Numerical Simulation On Fiber Collection Efficiency With Variable Coefficient Of Restitution

With the speeding up of the industrialization and the increase of energy demand, the emission problem of fine particulate matter has been received more and more attention. Bag type dust collector is the most widely used equipment of dust collector. By using fiber-filtering technology, it can efficiently filter the micro-sized particles in airflow. But as the increasing of the fine particulate matter emission regulation, improving the existing fiber technology has become the top priority.In this paper, based on the mechanism of particle collision, considering the effect of variable restitution coefficient to the particle deposition and fiber capture coefficient, a particle deposition model and a deposited particle tree structure is established. Then the process of the particle deposited on the single/multi fiber structure is simulated to make references to the design and improvement of the bag type dust filter.First, from the aspects of the particle size and the filtration velocity, the effects on the particle deposition and collection efficiency are discussed. The result shows that in the aspect of particle deposition, when the filtering speed is relatively small, particle will evenly deposit around the fiber. With the increase of the filtering speed, particle deposition area gradually focuses on fiber windward side. When the filtering exceeding the critical capture speed, particles collision with the center of the fiber windward begins to rebound, and the deposited particles on this area started to decrease. When the filtering speed is constant, with the increasing particle diameter, the effect of the inertia becomes lager. Particle deposition area goes to the two flanks of the windward side, and the stack height as well as the layer number of the deposited particle rise rapidly. On the aspects of the collection efficiency, when the filtering speed makes the St number equal to 1, it has the lowest efficiency; when the filtering speed makes the St number greater than 1 and less than the critical capture speed, with the increasing of the filtering speed, it increases quickly; when the filtering speed is bigger than the critical capture speed, due to the particles start to rebound, collection efficiency curve begins to reduce.Then, the processes of the particle deposited on the multifiber are simulated. The results show that the collection efficiency of the multifiber is affected by fiber array structure and solid volume fraction. At parallel arrangement of fibrous structure condition, due to the obscuring effect of the front fibers, particles deposite mainly on the first row of fibers; but under the condition of the staggered arrangement of fibrous structure, deposits mainly concentrate on the front two rows of fibers, which has a higher level of collection efficiency. On the aspect of collection efficiency, parallel arrangement's collection efficiency is far less than the staggered arrangement's. Under the condition of staggered arrangement, the second row of fibers have the biggest collection efficiency; the collection efficiency increases with the solid volume fraction, and the collection efficiency of the third row of fibers rises at first then decreases eventually.