A. No. When an engine is working at the rate of 10 horse-power, it is doing 10 horse-power all the time. It is an error to assume that such an engine is doing 10 horse-power per minute, and 10 × 60 equals 600 horse-power per hour. When it is said that an engine uses 20 pounds of steam per horse-power per hour, it is meant that this amount of steam is used per hour for each horse-power developed.
Q. How is the foot-pounds of work done by a steam engine, found?
A. Multiply the average pressure per square inch during the stroke by the number of square inches in the piston, and by the number of feet through which the piston has moved.
Q. What do you understand by the “mean effective pressure”?
A. The mean pressure is the average pressure pushing the piston through the stroke, which is about one-third the pressure in the boiler. There is generally some back pressure working against it, therefore the “effective” pressure is only the difference between the two. It can only be determined accurately by measurements from an indicator diagram.
Q. What is a single acting engine?
A. An engine in which the steam acts on one side of the piston only.
Q. How do you find the “piston’s speed”?