Effects of Annular Piston Bowl-Rim Cavity on Soot Emissions of Heavy-Duty Diesel Engine Sandia National Laboratories

Format:

Book

Conference/Event

Author/Creator:

Rajasegar, Rajavasanth, author.

Contributor:

Andersson, Oivind

Li, Zheming

Lind, Ted

Musculus, Mark

Roberts, Greg

Srna, Ales

Conference Name:

SAE WCX Digital Summit (2021-04-13 : Live Online, Pennsylvania, United States)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2021

Summary:

The effect of an annular, piston bowl-rim cavity on soot emissions is studied in a heavy duty, optically accessible, single-cylinder, diesel engine using in-cylinder soot and exhaust smoke emission measurements. The baseline piston configuration consists of a flat bottomed bowl while the cavity-piston configuration has an additional annular cavity that is located below the piston bowl rim and connected to the main-combustion chamber through a thin annular passage, accounting for a 3% increase in the clearance volume, resulting in a reduction in geometric compression ratio (CR) from 11.22 to 10.91. Measurements in the cavity-piston configuration indicate significant reduction in engine-out smoke ranging from 20 60% over a wide range of engine loads compared to the baseline. To understand the effect of geometric CR on smoke emissions, two additional piston configurations with lower CRs namely 10.75 and 10.32, achieved by removing portions of the piston bowl wall are also studied. Results indicate that the cavity-piston configuration still has the lowest engine-out smoke, which confirms that the reduction in the observed smoke emissions is not primarily due to lowering of geometric CR but rather due to an increase in mixing and late-cycle oxidation associated with flows into and out of the cavity. Comparative analysis of apparent heat release rates also indicate a measurable increase in the late-cycle oxidation, immediately following the peak in cylinder pressure for the cavity piston configuration. This is consistent with the timing of when the cavity contents are expected to begin discharging into the piston bowl further supporting the enhanced late-cycle mixing and oxidation hypothesis. Furthermore, to explore the effect of mixing on in cylinder soot, quantitative diffuse back-illuminated (DBI) soot-extinction imaging is used to compute crank angle-resolved, soot optical density (soot-KL) distributions near the piston bowl rim (cavity passage). Averaged late-cycle, soot-KL trends agree with engine-out smoke data, suggesting that the in-cylinder soot-KL within the DBI field of view is representative of soot for the entire combustion chamber, at least late in the cycle. Soot-temperature distribution maps (DBI T), generated from the calculated KL and measured absolute soot-incandescence, intensity data based on aerosol emission theory indicate higher soot temperature (exceeding baseline by 100-200 K), close to the cavity near the time of main chamber pressure reversal, which is also consistent with late-cycle enhanced mixing and oxidation hypothesis

Notes:

Vendor supplied data

Publisher Number:

2021-01-0499

Access Restriction:

Restricted for use by site license