The regenerator has a central axis. The regenerator has a multitude of web layers wound around the central axis. The web layers are formed by two or more metal fiber or metal wire having webs wound around the central axis. When observed from the central axis to the outside of the regenerator, at least one web layer of a web of a first width is followed by a web layer of a web of a width larger than the web of a first width.

An external combustion engine is disclosed. The external combustion engine includes a working fluid and a burner element, at least one heater head defining a working space, at least one piston cylinder containing a piston, a cooler, a crankcase including a crankshaft for producing an engine output, a rocking beam, a piston rod connected to the piston, a rocking beam driven by the piston rod, and a connecting rod connected at a first end to the rocking beam and at a second end to a crankshaft to convert rotary motion of the rocking beam to rotary motion of the crankshaft. The external combustion engine also includes an airlock space separating the crankcase and the working space for maintaining a pressure differential between the crankcase housing and the working space housing and an airlock pressure regulator connected between the crankcase and one of the airlock space and working space.

A new thermal engine design and novel hot air inlet provide a high-efficiency hot-gas free-piston Stirling engine design.