An Innovative Approach to Model Temperature Influence on Particle Deposition in Gas Turbines

Abstract

The mechanism of deposit formation on the blade surfaces of a cooled turbine vane is investigated numerically. The prediction of dispersed particles trajectories is affected by temperature, by the mechanics of impact on a solid surface, and by the interaction between particles and film cooling jets and all these aspects must be accounted for. The model here proposed is obtained as a high temperature extension of the well-known Thornton and Ning (1998) approach in a temperature interval ranging between 500 K (where basic model — based on an elastic-plastic impact mechanism assumption — holds) and 1500 K (where the critical viscosity model of Walsh et al., 1990 is usually employed). The transition between the two extreme conditions is modelled through a temperature-driven modification of the mechanical properties of both particles and target surfaces. Our computations demonstrate that the updated model is able to return credible predictions of deposit formation when compared with the baseline models of Thornton and Ning and of Walsh and co-authors. Moreover in the region where particles bounce off, the model predict the coefficient of restitution according to the actual mechanical properties of particles, thus providing a better particle dynamics description than in both the critical viscosity and original Thornton and Ning models.