The Analysis of a…

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?

 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?

 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)

approximately 31% efficient

We measured…  System dimensions  Temperature difference  RPM

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

V 1 = minimum volumeV 2 = maximum volume

q in = Watts Work = 0.14 Watts q out = Watts

 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: 15% - 30% - 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!