Previous Years Gate MCQ’s on Power Engineering 2011-2013

Solved GATE Questions’s on Power Engineering

Statement for linked answer question: 1 and 2

The temperature and pressure of air in a large reservoir are 400 K and 3 bar respectively. A converging- diverging nozzle of exit 0.005 is fitted to the wall of reservoir shown in figure. The static pressure of air at the exit section for isentropic flow through the nozzle is 50 kPa. The characteristic gas constant and the ratio of specific heats of air are 0.287 kJ/kg K and 1.4 respectively.

Question 1. The density of air in at the nozzle exit is

(A) 0.560

(B) 0.600

(D) 0.800

GATE-ME-2011

Hint 1. (Ans C)

Question 2. The mass flow rate of air through the nozzle in kg/s is

(A) 1.30

(B) 1.77

(D) 2.06

GATE-ME-2011

Hint 2.(Ans D)

Velocity at exit,

Mass flow rate ,

Question 3. The values of enthalpy of stem at the inlet and outlet of a steam turbine in a Rankine cycle are 2800 kJ/kg and 1800 kJ/kg respectively. Neglecting pump work, the specific steam consumption in kg/KW-hour is

(A) 3.60

(B) 0.36

(D) 0.01

GATE-ME-2011

Hint 3. (Ans. A)

Specific steam consumption in kg/kw-hr

Question 4. A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as 990 . The isentropic specific work done by the pump in kJ/kg is

(A) 0.10

(B) 0.30

(D) 2.93

GATE-ME-2011

Hint 4. (Ans D)

Work done=

Question 5. A ideal Brayton cycle, operating between the pressure limits 1 bar and 6 bar, has minimum and maximum temperatures of 300k and 1500 K. the ratio of specific heats of the working fluid is 1.4. The approximate final temperatures in Kelvin at the end of the compression and expansion process respectively

(A) 500 and 900

(B) 900 and 500

(D) 900 and 900

GATE-ME-2011

Hint 5. (Ans A)

Statement for linked answer question 6 and 7

In a simple Brayton cycle, the pressure ratio is 8 and temperature at the entrance of compressor and turbine are 300 K and 1400 K, respectively. Both compressor and gas turbine isentropic efficiencies equal to 0.8 for the gas, assume a constant value of (specific heat at constant pressure) equal to 1 kJ/kg K and the ratio of specific heat as 1.4.