| Gas flow distribution was one of the most important factors that affected collection efficiency of ESP(Electrostatic Precipitator),circulation resistance of baghouse and longevity of filter bag.Due to the complexity of gas flow in ESPs,the study of gas flow distribution is dependent on test observation for a long time.The result of model test only displayed the distributing status of gas velocity magnitude of the test section,it could not judge that the affection extent of the collection efficiency by gas flow stream status.Meanwhile,because it could not strictly meet similitude condition,it was greatly restricted on studying for gas flow distribution of baghouse.Studying the rule of gas flow stream in dust collector by using CFD (Computational Fluid Dynamics),can provide all the information of gas flow stream in dust collector and conduct a systemic research on the affection of singleness factors or interaction factors.This paper completed the numerical simulation of gas flow field in ESPs with Fluent software and validated the feasibility of simulation calculation and the reliability of results by contrast with the model test of gas flow distribution in ESPs.The simulation results can provide design datafor the configuration parameter of gas flow distribution devices in ESPs, and can also guide model test,reducing test workload.With numerical simulation for straight-through flow baghouse,it provides appropriate configuration form and parameter of gas flow distribution device,tallying with the locate test results.The rule of pulse-jet gas flow was simulated by simplifying filter bags as films and using two-dimension unsteady flow mathematics model.The reliability of numerical simulation was validated by lots of literature data.The author established simulation scheme by using orthogonal layout,and gave the value range of the main parameter of the pulse-jet device in different condition by comparing with the results of numerical simulation. (1) It has completed the model test of gas flow distribution for GP214-Ⅳstraight-through ESPs and tested the velocity magnitude and distributing status of inlet section of the first electric field under three different placing ways of guide vanes on gas flow distribution plates.Taking model test as study object,the paper finished the numerical simulation calculation of internal gas flow field in ESPs by using Fluent software.The models of simulation and test are same in size.The porous gas flow distribution plate is simplified as uniformity air plate with the same local air resistance:The model adopt mixed structured and unstructured grid to generate the mesh,simplify gas flow as problem of steady flow in the ESPs and select the normal k-εtwo equations model.At the same time,the gas flow distribution plates adopt porous model with the same inertia resistance coefficient.The simulation results can display all the interior gas flow fields and gas flow distribution status at different section of the electric field under different disposal ways.According to relevant disposal scheme of guide vanes,the distribution trend of velocity magnitude of inlet section in the first electric field are basically inosculate with two study ways.The relative standard deviation is:5.6%,3.6%and 3.2%(check index≤±10%).(2) By numerical simulating of the gas flow distribution in a 660MW ESPs,it determined the width and disposal angle of the splitter plates in pipeline to adjust flux distribution of two inlet diffuser,providing the disposal geometry parameter of guide plates in pipelines and guide vanes of guide plates in inlet diffusers.The local test results of gas flow distribution display that the inlet gas flux distribution deviation of inlet diffuser in ESPs is±2.3%(design check index≤±3%),and the relative standard deviationσof velocity distribution at the inlet section of the first electric field is 0.178(design check index≤0.2). Both of the indexes meet ESPs standard and the requirement of design check.(3) The paper used the numerical simulation results of gas flow distribution in a 240t/h boiler ESPs to guide the model test of gas flow distribution:The simulate results displayed that by increasing the number of guide vanes of the second gas flow distribution plates in inlet diffuser and adjusting the space between every two guide vanes,the distribution status of gas flow velocity were improved evidently at the inlet section of the first electric field.It also gave the disposal scheme of guide vanes of gas flow distribution plates whenσwas 0.133(design check index is≤0.15).According to simulation,guide vanes of test model were installed.The testing results showed thatσat the inlet section of the first electric field is 0.124.The distribution trend of gas flow velocity magnitude,which was reflected by model test,tallied with the results of simulation.(4) The straight-through flow bag house was taken as an example.The paper simulated the gas flow distribution in baghouse with fluent software,got the gas flow velocity distribution of the windward filter bag section in the middle tank,the flux distribution at inlet section in the middle tank,the flux distribution of every filter bag cell and the press drop of dust catcher.The results of simulation calculation were basically consistent with those of local test,which provided reference data for optimizing structure design of gas flow distribution in baghouse.The results of numerical simulation can be intuitionistic to display the gas flow velocity distribution at random section in dust collector.It can resolve the problem which is difficult to resolve in model test,such as that disposal and configuration of hopper baffles affect the gas flow distribution in bottom area of the filter bags and flux distribution of every filter bag cell,and the gas flow scour filter bag in filtrate cell of backward position,and so on.(5) According to the test conditions of the pulse-jet experiment ofΦ160×6000mm filter bag in literature,the results of simulation calculation could show the magnitude of peak pressure at different time and the distribution of that along the length of filter bag.The curve of peak pressure distribution on the surface of filter bag by simulation tallied with the testing results in literature.The author selectedΦ130mm filter bag as a research object,chose L16 (4~5) orthogonal layout to formulate the cases of experiment,and discussed the impact on peak pressure on the surface of filter bag,rising speed of pressure and maximum reverse acceleration inside the filter bag when main factors such as pulse-jet pressure,pulse-jet time, diameter of nozzle,the distance of pulse-jet and the length of filter bag change.It provided reference data for optimizing structure design of impulse pulse-jet device structure and pulse-jet parameter.The paper indicated that to study the rule of gas flow motion,using numerical simulation could advance the design level of the dust catcher,increasing collection efficiency, reducing equipment investment and operational and administrative expenses.
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