Applied Thermodynamics - II, Question Paper of Mechanical Engineering 4th Semester, Download Question Paper Applied Thermodynamics 7

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Total No. of Questions : 09]

B. Tech. (Sem. – 4th)

APPLIED THERMODYNAMICS - II

SUBJECT CODE : ME – 208 (2008 Batch)

 Paper ID : [A0811]

Time : 03 Hours

INSTRUCTION TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying

TWO marks each.

2. SECTION-B contains FIVE questions carrying FIVE marks each and

students has to attempt any FOUR questions.

3. SECTION-C contains THREE questions carrying TEN marks each and

students has to attempt any TWO questions.

SECTION-A

l. Answer briefly :

a. What is engine indicator? What function does it perform in IC engine?

b. What is octane number?

c. What is specific fuel consumption? How do we evaluate it?

d. Why do we do supercharging in IC engines?

e. Write the expression for pressure rise in case of axial flow compressor.

f. Define for compressors isothermal, isentropic and polytropic efficiency.

g. What are the advantages of closed cycle gas turbine over the open

cycle gas turbine?

h. What is the use of pre-whirl in case of compressors?

i. What are various fuels used for in rocket motors? What are the

desirables from them?

j. What is the difference between ram jet engine and the pulse jet

engine?

SECTION-B

2. Explain the phenomenon of knocking in CI engine. What are different

factors those influence knocking? Describe the methods to suppress it.

3. What is the criterion for selection of blade materials in case of gas

turbines? What are different blade materials? Also, discuss the turbine

blade cooling requirements.

4. Draw the valve-timing diagrams for four stroke petrol engine and four

stroke diesel engine and discuss the various cut off points.

5. Derive the expression for pressure rise per stage for axial flow compressor

clearing showing the velocity triangles ant inlet and outlet. Also represent

the compression process on the T-s diagram.

6. Derive expressions for thrust power, propulsion energy, propulsion and

thermal efficiencies for a propulsive system.

SECTION-C

7. A centrifugal compressor is desired to have a total pressure ratio of

3.5:1. The inlet eye of the compressor impeller is 30 cm in diameter. The

axial velocity at the inlet is 130 m/s, and the mass flow is 10 kg/s. the

velocity in the delivery duct is 115 m/s. the tip speed of the impeller is

450 m/s and runs at 16,000 rpm with the total isentropic efficiency of

78% and pressure coefficient of 0.72. The ambient conditions are

1.013 bar and 15°C. Calculate :

a) the static pressure ratio.

b) the static pressure and temperature at the inlet of compressor.

c) work of compressor per kg of air.

d) the theoretical power required.

8. In a gas turbine installation, air is taken in LP compressor at 288 K and

1.1 bar and after compression, it passed through intercooler where its

temperature is reduced to 295 K. The cooled air is further compressed in

IP unit and passed in the combustion chamber where its temperature is

increased to 950°C by burning the fuel. The combustion products expand

in HP turbine which runs the compressor and further expansions is continued

in LP turbine which runs the alternator. The gases coming out from

LP turbine are used for heating the incoming air from IP compressor and

then exhausted to atmosphere. Taking the following data determine the

power output, specific fuel consumption and thermal efficiency. Pressure

ratio of each compressor = 2, isentropic efficiency of each compressor

stage = 85%, isentropic efficiency of each turbine stage = 85%, effectiveness

of heat exchanger = 0.75, air flow = 15 kg/s, CV of fuel = 45 MJ/kg.

Cp (air) = 1 kJ/kgK, Cp (gas) = 1.15 kJ/kg K,  (air) = 1.4,

 (gas) = 1.33. Neglect the mechanical pressure, pressure and heat

losses of the system and fuel mass ratio.

9. Following data were observed from the trial of oil engine. BHP of the

engine = 73.55 kW, oil consumption = 16.5 kg/hr, oil fuel contains

84% C and 16% H2, CV of the oil = 45.2 MJ/kg. The cooling water

after passing through the cooling jacket is further passed through the

exhaust gas calorimeter. Cooling water flow rate = 1220 kg/hr, temperature

of the water entering the-cooling jacket = 18°C, temperature of the water

leaving the jacket = 57°C, temperature of the water leaving the exhaust

gas calorimeter = 82°C, temperature of the exhaust gases leaving the

calorimeter = 100°C, temperature of the exhaust gases leaving the

engine = 410°C. Engine room temperature = 18°C. Specific heat of

exhaust gases = 1.0035 kJ/kg K. Find the excess air supplied to the

engine. Also draw heat balance sheet on minute and % basis.