Practical Bellows Seals for Stirling Engines

Rod seals, and to a lesser extent piston seals, are the primary impediments to long life and high reliability for kinematic Stirling engines. Hermetic metal bellows have been successfully demonstrated for 6.9 years and 4 × 10⁹ cycles in a free-piston Stirling engine. A totally different radioisotope fueled free-piston Stirling engine with a flexing metal diaphragm was still operating at last report after more than 12 years and 3 × 10¹⁰ cycles. A concept for implementing long life bellows to function as rod seals and piston seals in kinematic Stirling engines has been developed and is presented for the first time in this paper.