PASCO SE-8575 VISIBLE STIRLING ENGINE - Manual (Page 5)

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012-06055A The Visible Stirling Engine
®
Introduction
The PASCO Visible Stirling Engine is a tool to teach
students how engines work and to excite them about
physics.
Stirling engines have the most efficient cycle in the
world. Does that mean the Model SE-8575 engine is the
most efficient engine in the world? No. It means that
Stirling engines with regenerators have a cycle that
matches the Carnot cycle. The Carnot cycle determines
the maximum theoretical efficiency of a heat engine.
temp hot – temp cold
temp hot
×
100 = % efficiency
The temperatures must be measured in absolute degrees
(Kelvin or Rankine) for this formula to work.
No real engine (one that could be built in a machine shop)
can achieve the Carnot theoretical efficiency. But real
Stirling engines come closer to the Carnot cycle than any
other engine! Some research Stirling engines have
attained 50 percent of the theoretical Carnot efficiency!*
The efficiency of the SE-8575 is calculated in the experi-
ments section of this manual.
If Stirling engines are so efficient, why don’t we have
them in automobiles? The best answer to this question is
an easy demonstration. Start the SE-8575 on nearly
boiling water and wait for it to get up to full speed. Then
remove the engine from the heat source and notice that it
keeps running for a few minutes.
It is very easy to do an engineering trick to make the
engine stop instantly, but there is nothing in the world that
can be done to make a Stirling engine start instantly.
Today’s drivers want to be able to start their cars instantly
(if not sooner) and some of them want to burn rubber
across the parking lot. Stirling engines can’t do that.
Research automobile Stirling engines generally take
about 30 seconds before the car can be driven away.
Modern drivers do not want to wait.
Computer Compatibility
Photogates may be used to measure the engine rpm.
Additional Equipment Recommended
You may also find it convenient to use:
• A coffee cup.
• A clear water glass
• A Styrofoam dinner plate or a Styrofoam bowl.
* “Stirling Machines: An Emerging Technology Paradigm”
by B. Ross and L.B. Penswick, page 8.