Minnesota Boiler License Practice Exam

How many times does a compound engine use the same steam?

1. 1x

2. 2x

3. 3x

4. 4x

The correct answer is: 2x

A compound engine is designed to utilize steam more efficiently than a simple engine by expanding the steam through multiple stages or cylinders. Typically, in a compound engine, the steam is first expanded in a high-pressure cylinder and then transferred to one or more low-pressure cylinders where it is allowed to expand further. This process effectively allows a single quantity of steam to be used more than once as it passes through each cylinder, thus maximizing energy extraction from the steam before it is exhausted. Specifically, in a typical arrangement, the steam can be utilized twice: initially in the high-pressure cylinder and subsequently in the low-pressure cylinder. This is why the answer reflects that the steam is used two times in the operation of a compound engine. While there may be configurations that further utilize steam through multiple cycles, the conventional use in standard discussions about compound engines emphasizes this two-time expansion, illustrating the efficiency gains achieved with this design compared to simple engine arrangements.