Roll No. ......................
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.
0 comments:
Post a Comment
North India Campus