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The Cooling Airflow of Heavy Trucks - a Parametric Study

The Cooling Airflow of Heavy Trucks - a Parametric Study. Thomas Hällqvist, Scania CV AB. 2008-01-1171. Company Logo. Introduction. Study of the influence on the cooling airflow from various installation parameters on a Heavy duty truck. Analysis performed by means of 3D CFD.

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The Cooling Airflow of Heavy Trucks - a Parametric Study

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  1. The Cooling Airflow of Heavy Trucks - a Parametric Study Thomas Hällqvist, Scania CV AB 2008-01-1171 Company Logo

  2. Introduction • Study of the influence on the cooling airflow from various installation parameters on a Heavy duty truck. • Analysis performed by means of 3D CFD. • The focus of the paper is on the system pressure loss, flow distribution and cooling capacity. 2008-01-1171

  3. Physical Model • Complete 2-axle tractor. • Air enters in the front via mesh screens. • Cooling package includes: • Condensor • Oil cooler • EGR cooler • CAC cooler • Radiator Pictures show the surface mesh 2008-01-1171

  4. Physical Model • Fan diameter of 750 mm (default). • Fan placement depends on engine type. • Both V8 and inline six engines are considered. • High level of details in the engine compartment. Pictures show the surface mesh 2008-01-1171

  5. Simulation Technique • 3D isothermal CFD simulation. • LBM solver by EXA corp. • Coupling to 2D heat exchanger calculation. • Fan modeled via MRF. • Heat exchangers and mesh screens modeled as porous media. 2008-01-1171

  6. Model Size and Accuracy • Statistical convergence within <1 %. • Absolute accuracy within 6 % for massflow (rel. MP). • 40-50·106 volume elements. • Simulated on 128 cpu’s Linux cluster. • Total runtime of approx. 22-30 h. data sampling interval 2008-01-1171 MP: Micro Probe measurements

  7. General Boundary Conditions • Virtual windtunnel with moving ground. • Windspeed of 30 km/h. • Ambient temperature of 25°C. • Fan speed of 1700 rpm. L = 170 m W = 60 m H = 45 m outlet inlet 2008-01-1171

  8. Parameter Variations • Front opening area. • Fan-to-radiator spacing. • Fan-to-engine spacing. • Width of cooling module. • Fan diameter. • Fan projection into shroud. 2008-01-1171

  9. Results • Study of the impact from various parameter settings on: • the flow character, • the total pressure loss, • the flow distribution through the radiator, • the cooling capacity. 2008-01-1171

  10. Results: general flow character • The underhood includes different subsystems. • Subsystems installed in serial or in parallel. • The fan shroud has large influence on the pressure loss. • All subsystems, but the HX’s, must be optimized w.r.t dP. • A HX with large dP generally comes with large heat transfer capacity. Fan shroud Cooling pacakge RAD 2008-01-1171

  11. Results: general flow character • Airflow enters via the front. • Static pressure decreases until the fan, where the pressure is build up to Pamb + dPrear underhood. • Three main flow directions below the cab. • Flow also underneath the engine. 2008-01-1171

  12. Results: general flow character Inline-six setup V8 setup Inline-six setup (S6) V8 setup • V8: fan in high position • S6: fan in low position • Fan placement and engine type influences the flow distribution. • V8: Fan on top of crossmember. • S6: Fan in front of crossmember. • Strong influence on dP below the engine. 2008-01-1171

  13. Results: fan-to-radiator spacing V8 setup Inline-six setup Case REF* • Fan shrouds with different depths tested. • Default setup V8 has a deeper shroud. • dx more critical for S6-cases. • At same depth the V8 setup features higher dPtot than S6. 2008-01-1171

  14. Results: fan-to-radiator spacing V8 setup • dx also influences the flow distribution. • So also the shape of the shroud. • Bad uniformity for RAD  higher dPRAD. 2008-01-1171

  15. Results: fan diameter / width of RAD V8 default case setup 20 % larger fan 20 % wider cooling package uniformity = 0.87 (Case NF) uniformity = 0.88 uniformity = 0.91 • The geometrical shape of the fan shroud influences the flow distribution. • A wide cooler gives low flow rates in the outer regions. • A larger fan improves the uniformity. • A larger fan can geometrically be compared to a deeper fan shroud. 2008-01-1171

  16. Results: fan projection into shroud axial fan behavior leak flows • FPiS determines the flow direction behind the fan. • FPiS should be tuned for each specific installation. • Large FPiS  axial fan behavior, high dP for large engine silhouette. • Small FPiS  radial fan behavior, high rates of leak flows. • The smaller fan-tip to fan-ring spacing the smaller FPiS is possible. 2008-01-1171

  17. Results: cooling performance (1/CC) Influence from massflow Influence from flow uniformity • The flow uniformity has some effect on the cooling performance. • The character of the flow distribution is also relevant. non-uniform flow uniform flow • Within the present interval the cooling performance has a linear relation to the massflow. • The non-uniform and the uniform flow show the same trends. 2008-01-1171

  18. Conclusions • The underhood involves several subsystems. • The design of the fan shroud is crucial. • The flow distribution is important w.r.t. to dP. • For the cooling performance the massflow is of main importance, uniformity of less.

  19. Future Work • Additional parameter settings. • Extend the study w.r.t. fan configuration. • Study the effect from fan modeling. • Extend the thermodynamic analysis.

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