Exhaust Emissions Characterization of a Turbocharged 2-Stroke Tier 0+ Locomotive Engine: NOx, PM, SOF and SOF Composition

Abstract

This study presents a detailed exhaust emission characterization of an EMD 2-Stroke turbocharged line haul locomotive diesel engine fitted with an early-development Tier 0+ emissions kit. The objective of this work is to use emissions characterization to gain insight into engine operation and mechanisms of pollutant formation for this family of engine, and identify areas of potential future engine emissions improvement. Results show that at the notches tested (notches 3–8) the largest contributor to PM mass is insolubles (mostly elemental carbon), but that the soluble component of PM, comprising 14–32% of PM, is also significant. GC-FID analysis of the soluble portion shows that it is composed of 55–77% oil-like C22-C30+ hydrocarbons, with the remainder being fuel-like C9-C21 hydrocarbons. The emissions characterization suggests that advancing combustion timing should be effective in reducing PM mass by reducing the insoluble portion (elemental carbon) of PM at all notches. NOx will likely increase, but the current level of NOx is sufficiently below Tier 0+ limits to allow a moderate increase. Reducing engine oil consumption should also reduce PM mass at all notches, although to a smaller degree than measures that reduce the insoluble portion of PM.

Effect of Injection Timing on Combustion, NOx, Particulate Matter and Soluble Organic Fraction Composition in a 2-Stroke Tier 0+ Locomotive Engine

“…Additional details of PM sampling, the dilution tunnel, PM filters, procedures and calibrations are provided in Ref. [12].…”

“…Hedrick [11] presents SOF (soluble organic fraction) measurements from a Tier 0 EMD engine, but do not address the effect of injection timing. A prior study by the authors reports NO^, PM, and PM composition from a Tier 0-1-EMD engine at various notch positions but also does not address injection timing [12]. Markworth et al [13] study how injection timing affects NO^ and PM emissions from two pre-Tier 0 engines, but do not characterize PM composition.…”

“…This work is an extension of the work presented in Ref. [12], which provided a detailed exhaust emission characterization of a 2-stroke turbocharged Tier 0-1-locomotive engine at various notch positions but did not address injection timing.…”

“…Descriptions of the engine and emissions kit are provided in Ref. [12], with explanations of how brake power, brake mean effective pressure (BMEP), fuel fiow, exhaust A/F ratio, and exhaust flow rate are calculated. The engine is fueled with ultra-low sulfur diesel fuel (ULSD) and lubricated with SAE 40 wt.…”

“…Notches 5 and 8 are the notch positions that produce the highest and lowest brake specific PM emissions respectively using the earlyproduction Tier 0+ engine calibration [12].…”