Abstract
The article presents a water-wall tube panels simulation technique that uses finite element method as well as the power boiler water-wall structure design optimization method. Results of the proposed method verification and its application to the design of boilers of different capacities are discussed. The technique is to replace water-wall tube panels with equivalent plates. Replacement plates’ parameters calculation is reported, panels one-way heating metering is described. Optimization of the water-wall structure design is carried out in two stages: at the first stage, water-wall tube panels are replaced with orthotropic plates; at the second stage, sub-simulation with solid models is used to identify problem areas of the design. Solid-state models of the problem areas get connected to the orthotropic plates at calculated boundary conditions. The described approach improves accuracy of the simulation results and significantly reduces the models complexity and its computation time. The proposed simulation and optimization method has been tested and successfully applied to design power steam boilers with steam generating capacity of 500, 1030 and 1900 tons of steam per hour. As a result, while maintaining the specified reliability and durability, significant reduction of metal content in boiler structure is achieved.
Highlights
Modern power boiler is a sophisticated unit based on the system of membrane tube water walls gastightly connected into a water wall structure normally including a furnace, one or two connecting gas ducts and one or two convection shafts
The water-wall structure itself is suspended from and/or supported by the steel structure; it is equipped with buckstays and serves for supporting or suspending the burner devices, piping and other boiler structure parts
The key part in the boiler structure optimization is given to the three-dimensional numerical finite element simulation
Summary
Modern power boiler is a sophisticated unit based on the system of membrane tube water walls gastightly connected into a water wall structure normally including a furnace, one or two connecting gas ducts and one or two convection shafts. Efficient finiteelement simulation methods development is one of the major tasks to ensure strain-stress state analysis and optimization of all-welded gastight structure design of power boilers at minimum labour input and minimum computation time The latter is due to the use of reduced plates instead of solid water wall models that considerably decreases the model “weight” maintaining simulation accuracy. Goldberg [1] presented a procedure for constant elastic orthotropic plates calculation without considering the difference in the water wall behavior at membrane and momental loading, which was justified by insufficient development of the simulation techniques at those times Such approach yielded results within an inacceptable error limit. This article describes a new technique that combines analytical and numerical methods of reduced orthotropic plate elastic coefficients determination by making corrections in the elastic coefficients calculated analytically on the basis of the numerical modelling results and mandatory consideration for the shear components which essentially influence strainstress state of water walls, especially under normal water wall loads
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