Velocity, Pressure and Temperature Measurement in Low-Pressure Supersonic Flow

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The large scale supersonic window tunnels are usually applied for the study of SCRAM jet engine. However, one cannot use the large window tunnel in a small laboratory, such as in a university, if one consider the running cost, the safety and the scale of facility. Therefore, we developed the small scale window tunnel and tried to measure the flow velocity, the Mach unmber, the density and temperature, as well as the pressure of unsteady flow within submilliseconds in two steel rectangular tube window tunnels. To know the above-mentioned variables we measured the static pressures, obtained the shadow photographs and the light absorption of infrared He-Ne laser at 3.39 mum, and measured the velocity of the small particles seeded in the gas in the cold model, where the room temperature air and nitrogen in the high pressure section are expanded through the throat into the low pressure section.The one throat of tunnel is 38 mm wide and 10 mm high and the other is 20 x 5 mm^2. Using these wi … More ndow tunnels we could obtain the Mach number 4-4.5, the temperature 30-50 K,0.5-2kPa.Since we confirmed that the temperature, the velosity, and the Mach number agreed with those calculated from the static pressure, we used the static pressure measurement for the experiment of hot model, where the burned gas of wxygen rich mixture in the high pressure section expanded into the low pressure section. The hot model experimet was performed in a 6 meter long steel tube of 100 mm diameter with 150 liter dump tand. In the low pressure section we could obtain the same Mach numbers as designed, which depended on the premixed propane-oxygen mixture conditions. The temperatures in the expandedcondition were 700,820, and 1200 K.In this tunnel the liquid fuel (n-pentane) was sprayd into the laval nozzle for about 10 ms. The self ignition was observed at about 2 m from the nozzle using the time histories of gas radiation and static pressure.Through these experiments we could confirme the spray ignition and combustion in supersonic flow of Mach number 4-5. Less