Blade Element Momentum Method for a Counter-Rotating Pump-Turbine
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Typ
Examensarbete för masterexamen
Program
Applied mechanics (MPAME), MSc
Publicerad
2021
Författare
Ibanez Uribe, Cristobal
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Blade Element Momentum (BEM) methods are widely used for initial aerodynamic
analysis of wind and tidal turbines, as well as aircraft and marine propellers. Mainly
because they use less computational resources and can give fairly accurate results.
This thesis studies the applicability of such method for load prediction on the runner
blades of a model scale axial shaft-driven Counter-Rotating Pump-Turbine (CRPT).
One of the main assumptions and modifications adopted in the BEM method was
to omit the axial induction factor, a ,and let the axial velocity be constant. This
considering that the volumetric flow rate, q, and cross-sectional area, A, must remain
unchanged throughout the turbomachine. Additionally, an attempt to include the
constant pressure difference across the rotors as extra loading being exerted on the
blade, as well as a suggestion on how to apply the BEM method on the downstream
rotor are presented and evaluated.
The data needed to implement the BEM method is created by running several
CFD simulations using OpenFOAM. These simulations produce 2D aerodynamic
airfoil-like characteristics of lift and drag coefficients, Cl and Cd, at different angles
of attack (AoA) and Re numbers in both pump and turbine mode for different
blade profiles along the radial direction. Furthermore, validation cases at different
operating conditions are also simulated with OpenFOAM assuming steady-state
flow. This is done for different geometries. One of them considers the turbomachine
with both runners operating simultaneously and the other geometries isolate each
runner individually.
It is concluded that it is possible to use the BEM method with a reasonable amount
of error for certain operating conditions. Most importantly the behaviour of the
dimensionless thrust and power coefficients, CT and CP at different tip speed ratios,
T SR, tends to follow the same trend as CFD. Further work needs to be done in
order to fully validate such a method for this type of turbomachine.
Beskrivning
Ämne/nyckelord
BEM, CFD, Counter-Rotating, Pump-Turbine, Hydro-power, Open-FOAM