Stirlingengineforum.com

Hello everyone.
My name is Thibaut, I'm a French engineering student.
I'm working on the design and the manufacturing of a beta type Stirling engine. I've done some parts by 3Dprinting, and I've tried to machine a crankshaft, but it is too heavy.
I need some information in order to understand the thermodynamic functioning of the engine and modelise it (mathematically). If you have some informations, I'm more than interested !
Regards
ThibautB

Hello from Texas ThibautB,
Mathematically there are numerous variations to consider when designing the platform. That is partly why good running Stirling's are so elusive. I would start with the Ideal Gas Law (Try here: http://www.calctool.org/CALC/chem/c_thermo/ideal_gas ). You will need to know what your theoretical input and output temperatures will be. From there you can use the ideal gas law to determine the maximum and minimum volumes that your working gas will expand and contract to at any given pressure. Once you know the volumes, you can design the bore and stroke you want that will maximize use of the expansion phase. You can always look at a rhombic drive for a beta, those are proven and seem to do the job fairly well balanced.
Thermodynamics will need to be determined once you decide on bore(s) and stroke. Typically, unless you are building a pancake style, a smaller diameter bore than say, 5cm just the solid case is usually enough for adequate heat transfer area. Between 5 and 10cm internal fins will help maintain an adequate heat transfer area as the volume to surface area increases exponentially. Above 10cm you should probably consider moving away from the beta to an alpha with an external heater/reg/cooler to maintain proper heat transfer rates/area.

Good Luck,
Jamie