Abstract
Since multi-mode engine combustion strategies are being investigated as a pathway to increased vehicle fuel efficiency, a better understanding of particulate matter formation during the advanced compression ignition (ACI) modes and the resulting PM properties are of growing importance for mitigating PM emissions and/or developing emissions control strategies. ACI combustion strategies have demonstrated extremely low engine-out soot while achieving high break thermal efficiencies. However, US-regulated emissions for particulate matter (PM) are on a mass basis, which can consist of ash, soot or elemental carbon (EC), and organic carbon (OC). The composition of PM mass from ACI combustion ranges from nearly 100% OC to a mix of EC and OC particulates as the extent of fuel stratification increases. How the mass, compositions, and morphology of PM changes as fuel stratifies within the combustion chamber and what this can tell us about PM formation are presented through multi-cylinder, metal engine experiments. Using ACI modes ranging from homogeneous to highly stratified approaches, this study aimed to advance the understanding of how air-fuel stratification and fuel properties impact PM emissions formation; advanced gaseous and solid emission characterizations are also given. This study is part of a collaborative multi-lab initiative at the US Department of Energy that aims to simultaneously transform both transportation fuels and vehicles in order to maximize performance and energy efficiency, minimize environmental impact, and accelerate widespread adoption of innovative combustion strategies by providing the underlying science for this initiative.
Highlights
This manuscript has been authored by UT-Battelle, LLC under Contract No DE-AC05-00OR22725 with the US Department of Energy
A heated chemiluminescence analyzer (CLD) was used to measure total NOx emissions (NO + NO2). Both CO and CO2 were measured with non-dispersive infrared (NDIR) instruments: CO was measured in the exhaust with a dedicated instrument with simultaneous high and low ranges, and CO2 was measured in both the exhaust and intake with separate instruments
The NOx and CO emissions were measured with an FTIR, and total unburned hydrocarbons (THC) emissions were measured with a flame ionization detector (FID)
Summary
The US Department of Energy’s (DOE) Co-Optimization of Fuels and Engines (Co-Optima) initiative [1] is working to advance the underlying science needed to develop fuel and engine technologies that will work in tandem to achieve significant efficiency gains As part of this line of investigation, understanding the emissions from advanced compression ignition modes (ACI), which may be part of a light-duty multimode strategy or for either multi-mode or full-time medium-/ heavy-duty next-generation engines, are of importance. This current work investigated the bookends of ACI to understand the impacts that occur from increasing the amount of air-fuel stratification when using gasoline-like fuels. This study is a first step in understanding both of these effects on PM and gaseous emissions
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