Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-VIII EXAMINATION WINTER 2018
Subject Code:X81901 Date: 29/11/2018
Subject Name: Thermal Engineering
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of steam table and mollier chart is permissible.
Q.1

Explain with neat sketch the open cycle gas turbine power plant. Also show cycle on T-S diagram and derive an expression for thermal efficiency.
07

Draw the schematic diagram of a simple gas turbine cycle with inter cooling, regeneration and reheating. Draw also T-s diagram of the cycle.
07
Q.2

Discuss the various losses in steam turbine
07

Explain the various methods of attachment of blades to turbine rotor.
07
OR

Give difference between impulse turbine and reaction turbine.
07
Q.3

What is critical pressure? Derive the expression of critical pressure ratio to have maximum mass flow for a nozzle.
07

Steam at a pressure of 9 bar and 0.85 dry discharge through a nozzle having throat area of 45 mm2. If the back pressure is 1 bar, find Final velocity of the steam and Cross sectional area of nozzle at the exit for maximum discharge.
07
OR
Q.3

Explain parson's reaction turbine. Why it is called 50% reaction turbine?
07

The velocity of steam, leaving the nozzles of an impulse turbine, is 1100 m/s and the nozzle angle is 200, the blade velocity is 400 m/s and the blade velocity co-efficient is 0.75. assuming no loss due to shock at inlet, calculate for a mass flow of 0.5 kg/sec and symmetrical blading blade inlet angle driving force on the wheel axial thrust on the wheel and power developed by the turbine
07
Q.4

Explain Ram jet with T-S diagram
07

State the difference between air breathing and non-air breathing engines. Explain basic working principle of rocket engine.
07
OR
Q.4

Explain the working of turboprop engine with neat sketch. State its merits and demerits.
07

What is the principle of jet propulsion? Explain turbojet engine.
07
Q.5

Discuss the advantages of combined cycle power generation. Draw schematic diagram of combined steam and gas turbine power plant.
07

A gas turbine plant with a pressure ratio of 1:6 takes in air at 180c. The maximum temperature is 6500c and develops 2000 kw. The turbine and compressor efficiency are 0.80. Take cp=1 kj/kg k and cv=0.714 kj/kg k. Find actual overall efficiency and mass of air circulated by the turbine
07
OR
Q.5

Derive an expression for optimum intermediate pressure in an open cycle gas turbine with reheating.
07

Explain pass out turbine with schematic and T-s diagram.
07