O SlideShare utiliza cookies para otimizar a funcionalidade e o desempenho do site, assim como para apresentar publicidade mais relevante aos nossos usuários. Se você continuar a navegar o site, você aceita o uso de cookies. Leia nosso Contrato do Usuário e nossa Política de Privacidade.
O SlideShare utiliza cookies para otimizar a funcionalidade e o desempenho do site, assim como para apresentar publicidade mais relevante aos nossos usuários. Se você continuar a utilizar o site, você aceita o uso de cookies. Leia nossa Política de Privacidade e nosso Contrato do Usuário para obter mais detalhes.
A STIRLING engine is a heat engine operating by cyclic
compression and expansion of air or other gas, the working
fluid at different temperature levels such that there is a net
conversion of heat energy to mechanical work Or more
specifically, a closed-cycle regenerative heat engine with a
permanently gaseous working fluid, where closed-cycle is
defined as a thermodynamic system in which the working fluid
is permanently contained within the system and regenerative
describes the use of a specific type of internal heat exchanger
and thermal store known as the regenerator .
It is the inclusion of a regenerator that differentiates the
STIRLING engine from other closed cycle hot air engines.
Originally conceived in 1816 as an industrial prime mover
to rival the steam engine, its practical use was largely
confined to low-power domestic applications for over a
century. The STIRLING engine is noted for its high efficiency
compared to steam engines, quiet operation, and the ease
with which it can use almost any heat source. This
compatibility with alternative and renewable energy sources
has become increasingly significant as the price of
conventional fuels rises.
A STIRLING engine is a heat engine operating by cyclic
compression and expansion of air at different temperature
levels such that there is a net conversion of heat energy to
Like the steam engine, the STIRLING engine is traditionally
classified as an external combustion engine, as all heat
transfers to and from the working fluid take place through
the engine wall. This contrasts with an internal combustion
engine where heat input is by combustion of a fuel within
the body of the working fluid. Unlike a steam engine’s (or
more generally a Rankine cycle engine’s) usage of a working
fluid in both of its liquid and gaseous phases, the STIRLING
engine encloses a fixed quantity of air.
What’s a STIRLING engine?
As is the case with other heat engines, the general cycle
consists of compressing cool gas, heating the gas, expanding the hot gas,
and finally cooling the gas before repeating the cycle. The efficiency of
the process is narrowly restricted by the efficiency of the Carnot cycle,
which depends on the temperature between the hot and cold reservoir.
The Stirling engine is noted for high efficiency compared to
steam engines, quiet operation, and its ability to use almost any heat
source. The heat energy source is generated external to the Stirling
engine rather than by internal combustion as with the Otto
cycle or diesel cycle engines. Because the Stirling engine is compatible
with alternative and renewable energy sources it could become
increasingly significant as the price of conventional fuels rises, and also
in light of concerns such as peak oil and climate change. This engine is
currently exciting interest as the core component of micro combined
heat and power (CHP) units, in which it is more efficient and safer than a
Invented in 1816 by Robert Stirling
The Stirling engine was originally known as a hot air engine
First closed cycle hot-air engine
Produces power by repeatedly heating and cooling a fixed
amount of gas sealed inside the engine
Intended as safer alternative to the steam engine
History of the Stirling Engine
Replica of the model engine built by Stirling in 1816 to prove his
Robert Stirling built a full-size version to pump water in a local quarry
Operated continuously for two years with an estimated output of two
horse-power (1.5 kW)
Not powerful enough to complete steam engines
Suffered problems due to the poor quality of metal available at the time
An improved Stirling engine was installed at a Dundee iron
foundry in 1843 to drive machinery.
Engine produced thirty-seven horse-power (27.6 kW)
Quieter, safer, and more efficient than the steam engines of the
day, but it was not a success.
More prone to breakages than the steam engine due to its higher
Replaced by a now safer steam engine
Stirling engine was unable to complete with the steam engine
on an industrial scale
Continued in use for smaller applications, the Stirling engine
is remarkably quiet and reliable at lower power outputs.
Stirling engines, unlike steam engines, could be operated
safely by people with no background in engineering.
End of the 19th century: Number of Stirling engines in
operation declined – Internal combustion engine and the
Forgotten about until in 1936: Philips needed an efficient engine to
power radio receivers.
Over the next 20 years: Stirling engine usage investigated for
automotive, solar & submarine applications.
Philips coined the name “Stirling engine”
Computer chip cooling
Backup power supply for submarines
Application of the Stirling engine
Automobiles using Stirling engines:
Research led by General Motors and Ford – not a
success Low power to weight ratio More expensive
than internal combustion engines for same power
Require a longer warm up time.
Today, the engine is receiving renewed interest as a
means of generating electricity. Emphasis on sustainable
energy has brought attention to the engine’s ability to
convert a wide variety of heat sources, such as focused
sunlight and waste
heat, into mechanical work. Figure 2 shows a solar
concentrator whose parabolic dishes are focused on the
expansion cylinder of a Stirling engine. This station alone is
capable of generating 25 kW in full sunlight, enough to
power a mid-sized house. The engines can also be
retrofitted to existing power stations, where they can
scavenge waste heat from the cooling systems to generate
A Stirling engine is a reversible system; given mechanical
energy, it can function as a heat pump or cooling system. Below -40°
C, there are no refrigerants suitable for use in a Rankine style cooler.
Since the Stirling engine relies only on the input of mechanical
energy to supply a temperature gradient, it is a highly competitive
method of cooling in the cryogenic market. Similarly, a heat pump
using a Stirling system takes advantage of the developed temperature
gradient to move ambient heat from the environment into a space,
such as abuilding.
Computer chip cooling :
Micro-Star International Co., Ltd, Taiwan. Miniature Stirling
engine. Uses heat from the processor to cool the processor
MSI claim the engine is 70 per cent efficient.
Stirling engine powered submarines
Remarkably quite – backup to primary
modern diesel-electric engines when a
silent approach is required Stirling
engines are used to power a 75kW
How does the Stirling engine work?
Piston linked to a circular disc known as a flywheel.
Flywheel converts linear movement to rotational movement.
Flywheel’s momentum needed for continuous operation.
Mechanical energy generated from temperature difference.
Stage 1 Expansion(Heating)
Power producing phase cycle Gas at hot end
Expands to drive power piston.
Stage 2 – Transfer
Gas is moved around the displacer to the cold end.
Stage 3 – Contraction (Cooling)
Gas has moved to the cold end. Gas cools and
contracts, allowing the piston inward.
Stage 4 – Transfer
Power piston is top of its stroke, ready to start the
power output. Gas transferred to hot end
A STIRLING engine consists of a number of basic
components, which may vary in design depending on the
type and configuration. The most basic are outlined as
STIRLING ENGINE MAIN COMPONENTS
A flywheel is a rotating mechanical device that is used to
store rotational energy. Flywheels have a significant moment of
inertia and thus resist changes in rotational speed. The amount of
energy stored in a flywheel is proportional to the square of
its rotational speed. Energy is transferred to a flywheel by
applying torque to it, thereby increasing its rotational speed, and
hence its stored energy. Conversely, a flywheel releases stored
energy by applying torque to a mechanical load, thereby
decreasing the flywheel's rotational speed.
Common uses of a flywheel include:
Providing continuous energy when the energy source is
discontinuous. For example, flywheels are used
in reciprocating engines because the energy source, torque
from the engine, is intermittent.
Delivering energy at rates beyond the ability of a
continuous energy source. This is achieved by collecting
energy in the flywheel over time and then releasing the
energy quickly, at rates that exceed the abilities of the energy
Controlling the orientation of a mechanical system. In
such applications, the angular momentum of a flywheel is
purposely transferred to a load when energy is transferred to
or from the flywheel.
A piston is seated inside each cylinder by several
metal piston rings fitted around its outside surface in machined
grooves; typically two for compressional sealing and one to seal
the oil. The rings make near contact with the cylinder walls
riding on a thin layer of lubricating oil; essential to keep the
engine from seizing and necessitating a cylinder wall's durable
During the earliest stage of an engine's life, its
initial breaking-in or running-in period, small irregularities in
the metals are encouraged to gradually form congruent grooves
by avoiding extreme operating conditions. Later in its life, after
mechanical wear has increased the spacing between the piston
and the cylinder (with a consequent decrease in power output)
the cylinders may be machined to a slightly larger diameter to
receive new sleeves (where applicable) and piston rings, a
A piston is a component of reciprocating engines,
reciprocating pumps, gas compressors and pneumatic cylinders,
among other similar mechanisms. It is the moving component that
is contained by a cylinder and is made gas-tight by piston rings. In
an engine, its purpose is to transfer force from expanding gas in
the cylinder to the crankshaft via a piston rod and/or connecting
rod. In a pump, the function is reversed and force is transferred
from the crankshaft to the piston for the purpose of compressing
or ejecting the fluid in the cylinder. In some engines, the piston
also acts as a valve by covering and uncovering ports in the
A piston ring is a split ring that fits into a groove on the
outer diameter of a piston in a reciprocating engine such as
an internal combustion engine or steam engine.
The three main functions of piston rings in reciprocating
engines are :
1.Sealing the combustion chamber so that there is no transfer of gases
from the combustion chamber to the crank.
2.Supporting heat transfer from the piston to the cylinder wall.
3.Regulating engine gases consumption.
Oil ring is used for If the lubrication is passing through at top
of the cylinder and that time the oil ring is stop the oil.
It is placed on bottom of the piston.
The displacer is a special-purpose piston, used in Beta and
Gamma type Stirling engines, to move the working gas back and
forth between the hot and cold heat exchangers. Depending on
the type of engine design, the displacer may or may not be
sealed to the cylinder, i.e. it may be a loose fit within the
cylinder, allowing the working gas to pass around it as it moves
to occupy the part of the cylinder beyond.
In a reciprocating piston engine, the connecting rod is connected
to the piston to the flywheel. Together with the crank, they form a simple
mechanism that converts reciprocating motion into rotating motion.
Connecting rods may also convert rotating motion into reciprocating
motion. Historically, before the development of engines, they were first used
in this way.
As a connecting rod is rigid, it may transmit either a push or a pull and
so the rod may rotate the crank through both halves of a revolution, i.e.
piston pushing and piston pulling. Earlier mechanisms, such as chains,
could only pull. In a few two-stroke engines, the connecting rod is only
required to push.
Today, connecting rods are best known through their use in internal
combustion piston engines, such as automotive engines. These are of a
distinctly different design from earlier forms of connecting rods, used in
FINALEY ASSEMBLE THIS PARTS AND RUNNING
Operate using any available heat source.
Closed cycle - gas is unpolluted.
Simple engine design.
Operates at lower pressures.
No phase changes take place in the engine
Continuous combustion - lower emissions/higher efficiency
Small engine sizes possible
Greater flexibility of applications.
MERITS OF STIRLING ENGINE
Low power to weight ratio
More expensive than internal combustion engines for same
Require a longer warm up time
Efficiency drops if the temperature difference between the hot
and cold ends decreases.
Difficult to vary the power output
Sealing of Stirling engines is extremely difficult.
DEMERITS OF STIRLING ENGINE