https://www.youtube.com/watch?v=Sk0_ZYTseqs
How is it working?
Hi, it looks like hot air is sucked into the cylinder. The cylinder is closed. The hot air inside the cylinder cools and pulls the piston back toward TDC, the cylinder is opened and the cycle repeats. The flywheel is unbalanced for gravity assist.
This engine is known as a "flame licker" engine or by its German equivalent
for obvious reasons. It is sort of a mixed internal/external combustion
engine. Look these up on youtube and google to see some live examples.
:S:MarkSCoffman
Also google Stirling engine. At least a relative to that one.
Its all about exchanging heat to expand and contract air inside an enclosure like a cylinder. This force pistons to start moving.