Reduction in Flow Parameter Resulting From Volcanic Ash Deposition in Engine Representative Cooling Passages

Abstract

Internal cooling passages of turbine blades have long been at risk to blockage through the deposition of sand and dust during fleet service life. The ingestion of high volumes of volcanic ash (VA) therefore poses a real risk to engine operability. An additional difficulty is that the cooling system is frequently impossible to inspect in order to assess the level of deposition. This paper reports results from experiments carried out at typical high pressure (HP) turbine blade metal temperatures (1163 K to 1293 K) and coolant inlet temperatures (800 K to 900 K) in engine scale models of a turbine cooling passage with film-cooling offtakes. Volcanic ash samples from the 2010 Eyjafjallajökull eruption were used for the majority of the experiments conducted. A further ash sample from the Chaiten eruption allowed the effect of changing ash chemical composition to be investigated. The experimental rig allows the metered delivery of volcanic ash through the coolant system at the start of a test. The key metric indicating blockage is the flow parameter (FP), which can be determined over a range of pressure ratios (1.01–1.06) before and after each experiment, with visual inspection used to determine the deposition location. Results from the experiments have determined the threshold metal temperature at which blockage occurs for the ash samples available, and characterize the reduction of flow parameter with changing particle size distribution, blade metal temperature, ash sample composition, film-cooling hole configuration and pressure ratio across the holes. There is qualitative evidence that hole geometry can be manipulated to decrease the likelihood of blockage. A discrete phase computational fluid dynamics (CFD) model implemented in Fluent has allowed the trajectory of the ash particles within the coolant passages to be modeled, and these results are used to help explain the behavior observed.

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

“…Various studies have also examined how the size of ash particles influences likelihood of deposition (Giel et. al.,2016, Taltavull et.al., 2016, Bonilla et.al., 2012, Wylie et. al., 2016.…”

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).…”

Numerical investigation of particle deposition in film-cooled blade leading edge

“…Results showed that at the film-cooling hole exits, the deposition rate decreased with increasing blowing ratio. [14] demonstrated that the film-cooling passage was blocked by external ash particles, which reduced flow parameters significantly. Wang et al [15] numerically studied the effect of different blockage ratios of spherical blockage on film-cooling performance.…”