| The bag filter has the very important status in the dust purification field because of its high dust removal efficiency.Pulse-jet cleaning is the most common and most efficient bag filter cleaning method in the current world,ash removal performance directly affect overall unit operation of dust collector.Most of the existing theoretical and researches focus on experimental study and numerical simulation effect of cleaning performance of the single factor or the random combination of several factors pulse jet cleaning system.In order to reveal forming process of pulse-jet airflow's cleaning effect in a filter bag,aiming at given specification and dimension of the bag and resistance characteristics of cloth and dust layer,follow the principle that the flux and kinetic energy of jet flow injecting into filter bag should be consistent with the flux of cleaning airflow in the bag and the pressure drop flowing through filter cloth and dust layer.Regarding achieving the peak pressure of cleaning airflow which dominate the effect of pulse-jet cleaning process as a target,construct a theoretical model of a relationship between cleaning system structure and operating parameters by using theory of gas jet and theory of unitary adiabatic flow.Cleaning system structure includes the pressure of gas in the nozzle,the structure and size of nozzle,exit velocity of nozzle,spray distance between nozzle and the critical section of nozzle's inlet and diameter of jet cross-section.Based on parameters of cleaning system structure and operating conditions which build by mathematical model,apply Fluent software to carry on a two-dimensional?unsteady and axial symmetry numerical simulation for jet airflow field at the nozzle's outlet,jet airflow field between nozzle and the critical section of nozzle's inlet and cleaning airflow field in filter bag.The results show that:when the top of bag has not any rectification measure,the peak pressure of condition 1?3?5?7are:-900Pa?-1000Pa?-350Pa?-380Pa;All of the top of bag are in-1500Pa;In addition to the area of near the top of bag,the static pressure and radial velocity from the top of 0.3m to the bottom of the bags are increasing and then decreasing following the order vs the injection time;Because of a large number of airflow escape from the bag to the upper box body,leading to a serious shortage of cleaning air's flux and a very limited rise of static pressure.After enlarged about 1.27 times of the theoretical value of nozzle's outlet diameter,the bag from the top to the 0.3m of bag is still in the filtration state,the other area's pressure in the bag reach the excepted value,the trend of pressure change is the roughly same as before modification,the gas consumption of condition 1?3 after modification is about 10 times of the theoretical gas consumption,condition5?7 is about 6.5 times,and the gas consumption of the four conditions is 1.3-2.5 times of their own back blowing fluxes.when the top of bag installs external rectifier,the peak pressure of condition 2?4?6?8are:1750Pa?1663Pa?2860Pa?3000Pa,reached 70%?66.52%?63.6%?66.67%of their own excepted value;The static pressure and radial velocity from the top to the bottom of the bags are increasing and then decreasing following the order vs the injection time.the results show the gap between static pressure of gas in the bag and expected value is significantly reduced and well-distributed in the bag.After enlarged about 1.27 times of the theoretical value of nozzle's outlet diameter,the pressure peak of cleaning air in filter bag achieve the expected value.The maximum gas consumption after modification are 39.39%?27.69%?48.14%?33.49%of their own maximum back blowing fluxes of the fours conditions.Numerical results confirm the theoretical model established by the mechanism which formed by compressed pulse-jet airflow and calculation method of pulse-jet cleaning system structure and operating parameters is correct.The study results provide more intuitive scientific basis for the further experimental. |
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