Effects of Injector Nozzle Inclusion Angle on Extending the Lower Load Limit of Gasoline Compression Ignition Using 87 AKI Gasoline

Abstract

Gasoline Compression Ignition (GCI) is a promising single-fuel advanced combustion concept for increased efficiency and reduced emissions in comparison with current conventional combustion modes. Gasoline fuels are advantageous in premixed combustion concepts because of their increased volatility and reduced reactivity compared to diesel. These qualities help reduce emissions of particulate matter (PM) and oxides of nitrogen (NOx), while making combustion phasing (and therefore combustion noise reduction) easier to manage. One of the challenges of using a gasoline with an anti-knock index (AKI) of 87 in a premixed combustion concept is being able to achieve stable low load operation. (Note that AKI is equivalent to (RON + MON)/2.) With such small injection quantities of a relatively more volatile and less reactive fuel than diesel, the injection timing of minimum load fueling needs to be early enough to allow the auto-ignition chemistry enough time, but late enough to keep the fuel from over-mixing and losing ignition propensity. The objective of this study was to investigate the advantages and disadvantages of reducing the injector nozzles’ inclusion angle from 148° to 120° on the combustion and emissions performance of GCI at 850 RPM and low load. To assess these effects, minimum fueling injection timing sweeps were performed with a 3% coefficient of variance of indicated mean effective pressure with each injector nozzle angle at 500 and 250 bar injection pressure. The results from these experiments revealed that both reduced injector nozzle angle and reduced injection pressure increased ignition propensity and allowed for reduced fueling and stable low load extension to 1 bar brake mean effective pressure using 87 AKI gasoline without any external boosting or heating. Combustion characteristics (such as noise) and emissions are discussed.