Dust Particle Trajectories in Aircraft Radial Turbines

This paper presents the results of analytical and experimental studies of the trajectories that atmospheric dust particles follow as they move through a radial turbine. A dimensionless parameter is derived which can be used during preliminary design analysis to indicate the sizes of particles that will be most damaging to the turbine. The study reveals several internal surfaces that will be more severely eroded because most particles entering the turbine will strike them. A moderate amount of erosion can be expected near the end of the scroll and on the last few nozzle passages near the end of the scroll. All particles greater that 42/t will strike these surfaces. A severe erosion problem occurs on the nozzle trailing edges, because particles greater than 2-3fi will not penetrate the rotor. These particles are pushed outward by centrifugal forces where they bounce off the nozzle trailing edges. Particles greater than 1\\i have enough inertia to overcome the centrifugal force and these particles enter the rotor. After striking the rotor with a perpendicular impact, they also travel outward to the nozzle trailing edges.