Annular-Electrode Spark Discharges in Flowing Oxygen: Buckingham Pi Analysis

Tinker, Darren C ; Osborne, Robin J ; Pitz, Robert W

关键词: ELECTRODES;    ELECTRIC SPARKS;    SPARK IGNITION;    OXYGEN;    DIMENSIONAL ANALYSIS;    HIGH SPEED;    SCHLIEREN PHOTOGRAPHY;    FLOW CHARACTERISTICS;    IMAGING TECHNIQUES;    THERMAL PLASMAS;    ELECTRON PLASMA;    ACOUSTIC PROPERTIES;    REACTIVITY;    DISSOCIATION;    PLUMES;   

RP-ID  :  M18-6792

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

Limited information is available on the effects of spark discharge properties on flowing oxygen and the resultant gas plume. The fundamental addition of energy is in thermal, electronic, and acoustic modes. As sparks are employed as a synthetic activation energy, the most desirable modes of energy are electronic and thermal. The addition of energy to dissociate molecules and create highly reactive species is just as useful as raising the temperature of the gas above the mixture’s auto-ignition temperature. Due to the timescale of the event, measurements can be tricky. Dissociation of select molecules can be measured with spectroscopic methods, and validate chemical models that simulate the full chemical reaction. The thermal plume following the discharge must be tracked with a high speed system, be it imaging or fast-response instrumentation. The objective of this work is to track the thermal plume with high speed Schlieren imaging, and determine what pressure-distance product of the spark gap and manifold pressure will produce the greatest total volume of heated gases. Literature exists showing qualitative trends for the electrical discharge, yet information is not available regarding the effects on the gas mixture excited by and immediately following the arc. To fulfill this gap, the research at hand focuses on non-reactive gas mixtures flowing through annular electrode configurations. The aims are to parametrically determine what input (electrical, flow, fluid properties) and geometric (spark gap) variables create the largest spatial volume and longest duration cloud of plasma products. Studies of spark ignition have examined electrical characteristics, and imaged ignition kernels following the discharge. As often seen in application, pronged electrodes of various shapes and sizes take the spotlight of previous literature. Again driven by specific applications, such work revolves around stagnant conditions, leaving studies of sparks flowing gases in the dark. The aim of this paper is to shrink the gap of knowledge for sparks in flowing oxygen.