Direct Numerical Simulation Of Erosion Of Tubes And Sidewalls By Coal Particles

Many industrial applications such as coal combustion equipments, heat exchangers and chemical plants encounter serious problems from the tube erosion in tube banks caused by particle impacts on tube sidewall. With the development of computational fluid dynamics (CFD) the numerical study becomes to be a useful tool to study the material erosion.The computational fluid dynamics tool is applied to investigate the wear of the side walls by coal ash particles when these particles follow a cross flow past a 10×11 staggered tube bank. The flow field is obtained through direct numerical simulation, the coupling between tubes and flows are done through the immersed boundary technique and the trajectories of particles are tracked by Lagrangian approach with two-way coupling method. Finally, we find particle collision frequency distributions and sidewall erosion rate distribution.We get the conclusion that erosion rate is the main factor to erosion, and also have the results as follows,1 For the first column tubes in the flow direction, the erosion is increasing by the particle size.For the second column tubes in the flow direction. the erosion made by the particles with diameter 62μm is the largest. The erosion made by the particles with diameter 6.2μm can be ignored.2 The erosion made by different diameter particles to sidewall is similar. To the small size particles the erosion is increased because the chaotic eddy near the wall increases the collision frequency of small-scale particles to channel wall. For the large size, as the particle inertia increase, particles can pass through the shear layer and collide with the channel wall. The increase of erosion rate makes the mass erosion on the wall augmented.