Unthrottled engine operation using variable valve actuation: the impact on the flow field, mixing and combustion

Philip A. Stansfield, Graham Wigley, Colin P. Garner, Rishin Patel, Nicos Ladommatos, Graham Pitcher, Jamie W. G. Turner, Hans Nuglisch, Jerome Helie

Research output: Chapter or section in a book/report/conference proceedingChapter in a published conference proceeding

27 Citations (SciVal)


The effect on the intake flow field, air fuel mixing processes, thermodynamic performance and emissions output has been investigated for a range of valve operating profiles. A standard speed load point of 2000 rpm and 2.7 bar IMEP720° has been reached by throttling the intake whilst running standard cam profiles, by early closing of both inlet valves (EIVC) and by early closing of each inlet individually to generate bulk swirl motions within the cylinder. Data has been recorded at stoichiometric air fuel ratios for both direct injection and port fuelled operation. The valve profiles have been applied to two single cylinder homogeneous gasoline direct injection (GDI) spark ignition engines, developed to investigate the potential of controlling engine load by limiting the inducted air mass using fully variable valve timing (FVVT) to reduce pumping losses at part load. The first engine featured a full length optical liner, allowing 2D Particle Image Velocimetry (PIV) measurements of the intake flow fields to be made, along with Mie imaging studies of the liquid fuel fraction. The second was a thermodynamic engine equipped to measure specific fuel consumption and emissions of CO2, CO, NOX and THC. The work shows that fuel economy benefits can be gained by operating the engine with unthrottled EIVC operation. However, the interaction between the intake air and direct injection fuel spray means performance is highly dependant upon which valve is operated and the timing of the direct injection fuel spray.

Original languageEnglish
Title of host publicationSAE Technical Papers
Publication statusPublished - 1 Dec 2007
EventSAE 2007 World Congress - Detroit, USA United States
Duration: 16 Apr 200719 Apr 2007


ConferenceSAE 2007 World Congress
Country/TerritoryUSA United States


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