Numerical Simulation Of The Stress And Overall Deformation Of Supercharged Boiler Drum

As the core device of the broad scale marine power system,the supercharged boiler is mainly responsible for generating high-temperature and high-pressure steam to ensure the normal navigation of the ship and the conventional power demand of the ship.When the ship is running,it is often necessary to adjust the speed according to the missionrequirement.This demands the main steam power system possess high maneuverability to meet requirements of the ship’s variable speed navugation.This makes thenumber of times of operation in the supercharged boiler extremely increased,and the fluctuation of the load willcaused the superchargedboiler drum to be subjected to frequent reciprocating stress shocks.How to accurately predict the dangerous section of the drum and calculate the fatigue damage of the drumis a tough problem in engineeringproject,and it is also a bottom line to ensure theoperation safety of the ship.When the boiler is in operation,bolt cutting and cracking of the guard plate often occur,resuting in leakage of high temperature and high pressure flue gas,which endangers the life and property of the crew.It is important to determine the displacement law of the supercharged boiler drum to give a corresponding guidance for the problem of unreasonable structural design.At current research stage,the accurate calculation of the stress field and fatigue characteristics of the supercharged boiler drum is not enough and the overall displacement research of the drum in actual operation is extremely rare.In this paper,the marine supercharged boiler is theobject of research,and the temperature field,stress field and displacement characteristics of the supercharged boiler drum are studied deeply.Firstly,based on reasonable physical assumptions,the finite element model of the supercharged boiler drum was established.At the same time,the important structural details such as ellipsoidal head and solid tube bundle are introduced for the first time,which solves the problem that the overall displacement characteristics of the drum can not be calculated due to the imperfect model of the supercharged boiler drum;Secondly,the rationality of thesupercharged boiler restraint application scheme is discussed and analyzed.For the first time,a constraint scheme for fixed support of tube end faces was adopted.which solves the problem that the stress intensity of the dangerous point is incorrect due to the constraint placed on the cross section of the drum;Thirdly,based on the results of grid-independent solution verification,thesupercharged boiler drum and tube bundle model is reasonably meshed,and a highly accurate grid system is obtained,which solves the problem that the calculation result is not credible due to the defect of the grid system.Finally,based on the above schemes,the finite element multi-physics field of supercharged boiler drum under steam pressure fluctuation condition and cold start condition was carried out,the position of the dangerous section of the drum was determined,the center displacement and angle of the drum are calculated,and the strength of the dangerous point is checked,and the fatigue damage of the drum under each working conditon is calculated.The calculation results show that the steam pressure fluctuation condition and the cold start condition of thesupercharged boiler drum’s dangerous point position appear in the tube sheet radiation area,and the maximum stress intensity of each tube hole along the axial direction of the drum shows a trend that otter sidelarger than middle side.Compared with the thermal expansion effect of the drum,the expansion effect of the tube bundles is stronger,and the displacement of the supercharged boiler under high temperature conditions is mainly caused by the thermal expansion of the tube bundles.Due to the higher stress level of the tube sheet under the condition of steam pressure fluctuation,the possibility of strength damage of the drum under the cold start condition is lower than that of the steam pressure fluctuation condition;However,due to the larger fluctuation range of the stress amplitude,the fatigue damage caused by the single cold start condition to the drum material is about 1.8 times than that of the single steam pressure fluctuation condition.