AXIAL FLOW FAN TEST

1. Object
   1.1 To study the performance characteristics of an axial flow fan.
   1.2 To present the data in dimensionless form and compare with data recorded at different fan
   speeds.
2. Apparatus
   2.1 Keith Blackman Ltd. 405mm diameter Tornado two stage axial flow fan driven by a torque
   reaction variable speed DC electric motor.
   2.2 Damped torque arm force balance.
   2.3 Discharge tube, 405 mm diameter, fitted with adjustable discharge dampers.
   2.4 Pitot tube and manometers set in accordance with:
   BS EN ISO 5801:2017. Fans. Performance testing using standardized airways
   2.5 Tachometers.
   Figure 1: Experimental Apparatus
3. Procedure
   3.1 Record barometric pressure and temperature.
   3.2 Start motor with discharge dampers fully open. Run up to test speed slowly.
   3.3 For reducing damper positions record;
   3.3.1 static heads and velocity heads at the indicated positions,
   3.3.2 motor speed and load
   Balance
   Motor Pitot Tube
   Static Head
   Manometer
   Velocity Head
   Manometer
   Adjustable Dampers
   Fan
   Laboratory: Axial Flow Fan R9 (2021).Docx
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   3.4 Repeat 3.3 at the same constant motor speed for different damper positions from 5 to 0.5 in
   steps of 0.5. It is desirable to take more readings in the stall region due to the irregularities
   in performance as a result of impeller blade stall (indicated by the increase in shaft power
   and the position of the tell-tale thread).
4. Observed Results
   4.1 See attached sheet
5. Theory
   5.1 You must apply the static or dynamic head coefficients to the observed values of static or
   dynamic pressure (in cm H2O) because of the inclination of the manometers used.
   e.g. ℎ??(1) = 0.5 × 4.2???? = 2.1???? and ℎ??(1) = 0.1 × 9.6???? = 0.96????
   5.2 Air density; using barometer reading
   air air
   Hg Hg
   air air
   air
   air R T
   gh
   R T
   P ρ
   ρ = =
   5.3 Average Static Pressure
   s water s
   n
   s s
   p gh
   h
   n
   h
   ~ ~
   ~ 1
   1
   = ρ
   = ∑
   5.4 Velocity at a point in the test section
   air
   waterghu u
   ρ
   2ρ =
   5.5 Average velocity
   = ∑
   n
   u
   n
   u
   1
   ~ 1
   5.6 Average Velocity Pressure
   2
   ~ ~ 2
   u
   p air
   u
   ρ=
   5.7 Total Pressure
   pt ps pu
   ~ ~ = +
   5.8 Air Flow Rate
   Q uA~ =
   5.9 Total Air Power
   ??̇
   ?????? = ??????
   5.10 Shaft Power
   ??̇
   ?????? = ????
   5.11 Fan Total Efficiency
   ?? = ??̇
   ??????
   ??̇
   ??ℎ??????
   Laboratory: Axial Flow Fan R9 (2021).Docx
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   5.12 Non Dimensional Parameters
   It can be shown for a hydraulic turbo machine that:
   ??� ∝ (????)(??)(??)
   Where
   ??� = power coefficient = ??̇
   ?????????? ???? = Reynolds Number = ????????
   ??
   ?? = flow coefficient = ??
   ?????? ?? = head coefficient = ????
   ???????? = ??
   ??????????
   ??̇ = power [??] ?? = density �
   ????
   ????� ?? = speed �
   ??????
   ?? �
   ?? = diameter [??] ?? = flow rate �
   ????
   ?? � ?? = head [??]
   ?? = gravitational acceleration �
   ??
   ????� ?? = dynamic viscosity �
   ????
   ????
   �
   For a given fan running at different speeds in the same fluid then ρ, g,D,µ are constant and the
   characteristic power, flow and head parameters can be compared using:
   ??
   ??
   ??
   ????
   ??̇
   ????
6. Calculated Results
   6.1 See attached sheet for results to process.
   6.2 TAKE GREAT CARE WITH UNITS
7. Graphical Presentation
   7.1 Plot fan total pressure against air flow for each fan speed
   7.2 Plot shaft power against air flow for each fan speed
   7.3 Plot non dimensional characteristics
8. Discussion
   8.1 Discuss the fan characteristics and compare with other similar types of machine.
   8.2 Briefly explain surge and stall and how it affects the fan performance.
   8.3 Comment on the correlation of the test data presented non-dimensionally.
   8.4 Comment on the experimental errors and how they might be reduced.
9. Conclusions
   9.1 Brief statements to satisfy the objectives.
   Laboratory: Axial Flow Fan R9 (2021).Docx
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10. Notes
    10.1 This is a ‘technical report’ submission. These should generally include:-
    • Title Page (include title, author’s name, course and module)
    • Object
    • Observed Results
    • Sample Calculations (show a full sample calculation for one set of data if a series of
    data is calculated)
    • Derived Results (including presentation by results by diagrams, graphs, etc, as
    appropriate)
    • Discussion
    • Conclusions
    • References used

• The original laboratory sheet should be referenced (e.g. ‘see laboratory sheet for
  procedure and theory’)

Sample Solution