Impact of Sand and Dust on Jet Engines

Sand and dust from arid regions are increasingly a problem for aircraft gas turbine engines, both military and civil. The ingested mineral particles cause a number of different damage mechanisms, some of which accelerate the loss of engine efficiency, causing increased fuel burn, and a substantial reduction in component life, requiring early and expensive removal of engines for repair. The primary damage mechanisms affecting performance are erosion in high speed compressors and deposit buildup on turbine aerofoils. The primary damage mechanisms affecting component life (in the combustor and turbines) are corrosion-fatigue of nickel super alloys (when combined with atmospheric sulphur and NaCl), and CaO-MgO-Al2O3-SiO2 (CMAS) damage to ceramic thermal barrier coatings and blockage of intricate cooling systems. The financial impact of these problems on companies like Rolls-Royce is running into multiple billions of pounds. Rolls-Royce's business model depends on understanding the rate of engine performance and component life deterioration so the company can set the service charge rate correctly, and ultimately find design solutions to mitigate the damage. Rolls-Royce makes the bulk of its income from service - or power-by-the-hour - contracts with airlines. Charging airlines that regularly operate in sandy and dusty environments an appropriate hourly rate is vital to the Company's viability.
Substantial scientific work is being undertaken by both Rolls-Royce and The University of Manchester to better understand the composition and physical characteristics of atmospheric sand and dust along frequently used flight routes. This is because it is the composition and physical characteristics of sand and dust that drive the various damage mechanisms. However, our recent research has revealed that it is not sufficient to only understand the composition and nature of dust in the atmosphere because the chemical and mineral composition, physical characteristics and particle size distribution changes as sand and dust travels through a gas turbine engine. This ICASE project will focus on understanding the processes driving the changes in the sand and dust as it travels through a gas turbine engine intake, compression system and secondary air system before it gets to the damage sites in the combustor and turbines.
These processes require an understanding of the chemistry, thermodynamics, particle break-up, transport and differential fractionation under centrifugal loading of sand and dust particles. This project will involve an experimental study of key aspects of these processes and will contribute vital data needed to develop a computer model of the sand and dust transformation processes. In the first instance, empirical evidence will be derived from a controlled whole engine test conducted by Rolls-Royce using a mineral test dust produced by the University of Manchester. The student will work with engineers at Rolls-Royce to develop a sampling strategy, and engine samples made available to the student for laboratory analysis. The particle size distribution and mineral composition of the samples will be quantified using SEM, EDX and XRD techniques. Laboratory level testing of dust samples in simple rigs will also be undertaken to elucidate specific aspects of the evolution of the ingested test dust during its passage through the engine e.g., the effect of mineral properties on particle fragmentation. The results of the engine test will be compared to data from service engines that have been operating in a limited number of dusty environments with known dust characteristics.
The ultimate goal of the project is to: (i) Use the data produced in the study in a computer model to suggest ways of modifying the engine's operational use to mitigate the damaging effects of sand and dust. (ii) Explore engine design solutions utilising novel chemistry and physical process effects to militate the damage mechanisms.