Volcanic ash vs. sand and dust – “to stick or not to stick” in jet engines

Abstract:

Safe air travel activity requires clean flight corridors. But particles scattered in the atmosphere, whether volcanic ash, dust or sand, may present a critical threat to aviation safety. When these foreign particles are ingested into jet engines, whose interiors (e.g., the combustor and turbine blades) reach 1200-2000 °C, they can abrade, melt, and stick to the internal components of the engine, clogging ventilation traps of the cooling system as well as imparting substantial damage and potentially resulting in catastrophic system failure. To date, no criterion predicts ash behaviour at high temperature. Here, we experimentally develop the first quantitative model to predict melting and sticking conditions for the compositional range of volcanic ash encountered worldwide (Fig.1). The assumption that volcanic ash can be approximated by sand or dust is wholly inadequate, leading to an overestimation of sticking temperature and a correspondingly severe underestimation of the thermal hazard. Our findings confirm that the melting/softening behaviour of volcanic ash at high temperatures is essentially controlled by the composition of erupted ash - which may serve as an accurate proxy of the thermal hazard potential of volcanic ash interaction with jet engines. The criterion proposed here successfully parameterizes the potentially complex “melting” process of volcanic ash and can be used to assess the deposition probability of volcanic ash upon ingestion into hot jet engines.