| Particles contaminating the secondary air system of land based gas turbines or aero‐engines can cause serious problems in various engine components, particularly in the cooling system. The capability of the pre‐swirl system in separating particles will be described in this paper. So far, only a few publications can be found on experimental investigations on this subject. The work presented in this paper attempts to give a contribution to fill this gap and thus represents a further step towards a better understanding of the behavior of solid contaminants in the secondary air system. Due to the strong swirl in the pre‐swirl cavity, the aero‐dynamical forces can be used to separate particles, thus preventing depositions inside the turbine blades or even blockage of the film cooling holes. Numerous experiments in a pre‐swirl system have been performed using spherical particles and non‐spherical particles. As reference cases, three types of spheres, with two size ranges and different materials, were used to understand how size and density influence the separation efficiency. For further experiments, irregularly‐shaped particles, more similar to the ones found in real aero‐engines, were used too. The separation efficiency was investigated at different pre‐swirl nozzle pressure ratios, rotational speeds and radial mass flows. The results are presented in relation to the particle Reynolds numbers, drag coefficients, Stokes numbers and swirl ratios in the pre‐swirl cavity. |
