This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Draught System”.
1. Which of these terms defines the pressure difference in the furnace?
Explanation: The term ‘draught’ is used to define the static pressure in the furnace, in the various ducts and the stack.
2. The draught or pressure difference for a chimney of height of H metres is given by
Explanation: The draught produced is given by Δp=gH(ρa-ρg).
3. Which of these is not a type of mechanical draft system for a furnace?
a) balanced draft
b) induced draft
c) forced draft
d) actuated draft
Explanation: The three types of mechanical drafts are balanced, induced and forced drafts.
4. Stack heat losses can be minimised by
a) using low c.v. fuels
b) controlling the excess air
c) oxygen enrichment of combustion air
d) maintaining proper draft in the furnace
Explanation: Excess amount of air leads to significant losses in energy due to heat loss through flue gases.
5. Which of these accentuates clinkering trouble on furnace grate burning coal?
a) low reactivity of carbonised residue containing high proportions of iron and sulphur
b) low forced draught and low fuel bed temperature
c) thick fire bed and preheated primary air
d) all of the mentioned
Explanation: All these reasons lead to clinkering.
6. Natural draught produced by a chimney depends upon
a) density of chimney gases
b) height of chimney
c) both ‘a’ and ‘b’
d) none of the mentioned
Explanation: Natural draught depends on density of gases in chimney and its height.
7. In a furnace employing forced draught compared to induced draught
a) the fan operates hot and hence blades are liable to corrosion and erosion
b) positive pressure exists in the furnace
c) air is sucked in, so air leaks are more and hence furnace efficiency is reduced
d) none of the mentioned
Explanation: A positive pressure exists in the furnace employing forced draught.
8.Which of the following types of the fans has the highest cost?
a) centrifugal fans
b) axial fans
c) primary fans
d) gas recirculation fans
Explanation: Axial fans have the highest cost.
9. Which of these is not a type of drive of variable speed control?
a) variable speed turbine
b) hydraulic coupling
c) multiple speed ac motor
d) electronically adjustable turbine drive
Explanation: Except ‘d’, all other are a type of drive in variable speed control.
Sanfoundry Global Education & Learning Series – Power Plant Engineering.
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