Ions in the oxyfuel cutting flame due to work piece carbon

Experiments demonstrate that carbon in the work piece is a major source for secondary ions in the oxyfuel cutting flame. New sensing techniques replace traditional active sensors by monitoring the ion currents caused by the primary ions that are the natural byproducts of combustion, but secondary ions generated chemically at the work surface have been found to complicate the resulting signals. In the present work, ion currents through the oxyfuel flame are monitored while controlling for the addition of carbon in the outer flame. Wires of different carbon content are burned while holding all other conditions constant, and fluidized graphite dust is injected into the flame at controlled flow rates. Both experiments demonstrate that the addition of carbon in the outer cone dramatically enhances ion currents, but carbon in the material being burned is about twenty times more effective at producing ion currents.