Book Description

The damage due to particulate matter ingestion by propulsion gas turbine engines can be significant, impacting the operability and performance of compressor, combustor and turbine components. Here, focus is on the axial compressor whose blades become damaged when operated in dusty/sandy environments for extended periods of time. This results in significant performance degradation of the compressor and hence, the entire plant. Accordingly, prediction of the impact of specific particle damage morphologies on compressor aerodynamics can be of significant benefit to aircraft operators concerned with fuel efficiency and on-wing platform readiness. In this work, novel CFD methods are developed aimed at modeling the effects of particle ingestion airfoil damage on axial compressor performance. Specifically, the goal of the research is aimed at mechanistic (vs. empirical) prediction of the significant aero-thermodynamic, and attendant loss implications, for a range of damage morphologies. To this end, we study the first stage rotor blading of a GE T700-401C compressor. This five-stage axial machine is subject to current testing at NAVAIR, in a well instrumented facility. A secondary goal of this thesis research is to provide physics understanding and pre-test predictions associated with damage modes that have been observed in these systems. In this work, thermoplastic additive manufacturing is used to build a number of baseline undamaged stage 1 rotor blades, and then heat and tooling treatments are applied to obtain representative physical models of three of these modes -- ballistically bent/curved leading edges, spanwise cragged erosion of leading edges, and eroded leading/tailing edges at outer span locations. The resultant damaged plastic geometries are then optically scanned and incorporated into sublayer resolved Reynolds Averaged Navier-Stokes (RANS) analysis. Target conditions are imposed that conform to damaged compressor operation protocols, and an iterative process for accommodating corrected mass flow and off-design powering is developed and presented. The code, modeling and meshing strategies pursued here are validated, using a study carried out for NASA Rotor 37 -- these results are included and provide confidence in the predictions of the T700 geometry studied. The results for the steady-state calculations for the rotor only configuration, in the rotating frame of reference, are presented in terms of compressible wave field and secondary/tip flows, spanwise performance parameter distributions and efficiency. A method to estimate the effect of rotor damage on engine SFC is devised and presented. This enabled the rank ordering of the different damage modes in terms of the overall performance parameters. Time accurate rotor-stator calculations are then performed for the full stage configuration. These results are also presented in terms of compressible wave field and secondary/tip flows, spanwise performance parameter distributions, efficiency and estimated impact on plant Specific Fuel Consumption (SFC). The different damage modes are classified based on the overall performance parameters. Relevant observations include significant differences between the steady state rotor only calculations and the full stage unsteady calculations with different damage morphologies. A combined Eulerian-Lagrangian methodology was also deployed on the axial compressor configuration in this research, in order to initiate a "full-field" simulation approach wherein the damage process itself is modelled. Method validation is performed using a well-documented data-set for sand in air erosion at high Reynolds number. The results are presented in terms of eroded surface profiles and eroded surface time evolution history and conclusions are made. A qualitative assessment of the impact of erosion on the NASA Rotor 37 blade surface is performed and discussed. Assessments and recommendations for future multiphase flow damage modeling are made.