Download Ventilation Fan Aeroelastic Analysis

Ventilation Fan Aeroelastic
Analysis

Rotating Fan Stability Analysis.
(Courtesy of FläktWoods AB, Sweden)
LINFLOW 1.4
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Ventilation Fan Modeling in
LINFLOW

Rotating Fan Stability Analysis.
Twin blade fan model:
Rotating at 987 rpm
Inner radius 0.68 m
Outer radius 1.02 m
LINFLOW 1.4
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Steady Flow Analysis of
Rotating Fan
Steady Flow
Absolute Velocity
Contours.
LINFLOW 1.4
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Structural Dynamic Analysis Rotating Fan
Eigenmode table
Egenmod nummer
Structural model included
fan blades + hub.
Stability analysis was
performed using the 8-10
first structural modes
with the lowest natural
frequencies.
LINFLOW 1.4
Frekvens
(Hz )
126.0
332.4
382.7
438.5
554.3
608.9
736.1
804.2
849.3
891.3
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Tabell 1b
Structural model used
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Ventilation Fan Aeroelastic
Stability Analysis
Aeroelastic Eigenfrequency Diagram
Aeroelastic Damping Diagram
One mode showed increasing damping
requirements with increasing load, Which?
LINFLOW 1.4
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Ventilation Fan Stability
Analysis Evaluation
LINFLOW predicted
an unstable 3.rd mode
with a frequency of
382.6 Hz
Unstable Mode Shape
Measurements at full
load later show that a
maximum amplitude of
vibration existed at
389 Hz
LINFLOW 1.4
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Ventilation Fan Experimental
Response Evaluation
Measurements at full load show that a maximum
amplitude of vibration existed at 389 Hz
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2
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Measured frequency response diagram.
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LINFLOW 1.4
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Ventilation Fan Unstable Mode Animation
(Click on Picture for Animation)
LINFLOW 1.4
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New Improved Ventilation
Fan Geometry
Aeroelastic improvements of the fan design
LINFLOW 1.4
Damping requirements for all aeroelastic modes
now drop with increasing loading
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New Ventilation Fan, Experimental Evaluation
Measurements at full load on the aeroelasticly improved design show
more then one order of magnitude lower stress levels on the fan surface.
(Return)
LINFLOW 1.4
Measured frequency response diagram.
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