Kilchenstein, G., Juarez, F., Moseley, M., Cheverie, J. et al., "Compressor Airfoil Protective Coating for Turbine Engine Fuel Efficiency," SAE Technical Paper 2013-01-2187, 2013, doi:10.4271/2013-01-2187.
Small media ingestion has been known to cause erosion and result in corrosion to compressor components of gas turbine engines. Compressor degradation negatively impacts fuel consumption, engine performance, reliability, and maintenance costs. Power losses in the compressor section are often unrecoverable without increasing fuel consumption; therefore, protecting the compressor from excessive erosion/corrosion may extend the life of an engine, and reduce fuel, maintenance costs, and emissions.A study was conducted to investigate the effect of a new compressor blade and vane erosion/corrosion resistant coating on two Rolls-Royce T56-A7-B engines. The study included a comprehensive sand ingestion test that compared the performance and hardware condition of uncoated and coated compressor airfoils before, during, and after sand ingestion of 135 pounds of sand mixture. As part of the objective, the benefits of a new erosion/corrosion resistant compressor airfoil coating were quantified in regards to fuel efficiency, engine-time-on-wing (ETOW), emissions, fuel costs, maintenance, and engine readiness.Engine performance tests were conducted on both an uncoated and coated compressor engine at the start and end of the sand ingestion cycle. Sand was ingested into both engines until a finite amount of media had been consumed. The engine with the coated compressor demonstrated significantly better performance than the engine with the uncoated compressor as measured by corrected shaft horsepower (CSHP), compressor discharge pressure (CDP), and specific fuel consumption (SFC) at the post-test evaluation. The reduced fuel consumption benefits of the coated compressor engine also translated into reduced emissions and sizable decrease in SFC.The condition of the compressor airfoils was documented throughout the test via chord measurements, surface roughness measurements, optical scans, and photographs. The observations and inspections exhibited smoother surface finish characteristics, excellent leading edge (LE) profile protection, and greater chord and thickness loss protection than the uncoated blades.A return-on-investment (ROI) sensitivity analysis was conducted based on the engine test results and a Reliability Centered Maintenance (RCM) analysis. The ROI analysis accounted for potential ETOW improvements, annual parts savings, and fuel consumption savings. The ROI sensitivity analysis resulted in positive ROIs in the years to follow after implementation. The erosion/corrosion resistant coating demonstrated significant benefits for the T56 engine operations that are expected to translate into reduced maintenance, fuel costs, emissions, increased ETOW, and engine readiness.