The accumulation of molten volcanic ash in jet engines; simulating the role of magma composition, ash particle size and thermal barrier coatings

Abstract

As the eruption of Icelandic volcano Eyjafjallojökull demonstrated in 2010, volcanic ash can cause major disruption to commercial aviation. The primary concern is related to the build-up of ash deposits in aircraft gas turbine engines which can critically interfere with the carefully balanced internal flow regime, leading to loss of engine thrust with potentially dire consequences. As a result, limits are placed on the acceptable ash exposure (dose) for commercial aircraft flying in and around eruptive events. The role of ash composition is known to be an important variable but the rate of deposit build-up, the nature of the deposits and how this is affected by interaction with ceramic thermal barrier coatings is not well understood.In this study, volcanic ash samples from seven compositionally diverse volcanoes were heated and deposited onto coated and uncoated Nimonic alloy targets at temperatures matching those of modern engines currently in service. Measurements of the mass and volume of the ash deposits are used to calculate the key parameters that would create a reduction in the flow passage area at the High Pressure Nozzle Guide Vanes (HPNGV). For the realistic range of fine ash sizes tested (median diameter 4 to 40 m, up to a maximum at 125 m), there is a clear trend of increasing deposition rate with increasing particle diameter. After correcting for particle size, there is no clear influence of ash composition on the rate of build-up of deposit in terms of mass. However, an important finding from our study is that ash from more silicic volcanoes forms a relatively low density deposit, with significant vesicularity, implying an increased level of reduction of flow area for a given mass of ash deposit on the HPNGVs. It is also clear that ash remains adhered to ceramic coatings more efficiently than bare metal and we find that low silica ash is the most likely to penetrate in to the thermal barrier coating and the least likely to be dislodged by temperature reduction. Highlights• Ash particle size has a very significant influence on mass deposition rate • Deposits on ceramic Thermal Barrier Coatings do not detach so easily on cooling • High-silica deposits cause more blockage at a given mass dose, due to higher porosity • Low-silica deposits are most likely to remain attached on cooling • We present a method for predicting deposit thickness for given ash exposure scenarios

Sifat Kimia Abu Vulkanis Gunung Sinabung Sebagai Sumber Hara Tanah Dan Analisis Spasial Dari Sebaran Material Hasil Erupsi Tahun 2019

“…Jauhnya jangkauan sebaran abu maupun ketebalan tutupan abu suatu wilayah dipengaruhi oleh kekuatan letusan (Watson et al, 2017), ukuran material (Murniasih et al, 2019), arah dan kecepatan angin serta curah hujan mempengaruhi arah sebaran abu (Wilcox & Coats, 1959). Letusan gunung yang kuat dengan angin kencang dapat menerbangkan abu dan menyelimuti wilayah hingga radius 2.000 km namun dengan endapan yang tipis (Pearson & Brooker, 2020;Rocha-Campos et al, 2011).…”

Monte Carlo Predictions of Aero-Engine Performance Degradation Due to Particle Ingestion

“…Equation ( 10) includes the conversion of the deposit mass to a corresponding volume ( m dep/ρ dep N) distributed across the area of each vane pressure surface A NGV . Understanding the bulk density of the deposit (ρ dep ) is therefore important in accurately determining the deposit volume and depends on the porosity of the deposits, as highlighted by Pearson and Brooker [30].…”

A Computationally Efficient Ensemble Filtering Scheme for Quantitative Volcanic Ash Forecasts

“…Ever since the eruption of the Icelandic volcano Eyjafjallajökull, in 2010, which had a significant impact on airline operations over Europe, there has been increasing interest in quantifying the amounts of ash that aircraft engines might be exposed to during ash encounters (Webster et al., 2012; Witham et al., 2012). There have also been corresponding efforts to better understand the effects of ash on engine performance (Bojdo et al., 2019; Pearson & Brooker, 2020; Song et al., 2019; Vogel et al., 2019) and to quantify the tolerance of engines to different ash dosages (Clarkson et al., 2016; A. J. Prata et al., 2018; A. T. Prata et al., 2019; Wylie et al., 2017). A key finding from these studies is that aircraft engines may be able to tolerate flying through low levels of ash for limited periods without significant deterioration in performance (Clarkson, 2017).…”