In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-...In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-era(100 captures per sec) with dual converging sonic nozzles. The flow field is also visualized by means of highspeed schlieren system( up to 70000 frame per second) to clarify the unsteady behavior of the jet structures suchas barrel shock wave, and Mach disk. Experiments were performed with a blow down tunnel changing the parameterssuch as the nozzle to plate distance, the distance between the two nozzles, and wind tunnel pressure ratio.The nozzle to plate distance L and the distance between the two nozzles H are non-dimensionalized by the nozzlediameter D covering H/D=1.5, 2.0, and 3, L/D= 2, 3,and 4, and po/pb=1.0 - 5.0, where po and pb are stagnationpressure and back pressure respectively. Although the response of the infrared camera is quite different fromthat of the high speed camera, the unsteady correlation between the pressure and temperature fields is confirmedunder some conditions. Also the high speed schlieren pictures and the wall static pressure fluctuations suggestthat the generation of the Mach disk promote the unsteady behavior of the jets. After the confirmation of the correlation,a simple way to find the severe fluctuating region can be provided according to the two dimensional unsteadytemperature images without a lot of unsteady pressure measurements.展开更多
文摘In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-era(100 captures per sec) with dual converging sonic nozzles. The flow field is also visualized by means of highspeed schlieren system( up to 70000 frame per second) to clarify the unsteady behavior of the jet structures suchas barrel shock wave, and Mach disk. Experiments were performed with a blow down tunnel changing the parameterssuch as the nozzle to plate distance, the distance between the two nozzles, and wind tunnel pressure ratio.The nozzle to plate distance L and the distance between the two nozzles H are non-dimensionalized by the nozzlediameter D covering H/D=1.5, 2.0, and 3, L/D= 2, 3,and 4, and po/pb=1.0 - 5.0, where po and pb are stagnationpressure and back pressure respectively. Although the response of the infrared camera is quite different fromthat of the high speed camera, the unsteady correlation between the pressure and temperature fields is confirmedunder some conditions. Also the high speed schlieren pictures and the wall static pressure fluctuations suggestthat the generation of the Mach disk promote the unsteady behavior of the jets. After the confirmation of the correlation,a simple way to find the severe fluctuating region can be provided according to the two dimensional unsteadytemperature images without a lot of unsteady pressure measurements.
