Numerical Simulation Study Of Fluidized Bed Based Powder Feeder For Laser Cladding

Powder feeding is a key part of laser cladding, and powder transported with carrying gas is a current popular method in laser cladding process. so It’s very important to develop a powder feeding system with carrying gas which have homogeneous feeding rate and easy to realize the automatic control. Three-dimensional unsteady numerical simulation of gas-solid two phases flow in powder feeder based on fluidized bed was presented. The simulation results were compared with those of the experiments. And the numerical simulation was also used to optimizing structure and gas path design of powder feeder. Finally, the convey property of feeding different kinds of powders is simulated and analyzed.The simulation results of Ni-based alloy powder feeding process in Syamlal-O’Brien, Gidaspow, Mckeen and modified Syamlal-O’Brien drag law model are compared, which show that the mass flow rate obtained from Mckeen drag model is consistent well with the experimental results. And the simulation results of different fluidizing gas flow rate also agree well with the experimental results, which indicates that Mckeen model is suitable to simulate this kind of powder feeder.The internal gas and powder phases flow field of the powder feeder are analyzed, the results show that the upper fluidizing gas inlet didn’t directly act on powder fluidizing and feeding. The same powder feeding results were obtained by the gas flow of the bottom fluidizing gas inlet, and upper fluidizing gas inlet is closed or just open. Less gas was needed to powder feeding. The height of powder feeding tube is optimized, simulation results show that a more homogeneous mass flow rate are obtained when the distance from the powder feeding tube to the bottom fluidizing gas inlet is 14mm. else the mass flow rate of powder has poor stability.By an application of the modified numerical model, the simulation result of powder feeding with different particle diameter was presented. The mass flow rate of powder decreased with the increase of particle diameter. Large particle size is harder to feeding under given gas flow rate, and the mass flow rate of small particle size is also limited by the structure of powder feeder. So the mass flow rate would not linear increased but tended to a definite value. And the simulation result of different powder material density with a same particle diameter is also presented. With the increase of powder density, the mass flow rate of powder first increased and then decreased. And then by analysis the flow of powder phase, obtains that the fluidizing based powder feeder would has a better feeding result with the lower density powder.