1. Experimental Study of Low-Pressure Automotive Cooling Fan Aerodynamics Under Blocked Conditions N. L. Gifford and E. Savory University of Western Ontario London, Canada R. J. Martinuzzi University of Calgary Calgary, Canada

2. I: Introduction ► Purpose, constraints, need for better designs ► Fan performance is adversely affected by in-situ geometry Hood Ram Airflow Radiator Engine Block Alternator Condenser (A/C) Bumper Fan Module Major Engine Bay Components

3. I: In-Situ Effects ► Air moves by ram and/or fan-induced pressure differentials ► Fan operating point is determined by the vehicle speed and system resistance Ram Flow CharacteristicFan Operating Point

4. I: Low-Pressure Fans ► ‘Low-Pressure’ fans develop more pressure at high flow rates. Wider effective operating range. ► Suitable for truck and high-speed (Autobahn) applications. Performance Curves of LPF and HPF

5. II: Objectives 1. Develop correlations for blocked fan performance 2. Blockage plate effects on fan aerodynamics 3. Aerodynamic difference between HPF and LPF 4. Design constraints for an optimized LPF

6. III: Experimental Details Test Specimens ► Siemens 487mm diameter fan  Airfoil shaped, back-swept blades, brushless DC motor, and a shroud incorporating a labyrinth seal and five structural support arms. Exploded Low-Pressure Fan Assembly

7. III: Blockage Measurements ► Aim:  Quantify blockage induced pressure loss (δΨ) as a function of B ► Apparatus:  AMCA Standard plenum chamber  Circular plate mounted downstream, D b =D f  Performance curves recorded for varying B ► Data Reduction:  Pressure loss is calculated  A quadratic best fit curve is fit to the pressure loss  Coefficients of each curve are plotted as a function of Δ=  Coefficients of each curve are plotted as a function of Δ=B/D f

8. III: Blockage Plate Setup Fan and blockage plate installed in the plenum chamber Blockage Plate Shroud B Flow Direction Plenum Test Nomenclature DbDb D Blockage Plate Fan B Airflow

9. III: Plenum Chamber ► Suction-type AMCA standard plenum chamber AMCA Standard 210-99 Plenum Chamber

10. III: LDV test, In-Situ Test Facility ► Accommodates LDV measurements both upstream and downstream of the fan ► Adjustable to simulate actual vehicle engine bay geometry Diagram of the In-Situ Chamber

11. III: Measurement Location Measurement Location ► 0.006D downstream of the blade trailing edge ► Traversing horizontally across one radius

12. IV: Data Analysis - Performance Curves LPF Performance HPF Performance

13. IV: Pressure Loss HPF Pressure Loss LPF Pressure Loss

14. IV: Pressure Loss vs. D f /B HPF Pressure Loss Coefficients vs. D f /B LPF Pressure Loss Coefficients vs. D f /B

15. IV: Correlation ► A correlation between pressure loss and Δ=B/D f for both fans was developed: ► HPF ► LPF

16. IV: Mean Axial Velocity Plot

17. IV: Mean Radial Velocity Plot

18. IV: Mean Tangential Velocity Plot

19. IV: LDV Analysis ► Axial Velocity:  Energy is redistributed as radial and tangential velocity  LPF tip flow maintained under blockage, allowing higher flow rates ► Radial Velocity:  LPF encourages radial outflow  Alters streamlines over the blade (cylindrical to conical)  May lower airfoil lift

20. IV: Estimated Blade Lift

21. IV: Assumed Upstream Swirl Distribution

22. IV: Resultant Lift Distribution

23. IV: Effective Chord Length

24. Effective Chord Length – LPF

25. IV: Effective Chord Length Normal and Extended Blade Shape DLR2 Airfoil Extended DLR-2 Dimensionless Chord Length 1.01.121.23 Camber Angle (º)18.315.614.5 Percent DifferenceN/A-17.3%-26.2

26. V: Conclusions ► Blockage Correlations  Developed expressions for pressure loss  Pressure loss becomes significant B=1/6D f ► LDV Results:  Increased axial flow at tip due to blockage  Increased radial flow  Tip region produces zero flow without blockage (tip leakage)  Effective chord length leading to reduced camber and inaccurate Re numbers

27. VI: Future Work ► Upstream measurements to confirm blade lift ► Analysis of phase-averaged test results ► Development of an integrated design methodology from these results ► Prototype development and testing with assumption of conical stream surfaces

28. Acknowledgements ► UWO Researchers  Rita Patel ► MESc Candidate  James Kempston ► Undergraduate Student  Graham Hunt ► PhD Candidate  Jason Li ► Former Post Doctoral Researcher ► Siemens VDO Engineering Staff  Brian Havel, Mark Blissett, Paul McLennan ► The Advanced Fluid Mechanics Research Group  www.eng.uwo.ca/research/afm

29. Questions