Category: Mechanical Engineering

Latest multiple choice questions with answers for mechanical engineering students.

Mechanical Engineering MCQs [Quiz 31]

Q1. Tertiary air is the air used to
(a) provide air around burners for obtaining optimum combustion
(b) transport and dry the coal
(c) cool the scanners
(d) supply air for ignitors
(e) convert CO (formed in lower zone of furnace) into C02 at higher zone.

Q2. The safety valve on boiler drum compared to safety valve on superheater is set at
(a) same value
(b) higher value
(c) lower value
(d) lower/higher depending on steam flow
(e) unpredicatble.

Q3. Which is not correct statement about pulverised fuel firing
(a) high burning rate is possible
(b) heat release can be easily controlled
(c) fuel burns economically
(d) it is the best technique for burning high ash content fuel having low fusion ash
(e) separate mills are required to powder the coal.

Q4. The three “Ts” for good combustion are
(a) temperature, time, and turbulance
(b) total air, true fuel, and turbulance
(c) thorough mixing, total air, and temperature
(d) total air, time, and temperature
(e) none of the above.

Q5. Which is not correct statement about the function of furnace
(a) to provide proper conditions for con-tinuous complete combustion
(b) mix fuel with air and ignite
(c) separate ash from coal
(d) maintain heat supply to prepare and ignite the incoming fuel
(e) to minimise radiation losses.

Q6. Which is not correct statement about effect of sulphur in fuel
(a) it has heating value
(b) it helps in electrostatic precipitation of ash in flue-gases
(c) it leads to corrosion of air heaters, ducting, etc. if flue gas exit temperature is low
(d) it erodes furnace walls
(e) none of the above.

Q7. Heating value of fuel used is as on fired basis. If it is reported for dry or moisture free fuel, then latter should be multiplied by the following factor to correct for as fired value
(a) (1- moisture content)
(b) (1 + moisture content)
(c) 1 + moisture content
(d) 1 – moisture content

Q8. Gardually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of
(a) higher effectiveness of boiler
(b) high calorific value coal being burnt
(c) fouling of heat transfer surfaces
(d) raising of steam temperature
(e) leakage of air.

Q9. Incomplete combustion can be best judged by
(a) smoky chimney exit
(b) excess air in flue gases
(c) measuring carbon mono-oxide in flue gases
(d) measuring temperature of flue gases at exit of furnace
(e) measuring oxygen in flue gases.

Q10. The capacity of induced draft fan compared to forced draft fan in a boiler is
(a) same
(b) more
(c) less
(d) less or more depending on size of boiler
(e) unpredictable

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