Electrical control of gas flows in combustion processes

Abstract

The theory of the ionic wind is developed for flame ions travelling towards electrodes of various configurations so that entrainment as well as main stream gas velocities can be predicted. It is shown that, by confining entrainment to specified regions, large flow velocities can be induced at the flame itself, where they can be used to modify a variety of combustion processes. Theoretical maximum values of the flow parameters are calculated for several configurations likely to be of practical use and these are compared with results of experiment. The experiments are designed to test the general theory and to determine to what extent the theoretically deduced maxima are altered by inevitable practical complications such as entrainment of hot gas, deposition of soot and other specks on the electrodes and convergence of lines of force on to individual strands of gauze-electrodes. The potentialities of varying parameters such as geometry, temperature, pressure and composition as well as superimposing magnetic fields are also examined. A variety of practical examples is considered in the light of this theory. Experiments confirm that confined entrainment can be used to aerate diffusion flames in an accurately controllable manner without risking flash-back or requiring an air supply, metering and mixing systems. Similarly, it is demonstrated that combustion intensity can be increased by field-induced recirculation of hot products, thereby minimizing random turbulence and heat losses to the large obstacles usually employed for this purpose.