stirling engine term project report
TRANSCRIPT
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Semester TERM Project Report On
DESIGN AND FABRICATION
OF A STIRLING ENGINE.
1.:- Syed Anis Badshah UW-09-ME-BE-001
2.:-Qazi Naseer Ahmad UW-09-ME-BE-020
3.:-Muhamad Umair UW-09-ME-BE-030
4.:-Shafique Ahmad UW-09-ME-BE-032
5.:- Syed Shahid Raza UW-09-ME-BE-034
Wah Engineering College
UNIVERSITY OF WAH
JANUARY 2011
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Looking at the present power scenario we can get an idea of the importance ofalternate ways of getting energy. One of the simpler and cheaper one of these methods is
the Solar-Stirling method. In this method a Stirling engine is coupled onto a solar collector.
One such mechanism for energy generation was desired. The part of the project that is
presented here only deals with the Stirling engine. The engine was designed except for the
regenerator part which was built on hit and trial methods as has been done in nearly all
experimental engines since the calculations involved are too difficult. The theoretical
calculations of the engine were done along with the position analysis of the engine and the
values sorted were used to design the engine. The structural analysis and the thermal
analysis of the engine was done and based on this the design was finalized. The design is
still being fabricated but due to frequent load shedding and other issues the engine could
not be tested in time.
This project is dedicated to
our parents AND Teachers without whose
support and prayers we are nothing.
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First of all we would like to thank Allah Almighty for giving us the chance and the
courage to carry out this project. Although the task is not complete yet but we have
achieved a lot from this project so we keep on praying to Allah for more.
Secondly, we would like to thank ourSupervisor Engr; Muazma for all the support
and guidance without which we would have never gone so far.
Thirdly we would like to thank WEC lab Staff for their technical advices.
We would like to thank Engr; Tehseen for helping us re-assemble the system.
Stirling engine is a regenerative thermal machine, 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", and there
is a net conversion of heat to work or vice versa.
In this context, closed-cycle means that the working fluid is permanently contained
within the system, whereas "open-cycle" engines such as internal combustion engine and
some steam engines, exchange working fluid with theirsurroundings as part of the cycle.
Regenerative refers to the use of an internal heat exchanger - the regenerator -
which greatly improves the engine's potential efficiency.
http://en.wikipedia.org/wiki/Thermodynamic_systemhttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Thermodynamic_systemhttp://en.wikipedia.org/wiki/Thermodynamic_cyclehttp://en.wikipedia.org/wiki/Stirling_engine#the_regeneratorhttp://en.wikipedia.org/wiki/Stirling_engine#the_regeneratorhttp://en.wikipedia.org/wiki/Thermodynamic_cyclehttp://en.wikipedia.org/wiki/Thermodynamic_systemhttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Thermodynamic_system -
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There are many possible implementations of the Stirling engine, the majority of
which fall into the category of a reciprocating piston engine.
The Stirling engine is traditionally classified as an external combustion engine,
though heat can equally well be supplied by non-combusting sources such as solar or
nuclear energy. A Stirling engine operates through the use of an external heat source and
an external heat sink having a sufficiently large temperature difference between them
In the conversion of heat into mechanical work, the Stirling engine has the potential
to achieve the highest efficiency of any real heat engine, theoretically up to the full Carnot
efficiency, though in practice this is limited by non-ideal properties of the working gas and
engine materials, such as friction, thermal conductivity, tensile strength, creep, melting
point, etc. The engines can run on any heat source of sufficient quality, including solar,
chemical and nuclear.
The major advantages of Stirling Engines are:-
1) They can run directly on any available heat source.
2) A continuous combustion process can be used to supply heat, emissions can be
greatly reduced.3) Most types of Stirling engines have the bearing and seals on the cool side of the
engine; consequently, they require less lubricant and last significantly longer
between overhauls than other reciprocating engine types.
4) The engine mechanisms are in some ways simpler than other types of reciprocating
engine types, i.e. no valves are needed, and the fuel burner system can be relatively
simple.
5)A Stirling engine uses a single-phase working fluid which maintains an internalpressure close to the design pressure.
http://en.wikipedia.org/wiki/Reciprocating_enginehttp://en.wikipedia.org/wiki/External_combustion_enginehttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Nuclear_energyhttp://en.wikipedia.org/wiki/Heat_sinkhttp://en.wikipedia.org/wiki/Work_%28thermodynamics%29http://en.wikipedia.org/wiki/Carnot_cyclehttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Creep_%28deformation%29http://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Quality#In_Thermodynamicshttp://en.wikipedia.org/wiki/Quality#In_Thermodynamicshttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Creep_%28deformation%29http://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Carnot_cyclehttp://en.wikipedia.org/wiki/Work_%28thermodynamics%29http://en.wikipedia.org/wiki/Heat_sinkhttp://en.wikipedia.org/wiki/Nuclear_energyhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/External_combustion_enginehttp://en.wikipedia.org/wiki/Reciprocating_engine -
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6) They can be built to run very quietly and without an air supply, for air-independent
propulsion use in submarines or in space.
The Stirling engines have many advantages but some disadvantages come with the
package:-
Size and Cost Issues
a. Stirling engine designs require heat exchangers for heat input and for heat output,and these must contain the pressure of the working fluid, where the pressure is
proportional to the engine power output. In addition, the expansion-side heat
exchanger is often at very high temperature, so the materials must resist the
corrosive effects of the heat source, and have low creep (deformation). Typically
these material requirements substantially increase the cost of the engine. The
materials and assembly costs for a high temperature heat exchanger typically
accounts for 40% of the total engine cost.
b. All thermodynamic cycles require large temperature differentials for efficient
operation; however, in an external combustion engine, the heater temperature
always equals or exceeds the expansion temperature. This means that the
metallurgical requirements for the heater material are very demanding. This is similar
to a Gas turbine, but is in contrast to a Otto engine or Diesel engine, where the
expansion temperature can far exceed the metallurgical limit of the engine materials,
because the input heat-source is not conducted through the engine; so the engine
materials operate closer to the average temperature of the working gas.
c. Dissipation of waste heat is especially complicated because the coolant temperature
is kept as low as possible to maximize thermal efficiency. This increases the size of
the radiators, which can make packaging difficult. Along with materials cost, this has
been one of the factors limiting the adoption of Stirling engines as automotive prime
movers. However, for other applications high power density is not required, such as
Ship propulsion, and stationary micro-generation systems using combined heat and
power(CHP)
http://en.wikipedia.org/wiki/Air-independent_propulsionhttp://en.wikipedia.org/wiki/Air-independent_propulsionhttp://en.wikipedia.org/wiki/Submarinehttp://en.wikipedia.org/wiki/Heat_exchangerhttp://en.wikipedia.org/wiki/Creep_%28deformation%29http://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Otto_enginehttp://en.wikipedia.org/wiki/Diesel_enginehttp://en.wikipedia.org/wiki/Power_densityhttp://en.wikipedia.org/wiki/Ship#Propulsionhttp://en.wikipedia.org/wiki/Microgenerationhttp://en.wikipedia.org/wiki/Cogenerationhttp://en.wikipedia.org/wiki/Cogenerationhttp://en.wikipedia.org/wiki/Cogenerationhttp://en.wikipedia.org/wiki/Cogenerationhttp://en.wikipedia.org/wiki/Microgenerationhttp://en.wikipedia.org/wiki/Ship#Propulsionhttp://en.wikipedia.org/wiki/Power_densityhttp://en.wikipedia.org/wiki/Diesel_enginehttp://en.wikipedia.org/wiki/Otto_enginehttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Creep_%28deformation%29http://en.wikipedia.org/wiki/Heat_exchangerhttp://en.wikipedia.org/wiki/Submarinehttp://en.wikipedia.org/wiki/Air-independent_propulsionhttp://en.wikipedia.org/wiki/Air-independent_propulsion -
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Power and Torque Issues:
a. Stirling engines, especially those that run on small temperature differentials, are
quite large for the amount of power that they produce (i.e. they have low specific
power). This is primarily due to the low heat transfer coefficient of gaseous
convection which limits the heat flux that can be attained in an internal heat
exchanger to about 4 - 20 W/(m*K). This makes it very challenging for the engine
designer to transfer heat into and out of the working gas. Increasing the
temperature differential and/or pressure allows Stirling engines to produce morepower, assuming the heat exchangers are designed for the increased heat load,
and can deliver the convected heat flux necessary.
b. A Stirling engine cannot start instantly; it literally needs to "warm up".
c. Power output of a Stirling tends to be constant and to adjust it can sometimes
require careful design and additional mechanisms.
Gas Choice Issues:
a. Hydrogen's low viscosity, high thermal conductivity and specific heat make it the
most efficient working gas, in terms of thermodynamics and fluid dynamics, to use in
a Stirling engine. However, given the high diffusion rate associated with this low
molecular weight gas, hydrogen will leak through solid metal, thus it is very difficult to
maintain pressure inside the engine for any length of time without replacement of the
gas. Typically, auxiliary systems need to be added to maintain the proper quantity of
working fluid. These systems can be a gas storage bottle or a gas generator.
Hydrogen can be generated either by electrolysis of water, or by the reaction ofacid
on metal. Hydrogen can also cause the embrittlement of metals. Hydrogen is also a
very flammable gas, while helium is inert.
b. Most technically advanced Stirling engines use helium as the working gas, because
it functions close to the efficiency and power density of hydrogen with fewer of the
material containment issues. Helium is relatively expensive, and must be supplied by
http://en.wikipedia.org/wiki/Specific_powerhttp://en.wikipedia.org/wiki/Specific_powerhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Thermodynamicshttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Hydrogen_embrittlementhttp://en.wikipedia.org/wiki/Inert_gashttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Inert_gashttp://en.wikipedia.org/wiki/Hydrogen_embrittlementhttp://en.wikipedia.org/wiki/Acidhttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Fluid_dynamicshttp://en.wikipedia.org/wiki/Thermodynamicshttp://en.wikipedia.org/wiki/Specific_heathttp://en.wikipedia.org/wiki/Thermal_conductivityhttp://en.wikipedia.org/wiki/Viscosityhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Specific_powerhttp://en.wikipedia.org/wiki/Specific_power -
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bottled gas. One test showed hydrogen to be 5% absolutely (24% relatively) more
efficient than helium in the GPU-3 Stirling engine.
c. Some engines use air or nitrogen as the working fluid. These gases are less
thermodynamically efficient but they minimize the problems of gas containment and
supply. The use of Compressed air in contact with flammable materials or
substances such as lubricating oil, introduces an explosion hazard, because
compressed air contains a high partial pressure ofoxygen. However, oxygen can be
removed from air through an oxidation reaction, or bottled nitrogen can be used.
Stirling engines have the following major applications:-
Combined heat and power (CHP) applications
CHP is an economical source of mechanical or electrical power, which uses a heatsource in conjunction with a secondary heating application, usually a pre-existing energy
use, such as an industrial process. Usually the primary heat source will enter the Stirling
engine heater.
Solar power generation
Placed at the focus of a parabolic mirror a Stirling engine can convert solar energy to
electricity with an efficiency better than non-concentrated photovoltaic cells, and
comparable to Concentrated Photo-voltaics.
Stirling cryocoolers: Any Stirling engine will also work in reverse as a heat pump: i.e.
when a motion is applied to the shaft, a temperature difference appears between the
reservoirs. One of their modern uses is in refrigeration and cryogenics.
http://en.wikipedia.org/wiki/Airhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Compressed_airhttp://en.wikipedia.org/wiki/Partial_pressurehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Photovoltaic_cellshttp://en.wikipedia.org/wiki/Concentrated_Photo_Voltaicshttp://en.wikipedia.org/wiki/Heat_pumphttp://en.wikipedia.org/wiki/Refrigerationhttp://en.wikipedia.org/wiki/Cryogenicshttp://en.wikipedia.org/wiki/Cryogenicshttp://en.wikipedia.org/wiki/Refrigerationhttp://en.wikipedia.org/wiki/Heat_pumphttp://en.wikipedia.org/wiki/Concentrated_Photo_Voltaicshttp://en.wikipedia.org/wiki/Photovoltaic_cellshttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Partial_pressurehttp://en.wikipedia.org/wiki/Compressed_airhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Air -
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Heat pump:A Stirling heat pump is very similar to a Stirling cryocooler, the main
difference being that it usually operates at room-temperature and its principal application to
date is to pump heat
Marine engines:Kockums, the Swedish shipbuilder, had built at least 8 commercially
successful Stirling powered submarines during the 1980s. As of 2005 they have started to
carry compressed oxygen with them (see Gotland class submarine).
Nuclear power: There is a potential for nuclear-powered Stirling engines in electric
power generation plants. Replacing the steam turbines of nuclear power plants with Stirlingengines might simplify the plant, yield greater efficiency, and reduce the radioactive by-
products.
Automotive engines: While it is often claimed that the Stirling engine has too low a
power/weight ratio and too long a starting time for automotive applications there have been
at least two exclusively Stirling powered automobiles developed by NASA besides earlier
projects by Ford and American Motor Companies.
Aircraft engines: Stirling engines hold theoretical promise as aircraft engines. They are
quieter, less polluting, gain efficiency with altitude, 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.Geothermal energy: Some believe that the ability of the Stirling engine to convert
geothermal energy to electricity and then to hydrogen may well hold the key to replacement
of fossil fuels in a future hydrogen economy.
Low temperature difference engines:A low temperature difference Stirling engine
will run on any low temperature differential, for example the difference between the palm of
a hand and room-temperature or room temperature and an ice cube. Usually they are
designed in a gamma configuration, for simplicity, and without a regenerator.
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Stirling's air engine was invented by Reverend Dr Robert Stirling and patented by him in
1816. When the name became simplified to Stirling engine is not known, but may be as
recently as the mid twentieth century when the Philips company began to experiment with
working fluids other than air - the instruction book for their MP1002CA still refers to it as an
'air engine'. The main subject of that original patent was a heat exchanger which Stirling
called the "economiser" for its enhancement of fuel economy in a variety of applications.
The patent also described in detail the employment of one form of the economiser in an air
engine, in which application it is now commonly known as a regenerator.
An engine built by Stirling was put to work pumping water in a quarry in 1818. Subsequent
development by Robert Stirling and his brother James, an engineer, resulted in patents for
various improved configurations of the original engine, including pressurization which by
1845 had sufficiently increased the power output for it to successfully drive all the
machinery at a Dundee iron foundry.
As well as conserving fuel, the inventors sought to create a safer alternative to the steam
engines of the time whose boilers frequently exploded with dire consequences, often
including loss of life. However, the need for the Stirling engine to run at a very high
temperature to maximise power and efficiency exposed limitations in the materials of the
day and the few engines which were built in those early years had rather short and
troublesome lives. In particular, 'hot end' failures occurred more frequently than could be
tolerated, albeit with far less disastrous results than a steam boiler explosion.
Though it ultimately failed as a competitor to the steam engine in the field of industrial scale
prime movers, during the latter nineteenth and early twentieth centuries smaller engines of
the Stirling/hot air type (the boundary between the two is often blurred as in many the
regenerator is of dubious efficiency or omitted altogether) were produced in large numbers,
finding applications wherever a reliable source of low to medium power was required, most
commonly perhaps for raising water. These generally operated at lower temperatures so as
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not to tax available materials and thus tended to be rather inefficient, their major selling
point being that in contrast to a steam engine, they could be operated safely by anybody
capable of managing the fire in a domestic range. As the century wore on, this role was
eventually usurped by the electric motorand small internal combustion engines and by the
late 1930s the Stirling engine was a largely forgotten scientific curiosity represented only by
toys and a few small ventilating fans.
At this time Philips, the large Dutch electrical and electronic manufacturer, began research
into the engine. Seeking to expand the market for its radio sets into areas where mains
electricity power was unknown and the supply of short-lived batteries uncertain, Philips
management decided that what was needed was a low-powered portable generator andtasked a group of engineers at the company research lab (the Nat. Lab) in Eindhoven to
investigate the practicalities. Reviewing various prime movers old and new, each was
rejected for one reason or another until the Stirling engine was considered. Inherently quiet
and capable of running from any heat source (common lamp oil cheap and available
everywhere was favoured), it seemed to offer real possibilities. Encouraged by their first
experimental engine, which produced 16 watts of shaft power from a bore and stroke of
30x25mm, a development program was set in motion.
Remarkably, this work continued throughout World War II and by the late 1940s they had
an engine the Type 10 which was sufficiently developed to be handed over to Philips
subsidiary Johan de Witt in Dordrecht to be productionised and incorporated into a
generator set as originally planned. The set progressed through three prototypes (102A, B,
and C), with the production version, rated at 200 watts electrical output from a bore and
stroke of 55x27mm, being designated MP1002CA (affectionately known as the 'Bungalow
set'). Production of an initial batch began in 1951, but it became clear that they could not be
made at a price that the market would support, in addition to which the advent of transistor
radios with their much lower power requirements meant that the market for the set was fast
disappearing. Though the MP1002CA may have been a dead end, it represents the start of
the modern age of Stirling engine development.
Philips went on to develop the Stirling engine for a wide variety of applications including
vehicles, but only ever achieved any commercial success with the 'reversed Stirling engine'cryocooler. They did however take out a large number of patents and amass a wealth of
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information relating to Stirling engine technology, which was later licensed to other
companies.
It was also employed in reverse as a heat pump to produce early refrigeration
Think Nordic, an electric car company in Norway, is working with inventor Dean Kamen on
plans to install Stirling engines in the Think City, an otherwise all-electric vehicle that will be
commercially available at the end of 2007, at least in Europe.
Since 1988, Kockums shipyards have equipped submarines with Stirling engines. They are
currently used on submarines of the Gotland and Sdermanland classes. These engines
are run on diesel and liquid oxygen and are fitted under
Engineers classify Stirling engines into three distinct types. The Alpha type engine relies on
interconnecting the power pistons of multiple cylinders to move the working gas, with the
cylinders held at different temperatures. The Beta and Gamma type Stirling engines use a
displacer piston to move the working gas back and forth between hot and cold heat
exchangers in the same cylinder.
An alpha Stirling contains two separate power pistons in separate cylinders, one "hot"piston and one "cold" piston. The hot piston cylinder is situated inside the higher
temperature heat exchanger and the cold piston cylinder is situated inside the low
temperature heat exchanger. 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 the
durability of its seals.
ACTION OF AN ALPHA TYPE STIRLING ENGINE
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The following diagrams do not show a regenerator, which would be placed in the pipe
connecting the two cylinders. The crankshaft has also been omitted.
1. Most of the working gas is in contact with the hot cylinder walls ,
it has been heated and expansion has pushed the hot piston to the
top of the cylinder. Expansion continues in the cold cylinder piston,
which is 90o
behind the hot piston in its cycle, extracting still more
work from the hot gas.
2. The gas is now at its maximum volume. The hot cylinder piston
begins to move most of the gas into the cold cylinder , where it
cools and the pressure drops.
3. Almost all the gas is now in the cold cylinder and cooling
continues. The cold piston, powered by flywheel momentum or
other piston pairs on the same shaft, compresses the remaining
part of the gas.
4. The gas reaches its minimum volume and the hot cylinder
piston will now allow it to expand in the hot cylinder where it
will be heated once more and drive the hot piston in its power
stroke.
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. When the working gas is pushed to the hot end of
http://en.wikipedia.org/wiki/Displacerhttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Alpha_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Displacer -
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the cylinder it expands and pushes the power piston. When it is pushed to the cold end of
the cylinder it contracts and the momentum of the machine, usually enhanced by a
flywheel, pushes the power piston the other way to compress the gas. Unlike the alpha
type, the beta type avoids the technical problems of hot moving seals.
ACTION OF A BETA TYPE STIRLING ENGINE
A beta Stirling has two pistons within the same cylinder both connected to the same
crankshaft. One of these is the tightly fitted power piston and the other a loosely fitted
displacement piston.
1. Power piston (dark grey) has
compressed the gas, the displacer
piston (light grey) has moved so
that most of the gas is adjacent to
the hot heat exchanger.
2. The heated gas increases its
pressure and pushes the power
piston along the cylinder. This is
the power stroke.
3. The displacer piston now
moves to shunt the gas to the
cold end of the cylinder.
4. The cooled gas is now
compressed by the flywheel
momentum. This takes less
energy since when it cooled its
pressure also dropped.
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 but remains a single
http://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_8.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_4.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_16.pnghttp://en.wikipedia.org/wiki/Image:Beta_Stirling_frame_12.pnghttp://en.wikipedia.org/wiki/Flywheel -
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body. This configuration produces a lower compression ratio but is mechanically simpler
and often used in multi-cylinder Stirling engines.
Changes to the configuration of mechanical Stirling engines continue to interest engineers
and inventors. Notably, some are in pursuit of the rotary Stirling engine; the goal here is to
convert power from the Stirling cycle directly into torque, a similar goal to that which led to
the design of the rotary combustion engine. No practical engine has yet been built but a
number of concepts, models and patents have been produced.
There is also a field of "free piston" Stirling cycles engines, including those with liquid
pistons and those with diaphragms as pistons.
A recent development of Stirling engines are the thermoacoustic stirling engine, which looks
like the beta Stirling engines but without the displacer.
Virtually, any temperature difference will power a Stirling engine. The heat source may be
derived from fuel combustion, hence the term "external combustion engine", although the
heat source may also be solar, geothermal, nuclear or even biological. Likewise a "cold
source" below the ambient temperature can be used as the temperature difference. A cold
source may be the result of a cryogenic fluid or iced water. In the case where a small
temperature differential is used to generate a significant amount of power, large mass flows
of heating and cooling fluids must be pumped through the external heat exchangers, thus
causing parasitic losses that tend to reduce the efficiency of the cycle.
Because a heat exchanger separates the working gas from the heat source, a wide range
of heat sources can be used, including any fuel or waste heat from some other process.
Since the combustion products do not contact the internal moving parts of the engine, a
Stirling engine can run on landfill gas containing siloxanes without the accumulation ofsilica
http://en.wikipedia.org/wiki/Compression_ratiohttp://en.wikipedia.org/wiki/Rotary_combustion_enginehttp://en.wikipedia.org/wiki/Thermoacoustic_stirling_enginehttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Geothermal_energyhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Biologyhttp://en.wikipedia.org/wiki/Cryogenhttp://en.wikipedia.org/wiki/Landfill_gashttp://en.wikipedia.org/wiki/Siloxanehttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Siloxanehttp://en.wikipedia.org/wiki/Landfill_gashttp://en.wikipedia.org/wiki/Cryogenhttp://en.wikipedia.org/wiki/Biologyhttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/Geothermal_energyhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Thermoacoustic_stirling_enginehttp://en.wikipedia.org/wiki/Rotary_combustion_enginehttp://en.wikipedia.org/wiki/Compression_ratio -
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that damages internal combustion engines running on this fuel. The life of lubricating oil is
longer than for internal-combustion engines.
.;The Stirling cycle is similar, in some respects, to the Carnot cycle. It is illustrated in
figure.
http://en.wikipedia.org/wiki/Internal_combustion_enginehttp://en.wikipedia.org/wiki/Internal_combustion_engine -
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The cycle is composed, therefore, of four heat-transfer process.
Process 1-2: isothermal compression; heat transfer from the working f luid at Tminthe external
dump.
Process 2-3: constant volume; heat transfer to the working fluid from the regenerative matrix.
Process 3-4: isothermal expansion; heat transfer to the working fluid at Tmax from an external
source
Process 4-1: constant volume; heat transfer from the working fluid to the regenerative
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We need one more value beside the inputs in order to solve the ideal cycle of the Stirling
engine.
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ENGINE DESIGN:
Our engine design was based around previously designed Stirling engines. Various alpha
type Stirling engine designs along with low speed fossil fuel reciprocating engines were
used to get a rough sketch for our design requirements. Based on these studies and our
design requirements, the following features were to be incorporated in out engine:
A two cylinder design in which one cylinder known as initiating sleeve would
involve the heat addition process and the other known as displacer sleeve,
involveheat rejection process.
The two cylinders are to be at 90o to each other.
Basic reciprocating engine components to give the desired displacement: crankshaft,
connecting rod.
Design of the displacer element keeping in mind the sealing requirements and thepressures inside the cylinders.
Design of the head section and the connection between the two cylinders