This engine is also called: flame eater, flame licker, flame sucker, atmospheric engine, vacuum engine, flame dancer, etc.
WARNINGS: Burns possible. This engine gets very hot. It uses flammable liquid fuels in a burner that can easily leak spreading fire to persons and things (note that during shooting this video the burner leaked on my hand and my hand caught fire!) This should not be used by children unless closely supervised by responsible adults.
Based on Wikipedia:
A vacuum engine (aka flame-licker engine, flame-engine, flame-dancer) derives its force from air pressure against one side of the piston, which has a partial vacuum on the other side. At the beginning of an outstroke, a valve in the cylinder head opens and admits a charge of hot, highly expanded plasma and air, which is trapped by the closing of the valve. The charge comes into contact with a water- or air-cooled part of the cylinder and is chilled, causing a drop in pressure sufficient to suck the piston back on the return stroke. The valve opens again in time for the piston to expel the now-cooled gases before the next outstroke begins.
All early steam engines, especially the pioneering Boulton and Watt engines, operated with almost atmospheric pressure steam.
Ideal Thermodynamic Process
One of the major issues of this engine is that the efficiency is extremely poor. Because the heat source is not contained, only a small portion of the potential fuel consumed powers the engine. Because Engine efficiency is defined by the relationship between the amount of work done and the potential energy in the fuel consumed, in the vacuum engine only a small amount of the burning fuel is being used to power the engine, the rest is lost to the surrounding atmosphere.
Flame licker gif: Benutzer:Karl Bednarik GNU 1.2
Walking beam gif: Emoscopes GNU 1.2