| Cyclone separators have been one of the oldest and most popularly used industrial particulate control devices for the removal of dispersed particles from their carrying fluids because of their simplicity, easiness and low costs in terms of construction, operation, maintenance and energy consumption. With the use of suitable materials and methods of construction, cyclone separators can be operated under extreme operating conditions, especially at temperatures over 900℃, conditions that almost exclude the application of other separation technologies. Some of the best examples are cyclone separators employed in PFBC (Pressurized Fluidized Bed Combustion), IGCC (Integrated Gasification and Combined Cycle) and FCC (Fluidized Catalytic Cracking) processes. In these harsh environments, cyclone separators are nowadays the sole, fully commercial solution to the removal of particles from elevated-temperature gases. Their main disadvantage, however, is low efficiency for particles less than 5 microns in size.In order to increase the separation efficiencies of the cyclone, a little improving to its structure is maded in this thesis . Meanwhile,numerical simulations are used to analyze the three-dimensional and two-phase turbulent flow field of the cyclones while their inlet section angles respectively are 0°,30°and 45°.And also, experiments and mathematical models are used to make a further study to the gas-solid separation characteristics of these cyclones. Under the RSTM in Fluent code, although the first-order upwind scheme discretization can yield better convergence, it generally will lead to less accurate results. Therefore, the QUICK discretization scheme is used in calculating momentum, turbulence kinetic energy, its dissipation rate equations and Reynolds stress equations. And the discrete phase models are used in the simulations when the numerical studies are conducted for the same inlet particle concentration and velocity of the different cyclone separators.It will be more convenient to contrast the separation characteristics of the cyclones with different inlet section angles when the other conditions are all the same. Moreover, a small experiment platform is built to test the efficiency of the cyclone.In this section,three cyclone models are made .They are completely the same with the ones in numerical simulations in every details.The particles that are trapped in the dustbin will be collected every times when the experiment is over.They will be used to calculate both the total efficiency and grade efficiency.And in addition, inlet particle concentration is also invariable,but the inlet velocity will be controlled from low to high for every cyclone.The result shows that the separation efficiencies have increased by five percent and the pressure drops have decreased by more than ten percent when the cyclone separators have different inlet section angles. At last,a mathematical model of grade efficiency is obtained based on the time pause model and shortcut flow model.This mathematical model is suit for the syclones that have different inlet section angles.The result shows that vortex finder length, vortex finder diameter and the inlet section angle play an important role in influencing the grade efficiency.And it is helpful for the scholars to have a further study on the cyclone separators that have different inlet section angles.These are the three methods to study the separation characteristics of the cyclones that with different inlet section angles in this thesis. The predicted separation performances are confirmed by means of contrasting the results.They show that the new cyclone with a inlet section angle has higher efficiency than the traditional one while its shortcut flow rate and pressure drop seem to be lower.
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