steam-boilers-and-engines mechanical-engineering question and answers -Page 3

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Home Aptitude

3. When the speed of the crankshaft is between 100 r.p.m. and 250 r.p.m., the engine said to be a
Options
A. slow speed engine
B. medium speed steam engine
C. high speed steam engine
D. none of these

4. The function of a safety valve is
Options
A. to blow off steam when the pressure of steam inside the boiler exceeds the working pressure
B. to indicate the water level inside the boiler to an observer
C. to measure pressure of steam inside the steam boiler
D. none of the above

5. Which of the following statement is wrong?
Options
A. The factor of evaporation for all boilers is always greater than unity.
B. The amount of water evaporated in kg per kg of fuel burnt is called equivalent evaporation from and at 100� C.
C. The ratio of heat actually used in producing the steam to the heat liberated in the furnace is called boiler efficiency.
D. none of the above

6. Which of the following statement is correct for a compound steam engine?
Options
A. The cost of the engine, for the same power and economy, is more than that of a simple steam engine.
B. The forces in the working parts are increased as the forces are distributed over more parts.
C. The ratio of expansion is reduced, thus reducing the length of stroke.
D. The temperature range per cylinder is increased, with corresponding increase in condensation.

7. In a boiler, feed water supplied per hour is 205 kg while coal fired per hour is 23 kg. The net enthalpy rise per kg of water is 145 kJ. If the calorific valve of the coal is 2050 kJ/kg, then the boiler efficiency will be
Options
A. 56%
B. 63%
C. 74%
D. 78%

8. In water tube boilers
Options
A. water passes through the tubes which are surrounded by flames and hot gases
B. the flames and hot gases pass through the tubes which are surrounded by water
C. forced circulation takes place
D. none of these

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