Vacuum Rotor Engine

This is a Vacuum rotor engine, sometimes called a flame licker engine or atmospheric engine. It is, I believe from the 1920's. It is approx. 7 lb. and overall length is 9" x 6" tall. as the pamphlet shows, it cost $ 6.00 new. It was made by the Rotor Corporation Of America in Dayton Ohio.
I bought this flame licker during my visit to the annual Carlisle, PA Car Show yesterday. It was stuck fast and filthy. It has all the parts that belong to it, so, I took a chance and bought it. I hoped that I could get it to relive for me. After plenty of oil and scotch-brite, I got it to turn over. I added denatured alcohol to the well and wick and it started to pop. After repeated adj. of the wick, it started running and ran for a half hour, non-stop. So, how does it work?
The flame is sucked into the piston chamber as the piston is drawing back, the port cover closes and the hot gases begin to cool. This creates a vacuum in the piston chamber and draws the piston forward and reopens the port to allow another charge of heated air into the chamber, thus starting the process all over again