Corona discharge augmentation of the catalytic combustion of hydrogen in the diffusion controlled regime

Abstract

An experimental study of the catalytic combustion of hydrogen in air at 1 atm has been conducted for laminar and turbulent flows in an annular reactor. The reactor comprises a small-diameter inner cylinder and an outer cylinder of platinized alumina. Measurements of the overall rate of combustion have been made wherein the inner cylinder is maintained at a positive d.c. potential with respect to the outer cylinder such that a steady corona discharge takes place. For nearly fully developed flows for Reynolds numbers from 300 to 6500 and corona discharge currents up to 1.1 mA, the reaction rate increases with corona current. Augmented reaction rates are correlated in terms of the ratio of electrical body forces due to corona discharge and the momentum forces of the mean flow. The reaction order is found to be unity with respect to the concentration, both with and without corona discharge present. Overall first-order rate constants are much lower than true rate constants, indicating a dominance of mass transfer. Rate constants are found to increase markedly with corona current but cannot be correlated in the same way as heat transfer coefficients. The fractional increase in overall reaction rate at constant corona current, is found to increase rapidly for low Reynolds numbers, but after reaching a peak, decreases rapidly. This decrease occurs across the laminar-to-turbulent flow transition.