# Download GTU B.Tech 2020 Summer 8th Sem 2171914 Gas Dynamics Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 8th Sem 2171914 Gas Dynamics Previous Question Paper

Seat No.: ________
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER? VIII EXAMINATION ? SUMMER 2020
Subject Code: 2171914 Date:26/10/2020
Subject Name: GAS DYNAMICS
Time: 10:30 AM TO 01:00 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 Gas Table is permitted.

MARKS
Q.1 (a) Define following :
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1) Maximum fluid velocity
2) Critical velocity of sound
3) Hypersonic flow

(b) "Bulk moduluas of elasticity of ideal gas is directly
04
proportional to the pressure of the ideal gas in
reversible adiabatic process" prove the above
statement.

(c) Define M*. Derive following relation:
07
2
{
}M2
pr
oportiona
2 = +1
-1
l to
1-{
}M2
+1
Calculate maximum value of M* for diatomic gas.

Q.2 (a) Compare adiabatic expansion and isentropic
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expansion processes on TS diagram.

(b) Air flowing in a duct has a velocity of 300m/s,
04
pressure 1 bar and temperature 290K. Determine
stagnation temperature and velocity of sound
corresponds to stagnation condition.

(c) From the continuity equation, derive the equation for
07
non-dimensional mass flow rate in terms of pressure
ratio of static and stagnation pressure.
m T
R
Non-dimensional mass flow rate =
0
A* P
0

OR

(c) From the continuity equation derive the relation :
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( 1
/ 2( -1))
1 2
A p
M 1
*
A p0
-1 2
1
M
2
Q.3 (a) What is shock strength?.Write the equation which
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represents shock strength in terms of upstream Mach
number.

(b) Upstream gas properties are Mach number 2.5,
04
Pressure 2 bar and temperature 275K.
1

What is Mach number, pressure and velocity of gas in
downstream side of shock.

(c) Starting from energy equation prove that,
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Mx* * M*y = 1.
Where upstream and downstream reference Mach
numbers for normal shock are represented by Mx* and
M*y respectively.

OR

Q.3 (a) What is shock? Represent normal shock on hs
03
diagram along with Rayleigh and Fanno curve.

(b) A gas at a Mach number of 1.8, pressure 0.8 bar and
04
temperature 373 K encounter shock. Determine
density after shock and compare it with isentropic
density.

(c) From the energy equation, derive the following
07
relation for the normal shock
2/( 1)
2
M
2
x
M
y
2 /( 1) 2
M 1
x
Where upstream and downstream reference Mach
numbers for normal shock are represented by Mx* and
M*y respectively.
Q.4 (a) What is Fanno flow? Give examples of Fanno flow in
03
thermal systems.

(b) Prove that at maximum entropy point on Fanno curve
04
is where Mach number is unity and all processes
approach this point.

(c) A circular duct passes 8.25 kg/s of air at an exit Mach
07
number of 0.5. The entry condition of air is 3.45 bar
and 380C. Co-efficient of friction of duct is 0.005. If
entry Mach number is 0.15 determine:
1) Length of duct
2) Diameter of duct
3) Exit pressure and temperature of air.

OR

Q.4 (a) Differentiate : Fanno flow and Isothermal flow.
03

(b) Write governing describing Fanno curve. Draw three
04
different Fanno curve on TS diagram for three
different mass densities.

(c) Air enters a long circular at 3 bar, 312 K and Mach
07
number 0.5. If the flow is isothermal throughout the
duct Calculate:
1) Length of the duct require to get Mach number 0.7
at exit.
2) Pressure and temperature at exit where M = 0.7.
3) Limiting Mach number.
Take : Duct diameter 0.125m and friction factor
0.0045.
Q.5 (a) What is critical state? Calculate the ratio of stagnation
03
pressure to the critical pressure for monoatomic gas.

(b) State the four assumptions of Rayleigh flow as well as
04
write two applications where Rayleigh flow analysis is
applicable.
2

(c) The Mach number at the exit of combustion chamber
07
is 0.9. The ratio of stagnation temperature at exit and
entry is 3.74. if the exit condition is 2.5 bar at 1273K,
determine :
1) Pressure, temperature and Mach number at
entry.
2) Heat supplied per kg of the gas.
Take : = 1.3 and Cp = 1.218 kJ/kg-K

OR
Q.5 (a) Write the equation of A/A* and draw the graph of
03
(A/A* ) M.
(b) Write momentum equation for Rayleigh flow. Plot
04
dp
Rayleigh curve on pv diagram and find :
for
dv R
Rayleigh line.
(c) The conditions of a gas in a combuster at entry are :
07
0.343 bar, 310 K and 60 m/s. If the stagnation enthalpy
is increased by 1172.5 kJ/kg between entry to exit,
Calculate
1) Pressure at exit.
2)Temperature at exit and
3) Mach number at exit.

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