Abstract
Research and/or Engineering Questions/Objective
The reduction of CO2 emission levels is one of the major concerns of the automotive industry. OEM’s and suppliers are focused on the development of more efficient powertrain solutions and the improvement of the vehicle running resistance. For this purpose, the main innovation of this methodology is the enhanced integration of the expertise and testing capabilities in different engineering functional areas to obtain the vehicle running resistance contributions in an accurate, reliable and effective way.
Methodology
A representative B segment hatchback vehicle was used for the methodology development and demonstration. First, a coast-down sensitivity study was performed on IDIADA proving ground. Real vehicle rotational inertia correction was applied to calculate the actual vehicle running resistance as a baseline. Then, the drivetrain friction losses were measured in IDIADA 4WD chassis dynamometer under representative on-road vehicle conditions. As a result of the measurements, the contributions of the transmission, differential, driveshafts, brake pads and wheel hub were identified. Thirdly, the tyre rolling resistance was accurately disaggregated after performing the characterization of the vehicle-equipped tyres on the coast-down test track by means of IDIADA skid trailer and also on tyre laboratory. Finally, a comprehensive aerodynamic mapping was conducted in the wind tunnel for analysis and correlation purposes.
Results
Results indicated a proper running resistance matching between actual complete vehicle testing and aggregated contributions measurement. This fact confirmed the convenience of the combined methodology for obtaining and balancing the running resistance contributions. The aerodynamic correlation tests in wind tunnel will show the suitability of the methodology for evaluating the aerodynamic drag coefficient variation for different vehicle set-ups through on-road coast-down testing.
Limitations of this study
As the results must be corrected to laboratory conditions, the fact of testing at limit of boundary conditions would yield inaccurate results. Wind conditions are especially sensitive for the coast-down measurement when the purpose of the test is to establish the vehicle baseline so it was ensured that the coast-down measurements were performed at nearly zero wind speed condition. Another limitation is that the methodology may not be able to be extrapolated out to the passenger cars segment. W
hat does the paper offer that is new in the field including the comparison to other work by the authors?
The refined experimental methodology combines IDIADA’s background, know-how and top class facilities in order to allow the performance of the vehicle running resistance split up under a controlled and unique environment quickly and efficiently.
Conclusions
A new combined methodology for the running resistance characterization has been developed. The outcome of the program helps meet the challenging requests from the OEMs because the vehicle improvement proposals for minimizing the vehicle running resistance can be individually identified, weighted and applied in an effective way.
Key words : Running Resistance, Coast-Down; Drivetrain losses; Skid trailer