Stirling engine
belongs to external combustion engine. It is based on Stirling cycle with
Carnot efficiency. Carnot efficiency is the most efficiency of heat engine
working from high temperature to cool temperature. However, the pressure of
working media changes steadily in Stirling cycle system. Therefore Stirling
engine works much more silently than internal combustion engine. The latest
stirling engine use Hydrogen and natural gas as its heat source. If the hot cylinder
reaches 700 ℃, the engine can start to work. And the lower ambient temperature,
the higher efficiency it will get. Therefore stirling engine is a good choice
in high altitude areas.
The stirling cycle
can be divided into four parts: Isothermal compression, isochoric heating,
isothermal expansion and isochoric cooling.
1.1 Various Design
Schemes
Fig.1 Two-piston α
type stirling engine Fig.2 Displacer β type stirling engine[1]
Fig.1 shows α type
stirling engine with two cylinders. One is expansion cylinder with high
temperature and the other one is compression cylinder with cool temperature.
The power piston is the cold one and 90 degree phase angle is needed here.
However, in the β type stirling engine, there is only one cylinder separated by
a loose fitting displacer. Cool end is at top and hot end is at bottom.
Nowadays there are
several typical car models with stirling engine. We can make a model car by
ourselves with simple parts.
Fig.3 A model car
with stirling engine[2] Fig.4 Parts of
that model car[2]
1.2 Design Steps and
Manufacturing Requirements
The first step is to
simulate 3D model based on preliminary design in CatiaV5. Second, the assembly
drawing and part drawing are both needed from 3D model. At the same time,
materials should be added in the structure for intensity inspection and
structure optimization. Third, all the nonstandard parts are manufactured by
CNC machine based on the determined dimensions. Last but not least, assemble
the model car and check working status.
When we want to make
the Stirling engine, it needs several simple parts like copper velvet, cuvette,
plastic tube, syringe, disk, rubber stopper and so on. These parts we can
gather from discarded toys and buy them from online. And for standard parts
like gears in the model car, we can order them from specific factory after we
provide them dimensions of our standard part.
2. Other Applications
of Stirling Engine
2.1 Stirling Solar
Generator
Fig. 5 Solar Power
Generator System[3]
Heat source is needed
in all the stirling engine. If solar energy can be used as heat source instead
of fossil fuel, it will be environmental-friendly. Fig.5 shows the scheme of
solar power generator system. The solar parabolic dish consists of 82 mirrors
can drive 25kw stirling generator and it claims that the efficiency of this
solar generator is 29.4%.[4]
2.2 Stirling System
for Waste Heat Recovery in Cement Plant
Fig.6 Stirling System
for Waste Heat Recovery in Cement Plant[5]
In the cement plant,
waste heat is generated every second which can be used by stirling generator
due to the low quality requirement of heat source in stirling system. Not only
it can save fuels for power plant, but it will reduce the cooling need of waste
heat in cement plant.
[1]
American Stirling Company. “How Stirling Engine Work?” Internet: https://www.stirlingengine.com/faq, Oct.25, 2000
[Jan.28, 2014]
[2]
Q.X. Cao. How to Make a Stirling Engine Model. Shanghai, China: Shanghai
Jiaotong University Press, 2010, pp.135-23.
[3]
A.A. Kecskes. “Stirling Solar Engines: A Whole New Look at Solar Power”
Internet: http://www.beyond.com/articles/sterling-solar-engines-a-whole-new-look-at-solar-8579-article.html#Comments,
April.9, 2010 [Jan.28, 2014]
[4]
B. Bart. “Climate and Fuel.” Internet: http://www.climateandfuel.com/pages/solar.htm,
Sep.10, 2009 [Jan.28, 2014]
[5]
ReGen Power Systems. “Gaseous Waste Heat-to-Power.” Internet: http://www.rgpsystems.com/solutions.html,
Oct.25, 2000 [Jan.28, 2014]
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