Analysis of Free-Piston Stirling Engine/Linear Alternator Systems Part 1: Theory

Abstract: Linear alternators are frequently proposed and used as electric-energy-producing devices in connection with free-piston Stirling engines. However, while considerable research work has been done on this type of engine and on its dynamics and thermodynamics, there are only few studies dealing with the linear alternator and its interaction with both the engine and the load. The objective of this article is to provide a mathematical model able to describe a free-piston Stirling engine/linear alternator combination as a whole system, where the electric, dynamic, and thermodynamic aspects are linked together. The engine/alternator system drives through a tuning capacitor a static load. In particular the method is applied: 1) to calculate the force resisting the piston motion produced by the alternator and the associated load, and 2) to derive a criterion of electric, dynamic, and thermodynamic steady-state operation of the machine.