Simulation of Volcanic Ash Ingestion Into a Large Aero Engine: Particle–Fan Interactions

Abstract

Volcanic ash (VA) clouds in flight corridors present a significant threat to aircraft operations as VA particles can cause damage to gas turbine engine components that lead to a reduction of engine performance and compromise flight safety. In the last decade, research has mainly focused on processes such as erosion of compressor blades and static components caused by impinging ash particles as well as clogging and/or corrosion effects of soft or molten ash particles on hot section turbine airfoils and components. However, there is a lack of information on how the fan separates ingested VA particles from the core stream flow into the bypass flow and therefore influences the mass concentration inside the engine core section, which is most vulnerable and critical for safety. In this numerical simulation study, we investigated the VA particle–fan interactions and resulting reductions in particle mass concentrations entering the engine core section as a function of particle size, fan rotation rate, and for two different flight altitudes. For this, we used a high-bypass gas-turbine engine design, with representative intake, fan, spinner, and splitter geometries for numerical computational fluid dynamics (CFD) simulations including a Lagrangian particle-tracking algorithm. Our results reveal that particle–fan interactions redirect particles from the core stream flow into the bypass stream tube, which leads to a significant particle mass concentration reduction inside the engine core section. The results also show that the particle–fan interactions increase with increasing fan rotation rates and VA particle size. Depending on ingested VA size distributions, the particle mass inside the engine core flow can be up to 30% reduced compared to the incoming particle mass flow. The presented results enable future calculations of effective core flow exposure or dosages based on simulated or observed atmospheric VA particle size distribution, which is required to quantify engine failure mechanisms after exposure to VA. As an example, we applied our methodology to a recent aircraft encounter during the Mt. Kelud 2014 eruption. Based on ambient VA concentrations simulated with an atmospheric particle dispersion model (FLEXPART), we calculated the effective particle mass concentration inside the core stream flow along the actual flight track and compared it with the whole engine exposure.

Physical and Aerodynamic Characterization of Particle Clusters at Sakurajima Volcano (Japan)

“…The importance of aggregation on ash dispersal is widely recognized by the scientific community also considering the significant hazards posed to aviation, agriculture and public health by ash fallout (Guffanti et al, 2010;Bonadonna et al, 2012;Jenkins et al, 2015). As a result, many efforts have been made to improve the description of aggregates and our understanding of aggregation processes (e.g., Gilbert and Lane, 1994;James et al, 2002;James et al, 2003;Durant et al, 2009;Bonadonna et al, 2011;Rose & Durant, 2011;Taddeucci et al, 2011;Brown et al, 2012;Van Eaton et al, 2012;Van Eaton and Wilson, 2013;Burns et al, 2017;Vogel et al, 2019), as well as to provide increasingly accurate numerical descriptions for more effective hazard assessments (Cornell et al, 1983;Veitch and Woods, 2001;Bonadonna et al, 2002a;Textor et al, 2006;Costa et al, 2010). Despite the importance of aggregation, due to the low preservation potential of particle clusters in tephra-fallout deposits, only a few examples exist that document the fundamental physical and aerodynamic parameters of ash aggregates, such as their bulk density, terminal velocity and size distribution of the constitutive particles (Bonadonna et al, 2002b;Bonadonna et al, 2011;Taddeucci et al, 2011;Van Eaton et al, 2012;Burns et al, 2017;Miwa et al, 2020).…”

A Computationally Efficient Ensemble Filtering Scheme for Quantitative Volcanic Ash Forecasts

“…A commercial aircraft inadvertently flew through the edge of the umbrella cloud while cruising at an altitude of around 36,000 feet during the Kelut eruption at around 13/2220 UTC, and had to make an emergency descent to a lower altitude after crew became alerted of the hazard by the presence of fumes in the cabin and St. Elmo's fire (Kristiansen et al., 2015; Vogel et al., 2019). Inspection of the engines after landing revealed enough damage to its parts to warrant total engine replacement.…”

“…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).…”

A Model for Translation and Rotation Resistance Tensors for Superellipsoidal Particles in Stokes Flow

“…Significant research interest still exists for this approach, as there is a number of applications [9][10][11][12], where the best representation of the particle shape is in fact spherical. On the other hand, it is not uncommon that a reasonable shape specific model does not exist for the actual particle shape and flow regime [13], in which case a spherical drag model can still be used, at least to gain an approximate overview of the observed phenomena. Unlike for the spheres, drag models for non-spherical particles are significantly more complex, not only because of the increased shape formulation effort, but also due to the fact that the particle orientation, with respect to the flow velocity field, needs to be accounted for.…”