Question

In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the steam lap and the angle of the eccentric but keeping constant the travel and lead of the valve. This method will

(a) cause withdrawing or throttling of steam

(b) reduce length of effective stroke of piston

(c) reduce maximum opening opening of port to steam

(d) all of the mentioned

The question was asked by my college professor while I was bunking the class.

Enquiry is from Reversing Gears in section Steam Engine Valves and Reversing Gears of Machine Dynamics

Answer 1

Correct choice is (c) reduce maximum opening opening of port to steam

To elaborate: In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the steam lap and the angle of the eccentric but keeping constant the travel and lead of the valve. This method will reduce maximum opening opening of port to steam.

In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve is by increasing the angle of advance of the eccentric while the throw of the eccentric, steam lap and exhaust lap are kept constant. The method will reduce length of effective stroke of piston.

In a steam engine, one method of obtaining the earlier cut-off with a simple slide valve may be obtained by increasing the angle of advance of the eccentric but reducing the throw of the eccentric and keeping the steam lap and exhaust lap constant. The method will cause withdrawing or throttling of steam.