1. No category

TRUBA COLLEGE OF ENGINEERING & TECHNOLOGY
INDORE (M.P.)
“FABRICATION OF BASIC STIRLING ENGINE MODEL”
A MINOR PROJECT REPORT-2012
A minor project report submitted at
Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal
In partial fulfillment of the requirement as per the curriculum of
BE IIIrd year in the Mechanical Engineering.
SUBMITTED BY
MANISH SOLANKI (0830ME091032)
MD. UMAR KHAN (0830ME091035)
ROHAN GORALKAR (0830ME091050)
SUBMITTED TO:
GUIDED BY:
PROF. MRS. SUMAN SHARMA
Asst.Prof. MR. VISHAL ACHWAL
(HEAD OF DEPARTMENT)
DEPARTMENT OF MECHANICAL ENGINEERING
1
TRUBA COLLEGE OF ENGINEERING & TECHNOLOGY
INDORE (M.P.)
“FABRICATION OF BASIC STIRLING ENGINE MODEL”
A MINOR PROJECT REPORT-2012
SUBMITTED BY
MANISH SOLANKI (0830ME091032)
MD. UMAR KHAN (0830ME091035)
ROHAN GORALKAR (0830ME091050)
SUBMITTED TO:
PROF. MRS. SUMAN SHARMA
GUIDED BY:
Asst.Prof .MR. VISHAL ACHWAL
(HEAD OF DEPARTMENT )
DEPARTMENT OF MECHANICAL ENGINEERING
2
TRUBA COLLEGE OF ENGINEERING & TECHNOLOGY
INDORE, (M.P.)
CERTIFICATE
This is to certify that the project work entitled
“ FABRICATION OF BASIC STIRLING ENGINE MODEL”
has been carried out by, MANISH SOLANKI, MD. UMAR KHAN ,
ROHAN GORALKAR students of third year B.E. Mechanical Engineering under our
supervision & guidance. They have submitted this Minor project report towards partial
fulfillment for the award of Bachelor of Engineering in Mechanical Engineering of
Rajiv Gandhi Prodyogiki Vishvavidyalaya, Bhopal
during the academic year 2011-2012.
Asst.Prof.Mr. Vishal Achwal
Project Guide
Mechanical Engg Dept. TCET
Prof. Suman Sharma Madam
Head of Department
Mechanical Engg Dept. TCET
Director
TCET, INDORE
DEPARTMENT OF MECHANICAL ENGINEERING
3
TRUBA COLLEGE OF ENGINEERING & TECHNOLOGY
INDORE, (M.P.)
RECOMMENDATION
This is to certify that
MANISH SOLANKI, MD. UAMR KHAN, ROHAN GORALKAR
Students of Final year B.E (Mechanical Engineering)
Of this institute have completed the project work entitled
“FABRICATION OF BASIC STIRLING ENGINE MODEL”
Based on the syllabus and have submitted a satisfactory report on it in the
Academic year 2011-2012.
INTERNAL EXAMINER
EXTERNAL EXAMINER
Date-
Date-
DEPARTMENT OF MECHANICAL ENGINEERING
4
ACKNOWLEDGEMENT
Working in this institute during this project had been a great learning
experience for us. We take this opportunity to express our sincere gratitude
to all those people who have been instrumental in making our project a
success.
“To make efforts is better than to achieve success and choose the capable
person for success is greater than to make and succeed.”
We feel deeply indebted to our project Guided by: Asst. Prof. Vishal
Achwal
( Lecturer Mechanical Engineering Department) who generously shared
his wisdom, experience and expertise with us and guided us through the
project. We thank him for all his valuable guidance and suggestions.
We also extend our sincere thanks to all the faculty members of
Mechanical Engineering Department for their constant guidance and
support.
We express our deep sense of gratitude to Dr.P.K.CHANDE
(Director, T.C.E.T.) for his liberal encouragement and moral support not
only during this project but also throughout the studies.
Manish Solanki
Md.Umar Khan
Rohan Goralkar
1
ABSTRACT
The performance of Stirling engines meets the demands of the efficient use
of energy and environmental security and therefore they are the subject of
much current interest. Hence, the development and investigation of Stirling
engine have come to the attention of many scientific institutes and
commercial companies. The Stirling engine is both practically and
theoretically a significant device, its practical virtue is simple, reliable and
safe which was recognized for a full century following its invention by
Robert Stirling in 1816. The engine operates on a closed thermodynamic
cycle, which is reversible.
The objective of this project paper is to provide fundamental information
and present a detailed review of the efforts taken by us for the development
of the Stirling cycle engine and techniques used for engine analysis. A
number of attempts have been made by us to build and improve the
performance of Stirling engines. It is seen that for successful operation of
engine system with good efficiency a careful design, proper selection of
drive mechanism and engine configuration is essential. This project paper
indicates that a Stirling cycle engine working with relatively low
temperature with air or helium as working fluid is potentially attractive
engines of the future, especially solar-powered low-temperature differential
Stirling engines.
2
CONTENT
Page No.
1. Introduction
1.1 Thermodynamic cycle
1.2 Heat and Work
1.3 Well known thermodynamic cycle’s
1.4 History of Stirling Engine
5
6
7
12
14
2. Literature Review
2.1 Presentation of Stirling Engines
2.1.1 Stirling thermodynamic cycle
15
18
18
2.2 Analysis of the Stirling-Cycle Engine
2.2.1 Work done by an ideal Stirling-cycle
2.2.2 Heat flow in an ideal Stirling-cycle
2.2.3 Efficiency of an ideal Stirling-cycle
2.2.4 Actual Stirling Engine
20
20
22
23
24
2.3 Engine configurations
2.3.1 Alpha Stirling
2.3.2 Beta Stirling
2.3.3 Gamma Stirling
25
26
28
30
2.4 Technical complexity of topic
31
3. Model Description
3.1 Design & Drawing
3.1.1 Stand & Cylinder
3.1.2 Piston
3.1.3 Fan Acting as Crank
3.1.4 Connecting Rod & Link
3.1.5 Assembly in Pro-Engineer software
3.2 Methodology
3.2.1 Assembly & Procedure
3.2.2 Our Stirling Engine Mode
3.3 Expenses
32
33
34
35
35
36
36
37
37
39
40
4. Advantages
41
3
Page No.
5. Disadvantages
5.1 Problems And Iteration
5.2 Causes Of Failure
6. Analyze From Economic Point
7. Applications of The Stirling Power
7.1. Cars
7.2. Submarine.
7.3. Nuclear power
7.4. Solar Energy
7.5. Aircraft engines
8. Conclusion
9. References
10. List of Figures
11. List of Tables
43
44
44
45
48
48
48
48
49
49.
50
52
54
55
4
INTRODUCTION
5
INTRODUCTION
1.1 Thermodynamic cycle
Thermodynamics
HEAT FLOW: FIGURE: 1
State:
Equation of state
Ideal gas · Real gas
Phase of matter · Equilibrium
Control volume · Instruments
Processes:
Isobaric · Isochoric · Isothermal
Adiabatic · Isentropic · Isenthalpic
Quasistatic · Polytropic
Free expansion
Reversibility · Irreversibility
Endoreversibility
Cycles:
Heat engines · Heat pumps
Thermal efficiency
6
Material properties:
Specific heat capacity
Compressibility
Thermal expansion
Potentials:
Internal energy
Enthalpy
Helmholtz free energy
Gibbs free energy
A thermodynamic cycle consists of a series of thermodynamic processes
transferring heat and work, while varying pressure, temperature, and other
state variables, eventually returning a system to its initial state. In the
process of going through this cycle, the system may perform work on its
surroundings, thereby acting as a heat engine.
State quantities depend only on the thermodynamic state, and cumulative
variation of such properties adds up to zero during a cycle. Process
quantities (or path quantities), such as heat and work are process dependent,
and cumulative heat and work are non-zero. The first law of
thermodynamics dictates that the net heat input is equal to the net work
output over any cycle. The repeating nature of the process path allows for
continuous operation, making the cycle an important concept in
thermodynamics. Thermodynamic cycles often use quasistatic processes to
model the workings of actual devices.
1.2 Heat and work
Two primary classes of thermodynamic cycles are power cycles and heat
pump cycles. Power cycles are cycles which convert some heat input into a
mechanical work output, while heat pump cycles transfer heat from low to
high temperatures using mechanical work input. Cycles composed entirely
of quasistatic processes can operate as power or heat pump cycles by
controlling the process direction. On a pressure volume diagram or
temperature entropy diagram, the clockwise and counterclockwise
directions indicate power and heat pump cycles, respectively.
7
Relationship to work
Example of P-V diagram of a thermodynamic cycle
FIGURE : 2
Because the net variation in state properties during a thermodynamic cycle
is zero, it forms a closed loop on a PV diagram. A PV diagram's Y axis
shows pressure (P) and X axis shows volume (V). The area enclosed by the
loop is the work (W) done by the process:
This work is equal to the balance of heat (Q) transferred into the system:
Equation (2) makes a cyclic process similar to an isothermal process: even
though the internal energy changes during the course of the cyclic process,
when the cyclic process finishes the system's energy is the same as the
energy it had when the process began.
If the cyclic process moves clockwise around the loop, then W will be
positive, and it represents a heat engine. If it moves counterclockwise, then
W will be negative, and it represents a heat pump.
8
The clockwise thermodynamic cycle indicated by the arrows shows that the
cycle represents a heat engine. The cycle consists of four states (the point
shown by crosses) and four thermodynamic processes (lines).
For example the pressure-volume mechanical work done in the heat engine
cycle, consisting of 4 thermodynamic processes, is:
If no volume change happens in process 4->1 and 2->3, equation (3)
simplifies to:
Thermodynamic cycles may be used to model real devices and systems,
typically by making a series of assumptions.simplifying assumptions are
often necessary to reduce the problem to a more manageable form.For
example, as shown in the figure, devices such a gas turbine or jet engine can
be modelled as a Brayton cycle. The actual device is made up of a series of
stages, each of which is itself modelled as an idealized thermodynamic
process. Although each stage which acts on the working fluid is a complex
real device, they may be modelled as idealized processes which
approximate their real behavior. A further assumption is that the exhaust
gases would be passed back through the inlet with a corresponding loss of
heat, thus completing the idealized cycle.
The difference between an idealized cycle and actual performance may be
significant. For example, the following images illustrate the differences in
work output predicted by an ideal Stirling cycle and the actual performance
of a Stirling engine:
9
Ideal Stirling cycle
FIGURE: 3
Actual and ideal overlaid, showing difference in work output
FIGURE: 4
10
Actual performance
FIGURE: 5
The adiabatic Stirling cycle is similar to the idealized Stirling cycle;
however, the four thermodynamic processes are slightly different (see graph
above):




180° to 270°, pseudo-Isothermal Expansion. The expansion-space is
heated externally, and the gas undergoes near-isothermal expansion.
270° to 0°, near-constant-Volume (or near-isometric or isochoric)
heat-removal. The gas is passed through the regenerator, thus cooling
the gas, and transferring heat to the regenerator for use in the next
cycle.
0° to 90°, pseudo-Isothermal Compression. The compression space is
intercooled, so the gas undergoes near-isothermal compression.
90° to 180°, near-constant-Volume (near-isometric or isochoric) heataddition. The compressed air flows back through the regenerator and
picks-up heat on the way to the heated expansion space.
11
With the exception of a Stirling thermoacoustic engine, none of the gas
particles actually flows through the complete cycle. So this approach is not
amenable to further analysis of the cycle. However, it provides an overview
and indicates the cycle work.
As work output is represented by the interior of the cycle, there is a
significant difference between the predicted work output of the ideal cycle
and the actual work output shown by a real engine. It may also be observed
that the real individual processes diverge from their idealized counterparts;
e.g., isochoric expansion (process 1-2) occurs with some actual volume
change.
1.3 Well-known thermodynamic cycles
In practice, simple idealized thermodynamic cycles are usually made out of
four thermodynamic processes. Any thermodynamic processes may be
used. However, when idealized cycles are modeled, often processes where
one state variable is kept constant are used, such as an isothermal process
(constant temperature), isobaric process (constant pressure), isochoric
process (constant volume), isentropic process (constant entropy), or an
isenthalpic process (constant enthalpy). Often adiabatic processes are also
used, where no heat is exchanged.
12
Some example thermodynamic cycles and their constituent processes are as follows:
Process 1-2
(Compression)
Cycle
Process 2-3
Process 3-4
(Heat
(Expansion)
Addition)
Process 4-1
(Heat
Rejection)
Notes
Power cycles normally with external combustion - or heat pump cycles:
A reversed
Brayton cycle
Bell
Coleman
adiabatic
isobaric
adiabatic
isobaric
Carnot
isentropic
isothermal
isentropic
isothermal
Ericsson
isothermal
isobaric
isothermal
isobaric
the second
Ericsson cycle
from 1853
Rankine
adiabatic
isobaric
adiabatic
isobaric
Steam engine
Scuderi
adiabatic
variable
pressure
and volume
adiabatic
isochoric
Stirling
isothermal
isochoric
isothermal
isochoric
Stoddard
adiabatic
isobaric
adiabatic
isobaric
Power cycles normally with internal combustion:
Brayton
adiabatic
isobaric
adiabatic
isobaric
Diesel
adiabatic
isobaric
adiabatic
isochoric
Lenoir
isobaric
isochoric
adiabatic
Otto
adiabatic
isochoric
adiabatic
Pulse jets
(Note: Process 12 accomplishes
both the heat
rejection and the
compression)
isochoric
Known Thermodynamic Cycles: TABLE: 1
13
Jet engines
the external
combustion
version of this
cycle is known as
first Ericsson
cycle from 1833
Gasoline / petrol
engines
1.4 HISTORY:
The Stirling engine were invented in 1816 by Robert Stirling in Scotland,
some 80 years before the invention of diesel engine, and enjoyed substantial
commercial success up to the early 1900s. A Stirling cycle machine is a
device, which operates on a closed regenerative thermodynamic cycle, with
cyclic compression and expansion of the working fluid at different
temperature levels. The flow is controlled by volume changes so that there
is a net conversion of heat to work or vice versa. The Stirling engines are
frequently called by other names, including hot-air or hot-gas engines, or
one of a number of designations reserved for particular engine arrangement.
In the beginning of 19th century, due to the rapid development of internal
combustion engines and electrical machine, further development of Stirling
engines was severely hampered.
Sketch of Robert Stirling of his invent
FIGURE: 6
14
LITERATURE REVIEW
15
2. LITERATURE REVIEW
The Stirling Engine is one of the hot air engines. It was invented by Robert
Stirling (1790-1878) and his brother James. At this period, he found the
steam engines are dangerous for the workers. He decided to improve the
design of an existing air engine. He hope it wound be safer alternative.
After one year, he invented a regenerator. He called the “Economizer” and
the engine improves the efficiency. This is the earliest Stirling Engine. It is
put out 100 W to 4 kW. The Ericsson invented the solar Energy in 1864 and
did some improvements for after several years. Robert’s brother, James
Stirling, also played an important role in the development of Stirling
engines.
Earliest Stirling engine
FIGURE: 7
16
The original patent by Reverend Stirling was called the "economizer", for
its
Improvement of fuel-economy. The patent also mentioned the possibility of
using the device in an engine. Several patents were later determined by two
brothers for different configurations including pressurized versions of the
engine. This component is now commonly known as the "regenerator" and
is essential in all high-power Stirling devices.
During the early part of the twentieth century the role of the Stirling engine
as a "domestic motor" was gradually usurped by the electric motor and
small
Internal combustion engines until by the late 1930s it was largely forgotten,
only produced for toys and a few small ventilating fans. At this time Philips
was seeking to expand sales of its radios into areas where mains electricity
was unavailable and the supply of batteries uncertain. Philips’
Management decided that offering a low-power portable generator would
facilitate such sales and tasked a group of engineers at the company
research lab (the Nat. Lab) in Eindhoven to evaluate the situation. After a
systematic comparison of various prime movers the Stirling engine was
considered to have real possibilities as it was among other things, inherently
quiet (both audibly and in terms of radio interference) and capable of
running from any heat source (common lamp oil was favored). They were
also aware that, unlike steam and internal combustion engines, virtually no
serious development work had been carried out on the Stirling engine for
many years and felt that with the application of modern materials and
know-how great improvements should be possible.
17
2.1 PRESENTATION OF STIRLING ENGINES
2.1.1 STIRLING THERMODYNAMIC CYCLE
The Stirling engine cycle is a closed cycle and it contains, most commonly
a fixed mass of gas called the "working fluid" (air, hydrogen or helium).
The principle is that of thermal expansion and contraction of this fluid due
to a temperature differential.
So the ideal Stirling cycle consists of four thermodynamic distinct processes
acting on the working fluid: two constant-temperature processes and two
constant volume processes.
Each one of which can be separately analyzed:
Stirling thermodynamic cycle: FIGURE:8
18
Process Involved In Stirling Cycle:
 1-2: isothermal compression process. Work W1-2 is done on the
working fluid, while an equal amount of heat Q1-2 is rejected by the
system to the cooling source. The working fluid cools and contracts
at constant temperature TC.
 2-3: constant volume displacement process with heat addition.
Heat Q 2-3 is absorbed by the working fluid and temperature is raised
from TC to TH. No work is done.

3-4: isothermal expansion process. Work W3-4 is done by the
working fluid, while an equal amount of heat Q3-4 is added to the
system from the heating source. The working fluid heats and expands
at constant temperature TH.
 4-1: constant volume displacement process with heat rejection.
Heat Q4-1 is rejected by the working fluid and temperature decrease
from TC to TH. No work is done.
19
2.2 ANALYSIS OF THE STIRLING-CYCLE
ENGINE
2.2.1 Work done by an ideal Stirling-cycle engine
The net work output of a Stirling-cycle engine can be evaluated by
considering the cyclic integral of pressure with respect to volume:
W=-∮
This can be easily visualized as the area enclosed by the process curves on
the pressure-volume. To evaluate the integral we need only consider the
work done during the isothermal expansion and compression processes,
since there is no work done during the isochoric processes, i.e.
W=-[ ∫
+∫
(4.1)
By considering the equation of state:
pV =mRT
and noting that T is constant for an isothermal process, and m is constant for
a closed cycle, then an expression for work done during an isothermal
process can be formulated:
∫
( )
∫
(4.2)
so that by substitution of Equation 4.2 into Equation 4.1,we can evaluate
the work integral:
(
)
(
(
)
)
(
)
where the subscripts H and L denote the high and low temperature
isotherms respectively.
This equation can then be further simplified by noting that V4 = V1 and V3
= V2 so that a final equation for work can be obtained:
20
(
)(TH -TL)
(4.3)
The work done represents energy out of the system, and so has a negative
value according to the sign convention used here.
Inspection of Equation 4.3, therefore, shows that the work output for a
Stirling-cycle machine can be increased by maximizing the temperature
difference between hot and cold ends (TH-TL), the compression ratio
(V2/V1), the gas mass (and hence either the total volume of the machine
and/or the mean operating pressure), or the specific gas constant.
Material strength/temperature considerations and practicalities such as the
overall size of the machine usually limit the amount that the temperature,
volume, or pressure can be increased.
However, it is interesting to note that the specific work output (i.e. work
output per kilogram) can be dramatically enhanced in a Stirling-cycle
machine simply by selecting a working gas with a high specific gas
constant.
One of the reasons that hydrogen and helium are so often used as the
working gas in large Stirling-cycle machines can be deduced by inspection
of the values for specific gas constants given in Table 4.1. (another reason
is the lower flow losses that occur with smaller molecule gases).
Table: Specific gas constants for a variety of gases at 300 K
Gas
Specific gas constant,
R (J/kgK)
319.3
488.2
188.9
2077.0
4124.2
296.8
188.6
461.5
Air
Ammonia
Carbon dioxide
Helium
Hydrogen
Nitrogen
Propane
Steam
Specific gas constants: TABLE: 2
21
2.2.2 Heat flow in an ideal Stirling-cycle engine
The heat flowing into and out of a Stirling-cycle engine can be evaluated by
considering the integral of temperature with respect to entropy:
∫
Since the isochoric heat transfers within the regenerator are completely
internal to the cycle, i.e. -Q2-3 = Q4-1, then to evaluate the heat flows into
and out of the system we need only consider the isothermal processes.
For the isothermal expansion process in a closed cycle (where T and m are
constant, and where the subscripts H and L denote the high and low
temperature isotherms respectively):
QH= ∫
H
dS
This integral can be most easily evaluated by considering the First Law of
Thermodynamics in the form:
QH=∫
∫
and by considering the equation of state:
pV=mRT n be expressed in terms of volume and temperature, and (noting
that there is no change in internal energy during an isothermal process) the
integral can be easily solved:
QH=∫
∫
H
dV = 0 + ∫
H
dV
giving:
QH = mRTH ln ( )
(4.4)
which is a somewhat convoluted (but hopefully instructive) method of
derivation. The same expression can, of course, be obtained much more
easily by simple inspection of Equation 4.3., since the heat and work
transfers for an isothermal expansion process are equal but opposite.
22
The isothermal compression process can also be readily evaluated (noting
that V4 = V1 and V3 = V2, and where the subscripts H and L denote the high
and low temperature isotherms respectively), giving:
QL = - mRTL ln ( )
(4.5)
2.2.3 Efficiency of an ideal Stirling-cycle engine
The efficiency of any heat engine is defined as the ratio of work output to
heat input, i.e.
hence an equation for the efficiency of an ideal Stirling-cycle engine can be
developed by considering Equations 4.3. and 4.4., giving:
STIRLING=
which simplifies to:
STIRLING=
this demonstrates the interesting fact that the efficiency of an ideal Stirlingcycle engine is dependant only on temperature and no other parameter. It is
worth recalling that the Carnot efficiency for a heat engine is:
CARNOT=
and so it will readily be observed that:
STIRLING =
CARNOT
or, in other words, that the Stirling-cycle engine has the maximum
efficiency possible under the Second Law of Thermodynamics. However, it
should be noted that unlike the Carnot Cycle, the Stirling-cycle engine is a
practical machine that can actually be used to produce useful quantities of
work.
23
2.2.4 Actual Stirling Engine
Actual Stirling Engine: FIGURE: 9
In real life, it is not possible to have isothermal and isochoric process
because they are instantaneous. In stirling cycle heat addition and rejection
is assumed to be instantaneous which is not possible and because of some
internal losses in friction and other the actual graph is oval shape.
24
2.3 ENGINE CONFIGURATIONS
Mechanical configurations of Stirling engines are classified into three
important distinct types: Alpha, Beta and Gamma arrangements.
These engines also feature a regenerator (invented by Robert Stirling). The
regenerator is constructed by a material that conducts readily heat and has a
high surface area (a mesh of closely spaced thin metal plates for example).
When hot gas is transferred to the cool cylinder, it is first driven through the
Regenerator, where a portion of the heat is deposited. When the cool gas is
transferred back, this heat is reclaimed. Thus the regenerator “pre heats”
and “pre cools” the working gas, and so improve the efficiency.
But many engines have no apparent regenerator like beta and gamma
engines configurations with a “loose fitting” displacer, the surfaces of the
displacer and its cylinder will cyclically exchange heat with the working
fluid providing some regenerative effect.
25
2.3.1 Alpha Stirling :
Alpha engines have two separate power pistons in separate cylinders which
are connected in series by a heater, a regenerator and a cooler. One is a
“hot” piston and the other one a “cold piston”.
Alpha Stirling: FIGURE: 10
The hot piston cylinder is situated inside the high temperature heat
exchanger and the cold piston cylinder is situated inside the low
temperature heat exchanger. The generator is illustrated by the chamber
containing the hatch lines.
Alpha type Stirling.
FIGURE: 11
26
Expansion: At this point, the most of
the gas in the system is at the hot
piston and expands, pushing the hot
piston down, and flowing through the
pipe into the cold cylinder, pushing it
down as well.
Contraction: Now the majority of
the expanded gas is shifted to the
cool piston cylinder. It cools and
contracts, drawing both pistons up.
Transfer: At this point, the gas
has expanded. Most of the gas
is still in the
Hot cylinder. As the crankshaft
continues to turn the next 90°,
transferring the bulk of the gas
to the cold piston cylinder. As it
does so, it pushes most of the
fluid through the heat
exchanger and into the cold
piston cylinder
Transfer: The fluid is cooled and
now crankshaft turns another 90°.
The gas is therefore pumped back,
through the heat exchanger, into
the hot piston cylinder. Once in
this, it is heated and we go back to
the first step.
This type of engine has a very high power-to-volume ratio but has technical
problems due to the usually high temperature of the "hot" piston and its
seals.
27
2.3.2 Beta Stirling
The Beta configuration is the classic Stirling engine configuration and has
enjoyed popularity from its inception until today. Stirling's original engine
from his patent drawing of 1816 shows a Beta arrangement.
Both Beta and Gamma engines use displacer-piston arrangements. The Beta
engine has both the displacer and the piston in an in-line cylinder system.
The Gamma engine uses separate cylinders.
The purpose of the single power piston and displacer is to “displace” the
working gas at constant volume, and shuttle it between the expansion and
the compression spaces through the series arrangement cooler, regenerator,
and heater.
A beta Stirling has a single power piston arranged within the same cylinder
on the same shaft as a displacer piston. The displacer piston is a loose fit
and does not extract any power from the expanding gas but only serves to
shuttle the working gas from the hot heat exchanger to the cold heat
exchanger.
Beta Stirling: FIGURE: 12
28
Expansion: At this point, most of the
Transfer: At this point, the gas has
gas in the system is at the heated end
expanded. Most of the gas is still
of the cylinder. The gas heats and
located in the hot end of the
expands driving the power piston
cylinder. Flywheel momentum carries
outward.
the crankshaft the next quarter turn.
As the crank goes round, the bulk of
the gas is transferred around the
displacer to the cool end of the
cylinder, driving more fluid into the
cooled end of the cylinder.
Contraction: Now the majority of
the expanded gas has been shifted
to the cool end. It contracts and the
displacer is almost at the bottom of
its cycle.
Transfer: The contracted gas is still
located near the cool end of the
cylinder. Flywheel momentum
carries the crank another quarter
turn, moving the displacer and
transferring the bulk of the gas
back to the hot end of the cylinder.
And at this point, the cycle repeats.
29
2.3.3 Gamma Stirling
A gamma Stirling is simply a beta Stirling in which the power piston is
mounted in a separate cylinder alongside the displacer piston cylinder, but
is still connected to the same flywheel. The gas in the two cylinders can
flow freely between them and remains a single body. This configuration
produces a lower compression ratio but is mechanically simpler and often
used in multi-cylinder Stirling engines. Gamma type engines have a
displacer and power piston, similar to Beta machines, but in different
cylinders. This allows a convenient complete separation between the heat
exchangers associated with the displacer cylinder and the compression and
expansion work space associated with the piston.
Gamma engine’s configuration
FIGURE: 13
Furthermore during the expansion process some of the expansion must take
place in the compression space leading to a reduction of specific power.
Gamma engines are therefore used when the advantages of having separate
cylinders outweigh the specific power disadvantage.
The advantage of this design is that it is mechanically simpler because of
the convenience of two cylinders in which only the piston has to be sealed.
The disadvantage is the lower compression ratio but the gamma
configuration is the favorite for modelers and hobbyists.
30
TECHNICAL COMPLEXITY OF TOPIC
The Stirling cycle is a highly advanced subject that has defied analysis by
many experts for over 190 years. Highly advanced thermodynamics are
required to describe the cycle. Professor Israel Urieli writes: "...the various
'ideal' cycles (such as the Schmidt cycle) are neither physically realizable
nor representative of the Stirling cycle" [
The analytical problem of the regenerator (the central heat exchanger in the
Stirling cycle) is judged by Jakob to rank 'among the most difficult and
involved that are encountered in engineering '.
Piston motion variations
A model of a four-phase Stirling cycle
FIGURE:14
31
MODEL DESCRIPTION
32
3.1 DESIGN AND DRAWING
MATERIAL
TIN
TIN
LENGTH DIAMETER THICKNESS
(mm)
(mm)
(mm)
200
105
80
50
1
1
PISTON
1 HARD FIBRE
(HOLLOW)
2 HARD FIBRE
25
78
3
15
48
1
1 ALUMINIUM
2 ALUMINIUM
3 ALUMINIUM
WOOD
4
250
300
270
300
3
3
3
25*
SOLID
SOLID
SOLID
8
CYLINDER 1
2
LINK
STAINLESS
STEEL
BEARING
6000z
CRANK RADUIS
1 (mm)
PLASTIC
22
(Note: * Represents rectangular section width)
DESIGN: TABLE: 3
CRANKSHAFT
Clearance volume, V1=
MATERIAL
(D1)2 L1 = 1.231 x 10(-5) m3
D2 L2
=2.155 x 10(-5) m3
Heat given (through wax i.e. candle) = m x C.V.
= x V x C.V.
=0.93(g/cm3) x 3.53(m3) x 10(-5) x 106 x 7.8(kJ/g)
=253.8 kJ
V2 =
Work done ,
TH -TL)
Assuming TH = 120 0C (Temperature of hot air)
TL = 40 0C (Temperature of cold air)
W = 5.358 x m kJ
Hence, efficiency,
=
= 0.328=32.8 %( on assumed conditions)
33
PRO-ENGINEEER DESIGN & SPECIFICATION
3.1.1 STAND & CYLINDER
Criteria: Good thermal
conductivity
Easy machinable
Material preferred: Wood, Tin
Processing: Mig welding
For sealing ,M-Seal
Internal grinding through
Sand paper
FIGURE:15
HINGED SUPPORT: FIGURE:16
LINK: FIGURE: 17
34
3.1.2 PISTON
Criteria: Light weighted
Material preferred:
Hard fiber
Processing: Sealing on
both side Turning on surface
Finishing by lathe
machine
FIGURE:18
3.1.3 FAN ACTING AS CRANK
Criteria: Light weighted
Material preferred: Fiber
Processing: Bending to the required
crank radius
FIGURE:19
35
3.1.4 CONNECTING ROD & LINK
Criteria: Light weighted ,
Fatigue resistance
Material preferred:
Aluminum
FIGURE: 20
3.1.5 ASSEMBLY IN PRO-Engineer software:
ASSEMBLY: FIGURE: 21
36
3.2
METHODOLOGY
3.2.1 ASSEMBLY AND PROCEDURE
a. Firstly we have designed our stirling engine model on the software
Wildfire Pro- Engineer designing software 5.0; We have calculated
our Dimensions requirement on the software. All the analysis taken on
the software taken into consideration for the fabrication of our project.
b. As per the requirement we have gathered our parts from various places
from the market.Both the cylinders are connected perpendicularly via a
small diameter pipe through welding & M-seal .
c. For the assembly of our project our workshop was the better place for
the fabrication as we get all the facilities at the same place.
d. For the piston cylinder arrangement. We have used Tin Cylinders for
vertical position and PVC Pipe for Horizontal cylinder. For the
fabrication of piston for vertical we buyed solid hard fiber of cylindrical
shape.than by using LATHE machine available in workshop. By the
operations turning on that fiber with a small clearance of 2mm.
e. As per cylinder diameter is considered.Reciprocation of piston in the
cylinder is quiet freely. On piston a aluminium link has been
attached..(LENGTH AND DIAMETER SPECIFICATION IN TABLE 3) By
cutting the upper portion of cylinder for placing the horizontal cylinder
of varying dia.and upper portion for the air movement.All this parts were
arranged than fixed by M-Seal making the arrangement air tight.
f. Our Fan which is Acting as crank for both the arrangement is fixed on
the
bearing which is fixed by us on the wood frame fabricated by
us in Carpentry shop. Rest of the assembly was done by us at our
home.
g. Crank and links are connected. Now this whole model is placed on
rigid structure and clamped by strips to make
It rigid while
working.Hinged support for the vertical cylinder piston & FAN
arrangement is done by cutting a PVC pipe and providing wood rip
between the PVC and Attaching both the arrangement on the hinged
support. than fabricating horizontal piston & connecting rod and
attaching it to the crank.
37
h. Our model is ready to work by providing Heat BY candle. Than by
providing sufficient heat so that expansion of air takes place by which
the reciprocation of piston takes place easily which will help to rotate
our crank easily. Every arrangement in the engine is so light weighted so
that reciprocating motion can be achieved easily in both the cylinders.
i. Working: Through the expansion of air inside the cylinders piston
moves vertically upwards and which helps in moving the cold air above
the piston to the horizontal cylinder by reciprocating the piston
backwards, the link and the connecting rod arrangement is done in such
a way that the reciprocation of piston in respective cylinders helps in the
rotation of fan by the hinged support.
This process is continuous and thus fan rotates by small amount of heat.
and this cycle is ecofriendly and thus providing pollution free
environment.
j.
Future Aspects of our project: Continuous rotation of fan can be used
for the generation of electricity ,by providing Dynamo at the shaft of
fan .
38
3.2.2 OUR STIRLING ENGINE MODEL
Hinged
support
Cylinder 1
Flame
Fan Acting as
Crank
Cylinder 2
FIGURE: 22
CONTINOUS ROTATION OF FAN with small amount of
HEAT by CANDLE.
BY THE use of STIRLING Cycle concept.
39
3.3 EXPENSES SPEND ON OUR PROJECT
QUANTITY
PRICE
CYLINDER
2
50
PISTON
2
130
CONNECTING ROD
2
40
FAN
1
50
WOOD RIPS
1
10
M-SEAL(PACKETS)
3
75
CANDLES
3
25
WOODEN STAND
1
200
PVC PIPE
1
10
NAILS
20
10
45
BEARING
-
OTHER
TOTAL
50
695/-
EXPENSES: TABLE: 4
40
ADVANTAGES
41
4. ADVANTAGES
There are several reasons to use a Stirling Engine:
1. Inside the pistons can be used air, helium, nitrogen or hydrogen and you
don’t have to refill it because it uses always the same body of gas.
2. To produce heat you can use whatever you want: fuel, oil, gas, nuclear
power and of course renewable energies like solar, biomass or
geothermal heat.
3. The external combustion process can be designed as a continuous
process, so the most types of emissions can be reduced.
4. If heat comes from a renewable energy source they produce no
emissions
5. They run very silent and they don’t need any air supply. That’s why they
are used a lot in submarines. E.g. in the Royal Swedish Navy.
6. They can run for a very long time because the bearings and seals can be
placed at the cool side of the engine → they need less lubricant and they
don’t have to be checked very often ( longer period between the
overhauls ).
42
DISADVANTAGES
43
5. DISADVANTAGES
5.1 PROBLEMS AND ITERATION
1. Initially we have made crankshaft using separate flywheel for both
cylinders, in which link-crankshaft assembly functioning is not proper.
Hence it is replaced by crankshaft made by bending the rod.
2. Firstly we have used large links, this increases weight and vibration.
Therefore we have reduced their length.
3. Due to the large clearance between piston and cylinder, it is not able to
displace by hot air. Hence for decreasing clearance small diameter
cylinder is used and reassembling of the model has done.
5.2. CAUSES OF FAILURE
1. Required precision between the crankshaft and link arrangement is not
achieved. High precision equipments are costly.
2. Proper clearance between piston and cylinder is not provided.
3. Weight of the link is more.
4. Improper welding, machining and surface finishing.
44
6. ANALYZE FROM ECONOMIC POINT
As said above the Stirling engine is a kind of external combustion engine,
and it can use a variety of fuels. It can be estimated that combustible gases
are the best material, including gasoline, diesel, propane, sunshine and salad
oil; even cow dung can be run on as fuels.
A cup of coffee cannot become a cup of gasoline, but it can be also used as
a
Stirling engine driver. There is a famous experiment that a Stirling engine
can easily run on a cup of coffee. The Stirling engine is a kind of piston
engine. In the external heating sealed chamber, the expansion of gases
inside the engine promotes the pistons work. After the expanded gases
cooling down in the air –conditioned room, next process is taking on. As
long as a certain value of the temperature difference exists, a Stirling
Engine can be formed.
Stirling Engine working on a cup of coffee
FIGURE: 23
45
This experiment shows that only a very small power operation can carry out
a Stirling engine, which contributes a lot to energy conservation. This
characteristic especially shows out on economy point. The benefits obtained
from the Stirling engine are definitely far beyond the costs.
So once solar is used to produce energy for the Stirling engine, the cost
would surely be cut down for quite a lot. As long as there is sunshine, the
Stirling engine will run on and on. Of course it costs much to manufacture a
Stirling engine, as it requires a high level of the materials and
manufacturing processes.
Some engines cause a lot of pollution, so much is cost for pollution control
and government. On contrast, Stirling engine exhausts cleanly and avoid
this type of matter. Development and utilization of solar will not pollute the
environment, as solar is one of the cleanest energy. While the
environmental pollution is becoming more and more serious today, this
characteristic is extremely valuable. It saves the cost for a lot while making
sustainable development.
Nowadays, more and more countries have recognized that a society with
sustainable development should be able to meet the needs of the community
without endangering future generations. Therefore, use clean energy as
much as possible instead of the high carbon content of fossil energy is a
principle which should be followed during energy construction. Vigorously
develop new and renewable sources of energy utilization technology will be
an important measure to reduce pollution. Energy problem is a worldwide
one, and it is sooner or later to get into the transition-to-new-energy period.
Because of its sustainability, renewably and efficiency, the Stirling engine
is just the very one being consistent with the requirements of the times.
46
APPLICATIONS
47
7.APPLICATIONS OF THE STIRLING POWER
7.1.
Cars
In the ages of 1970s and 1980s several automobile companies like “General
Motors” or “Ford” were researching about Stirling Engine. This device is
good for a constant power setting, but it is a challenge for the stop and go of
the automobile.
A good car can change the power quickly. One possibility to obtain this
important characteristic is design a power control mechanism that will turn
up or down the burner. This is a slow method of changing power levels
because is not enough to accelerate crossing an intersection.
7.2.
Submarine
“Kockums”, a Swedish defense contractor, produce Stirling Engines for the
Navy making the quietest submarines in the world.This high-technology is
named air-independent propulsion (AIP). There are
four submarines equipment with Stirling AIP. The models are HMS Näcken,
which was launch in 1978 and after ten years 1988 became the first
submarine equipped with AIP system, by means of a cut and lengthened by
an intersection of a Stirling AIP section, which before the installation is
equipped by two Stirling units, liquid oxygen (LOX) tanks and electrical
equipment.
7.3.
Nuclear power
Steam turbines of a nuclear plan can be replaced by Stirling engine thus
reduce the radioactive by-products and be more efficient. Steam plants use
liquid sodium as coolant in breeder reactors, water/sodium exchanger are
required, which in some cases that temperature increase so much this
coolant could reacts violently with water.
NASA has developed a Stirling Engine known as Stirling Radioisotope
(SRG) Generator designed to generate electricity in for deep space proves
in lasting missions. The heat source is a dry solid nuclear fuel slug and the
cold source is space itself. This device converter produces about four times
more electric power from the plutonium fuel than a radioisotope
thermoelectric generator.
48
7.4.
Solar Energy
Placed at the focus of a parabolic mirror a Stirling engine can convert solar
Energy to electricity with efficiency better than non-concentrated
photovoltaic cells.
In 2005 It is created a 1 kW Stirling generator with a solar concentrator, this
was a herald of the coming of a revolutionary solar, nowadays It generates
electricity much more efficiently and economically than Photovoltaic (PV)
systems whit technology called concentrated solar power (CPS). Nowadays
the company Infina Applications has development a 3 kW Solar Stirling
Product.
By a mirror to focus the sun’s rays on the receiver end of a Stirling engine.
The internal side of the receiver then heats hydrogen gas, which expands.
The pressure created by the expanding gas drives a piston, crank shaft, and
drive shaft assembly much like those found in internal combustion engines
but without igniting the gas. The drive shaft is connected to a small
electricity generator.
This solar application is called concentration solar power (CSP) and is
significant potential grid for water pumping or electrification.
7.5. Aircraft engines
Stirling engines may hold theoretical promise as aircraft engines, if high
power density and low cost can be achieved. They are quieter, less
polluting, gain efficiency with altitude due to lower ambient temperatures,
are more reliable due to fewer parts and the absence of an ignition system,
produce much less vibration (airframes last longer) and safer, less explosive
fuels may be used.
49
CONCLUSION
50
8. CONCLUSION
Our Stirling engine model has a good point that they can be constructed in a
way that they produce no emissions. That means, in combination with solar
or geothermal heat, they can be used as a renewable energy source to
produce electricity by means of dynamo.
The real renewable energy is the solar application for this device because
the
other ways to produce the heat source are burning something. It is possible
to decrease the emissions of CO2 or other toxic gases but not eliminate
completely this problem for the earth and therefore for humans. This
application could be one of the different ways to solve the problem of
greenhouse gas emissions and to continue and also to develop our comfort.
No high-tech materials are needed.
Future Aspects of our project: Continuous rotation of fan can be used for
the generation of electricity ,by providing Dynamo at the shaft of fan .
51
REFERENCE
52
9. REFERENCE
http://www.kockums.se/News/photostock/photo.html
http://www.moteurstirling.com/alpha.htm
www.stirlingenergy.com/solar_overview.htm
www.stirlingenergy.com/images.asp?Type=solar
53
10. LIST OF FIGURES
S.NO.
FIGURE NAME
Page
no.
1.
2.
Heat Flow
P-v diagram of a thermodynamic
cycle
Ideal stirling cycle
Actual and ideal overlaid, showing
difference in work output
Actual performance
Sketch of Robert Stirling of his invent
Earliest stirling engine
Distinct processes
Actual stirling engine
Alpha stirling
Alpha type stirling
Beta stirling
Gamma engine’s configuration
A model of a four-phase Stirling cycle
Stand & cylinder
Hinged support
Link
Piston.
Fan acting as crank.
Connecting rod
Assembly in pro-engineer software
Our stirling engine model
Stirling engine working on a cup of
coffee
6
8
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
54
10
10
11
14
16
18
24
26
26
28
30
31
34
34
34
35
35
36
36
39
45
11. LIST OF TABLES
S.NO.
NAME
Page no.
1
Well-known thermodynamic
cycles
Specific gas constants for a
variety of gases at 300 k
13
Design
Expenses spend on our
project
33
40
2.
3
4.
55
21