A compound steam engine in which the high pressure and low pressure cylinders have a common piston rod is called a: a. receiver type compound engine b. tandem type compound engine c. Woolf type compound engine d. none of these
The correct answer and explanation is:
Correct Answer: c. Woolf type compound engine
Explanation (Approx. 300 words):
A compound steam engine is a type of steam engine where steam expands in two or more stages for improved efficiency. In this setup, steam first expands in a high-pressure (HP) cylinder and then passes to a low-pressure (LP) cylinder, thereby extracting more energy from the same amount of steam. Depending on how these cylinders are arranged and how steam is transferred between them, compound engines are categorized into several types, one of which is the Woolf type compound engine.
In the Woolf type compound engine, both the high-pressure and low-pressure cylinders share a common piston rod and are usually mounted in tandem—that is, one cylinder is placed directly in line with the other. The pistons of both cylinders move together on a common rod and crankshaft. This compact arrangement eliminates the need for a receiver (a chamber that temporarily stores steam between cylinders), as the steam flows directly from the HP cylinder to the LP cylinder. This direct steam transfer reduces energy losses due to condensation and re-evaporation, making the system more thermally efficient.
This type of engine was named after Arthur Woolf, an engineer who developed it in the early 19th century to enhance the fuel efficiency of steam engines. It was particularly popular in stationary engines used in mills and pumping stations, where compact design and energy efficiency were important.
Let’s contrast it with the other options:
- Receiver type compound engine (a): Uses a separate receiver between cylinders to store steam temporarily.
- Tandem type compound engine (b): Similar to Woolf but may use a receiver and doesn’t necessarily share a common piston rod.
- None of these (d): Incorrect, as the Woolf type fits the description.
Hence, the correct choice is (c) Woolf type compound engine.