An energy based fouling model for gas turbines: EBFOG
File(s)
Accepted version
Author(s)
Casari, N
Pinelli, M
Suman, A
Di Mare, L
Montomoli, F
Type
Journal Article
Abstract
Fouling is a major problem in gas turbines for aeropropulsion
because the formation of aggregates on the wet surfaces
of the machine affects aerodynamic and heat loads.
The representation of fouling in CFD is based on the evaluation
of the sticking probability, i.e. the probability a particle
touching a solid surface has to stick to that surface. Two main
models are currently available in literature for the evaluation of
the sticking coefficient: one is based on a critical threshold for
the viscosity, the other is based on the normal velocity to the
surface. However, both models are application specific and lack
generality.
This work presents an innovative model for the estimation
of the sticking probability. This quantitiy is evaluated by comparing
the kinetic energy of the particle with an activation energy
which describes the state of the particle. The sticking criterion
takes the form of an Arrhenius-type equation. A general formulation
for the sticking coefficient is obtained. The method,
named EBFOG (Energy Based FOulinG), is the first ”energy”
based model presented in the open literature able to account any
common deposition effect in gas turbines.
The EBFOG model is implemented into a Lagrangian tracking
procedure, coupled to a fully three-dimensional CFD solver.
Particles are tracked inside the domain and equations for the momentum
and temperature of each particle are solved. The local
geometry of the blade is modified accordingly to the deposition rate. The mesh is modified and the CFD solver updates the flow
field.
The application of this model to particle deposition in high
pressure turbine vanes is investigated, showing the flexibility of
the proposed methodology. The model is particularly important
in aircraft engines where the effect of fouling for the turbine, in
particular the reduction of the HP nozzle throat area, influences
heavily the performance by reducing the core capacity. The energy
based approach is used to quantify the throat area reduction
rate and estimate the variation in the compressor operating condition.
The compressor operating point as a function of the time
spent operating in a harsh environment can be in this way predicted
to estimate, for example, the time that an engine can fly
in a cloud of volcanic ashes. The impact of fouling on the throat
area of the nozzle is quantified for different conditions.
because the formation of aggregates on the wet surfaces
of the machine affects aerodynamic and heat loads.
The representation of fouling in CFD is based on the evaluation
of the sticking probability, i.e. the probability a particle
touching a solid surface has to stick to that surface. Two main
models are currently available in literature for the evaluation of
the sticking coefficient: one is based on a critical threshold for
the viscosity, the other is based on the normal velocity to the
surface. However, both models are application specific and lack
generality.
This work presents an innovative model for the estimation
of the sticking probability. This quantitiy is evaluated by comparing
the kinetic energy of the particle with an activation energy
which describes the state of the particle. The sticking criterion
takes the form of an Arrhenius-type equation. A general formulation
for the sticking coefficient is obtained. The method,
named EBFOG (Energy Based FOulinG), is the first ”energy”
based model presented in the open literature able to account any
common deposition effect in gas turbines.
The EBFOG model is implemented into a Lagrangian tracking
procedure, coupled to a fully three-dimensional CFD solver.
Particles are tracked inside the domain and equations for the momentum
and temperature of each particle are solved. The local
geometry of the blade is modified accordingly to the deposition rate. The mesh is modified and the CFD solver updates the flow
field.
The application of this model to particle deposition in high
pressure turbine vanes is investigated, showing the flexibility of
the proposed methodology. The model is particularly important
in aircraft engines where the effect of fouling for the turbine, in
particular the reduction of the HP nozzle throat area, influences
heavily the performance by reducing the core capacity. The energy
based approach is used to quantify the throat area reduction
rate and estimate the variation in the compressor operating condition.
The compressor operating point as a function of the time
spent operating in a harsh environment can be in this way predicted
to estimate, for example, the time that an engine can fly
in a cloud of volcanic ashes. The impact of fouling on the throat
area of the nozzle is quantified for different conditions.
Date Issued
2017-02
Date Acceptance
2016-07-20
Citation
Journal of Turbomachinery - Transactions of the ASME, 2017, 139 (2), pp.021002-1-021002-8
ISSN
0889-504X
Publisher
American Society of Mechanical Engineers (ASME)
Start Page
021002-1
End Page
021002-8
Journal / Book Title
Journal of Turbomachinery - Transactions of the ASME
Volume
139
Issue
2
Copyright Statement
© 2017 by ASME
Identifier
https://asmedigitalcollection.asme.org/turbomachinery/article/doi/10.1115/1.4034554/378779/An-EnergyBased-Fouling-Model-for-Gas-Turbines
Subjects
Science & Technology
Technology
Engineering, Mechanical
Engineering
ASH PARTICLES
DEPOSITION
DEGRADATION
TURBULENT
Mechanical Engineering & Transports
0913 Mechanical Engineering
0901 Aerospace Engineering
Publication Status
Published
Article Number
ARTN 021002
Date Publish Online
2016-09-27