A. Clearance is the space between the cylinder head and the piston head with the ports included.
Q. What is the principal which distinguishes a non-condensing from a condensing engine?
A. Where no condenser is used, and the exhaust steam is open to the atmosphere, it is a non-condensing engine.
Q. Why do you condense steam?
A. To form a vacuum and thus remove the atmospheric and back pressure that would otherwise be on the piston, thereby getting more useful work out of the steam.
Q. What is meant by vacuum?
A. A space void of all pressure.
Q. How can you maintain a vacuum?
A. By the steam used being constantly condensed by the cold water or cold tubes, and the air pump constantly clearing the condenser.