Numerical Simulate On The Induction Heating Coupled Ignition And Steady Combustion

Over the years,induction heating technology can heat the workspecies fastly with fewer enengy,so it has been used in many fields.In this paper,induction heating technology is applied to the pulverized coal burner with large regulation ratio.The high temperature wall with fast heating is used to ignite the pulverized coal flow directly,so as to be applied to the ignition and low load stable combustion process of 600 MW subcritical boiler.The detailed simulation study of this technology will be expected to solve the problem of restricting the consumption of wind and solar power in power grid,and make the flexible and deep peak shaving of power station boiler possible.The simulation work of this paper is mainly based on ANSYS 2019r3 software,which is divided into three stages: the wall heating stage of induction heating,the pulverized coal ignition stage in the burner and the low load transformation stage in the furnace.The simulation of the temperature rising process of burner wall using induction heating technology.Firstly,the data interface is created by using Python language,and the joint simulation between Maxwell and fluent is carried out.Considering the real-time response of the simulation results to the nonlinear change of material properties with temperature,the bidirectional coupling simulation of induction heating process is realized.After that,the thermal conductivity and conductivity of cr25ni20 cast steel used in the front section of the burner were tested with temperature,which provided the original data basis for the simulation.The eddy current field,magnetic induction field and temperature field after induction heating are calculated by unidirectional coupling method and bidirectional coupling method respectively.The results show that: when the material properties change sharply with temperature,the error between single and two-way coupling simulation results is large,so the two-way coupling simulation method should be used.The heating effect of cr25ni20 cast steel is poor,and the eddy current loss is very small.Therefore,the front-end material is optimized.After comparison,it is found that the heating effect is better when the front-end material is replaced by Si C.In addition,under the double restrictions of material service life and flexible peak shaving,a more reasonable heating mode is determined,that is,overall heating,excitation current of 350 A,frequency of 8k Hz and heating time of 18 min.The simulation of the transient process of ignition of pulverized coal flow on the high temperature wall of the burner.Based on FLUENT software,the two equation model is used for the gas-solid turbulent flow model,the stochastic track model is adopted for the gas-solid two-phase flow model,the mixed fraction PDF model is used for volatile combustion,the dynamic diffusion control model is used for coke combustion,and P1 model is used for radiation model.Firstly,the experimental data in the relevant literature of Zhejiang University and the field experimental data in this paper are compared and verified respectively.The simulation results is similar to the experimental results,it has been proved that the simulation is reliable.The results show that the existence of heat conduction plate and blunt body in the burner can promote the combustion of pulverized coal gas to a certain extent,and the role of heat transfer plate is greater than that of blunt body.The higher temperature the wall is,the ignition is getting better and better.The suitable temperature of powder injection is 1150℃ in consideration.The ignition condition is the best when the concentration of pulverized coal is 0.380kg/kg,and the temperature distribution at the exit section of burner is uniform,which is the best concentration of pulverized coal under this condition.The simulation of the low load combustion process in the whole furnace of a600 MW subcritical boiler.Firstly,the basic working condition is simulated with the data of 50% BMCR,and the temperature at the bottom of the partition screen at the upper part of the furnace is taken as the verification temperature.The simulation results are compared with the data in the thermal calculation table of the boiler,and the error is less than 10%,which proves the credibility of the numerical simulation of the whole furnace.The steady-state calculation of pulverized coal ignition process in the burner studied in the second part is carried out,and the temperature,velocity and component concentration distribution at the outlet of the burner are taken as the inlet conditions of the C-layer burner in the furnace.The distribution parameters of temperature and velocity field before and after the transformation under 30% low load condition are compared and analyzed.The results show that:after the transformation,the flue gas temperature level in the furnace increases as a whole,the high temperature areas are concentrated in the main combustion area and the upper area,which are symmetrically distributed,the cross-section of the primary air nozzle in the transformation layer and adjacent layers is complete and the flue gas fullness in the furnace is high.Overall,the effect of the transformation is obvious,and the ability of the boiler to maintain stable combustion under 30% low load is significantly improved.