Turbine Blade Surface Deterioration by Erosion

Abstract

This paper presents the results of a combined experimental and computational research program to investigate turbine vane and blade material surface deterioration caused by solid particle impacts. Tests are conducted in the erosion wind tunnel for coated and uncoated blade materials at various impact conditions. Surface roughness measurements obtained prior and subsequent to the erosion tests are used to characterize the change in roughness caused by erosion. Numerical simulations for the three dimensional flow field and particle trajectories through a low pressure gas turbine are employed to determine the particle impact conditions with stator vanes and rotor blades using experimentally-based particle restitution models. Experimental results are presented for the measured blade material/coating erosion and surface roughness. The measurements indicate that both erosion and surface roughness increase with impact angle and particle size. Computational results are presented for the particle trajectories though the first stage of a low-pressure turbine of a high bypass turbofan engine. The trajectories indicate that the particles impact the vane pressure surface and the aft part of the suction surface. The impacts reduce the particle momentum through the stator but increase it through the rotor. Vane and blade surface erosion patterns are predicted based on the computed trajectories and the experimentally measured blade coating erosion characteristics.

Deterioration of Thermal Barrier Coated Turbine Blades by Erosion

“…Figure 4 shows the threedimensional H-O computational grids used in the NASAdesigned turbine flow field and particle dynamics simulations. Grid size was based on our prior experience in large commercial engines [16]. The grids were clustered near the blade passage surfaces to achieve the y+ < 3 at the first grid point next to the surface.…”

“…The simulations require the 3D flow field and blade passage geometries as inputs and a model for particle restitution conditions following each surface impact. The basis for particle trajectory simulations in turbomachines continues to be Eulerian-Lagrangian with one way coupling between the particles and flow [15,16]. Currently threedimensional flow field solutions of the Reynolds averaged Navier-Stokes equations for turbulent flow through the blade passages [16] are used in turbomachinery trajectory simulations.…”

Solid particle erosion mechanisms of protective coatings for aerospace applications

“…The Cr-Si-N coating with C Si = 11.6 at.% presents a texture change from (111) to (200), indicative of coating densification because (111) textured coatings typically possess a more opened structure, with more voids between the columns [229]. The important decrease of d g combined with the change in texture seems to indicate that for this latter coating, the limit of solubility has been exceeded and that segregation of SiN x around CrN grains has occurred, changing the growth mechanism [4][5][6][7][8]. This nanostructural change resulting in microstructural densification seems to lead to an increased H v with a related decrease in ER 90 .…”

“…In fact, compressor blades typically show preferential erosion of the trailing edge where the particles impact with trajectories nearly parallel to the surfaces (Figure 1.2). Figure 1.2: Typical damage to a compressor blade [5].…”

“…In particular, the group of Tabakoff have evaluated many different coatings found in aerospace applications (Pt-Al, Rd-Pt-Al, CrC, NiCrC, Cr, WC-Co, TiC, TiN, Al 2 O 3 and CVD diamond) in a specially constructed high temperature erosion test rig that simulates, as closely as possible, the particle impact conditions found in the engine [5,121,128,[138][139][140][141][142][143][144][145][146][147][148][149][150][151]. Although most of their studies were comparative, they have shown that in many cases the increased ductility at high temperature is beneficial for erosion resistance of hard coatings.…”