Assessing the Impact of Lubricant and Fuel Composition on LSPI and Particulate Emissions in a Turbocharged Gasoline Direct Injection Engine 2020-01-0610
Downsized turbocharged gasoline direct-injection (TGDI) engines with high specific power and torque can enable reduced fuel consumption in passenger vehicles while maintaining or even improving on the performance of larger naturally aspirated engines. However, high specific torque levels can lead to abnormal combustion phenomena such as knock and Low Speed Pre-Ignition (LSPI). LSPI, in particular, can limit further downsizing due to resulting and potentially damaging mega-knock events. Here, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events. Our research shows that oil composition has a strong impact on LSPI frequency and that LSPI frequency can be reduced through a carefully focused approach to lubricant formulation. We observed significant improvement in the maximum BMEP achievable with zero LSPI events using both prototype and market-representative lubricant formulations. Fuels blended with a high polyaromatic content were shown to increase LSPI frequency significantly, and also were shown to produce higher particulate mass (PM) and particulate number (PN) emissions. Fuel ageing also was shown to increase LSPI frequency, which we attribute to the accrual of heavier aromatic and polyaromatic fuel components on the engine’s cylinder wall resulting in a lubricant-fuel mixture that can auto-ignite. In this paper, we discuss the above results along with the use of a high-fidelity test method to measure LSPI under steady-state test conditions.
Abhishek Kar, Andrew Huisjen, Allen Aradi, Jannik Reitz, Asim Iqbal, Karin Haumann, Jennifer Kensler, Ken Hardman, Robert Mainwaring, Sarah Remmert
Shell Global Solutions (US), Inc., FCA US LLC, Shell Global Solutions (Deutschland) GmbH, Shell Global Solutions (UK)