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 super­-imposing 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.

Edge flame propagation via parallel electric fields in nonpremixed coflow jets

“…A study of premixed and nonpremixed jet flames under various direct current (DC) and alternating current (AC) conditions recently visualized the three-dimensional nature of ionic wind [3]. Note that Weinberg and colleagues knew the nature of ionic wind [1], however, the visual impact of drastically tilted flame toward a cathode [10] somewhat misled researchers to have a false impression that ionic wind blows from an anode to a cathodeunidirectional.…”

“…The separation of these charged species imposes electrical charges on the flow volume, ending neutrality in the flame zone such that the electric body force on the flow volume creates a bulk flow motion, i.e., ionic wind, blowing from the flame toward both electrodes [1][2][3].…”

Effect of an axial electric field on detonation waves

“…It is known flames conduct electricity due to the presence of free electrons and ions in the combustion zone. Several studies (e.g Lawton and Mayo [15]) showed that when an 4 electric field is applied to a flame, the flame is pulled in the direction of positive ion flow towards the negative electrode. This effect is referred to as the ionic wind induced by the presence of an electric field.…”

“…Six photo diodes were spaced regularly along the tube to monitor the detonation velocity 15 as it traversed the field section. Three PCB 113A24 pressure transducers were mounted flush with the tube wall at the locations indicated in Figure 2-1.…”

A Study of the Effects of Electric Fields on Solid Propellant Burning Rates

“…Electrode GeuinuLiy V. Th1is configurationprvdsteheS opportunity of all geometries used for ionic winds, if exis,:ant, to influence the burning process (19,20,26 This geometry served no further use.…”