Types of Stirling Engines

Although there are several different kinds of Stirling engines they all have two major things in common:
                  
                                                                   1.)  The gases inside a Stirling engine (whether they be normal air, or helium, or hydrogen, etc..) never leave the engine.

                                                                  2.)  The Stirling engine uses an external heat source which could be anything; solar, geothermal, fire,plant compost, 
                                                                                   nuclear, anything what-so-ever that can apply the necessary heat to the hot end of the engine.


                                                   The two most common types of Stirling engines are the Displacer Stirling engine and Two-Piston Stirling engine.

                                       
                                            
                                                                        Displacer Stirling Engine:
 
          The Displacer Stirling engine operates using a piston and a displacer.  The displacer is mounted so it doesn't touch the walls of the cylinder so air can move around it into the cool/hot ends and the power cylinder containing the piston.  The displacer moves the air from the hot end to the cold end and back.  When the air gets hot it expands, pushing out on the piston.  As the air cools is contracts and the piston is pulled in and the cold air is pushed back into the hot end where it repeats the process.

    Pictured to the right is a cross-section of a Displacer Stirling engine and to the left is one that can run off of just the heat from your hand.




pic from http://members.iinet.net.au/~velletri/stirlingengines/Stirling_Anime.html  




                                                                                                                                                                                                                                                                                                                                                                                                                                pic from http://www.stirlingengine.com/

                                        Two-Piston Stirling Engine:


   
       The Two-Piston Stirling Engine uses two pistons to pump the gas from the hot end to the cold.  First the air expands in the hot end, pushing the hot end piston inward while the cold end stays relatively in place.  Next the cool piston draws in air from the hot end allowing the hot piston to move outward.  The cool piston then compresses the gas as the cooling device remove heat from the air. Lastly the air is pushed/drawn into the hot end where it begins it's cycle all over again.


Pictured on the left is a cut-a-way view of a Two Piston Stirling Engine,
       on the right is a 3D model

pic from www.cnczone.com/forums/showthread.php?t=21919