From the description of the steam engine model:
A precursor to the jet engine, Heron's steam turbine was the first of its kind to extract thermal energy from pressurized steam and convert it into rotary motion. The desktop steam turbine is powered by an alcohol burner that heats a sphere boiler holding 2/3 oz. of water, evoking the metal cauldron that heated Heron's original aeolipile. When steam is generated, it is expelled through two nozzles on the sphere pointing in opposite directions, generating thrust that rotates the sphere on its axis up to 2,500 rpm.
Here's where you can learn more about this working model of Hero's steam turbine.