A look at some air engine working cycles
The Stirling cycle
The Rider or Compression engine
The Ericsson cycle
The Ringbom cycle, named after the inventor Ossian Ringbom of Helsinki, Finland.
Free Piston engines
The Manson cycle. A valved single piston/displacer engine so called after a design by A.D Manson published in Newnes Pratical Mechanics in 1952. The design also appears in a patent granted in Germany to Michael Ruppel in 2000.