Finite Element Analysis Of Supercharged Boiler Based On Shell Element Tube Bundle

The supercharged boiler is mainly responsible for providing high temperature and high pressure steam for ships to meet the steam demand of ships.Because the ship often needs to adjust the speed according to the requirements of the task,the number of off design operation of the supercharged boiler is significantly increased,and the large disturbance of steam supply causes the supercharged boiler drum to be subjected to frequent reciprocating stress impact,resulting in higher stress amplitude in the tubesheet area.Long time accumulation will cause the drum plastic damage and low cycle fatigue,threatening the safety of personnel and equipment.In this paper,taking the marine supercharged boiler drum as the research object,the key problems of the wall temperature distribution of the superheater tube bundle of the supercharged boiler and the time-consuming solution in the process of solving the stress field are mainly solved,and the stress distribution characteristics of the drum under the condition of steam pressure fluctuation are analyzed.For the problem of superheater tube bundle wall temperature,Fluent was used to simulate the flow and heat transfer,and the temperature field of tube bundle was obtained,which solved the problem of inaccurate calculation of displacement field due to the temperature can not be measured in the tube bundle area.Secondly,the finite element modeling method of body shell element combination was used,and compared with the whole solid element finite element model The accuracy and reliability of this method are verified,and the problems of large number of mesh nodes and long solving time in the process of solving the stress field are solved.Finally,the stress distribution characteristics and fatigue life of the supercharged boiler in the process of steam pressure fluctuation are investigated based on the body shell element combination model.The results show that: the wall temperature of superheater tube bundle fluctuates along the axial direction,the maximum axial temperature difference is 95.52?,and the maximum circumferential temperature difference is 32.50 ?;the wall temperature of the second row of superheater tube bundle is the highest,and the wall temperature of the second,third and fourth rows shows a decreasing trend;compared with the whole solid element modeling method,the temperature of tube sheet in the two models is higher Compared with the whole solid element model,the number of grid nodes in the tube bundle of the body shell element combination model is reduced by 63.90%,and the calculation time is reduced by 33.87%,which achieves the purpose of simplification.Under the condition of steam pressure fluctuation,the thermal stress level in the flue gas radiation area of the drum is the highest,and the stress value at the dangerous point is due to the thermal stress and mechanical stress The results show that the maximum coupling stress is less than the maximum thermal stress when coupled,and the drum of supercharged boiler meets the strength requirements under the steam pressure fluctuation condition.The fatigue life of supercharged boiler is calculated by JB4732,and the number of allowable cycles is 68386.Therefore,in the actual operation process,we should try to avoid large fluctuations in pressure.