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TECHNICAL PAPERS: Internal Combustion Engines

# An Experimental Investigation on the Effect of Post-Injection Strategies on Combustion and Emissions in the Low-Temperature Diesel Combustion Regime

[+] Author and Article Information
Hanho Yun

Delphi Research Labs, 51786 Shelby Parkway, Shelby Township, MI 48315

Rolf D. Reitz

J. Eng. Gas Turbines Power 129(1), 279-286 (Dec 06, 2005) (8 pages) doi:10.1115/1.2180812 History: Received September 02, 2005; Revised December 06, 2005

## Abstract

In order to meet future emissions regulations, new combustion concepts are being developed. Among them, the development of low-temperature diesel combustion systems has received considerable attention. Low $NOx$ emissions are achieved through minimization of peak temperatures during the combustion process. Concurrently, soot formation is inhibited due to a combination of low combustion temperatures and extensive fuel-air premixing. In this study, the effect of late-cycle mixing enhancement by post-injection strategies on combustion and engine-out emissions in the low-temperature (low soot and $NOx$ emissions) combustion regime was experimentally investigated. The baseline operating condition considered for low-temperature combustion was $1500rpm$, $3bar$ IMEP with 50% EGR rate, and extension to high loads was considered by means of post injection. Post-injection strategies gave very favorable emission results in the low-temperature combustion regime at all loads tested in this study. Since post injection leads to late-cycle mixing improvement, further reductions in soot emissions were achieved without deteriorating the $NOx$ emissions. With smaller fuel injected amounts for the second pulse, better soot emissions were found. However, the determination of the dwell between the injections was found to be very important for the emissions.

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## Figures

Figure 1

Schematic of experimental engine setup

Figure 2

Example control strategy for post injections for the fixed injection energizing time tests

Figure 3

Variations in total fuel mass per injection and the associated IMEP as a function of dwell with fixed energizing time for both injection pulses. (ETp=330μs, ET=150μs)

Figure 4

Rate-of-injection profile with different dwell time (DT) at fixed energizing time (ETp=330μs, ET=150μs)

Figure 5

NOx-soot trade-off with different amount of second injected fuel with 1400μs and 1600μs dwell time, 3bar IMEP (open circle, single injections)

Figure 6

Changes in AHRR with the dwell time between injections

Figure 7

Variations in NOx and soot emissions as a function of dwell

Figure 8

Comparison results of HC emissions with single injection results

Figure 9

Changes in the combustion characteristics with increasing load with single injections

Figure 10

Soot and NOx emissions for the load tests of Fig. 1

Figure 11

Changes in CO emissions with increased load

Figure 12

Changes in cylinder pressure with increased load and post injections (injection pressure 1100bar)

Figure 13

Comparison of emissions between single and post injections for the conditions of Fig. 1 and Table 3 (injection pressure 1100bar for both single and post injections)

Figure 14

AHRR and ROI profile obtained with post injections for the conditions of Fig. 1 (injection pressure 1100bar)

Figure 15

Comparison of combustion characteristics and ROI profile between single and post injection with Pinj=1100bar, Rs=1.83 at 3bar IMEP

## Errata

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