Microplasma jet cleaning of Langmuir probes for methane-air premixed flame diagnostics

This paper presents the use of an atmospheric microplasma jet to preserve the measurement integrity of Langmuir probes for ion density measurements of an atmospheric methane-air premixed flame. Soot produced from incomplete combustion is able to deposit on the probe filaments and alter measurement characteristics over time. The effect of argon microplasma probe cleaning on current measurements was investigated, with probe flame exposure of 2–30 s and 20 s of microplasma cleaning. In the noncleaned probes, a decrease in the current measurements (up to 64% reduction) was observed in subsequent tests of probes at all exposure times. The probe cleaning experiments yielded a near constant current reading, even after subsequent flame exposures. The resulting plasma densities showed similar trends.