Experimental assessment of ozone production by multichannel plasma discharges for automotive applications

Abstract

Ozone addition has come under study as a means of controlling ignition timing in low temperature combustion using highly dilute homogeneous mixture. In this context, this work aims to improve ozone production from air and simulated exhaust gas recirculation (EGR) in a homogeneous charge compression ignition engine using a cold plasma reactor based on multichannel dielectric barrier discharges. Ozone concentration was investigated as a function of energy deposition, gas characteristics, and distance from the source to measurement points. At a given specific input energy, experimental outcomes indicate a relatively high influence of the feeding EGR composition (O2–N2–CO2–CH4–H2O) and flow rate on the ozone production. However, no changes within experimental accuracy in ozone concentration were seen when changing the distance plasma-measurement points, allowing us to find the optimum position of the plasma reactor with respect to the engine inlet. In air, ozone concentration increased from 120 ppm to 1600 ppm, as the flow rate decreased from 200 to 2 slm. At a given voltage set point, the increase in gas pressure causes the decrease in energy deposition and thus the ozone concentration. In EGR mixtures, the lowest ozone concentration tends to stabilize around 50 ppm, which is acceptable for LTC applications.