TED-AJ03-173 AN EXPERIMENTAL STUDY OF FLAME CONTROL BY APPLICATION OF EXTERNAL ELECTRIC FIELDS
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概要
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This paper presents results of an experimental study of the response of hydrocarbon diffusion flames to imposed DC electric fields. It is well known that due to ion formation in the flame reaction zone, flames are susceptible to electric fields. Two primary effects are recognized; these are the ionic wind effect and chemistry effect. The ionic wind effect arises because the electric field imparts a motion on the ions in the flame region driving the positive ions toward the negative electrode During their motion, these ions can impact upon the neutral molecules and radicals, thereby affecting the velocity field of the gases. The chemistry effect arises from removal of ions partaking in chemical reactions from the flame surface. In combination, these two effects can influence flame characteristics such as shape and size, as well as chemical species formation. A microgravity environment obtained by drop tower testing is utilized to conduct the described experiments in a spherical geometry and to avoid complications arising from buoyant flow effects. By removing buoyancy, a one-dimensional flame-electric field system is obtained. Theoretical considerations are presented to show that for a spherical flame the ionic wind effect is reduced and flame response should be primarily due to the chemistry effect. In the experiments, various fuels (methane, propane, and ethylene) are injected through a porous spherical burner, which also acts as one of the electrodes establishing the electric field. The burner is surrounded by a spherical Faraday cage, which serves as the second electrode. Results obtained from the experimental studies which are discussed in the paper include the effects of electric field strength and polarity, and fuel type on : (a) flame shape and size, (b) flame sooting propensity, (c) flame unsteadiness, and (d) flame extinction behavior. For example, for ethylene flames, when the outer electrode is positive, the flame radius is little affected and the flame tends to locate itself along an equipotential surface. On the other hand, for the case when the outer electrode is negative, flame radius tends to shrink and portions of the flame undergo unsteady pulsations. Interestingly, for the methane flames, local extinction is also observed.[figure]
- 一般社団法人日本機械学会の論文
著者
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Hegde U.
National Center For Microgravity Research
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Yuan Z.
National Center for Microgravity Research