Applied Thermodynamics

Q.1-  For an ideal air-standard gas turbine cycle, the minimum and maximum temperatures are 300 K and 1000 K respectively. The optimum pressure ratio of the cycle is ______. (round off to 2 decimal places)

Ans. (8.22) [8.15 to 8.35]

Sol. Optimum pressure ratio,
For air, γ = 1.4

Q.2 – Which of the following figure correctly shows pressure variation in centrifugal
compressors:

Ans. (D)
Sol-

Q.3- What is the efficiency of an ideal regenerative Rankine cycle power plant using saturated
steam at 327°C and pressure 135 bar at the inlet to the turbine, and condensing
temperature of 27°C (corresponding saturation pressure of 3.6 kPa)?

(A) 92% (B) 33% (C) 50% (D) 42%

Ans. (C)

Sol. Ideal regenerative Rankine cycle efficiency is same as the Carnot cycle efficiency.

Q.4 – The ideal cycle for a steam power plant is the Rankine cycle instead of the Carnot cycle because

(A) Rankine cycle has higher efficiency
(B) Rankine cycle efficiency equals the Carnot cycle efficiency
(C) Rankine cycle has higher work ratio and is easier to implement
(D) Carnot cycle gives lower turbine work

Ans. (C)

Sol. Rankine cycle is used instead of the Carnot cycle because the Rankine cycle has higher
work ratio and is easier to implement, even though the efficiency of Carnot cycle is more
than that of Rankine cycle.

Q.5- Which of the following statement(s) is/are correct for Reaction turbine?

(A) Pressure drop takes place in both the moving blade as well as fixed blade
(B) Profile type symmetrical blades are used
(C) Cross-section area between the blade passage is made converging both for fixed and
moving blades
(D) These turbines are mainly used for high power generation with heavy investment.

Ans. (A, C, D)

Sol. Aerofoil type unsymmetrical blades are used.