Research On Numerical Simulation Of Pulse-jet And Evaluation Of Filter Status Of Bag Filter

With the development of China’s economy and the continuous improvement of the industrialization process,the state has implemented stricter supervision and control of atmospheric emissions in the field of industrial production.As an important industrial environmental protection equipment for treating air pollution,a bag filter is an important indicator for determining the effect of dust removal.Therefore,the study of optimized injection cleaning bag filter and filter condition assessment is of great practical significance.In this paper,a numerical simulation study of pulse-jet cleaning for bag filter and an evaluation study of the filtration status of filter bags.The main contents are as follows:Firstly,the working method and composition structure of the bag filter are introduced,and the mechanism of pulse-jet cleaning and the main factors affecting the cleaning effect are analyzed in detail.In addition,the filter bag pressure change log data based on the pulse-jet cleaning was determined to establish a filtration state evaluation model.The research route is clearly carried out by first optimizing the design of the blowing system and then assessing the filtration status,which paved the way for the later research work.Secondly,for the numerical simulation of pulse-jet cleaning,a three-dimensional CFD numerical model was established under the consideration of jet misalignment.The conditions for establishing mathematical models were determined and the governing equations of fluid mechanics were solved according to the working conditions.The Realizable k-epsilon model was selected as the turbulence model based on the actual application.A geometric model was established to divide the fluid domain,the porous viscous resistance of the pulse valve was set to change with its opening and closing state.And the porous viscous resistance of the filter bag was set to a fixed value of 30 000 m·s^-1.A 10%resolution relative to the base size was used to mesh-encrypt the fluid domain parts with large calculation gradient changes.The correctness and validity of the numerical model were verified,and the foundation was established for the three-dimensional CFD numerical model used in the optimal design of pulse-jet cleaning.Thirdly,based on the above numerical model basis,a numerical model was established to optimize the design of the nozzle and the restriction flow device to improve the dust removal effect.Comparing improved nozzle with side wall opening and side wall without opening with original hole nozzle,the improved nozzle with a hole in the side wall improves the dust removal effect best,which makes the pulse pressure increase of each part in the filter bag the largest.The backflow limiting device can make the cleaning jet easier to enter the filter bag,and the optimized design for the backflow limiting device can significantly improve the dust cleaning effect.The optimized design to improve the dust removal effect is applied to the actual working conditions.The optimized design can reduce the atmospheric dust emission during the pulse-jet cleaning process.Finally,after applying the above-mentioned optimized design of pulsed spray cleaning,the filter log pressure change log data based on the pulse-jet cleaning is established,and a filtering state evaluation model based on a time-sensitive network algorithm is established.Considering the fastness and translation invariance of the one-dimensional convolutional neural network in processing long time series data,and the order sensitivity of the gated recurring unit to time series data.The network model based on the combination of 1DCNN-GRU solves the problem of long time-series feature extraction and sequential transfer.Through the linear calculation unit,the goal of pressure difference prediction of the filter bag was achieved.Simulation results show that the prediction model can effectively evaluate the filtering state.