LTD Stirling design/optimization

[bigsteve]

Does anyone have some rules of thumb, or better yet, mathematical equations covering gamma-type Stirling engines? I want to make one from junk around the house, but I don't want to guess at it. My specific questions are about the volume of the power cylinder (would I just use the ideal gas law [V1*T2 = V2*T1, with the temps in rankines], from my desired temperature differential?), the volume of the displacer piston in relation to the power cylinder, the mass of the displacer piston and the mass/diameter of the flywheel.

Also, does anyone know if the displacer cylinder has to be exactly 90° off of the power cylinder, or can it be just close - I'm thinking of powering the displacer with neodymium magnets to get a better seal.

 

[kevincoxshall]

Hi
Have you looked at the schmidt theory calculations. At first they seem difficult but they are quite easy to follow.
http://www.bekkoame.ne.jp/~khirata/academic/schmidt/schmidt.htm
Then plot the PV pressure volume curve and the area inside this closed loop is the power of the system.
They do not have to be at the 90 degree angle at all. The ideal cycle is a square wave form so the sine wave is the closest match we can achieve without complex mechanisms. If you could create a changeable angle to tune it that would be good.
If it was me i would start with a wokring model from Jerry Howell and alter it slightly. Designing them is a difficult as the mechanism has to be extremely frictionless due to the low power output.