radial
turbines as well as a Quiz. Lecture 39 is
on
design of radial turbines.
And the next few lectures, as I mentioned,
we also spend some time to look at the use
of
a computational tools, numerical techniques
in the design and rancidez of axial flow well
turbo machines. So, we will spend a few lectures
on understanding, the basics of the
numerical tools.
So, we will start with use of CFD for turbomachinery
is basically Computer aided blade
profiles and cascade analysis. We will then
look at in lecture 41 Grid generation,
Periodicity and Boundary Conditions as well
as the Flow Analysis. Lecture 42 would be
3-D blade generation and analysis using CFD.
And the last lecture of those lecture series
would be the Flow Track and inter-spool duct
analysis and design using CFD.
So, as you see the last few lectures, we have
specifically set aside to introduce the
concept of the, use of the numerical techniques
in turbomachinery design and analysis.
Because this is coming increasingly important
in modern day, design of turbo machines.
So, as you have seen about 43 are lectures
in this lecture series, during which we shall
be
covering the fundamental aspects of the aerodynamic
and of turbomachines. The
different types of turbo machines, starting
with axial flow compressors and fans, axial
flow turbines, the centrifugal compressors
and the radial turbines.
So, these the lecture wise schedule is what
I had discussed in the last a few minutes
and
in next part of this today’s lecture, which
is going to be taken up by Professor Roy.
He shall give, an introduction, A Brief Introduction
to the different concepts of the the
types of Compressors and Turbine, basically,
an introduction to this whole course itself.
So, this second half of this lecture is going
to be taken up by Professor Roy.
You are just been given a full details by
Professor Pradeep, about the course content
and
the course coverage and all the details about
how the course is going to be taken through
the various lectures over this lecture series.
He is also given you details about some of
the books, very good books that you may have
to acquire or you may have to ask your
college library to acquire, because most of
these books are published to abroad and hence
you may have to take a little trouble to acquire
those books, but those books are indeed a
very useful for this course.
So, if you or your college library can part
these books, it will be really useful book
addition to this course coverage. What I will
do is, I will look at the basic elements that
we are going to cover over this lecture series.
I am trying to give you, a very brief sketch
or what these elements are as for accept (Audio
Not Clear). We will be looking at
Compressors and Turbines, as essentially that
are turbomachinery elements in this
course. One may think of other turbo machineries
like winter binds, but they those are
not part of this course. We are looking at
the elements that he is talked about, essentially
the elements that are part of aircraft propulsion
system or aircraft engines.
So, those are they elements that we would
be looking at more closely an in in great
detail
in this a lecture series. So, i will we quickly
look at these elements of the compressors
and the turbines, to give you a very quick
idea about, what we are really up to in this
course. The first question is why do you need
compressors and turbines in an aircraft
engine or in an engine that produces thrust
for aircraft to fly?
Now, this is the question that actually is
answered, a little more precisely with a little
help from thermodynamics. So, we will have
a very quick peek at, what the
thermodynamics indeed give us to begin with
from which we have taken off to create
these complex machineries called compressors
and turbines. So, if you look at where the
engine is come from understanding that an
aircraft engine is fundamentally, a heat
engine and this heat engine finally helps
us produces thrust.
So, let us take a look at the basis of this
heat engine, very quickly. If you look at
this
diagram is basically a temperature entropy
diagram or a TS diagram. As it is popularly
known and this TS diagram essentially encapsulates
or captures, what is happening in an
engine. Artificially in an engine, the flow
goes through a process of a compression from
1 to 2 and then it goes through a processor
combustion in which energy is a put inside
the engine by burning of the fuel and having
put in this energy; this energy highly
energized flow is then used in an expansion
process partly to run a turbine, which in
turn
is essentially runs the compressor, and then
partly to take out the flow through the nozzle
or a jet nozzle to create jet thrust.
Now, the question is what are the compressors
and then the turbines indeed doing here?
If you look at this diagram, you will see
that if you have a compression. The
thermodynamic diagram indeed goes from 1 to
2 and then it goes in the combustion from
2 to 3. The question is; if you do not have
compression, what will happen is to reach
that
temperature 3, for example, you have to start
your combustion process at one, and then
go all the way along this and reach that temperature
3 along that path.
Now, that path as you can very imagine now
is going to be a very long path of a burning
of a fuel and the burning of fuel would then
be done at a low pressure and not at a high
pressure. So, the path of combustion would
then be extremely large. To reach that same
temperature levels from which you can hopefully
do some amount of expansion. The
point is for good combustion, you need to
have a good compression.
Without a good compression, the combustion
process of in and that being a very
inefficient process. So, for combustion or
for a good combustion, you do need a certain
amount of compression to accomplished, before
the flow is taken through the
combustion chamber. Now, once the flow is
taken through the combustion chamber, you
have high energy gas. You have compressed
gas and you have high temperature gas,
which is then fed into the expansion system.
Now, the first expansion system as you see
here is actually the turbine. Now, this turbine
essentially is an expander indeed, and we
will be covering turbine in grid detail in
this
course. This produces work or as it written
here, the Compressed burned gas essentially
facilitates turbine work production. Turbine
is the work producer or work work exactor
from the high energy gas and this work essentially
extracted produced to run the
compressor. So, the entire work produced here,
in typical aircraft engine is transferred
to
the compressors, which then thus a compressor
job to take the flow to high pressure.
So, turbine and compressor essentially are
coupled and they work in a loop hoses certain
amount of energy then actually is fed into
the gas or into the air through the compressor
and it is taken out through the turbine. So,
that amount of energy is essentially going
into
this energy loop, which is between the turbine
and the compressor, it goes to the
combustion chamber again comes back to the
turbine into the compressor and then
remainder of the energy is fed into the jet
nozzle to create the Jet Thrust.
So, you do need compressor to take the flow
to high pressure, which facilitates the work
of the turbine, and then it secondly facilitates
the work of the jet nozzle for creation of
thrust. So, compressor is a very important
part of an aircraft engine, for most of the
aircraft engine that we know of and as a result
of which it has become integral part of
aircraft propulsion system, right from the
beginning of flying. Now, let us take a quick
look at what an aircraft engine, a modern
aircraft engine, typically would look like
consisting of compressors, combustion chambers
and turbines.
Now, if you look at this engine, you would
see, there are so many parts, we would be
dealing essentially with Fans, Compressors.
So, the flow goes through these fans and
then goes through these ducting system then
into the compressors, and then through large
amount of compression, through let us say
various compressors stages and those various
stages would be introduced to you and then
fed into the combustion chamber, and finally
the flow goes from the combustion chamber
into the turbine, which extracts the work
and
through the shaft system runs the compressor.
We will be talking about the multi - shaft
system or multi - spool system by which various
groups of turbines run, various groups
of compressors or fans. So, those things would
be introduced to you in the process of this
lecture series. What we have here is very
complex machinery of compressors, fans on
one hand and turbines on the other hand, on
calling these machineries, because these are
fundamentally aerodynamic machines. These
aerodynamic machines are essentially used
inside their craft engine for creation of
thrust.
So, these are essentially aerodynamic machines,
make a mistake about it they are indeed
machines, that work that produce work, that
absorb work and finally that helps in
creation of thrust. Let us take a closer look
at some of these components, which make up
an aircraft engine.
If you look at this components, you will see
here compressors. The first picture on the
left that you see here is indeed a multi - stage
compressor. You can see here, so many
rows of blades and one row of blade here,
a router here is shown here, in a little more
detail. It consists of so many blades. These
blades as we go along, we shall see are
indeed made up of aerofoils actions. And these
aerofoils actions are the basses of which
these blades are made, and then these blades
are lined up.
First they are arranged a comparentially in
a certain manner and then rows of these
comparentially arrange rotors are lined up
to make, what is called a multi-stage
compressor? Now, in between these rotors,
we shall see later on as we go along, we
would have compressor stators; that means,
another row of blades, which are stationary
and hence they are called stators.
These stator blades again row or shown here
in some detail and these are the blades that
come in between two rows of rotors. So, we
have 1 row of router and then other row of
stator and here the final assembly shown,
where rotors and stators surrounded and
covered by a casing, which is the final assembly
we shown here.
So, we have a compressor, which consist of
a large number of blades, which are arranged
in a certain manner and those manners are
what we are going to talk about in great detail,
and when you arranged them correctly. And
when you arrange them in an appropriate
manner, you have a compressor that produces
compression and feeds the compressed
here into the combustion chamber. So, this
is what a compressor is whole about, we will
take a look at a turbine. A turbine is typically
made up of high temperature material.
So, as you can see here in this picture. It
shows that it is of a different color, because
it is
made up of very high temperature material,
high temperature gas from the combustion
chamber is going into the turbine. But these
turbines are also made up of aerofoils
slightly different kind of aerofoils, but
indeed they are aerofoils and those aerofoils
kinds
are shown over here, on the right hand side.
These kinds of aerofoils are used in turbine
blades in rotors and in stators. The one you
see in the right hand side is indeed a rotor
and one on the left hand side is indeed a
stator.
You can see here, some very small row of holes
drilled along the surface of this stator
blade and these rows of small holes essentially
or micro holes, essentially are the cooling
mechanism that cools this blade internally
and gives it sufficient life to work for few
thousands of hours.
We will be talking about the mechanism of
the cooling, their dynamics of the cooling
and how the cooling essentially enhances,
the working life of a turbine in a useful
manner. We will be talking about those things
as a part of all lecture series. So, this
is
what a turbine essentially would be looking
like again it is made up of aerofoils and
we
will have to understand, how this aerofoils
are arranged to make up turbine blades.
The other kind of compressors that we would
be indeed talking about other centrifugal
compressors, which Professor Pradeep mentioned
and these centrifugal compressors
indeed the other kind of turbines is the radial
turbines, and we will see later on that the
radial turbines and centrifugal compressors
outwardly, they are not really similar. They
work very differently, but looks wise they
may look somewhat similar to each other.
So, I am showing you here, a typical centrifugal
compressor, which also does the job of
compression and this flow here, it enters
over here, it goes out from this side and
then its
surrounded by a row of diffusers, which is
indeed equivalent to the stators that we talked
about for actual compressors and when you
put them together, the diffuser and the
impeller together, you have a compressor.
In addition to these 2 units, you also have
this compressor manifold, which essentially
then take up the compressed air and supplied
to the combustion chamber, as you can see
here, there are number of supply manifolds,
which are essentially supplying to various
combustion chambers. So, a centrifugal compressor
essentially consists of an impeller or
diffuser and then of course, a set of manifold,
which supply the compressed air to various
combustion chambers.
So, these are the components with which, we
shall be dealing with in great detail. We
shall see, how these components are indeed
made out how they are analyzed, exactly
what shapes they are how do they work, and
finally, we use CFD in the modern
compressor analysis and design.
And we shall see, how these shapes are essentially
created with an analyze with the help
of CFD. So, that would be the course coverage
in this particular course. I will round up
today’s introduction with a comments that
he would do need to have a good grinding,
in
the basics of aerodynamics.
We shall be using, those basic aerodynamic
knowledge all the time and we will not have
time to go back and essentially detail out
those fundamental concepts all over again.
We
will be assuming that you are familiar with
those fundamental concepts.
So, you may really need, to get yourself familiarized
with those fundamental concepts
and as I mentioned, that we will be using
certain concepts of CFD. It may be useful,
if
you have a passing knowledge of CFD. So that
when we come to towards the end of this
lecture series and we get into using CFD for
computational analyses of compressor
turbines.
It is necessary that you have some passing
knowledge of CFD; we will mention that
when this blades and impeller shapes are created.
It may be useful for you to have some
knowledge of geometric modeling. The cad models,
which are often used to finally give
shapes to this complex shapes, which as I
mentioned are essentially aerodynamic
machines. You need to give them aerodynamic
shapes for these machines to work in an
efficient manner.
So, the this is what we would be doing in
this lecture series, over a period of little
more
than 40 lectures and in the process, we hope
that we will be able to introduce to you the
fundamental aerodynamic details of compressors,
turbines, how they are analyzed, how
they are designed, and how they are finally
created to go inside aircraft engines in
modern aircraft engine for creation of thrust.
