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

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

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

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

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

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

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

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

III: Plenum Chamber ► Suction-type AMCA standard plenum chamber AMCA Standard Plenum Chamber

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

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

IV: Data Analysis - Performance Curves LPF Performance HPF Performance

IV: Pressure Loss HPF Pressure Loss LPF Pressure Loss

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

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

IV: Mean Axial Velocity Plot

IV: Mean Radial Velocity Plot

IV: Mean Tangential Velocity Plot

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

IV: Estimated Blade Lift

IV: Assumed Upstream Swirl Distribution

IV: Resultant Lift Distribution

IV: Effective Chord Length

Effective Chord Length – LPF

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

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

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

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 

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