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    Low Load Limit Extension for Gasoline Compression Ignition Using Negative Valve Overlap Strategy

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    Type
    Conference Paper
    Authors
    Vallinayagam, R.
    AlRamadan, Abdullah
    Vedharaj, S
    An, Yanzhao cc
    Sim, Jaeheon cc
    Chang, Junseok
    Johansson, Bengt cc
    KAUST Department
    Clean Combustion Research Center
    Mechanical Engineering Program
    Physical Science and Engineering (PSE) Division
    Date
    2018-04-03
    Permanent link to this record
    http://hdl.handle.net/10754/627854
    
    Metadata
    Show full item record
    Abstract
    Gasoline compression ignition (GCI) is widely studied for the benefits of simultaneous reduction in nitrogen oxide (NO) and soot emissions without compromising the engine efficiency. Despite this advantage, the operational range for GCI is not widely expanded, as the auto-ignition of fuel at low load condition is difficult. The present study aims to extend the low load operational limit for GCI using negative valve overlap (NVO) strategy. The engine used for the current experimentation is a single cylinder diesel engine that runs at an idle speed of 800 rpm with a compression ratio of 17.3. The engine is operated at homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) combustion modes with the corresponding start of injection (SOI) at 180 CAD (aTDC) and 30 CAD (aTDC), respectively. In the presented work, intake air temperature is used as control parameter to maintain combustion stability at idle and low load condition, while the intake air pressure is maintained at 1 bar (ambient). The engine is equipped with variable valve cam phasers that can phase both inlet and exhaust valves from the original timing. For the maximum cam phasing range (56 CAD) at a valve lift of 0.3 mm, the maximum allowable positive valve overlap was 20 CAD. In the present study, the exhaust cam is phased to 26 CAD and 6 CAD and the corresponding NVO is noted to be 10 CAD and 30 CAD, respectively. With exhaust cam phasing adjustment, the exhaust valve is closed early to retain hot residual gases inside the cylinder. As such, the in-cylinder temperature is increased and a reduction in the required intake air temperature to control combustion phasing is possible. For a constant combustion phasing of 3 CAD (aTDC), a minimum load of indicated mean effective pressure (IMEP) = 1 bar is attained for gasoline (RON = 91) at HCCI and PPC modes. The coefficient of variance was observed to below 5% at these idle and low load conditions. At the minimum load point, the intake air temperature required dropped by 20°C and 15°C for NVO = 30 CAD at HCCI and PPC modes, respectively, when compared to NVO = 20 CAD and NVO = 10 CAD. Similarly, for the load range of IMEP = 1 to 3 bar, decrease in temperature requirement is noted for negative valve overlap cases and the translational table in terms of d (Tin)/d (NVO) is attained. However, the low load limit was extended with negative valve overlap at the expense of decreased net indicated thermal efficiency due to heat losses and reduction in gas exchange efficiency. Ultra low soot concentration and NO emission were noted at HCCI condition.
    Citation
    Vallinayagam R, AlRamadan AS, Vedharaj S, An Y, Sim J, et al. (2018) Low Load Limit Extension for Gasoline Compression Ignition Using Negative Valve Overlap Strategy. SAE Technical Paper Series. Available: http://dx.doi.org/10.4271/2018-01-0896.
    Sponsors
    This work was funded by competitive research funding from King Abdullah University of Science and Technology (KAUST) under the Clean Combustion Research Center’s research program. We also acknowledge funding from KAUST and Saudi Aramco under the FUELCOM program. Finally, we would like to express our gratitude to our research Technician, Adrian. I. Ichim for his support in carrying out the experiments at KAUST engine lab.
    Publisher
    SAE International
    Journal
    SAE Technical Paper Series
    Conference/Event name
    2018 SAE World Congress Experience, WCX 2018
    DOI
    10.4271/2018-01-0896
    Additional Links
    https://saemobilus.sae.org/content/2018-01-0896
    ae974a485f413a2113503eed53cd6c53
    10.4271/2018-01-0896
    Scopus Count
    Collections
    Conference Papers; Physical Science and Engineering (PSE) Division; Mechanical Engineering Program; Clean Combustion Research Center

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