Impact interaction of in-flight high-energy molten volcanic ash droplets with jet engines
| Autor: | Siddharth Lokachari, Wenjia Song, Donald B. Dingwell, Hongbo Guo, Masahiro Fukumoto, Yan Lavallée, Shanjie Yang, Yancheng You |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
geography geography.geographical_feature_category Materials science Polymers and Plastics Metals and Alloys 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Turbine Electronic Optical and Magnetic Materials Jet engine law.invention Thermal barrier coating Viscosity Volcano law 0103 physical sciences Ceramics and Composites Surface roughness Composite material 0210 nano-technology Thermal spraying Volcanic ash |
| Zdroj: | Acta Materialia |
| ISSN: | 1359-6454 |
| DOI: | 10.1016/j.actamat.2019.04.011 |
| Popis: | The turbine technology incorporated in jet engines is inherently vulnerable to attack by environmental silicate debris. Amongst the various kinds of such debris, volcanic ash is a particular threat as its glass softens to a liquid at temperatures of 500–800 °C, far below jet engine operating temperatures of ∼1500 °C. As a result, ingested re-molten droplets impact and form splats on the protective thermal barrier coatings (TBCs). Investigation of the damage to jet engines ensuing from this process has, to date been restricted to forensic observations after critical encounters. Here, we employ a thermal spray technology to recreate the ‘in-situ’ generation of molten volcanic ash droplets and observe their morphological evolution and interaction with TBCs. The mechanism of splat formation is found to depend both on substrate topography and on in-flight droplet characteristics, whereby splat circularity increases with surface roughness and with the product of the Weber and Reynolds numbers. The experiments reveal that the molten ash droplet adhesion rate is dictated by droplet temperature and viscosity, ash concentration and substrate roughness. A new dimensionless number, S, is developed to quantify the molten ash droplet adhesion rate to both substrate topography and in-flight droplet characteristics. These findings provide a greatly improved basis for the quantification of the hazard potential of volcanic ash to jet engines and should be incorporated into protocols for operational aviation response during volcanic crises. |
| Databáze: | OpenAIRE |
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