Further Evaluations of Low-Temperature Difference Stirling Engine Characteristics

Low temperature-difference Stirling engines, while of limited perceived applicability, offer excellent opportunities to challenge the existing state of theoretical knowledge with low-cost yet revealing experimentation. The general availability of a well-performing low-cost Ringbom-Stirling engine provides an excellent basis for widespread experimentation based upon a common platform. Whereas some broad characteristics of this engine have already been presented this paper addresses in particular a number of aspects in regard to displacer springing. Most particularly, the gravitational effects on a vertically-oriented free displacer may be inferred with reference to a spring-suspended displacer. At the same time, theoretical predictions regarding sprung-displacer performance can be tested.