Arthur WoolfAn elevation of Woolf's engine

Arthur Woolf was a Cornish engineer who invented something like a compound engine. He was born 1766 and died 1837. The engine combined expansion, compound and the Cornish principle in one engine. Very remarkable since the engine was designed already in somewhere 1810. At that time high-pressure steam was very new and a thing like compound was not scientifically understood yet. It was obvious he didn't understand compound, since his first engine used a ratio between high and low cylinder of 1 to 20! With no doubt this engine didn't perform properly.

Lateron he designed working engines like in the animation below. The engines were at about 2,5 times more efficient than Watt's engines. Many engines were built, especially in France.

Animation of the Woolf engine



The engine has two cylinders to perform the compound principle. We can be sure he used steam of very low pressure, max 5 bar. With such a low pressure the use of compound is very arbitrary.

The fresh steam has a cut-off of about 50 %.

During the up-stroke the engine uses the Cornish principle, an equilibrium valve is opened and the space above and under the piston is connected, the pressure up and under the piston is equal and the piston can rise without any friction.

During the downstroke the low-pressure cylinder exhaust to the condensor.

A very interesting engine, far ahead of his time, therefore mister Woolf deserves his place in the list of important steam-engineers.