Miniature Single Cylinder Thermo Acoustic Engine Runs on Alcohol

Posted by: Jeremy Patterson on 11/17/2021

This single cylinder thermo acoustic engine operates by converting a denatured alcohol flame. The thermo acoustic, also known as a resonant engine, lamina flow engine, traveling wave engine and lag engine. With it’s clear tube and simple-but-functional design, this engine is certainly one of the simplest engine designs we’ve seen, while remaining simultaneously elegant in appearance and function.

If you’re like us, you want to know how it works, and to be totally honest, we really don’t fully grasp the physics behind it, so we’re going to paste the description from the video itself below and you can learn along with us:

“The thermo-acoustic engine works by converting sound waves into motion. The sound waves are generated by heating one end of a ‘stack’ of coiled material and allowing the other end to remain cool. The engine is fired by a small spirit burner. By heating the end of the coiled ‘stack’ a bouncing pressure wave is set up inside the tube. The crucial element in the thermo-acoustic engine is the ‘choke’, which reduces the bore of the tube. It is the pressure fluctuations that ultimately drive the engine, in the expansion phase the piston is pushed outwards, in the contraction phase the piston is pulled inwards. The engine requires a small push of the flywheel for it to start. Without the small push the pressure and velocity of the standing wave remain at equilibrium. Move the flywheel and the equilibrium is shifted, thus allowing the cyclic variations to take place.” – Grand Illusions video description

Now, that explains how it works, and even after reading it over a couple of times, I personally cannot grasp how the engine functions to remain running with no actual combustion taking place. I understand the general theory but certainly not well enough to build one myself or explain it to others. However, I don’t have to fully grasp everything taking place to know that this is a beautiful way to display the theory itself and maybe if I keep watching this little engine chug away, everything will “click”!