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Research Papers: Internal Combustion Engines

Exhaust-Stream and In-Cylinder Measurements and Analysis of the Soot Emissions From a Common Rail Diesel Engine Using Two Fuels

[+] Author and Article Information
Patrick Kirchen1

ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzlerandpkirchen@mit.edu

Peter Obrecht

ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzlerandobrecht@lav.mavt.ethz.ch

Konstantinos Boulouchos

ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzlerandboulouchos@lav.mavt.ethz.ch

Andrea Bertola

Kistler Instruments AG, CH-8408 Winterthur, Switzerlandandrea.bertola@kistler.com

Because of the empirical nature of this correlation, it should be noted that the wavelength is considered in units of micrometer.

1

Corresponding author. Present address: Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139.

J. Eng. Gas Turbines Power 132(11), 112804 (Aug 16, 2010) (8 pages) doi:10.1115/1.4001083 History: Received October 12, 2009; Revised December 10, 2009; Published August 16, 2010; Online August 16, 2010

Abstract

The operation and emissions of a four cylinder, passenger car common-rail diesel engine operating with two different fuels was investigated on the basis of exhaust-stream and in-cylinder soot measurements, as well as a thermodynamic analysis of the combustion process. The two fuels considered were a standard diesel fuel and a synthetic diesel (fuel two) with a lower aromatic content, evaporation temperature, and cetane number than the standard diesel. The exhaust-stream soot emissions, measured using a filter smoke number system, as well as a photo-acoustic soot sensor (AVL Micro Soot Sensor), were lower with the second fuel throughout the entire engine operating map. To elucidate the cause of the reduced exhaust-stream soot emissions, the in-cylinder soot temperature and the $KL$ factor (proportional to concentration) were measured using miniature, three-color pyrometers mounted in the glow plug bores. Using the maximum $KL$ factor value to quantify the soot formation process, it was seen that for all operating points, less soot was formed in the combustion chamber using the second fuel. The oxidation of the soot, however, was not strongly influenced by the fuel, as the relative oxidized soot fraction was not significantly different for the two fuels. The reduced soot formation of fuel two was attributed to the lower aromatic content of the fuel. The soot cloud temperatures for operation with the two fuels were not seen differ significantly. Similar correlations between the cylinder-out soot emissions, characterized using the pyrometers, and the exhaust-stream soot emissions were seen for both fuels. The combustion process itself was only seen to differ between the two fuels to a much lesser degree than the soot formation process. The predominant differences were seen as higher maximum fuel conversion rates during premixed combustion at several operating points, when fuel two was used. This was attributed to the lower evaporation temperatures and longer ignition delays (characterized by the lower cetane number) leading to larger premixed combustion fractions.

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Figures

Figure 1

Schematic representation of the fundamental soot formation mechanisms during combustion. Adapted from Refs. 9-12.

Figure 2

Overview of instrumentation used on the OM611 engine

Figure 3

Schematic of the three-color pyrometry system implemented in this investigation

Figure 4

Representative KL factor history for diesel combustion and characteristic parameters for soot formation KLmax, oxidation γox, and cylinder-out soot emissions KLend

Figure 5

Exhaust-stream soot emission maps measured using the AVL Micro Soot Sensor for operation with both fuels. NOTE: Different scales used for each fuel.

Figure 6

Soot emissions measured using the AVL Micro Soot Sensor and FSN for operation with two fuels. The empirical correlation between FSN and soot concentration (26) is shown for reference purposes.

Figure 7

Correlations between FSN and KLend for both fuels; KLend values are based on cylinder 3 measurements

Figure 8

Operating point specific comparisons of KLmax (a) and γox (b) for operation with both fuels; cylinder 3

Figure 9

Mean relative difference in exhaust-stream soot emissions (MSS and FSN) and pyrometry based parameters (KLend, KLmax, and γox) for operation with the reference fuel and fuel two. Solid bars indicate the mean relative difference over all considered operating points while error bars indicate the standard deviation. KL parameters are taken from cylinder 3.

Figure 10

KL factor and fuel conversion rate histories for operation with the reference fuel and fuel two. See Table 4 for details of each operating point.

Figure 11

KL factor and fuel conversion rate histories for operation with the reference fuel and fuel two. See Table 4 for details of each operating point.

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