Effects of Post-Injection Strategies on Near-Injector Over-Lean Mixtures and Unburned Hydrocarbon Emission in a Heavy-Duty Optical Diesel Engine

Chartier, Clément; Andersson, Öivind; Johansson, Bengt; Musculus, Mark P.; Bobba, Mohan K.

doi:10.4271/2011-01-1383

Cited by 33 publications

(28 citation statements)

References 16 publications

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“…In particular, no direct information is obtained from the flow fields within the piston bowl or velocities in the vertical plane. Using a completely transparent bowl, for instance as used by Cosadia et al (2007), Chartier et al (2011) and Petersen and Miles (2011), might further improve the knowledge on the influence of spray injections on the flow fields and therefore the mixing.…”

Section: High-speed Piv Setupmentioning

confidence: 99%

Pre- and post-injection flow characterization in a heavy-duty diesel engine using high-speed PIV

et al. 2012

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High-speed particle image velocimetry (HS-PIV) using hollow microspheres has been applied to characterize the flow in a heavy-duty diesel engine during and after fuel injection. The injection timings were varied in the range representing those used in premixed charge compression ignition (PCCI) regimes, and multiple injections have been applied to investigate their influence on the flow inside the combustion chamber. By injecting into pure nitrogen, combustion is avoided and the flow can be studied long after injection. The results show a sudden change of air motion at the start of injection as a result of the air entrainment at the core of the spray. Furthermore, as expected, spray injection causes a considerable increase in the cycle-to-cycle fluctuations of the flow pattern, the more so for longer injection durations.

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Section: High-speed Piv Setupmentioning

confidence: 99%

Pre- and post-injection flow characterization in a heavy-duty diesel engine using high-speed PIV

et al. 2012

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“…3. Post-injections can (re-)introduce high-temperature reactions in a region near the injector or increase local mixing again, promoting complete oxidation of the soot formed earlier [11]. The scheduling of post-injections is particularly important and seems to be hardware dependent, but reduced engine-out soot levels have been reported, without necessarily compromising on fuel economy [7].…”

Section: Introductionmentioning

confidence: 99%

Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy

Maes

Bakker

Dam

et al. 2017

SAE Int. J. Fuels Lubr.

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Multiple-injection strategies are characterized by a complex and transient interplay between high-and low-temperature reactions. Tracking low-temperature reaction products such as formaldehyde (CH2O) is particularly important to understand ignition phenomena and the so-called "combustion recession" that is observed in experiments. Experimentally, it is often difficult to discriminate between formaldehyde and other species such as poly-aromatic hydrocarbons, which is why a selective excitation approach is used in this work. Simultaneous high-speed imaging of the chemicallyexcited hydroxyl radical (OH*) is used to improve indication of flame location and second stage ignition. During experiments in a constant-volume vessel, two 0.5-ms injections of n-dodecane, separated by 0.5-ms dwell time, are injected into a 900-K ambient. The global flame development is characterized based on high-speed diagnostics, followed by an investigation into the spatial distribution of formaldehyde at four different times after start-of-injection (aSOI). Results show significant influence of the first injection on characteristics of the second. Ignition delay and lift-off location of the second injection are prominently reduced, while flame penetration is greatly enhanced by the wake of the first injection. Formaldehyde structure is observed during both end-of-injection transients, reaching as far upstream as 6 mm from the nozzle. Even after the second injection, the flame structure still appears to be influenced by the first, with a shorter lift-off length and compressed formaldehyde structure. Based on the selective excitation procedure, it becomes clear that the interpretation of laser-induced fluorescence (LIF) images obtained by 355-nm excitation alone is prone to ambiguity.

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“…After first-stage ignition, the evolution of formaldehyde mirrors that of the overall pool of unburned hydrocarbons [14,15] . Formaldehyde does not serve as a good marker for all unburned fuel, such as that from regions that have not achieved first-stage ignition (e.g., wall wetting and crevices), nor does it mark UHC in rich mixtures after second-stage ignition [1,25] . While a small amount of OH is produced during first-stage ignition, its concentration rises by orders of magnitude at second-stage ignition [31] , and hence provides an indication of second-stage ignition, complete combustion, and low local unburned fuel concentration.…”

Section: Optical Engine Diagnosticsmentioning

confidence: 99%

“…Initial studies by Chartier et al [25] , Koci et al [27] , Anselmi et al [26] , and Skeen et al [28] showed promising results for UHC reduction using a post injection at a limited range of conditions. Recent work by O'Connor and Musculus [24] has detailed the sensitivity of UHC reduction by a post injection, termed "post-injection efficacy," to a wide range of injection parameters.…”

Section: Introductionmentioning

confidence: 95%

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Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine

O’Connor

Musculus

Pickett

2016

Combustion and Flame

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a b s t r a c tThis work explores the mechanisms by which a post injection can reduce unburned hydrocarbon (UHC) emissions in heavy-duty diesel engines operating at low-temperature combustion conditions. Post injections, small, close-coupled injections of fuel after the main injection, have been shown to reduce UHC in the authors' previous work. In this work, we analyze optical data from laser-induced fluorescence of both CH 2 O and OH and use chemical reactor modeling to better understand the mechanism by which post injections reduce UHC emissions. The results indicate that post-injection efficacy, or the extent to which a post injection reduces UHC emissions, is a strong function of the cylinder pressure variation during the post injection. However, the data and analysis indicate that the pressure and temperature rise from the post injection combustion cannot solely explain the UHC reduction measured by both engine-out and optical diagnostics. The fluid-mechanic, thermal, and chemical interaction of the post injection with the main-injection mixture is a key part of UHC reduction; the starting action of the post jet and the subsequent entrainment of surrounding gases are likely both important processes in reducing UHC with a post injection.

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Effects of Post-Injection Strategies on Near-Injector Over-Lean Mixtures and Unburned Hydrocarbon Emission in a Heavy-Duty Optical Diesel Engine

Cited by 33 publications

References 16 publications

Pre- and post-injection flow characterization in a heavy-duty diesel engine using high-speed PIV

Pre- and post-injection flow characterization in a heavy-duty diesel engine using high-speed PIV

Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy

Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine

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