Numerical Simulation And Optimization Of Flow Field Distribution In A Low-resistance Flue Gas Duct

With the rapid development of economy, energy consumption and environmental pollution is aggravating in China. So more and more attention has been paid to energy conservation and emissions reduction of the industrial production process. Coal-fired power plants play a major role in the electric power industry, which dominates the China's energy structure. It is therefore important to reduce energy consumption and dust-linked pollution resulting from coal-fired power plants by improving the performance of the downstream flue gas duct. In addition, flue field uniformity of the flue gas ducts can minimize the wear and tear of flue gas ducts and also prolong their service life.Flow field uniformity usually depends on the design of flue gas ducts in a coal-fired power plant. As a commonly used special part in flue gas ducts, the flue pipe bend has been studied by domestic and overseas scholars through many points of view. However, there is little research on flue gas ducts with inner supports which are usually used in practical engineering. Meanwhile, inner supports should not be ignored since they play an important role in the flow field distribution. Referring to the bend-straight pipe combination and bend-bend combination which consist of the standard flue gas ducts and the CE-Scheme flue gas ducts usually used in power plants, this paper studied on gas pressure and velocity distribution of electrostatic precipitator inflow duct by means of computational flow dynamic(CFD) approach. Also common bends with conventional guide plates which are installed upstream electrostatic precipitators were simulated. On the basis of the analysis about original pipes, the optimized pipe was designed. The result shows that about 50 percent of the total pressure loss is caused by inner supports and it can be concluded that inner support is one of the main causes of the pressure loss. Furthermore, the standard inner supports are superior to the CE-Scheme inner supports in a bend-straight pipe combination,but it is not obvious to a bend-bend pipe combination. Conventional guide plates arrangement can improve the flue flow field uniformity, but it is better to be replaced by a component which can act not only as guide plates but as inner supports as well.Referring to the results from simulation, new flue gas ducts are designed. Changing sharp bend to successive bend is proposed as the design concept. The outlet-velocity in the optimized ones is more uniform and their pressure loss decrease about 40 percent in the new-design bend-bend pipe combination than that of original model. The new designed bend-bend pipe combination gain varying degrees of good results.The results provide theoretical basis and guidance for the arrangement of the flue gas duct with inner supports and guide plates.