B.E./B.Tech. DEGREE EXAMINATION.
ME 151 — MECHANICAL ENGINEERING
(Common to Electronics and Instrumentation Engineering and Instrumentation and Control Engineering)
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 ´ 2 = 20 marks)
- What do you understand by thermodynamic reversibility?
- Define thermal efficiency and brake power as applied to engines.
- How a firetube boiler is different from a water tube boiler?
- Mention the purpose of governing steam engine.
- What are the two classifications of steam turbine? Give examples.
- Define the terms impulse and reaction.
- Explain briefly the process of metal casting.
- Mention the purpose of flux in brazing metals.
- Distinguish between live centre and dead centre of a lathe.
- List down any 4 typical applications of a shaping machine.
PART B — (5 ´ 16 = 80 marks)
- In a test of an oil engine under full load condition the following results were obtained :
Indicated power = 33 kW
Brake power = 27 kW
Fuel used = 8 kg/h
Rate of flow of water through gas calorimeter = 12 kg/min
Cooling water flow rate = 7 kg/min
Calorific value of fuel = 43 MJ/kg
Inlet temperature of cooling water = 15°C
Outlet temperature of cooling water = 75°C
Inlet temperature of water to exhaust gas calorimeter = 15°C
Outlet temperature of water to exhaust gas calorimeter = 55°C
Final temperature of the exhaust gases = 80°C
Room temperature = 17°C
Air–fuel ratio on mass basis = 20
Mean specific heat of exhaust gas = 1 kJ/kgK
Specific heat of water = 4.18 kJ/kgK
Draw up a heat balance sheet and estimate the thermal and mechanical
- (a) Draw the carnot cycle on p–v and T–s diagrams. Derive an expression for its efficiency. Comment on the significance of this result as it related to source and sink temperature. (16)
(b) (i) Mention the function of water gauge, fusible plug, safety valve, economiser, superheater and air preheater. (6)
(ii) Describe the construction of Babcock and Wilcox boiler. (10)
- (a) Explain with a neat sketch the construction and principle of operation of a steam engine. (16)
(b) (i) Discuss the differences between impulse and reaction turbines. (6)
(ii) Explain the working principle of a single stage impulse turbine with a neat sketch showing the pressure and velocity diagram. (10)
- (a) (i) Explain the different types of casting. (12)
(ii) Mention the uses of castings. (4)
(b) (i) List down the various tools that are used in moulding. (10)
(ii) Distinguish between soldering and brazing. (6)
- (a) (i) Explain the principle of operation of a lathe with a neat sketch. (8)
(ii) With a neat sketch explain the construction of a shaper. (8)
(b) (i) Discuss the principle of operation of a milling machine with a neat sketch. (8)
(ii) Explain the construction of a drilling machine with a neat sketch. (8)