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TRUBA COLLEGE OF ENGINEERING & TECHNOLOGYINDORE (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

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TRUBA COLLEGE OF ENGINEERING & TECHNOLOGYINDORE (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: GUIDED BY: PROF. MRS. SUMAN SHARMA Asst.Prof .MR. VISHAL ACHWAL

(HEAD OF DEPARTMENT )

DEPARTMENT OF MECHANICAL ENGINEERING

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TRUBA COLLEGE OF ENGINEERING & TECHNOLOGYINDORE, (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 Prof. Suman Sharma Madam Project Guide Head of DepartmentMechanical Engg Dept. TCET Mechanical Engg Dept. TCET

DirectorTCET, INDORE

DEPARTMENT OF MECHANICAL ENGINEERING

TRUBA COLLEGE OF ENGINEERING & TECHNOLOGY

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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 EXAMINERDate- Date-

DEPARTMENT OF MECHANICAL ENGINEERING

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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

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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.

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CONTENT

Page No.

1. Introduction 5 1.1 Thermodynamic cycle 6 1.2 Heat and Work 7 1.3 Well known thermodynamic cycle’s 12 1.4 History of Stirling Engine 14

2. Literature Review 15 2.1 Presentation of Stirling Engines 18 2.1.1 Stirling thermodynamic cycle 18

2.2 Analysis of the Stirling-Cycle Engine 20 2.2.1 Work done by an ideal Stirling-cycle 20 2.2.2 Heat flow in an ideal Stirling-cycle 22 2.2.3 Efficiency of an ideal Stirling-cycle 23 2.2.4 Actual Stirling Engine 24

2.3 Engine configurations 25 2.3.1 Alpha Stirling 26 2.3.2 Beta Stirling 28 2.3.3 Gamma Stirling 30

2.4 Technical complexity of topic 31

3. Model Description 32 3.1 Design & Drawing 33

3.1.1 Stand & Cylinder 34 3.1.2 Piston 35 3.1.3 Fan Acting as Crank 35 3.1.4 Connecting Rod & Link 36 3.1.5 Assembly in Pro-Engineer software 36

3.2 Methodology 37 3.2.1 Assembly & Procedure 37 3.2.2 Our Stirling Engine Mode 39 3.3 Expenses 40

4. Advantages 41

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Page No.

5. Disadvantages 43 5.1 Problems And Iteration 44 5.2 Causes Of Failure 446. Analyze From Economic Point 457. Applications of The Stirling Power 48 7.1. Cars 48 7.2. Submarine. 48 7.3. Nuclear power 48 7.4. Solar Energy 49 7.5. Aircraft engines 49.8. Conclusion 509. References 5210. List of Figures 5411. List of Tables 55

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INTRODUCTION

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INTRODUCTION

1.1 Thermodynamic cycle

Thermodynamics

HEAT FLOW: FIGURE: 1

State:Equation of stateIdeal gas · Real gasPhase of matter · EquilibriumControl volume · Instruments

Processes:Isobaric · Isochoric · IsothermalAdiabatic · Isentropic · IsenthalpicQuasistatic · PolytropicFree expansionReversibility · IrreversibilityEndoreversibility

Cycles:Heat engines · Heat pumpsThermal efficiency

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Material properties:

Specific heat capacity 

Compressibility 

Thermal expansion 

Potentials:

Internal energyEnthalpyHelmholtz free energyGibbs 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

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temperature entropy diagram, the clockwise and counterclockwise directions indicate power and heat pump cycles, respectively.

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.

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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:

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Ideal Stirling cycleFIGURE: 3

Actual and ideal overlaid, showing difference in work output

FIGURE: 4

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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) heat-addition. The compressed air flows back through the regenerator and picks-up heat on the way to the heated expansion space.

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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.

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Some example thermodynamic cycles and their constituent processes are as follows:

CycleProcess 1-2

(Compression)

Process 2-3(Heat

Addition)

Process 3-4(Expansion)

Process 4-1(Heat

Rejection)Notes

Power cycles normally with external combustion - or heat pump cycles:

Bell Coleman

adiabatic isobaric adiabatic isobaricA reversed

Brayton cycle

Carnot isentropic isothermal isentropic isothermal

Ericsson isothermal isobaric isothermal isobaricthe second

Ericsson cycle from 1853

Rankine adiabatic isobaric adiabatic isobaric Steam engine

Scuderi adiabaticvariable pressure

and volumeadiabatic isochoric

Stirling isothermal isochoric isothermal isochoric

Stoddard adiabatic isobaric adiabatic isobaric

Power cycles normally with internal combustion:

Brayton adiabatic isobaric adiabatic isobaric

Jet enginesthe external combustion

version of this cycle is known as

first Ericsson cycle from 1833

Diesel adiabatic isobaric adiabatic isochoric

Lenoir isobaric isochoric adiabatic

Pulse jets(Note: Process 1-2 accomplishes both the heat

rejection and the compression)

Otto adiabatic isochoric adiabatic isochoricGasoline / petrol

engines

Known Thermodynamic Cycles: TABLE: 1

1.4 HISTORY:

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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 thereis 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

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LITERATURE REVIEW

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2. LITERATURE REVIEW

The Stirling Engine is one of the hot air engines. It was invented by RobertStirling (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

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The original patent by Reverend Stirling was called the "economizer", for itsImprovement 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.

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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

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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.

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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=-∮ p . dV

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=-[ ∫V 1

V 2

p . dV +∫V 3

V 4

p . dV ¿¿ (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:

∫VA

VB

p . dV=∫VA

VBmRT

VdV=mRTln(VB

VA ) (4.2)

so that by substitution of Equation 4.2 into Equation 4.1,we can evaluate the work integral:

W =−¿

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:

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W =−mRln (V 2V 1

)¿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)

AirAmmonia

Carbon dioxideHelium

HydrogenNitrogenPropaneSteam

319.3488.2188.92077.04124.2296.8188.6461.5

Specific gas constants: TABLE: 2

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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:

Q=∫T dS

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= ∫S 1

S 2

T H dS

This integral can be most easily evaluated by considering the First Law ofThermodynamics in the form:

QH=∫U 1

U 2

dU +¿¿ ∫V 1

V 2

p . dV

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=∫U 1

U 2

dU +¿¿ ∫V 1

V 2mRV

T H dV = 0 + ∫V 1

V 2mRV

T H dV

giving:

QH = mRTH ln (V 2V 1 ) (4.4)

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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.

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 (V 2V 1 ) (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.

ƞƞ

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 Stirling-cycle 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

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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.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.

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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). Theregenerator 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 theRegenerator, 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.

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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

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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.

Transfer: At this point, the gas has expanded. Most of the gas

is still in theHot 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

Contraction: Now the majority of the expanded gas is shifted to the cool piston cylinder. It cools and

contracts, drawing both pistons up.

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.

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2.3.2 Beta Stirling

The Beta configuration is the classic Stirling engine configuration and hasenjoyed 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

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Expansion: At this point, most of the gas in the system is at the heated end

of the cylinder. The gas heats and expands driving the power piston

outward.

Transfer: At this point, the gas has expanded. Most of the gas is still

located in the hot end of the cylinder. Flywheel momentum carries 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.

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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 takeplace 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.

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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

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MODEL DESCRIPTION

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3.1 DESIGN AND DRAWING

MATERIAL LENGTH (mm)

DIAMETER(mm)

THICKNESS(mm)

CYLINDER

1 TIN 200 80 1

2 TIN 105 50 1

PISTON(HOLLOW

)

1 HARD FIBRE 25 78 3

2 HARD FIBRE 15 48 1

LINK 1 ALUMINIUM 250 3 SOLID2 ALUMINIUM 300 3 SOLID3 ALUMINIUM 270 3 SOLID4 WOOD 300 25* 8

BEARING STAINLESS STEEL

6000z

(Note: * Represents rectangular section width)DESIGN: TABLE: 3

Clearance volume, V1= (D1)2 L1 = 1.231 x 10(-5) m3

V2 = 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

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)

CRANKSHAFTMATERIAL CRANK RADUIS

1 (mm)PLASTIC 22

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PRO-ENGINEEER DESIGN & SPECIFICATION

3.1.1 STAND & CYLINDER

Criteria: Good thermalconductivityEasy machinableMaterial preferred: Wood, Tin

Processing: Mig weldingFor sealing ,M-SealInternal grinding throughSand paper

FIGURE:15

HINGED SUPPORT: FIGURE:16

LINK: FIGURE: 17

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3.1.2 PISTON

Criteria: Light weightedMaterial preferred:Hard fiberProcessing: Sealing onboth side Turning on surface Finishing by lathemachine

FIGURE:18

3.1.3 FAN ACTING AS CRANK

Criteria: Light weighted

Material preferred: FiberProcessing: Bending to the required crank radius

FIGURE:19

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3.1.5 ASSEMBLY IN PRO-Engineer software:

ASSEMBLY: FIGURE: 21

3.1.4 CONNECTING ROD & LINK

Criteria: Light weighted ,Fatigue resistanceMaterial preferred: AluminumFIGURE: 20

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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.

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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 .

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3.2.2 OUR STIRLING ENGINE MODEL

FIGURE: 22

CONTINOUS ROTATION OF FAN with small amount of HEAT by CANDLE.

BY THE use of STIRLING Cycle concept.

Fan Acting as Crank

Cylinder 1

Cylinder 2

Flame

Hinged support

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3.3 EXPENSES SPEND ON OUR PROJECTQUANTITY 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

BEARING 45

OTHER - 50

TOTAL 695/-

EXPENSES: TABLE: 4

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ADVANTAGES

4. ADVANTAGES

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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 ).

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DISADVANTAGES

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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.

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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 aStirling 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

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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 controland 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 withsustainable 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.

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APPLICATIONS

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7.APPLICATIONS OF THE STIRLING POWER

7.1. Cars

In the ages of 1970s and 1980s several automobile companies like “GeneralMotors” 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 arefour 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.

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7.4. Solar Energy

Placed at the focus of a parabolic mirror a Stirling engine can convert solarEnergy 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 enginesStirling 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.

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CONCLUSION

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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 theother 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 .

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REFERENCE

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9. REFERENCE

http://www.kockums.se/News/photostock/photo.htmlhttp://www.moteurstirling.com/alpha.htmwww.stirlingenergy.com/solar_overview.htmwww.stirlingenergy.com/images.asp?Type=solar

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10. LIST OF FIGURES

S.NO. FIGURE NAME Page no.

1. Heat Flow 62. P-v diagram of a thermodynamic

cycle8

3. Ideal stirling cycle 104. Actual and ideal overlaid, showing

difference in work output10

5. Actual performance 116. Sketch of Robert Stirling of his invent 147. Earliest stirling engine 168. Distinct processes 189. Actual stirling engine 24

10. Alpha stirling 2611. Alpha type stirling 2612. Beta stirling 2813. Gamma engine’s configuration 3014. A model of a four-phase Stirling cycle 3115. Stand & cylinder 3416. Hinged support 3417. Link 3418. Piston. 3519. Fan acting as crank. 3520. Connecting rod 3621. Assembly in pro-engineer software 3622. Our stirling engine model 3923. Stirling engine working on a cup of

coffee45

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11. LIST OF TABLES

S.NO. NAME Page no.

1 Well-known thermodynamic cycles

13

2. Specific gas constants for a variety of gases at 300 k

21

3 Design 334. Expenses spend on our

project40