Abstract
Abstract The ingestion of airborne particulate into aircraft engines is an undesirable consequence of their operation, particularly in and out of arid locations that leads to reduced time between overhaul. Predicting the maintenance burden in environments rich in airborne particulate is made difficult by the large number of parameters that influence the likelihood of retention of the particles on nozzle guide vanes. In this contribution, we propose a new, reduced-order model that can predict the probability of particle retention as a function of a reduced set of independent variables relating to both the carrier gas flow and particle. Two-dimensional CFD simulations of particle deposition are performed on the General Electric E3 nozzle guide vane using the existing, energy-based fouling of gas turbines (EBFOG) particle deposition model. Results from the model are compared with experimental observations of particle deposition and show good agreement with the mass fraction retained by a vane. We introduce a function that allows the probability of retention to be calculated for a range of engine operating states and architectures by defining a new dimensionless parameter, the generalized thermal Stokes number. This parameter normalizes the thermal response of a particle for all gas and particle softening temperatures allowing the retention probability function to be applied universally. Finally, we demonstrate a practical use of this model by showing its use in calculating the accumulation factor for a particle size distribution.
Highlights
There are several well-documented occurrences of aircraft engine flame-out due to atmospheric dust ingestion
As an alternative to the forms given in Eq (6), the particle thermal Stokes number can be expressed as a ratio of response times, neglecting the Nusselt number or heat transfer coefficient
This work bridges the gap between the two extremes of previous studies—empiricism and high fidelity deterministic computational fluid dynamics (CFD) – by proposing a reduced-order, generalized particle retention model which can be applied for a range of particle types, engine architectures, and operating states
Summary
There are several well-documented occurrences of aircraft engine flame-out due to atmospheric dust ingestion. The dose is defined as the product of the exposure duration and mean dust concentration, giving units of gram seconds per cubic meter. This approach allows calculations of the particle mass flux on the vane to be carried out. Where the rate of mass accumulation is a function of the mean dust concentration at the engine inlet C, the mass flowrate through the engine core Wcore, and the air density at the engine inlet ρf These combined terms are equivalent to the rate at which dust is ingested by the engine and are dependent on the aircraft trajectory and time varying. The final term in this equation is the accumulation factor ζNGV , which is defined as the proportion of ingested dust mass that deposits on a vane
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