Numerical Simulation Of Pressure On Superheated Boiler Drum In Vapor Pressure Fluctuation Process

Supercharged boilers,as the source of steam for the main power plant of large ships,are particularly important for their safety and reliability.Due to the reasons such as starting or stopping the furnace too fast,sudden load changes,large disturbances of steam supply and accidents,the drum pressure and wall temperature will fluctuate within a short time,resulting in a high level of cyclic stress amplitude in the tube and tube area of the drum.Accumulation over a long period of time can cause plastic barrel damage and low-cycle fatigue damage,directly threatening personal safety and equipment safety.Therefore,it is of great significance to study the stress field and fatigue life of the pressurized drum during the steam pressure fluctuation process for the design and actual operation of the power system.This paper takes the supercharged boiler drum as the research object,and focuses on the key issues such as the model structure,grid size and constraint method involved in the calculation accuracy.First,the same semi-bulging connection model as the actual engineering is established,which solves the problem that the inaccuracy of the previous model causes the position of the dangerous point of the drum and the distortion of the stress level.Secondly,the local refinement and independence verification of the grid is implemented,which solves the problem of low computational accuracy due to the uniform size of the model grid.Again,using the distal end of the barrel to restrain the way to solve the stress concentration caused by the previous fixed constraint method.Finally,using the measured data to verify the calculation results,the trend and accuracy meet the requirements,which proves the effectiveness of the above work.Based on the above research results,a three-dimensional numerical simulation of the entire steam pressure fluctuation process of the drum is performed.The results show that the cold start-up process and the large fluctuations in the steam pressure produce a high level of stress in the drum radiation area.In the cold start constraint,the drum fatigue damage mainly occurs in the unsaturated stage.The total stress in this stage is mainly dominated by the thermal stress generated by the wall temperature difference of the drum wall.When the working fluid in the drum reaches saturation,the total stress at the danger point of the drum is affected by both mechanical stress and thermal stress.In the actual operating pressure fluctuation process,the greater the pressure fluctuation amplitude,the greater the stress amplitude change at the dangerous point of the drum,the greater the fatigue damage.The research results can provide a theoretical basis for the design and safe operation of the power system.