Compressible fluid flow portion

1. WIND TUNNEL AND ITS TYPES
GUIDED BY, PRESENTED BY,
MR.RATHEESH R GROUP NO:9
ASSO.PROFESSOR ME A, S7
DEPARTMENT OF MECHANICAL ENGINEERING ROLL NO:45-49
SBCE, PATTOOR
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2. INTRODUCTION
 WIND TUNNEL
 Wind tunnel is a laboratory facility for producing high
velocity flow that can be used for simulating different flow
Mach number situations for testing of turbine blades, aerofoil
sections, and for simulating flight conditions of jet engines
,missiles ,etc.
 Wind tunnel can be subsonic, transonic or supersonic,
depending on the flow Mach no: in the test section.
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3. Fig: Wind tunnel testing environment
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4. TYPES OF WIND TUNNELS
1. Blow Down Wind Tunnel
2. Atmospheric Entry Wind Tunnel
3. High Enthalpy Wind Tunnel
4. Continuous Flow Wind Tunnel
a. Open Circuit Wind Tunnel for Subsonic Testing
b. Open Circuit Wind Tunnel for Supersonic Testing
c. Closed Circuit Wind Tunnel
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5. 1. Blow Down Wind Tunnel
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6.  High pressure air (or gas ) stored in large reservoirs are used for
supplying fluid to the test section through a convergent –
divergent nozzle .
 A quick opening valve between the reservoir and nozzle allows
flow of high pressure air (or gas) through the nozzle and test
section. In this type testing time depends on the capacity of
reservoir.
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7. 2.Atmospheric Entry Wind Tunnel
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8.  Atmospheric air enters the test section through a convergent-
divergent nozzle.
 The low back pressure required for flow expansion in nozzle is
created by discharging the air directly into an evacuated tank.
 The testing time in this type of wind tunnel can be increased by
continuously operating vacuum pump fitted to the tank.
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9. 3.High Enthalpy Wind Tunnel
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10.  In a high enthalpy wind tunnel, a shock tube is employed for
generating a high pressure, high enthalpy fluid for expansion in
the nozzle to get the required conditions in the test section.
 A shock tube is a duct in which Mach number flow is generated
by passing a shock wave through it.
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11. 4.Continuous Flow Wind Tunnel
 Continuous floe wind tunnels are employed when test is to be
conducted for longer duration . The limiting factor for continuous
flow wind tunnel is the power available for running the
compressor , since for larger sections several hundred MW of
power is required.
 Continuous flow wind tunnel can be open type or closed type. In
open type wind tunnel the atmospheric air is taken in and
exhausted to the atmosphere.
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12. A. Open Circuit Wind Tunnel for Subsonic
Testing
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13.  In such tunnel air is supplied to the system with the help of a fan,
blower or compressor.
 The air from compressor or fan passes through a diffuser to
reduce the velocity and increase the pressure and then is settled in
a large chamber called settling chamber and enters the converging
nozzle with minimum disturbance.
 The nozzle feeds the test section air With sufficient Mach number
for testing.
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14.  Fig: shows a suction type wind tunnel in which an exhaust fan is
employed for sucking the atmospheric air. Due to the sucking action air
enters the test section through a convergent nozzle increasing the velocity.
From the test section the air passes through a diffuser to get sufficient
pressure at the upstream of fan.
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15. B. Open Circuit wind Tunnel for Supersonic
Testing
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16.  It is similar to blow down type except that the reservoir is
continuously supplied with the high pressure air using a
compressor. From the reservoir, the convergent-divergent nozzle
feeds air at supersonic Mach number to the test section
 The shortcoming of this type of wind tunnel is that a continuous
amount of energy is thrown away into the atmosphere, thus
requiring a high pressure ratio and power of compressor.
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17. C. Closed Circuit Wind Tunnel
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18.  This type of wind tunnel overcome some of the problem
mentioned in open circuit systems.
 The arrangement of the tunnel consist of a compressor, a
convergent-divergent nozzle, test section, diffuser and a cooler.
 On account of closed circuit any gas besides air can be used.
 The K.E at the exit of the test section is discovered by a
supersonic diffuser.
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19. THANK YOU
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