project report_final

DEVELOPMENT OF SOLAR OPERATED STIRLING ENGINE
Darshan institute of Engineering and Technology Page 1
Chapter 1- INTRODUCTION
The stock of conventional fuel is limited and also the cost is high. The use of conventional
fuel also increases. So we have to find optional source of energy. The solar energy is
renewable energy and also has benefits like the low running and maintenance cost and also
pollution free. In India 300 days are clear sunny days in every year. India has a potential to
produce 30 MW of energy per sq.km. So it is better to use solar energy as a fuel.
Solar energy is more attractive renewable energy sources that can be used as an input
energy source for heat engines. So, any heat energy source can be used with the Stirling
engine. The solar radiation can be focused onto the displacer hot-end of the Stirling engine,
thereby creating the solar-working prime mover. The direct conversion of solar working
into mechanical working reduced both the cost and complexity of prime mover. According
to theory, the principal advantages of Stirling engines are their use of an external heat
source and high efficiency. Stirling engines are able to use solar energy because of cheap
source of energy. Since during two-thirds of the day, solar energy is not available, solar
hybrids are needed.
Since the combustion of the engine is continuous process in Stirling engine, it can burn fuel
more completely and able to use all kinds of fuel with various quality. According of its
simple construction and its manufacture being make the equal as the reciprocating internal
combustion engine, and when produced in a high number of units per year, the Stirling
engine would be obtain the economy of scale and could be built as a cheap working source
for developing countries. For the range of solar electric generation in 1–100 kWe, the
Stirling engine was considered to be the cheapest [1]
. However the efficiency of the Stirling
engine may be low, reliability is high and costs are low. Moreover, simplicity and reliability
are keys to a cost effective solar operated Stirling generator.
A Stirling engine is one of the examples of a broad class of heat engines which are devices
designed to convert thermal energy into mechanical energy. The internal combustion, or
gasoline, engine in an automobile is the example of the heat engine. The gasoline engine
uses the combustion of fuel inside a limited volume, whereas the Stirling engine uses an
external heat source to heat the working volume. The heat source can come from burning

fossil fuels (such as gasoline), solar energy, decaying plant substance, or whatever is
available[2]
. In fact, all the Stirling engine are requires to operate is a high temperature
difference. It is possible to run a Stirling engine by cooling one part of the engine under the
atmospheric temperature. The gas inside the cylinder of a Stirling engine is not burned or
consumed. So, in compare to the internal combustion engine, the Stirling engine does not
require an exhaust or an intake. If a clean (green) external heat source is used into the
Stirling engine, it can be an ecofriendly alternative to engines that burn and emit
hydrocarbons and other pollutants. Stirling engines also has a benefits which is limits noise
pollution because they do not require intake and exhaust valves which usually are the main
source of engine noise. Though, Stirling engines that would be suitable for automobile use
are highr, heavy, and more costly than conventional internal combustion engines. Besides,
Stirling engines require some time to heat up before they starts and the output of the engine
can‘t be changed quickly for quick acceleration and deceleration. So Stirling engines have
not yet found use in the automotive industries; they have been used as a submarine engine.
Freshly, there has been a rebirth of interest in Stirling engines as the demand for more fuel
efficient and clean engines continues to increase.
1.1. General principles
Stirling engines are mechanical devices working ideally on the Stirling cycle, or its
modifications, in which compressible fluids, such as air, hydrogen, helium, nitrogen or even
vapors, are used as operational fluids. The Stirling engine offers probability for having high
efficiency engine with less exhaust emissions in parallel with the internal combustion
engine. The earlier Stirling engines were huge and inefficient. However, over a period of
time, a number of new Stirling engine have been developed to improve the faults.
The Stirling engine operates by repeatedly totally a sequence of four steps. Each step in the
sequence is reversible and together they form the Stirling cycle. With help of understand
each of the four steps in the Stirling cycle consider two gas filled cylindrical pistons whose
chambers are connected by a thin tube as pictured in Figure 1.1.1.
The left piston has temperature TH and the right piston has temperature TC In the center of
the tube that connects the two chambers is a wire mesh that will be used to temporarily
store heat as described. For each step in the Stirling cycle of Figure 1.1.1 will be mapped to

curves on a pressure-volume plot of the Stirling cycle shown in Figure 1.1.2. The four steps
of the perfect Stirling cycle are [3]
:
(1-2) the gas in the engine is expanded at the steady temperature TH. The left piston moves
down and the right piston is fixed. In ordered to maintain a steady temperature the gas must
absorb heat QH from the source (Isothermal expansion - Figure 1.1.1a, path 1-2 in Figure
1.1.2).
(2~3) At steady volume V2, the temperature of the gas is lowered down from TH to TC. The
left piston is compressed and the right piston expanded so the total volume remains fixed.
The hot gas is passed from the left chamber to the right chamber. As the gas passes through
the split tube it delivers heat Q to the wire mesh. (Steady volume heat removal – Figure
1.1.1b, path 2-3 in Figure1.1.2)
(3-4) the gas is compressed at steady temperature TC. The right piston is compressed and
the left piston is remains equal. To maintain a steady temperature the gas releases heat QC
to the thermal source at TC. (Isothermal compression – Figure 1.1.1c, path 3-4 in Figure
1.1.2)
(4-1) at steady volume V1, the temperature of the gas is increased from TC to TH. The left
piston is expanded and the right piston compressed so that the total volume remains steady.
The cold gas is passed from the right chamber to the left chamber. As the gas passes into
the narrow tube it recovers the heat Q stored in the hot wire mesh. (Steady volume heating
– Figure 1.1.1d, path 4-1 in Figure 1.1.2) .

Fig.1.1.1 Dual piston Stirling engine at four different stages Stirling cycle
Stirling engine at various stages of the Stirling cycle. In any real Stirling engine the
idealized Stirling cycle cannot be made. The four steps are fuzzy together and the cycle on
a PV-diagram appears elliptical. This type of engine has one little sealed piston, called the
working piston, and one higher loose fitting known as displacer piston. The role of the
displacer piston is simply to move, or displace, working gas in the engine back and forth
between a heated lower part and the upper cooled part. In the design pictured in Figure, the
lower plate is heated with the help of flame and the upper plate is cooled with the help of
water or the ambient surroundings. The two pistons are linked together such that their
movements are making 90o
out of phase. That is, when the working piston is either at its
maximum or minimum height and moving gently, the displacer piston is at its halfway
point and moving at its higher speed. At position 1 of Figure, the displacer piston is in the
upper cold part which forces the working gas to occupy the hot part and be at temperature
TH. Heat is added pressure to the gas and it expands forcing the working piston to move
upwards (path 1-2 in Figure 1.1.2). At position 2 the working piston is at its maximum
height (the gas has its maximum volume V2) and is moving very gradually approximating
the steady volume path 2~3 in Figure 1.1.2. The displacer, on the other side, is moving into

the hot part causing the gas to move to the cold part. In this design, the displacer itself plays
the role of the wire mesh of Figure 1.1.1 by momentarily storing energy taken from the gas
as it cools from TH to TC. At position 3, because all of the gas is in the cold part, it contracts
(heat is removed from the gas) causing the working piston to slide down (path 3-4 in Figure
1.1.2). At position 4, the working piston is totally compressed (minimum volume V1) and is
moving gradually. The displacer piston is moving upwards forcing the gas into the hot part.
As the cool gas passes by the displacer it recovers the heat that was temporarily stored in
the displacer (path 4-1 in Figure 1.1.2). At the completion of this process the state of the
Stirling engine returns to 1 and the cycle repeats continuously.
Fig.1.1.2 Motion diagram of gamma engine of Stirling engine
The new Stirling engine is more efficient than the early engines and can required any high
temperature heat source. Hence, most sources of heat can working it, including combustion
of any combustible material, rice husk or the like, biomass methane and solar energy.
According to principle, the Stirling engine is simple in design and construction, and can be
operated very easy.
Direct solar operated Stirling engines may be of great interest to countries because of solar
energy is available in unlimited quantity. To use direct solar energy, a solar concentrator
and absorber must be used in the engine system.

The Stirling engine could be used in many applications like:
1. multi-fueled characteristic is required;
2. A very good cooling source is available;
3. Quiet operation is required;
4. Relatively low speed operation is permitted;
5. Steady working output operation is permitted;
6. Slow changing of engine working output is permitted;
7. A long warm-up period is permitted.
1.2. TYPES OF STIRLING ENGINE:
Various machine parts have been combined to provide the Stirling cycle. The cycle
provides a steady-volume process during the transfer of working fluid between the hot and
cold part of the engine, and provides a steady-temperature heating and cooling process
during compression and expansion. The compression and expansion process of the cycle
generally takes place in the cylinder (called working cylinder) with a piston (called working
piston). A displacer piston (simply called displacer) shuttles the working fluid back and
forth in the heater, regenerator, and cooler at steady volume. As shown in Fig. 1.1.2, a
displacer that moves to the cold part forcing the working fluid from the cold part causing it
to flow to the hot part and vice versa. Three different types of engine available, namely the
alpha-, beta-, and gamma-engines, are commonly used. Each engine has the equal
thermodynamic cycle but has different mechanical design characteristics.
In the alpha-engine a displacer is not used. Two pistons, called the hot and cold pistons, are
used on side of the heater, regenerator, and cooler. These pistons move uniformly in the
equal direction to provide steady-volume heating or cooling processes of the working fluid.
When all the working fluid has been passed into one cylinder, one piston will be fixed and
the other piston moves to expand or compress the working fluid. The expansion work is
done by the hot piston on the other side the compression work is done by the cold piston [4]
.
In the beta-engine, a displacer and a working piston are incorporated in the equal cylinder.
The displacer moves between the hot part and the cold part of the cylinder through the
heater, regenerator, and cooler. The working piston, located at the cold part of the cylinder,

compresses the working fluid when the working fluid is in the cold part and opens the
working fluid when the working fluid is moved into the hot part [4]
.
Fig.1.2.1Three basic mechanical engine of Stirling engine.
The gamma-engine uses separated cylinders for the displacer and the working pistons, with
the working cylinder connected to the displacer cylinder. The displacer moves working
fluid between the hot part and the cold part of the displacer cylinder through the heater,
regenerator, and cooler. In this engine, the working piston both compresses and expands the
working fluid. The gamma-engine with double-acting piston arrangement has actually the
highest possible mechanical efficiency. This engine also shows good self-pressurization [7]
.
Hence, the engine cylinder should be designed in vertical type rather than horizontal in
order to reduce disadvantage of bushing friction [4]
.
1.3. LOW TEMPERATURE DIFERENTIAL ENGINE:
A low temperature differential (LTD) Stirling engine can be o with small temperature
difference between the hot and cold ends of the displacer cylinder [9]
. This is different from
other types of Stirling-cycle engines, which have a greater temperature difference between
the two ends, and therefore the working developed from the engine can be higher.
LTD engines have two designs. The first design uses single-crank operation where only the
working piston is connected to the flywheel, called the Ringbom engine. This type of
engine, that has been showing more frequently, is based on the Ringbom principle. A short,
high-diameter displacer rod in a machined fitted guide has been used to replace the
displacer connecting rod [7]
. The second design is called a kinematic engine, where both the

displacer and the working piston are connected to the flywheel. The kinematic engine with
a normal 900
phase angle is a gamma-engine [7]
.
Some characteristics of the LTD Stirling engine [7]
are as given below:
1. Displacer to working piston swept volumes ratio is high;
2. Diameter of displacer cylinder and displacer is high;
3. Displacer is less;
4. Effective heat transfer surfaces on both end plates of the displacer
5. Displacer stroke is small;
6. Dwell period at the end of the displacer stroke is rather longer than the
normal Stirling engine.
7. Operating speed is low.
LTD Stirling engines gives value as demonstration units, but they immediately become of
interest when considering the possibility of working production from many low temperature
waste heat sources in which temperature is less than 1000
C [6]
.
According to calculation using the Carnot cycle formula shows that an engine operating
with the source temperature of 1000
C and the sink temperature of 350
C gives the maximum
thermal efficiency of about 17.42%. If an engine could be reach for achieving 50% of the
maximum thermal efficiency, it would have about 8.71% overall Carnot efficiency. Even
the calculated thermal efficiency rather low, but LTD Stirling engines could be used with
free or low temperature sources. This engine should be selected if the low cost engines are
put into consideration.
However the particular working developed by LTD Stirling engines is low, lightweight and
cheap materials such as plastics can be used as the engine parts.
1.3.1. PRINCIPLE OF LTD STIRLING ENGINE:
The hot air engine is a simple type of engine that uses a compressible fluid as the working
fluid. Because of the working fluid is in a closed system, there are no problems with
contamination and working fluid prices. Heat transfer to the working fluid is most
important. Very High mass flow is needed for good heat transfer. The working fluid should

be that of low viscosity to reduce the pumping losses. Using higher pressure or lower
viscosity, or combinations, could reduce the high mass flow required.
The Stirling engine could ideally be a very efficient engine in upgrading from heat to
mechanical work with the Carnot efficiency. The thermal boundary of the operation of the
Stirling engine based on the material used for construction. Engine efficiency ranges from
about 30 to 40% resulting from a typical temperature range of 923–1 073 K, and a normal
operating speed range from 2000 to 4000 rpm [5]
.
1.3.2. STIRLING CYCLE:
The ideal Stirling cycle has three advantages. First, the thermal efficiency of the cycle with
ideal regeneration is equal as the Carnot cycle. During the transfer strokes, the regenerator,
which is temporary energy storage, rapidly absorbs and releases heat to the working fluid
which is passing through. So, the quantity of heat taken from the external heat source is
reduced. This results in improving the thermal efficiency(Fig. 1.3.2.1).
The second advantage, over the Carnot cycle, is obtained by adding of two isentropic
processes with two steady-volume processes. This results in increasing the p–v diagram
area. Therefore, a reasonable amount of work from the Stirling cycle is obtained without
use very high pressures and high swept volumes, as in the Carnot cycle.
Fig.1.3.2.1 Stirling and Carnot cycle

The comparison of Stirling cycle with the Carnot cycle between the equal given limits of
pressure, volume, and temperature, is shown in Fig. 1.3.2.1. The shaded areas 2C-2-3 and
1-4C-4 indicate the extra work available by replacing two isentropic processes with two
steady-volume processes. The Carnot cycle isothermal processes (1-2C and 3-4C) are
respectively, extended to process 1–2 and 3–4. The amount of work is increased in the
equal proportion as the heat supplied to and rejected from the Stirling cycle [10]
.
The third advantage has recently been found. Compared with all reciprocal piston heat
engines working at the equal temperature limits, the equal volume ratios, the equal mass of
ideal working fluid, the equal external pressure, and mechanism of the equal overall
effectiveness, the ideal Stirling engine has the maximum possible mechanical efficiency [7]
.
These three advantages that the Stirling engine is a theoretical equivalent of all heat engines
[3]
.
Stirling engine operation Isothermal compression process 1–2 (heat transfer from working
fluid at low temperature to an external sink): After the displacer has pushed back the
working fluid into the cold part of the cylinder, where it was cooled, it was then held steady
at its top dead center (TDC) (Fig. 1.3.2.1). This indicated the state 1 and the pressure at this
state is P1. The working piston is then being pushed from bottom dead center (BDC) to
TDC by flywheel momentum helped by partial vacuum created by the cooling working
fluid.
The working fluid is in the cold part and is under compression by working piston, which is
approaching TDC, and compressing working fluid from 1 to 2 at steady temperature. The
work done on the working fluid indicated by the area under the process 1–2.
Steady-volume heating process 2–3 (heat transfer to the working fluid from regenerator):
The displacer is moving from TDC to BDC and transferring working fluid from the cold
part to the hot part, while the working piston remains steady at its TDC, increases in
pressure as a result of expanding working fluid. The displacer is pushing the working fluid
into the hot part, passing through a regenerator which has stored heat, and already a certain
amount is being heated. Heat given up by the regenerator raises the temperature and
pressure of the working fluid from 2 to 3 at steady volume. Heat stored in the regenerator is
added to the working fluid.

Isothermal expansion process 3–4 (heat transfer to the working fluid at high temperature
supplied by an external source): After the displacer has pushed back all the working fluid
into the hot part, with a corresponding increase in pressure to the maximum position, it is
then kept at rest at its BDC. The working fluid is in the hot part and is expanding to
pressure P4, while a steady temperature process 3–4 is maintained applied at the hot part.
The working piston is being pushed from TDC to BDC by the increased pressure, and is
applying force to the flywheel, thus creating mechanical energy. This energy will be
utilized throughout the remaining processes of the cycle. The work done by the working
fluid is known by the area under process 3–4.
Steady-volume cooling process 4–1 (heat transfer from the working fluid to the
regenerator): After the working piston has reached its BDC and has supplied its energy to
the flywheel, it remains stationary and is ready to travel back to TDC under flywheel
momentum and the sucking action of the partial vacuum created by the falling pressure.
Fig. 1.3.2.2 Stirling engine operation

The displacer is moving from BDC to TDC and is transferring working fluid to the cold
part where the pressure will fall and a partial vacuum is created, through the regenerator,
causing a fall in temperature and pressure of the working fluid from 4 to 1 at steady
volume. Heat is passed from the working fluid to the regenerator.
1.3.3. Efficiency of Stirling cycle
Fig 1.3.3.1 Stirling cycle on P-V and T-S diagram

(a) The air is compressed isothermally from state 1 to 2 (TL to TH).
(b) The air at state-2 is passed into the regenerator from the top at a temperature
T1. The air passing through the regenerator matrix gets heated from TL to TH.
(c) The air at state-3 expands isothermally in the cylinder until it reaches state-4.
(d) The air coming out of the engine at temperature TH (condition 4) enters into
regenerator from the bottom and gets cooled while passing through the
Regenerator matrix at steady volume and it comes out at a temperature TL,
at condition 1 and the cycle is repeated.
(e) It can be shown that the heat absorbed by the air from the regenerator matrix
during the process 2-3 is equal to the heat given by the air to the regenerator
matrix during the process 4-1, then the exchange of heat with external source
will be only during the isothermal processes.
Now we can write, Net work done = W = Qs - QR
Heat supplied = QS = heat supplied during the isothermal process 3-4.
Heat rejected = QR = Heat rejected during isothermal compression process 1-2

Now,
And,
Thus the efficiency of Stirling cycle is same as that of Carnot cycle efficiency when both
are working with the equal temperature limits. It is not possible to obtain 100% efficient
Regenerator and so there will be always 10 to 20 % loss of heat in the regenerator, which
lowered the cycle efficiency. Considering regenerator efficiency, the efficiency of the cycle
can be written as,

Chapter 2- LITERATURE REVIEW
Pongsakorn Kerdchang, Maung MaungWin, and Sombat Teekasap, of Scientific Research
Center, South-East Asia University, presented a research paper on “Development of a new
solar thermal engine system for circulating water for aeration.” At Thailand. They
concluded that:
Uses low temperature technology, the number of Stirling engines and designs, including the
engines development, are provided and discussed. The extent of research on solar Stirling-
cycle for production has been limited to fraction of horsepower (Farber and Prescott, 1965).
The hot-air engine developed by Farber and Prescott in 1965 focused on area where air was
heated and its expansion pushes back the piston down. In the down-stroke of the piston, the
displacer moved to the left by the linkage. On the up-stroke of the piston, the displacer
moved to the right and all the hot air was at the left side of the cylinder and lost heat to the
cooling water.
An efficiency of about 9% was obtained at 100rpm with the break horsepower of about 0.2.
And after that Beale et al. (Beale et al., 1971) in 1971, considered free cylinder containing
the heavy piston which remained essentially stationary and a light displacer which moved
under the influence of pressure differential between the work part and the bound part in the
cylinder. The cylinder moved under the influence of the same pressure differential and
performs work against an external load. Since the entire pressure enclosure moved as the
unit, the free cylinder engine can deliver work from the completely sealed working gas and
since there are no internal bearing loads, or mechanical linkage or gears, etc., no lubrication
was needed. The engine should be inexpensive and should have a long life. The Fresnel
lens focused the solar radiation on the hot part of the engine and a double acting water
pump utilized the developed mechanical energy. An efficiency of about 9% was obtained at
100rpm with the working of about 149W. Stirling engine ideally could achieve the highest
possible energy conversion efficiency of all heat/working engines. Using practically any
kind of the energy, they can be employed with extremely low emissions as generator,
motor, heat pump or cooling system. In spite of all these advantages, Stirling engines still
have not made in the market breakthrough as a mass product.

A overall analysis of finite time thermodynamics of a Stirling heat engine was presented
with finite heat capacity of external reservoirs, regenerative losses and finite effectiveness
of each of the heat exchangers (i.e. a high temperature heat exchanger and a low
temperature heat exchanger) (Fette, 1995). They obtained the expressions for maximum
working output and defeated the corresponding thermal efficiency. The effect of operating
temperatures, the effectiveness of the regenerative heat exchanger on the heat transfer (QH
and QL) to and from the Stirling heat engine, the regenerative heat transfer (QR), the
maximum working power output (P) and the corresponding thermal efficiency of the cycle
have all been studied. They considered as the inlet source temperature and sink temperature
as 1300K and 300K. They also used effectiveness of each heat exchanger and each the
regenerator in the range from 0.4 to 1, and the capacitance rates of the heat source/sink
reservoirs in the range from 0.30 to 1.80kW/K. Their analysis showed that working output
and thermal efficiency were 62.55kW and 43.94%, respectively.
Bancha Kongtragool, SomchaiWongwises Fluid Mechanics, Thermal Engineering and
Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical engineer
Faculty of Engineering, King Mongkut‘s University of Technology Thonburi,presenred a
paper on ―A four working-piston low-temperature differential Stirling engine using
simulated solar energy as a heat source” at Bangmod, Bangkok 10140.
They reported that:
The low-temperature differential (LTD) Stirling engine is the type of Stirling engine that
can run with a small temperature difference between the hot and cold region of the
displacer cylinder. The LTD Stirling engine is therefore able to operate with many low-
temperature heat sources. Some characteristics of the LTD Stirling engine are as given
below:
(1) Displacer to working-piston swept volumes ratio or compression ratio is high.
(2) Diameters of displacer cylinder and displacer are high.
(3) Displacer length is small.
(4) Effective heat transfer surfaces on both end plates of the displacer cylinder are high.
(5) Displacer stroke is small.
(6) Dwell period at the end of the displacer stroke is slightly longer than the normal
Stirling engine.
(7) Operating speed is low.

While the Stirling engine has been studied by a number of researchers, the LTD Stirling
engine has received comparatively little concentration. Many studies related to solar-
operated Stirling engines and LTD Stirling engines have been reviewed in the authors‘
previous works
Haneman (1975) studied the using of air with low-temperature sources. This led to the
construction of an unusual Stirling engine, in which the exhaust heat was still sufficiently
hot to be useful for other purposes. The simply constructed low-temperature heat engine
modeled on the Stirling engine was patented by White (1983). White suggested improving
performance by pressurizing the displacer cylinder. Efficiencies were claimed to be around
30%, which is as quiet high for a low-temperature engine.
O‘Hare (1984) patented a device which passed cooled and heated streams of air through a
heat exchanger by changing the pressure of air inside the cylinder. The practical usefulness
of this device was not shown in detail as in the case of Haneman‘s work. Spencer (1989)
reported that, in practice, such an engine would produce only a small amount of useful
work relative to the collector size, and would give little compared to the additional
maintenance required.
Senft‘s work (Senft, 1991) showed the motivation in the use of Stirling engine. Their target
was to develop the Stirling engine operating with a temperature difference of 20
C or lower.
Senft's (1993) described the design and testing of a small LTD Ringbom Stirling engine
working by a 600
conical reflector. He reported that the tested 600
conical reflector,
producing the hot end temperature of 93 0
C under running conditions, worked very well.
Rizzo (1997) reported that Kolin experimented with 16 LTD Stirling engines, over the
period of 12 years. Kolin presented a model that worked on a temperature difference
between the hot and cold ends of displacer cylinder which was as low as 15 0
C.
Iwamoto et al. (1997) compared the performance of the LTD Stirling engine with a high-
temperature differential Stirling engine. They concluded that the LTD Stirling engine
efficiency at its rated speed was nearly 50% of the Carnot efficiency. However, the
compression ratio of their LTD Stirling engine was approximately equal to that of a
conventional Stirling engine. Its performance, therefore, seemed to be the performance of a
common Stirling engine operating at a low operating temperature.

SenftVan Arsdell (2001) made an in-depth study of the Ringbom engine and its derivatives,
including the LTD engine. Senft‘s research into LTD Stirling engines resulted in an
interesting LTD engine, which had an ultra-low temperature difference of 0.5 0
C. It has
been very difficult for anyone to create an engine with the result better than this.
Kongtragool and Wongwises (2003b) investigated the Beale number for LTD Stirling
engines by collecting the existing Beale number data for various engine specifications from
the paper. They concluded that the Beale number for a LTD Stirling engine could be found
from the mean-pressure working method.
Kongtragool and Wongwises (2005a) ideally investigated the working output of a gamma-
engine LTD Stirling engine. Former works on Stirling engine working output calculations
were studied. They pointed out that the mean-pressure working formula was the most
appropriate for LTD Stirling engine working output . However, the hot-part and cold-part
working fluid temperatures were needed in the mean-pressure working formula.
Kongtragool and Wongwises (2005b) presented the optimum absorber temperature of the
once reflecting full-conical reflector for a LTD Stirling engine. A mathematical model for
the overall efficiency of a solar operated Stirling engine was developed and the limiting
conditions of both maximum possible engine efficiency and working output were
calculated. Results showed that the optimum absorber temperatures obtained from both
conditions were not significantly different. However, the overall efficiency in the case of
the maximum possible engine working output was very close to that of the real engine of
55% Carnot efficiency.
Kongtragool and Wongwises (2007a) also gave the performance of two LTD Stirling
engines tested using LPG gas burners as heat sources. The first engine was a twin-working-
piston engine and the second was a four working- piston engine. Engine performances,
thermal performances, including the Beale‘s numbers were presented.
Now, Kongtragool and Wongwises (2007b) presented the performance of a twin-working-
piston Stirling engine working by a solar simulator. This engine was the same as the engine
described in (Kongtragool and Wongwises, 2007a).
So, the heat source was a solar simulator made from a 1000 W halogen lamp. Comparisons
were made between the characteristics of the high-temperature differential (HTD) and LTD
Stirling engine and methods for performance improvement. However some information is
currently available on the LTD Stirling engine, there still remains room for further research.

In particular the detailed investigation is lacking into the LTD Stirling engine using solar
energy as a heat source. As a consequence, in this, the testing of the performance of a LTD
Stirling engine using simulated solar energy. The LTD Stirling engine tested in this paper is
a kinematics, single-acting, four working piston, gamma-engine. Non-pressurized air is
used as a working fluid and a solar plate fabricated from four 1000 W tungsten halogen
lamps is used as a heat source. Since the gamma engine provides a high regenerator heat
transfer area.
BanchaKongtragool a, SomchaiWongwises b, aThe Joint Graduate School of Energy and
Environment, King Mongkut’s University of Technology Thonburi, Bangmod, presented a
paper on ―A review of solar-working Stirling engines and low temperature differential
Stirling engines‖ at Bangkok 10140, Thailand. They said that:
The Stirling engine was the first developed regenerative cycle heat engine. Robert Stirling
patented the Stirling engine in 1816 (patent no. 4081). Engines based upon his invention
were built in many forms and sizes until the turn of the century. Because Stirling engines
were simple and safe to operate, run almost silently on any fuel, and were clean and
efficient compared to steam engines, they were quite popular [3]
. These Stirling engines
were small and the working produced from the engine was low power (100 W to 4 kW).
In 1853, John Ericsson construct a high marine Stirling engine having four 4.2 m diameter
pistons with a stroke of 1.5 m producing a brake working of 220 kW at 9 rpm [10]
.
The first time of the Stirling engine was terminated by the rapid development of the internal
combustion engine and electric motor. 3. The second time of the Stirling engine began
around 1937[3]
, when the Stirling engine was brought to a high state of technological
development by the Philips Research Laboratory in Eindhoven, Holland, and has
progressed continuously since that time. Initial work was focused on the development of
small thermal-working electric generators for radios used in remote areas [3,4]
. New
materials were one of the keys to Stirling engine success. The Philips research team used
new materials, such as stainless steel [7]
.
Another key to success was a better knowledge of thermal and fluid physics than in the first
time. The specific working of the small ‗102C‘ engine of 1952 was 30 times that of the old
Stirling engine[11]
.

The progress in development made by Philips and other industrial laboratories, together
with the need for more energy resources, has sustained the second time of Stirling engine
development until today [7]
.
Intensive research by Philips and industrial laboratories the development of small Stirling
engines with high efficiencies of 30% or more. In 1954, Philips developed an engine using
hydrogen as the working fluid. This engine produced 30 kW for the maximum cycle
temperature of 977 K at 36% thermal efficiency. The efficiency of the equal engine was
than improved to 38%. The experimental studies of engines of different sizes up to 336 kW
were studied[8]
.
Other attempts to more develop Stirling engines under license of Philips, were carried out
by General Motors from 1958 to 1970 [10]
.
Other licenses were granted by Philips to United Stirling AB of Malmo, Sweden in 1968
and to the West German consortium of MAN and MWM in 1967[10]
. In 1973, the
Philips/Ford 4-125 experimental automotive Stirling engine accomplished a specific
working of over 300 times that of the first Stirling engines [7]
.
Trayser and Eibling[12]
carried out a design study to determine the technical feasibility of
developing a 50 W portable solar-working generator for use in remote areas. The results of
their study indicate that it is possible to build solar-working lightweight portable, reliable,
Stirling engine at a reasonable cost. Gupta et al.[13]
developed 1 and 1.9 kW solar-working
reciprocating engines for rural applications. Engine efficiencies were found to be between
5.5 and 5.7% and overall efficiency was found to be 2.02%[17]
.
Pearch et al.[14]
proposed and analyzed a 1 kW domestic, combined heat and working
(DCHP) system. The results show that 30% of a home‘s electrical demand could be
developed and electricity cost could be reduced by about 25%. Podesser[19]
designed,
generated and operated a Stirling engine, heated by the flue gas of a biomass furnace, for
electricity production in rural area. With the working gas pressure of 33 bar at 600 rpm and
the shaft working of 3.2 kW, an overall efficiency of 25% was obtained. He expected to
extend the shaft working to 30 kW in the next step.

Dixit and Ghodke[14]
designed compact working generating systems capable of using the
combination of a wide variety of solid fuels as a local working source. The system was a
heat pipe based, biomass energy-driven Stirling engine. The macroscopic thermal design of
the engine along with the calculation of various energy losses was reported.
―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 Nacken, 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. Successful demonstration of AIP
system during many routine patrols of HMS Nacken made that Gotland, another type of
submarine, was the first submarine designed from the beginning to operate with AIP
system.

Chapter 3- EXPERIMENT SETUP
Fig. 3.1. Stirling Engine
The main function is shown in Diagram 1. The model consists of two parallel cylinders
which are connected by a copper tube. The working piston is open at one end between the
pressure piston and the displacement cylinder is a small air pass in which the air can
transfer. Both of the pistons work at 90 degrees angel against each other from a single
crankshaft. The hot air is made at the end of the displacement chamber (combustion
chamber).A cooler ensures that the temperature falls to ensure a good working efficiency.

The following diagrams explain the various stages
Fig. 3.1.1. working stages
A: The air placed in the working cylinder has cooled down. A slightly lower pressure is
formed and the working piston is pushed into the cylinder. The air volume is at its greatest
level. The displacement piston moves forward towards the heated area of the cylinder and
pushes the air into the cooler area. Mechanical movement follows.
B: The Displacement piston is placed at the far end of its stroke. On the way it has pushed
the hot air into the working cylinder. The movements of the two flywheels push the
working piston into its cylinder area.
C: In diagram C the working piston pushes the cooled air into the heated displacement
cylinder area just as the piston is reaching the cooler end. Then the air is heated and
expands pushing back the working piston back again. Mechanical movement follows
D: In diagram D the displacement piston has reached its top dead center and the working
piston is about to be moved to the position which shown in diagram A

3.2 LIST OF COMPONENTS AND MATERIALS
COMPONENT MATERIAL DIMENSIONS(MM)
FLYWEEL STEEL ∅55𝑋5
DISPLACER
PISTON
STEEL WIRE
AND GLASS
WOOL
∅18X85
WORKING
PISTON
ALUMINIUM ∅17X16
HOT CYLINDER CAST IRON ∅32X40
COLD
CYLINDER
TEST TUBE ∅20
CONNECTING
ROD
STEEL PLATE 120X10X2
AXLE STEEL ROD ∅5X55
COOLER ALUMINIUM 30X30X38
JOINING TUBE BRASS ∅8X50
SUPPORT AND
BASE ELEMENT
WOOD AND
ALUMINIUM
140X140

3.3 MANUFACTURING OF PARTS
3.3.1 MAKING OF CONNECTING ROD
Fig.3.3.1. connecting rod
- Cut the flat strip by 10 x 2 x 120 to length
- File its end to 90 degrees
- Then Mark out the center
- Centre punch
- Remove burr from surfaces
- Drill the holes according to dia. (3, 8 and 1,8mm diameter, open them out to 4 and 2mm
diameter)
3.3.2 MAKING OF BEARING BLOCKS
Fig.3.3.2. bearing blocks

- Remove the burr
- Mark out point
- Drill the 7mm diameter holes on marked area (Drill the pilot whole 1.6mm diameter
first!!!)
- Make internal thread. Tap the M4 internal thread –drill a 3, 3 mm hole first
3.3.3 MAKING OF FLYWHEEL
Fig.3.3.3. flywheel
- Make both of the internal M3 holes
- Then Drill out to 2.5mm dia
- Make the M3 thread on surface
- Place the axle 5 in the 5mm diameter hole
- Mark the middle of the axle
- Mark the 8 holes in flywheel
- Use Centre punch
- Drill with an 8mm pilot drill. (Carefully hold the work in a vice)
- Then Drill the 11mm diameter holes
- After that remove the burr with a countersink bit

3.3.4 MAKING OF BASE PART
Fig. 3.3.4. Base part
3.3.5 MAKING OF FLANGE
Fig.3.3.5. flange

3.3.6 MAKING OF THE COOLER
- Place the "O‖ ring in the flange and insert the borosilicate test tube in the flange
- The flange (With test tube + O ring) on the front of the cooler and then push the test tube
until it reaches a stop.
- Place the flange and cooler in a vice, remember that the test tube is upright to the cooler
and flange.
- Mark out the 4 x 2.5mm, holes in the flange on the surface of the cooler (Drill)
- Remove the cooler from the vice and add the brass tube (25) 3 x1 x18 press in the 3mm
hole (If it has too much play use a little glue)
- Now drill out 4 holes of 3, 1 diameter in the flange
- Now remove the entire burr
3.3.7 ASSEMBLE OF THE ENGINE
Fig.3.3.7. assembly of the engine
- Joint the working cylinder and the cooler with the help of glue and the joiner together
with two component glue. The glue points must be air tight and not seep into the joiner.

The distance between the cooler and the working cylinder is approximately 36mm. Check
the sizes once more before the glue sets otherwise adjust if necessary. The axis of the
cooler and the working cylinder must be placed in parallel to one another
- Now the two bushes for the flywheels (dia 7 x 1 x 7, 5) be inserted in the bearing block
and jointed in place with 2 component glue. Finally drill the two oil hole (Dia 2,5mm)
- Shorten pin to 11.7mm (Or shorter) so that it does not protrude over the working cylinder
piston (12mm dia) and rubbing on the cylinder wall.
Join together all the connecting rod, the working piston and the shortened pin. Now the
mount it on the wooden base. On wooden base mount the bearing block with flywheels
and motor holder with washers and the screws on the base
Then join the connecting rods with the cylinder and the carrier bushes (15/18) to the
flywheels
Then Cut for square feet 30mm from the cellular foam and glue them on the base
- Now take the displacement piston in the cooler until the stop. Lay the O ring in flange
and insert the test tube into the flange. Then Insert the test tube in the cooler up to the stop
and then join the flange with 4 machine screws (test tube and cooler must be vertical with
each other. The backward and forward movement of the displacer must be free and easy to
move. Connecting rod with the screws and then use the connector block to join them.
Place the copper tube (16/3 +7mm) on the hooks to control the movement of the
connecting rods. When adjusting the flywheels on the axles it‘s necessary to see that the
working piston and the displacement piston are not stopped from the working condition.
- The two connecting rods are must run parallel to each other (Correct by adjusting the
bearing block –cooler with the working cylinder is possible)
- The "compressor‖ piston must not be stopped on the front or the back dead point in the
cylinder
- Finally the 90 degree angle between the two connecting rods and the flywheels are set as
shown in the figures

Chapter 4: RESULT AND DISCUSSION
In this project we construct alpha type Stirling engine, which has piston ( )
and according to that we design our model which is shown in upper fig.3.3.7. First we
design the engine in the creo parametric 2.0 designing software which is shown in below:
Fig. 4.1. Creo Model
Then we lubricate the all moving parts like working piston, connecting rods, joints,
flywheel, etc. with the help of thin oil. Then we heat up the displacer with the three candles.
But due to some reasons like friction, failure of regenerator and unstable joints engine can
not worked.

Chapter 5: CONCLUSION
We construct an alpha type solar operated Stirling engine in which we use atmospheric air
as a working fuel and displacer is made up of test tube then we heat up the engine by solar
radiation but due to some reasons the engine cannot work properly. Some of these reasons
are following below:
i. If Wrong lubricant used
ii. If too much friction between the parts
iii. If the displacement piston touches the front dead point in the cylinder
iv. If the displacement piston touches the rear dead point in the cylinder
v. If the displacement piston rubs on the cylinder too much
vi. If heat not enough
vii. If the displacement piston not properly wound.
viii. If the displacement cylinder does not move with the push rod- not working properly

Chapter 6: REFERENCES
[1] Bancha Kongtragool, SomchaiWongwises Fluid Mechanics, Thermal Engineering
and Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical
engineer Faculty of Engineering, King Mongkut‘s University of Technology
Thonburi,presenred a paper on ―A four working-piston low-temperature differential
Stirling engine using simulated solar energy as a heat source” at Bangmod, Bangkok
10140.
[2] Bancha Kongtragool, SomchaiWongwises Fluid Mechanics, Thermal Engineering and
Multiphase Flow Research Laboratory (FUTURE), Department of Mechanical
engineer Faculty of Engineering, King Mongkut‘s University of Technology
Thonburi,presenred a paper on ―A two working-piston low-temperature differential
Stirling engine using simulated solar energy as a heat source” at Bangmod, Bangkok
10140.
[3] Pongsakorn Kerdchang, Maung MaungWin, and Sombat Teekasap, of Scientific
Research Center, South-East Asia University, presented a research paper on
“Development of a new solar thermal engine system for circulating water for
aeration.” At Thailand.
[4] Bancha congragool and somachi congwises of The Joint Graduate School of Energy
and Environment, King Mongkut‘s University of Technology Thonburi,presenred a
paper on ―A review of solarstirling engine and low temperature differential engine as
a heat source” at Bangmod, Bangkok 10140.
[5] Stine WB. Stirling engines. In: Kreith F, editor. The CRC handbook of mechanical
engineers. Boca Raton: CRC Press; 1998. p. 8-7–8-6.
[6] Van Arsdell BH. Stirling engines. In: Zumerchik J, editor. Macmillan encyclopedia of
energy, vol. 3. Macmillan Reference USA; 2001. p. 1090–95.
[7] Senft JR. Ringbom Stirling engines. New York: Oxford University Press, 1993.
[8] Walpita SH. Development of the solar receiver for a small Stirling engine. In: Special
study project report no. ET-83-1. Bangkok: Asian Institute of Technology; 1983.
[9] Rizzo JG. The Stirling engine manual. Somerset: Camden miniature steam services,
1997.

[10] Walker G. Elementary design guidelines for Stirling engines. In: Proceedings of the
14th Intersociety Energy Conversion Engineering Conference, Paper 799230. Boston:
American Chemical Society; 1979.
[11] West CD. A historical perspective on Stirling engine performance. In: Proceedings of
the 23rd Intersociety Energy Conversion Engineering Conference, Paper 889004.
Denver: American Society of Mechanical Engineers; 1988.
[12] Spend 1950—―Conventional‖ engines up to 100 kW. Sol Energy 1989; 43:197–210.r
LC. A comprehensive review of small solar-working heat engines: Part I.I. Research
since
[13] Prodesser E. Electricity production in rural villages with biomass Stirling engine.
Renew Energy 1999; 16:1049–52.
[14] Dixit DK, Ghodke SV. Renewable energy working Stirling engines—a viable energy
alternative. In: Sayigh AAM, editor. Renewable energy technology and the
environment. Proceedings of the Second World Renewable Energy Congress, vol. 2.
1992. p. 934–8.

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