An Experimental Investigation of the Use of Supersonic Driving Jets for Ejector Pumps

The main purpose of this study was to establish pumping and thrust performance comparisons between ejector configurations utilizing sonic and supersonic parallel flow nozzles. The application of interest in this particular investigation was in boundary-layer control for turbo-jet aircraft. In order to optimize the performance, it was necessary to vary systematically the geometric parameters of mixing tube length to diameter ratio. The primary or driving jet pressure was an important independent parameter and was variable up to 32.0 times the ambient pressure. An ejector-vacuum chamber installation was fabricate and designed in order that the desired parameter ranges might be obtained. Both the ejector and thrust table were mounted inside the vacuum chamber. Results of the investigation indicated substantial improvement in the pumping and thrust performance of the ejector with supersonic primary nozzles as compared to the sonic jet. A mixing tube length of ten mixing tube diameters was found to give the most satisfactory over-all pumping performance. Comparisons between experimental results and theory for the supersonic primary nozzle are included. Experimental investigations were also conducted using a sonic primary nozzle containing a center body at primary temperatures up to 1000° F.