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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Effect of Load on Close-Coupled Post-Injection Efficacy for Soot Reduction in an Optical Heavy-Duty Diesel Research Engine

[+] Author and Article Information
Jacqueline O’Connor

Assistant Professor
Mechanical and Nuclear Engineering Department,
Center for Combustion, Power and Propulsion,
Pennsylvania State University,
111 Research East Building,
University Park, PA 16802
e-mail: jxo22@engr.psu.edu

Mark Musculus

Technical Staff
Engine Combustion Department,
Combustion Research Facility,
Sandia National Laboratories,
P.O. Box 969, MS 9053,
Livermore, CA 94551
e-mail: mpmuscu@sandia.gov

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 14, 2014; final manuscript received March 5, 2014; published online May 2, 2014. Editor: David Wisler. The United States Government retains, and by accepting the article for publication, the publisher acknowledges that the United States Government retains, a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States government purposes.

J. Eng. Gas Turbines Power 136(10), 101509 (May 02, 2014) (16 pages) Paper No: GTP-14-1095; doi: 10.1115/1.4027276 History: Received February 14, 2014; Revised March 05, 2014

The use of close-coupled post injections is an in-cylinder soot-reduction technique that has much promise for high efficiency heavy-duty diesel engines. Close-coupled post injections, short injections of fuel that occur soon after the end of the main fuel injection, have been known to reduce engine-out soot at a wide range of engine operating conditions, including variations in injection timing, exhaust gas recirculation (EGR) level, load, boost, and speed. While many studies have investigated the performance of post injections, the details of the mechanism by which soot is reduced remains unclear. In this study, we have measured the efficacy of post injections over a range of load conditions, at constant speed, boost, and rail pressure, in a heavy-duty optically-accessible research diesel engine. Here, the base load is varied by changing the main-injection duration. Measurements of engine-out soot indicate that not only does the efficacy of a post injection decrease at higher engine loads, but that the range of post-injection durations over which soot reduction is achievable is limited at higher loads. Optical measurements, including the natural luminescence of soot and planar laser-induced incandescence of soot, provide information about the spatiotemporal development of in-cylinder soot through the cycle in cases with and without post-injections. The optical results indicate that the post injection behaves similarly at different loads, but that its relative efficacy decreases due to the increase in soot resulting from longer main-injection durations.

Copyright © 2014 by ASME
Topics: Engines , Stress , Soot , Cylinders
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References

Figures

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Fig. 1

Experimental setup of the single-cylinder optical engine, laser configuration, and dual-camera optical system. The camera field-of-view is shown in the upper right.

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Fig. 5

Engine-out soot for single-injection operation at a variety of DOI1C with 18% O2 and SOI1C = 347 CAD

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Fig. 2

Mass rate-of-injection commands (dotted lines) and profiles (solid lines) over a range of DOI2C with SOI1C = 347 CAD for (a) DOI1C = 1550 μs and SOI2C = 366 CAD, (b) DOI1C = 1950 μs and SOI2C = 366 CAD, and (c) DOI1C = 2350 μs and SOI2C = 368 CAD

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Fig. 3

Apparent heat release rate for three baseline loads, DOI1C = 1550 μs with DOI2C = 500 μs (blue), DOI1C = 1950 μs with DOI2C = 500 μs (red), and DOI1C = 2350 μs with DOI2C = 300 μs (green) for both single (solid line) and main- plus post-injection (circles) schedules at 18% O2 and SOI1C = 347 CAD

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Fig. 4

Engine-out soot for single-injection operation at a variety of DOI1C at four intake-oxygen levels and SOI1C = 347 CAD

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Fig. 6

Ensemble-average soot-NL imaging of single-injection schedules at three loads (columns) and four timings after the end of injection (rows) with 18% O2 and SOI1C = 347 CAD. Crank-angle timing (top) and image intensity scaling (bottom) are in the upper left corner of each image.

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Fig. 7

Instantaneous soot-PLII images of single-injection schedules at three loads (columns) and four timings after the end of injection (rows) with 18% O2 and SOI1C = 347 CAD. The green dot at the left is the injector location and the green line on the right is the bowl wall location. Crank-angle timing is in the upper left corner of each image.

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Fig. 8

Engine-out soot for main- plus post-injection operation at three DOI1C with 18% O2 and SOI1C = 347 CAD

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Fig. 13

Instantaneous soot-PLII images of main- plus post-injection schedules at three loads (columns) and four timings after the end of injection (rows) with 18% O2 and SOI1C = 347 CAD. The green dot at the left is the injector location and the green line on the right is the bowl wall location. Crank-angle timing is in the upper left corner of each image.

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Fig. 9

(a) Percentage, and (b) absolute reduction in engine-out soot compared to a single injection at the same load for main- plus post-injection operation at three DOI1C with 18% O2 and SOI1C = 347 CAD

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Fig. 10

(a) Maximum percentage, and (b) absolute reduction in engine-out soot for a main- plus post-injection schedule compared to a single injection at the same load for three main-injection durations (loads) and four intake-oxygen levels

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Fig. 11

(a) Percentage, and (b) absolute reduction in engine-out soot by main- plus post-injections compared to the main injection without a post for operation at three DOI1C with 18% O2 and SOI1C = 347 CAD

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Fig. 12

Ensemble-average soot-NL imaging of main- plus post-injection schedules of the minimum engine-out soot conditions at three loads (columns) and four timings after the end of injection (rows) with 18% O2 and SOI1C = 347 CAD. Crank-angle timing is in the upper left corner of each image.

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Fig. 14

Measured cylinder pressure for three load conditions with main- plus post-injection schedules. Dotted vertical lines indicate the start and end of the visualization in Fig. 12.

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Fig. 15

Instantaneous soot-NL images of main- plus post-injection schedule at the midsoot condition with 18% O2, SOI1C = 347 CAD, DOI1C = 1950 μs, SOI2C = 366 CAD, and DOI2C = 500 μs. The red outlines indicate the approximate boundary of the post jet and the blue outlines indicate the approximate boundary of one main-injection recirculation zone. Crank-angle timing is in the upper left corner of each image. A video of this condition can be found in Ref. [66].

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Fig. 16

Graphical representations of test matrix options: (a) constant start of injection (CSOI), (b) constant dwell/variable phasing (CDVP), and (c) constant dwell/constant phasing (CDCP)

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Fig. 17

Sensitivity of post-injection efficacy to injection dwell at (a) 21% O2, DOI1C = 1950 μs, (b) 18% O2, DOI1C = 1550 μs, and (c) 12.6% O2, DOI1C = 1550 μs

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