Research On The Impact Of The Velocity Inlet Boundary Condition To The Bubbling Fluidized Bed

Bubbling fluidized bed is one kind of fluidized instruments which is widely used in industries. The axial gas flow causes gas-solid two-phase flow with regularity. In industrial practice, the gas flow at the air distribution is always pulsatile, which may influence gas-solid two-phase flow. With the rapid development of hardware and calculation technique, numerical simulation has become an important method to study flow patterns.Euler-Euler two-fluid model is used in this paper, and standard k-εtwo gas-processing model of turbulent flow is applied. Steady velocity inlet boundary condition and pulse distribution velocity inlet boundary conditions with normal distribution pulse item and SIN distribution plus item are introduced to simulate the process of two-phase flow patterns in center jet bubbling fluidized bed, uniform bubbling fluidized bed and wall-to-bed bubbling fluidized bed separately.The fact that every bubble in fluidized bed goes through the stages of formation, growing-up and separation from air-distribution can be concluded from the simulation result. The bubble bottom shrink when it separate from air-distributor, and trailing vortex form in the bubbling movement process. Interaction existed among bubbles, and the coalescence can only take place in the vertical direction.The simulation result shows that it is more reasonable to forecast and analyze the hydrodynamic behavior with the turbulence of the inlet boundary condition. Contrast with the steady velocity inlet boundary condition result, the distribution of the physical quantities which describes the gas and solid phase is smoother in the radial direction. Smaller bubble frequency and fluctuation take place when turbulence inlet boundary condition is applied.