Analysis And Online Monitoring Of Transient Temperature Field And Stress Field For Turbo-charged Boiler Drums

Drum is the largest thick-walled high-temperature component undertaking pressure of a turbo-charged boiler, whose frequently start/stop and working under variable load lead to the temperature and stress of drum changing dramatically, which shortens the service life of the drum. Therefore, the development of the online monitoring system for turbo-charged boiler drums, real-time monitoring the temperature and stress distributions of the drum and guiding the operation of boiler, has important significance to improve the safety and economy of boiler operation. How to improve the calculation accuracy of the drum temperature and stress field while ensure the high efficiency, is the key of the online monitoring system.Combined with the characteristics of the turbo-charged boiler drum outside surface locally heated, a coupling method of direct and inverse heat conduction problems was proposed for transient temperature calculation of the drum, and by programming the drum section temperature field was obtained. Then on this basis using the finite element method, in accordance with the plane strain problem, the transient theory stress of the drum section was analyzed.In order to verify the accuracy of the program, by making use of the software Ansys, the 3D transient temperature field and stress field of the drum during a cold-state startup were calculated, as well as the 2D transient theory stress. A comparison was made to the temperature distribution obtained by numerical simulation together with experimental values and the coupling method calculation temperatures, results show that the coupling method has high precision and strong adaptability under complicated boundary conditions. The stress concentration factors which got by comparing the 3D stress and theory stress were used to modify the stress determined by program, to quickly and accurately obtain the stress distribution of the turbo-charged boiler drum.Based on the rain flow counting method, the Miner linear cumulative fatigue damage principle was used to calculate the life loss of the drum according to the stress simulation results. Meanwhile, the stress intensity was checked for the connection between the drum and the downcomer tube. Finally, an online monitoring system for turbo-charged boiler drums was developed to guide the safe and economic operation of the boiler.