Types of Wind tunnels

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 11/7/2018 1 DEPARTMENT OF MECHANICAL ENGINEERING

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. 11/7/2018 2 DEPARTMENT OF MECHANICAL ENGINEERING

3. Fig: Wind tunnel testing environment 11/7/2018 3 DEPARTMENT OF MECHANICAL ENGINEERING

4. TYPES OF WIND TUNNELS Blow Down Wind Tunnel Atmospheric Entry Wind Tunnel High Enthalpy Wind Tunnel 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 11/7/2018 4 DEPARTMENT OF MECHANICAL ENGINEERING

5. 1. Blow Down Wind Tunnel 11/7/2018 5 DEPARTMENT OF MECHANICAL ENGINEERING

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. 11/7/2018 6 DEPARTMENT OF MECHANICAL ENGINEERING

7. 2. Atmospheric Entry Wind Tunnel 11/7/2018 7 DEPARTMENT OF MECHANICAL ENGINEERING

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. 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 8

9. 3. High Enthalpy Wind Tunnel 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 9

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. 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 10

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 . 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 11

12. Open Circuit Wind Tunnel for Subsonic Testing 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 12

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. 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 13

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 . 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 14

15. B. Open Circuit wind Tunnel for Supersonic Testing 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 15

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. 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 16

17. C. Closed Circuit Wind Tunnel 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 17

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. 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 18

19. THANK YOU 11/7/2018 DEPARTMENT OF MECHANICAL ENGINEERING 19