Experimental investigation of a turbofan nacelle at different mass flow ratios and angles of attack
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Typ
Examensarbete för masterexamen
Program
Sustainable energy systems (MPSES), MSc
Publicerad
2019
Författare
Dwalibi, Johannes
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The air travel sector is rapidly increasing worldwide motivated by the push for
greater connectivity in an increasingly globalised economy. The turbofan engine is
widely used for aircraft propulsion and it is designed to satisfy the increasing demand
for fuel efficiency. As bypass ratio (BPR) increases, the overall efficiency of
the engine increases which is a main factor that yields lower specific fuel consumption
(SFC). However, high-bypass ratios are accompanied by increased weight and
nacelle drag. Therefore, turbofan nacelles require careful design to balance performance
benefits of the higher propulsive efficiency against weight and drag penalties.
In order to reduce the drag it is necessary to understand how the flow-field around
it behaves at different flight conditions. Therefore, a scale model of a powered turbofan
nacelle was built and tested at the Chalmers low speed wind tunnel. A 3D
axisymmetric nacelle geometry was generated using the class shaped transformation
(CST) method which allows for parametric aerodynamic geometry definitions. Furthermore,
the geometry is imported to a CAD software, where the mechanical design
and assembly modelling were conducted. The model was manufactured, build and
tested in the wind tunnel. Measurements of force, fan speed and static pressure
were carried out for different angles of attack (AoA) and mass flow ratios (MFR).
In addition, surface tufts were used in order to visualise the flow-field, changing
angles of attack (AoA) has been conducted using rotary table and mass flow ratios
(MFR) have been controlled by varying (EDF) rotational speed in accordance with
the wind tunnel air velocity. Results show that the flow around the nacelle body
differs substantially depending on whether the fan is turned on or off, suggesting
that experiments using flow-through nacelles would not be enough for thoroughly
assessing the aerodynamic behaviour of this component. It was also observed that
the higher the (MFR) is, the larger the backward forces are.
Beskrivning
Ämne/nyckelord
CST , Drag , Axisymmetric nacelle , Axisymmetric nacelle , Mass flow ratio , Wind tunnel , Load cell , Measurement , Flow visualisation