On the NOx Generation in Corona, Streamer and Low Pressure Electrical Discharges

Abstract

A theory developed by scientists to study nitrogen oxides, NO x , production by solar proton events shows that the NO production rate is approximately equal to the rate of production of ion pairs during the proton impact. Since the bulk of ionization in such events is produced by secondary electron impacts, the same concept is used here to study the NO x production in low pressure discharges, corona discharges and streamer discharges in which the source of ionization is the electron impacts. Using experimental data pertinent to corona discharges it is established that, as in the case of proton impacts, the rate of NO x production is approximately equal to the rate of production of ion pairs. The theory in turn is applied to study the NO x production in streamer and low pressure electrical discharges. The results show that the NO production in low pressure discharges depends not only on the energy dissipated but also on the ambient pressure and the electric field. In low pressure discharges the efficiency of NO x production is given by kα (p, E) / eE NO molecules/J, where α (p, E) is the Townsend’s first ionization coefficient, p is the atmospheric pressure, e is the electronic charge, E is the electric field and k is the number of NO molecules resulting during an ionizing event. This shows that the NO x production efficiency of a discharge depends not only on the energy dissipation but also on the pressure and the electric field. In the case of streamer discharges, the NO x molecules produced by the streamer in propagating a unit distance is given by k / 2ωeE , where ω is the number of positive ions located in the streamer head.