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

大型超声速窗洞通常用于超临界冲压发动机的研究。然而，如果考虑到运行成本、安全性和设施规模，就不能在大学等小型实验室中使用大窗隧道。因此，我们开发了小尺度的窗洞，并尝试在亚毫秒内测量两个矩形钢管窗洞的流速、马赫数、密度和温度以及非定常流压力。为了了解上述变量，我们测量了静态压力，得到了3.39 μ m红外线He-Ne激光的阴影照片和光吸收，并测量了冷模型中气体中播种的小颗粒的速度，其中室温空气和高压段的氮气通过喉部膨胀到低压段。隧道的一个喉道为38毫米宽，10毫米高，另一个喉道为20 × 5毫米^2。利用这些通道，我们可以得到马赫数4 ~ 4.5，温度30 ~ 50k，0.5 ~ 2kpa。由于我们确认了温度、速度和马赫数与静压计算的结果一致，因此我们采用静压测量进行热模型实验，其中富氧混合物的燃烧气体在高压段膨胀到低压段。热模型实验在直径100 mm、长6米、排土场150 l的钢管中进行。在低压段，我们可以得到与设计相同的马赫数，这取决于预混丙烷氧混合物的条件。膨胀条件下的温度分别为700k、820 K和1200 K。在该通道中，液体燃料（正戊烷）喷入拉瓦尔喷嘴约10毫秒。利用气体辐射和静压时程，在距喷管约2 m处观察到自燃现象。通过这些实验，我们可以证实在马赫数为4-5的超声速流动中喷雾点火和燃烧。少

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