Evaluation of Downsizing and Downspeeding Concepts to Reduce Fuel Consumption of Diesel Engines English

  • Category Technical paper
  • Related event International Congress : SIA Powertrain - Rouen 2014 - 21 & 22 May 2014
  • Edition SIA
  • Date 05/21/2014
  • Author L. de Francqueville, G. De Paola, L. Noel - IFP Energies Nouvelles
  • Language English
  • Type PDF file (1.6 Mo)
    (Downloadable immediately on receipt of online payment)
  • Number of pages 11
  • Code R-2014-02-13
  • Fee from 8.00 € to 10.00 €

The objective of this study is to evaluate the potential of downsizing vs. downspeeding concepts towards reducing fuel consumption of a given vehicle on an NEDC cycle. A dedicated methodology has been set up in order to compare the two concepts, assess the results in terms of emissions, performances and fuel consumption, and finally, to evaluate the impact on the technological requirements on a multi cylinder application.
The aim of downsizing was to reduce the unit displacement from 0.5L to 0.3L, whereas for downspeeding there were two objectives in terms of maximum engine speed over the NEDC cycle: 2250 rpm (medium-downspeeding) and 1750 rpm (highdownspeeding). Starting from a 2.0L, 4 cylinders reference, 7 operating points (OP) were chosen to be as representative as possible over the NEDC cycle. To ensure engine-out raw emissions fulfill Euro 5 regulation, pollutant (HC, CO, NOx and smoke) and noise limits were assigned to each of these 7 OP. The 7-OP reference was used in order to define a new set of OPs corresponding to an isopower application for both the downspeeded- and the downsized-concept. Then the OPs were optimized at the test bench on a single-cylinder engine. A specific methodology was developed for the estimation of the fuel consumption over an NEDC cycle by using both measurements at the test bench on 7 steady-state OPs and a fuel consumption reference map.
Final results and analysis show that fuel consumption on the NEDC cycle can be reduced by ~15% by downsizing, by ~12% by mediumdownspeeding and by ~19% by high-downspeeding. Uncertainty of these estimations being +/-2%, it can be concluded that downsizing and downspeeding could have similar potential for fuel consumption reduction. However, for downsizing, smoke emission did not meet the given limit on 2 high-load OPs, and low-end torque target not achieved. In addition, the downsizing concept requires more advanced (and costly) technology such as two-stage turbocharging, 2500 bar fuel-rail pressure and 180 bar in-cylinder maximum pressure, whereas to achieve the targets for downspeeding only a single turbocharger, 1800 bar fuel pressure and 145 bar incylinder maximum pressure are required.

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