Thermo Acoustic Engine

This single cylinder thermo acoustic engine operates from a tiny methylated spirits (denatured alcohol) flame. The optimum running speed is 2700rpm when warmed up fully. As far as we know this is the fastest thermo-acoustic engine available.

The thermo acoustic engine is known by several names, including resonant engine, lag engine, lamina flow engine and traveling wave engine. This engine, with its transparent main tube, beautifully and elegantly demonstrates the principles behind such engines.

How does it work?

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.

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