The assessment of the severity of engine in-service operation receives increased attention in the age of pay by hour maintenance programs. In this context, the degree of severity is defined as the relative damage experienced by an engine over a series of flights. There is a variety of physical phenomena contributing to this relative damage. Compressors erosion caused by particles ingested into the engine has been selected for the presented paper. The resulting damage arises from the complex interaction of factors such as particle properties, concentration and pathways as well as mechanisms of micro damage unique to the materials of the involved engine parts \[1-3\]. These factors depend on the engine operating point and prevailing environmental conditions, which in turn, are influenced by the flight mission.

Until now, the complexity of the involved physics prevents a detailed simulation of erosion damage over a significant operating period. Hence, a more effective method is presented which allows a general judgement of the severity of engine operation with regards to compressor erosion. The amount of material loss is selected as the parameter describing the degree of severity. This allows the use of flat plate jet abrasion experiments as the starting point of the numerical approach. Hence, specimen of the materials involved can be tested leading to a result reflecting particle properties as well as the specific micro damage phenomena.

The particle impingement conditions experienced by compressors parts throughout a flight mission are computed using a flight simulation for a short- to medium range aircraft including a twin-spool turbofan engine performance model and a mean line compressor computation. The flight simulation considers the flight segments, from taxi-out to taxi-in without holding. The environmental conditions are based on the International Standard Atmosphere (ISA) taking into account the average temperature deviation, particle mass concentration and tailwind or headwind. The aerodynamic aircraft coefficients are determined using Prandtl’s lifting-line theory. The flight path between departure and arrival is calculated with the equation of motion and the equation of the great circle. The engine power setting results from commanded power settings required for the particular flight segment or from the equations of motion. The performance model as well as the mean line computations are represented by maps to speed up flight mission computation.

This investigation reveals the material loss in the low pressure compressor being an order of magnitude smaller than in the high pressure compressor. Taxi-out with both engines operating and taxi-in with one engine operating generates more than 10 % of the total severity of the flight mission considering average taxi durations and taxi speeds. Despite of the short operating time of the take-off and take-off climb, about 20 % of the total severity of the flight mission are caused in these segments. The severities of the two flight segments climb and cruise have a significant impact on the total severity, if environmental particle mass concentration at high altitudes is considered. The flight segments descent, approach and landing with thrust reversers operating have a negligible influence of 2,5 % on the total severity of the flight mission. Landing without thrust reversers further reduces the influence on the total severity.

 

References

\[1\]   Schrade M., Staudacher S., and Voigt M., Monday 2015,“Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors,” *ASME Turbo Expo 2015: Turbine Technical Conference and Exposition*, American Society of Mechanical Engineers.

\[2\]   Hufnagel M., Staudacher S., and Koch C., 2018,“Experimental and Numerical Investigation of the Mechanical and Aerodynamic Particle Size Effect in High-Speed Erosive Flows,” J. Eng. Gas Turbines Power, 140(10), p. 102604.

\[3\]   Hufnagel M., Werner-Spatz C., Koch C., and Staudacher S., 2018,“High-Speed Shadowgraphy Measurements of an Erosive Particle-Laden Jet Under High-Pressure Compressor Conditions,” J. Eng. Gas Turbines Power, 140(1), p. 12604.


Estimation of Aircraft Engine Flight Mission Severity Caused by Erosion

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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