Studying the Radio Frequency Energy Coupling to Atmospheric Plasma Jet for the Plasma-Assisted Combustion and Other Applications

Abstract

Column-like dynamically created plasma structures and their interaction with RF signals are studied for various scientific and industrial applications, including discharge driven plasma jet sources. In such devices a microwave energy propagates along the jet as a surface wave, which is accompanied by radiative losses. The similar phenomenon is used in a so-called “plasma antenna” devices based on discharge tubes. Besides that, plasma jets are studied for Plasma-Assisted Combustion in scramjet engines. For the same purpose a sub-critical and other RF discharges were suggested. The excited species and radicals influence the results for both types of techniques. However, the joint action of both RF energy supply and plasma jets on combustion in scramjets was not evaluated yet. A phenomenon of RF discharge propagation far from the feeding point along the combustion zone was already described, while the spatial distribution of electromagnetic energy and its influence on combustion efficiency are still unclear. Development of RF plasma torch for the Plasma-Assisted Combustion is reasonable in the case of high coupling efficiency, which depends on resonance phenomena and, thus, on geometrical parameters of the non-mixed part of the plasma jet in the flow. The signal reflection may damage RF power source, while the radiation losses may be of uncertain effect. This problem was studied experimentally using the physical model. The energy coupling and impedance mismatch were evaluated for various plasma column dimensions. The results are discussed.