Numerical modelling of three-dimensional fly-ash flow in power utility boilers

A two-fluid Eulerian model in combination with a particle - wall collision model and generalized Eulerian boundary conditions for the particulate phase is employed to predict complex three-dimensional fly-ash flows which often cause severe erosion to boiler tubes located in power utility boilers. Mean momentum and mass conservation equations are solved for each phase using a finite volume scheme with two-way coupling and a modified renormalization group (RNG)-based k-ε turbulence model. Comparison of predicted particle concentration with measured data is made and excellent agreement is obtained. The detailed character of the particulate velocity field and concentration just downstream of the 180° bend shows a marked dependence on the Stokes number not previously reported.