Structure Optimization And Stress Analysis With Fluid-structure Interaction Method Of Primary Air Duct In Circulating Fluidized Bed Boiler

In order to obtain the efficient use of space, curved ducts were applied widespread in smoke and wind system when boilers were designed and constructed. And flow characteristics were complex, such as uniform velocity distribution and separation region of gas-solid two-phase flow near the elbow, due to the design feature of the curved ducts.The flow characteristics can caused pressure and energy loss, and can caused unsafe flow measurement results and the pipeline vibration.Firstly, in the paper, lattice plate deflector was retrofitted at the entrance of the straight pipe section according to the special structure of primary air duct in circulating fluidized bed boiler. By using the commercial software ANSYS workbench, the structure of the lattice plate deflector was optimized, including identifying grid number, grid height,the angle of the grid with the pipe axis and grid plate thickness, etc. Optimization results were obtained. And the grid number was 4×4. The angle to the pipe axis was 10 °. The height of the plates was 240 mm, and the thickness is 4 mm.Secondly, the experiments was carried in circulating fluidized bed boiler in order to verify the accuracy of the optimization results. Velocity distributions were measured in hot primary air pipe with and without lattice plate deflector at three working conditions.Experimental results showed that after adding deflector, velocity distribution was uniform at the position of the air flow measurement device. And that played the flow diverter effect. At the same time, the simulation results are in good agreement with the experimental results, and it shows that the accuracy of the simulation result is higher.Finally, using the unidirectional flow solid coupling method, statics analyses, modal analyses, harmonic response analyses and fatigue analysis in hot primary air pipe with and without lattice plate deflector were carried by ANSYS workbench software. Statics calculation found that after adding diverter, the working condition of the next duct maximum deformation and maximum stress is slightly increased compared to that before adding diverter, showed the diverter to add to a duct structure has an effect, but little impact; Modal analysis found that adding a wind pipe after the diverter than add diverter before the natural frequency at all levels should be small; Harmonic response analysis found that adding a wind pipe after the diverter resonant frequency is smaller than before adding; Fatigue analysis found that the fatigue analysis results before and after adding diverter basic same, showed the diverter add not to a duct extra fatigue damage.According to this paper, the study found a duct path in circulating fluidized bedboiler with grid pipe flow diverter has obvious improvement, for the vibration of the pipeline has a certain influence, has no effect on pipeline life almost. Therefore, in a wind pipe bending add raster diverter improve the flow field of the method is feasible.