Reg. No.
B.E. B.Tech. DEGREE EXAMINATION, MAY 2017
Elective
Mechanical Engineering
14UME902 GAS DYNAMICS AND JET PROPULSION
(Regulation 2014)
Duration: Three hours Maximum: 100 Marks
Answer ALL Questions
PART A (10 x 1 10 Marks)
1. In regions, fluid velocity is equal to the sound velocity.
Incompressible flow Subsonic flow
Sonic flow Hypersonic flow 2. The flow in which the fluid characteristics do not change with respect to time
continuous flow one dimensional flow two dimensional flow steady flow
3. For an isothermal flow in long constant area duct, remains constant.
Static temperature Viscosity Friction factor All the above 4. The value of mach number of air at the maximum point of Rayleigh flow is
0.5 0.25 0.75 1
5. The stagnation pressure across normal shock may
increase decrease remains constant increase or decrease
6. Shock can be develop in a flow.
supersonic subsonic sonic none of these
Question Paper Code: 41781
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7. Pick up the wrong statement: Pulse-jet requires no ambient air for propulsion Ramjet engine has no turbine Turbine drives compressor in a Turbojet Bypass turbojet engine increases the thrust without adversely affecting, the propulsive efficiency and fuel economy 8. In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of
Vacuum Atmospheric air Compressed air Oxygen alone
9. The thrust per unit weight flow rate of the propellant for a rocket engine is known as its Specific impulse Specific propellant consumption Weight flow co-efficient Thrust co-efficient
10. Theoretically the maximum achievable speed by a body in space is equal to
1,97,600 km/s 2,97,600 km/s 330 m/s 330 km/s
PART B x 2 10 Marks)
11. Differentiate nozzle and diffuser.
12. Give two practical examples where the Fanno flow occurs.
13. Define oblique shock.
14. List the different types of jet engines.
15. State the advantages of liquid propellant rockets over solid propellant rockets.
PART C x 16 80 Marks)
16. Discuss on Von Karman's rules of supersonic flow.
A supersonic fighter plane flies at an altitude of 3000 m. An observer on the ground hears the sonic boom 7.5 seconds after the passing of the plane over his head. Estimate speed of plane in km/hr and Mach number. Assume the average temperature of air as 11oC.
Or
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A conical diffuser has entry diameter 20 cm. The Mach number, temperature and pressure are 0.6, 120 kN/m2 and 340 K. The Mach number at exist is 0.2. For one dimensional isentropic flow, calculate: Pressure, temp and velocity at exist Mass flow rate, and exit diameter, and Change in impulse function.
17. A circular duct passes 8.25 kg/s of air at an exit Mach number of 0.5. The entry pressure and temperature are 345 kPa and 380C respectively and the co-efficient of friction is 0.005. If the Mach number at entry is 0.15, determine: The diameter of the duct Length of the duct Pressure and temperature at exit, and Stagnation pressure loss.
Or
A gas =1.3 and R 0.46 kJ/kg at a pressure of 70 kPa and temperature of 295 K enters a combustion chamber at a velocity of 75 m/s. The heat supplied in a combustion chamber is 1250 kJ/kg. Determine, the Mach number, pressure and temperature of gas at exit.
18. An Aircraft flies at a Mach number of 1.1 at an altitude of 15,000 meters. The compression in its engine is partially achieved by a normal shock wave standing at the entry of the diffuser. Determine the following for downstream of the shock: Mach number Temperature of the air Pressure of the air Stagnation pressure loss across the shock.
Or
Air having a Mach number 3.0, approaches a symmetrical wedge having a wedge angle of 30oC. The pressure and temperature of the air are 1 bar and 27oC. Find the Mach number and velocity of flow downstream of the shock wave, assuming that a weak oblique shock is formed. Also, find the pressure, density, temperature and stagnation pressure downstream of the shock wave.
19. Illustrate the working of ramjet engine and depict the various thermodynamic processes occurring in it on h-s diagram. Write down its main advantages and disadvantages.
Or
Describe the main components of a gas turbine engine used for turbojet aircrafts with the aid of a simple layout. Show the various processes occurring in the engine on T-s diagram.
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20. Draw neat sketches explaining the general working of the following rocket engines: Hybrid propellant rockets, and Nuclear rockets.
Mention any five important properties desired of a liquid propellant.
Or
Describe with the aid of neat sketches the two arrangements of solid propellant grains employed for restricted and unrestricted burning.
List out any three important applications of rocket propulsion.