Papers by Keyword: Tangential Velocity

Abstract: This paper is presents numerical simulation of isothermal swirling turbulent flows in a combustion chamber of an unconfined burner. Isothermal flows of with three different swirl numbers, S_N of axial swirler are considered to demonstrate the effect of flow axial velocity and tangential velocity to define the center recirculation zone. The swirler is used in the burner that significantly influences the flow pattern inside the combustion chamber. The inlet velocity, U₀ is 30 m/s entering into the burner through the axial swirler that represents a high Reynolds number, R_e to evaluate the differences of S_N. The significance of center recirculation zone investigation affected by differences R_e also has been carried out in order to define a good mixing of air and fuel. A numerical study of non-reacting flow into the burner region is performed using ANSYS Fluent. The Reynolds–Averaged Navier–Stokes (RANS) realizable k-ε turbulence approach method was applied with the eddy dissipation model. An attention is focused in the flow field behind the axial swirler downstream that determined by transverse flow field at different radial distance. The results of axial and tangential velocity were normalized with the U₀. The velocity profiles’ behaviour are obviously changes after existing the swirler up to x/D = 0.3 plane. However, their flow patterns are similar for all S_N after x/D = 0.3 plane towards the outlet of a burner.

Abstract: Large eddy simulation to describe the turbulent flow of airflow field was used to calculate the unsteady turbulent flow characteristics in the cyclone. It funded that the tangential velocity in the cyclone profile behaved like rankine vortex, with the downward semi-free vortex of the outer layer and the upward forced vortex. With the increasing import gas velocity, the swirling strength of the center increased which reduced collection efficiency by clouding the dust particles in the ash bucket to the center airflow.

Abstract: The impact processes of water and ethanol drops on a rotating horizontal aluminum disk were recorded and analyzed using a high-speed digital camera together with an image analysis program. The angular velocities of the disk were altered to study the effect of surface tension of drops on drop impact processes. The experimental results show that a lower surface tension will result in a higher tangential spread factor and a lower receding rate during the receding stage, for the drop impinging and depositing on a rotating disk. In addition, a lower surface tension of the drop tends to promote the occurrence of splash. The experimental results further verify a proposed correlation of splash-deposition boundary for drops impinging on a rotating disk. Both drops, though they have a quite different surface tension, experience four stages, with two new stages different from those of drops impinging on stationary surfaces. Their tangential spreading factors both increase obviously with the tangential velocity at the impact point, while their radial spreading factors vary a little.

Abstract: This paper presents computational fluid dynamics (CFD) studies to characterize air velocity distribution for various bed configurations in a swirling fluidized bed (SFB). Unlike conventional fluidized beds, a SFB provides radial mixing which is desirable is fluidization. Three velocities components were observed, the tangential velocity, radial velocity and axial velocity. These velocities were created as a result of using annular blade type distributor which mimics the turbine blades. In actual industrial applications, the axial velocity will create fluidization while the tangential velocity provides swirling effect. The presence of radial velocity can be explained as a consequence of centrifugal force generated by the swirling gas. Understanding these velocity distributions will enable optimization of the annular blade distributor design towards a high efficient fluidized bed system.

Abstract: A fundamental study has been performed to analysis the fluid dynamic characteristics of the gas medium in a rotating disk cavity through the commercial software CFX11.0. This paper aims to discuss the impact of the speed of rotating disk, axial and radial size and parietal lubricant film velocity and other factors on the gas flow state in cavity. Several conclusions have been obtained: the speed of rotating disk has a great impact on velocity distribution of gas flow field; the dimensionless tangential velocity of the gas medium decreases along the radial direction, and with the speed increasing, it shows a certain regularity; Dimensionless radial velocity decreases along the radial direction, and the speed of rotating disk nearly has no influence on this; The shear stress distribution along the radial direction and the distribution of tangential velocity have similar regularity; the impact of disk cavity height on the distribution of the tangential velocity along radial direction in the gas flow field is much more obvious than the impact of disk cavity width.

Abstract: Circulating Fluidization Bed (CFB) for Flue Gas Desulfurization (FGD) is widely used. But its desulfurization efficiency is lower than Wet FGD. Its investment is not much lower than Wet FGD. Flow field of CFB for FGD is hard to be uniform. Swirl Composite Fluidization Mode (SCFM) was brought forward compared to Venturi Fluidization Mode (VFM). Experiment and simulation under cold condition was proceeded. From the test, flow field along axis and in cross-sections for SCFM are uniform. Turbulent velocity fluctuation is violent. And particles concentration is high. SCFM has better flow effect than VFM. Uniformity increases with higher superficial velocity and more tangential swirl devices. Recommended tangential swirl devices number is between 3-6. SCFM technology has good foreground.