Volcanic ash melting under conditions relevant to ash turbine interactions

Wenjia Song,Ulrich Kueppers,Yan Lavallée,Kai-Uwe Hess,Corrado Cimarelli,Donald B Dingwell

doi:10.1038/ncomms10795

Wenjia Song, Ulrich Kueppers + Show 4 more

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https://doi.org/10.1038/ncomms10795

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Abstract

The ingestion of volcanic ash by jet engines is widely recognized as a potentially fatal hazard for aircraft operation. The high temperatures (1,200–2,000 °C) typical of jet engines exacerbate the impact of ash by provoking its melting and sticking to turbine parts. Estimation of this potential hazard is complicated by the fact that chemical composition, which affects the temperature at which volcanic ash becomes liquid, can vary widely amongst volcanoes. Here, based on experiments, we parameterize ash behaviour and develop a model to predict melting and sticking conditions for its global compositional range. The results of our experiments confirm that the common use of sand or dust proxy is wholly inadequate for the prediction of the behaviour of volcanic ash, leading to overestimates of sticking temperature and thus severe underestimates of the thermal hazard. Our model can be used to assess the deposition probability of volcanic ash in jet engines.

Highlights

The ingestion of volcanic ash by jet engines is widely recognized as a potentially fatal hazard for aircraft operation
To analyse quantitatively the fusion behaviour of volcanic ash at high temperatures, a standard procedure documented by International Organization for Standardization (ISO) was employed
The analysis shows that the average rates of shrinkage (Fig. 5d), fusion (Fig. 5e) and wetting (Fig. 5f) scale linearly with the compositional parameter ratio of basic to acidic major oxides (Rb/a), which supports the conclusion that the viscosity of the bulk material controls the kinetic of volcanic ash melting, sticking and flow in jet engines

Summary

Introduction

The ingestion of volcanic ash by jet engines is widely recognized as a potentially fatal hazard for aircraft operation. The high temperatures (1,200–2,000 °C) typical of jet engines exacerbate the impact of ash by provoking its melting and sticking to turbine parts Estimation of this potential hazard is complicated by the fact that chemical composition, which affects the temperature at which volcanic ash becomes liquid, can vary widely amongst volcanoes. We experimentally constrain the conditions leading to ash deposition onto hot surfaces as a function of bulk chemistry, expressed here as an index of the ratio of basic to acidic major oxides (Rb/a) and heating rate Our findings and their comparison with the fusion characteristics of dust and sand standards, used by the International Organization for Standardization (ISO), reinforce the preliminary conclusion that volcanic ash behaviour cannot be approximated by that of dust or sand particles[21]. Doing so will lead to significant underestimation of the thermal hazards arising from volcanic ash–jet engine interactions and should be avoided

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Conclusion