Document Outline

How does a Stirling engine work?

Today we have ecology problems and energy problems. The world needs a clean and environmental
power source. Stirling engines are able to use many kinds of fuel and achieve a high theoretical
efficiency.

Structure of Stirling engines

History of Stirling engines

Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/begin.htm [04/07/2006 2:27:07 PM]

How does a Stirling engine work?

How does a Stirling engine work?

Koichi Hirata (khirata@gem.bekkoame.ne.jp)

Step 1 Characteristics of air

Let's fit a rubber to a can like Figure 1. You can understand easily that the rubber expands when the can is
heated (Figure 2), and the rubber contracts when the can is cooled (Figure 3). It is caused that a pressure of
the air in the can works to the rubber when the air is heated, shown in allows of Figure 2. Of course, you
cannot see the pressure by your eyes.

Step 2 What is a displacer piston?

Next, let's put in a piston into the can like Figure 4. A diameter of the piston must be somewhat smaller than
that of the can, because the piston works to move (displace) the air up and down in the can. And, please heat
the bottom side of the can and cool the upper side of the can. After it has enough temperature difference,
move the piston up and down by your hand. When the piston is moved up, the rubber expands because there
is a lot of hot air in the can (Figure 5). It corresponds to Figure 2. When the piston is moved down, the rubber
contracts because there is a lot of cold air in the can. It corresponds to Figure 3.
In the case of the Stirling engine, this piston, which moves (displaces) the air and make the pressure changes
is called a displacer piston.

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How does a Stirling engine work?

Step 3 Crank mechanism ~ from piston motion to rotation ~

Do you understand about the characteristics of the air and the work of the displacer piston? They are very
important to understand how does the Stirling engine work.
First, connect from the piston and a bent wire with a thread like Figure 6. When the bent wire is rotated, the
piston is moved up and down. This is called a crank mechanism.
Please heat the bottom side of the can and cool the upper side of the can, similar to above description. When
your hand rotates the bent wire, the piston is moved up and down, and the rubber expands and contracts
repeatedly (Figure 7).

Step 4 Power piston ~ function of the rubber ~

The Stirling engine converts from the motion of the rubber to the rotation of the bent wire. Please connect
from the rubber to the bent wire with a rod. In this time, a force of the rubber (expansion and contraction) has
to be the direction, which rotates the bent wire. In short, you must bend the bent wire the just right angle (90

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How does a Stirling engine work?

degrees) from the piston like Figure 8 and 9.

Step 5 Flywheel ~ for the smooth rotation ~

This engine has not worked yet. If you try to work this engine (Figure 8 and 9), the rubber keeps the most
expansion or contraction. In order to rotate smoothly and repeatedly, you must fit a rotated mass with the bent
wire. It is called a flywheel.
Generally, the flywheel is circular like Figure 10. But at this point, please bend the end of the bent wire, and
fit a mass at the edge of the wire like Figure 11. The mass works as the flywheel and to be balanced to the
weight of the piston. So, you must fit the mass against the piston.

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How does a Stirling engine work?

Step 6 It is the Stirling engine

Finally, the Stirling engine is completed.

Do you understand how does the Stirling engine work?

Yes.

No.

I have known the principles before seeing this page.

Do you think that above description is easy to understand?

Yes, it is easy.

No, it is not easy.

If you have any suggestion about this page, please tell me it.

If you can, please tell me your name, e-mail address and country.

Name:

Country:

E-mail address:

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How does a Stirling engine work?

P.S.: When the Stirling engine is understood, it is important that the knowledge of the characteristics of air
(Thermodynamics), the crank mechanism and the flywheel (Mechanics and Mechanical Vibrations). I have
tried to explain about them as simply as possible. Please contact me if you find incomprehensible contents or
any errors, and have any your opinions. I hope that this description becomes more suitable for every young
student. Permission is hereby granted, by author, to print and distribute this description. Thank you.

Koichi Hirata

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Structure of Stirling Engines -English-

Structure of Stirling Engines

Stirling engines have two pistons that create a 90 degree phase angle and two different temperature
spaces. The working gas in the engine is perfectly sealed, and doesn't go in and out to the atmosphere.
Stirling engines can be classified as two pistons type Stirling engines and displacer type Stirling engines.
The two pistons type Stirling engine consists of two power pistons. The displacer type Stirling engine
consists of one power piston and a displacer piston.

Two pistons type Stirling engine

The two pistons type Stirling engine is
shown in this figure. A space above a hot
piston is always heated by a heat source.
A space above a cold piston is cooled
always.

Please click next buttons and you will see
a operation principle of the two piston
type Stirling engine.

Stillness

Animation

(Netscape2.0 is demanded.)

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Structure of Stirling Engines -English-

Displacer type Stirling engine

The displacer type Stirling engine is
shown in this figure. A space above a
displacer piston is always heated by a
heat source. A space below the displacer
piston is cooled always. The displacer
piston displaces hot air and cold air.

Please click next buttons and you will see
a operation principle of the displacer type
Stirling engine.

Stillness

Animation

(Netscape2.0 is demanded.)

Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/struct.htm (2 of 2) [04/07/2006 2:32:00 PM]

Principle of Two Pistons Type Stirling Engines -English-

Principle of Two Pistons Type Stirling Engines

Return to Structure of Stirling Engines

Gas expands when heated, and contracts when cooled. Stirling engines move the gas from the hot side of
the engine, where it expands, to the cold side, where it contracts.

HEATING
Let's start from a top dead center of a hot piston. The hot piston moves to the upper part of the cylinder
and a cold piston moves to the lower part of the cylinder during first 90 degree revolution. The working
air is moved from cold space to hot space. And the pressure in the engine is inclused.

EXPANSION
Next 90 degree revolution, the two pistons move both lower part accepting the air pressure. The engine is
gotten the power of the operation.

COOLING
The crank shaft is revoluted by saved power in a flywheel next 90 degree. The hot piston moves to the

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Principle of Two Pistons Type Stirling Engines -English-

lower part and the cold piston moves to the upper part. The air is moved from the hot space to the cold
space. And the pressure in the engine is decreased.

COMPRESSION
The two pistons are moved to upper part by the compression of the air during next 90 degree. The engine
is gotten the power of the operation in this time.

The two pistons type Stirling engine operates to repeat these distances.

Have you understood the principles of the two pistons type Stirling engines?

Yes, very well!

Yes.

No.

No, at all!

I have known the principles before seeing this page.

If you can, please tell me your name, e-mail address and country.

Name:

Country:

E-mail address:

Koichi Hirata

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History of Stirling Engines No.1 -English-

History of Stirling Engines No.1

The Stirling engine was invented by Robert Stirling in 1816. He was a Scottish minister. At that time,
Stirling engines were recognized as a safe engine that could not explode like steam engines of that era
often did.

Stirling Engine of Robert Stirling (1816)

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History of Stirling Engines No.2 -English-

History of Stirling Engines No.2

Since then, many kind of Stirling engines were manufactured with a view to increasing the output and the
efficiency. But the engine had been made a poor production, in the back of Otto engine and Diesel
engine. Because Otto engine invented by N. Otto on 1877 and Diesel engine invented by R. Diesel on
1893 were higher capacity than Stirling engine in those days.

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History of Stirling Engines No.2 -English-

Stirling Engine in the early days

I took this picture in 6th International Stirling Engine

Conference, Eindhoven (the Netherlands) on 1993.

Go to Before Page

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History of Stirling Engines No.3 -English-

History of Stirling Engines No.3

Stirling Engine was taken notice again, when PHILIPS Corporation started to research on Stirling engine
as the power source of portable generator in about 1940. A 200 W Class Stirling engine was completed
in about 1950. But the engine was not spread, because the transistor that can work at low power was
invented.

Stirling Generator of PHILIPS Corporation (the Nethrland)

http://www.bekkoame.ne.jp/~khirata/english/history3.htm (1 of 2) [04/07/2006 2:34:23 PM]

History of Stirling Engines No.3 -English-

I took this picture in 6th International Stirling Engine Conference,

Eindhoven (the Netherlands) on 1993.

Go to Before Page

---

Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/history3.htm (2 of 2) [04/07/2006 2:34:23 PM]

History of Stirling Engines No.4 -English-

History of Stirling Engines No.4

Since then, Stirling engine had been studied in Europe and America. The engine had been started to
develop rapidly with effect of oil-shock in 1973. In Japan, the engine was started to research later than
Europe and America about 20 years.

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History of Stirling Engines No.4 -English-

2kW Class Experimental Stirling Engine

(Ship Research Institute, Japan)

Go to Before Page

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Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/history4.htm (2 of 2) [04/07/2006 2:34:57 PM]

History of Stirling Engines No.5 -English-

History of Stirling Engines No.5

Now, Stirling engine is studying lively in the world. For examples, Solar Stirling engine, hot spring
Stirling engine, underwater Stirling engine, air-conditioning Stirling system, Stirling refrigerator and .....

Stirling Engines in Near Future

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LSE-01

Model Stirling Engine "LSE-01"

This engine is a two piston type Stirling engine with a cap type heater made of stainless steel and it does
not have a regenerator. Its cooling system is a natural convection cooling by air. The pistons and
cylinders use medical syringes made of glass, so the engine has few leakage of the working gas and small
friction. To minimize the friction loss, at most of drive parts are used ball bearings. This engine has high
speed performance. It can rotate about 3000 rpm.

Model Stirling Engine "LSE-01"

http://www.bekkoame.ne.jp/~khirata/english/lse01e.htm (1 of 2) [04/07/2006 2:36:13 PM]

Model Stirling Boat with MSE-01

Model Stirling Boat with MSE-01

Following picture is a model boat with MSE-01.
Ship type is named Short Water Area Twin Hal (SWATH).

Model Boat with MSE-01

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Development of MSE-01 Boat

Development of MSE-01 Boat

Return to Model Stirling Boat with MSE-01

Model Stirling Engine "MSE-01" had been loaded some type model boats.

At first, model boat was a general catamaran.

The engine was loaded SWATH, but the boat overturned.

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Development of MSE-01 Boat

The boat was installed with the floats on front and side, but it overturned too.

Now, the boat is becoming this picture.

Return to View of Model Stirling Engines

Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/h_mse01.htm (2 of 2) [04/07/2006 2:37:43 PM]

Model Stirling Amphibian Ship with MSE-02

Model Stirling Amphibian Ship with MSE-02

Detail Information of the MSE-02

This amphibian ship is powered by the 5W class Stirling Engine "MSE-02". Running Speed of this ship
is about 2 km/hour on the land and on the water.

Amphibian Ship with MSE-02

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Model Stirling Amphibian Ship with MSE-02

Return to View os Model Stirling Engines

Koichi Hirata

http://www.bekkoame.ne.jp/~khirata/english/mse02e.htm (2 of 2) [04/07/2006 2:38:16 PM]

Model Stirling Boat with MSE-05

Model Stirling Boat with MSE-05