Solved GATE Questions on Power Engineering
Data for Question 1 and 2 is given below. Solve the problem and choose correct answers.
Consider a steam power plant using a reheat cycle as shown. Steam leaves the boiler and enters the turbine at 4 Mpa, 350 
(
) after expansion in the turbine to 400 KPa (
), the stem is reheated at 350
(
), and then expanded in a low pressure turbine to 10 KPa (
).
Question 1. The thermal efficiency of the plant neglecting pump work is
(A) 15.8 %
(B) 41.1%
(C) 48.5%
(D) 58.6%
GATE-ME-2004
Hint 1. (Ans B)
Gi ven :
Turbine work
Question 2. The enthalpy at the pump discharge (
) is
(A) 0.33 KJ/Kg
(B) 3.33 KJ/Kg
(C) 4.0 KJ/Kg
(D) 33.3 KJ/Kg
GATE-ME-2004
Hint 2. (Ans D)
Enthalpy at the pump discharge will be greater than 29.3 KJ/Kg
Hence from given choice clearly we can say
Question 3. The compression ratio of gas power plant cycle corresponding to maximum work output for the given temperature limits of 
will be
(A) 
(B) 
(C) 
(D) 
GATE-ME-2004
Hint 3. (Ans A)
Let
For maximum work output
We know that
Question 4. In the velocity diagram shown below, u=blade velocity, C=absolute fluid velocity and w=relative velocity of the fluid and the subscripts 1 and 2 refers to inlet and outlet. This diagram is for
(A) An impulse turbine
(B) A centrifugal compressor
(C) A reaction turbine
(D) An axial flow compressor
GATE-ME-2005
Hint 4. (Ans B)
As 
Velocity of flow is constant throughout the stage and the diagram is symmetrical hence it is diagram of reaction turbine.
Question 5. A p-v diagram has been obtained from a test on a reciprocating compressor. Which of the following represents that diagram?
(A) 
(B) 
(C) 
(D) 
GATE-ME-2005
Hint 5. (Ans D)
At the time of intake, intake valve operates only when the pressure inside the cylinder is lower than the atmospheric pressure. And appreciable large pressure difference at the time of suction starting, causing fluttering at initial.
A the time of compression, process followed is polytropic and continues till pressure exceeds the delivery line pressure for opening the delivery valve.
Question 6. Determine the correctness or otherwise of the following Assertion 
and the Reason 
Assertion 
:Condenser is an essential equipment in a steam power plant
Reason 
: For the same mass flow rate and the same pressure rise, a water pump requires substantially less power than a steam compressor
(A) Both 
and 
are true and 
is correct reason for 
.
(B) Both 
and 
are true and 
is NOT the correct reason for 
.
(C) Both 
and 
are false
(D) 
is false and 
is true
GATE-ME-2006
Hint 6. (Ans B)
Condenser is an essential equipment in a steam turbine because it is not economical to feed steam directly to the boiler.
For same mass flow rate and the same pressure rise, a water pump require very less power because the specific volume of liquid is very less as compare to specific volume of vapour.
Question 7. Determine the correctness or otherwise of the following Assertion
and the Reason 
Assertion 
: In a power plant working on a Rankine cycle, the regenerative feed water heating improves the efficiency of the steam turbine.
Reason 
: The regenerative feed water heating raises the average temperature of heat addition in the Rankine cycle.
(A) Both 
and 
are true and 
is correct reason for 
.
(B) Both 
and 
are true and 
is NOT the correct reason for 
.
(C) Both 
and 
are false
(D) 
is false and 
is true
GATE-ME-2006
Hint 7. (Ans A)
Answer Keys
1. (B) 2. (D) 3. (A) 4. (B) 5. (D) 6. (B) 7. (A)
One Response to “Previous Year GATE MCQ’s on Power Engineering 2004-2006”
Pratik Patil
Ans 7 is incorrect,efficiency of steam turbine is function of turbine geometry,steam dynamics,dryness fraction etc not dependent on feed water heating.