STIRLING ENGINE 1

HEAT AND MASS TRANSFER

BMCT3143

STERLING ENGINE

Fakhrurazi Bin Aziz B040910051

Halimaton Basmatu AliB040910081

Mohd Azarul Syazari Bin Che Aziz B040910167

Muhammad Hafiz Bin Abd Rahim B040910092

Nurul Nadia Binti AbdullahB040910227

DUE DATE

25 MEI 2012

LECTURE

Pn. Mahanum Mohd Zamberi

Bachelor of Mechanical Engineering (Thermal-Fluid), Faculty of Mechanical Engineering,

Universiti Teknikal Malaysia Melaka, Durian Tunggal, Melaka.

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Table of Contents

Abstract……………………………………………………………………………………......3

Acknowledgement…………………………………………………………………………….4

Introduction………………………………………………………………………………....5-6

Chapter 1 : Theory…………………………………………………………………………6-8

Chapter 2 : Discussion……………………………………………………………………9-21

2.1. Design Details……………………………………………………………………..9-13

2.1.1. Flow chart…………………………………………………………………….14

2.1.2. Block diagram………………………………………………………………..15

2.2. Design Verification and Testing…………………………………………………...16

2.3. Discussion of Problem Encountered…………………………………………..16-17

2.3.1. Calculation………………………………………………………………..17-22

2.3.2. Application…………………………………………………………………...22

Chapter 3 : Conclusion……………………………………………………………………...22

References……………………………………………………………………………………23

Appendix A : Simple Performance Prediction Method……………………………….24-25

Appendix B : GANTT CHART…………………………………………………………….26

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Abstract

Despite vast research on energy generating engines for a long time, human particularly

the human society had not found the winning formula to create an engine that has 100%

efficiency. One of the closest engine that has a very high efficiency is the Stirling engine,

however it has several downfalls that deters any further application in our life. This report

subsequently is intended to find out the manufacturing process of a Stirling Engine using

recycled materials. The fabrication and assembly of all the parts requires knowledge about

theoretical application on how this engine works. Based on several dimensions and data from

the design, a Pressure-Volume(P-V) diagram had been obtained in order to know about the

theoretical performance of this engine. The engine had also been adds up with an application

in order to better understand its working principle. The application must not be overdone

because our engine design complies with only a small amount of torque so it cannot run on

heavy loads. The Stirling engine was used to remove the electrical load from the internal

combustion engine and to increase the fuel efficiency of the engine. The efficiency of heat

engine was limited by the law of thermodynamics. The powered of stirling engine was

causing by the differences of temperature at the radiator ends. The engine with high efficiency

helps to conserve fossil fuels and other natural resources, reducing global-warming emissions

and pollutants.

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Acknowledgement

The special thank goes to our lecturer, Puan Mahanum bt Zamberi. The supervision

and support was mostly helpful in progression and smoothness of this project. The co-

operation is much indeed appreciated.

Great deals appreciated to all team members that had give the support and struggle to

ensure this project was success. A big contribution and hard worked from all of team member

during eight week is very great indeed. This project would be nothing without the enthusiasm

and imagination from all team members.

Our grateful thank also go to all classmate members that give us support and briefly

idea that helpful in ensure this project was successful. Besides, due to this project there are

many new experiences in working environment which challenges us every minutes. We also

realized the value of working together as a team.

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Introduction

Stirling Engine is one of the reversible thermodynamic cycle application, it is

consisting of four phases that include heat addition (isovolumetric heating), expansion

(isothermal expansion), heat rejection (isovolumetric cooling), and compression (isothermal

compression) which is perform in one complete cycle. They are widely can found in industry

application because of the high thermal efficiency, form a quiet and safe operation, ease of

operation and able to working with form of thermal energy.

Beta Stirling engine is one of the type of sterling engine, it is and improvment from

the alpha type of stirling engine. The new design have eliminated the hot seal failure that can

found in Alpha and the hot power piston is replaced by a displacer for the improvement. Other

design is still the same with. The power piston and the displacer is sharing the same common

cylinder and flywheel/crankshaft. Unlike the piston power, the displacer size need to be small

from the the cylinder so that the friction between the cylinder and the displacer will be lower

and easily to move up and downward.

Figure 1 Beta Sterling Engine

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In Beta Sterling Engine, it has four basic stages to complete one cycle of operation.

First stage is heating process. The heat will be supplied from the bottom of cylinder. Then the

displacer will going upward due to the heat energy being transferred to the atom in a form of

kinetic energy. The collision between the atom with each other and with the wall will produce

pressure that push the displacer. The piston power will also going upward because of the

compression state at upper cylinder. Then the heat being remove, the expand part is contract

because of the kinetic energy is converted into potential energy, the piston will followed the

same motion with the displacer. And once the heat being supplied again, it will repeat the

same process.

Chapter 1 : Theory

Based on SCHMIDT theory and the theory of stirling engine, there are four type of

stirling engine where it is APLHA, BETA, GAMMA and Low Temperature Displacer (LTD).

The theory that used an isothermal calculation for the stirling engine is a Schmidt Theory.

Where it was the simplest method for the Stirling engine. This theory is based on the

isothermal expansion and compression of an ideal gas.

Due to assumption of Schmidt Theory, the performance of engine can be calculated by using

P-V diagram. Where the volume in the engine can be calculated by internal geometry and the

mass of working gass and the temperature are decided. The pressure can be calculate using an

ideal gas method where shown on equation (1).

PV = mRT (1)

Where:

P (Pa) = engine pressure

V (m3) = total momental volume

m (kg) = total mass of working gas

R (J/kgK) = gas constant

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STIRLING ENGINE 7

T (J) = space gas temperature

For the BETA-TYPE stirling engine, there are calculation model.

The equation that involve are;

VE = VSE / 2 (1- cos x) + VDE (2)

Vc = VSE / 2 (1- cos x) + VSC / 2 [ 1-cos(x-dx)] + VDC – VB (3)

Where;

VE = expansion momental volume

Vc = compression momental volume

VSE = swept volume of displacer piston

VSC = swept volume of power piston

dx = phase angle between the diesplacer piston and power piston

In case of stirling engine, the displacer piston and the power piston was located in the same

cylinder. An effective working space was created when the both piston was overlaps then

there are a stroke. The overlap volume (VB) was calculated based on equation (4);

VB = (VSE + VSC) /2 - √V SE2+V SC24

−V SEV SC2

cos dx (4)

So, the total momental volume (V) is

V = VE + Vc + VR (5)

To define the engine pressure;

P = [ Pmean √1– c 2 ] /[ 1-c.cos(x –a)]

= [ Pmin (1+c)] / [ 1-c.cos(x –a)]

= [ Pmax (1-c)] / [ 1-c.cos(x –a)] (6)

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Where;

Pmean = mean pressure

Pmin = minimum pressure

Pmax = maximum pressure

There are several ratios and coefficients are defined as;

t = TC / TE (7)

v = VSC / VSE (8)

XB = VB / VSE (9)

XDE = VDE / VSE (10)

XDC = VDC / VSE (11)

XR = VR / VSE (12)

a = tan ⁻1[ v sin dx /( t + cos dx + 1)] (13)

S = t + 2txDE + 4t XR / (1 + t) + v + 2XDC + 1-2XB (14)

B = √ t 2+2(t−1)v cosdx+v2−2t+1 (15)

c = B /S (16)

where;

TC = compression space gas temperature

TE = expension space gas temperature

VR = regenerator volume

Then, the P – V diagram of Beta-type Stirling engine can be made based on the equation

above.

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Chapter 2 : Discussion

2.1. Design Details

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Figure 2 : Connecting Rod

Figure 3 : Crankshaft Holder

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Figure 4 : Flywheel

Figure 5 : Displacer

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Figure 6 : Displacer Block

Figure 7 : Rendering of Stirling Engine in Solidworks

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Figure 8 : Isometric View

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2.1.1. Flow chart

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NO

START END

Brainstorming

Fabrication of engine block by

using aluminum tin

Selecting material

Engine testing

Assemble all part

Fabrication of crank shaft, connecting

rod, and flywheel by using compact disc.

Fabrication of power piston by using

balloon

Fabrication of displacer

Is the engine running

Is there any air leakage

Can it fit with the

tin

Is it a recycle material

YES

NO

NO

YES

YES

NO

YES

STERLING ENGINELIST OF COMPONENT

AND FUNCTION

ENGINE FRAMETo hold crankshaft and

flywheel together.

FLYWHEELSThe flywheel smoothes

out the pulse of the power stroke and its

inertia allows the crank shaft to continue

rotating.

CONNECTING RODSIt changes the

reciprocating motion of piston into  at

crankshaft. This way connecting rod

transmits the power produced at piston to

crankshaft.

CRANKSHAFTReceives oscillating

motion from connecting rod and

gives a rotary motion to the flywheel

POWER PISTONto amplify the displacer stroke (power stroke)

DISPLACERto move the working gas back and forth

between the hot and cold heat exchangers.

BLOCK LEGTo create room for

heater( candle) compartment

ENGINE BLOCKthe bore of the cylinder

will create pressure difference between

upper and lower compartment

STIRLING ENGINE 15

2.1.1. Block diagram

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2.1. Design Verification and Testing

The verification is intended to check that a product, service, or system meets a set of

initial design requirements, specification and regulations. For the stirling engine project, the

functionality of the design and also the application needs to be evaluated in order to ensure

the project complies with regulations, specifications, or conditions imposed at the start of a

development phase. On this project, there are several benchmarks to be met by the product in

order to ensure it achieves a high standard.

The design of this engine speed is about 100 revolutions per minutes. The speed of this

engine does not necessarily be so high because the application for this system is light. For

ensure the application of this stirling engine project was run smoothly, the light application

was chosen that are shoes polisher. By using the minimal amount of heat, the engine was run

at least with two candles. Due to this application and design, it was safe for domestic usage

that are not be harmful towards costumer, however it was not suitable for children that was

below age of 7 years.

2.2. Discussion of Problem Encountered

This project development was divided into several phase that are multiple types of

problem that should be encounter in order to ensure the stirling engine was working.

The first type of stirling engine that was chosen was Low Temperature Displacer

( LTD)There was several factor that make the design of LTD was failure and it is down,

which is the heat required to run the engine was so high. Due to this requirement, the

displacer bore is quite spacious that in this stirling engine, it cannot been able to create the

sufficient amount of pressure to lift the displacer up. The factor that was affected this type of

stirling engine was diameter of the bore. The big displacer must been fabricate due to this type

of stirling engine where it was quite heavy. The crankshaft design had met a design

complication that caused the piston and displacer movement to be not smooth.

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Got a failure from the first design of stirling engine, the type of Beta stirling engine.

There are also several complication that was faced in terms of design and also application

before it was successful. The dimensions of bore and piston diameter was been ensure suitable

for the compression ratio of the engine. It was important because it has possibility to face with

malfunction of stirling engine. The balloon was inserting in the system that act as power

piston. The balloon has its nature elasticity that was used as advantage for air tight purpose. It

was installing carefully to ensure that it was tight properly. The complexity of the crankshaft

was design properly because it was important for the piston and displacer stroke smoothness.

The fabrication of cooling compartment is quite complicated as to cut the compartment to suit

the block diameter.

2.2.1. Calculation

Given that( from stirling engine):

T = 650c

R= 287.06

VSE = 0.000184 m3 ( volume of piston)

VSC = 1m3

VR = 0.00010053 m3

dx = 900c

Tc = 65 0c

Te = 600c

X = 0 ( ideal stirling engine)

t = 0.8 sec (complete one cycle)

VE = Πr2 h = π (3x 10-2)2 (6.5x10-2) = 0.1838x10-3 m3

VC = Πr2 h = π (3x 10-2)2 (4.5x10-2) = 0.127x10-3 m3

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V = VE + VC + VR = 0.000184 + 0.000127 +0.00010053 = 0.000412m3

To find the pressure on the stirling engine,

PV= m RT,

ρ = m / V,

To find mass expansions of gas,

ρ = mE / V

From table 2;

T1 =350c, ρ = 1.1455 kg/m3

So, ρ = mE / VE

1.1455 kg/m3 = mE / (0.1838x10-3 m3)

mE = 0.0002105KG

To find mass compression of gas,

ρ = mc / Vc

From table 2;

T1 =350c, ρ = 1.1455 kg/m3

So, ρ = mc / Vc

1.1455 kg/m3 = mc / (0.127x10-3 m3)

mc = 0.0001457KG

so, the pressure are;

Pmax (Pexpansion) : PVE = mE RT

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(Pmax)(0.1838 X10-3) = (2.105 X 10-4)(287.06)(65+ 273)

Pmax = 111.13kPa

Pmin (Pcompression) : PVC = mC RT

(Pmin)(0.127x10-3) = (1.4574 X 10-4)(287.06)(65+ 273)

Pmin = 111.35kPa

Pmean = 111.13 kPa+111.35 kPa

2 =111.24kPa

After that, to find the overlap volume;

VB = (VSE + VSC) /2 – √V SE2+V SC2

4−V SEV SC

2 cos dx

VB = (0.000184+ 1) /2 – √ ( 0.000184 )2+(1)2

4−

(0.000184 )(1)2

cos (90)

VB = 9.2 x 10-5m3

Engine pressure;

P = [ Pmax (1-c)] / [ 1-c.cos(x –a)]

C = B / S

B = √ t 2+2(t−1)v cosdx+v2−2t+1

B = √ (0.8 )2+2 (0.8−1 ) (0.000412 ) cos (90 )+(0.000412)2−2(0.8)+1

B = 0.2

S = t + 2txDE + 4t XR / (1 + t) + v + 2XDC + 1-2XB

S = 0.8 + 2(0.8)(0) + 4(0.8)(0) / (1 + 0.8) + 0.000412 + 2(0) + 1-2(0)

S = 1.800412

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C = B / S

C = 0.2 / 1.800412 = 0.11109

t = TC / TE = (65/ 60) = 1.08

a = tan ⁻1[ v sin dx /( t + cos dx + 1)]

a = tan ⁻1[ (0.000412) sin (900) /( 1.08 + cos (900) + 1)] = 0.01135

P = [111.13x103 (1-0.11109)] / [ 1-0.11109cos(0 –0.01135)] = 111.12 kPa

After that, by using the simple performance prediction method for stirling engine (ver. 1.8J,

koichi Hirata (31 March, 1998)).

Step to used;

1) The mean pressure, a swept volume, gas temperature, and a type of working gas was

added on the calculated condition.

2) Due to this stirling engine, it was operate by using the design and permitted value.

3) After complete the fill in the blank of the table, the button start was click.

4) The maximum output power and the engine speed was calculate when the engine was

at maximum output power due to the experimental equations.

The result that was get from these experimental equations is;

Viscosity coefficient, vlim = 1.74E-5 m2/s

Gas constant, R = 287.3 J/kgK

Engine speed, N = 11552.7 rpm

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Graph 1 : P – V DIAGRAM

Based on the Graph 1 for the stirling engine that had been plotted due to the

calculation that had done, the amount volume of compression are 0.127x 10-3m3. While

volume of expansion on this stirling engine are 0.1838x10-3m3. This is due to the volume

displacement that involve during the stirling engine cycle. The total volume of the can that

was assumed as cylinder is 3.6757 x 10-4 m3. The heights of the cylinder are 13 cm and the

diameters of the can are 6cm. The volumes of the displacer that are on the cylinder are half of

the height of the cylinder where it was 6.5 cm. Amount of pressure that involve on this stirling

engine is due to the volume of expansions and compression. Pressure at expansion are 111.13

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kPa while at compression, the pressure was at 111.35 kPa. The heating process was happen at

pressure 1 until pressure 2. Where between 111.13kPa until 111.35kPa. The expansion

process was happen during 111.35 kPa until 111.24 kPa. At this situation, the work done of

expansion was out while the flow rate was in the system. On the cooling process, the pressure

from 111.24 kPa was drop until 111.12 kPa. The compressions on the system were happen

from pressure 4 to pressure 1.

2.1.1. Application

By manipulate the stirling engine system and translate it into shoes polisher as the

application. How the shoes polisher is working? By manipulate the heat being transfer to the

system, the air in the cylinder will expend due to the pressure increased. Once the pressure

increased, it will push away the displacer upward and make a half cycle. At upper cylinder

included power piston is placed and ice that will make a temperature difference. Because of

the low temperature being supplied, the pressure at the power piston will contract due to the

kinetic energy being transferred into potential energy. The power piston will push away the

displacer to the downward movement and make another half cycle. The complete cycle will

make a rotational movement and transfer to the crank shaft and then transfer to the span that

will act as shoes polish.

Chapter 3 : Conclusion

From the project that have been build, many type of properties need to be considered

to perform a good result in this project. From the fabrication process, each of the dimensions

need to be precise or otherwise the project will not running at all. This is due to the friction

factor between the displacer and the tin, temperature difference that not meet specification

that have been stated and maybe will form a leakage place that will lowered the performance

of the engine. Engine that had high efficiency is the one that can manipulated the lower

temperature an in this project it can run by using at least with two candle.

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References

[1] LARRY KEEGAN'S EXPERIMENTS WITH STIRLING ENGINES. Retrieved from

http://www.keegan.org/larry/stirling.html

[2] The Stirling engine. Retrieved from http://www.pha.jhu.edu/~broholm/l39/node5.html

[3] Simple Performance Prediction Method for Stirling Engine. Retrieved from

http://www.bekkoame.ne.jp/~khirata/academic/simple/simplee.htm

[4] SCHMIDT THEORY FOR STIRLING ENGINES. Retrieved from

http://www.bekkoame.ne.jp/~khirata/academic/schmidt/schmidt.htm

[5] STIRLING ENGINES. Retrieved from http://www.robertstirlingengine.com/theory.php

[6] Beta Type Stirling Engines. Retrieved from

http://www.ohio.edu/mechanical/stirling/engines/beta.html

[7] Stirling engine http://en.wikipedia.org/wiki/Stirling_engine

[8] Beta And Gamma Engine Phase Angle Calculation. Retrieved from

http://newenergydirection.com/blog/2008/11/beta-and-gamma-engine-phase-angle-

calculation/

[9] Innovative Rotary Displacer Stirling Engine: Sustainable Power Generation for Private

and Fleet Vehicle Applications. Retrieved from

http://scholar.lib.vt.edu/ejournals/JOTS/v37/v37n2/foster.html

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Appendix A : Simple Performance Prediction Method [3]

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Appendix B : GANTT CHART

( TIME DURATION OF PLANNING STIRLING ENGINE PROJECT)

ACTIVITIES

DURATION

22/3 – 29/3 29/3 – 5/4 5/4 – 12/4 12/4 – 19/4 19/4 – 26/4 3/5 – 10/5 17/5 – 24/5

24/5 – 25/5

IDENTIFYING THE PROBLEM

BRAINSTORMING AND PLANNING THE PRODUCT OF STIRLING ENGINEPROCESS DESIGN AND DEVELOPMENT

DETAILED TECHNICAL DESIGN

DESIGN FUNCTIONALITY AND EFFECTIVENESS

PRODUCT DESIGN ANALYSIS

PRESENTATION

REPORT

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