Gasoline compression ignition (GCI) is widely studied for the benefits of simultaneous reduction in nitrogen oxide (NOX) 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 is operated at homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) combustion modes. In the presented work, the engine is equipped with variable valve cam phasers that can phase both inlet and exhaust valves from the original timing. With exhaust cam phasing adjustment, the exhaust valve is closed early to retain hot residual gases inside cylinder. As such, the in-cylinder temperature is increased and a reduction in the required intake air temperature to control combustion phasing is noted. A 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.
Abdullah received his B.Eng. degree in Mechanical Engineering on August 2013 from University College London, United Kingdom. He recently received his Master's degree in Mechanical Engineering at KAUST in December 2017. He started his PhD at KAUST under the Clean Combustion Research Center in January 2018 with a research focus on internal combustion engines and fuel design and applications.