Generation and Study of Microwave Plasma Jets

摘要

The present report summarizes the work, under the support of the AFOSR Grant AFOSR-FA9550-O4-l-0352, starting at May 1, 2004. This research program is primarily aiming at developing plasma torches as igniters of a scramjet engine. For the hydrocarbon-fueled scramjet in a typical startup scenario, cold liquid JP-7 is injected into a Mach-2 air crossflow (having a static temperature of - 500 K); under these conditions, the fuel-air mixture will not auto-ignite. Some ignition aid, for example, plasma torches that can deliver enough heat to the mixture to reduce the ignition delay time and to increase the rate of combustion, is necessary to initiate main-duct combustion. A cylindrical torch module improved from the previous one (United States Patent No.: US 6329628 BI) has been designed. It was fabricated at AFRL, Hanscom and tested at Polytechnic University. The central electrode is made of a tungsten tube, rather than a tungsten rod, adding an additional flow path through the tungsten tube that can be used for fuel injection purpose The gas plenum chamber is integrated to the module. Moreover, we have developed a unique way to couple microwave to the arc plasma generated by this new torch module. We integrate the torch module into a tapered rectangular cavity.