Thermal Stress Calculation And Analysis Of Small Supercharged Boiler Drum

The drum is one of the most important pressure parts in supercharged boiler. During theprocess of starting or stopping and altering loads of the marine supercharged boiler unit,rising or dropping of the pressure and varying of temperature of wall will make the drumendure great mechanical and thermal stress. The frequent varying of the stress will result infatigue damage to drum material and shorten the service life of the drum. The structure andheated situation of supercharged boiler drum is very complex. At present, the research of thesupercharged boiler drum’s temperature field and thermal stress field is relatively small. Thetraditional algorithm for power station steam drum temperature field does not apply to thedrum of the supercharged boiler. The purpose of this paper is to seek a suitable superchargedboiler drum temperature field and thermal stress field calculation and preparation of thecorresponding computer program, in order to monitor the drum temperature field andthermal stress field changes when supercharged boiler is running and give guidance on thesafe operation of the supercharged boiler.In this paper, Harbin Engineering University small supercharged test boiler drum is thestudy object. The temperature data acquisition system of drum inside and outside wall hasbeen built. Inner and outer wall temperature data has been processed and analyzed underdifferent operating conditions, and the temperature distribution of the drum has beenobtained. The axial temperature difference of the outer wall and the hoop temperaturedifference the inner wall are small, while the hoop temperature difference of the outer walland the temperature difference between the inner and outer wall are large. Therefore, in thecalculation of the thermal stress, the axial temperature difference of the outer wall and thehoop temperature difference of the inner wall can be ignored. In this paper, the superchargedboiler drum is simplified as a two-dimensional model. The drum temperature field is solvedby combining the direct solution of the heat conduction problem and backstepping solution.Through the coupling of positive and negative issues to resolve the problem that separatebackstepping solution or direct solution can’t solve the entire drum temperature field. TheFORTRAN and C++language are used to write the temperature field calculationprocedures.In this paper, the finite element model of drum has been established using the finite element analysis software ANSYS. Numerical simulation of the drum’s steady mechanicalstress field, thermal stress field and the total stress field have been conducted under thefourth combustion condition. The position of the maximum stress value has been found. Thedistribution law of the stress field of the drum has been obtained and the theoreticalmechanical stress concentration factor and thermal stress concentration factor have beencalculated. The mechanical stress concentration factor recommended by ASME standard hasbeen corrected. The stress intensity evaluation has been done to the drum, and theassessment results meet safety requirements. In this paper, based on the plane strain problemand the finite element method, the drum stress field calculation subroutine is designed andwrote using FORTRAN language. This subroutine is able to achieve the thermal stress,mechanical stress and the calculation of the total stress. For the small supercharged boilerdrum, the program running results show that total stress caused by the internal pressure andtemperature, the thermal stress attributable to main portion. Finally, based on therainflow-counting method, the stress amplitude statistics subroutine RAINFLOW is wroteusing FORTRAN language.