An experimental investigation of an arc-heated stirred reactor

Abstract

A small stirred reactor equipped with electrodes was developed, in which high-temperature radicals produced by an arc discharge are dispersed through a reacting mixture. With the electrode arrangement finally selected, the stability of the arc discharge was satisfactory up to the maximum loading used without seeding (no interruption and negligible fluctuation of the current). The result obtained using a lean propane-air mixture (=0.62) showed that quite small additions of electrical power (boost ratio: 4.5∼6%) produce large increases in throughput (200% or more), keeping combustion efficiency relatively high. It was shown also that a diluted mixture (=0.43) outside the flammability region can be reacted steadily with small additions of electrical power (e.g., 10%) with reasonable throughput and combustion efficiency (e.g., N/VP 1.8 =4 and combustion efficiency ≈80%). Under the assumption of an adiabatic, perfectly-stirred reactor, burning-rate correlations based on reaction rate theory were derived, using the data for air loading and reacting gas temperature or oxygen consumption efficiency. Although the accuracy of the results is limited because of imperfect mixing and relatively large heat loss, it was confirmed that with electrical power, the value of the apparent activation energy is very low, whereas without electrical power a normal value is obtained. This fact seems to suggest that high-temperature radicals, produced by arc discharges, participate actively in the rate-limiting process of the combustion reaction.