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Flow Field Test and Intensity of Turbulence Analysis in Circumfluent Cyclone Separator

Author: ZhaoFuBao
Tutor: WangWeiWen
School: Qingdao University of Science and Technology
Course: Chemical Engineering
Keywords: circumfluent cyclone separator PIV flow field FLUENT Reynolds stress model
CLC: TQ051.89
Type: Master's thesis
Year: 2008
Downloads: 145
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Abstract

In this thesis, the flow fields and the vortex characteristics of circumfluent cyclone separator (CFC) were studied by means of PIV experiment and FLUENT numerical simulation. It provided the theory gist to restrain the vortex in cyclone and the optimization of rectifier. The main works in this thesis as follows:Utilizing an advanced measurement technique—particle image velocimetry (PIV), the instantaneous two-dimensional velocity distributions at some sections of the CFC were obtained. Some turbulent characteristics, such as intensity of turbulence of flow field, were also computed from the instantaneous velocities measurement by PIV. Utilizing the pre-preparation software of FLUENT—GAMBIT, the physical model in the simulation was established. According to the configuration characteristics and the fluid flow of CFC, the hexahedral excellent grids were generated which could satisfy the computation demands of FLUENT. Utilizing Reynolds stress model (RSM) of FLUENT—one of the computational fluid dynamics (CFD), the gas flow field in CFC was simulated.The PIV experiment results showed that: The distributions of the tangential velocity were perfectly axis-symmetrical in the separating fields, presenting in M shape and when r/R was about 0.35, we got the max velocity. And when r/R was from 0.2 to 0.3, we could get the max velocity of tangential in the cone. Tangential velocity at the upper section was bigger (8m/s) than other sections in the cirque (2.5m/s~4.5m/s). The distributions of the axial velocity were basically axis-symmetrical in the inner and the cirque of the CFC, and the max axial velocity (llm/s) was appeared in the vicinity of axes, it decreased with the accretion of the radius. In the areas next to the wall of the CFC, the axial velocity was negative firstly, then it increased slightly. The intensity of turbulence was presented in inverse U shape, and the distributions were perfectly axis-symmetrical at the different sections of the CFC. The intensity of turbulence was steadily changed, and seldom changed with the axial height.The simulation results revealed that the distributions of total pressure and static pressure were similar, both presenting in V shape and they were relatively axis-symmetrical in the separating spaces. The total pressure and static pressure appeared at the central vortex were low, and the lowest point of static pressure appeared at center of the underside of vent-pipe in CFC. The special fluid path design of the circumfluent cyclone separator shortened the moving distance of the fluid, avoided the disturbance between the inner and outer flow, and eliminated the secondary vortex and short circuit flow existing in conventional cyclones. But the liquid moved acutely between inner piece and the cone, the flow field were very confusion and a little portrait vortices lied in CFC. These eddies would directly effect the performances of CFC.Compared the forecasted velocity obtained from RSM model to the PIV experimental result, they were basically coincident. It showed that RSM model could exactly predict the strong revolves in CFC.

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