Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Quite interesting engines these 


http://birkpetersens.blogspot.com/2014/04/non-compression-engine.html


https://www.eldensengines.com/Lenoir/Lenoir.HTML

Maybe I'm dense...but I read both of these articles, they both talk about introducing fuel , igniting the fuel with a spark and that pushes the cylinder. ...isn't that   combustion & would that be some kind of compression to push said cylinder ?