GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-VII(NEW) EXAMINATION — SUMMER 2019
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Subject Code:2171914 Date:10/05/2019Subject Name:Gas Dynamics
Time:02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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MARKS
Q.1 (a) Define Mach Number. Classify compressible flow on the basis of Mach Number. 03
(b) An aircraft is flying at an altitude of 8 km where the ambient temperature is 250 K. Find the Mach number and classify as subsonic or supersonic when the speed of the aircraft is 04
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a) 30m/sb) 300 m/s.
(c) Air flows through a duct at a pressure of 0.196 MPa with a velocity 350 m/s. The temperature of the air is 40°C. Determine the isentropic Stagnation pressure, Stagnation temperature and Stagnation density. 07
Q.2 (a) prove that ( T/T* ) = ( p/p* ) 03
(b) Draw the shape of subsonic and supersonic nozzle and diffuser and mention the varying properties. 04
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(c) Derive following expression for area ratio in terms of Mach number 07
A/A* = [2/(?+1)](?+1)/2(?-1) * (1/M) * [1 + ((?-1)/2)M2](?+1)/2(?-1)
OR
(c) Air expands isentropically from 20 bar and 100°C to 12 bar. Determine the temperature and density at the final state. Also find the ratio of initial to final acoustic velocity. 07
Q.3 (a) Write general characteristic of normal shock. 03
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(b) The pressure and Mach number upstream of a normal shock are 0.1 MPa and 2.0 respectively. Determine the Mach number and pressure downstream of the shock. 04
(c) Derive the following relation for normal shock VxVy = a*2. 07
OR
Q.3 (a) Write three governing equations which satisfy the state before and after a normal shock. 03
(b) Define strength of a shock wave. Find the strength of a shock wave when normal shock appears at M = 2. 04
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(c) Air flows through a converging-diverging nozzle followed by a constant area duct of 30 mm diameter. A normal shock occurs in the duct of constant area section with a velocity of 500 m/s. The air in the duct is stationary and is a pressure and temperature of 0.1 MPa and 200 K respectively. Determine the velocity of air after the passage of the shock. Also find the pressure, temperature, Mach number and stagnation temperature imparted upstream of the wave. 07
Normal Shock table:
M | M | Po2/Po1 | P2/P1 | T2/T1
1.46 | 0.71 | 0.941 | 2.33 | 1.29
Isentropic table:
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M | T/To | P/Po | p/ po
0.56 | 0.940 | 0.808 | 0.858
0.58 | 0.936 | 0.796 | 0.849
Q.4 (a) Differentiate Fanno flow and Isothermal flow. 03
(b) Draw Fanno line on h-s diagram and discuss the effect of friction in subsonic and supersonic flow. 04
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(c) The average friction of a 25 mm diameter 12 meter long pipe is 0.004. The condition of air at the entry are 2 bar and 300 K. Determine the mass flow rate, pressure, temperature and the mach number at exit, if the mach number at inlet is 0.25. 07
OR
Q.4 (a) Define dimensionless Critical Mach number. Give its uses. 03
(b) Explain phenomenon of chocking in Isentropic flow. 04
(c) Air flows through an insulated circular pipe at a rate of 495 kg/minute. The pressure, temperature and Mach number of air at entrance to the pipe are 0.3 MPa, 300 K and 0.15 respectively. The coefficient of friction for the pipe is assumed constant and its value is 0.005. if the Mach number at exit is 0.5, determine: 07
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a) The diameter of the pipeb) The length of the pipe.
Q.5 (a) Define fanning’s coefficient of friction and hydraulic diameter. 03
(b) Air flow in a duct with a velocity of 215 m/s. The temperature of air measured at a point along the-duct is 30°C and the air pressure is 5 bar. Determine the stagnation pressure. 04
(c) Show that the Mach number corresponds to the maximum entropy point of a Fanno curve’is unity. 07
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OR
Q.5 (a) Air enters in a pipe of 0.05 m diameter at stagnation condition of 10 bar and 400 K at Mach number of 2.8. Find the mass flow rate in pipe the pipe. 03
(b) Show graphically that zone of silence is greater than zone of action when object is moving with speed more than the velocity of sound. 04
(c) Explain the characteristics of Rayleigh flow with suitable graphs. 07
Fanno Flow Table (for air):
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M=0.14 | M=0.16 | M=0.24 | M=0.26 | M=0.50 | M=0.52 | M=0.54
4fLmax/D | 32.511 | 24.197 | 9.38 | 7.68 | 1.069 | 0.917 | 0.786
P/P* | 7.80 | 6.829 | 4.538 | 4.185 | 2.138 | 2.051 | 1.971
T/T* | 1.195 | 1.193 | 1.186 | 1.183 | 1.142 | 1.138 | 1.133
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This download link is referred from the post: GTU BE 2019 Summer Question Papers || Gujarat Technological University
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