Tractor Trailer Drag Reduction Study

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  • Tractor-Trailer Drag Reduction Study Christopher Frasson and Team B.S.E. Aerospace Engineering, Minor Mathematics

    University of Michigan

  • Overview

    Introduction Problem Task Solution

    Air Channeling Devices (ACDs) Computational Fluid Dynamics (CFD) Wind Tunnel Results Conclusion

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  • Problem

    Aerodynamically imperfect tractor-trailer design Over 60% engine power used to overcome drag Optimized for towing power Not fuel efficiency

    5.5 6.5 mpg

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  • Task

    NorthStar Commercial Project Sponsor Real estate company in Grand Rapids, MI

    Scott Nowakowski - Direct Contact Reduce coefficient of drag experienced by tractor-

    trailer

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  • Solution

    Air Channeling Devices (ACDs) Redirect airflow to reduce drag

    Design using CAD and test with CFD Build and test multiple ACDs Determine which combination of ACDs gives

    greatest improvement in drag

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  • Overview

    Introduction Air Channeling Devices (ACDs) Front Flaps Rear Flaps Side Skirts

    Computational Fluid Dynamics (CFD) Wind Tunnel Results Conclusion

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  • Air Channeling Devices (ACDs)

    Front Flaps Rear Flaps Side Skirts

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    Side Skirt

    Front Flaps Rear Flaps

  • Front Flaps

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  • Front Flaps Cont.

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    To back of tractor-trailer

  • Rear Flaps

    Keep flow attached to back end Reduce vortex drag

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  • Rear Flaps Cont.

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  • Rear Flaps Cont. =.52

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  • Side Skirts

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  • Side Skirts Cont.

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  • Overview

    Introduction Air Channeling Devices (ACDs) Computational Fluid Dynamics (CFD) CFD Simulation CFD Results

    Wind Tunnel Results Conclusion

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  • CFD Simulation

    1:10 scale CAD model (Siemens NX 8) Only tested rear flaps and side skirts Computing power and time limitations Meshing issues

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  • CFD Simulation Cont.

    Michigans High Performance Computing Cluster Unstructured Tetrahedral Mesh

    (ANSA) ~15 million cells

    K-omega SST turbulence model (FLUENT 14.5) Best boundary layer resolution

    60 mph free stream velocity 1500 iterations

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  • CFD Results

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    Without ACDs With ACDs

  • Overview

    Introduction Air Channeling Devices (ACDs) Computational Fluid Dynamics (CFD) Wind Tunnel Testing

    Facilities Equipment Calibration Testing Methodology Criteria Rationale Testing Assumptions

    Results Conclusion

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  • Facilities

    University of Michigans 5 x 7 Low Turbulence Subsonic Wind Tunnel Aerospace Machine

    Shop Construction

    Wind Tunnel Building Assembly

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  • Equipment

    1:10 scale tractor-trailer model Ground Plane Wind Tunnel Load Cell Lift, Drag, Side Force, Roll Pitch, Yaw

    Wind Tunnel Data Acquisition Software

    21 5 ft 2.125 in 10.125 in

    1 ft 2.5 in

  • Calibration

    Load Cell Hanging weights

    Data Acquisition Software Coefficient of Drag (CD) = /.52 Values within 1%

    Used tunnel values

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    = Drag Force = = =

  • Testing Methodology

    Reynolds Number matching = /

    = / = / /= ///1= / = /10

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  • Testing Methodology Cont.

    Simulate Highway Speeds - ~650mph wind tunnel Not possible

    Tested at 70, 80, 90 mph 7-10 mph for actual truck

    Trends of CD as a function of Re If CD constant as Re increases Then results represent full scale model

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  • Criteria Rationale

    Effectiveness At least 2% reduction in coefficient of drag

    Feasibility Easily attached/detached ACDs from vehicle ACDs do not limit tractor-trailer functionality

    Profitability Reduce fuel cost by 5% or more

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  • Testing

    Five Configurations No ACDs - Baseline Rear Flaps Side Skirts All ACDs Front and Rear Flaps

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  • Assumptions

    CAD and actual truck model were identical Truck ACDs

    Models represent real tractor-trailers Missing undercarriage components Missing suspension Stationary wheels

    Perfect conditions No sideslip condition or crosswind

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  • Overview

    Introduction Air Channeling Devices (ACDs) Computational Fluid Dynamics (CFD) Wind Tunnel Results Effectiveness Feasibility Profitability Best Configuration Improvements

    Conclusion 28

  • Results

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    Average CD 95% Accuracy Lower Limit Upper Limit

    Baseline .8482 .0038 .8444 .8520

    Side Skirts Only

    .8697 .0048 .8649 .8745

    Rear Flaps Only

    .7733 .0184 .7549 .7917

    Front and Rear Flaps

    .7289 .0021 .7268 .7310

    All ACDs .7819 .0047 .7772 .7866

  • Results Cont.

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  • Effectiveness

    At least 2% reduction in coefficient of drag Baseline: - Side Skirts: 2.53% increase in CD Rear Flaps: 8.83% decrease Front and Rear Flaps: 14.1% decrease All ACDs: 7.82% decrease

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    %= | |/

  • Effectiveness Cont.

    Side skirts fail Manufacturing mistake Flutter

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  • Feasibility

    Easily attached/detached ACDs and ACDs do not hinder functionality Front Flaps: Failed Rear Flaps: Failed Side Skirts: Passed

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  • Profitability

    Reduce fuel costs by 5% or more

    100,000 miles per year 6 miles per gallon $3.81 per gallon of diesel Baseline - $63,500 per year

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  • Profitability Cont. 2:1 correspondence between coefficient of drag

    reduction and fuel economy improvement Baseline: - Side Skirts: 1.27% decrease in fuel efficiency Rear Flaps: 4.42% increase Front and Rear Flaps: 7.05% increase All ACDs: 3.39% increase

    Apply to 6 mpg baseline

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  • Profitability Cont.

    Side Skirts: 1.04% increase in fuel cost Rear Flaps: 4.23% decrease Front and Rear Flaps: 6.59% decrease All ACDs: 3.28% decrease

    Only front and rear flap combination passed

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    %= | |/

  • Best Configuration

    Front and Rear Flaps 14.1% reduction in coefficient of drag 6.59% decrease in fuel cost $4182 savings 6.42 mpg Recommendation

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  • Improvements

    New side skirt design New rear flap design Different angles Only top and bottom or sides

    Front and rear flap maneuverability Take more data Test in larger wind tunnel

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  • Overview

    Introduction Air Channeling Devices (ACDs) Computational Fluid Dynamics (CFD) Wind Tunnel Results Conclusion Current Technology References

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  • Conclusion

    Reduce drag on tractor-trailer by adding ACDs Tested three unique ACDs CFD Wind Tunnel

    Recommend front and rear flaps Significantly reduce drag Increase fuel economy Further testing will yield better results

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  • Current Technology

    ATDynamics TrailerTail 5.5% increase in fuel economy 6 mpg => 6.33 mpg Our rear flap, 6.27 mpg

    Cummins-Peterbilt SuperTruck 10.7 mpg

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  • References

    ATDynamics.com Fundamentals of Aerodynamics John D. Anderson Images.google.com Introduction to the Aerodynamics of Flight, NASA

    SP-367, 1975 Peterbilt.com Simple and Low-Cost Aerodynamic Drag Reduction

    Devices for Tractor-Trailer Trucks Richard M. Wood and Steven X. S. Bauer

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  • Questions

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  • Thanks To

    Team Members Steven Dowding Orion Haro Anton Havrylyuk Charlie Jamieson

    University of Michigan Use of 5 x 7 wind tunnel

    Sponsor NorthStar Commercial

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