蒸汽动能磨粉碎腔内颗粒加速特性的数值模拟

Numerical simulation of particles acceleration characteristics in fluidized bed superheated steam jet mill

为研究颗粒经超音速喷嘴加速后在蒸汽动能磨粉碎腔内的加速情况,采用Fluent软件模拟蒸汽动能磨内的过热蒸汽流场和颗粒加速特性,获得不同物料在多种粒径和密度条件下的颗粒加速特性。结果表明:由于受喷嘴出口气流与环境压力匹配的影响,导致加速区域激波与膨胀波交替出现,使得过热蒸汽气流速度上下波动,最大波动幅度约为5%;在相同的过热蒸汽加速流场中,4种不同粒径的颗粒加速过程相似,粒径越小,颗粒的加速性能越好,其中直径为5μm的物料被加速达到的最大速度是直径为45μm的2倍左右,并且颗粒的加速性能与颗粒的密度呈反比关系。

In order to analyzed the acceleration characteristic of particle accelerated via supersonic nozzle in fluidized bed superheated steam jet mill, Fluent software was used to simulate the steam flow field of gas and particles and the particle acceleration features under the condition of different particle size and density were obtained. The results show that due to the influence of nozzle exits a airflow pressure matching with the environment, leading to shock and expansion wave in accelerating regional appear alternately which made the superheated steam flow velocity fluctuates up and down, the biggest swings around 5%. In the same acceleration of superheated steam flow field, the accelerate process of four different particles size is similar. The smaller of the particles size, the better of the acceleration performance and in the speed of the material having a diameter of 5 μm diameter is about 2 times 45 μm. Besides, particle acceleration is inversely proportional with the density of particles.