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The Analysis of a…. Stirling Engine. Why a Stirling Engine?. Here is what we wanted to learn: How do stirling engines work? Which design aspects have the greatest effect on their performance? How do they compare to more common engines? Where would a stirling engine be used?.
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The Analysis of a… Stirling Engine
Why a Stirling Engine? Here is what we wanted to learn: • How do stirling engines work? • Which design aspects have the greatest effect on their performance? • How do they compare to more common engines? • Where would a stirling engine be used? http://www.dansdata.com/images/blog/msiairpowerfan2_s.jpg http://i.ytimg.com/vi/osNluWPOpJ0/0.jpg
What is a stirling engine? • Gamma type stirling engine • A stirling engine uses heat flux from a temperature differential to create a cycle of expanding and contracting air • The expansion and contraction causes a pressure change which moves the green piston • The green piston rotates the shaft and the flywheel which moves the displacer • Why are they 90° out of phase?
Background • Invented in 1816 by Robert Stirling • First used in Dundee Foundry in Scotland for power generation • Applications include mechanical and electrical power generation, cryogenic cooling and HVAC. • Typical efficiency is 30-50% of Carnot cycle (15-30% overall)
Solar Power approximately 31% efficient
Experiment • We measured… • System dimensions • Temperature difference • RPM
Calculations • We assumed… • Steady state heat reaction for engine • Laminar flow • Insulated cylinder • No loss through bottom of coffee cup or sides of plate • Frictionless • Significant calculations: • Work output per cycle • Heat loss from mug
Power V1 = minimum volume V2 = maximum volume
Overview • Plate properties and dimensions have no effect on power output for steady-state • A larger diameter cylinder can operate on a smaller temperature difference • Gases with large (m*R) J/kg, such as helium, are the best working fluids • Temperature difference is directly proportional to power output Efficiency comparison: - Stirling engine: 12% - 20% - Steam engine: 8% - Internal combustion: 35% Stirling engines are increasingly being used in solar power applications. They are useful because they are extremely low maintenance and do not require fuel to run. Renewable energy!