The Stirling Engine

Sean Bohun, University of Ontario Institute of Technology

 

A Stirling engine is an externally heated engine developed in the 1800's as a safe alternative to the steam engine.  It functions by repeatedly heating and cooling a sealed amount of gas, and since the gas is sealed, there are no intake or exhaust valves as one would find with other piston engines.  One of the modern uses of Stirling engines is as a refrigerator when acted in reverse.  That is, motion applied to the shaft sets up a temperature differential across the tube containing the sealed gas.

The goal is to develop a mathematical model of how the Stirling engine operates by investigating how the temperature distribution on the sealed tube influences the gas flow inside the sealed chamber which drives the pistons and ultimately drives the flywheel.  In realistic machines the working spaces are more accurately approximated with an adiabatic assumption rather than an isothermal assumption.  This means that no heat (thermal energy) is transferred by the enclosed gas which is the opposite extreme of the isothermal case where heat transfer is maximized.  How would changing the working gas or using an adiabatic assumption allow one to make insights into perhaps a better engine design?