Numerical Simulation of the Blade Aging Process in an Induced Draft Fan Due to Long Time Exposition to Fly Ash Particles

Abstract

Erosion issues usually affect fans used for the extraction of exhaust gas in power plants. Because of the presence of fly ash within the exhaust flow, fan blades are subjected to material wear at the leading edge, trailing edge, and blade surface, and this may cause a modification of the blade aerodynamic profile, a reduction of blade chord and effective camber. All these effects result in a deterioration of the aerodynamic performance of the blade. Prediction of erosion process in industrial applications helps to better schedule the maintenance and predict the blade life. However, since usually numerical simulations of erosion process do not account for the change in target geometry, and then the variation in time of the erosion process itself, they can be only used to study a very short part (namely the beginning) of the whole process. To this aim, we report a numerical simulation of the blade aging process due to particle erosion in an induced draft fan. This is done using in-house numerical tools able to iteratively simulate the flow field, compute the particle tracking/dispersion/erosion, and modify the geometry (and mesh) according to the predicted erosion rate. First, we study the effect of the geometry damage due to erosion, for a generic particle flow and a given expected maximum damage. In the second part of the computation, a scale factor is introduced to align the simulation time and particle concentrations to a real application, comparing the results with the on-field observation.