Quiz: Mechanical Engineering 13 April 2020

Quiz: Mechanical Engineering
Exam: UPSSSC JE
Topic: Thermal

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. The process of abstracting steam at a certain section of the turbine and subsequently using it for
heating feed water supplied to the boiler is called
(a) Reheating
(b) Regeneration
(c) Bleeding
(d) Binary vapour cycle

Q2. In an axial flow turbine, the utilization factor has an absolute maximum value of unity, for any
degree of reaction if the value of nozzle angle α is
(a) 270°
(b) 180°
(c) 90°
(d) 0°

Q3. Which of the following are essential for a good combustion chamber of turbojet engine?
1. It should allow complete combustion of fuel.
2. It should maintain sufficiently high temperatures in the zone of combustion in addition to proper atomization of fuel thus leading to continuous combustion.
3. It should not have high rate of combustion.
4. The pressure drop should be as small as possible.
(a) 1, 2 and 4 only
(b) 1, 2 and 3 only
(c) 1, 3 and 4 only
(d) 2, 3 and 4 only

Q4. Which one of the following may be considered as a single cylinder two-stroke reciprocating
engine running at 2400 rpm to 2700 rpm for rapid chain of impulses?
(a) Turbo jet
(b) Pulse jet
(c) Ram jet
(d) Athodyd jet

Q5. The higher power requirements for compression in a steam power plant working on Carnot vapour cycle
(a) Increases the plant efficiency as well as work ratio
(b) Reduces the plant efficiency as well as work ratio
(c) Does not affect the plant efficiency as well as work ratio
(d) Increases the plant efficiency and reduces work ratio

Q6. An economizer in a steam generator performs the function of preheating the
(a) Combustion air
(b) Feed water
(c) Input fuel
(d) Combustion air as well as input fuel

Q7. In Orsat apparatus, when the percentage of carbon dioxide, oxygen and carbon monoxide are
known, the remaining gas is assumed to be
(a) Hydrogen
(b) Sulphur dioxide
(c) Nitrogen
(d) Air

Q8. The partial vacuum created by the fan in the furnace and flues, draws the products of the
combustion from the main flue and allows them to pass up to the chimney. Such a draught is called
(a) Balanced draught
(b) Forced draught
(c) Induced draught
(d) Artificial draught

Q9. Which of the following are applied (used) ways of compounding steam turbines?
1. Pressure compounding
2. Temperature compounding
3. Velocity compounding
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1 and 3 only

Q10. A steam ejector which removes air and other non-condensable gases from the condenser is
known as
(a) Wet air pump
(b) Dry air pump
(c) Centrifugal pump
(d) Circulating pump

solutions

S1. Ans.(b)
Sol. Regeneration is the process of bleeding steam and using it for feed water heating.
S2. Ans.(d)
Sol.
S3. Ans.(a)
Sol. Combustor should not have high rate of combustion, else the flame may die out.
S4. Ans(b)
Sol. Pulse jet engines have stable operation in range of 45 cycles per second. This can be correlated to a 2-stroke engine running at 2400 – 2700 rpm (40 – 45 cycles/sec).
S5. Ans(d)
Sol. For Carnot cycle, the efficiency will be increased as a consequence of cycle undergoing ideal. Work ratio will be reduced due to high compressor work.
S6. Ans(b)
S7. Ans(c)
S8. Ans(c)
S9. Ans(d)
Sol. Compounding are of two types
(1) velocity compounding and
(2) Pressure compounding.
S10. Ans(a)
Sol. Wet air pump is the steam ejector pump which removes air and non-condensable gases from condenser.

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