Figure Q4 schematically illustrates the structure of a 1-m-long cylindrical wind tunnel. The test chamber of...

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Figure Q4 schematically illustrates the structure of a 1-m-long cylindrical wind tunnel. The test chamber of the wind tunnel has a uniform dimeter of 25 cm, and it operates at a Mach number of 1.8. Atmospheric air (pressure 1.0x105 Pa and temperature 20°C) enters the wind tunnel through a convergent-divergent nozzle where it is accelerated to supersonic velocities. Air leaves the test chamber through a convergent-divergent diffuser where it is decelerated to a very low velocity (well below Mach 1) before entering the fan chamber. Assume the air flow in the entire wind tunnel is a one-dimensional isentropic compressible flow problem. For air, the specific heat ratio can be taken as 1.4 and the gas constant as 287 J/kg/K (a) Calculate the air temperature T₁ and air pressure p₁ at the station in the test chamber, where Ma1=1.8. [8] (b) Calculate the cross-sectional area of the throat of the convergent-divergent nozzle. [7] (c) Explain why it is often necessary to dehumidify the air (i.e. reduce the water content in the air) before air enters the wind tunnel. [2] (d) Determine the flow Mach number at the throat of the convergent-divergent (C-D) diffuser. [3] Po To to the atmo # Ma 1.8 (1) D = 25 cm = Convergent-Divergent (C-D) Nozzle Uniform Diameter Test Chamber (D = 25 cm) Figure Q4 C-D Diffuser Fan Chamber Figure Q4 schematically illustrates the structure of a 1-m-long cylindrical wind tunnel. The test chamber of the wind tunnel has a uniform dimeter of 25 cm, and it operates at a Mach number of 1.8. Atmospheric air (pressure 1.0x105 Pa and temperature 20°C) enters the wind tunnel through a convergent-divergent nozzle where it is accelerated to supersonic velocities. Air leaves the test chamber through a convergent-divergent diffuser where it is decelerated to a very low velocity (well below Mach 1) before entering the fan chamber. Assume the air flow in the entire wind tunnel is a one-dimensional isentropic compressible flow problem. For air, the specific heat ratio can be taken as 1.4 and the gas constant as 287 J/kg/K (a) Calculate the air temperature T₁ and air pressure p₁ at the station in the test chamber, where Ma1=1.8. [8] (b) Calculate the cross-sectional area of the throat of the convergent-divergent nozzle. [7] (c) Explain why it is often necessary to dehumidify the air (i.e. reduce the water content in the air) before air enters the wind tunnel. [2] (d) Determine the flow Mach number at the throat of the convergent-divergent (C-D) diffuser. [3] Po To to the atmo # Ma 1.8 (1) D = 25 cm = Convergent-Divergent (C-D) Nozzle Uniform Diameter Test Chamber (D = 25 cm) Figure Q4 C-D Diffuser Fan Chamber

Answer rating: 100% (QA)

Solution a The temperature and pressure of the air in the test chamber can be calculated using the isentropic compressible flow equation PV constant w... View the full answer