Numerical Simulation And Optimization Of Three-dimensional Flow Field In A Superheater Of Certain Marine Boiler

Superheater is one of the important components of steam boiler.There are so many factors like uneven heat load on the tubes,uneven heating areas,uneven steam flow in the tubes and scaling in the tubes,which may cause high local temperature in the superheater tubes.This affects the normal operation of the boiler.Based on the super-heater structure for marine boiler,this thesis analysed the cause of heat deviation theoretically,studied factors which cause over-temperature pipe explosion,and introduced method which can calculate wall temperature of superheater tubes,by using"Gambit'" establish the overall 1:1 three-dimensional model of the superheater which contains the outside smoke of super heater and inside space of steam,choose reasonable boundary conditions.Take the basic equations of hydrodynamics and"k-s" turbulence model as the mathematical model,make three dimensional hot state numerical simulation of overall superheater flow and heat-transfer of the whole steam,directly get the distribution of steam pressure,steam mass flow,steam temperature,load of the wall,the proportion of radiation and other value of each part,and the distribution changes with the load.Then put forward suggestion on improving structures of header partition based on the heat deviation theory.The simulation results indicate:temperature of pipe wall becomes higher gradually along the flow direction of steam.The highest temperature and deviation is the main steam pipe in the second process,in the middle of the tubes.In this position,the flow of steam is low,but the heat load is high,which makes the high deviation,the high temperature steam and pipe wall,so it is dangerous,prone to over-temperature burst.The simulation results of the improved model indicate:distribution of superheater steam temperature,steam temperature of each tube outlet and average temperature of tube walls are well-distributed.Coefficient of heat deviation and wall temperature of tubes are decreased.The highest wall temperature is 1 OK lower than before,so the improvement can improve the safety of the superheater.Starting from the basic theory,the whole three dimension calculation and analysis of super heater in marine supercharged boiler has been realized.By coupling calculation about steam,pipe wall,smoke,get the law of heat transfer and flow of super heater,and establish the position of the highest temperature of pipe wall and the conditions of dangerous situations.The numerical simulation can be used on the optimizing design or accidental diagnosis of superheater of marine boiler,at the same time it can economize large numbers of manpower and material resources.Numerical simulation methods would be extensively applied to boiler design and operations safely in the future.