UNSOLVED PROBLEMS
PROBLEM 1: The cross-sectional area 15cm * 30cm test section of a closed circuit wind tunnel having mach number 0.8.The pressure and the temperature of the test section is maintained at 1.02 bar and 288K respectively. The stagnation pressure loss in the precooler and the ducts upstream of the compressor is 100mbar.The efficiency of the compressor is 79 percent. The flow in the nozzle and compressor is isentropic. Calculate
- a) Mass flow rate through the tunnel
b) Compressor pressure ratio
c) Power required by the compressor
Answer: 18.8889Kg/s, 1.068, 146.35KW
PROBLEM 2: The data of Mach-2 supersonic wind tunnel is given below Pressure in the test section is 0.69 bar, area of cross-section of nozzle throat 1000cm2, ambient pressure 1.02 bar and ambient temperature is 311k.The air is taken from the atmosphere and compressed continuously in a multi stage compressor to the reservoir pressure. The text section of tunnel directly exhausts into the atmosphere. Determine: a) temperature of air in the text section b) mass flow rate of air c) Cross-sectional area of the text section
Answer: a) T01=500.7K, T=4.80c b) m=97.317kg/s c) 1687cm2
PROBLEM 3: a mixture of air and Freon is used in a closed circuit wind tunnel. The cross-sectional area of test section is 625cm2, mach number of text section is 1.6, Settling pressure and temperature are 5bar and 425 k respectively. For mixture R=135J/kgK, γ =1.3 Calculate a)cross-sectional area of nozzle and diffuser throat. b) Power required to start the tunnel