Experimental investigations of characteristics of electro-thermal-chemical plasma

An experimental investigation of transient plasmapropellant interactions is underway at Penn State with the overall objective of gaining insights from parametric studies that will contribute to the formulation of a more complete understanding of the various chemical and physical processes that occur during propellant ignition by the plasma igniter. Testing has been performed in open air and closed chambers with the plasma jet impinging on an inert plate or on propellant samples. Available diagnostics include high-speed photography, pressure measurements, and species measurements using a microprobe mass spectrometer system. The parametric studies to be discussed in this paper include the variation of separation between the plasma generator exit and the test sample, variation of the plasma energy, and variation of the capillary bore size. For open-air testing, pressure distributions along an inert impingement plate, discharge current, ablation of capillary as well as high-speed images were obtained as distance, energy, and capillary size were varied. Another series of tests, conducted in a closed chamber, were performed to obtain chemical species from the plasma efflux with different ambient gases. Descriptions of the upgrading of an existing microprobe mass spectrometer to a molecular beam mass spectrometer and development of a new advanced heat flux gage are also presented.