Impingement of particles-gas jet on a uniformly flowing water
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Solid particles of different diameters and wettabilities were injected into a uniformly flowing water of relatively low flowrate in order to visualize with a high-speed cinecamera the penetration of a particles-gas-liquid, three-phase flow jet. The velocity of particles injected from the nozzle was measured by a laser Doppler velocimeter, and the kinetic energy of the particlesgas jet was estimated. Two kinds of penetration depth were defined. One is the penetration depth of an "envelope" in which the particles-gas jet moves downward at a very high speed with virtually no liquid fragmentation. The particles remaining at the bottom of the cavity formed by the impinging gas jet are of primary importance for the initiation of this "envelope." The wettability of particles has less influence on this phenomenon. Another penetration depth is concerned with the trajectory of the particles-gas-liquid, three-phase flow jet. The particles-gas jet entrains the surrounding water beyond the envelope, and a three-phase flow jet is formed. Its behavior is affected considerably by the wettability of particles. It also was observed that the sectional area of the particles-gas jet was contracted slightly after impinging on the liquid surface due to the induction of a downward water flow. The penetration depths were predicted based on the kinetic energy of the impinging particles-gas jet. The effect of particle diameter on these phenomena was influenced significantly by the movement of the ensemble of particles.
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INTRODUCTION
THE industrial
application of powder injection in metallurgical processes is well established now, and a number of modeling studies u-~3~ have been reported on this technology. I~4J An early work by Engh et al. tn outlined the critical conditions for penetration of a single particle at the gas-liquid interface. Ozawa et al. t2J observed the penetration of a single particle into a mercury pool using a high-speed cinecamera. They found that the particle not only depressed the liquid surface to form a cavity but also was accompanied by a certain amount of liquid when it impinged on the liquid surface. When a particle-laden gas jet impinges on a liquid surface, a different approach is necessary for the analysis of the phenomenon. Engh et a1.[3.41 used a model similar to that proposed by Themelis et al. I51 for the trajectory of a submerged gas jet. They found that the expansion angle of a particles-gas-liquid, three-phase flow jet is considerably smaller than a gas-liquid, two-phase flow jet. In addition, several authors have formulated the penetration depth of a three-phase flow jet based on the balance between the buoyancy force and the momentum of the impinging particles-gas jet. 16.7J Kimura is1 studied the erosion of the arched bottom of the smelting furnace in the MI (Mitsubishi & IshikawaHarima Heavy Industry Co. Ltd.) process. He injected various kinds of particles into water or carbon tetrachloride to simulate the erosion phenomena, and the penetration depth of the impinging particles-gas jet was T. SH
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