Visualization of Ignition Processes in High-Pressure Sprays with Multiple Injections of n-Dodecane

Skeen, Scott A.; Manin, Julien; Pickett, Lyle M.

doi:10.4271/2015-01-0799

Cited by 96 publications

(154 citation statements)

References 41 publications

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“…Added to the complexity of a multi-parameter system, the scheduling of multiple injections has a profound influence on the characteristics of emission formation, and potentially fuel consumption, through the interplay between mixing and combustion [8,9]. An explanation for the largely different optimization schemes and resulting emissions from the previous studies can be found in the aforementioned interaction, combined with the impact of boundary conditions (e.g.…”

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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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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“…Based on the ensemble average, the second injection produces a factor of four times more soot than the first injection under these conditions. As discussed above, this is mainly attributed to the advanced ignition of the second injection, which occurs near the liquid length where the local equivalence ratio is more fuel rich [59]. It is interesting to consider the ratio of the peak total soot mass formed to the total mass of fuel injected for the single (1.5 ms) and multiple injection cases.…”

Section: Spray A: Multiple Injectionsmentioning

confidence: 99%

“…Skeen et al [59] previously investigated the effect of the split injection schedule on mixing and ignition characteristics at the Spray A condition and two lower ambient temperature variants. At the Spray A (900 K ambient) condition, combustion recession occurs following the end of the first injection leaving high-temperature combustion products in the near-nozzle region.…”

Section: Spray A: Multiple Injectionsmentioning

confidence: 99%

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

Skeen

Manin

Pickett

et al. 2016

SAE Int. J. Engines

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The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered

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“…In non-reacting conditions, the spray of the main injection penetrates faster within a shorter dwell time investigated by Mie-scatter and CFD models [8]. When the two-stage injection duration are same, the second injection vapor phase penetration is longer and faster [9][10] [11] [12]. For combustion characteristics, ignition delay of main injection is much shorter than that of the pilot injection and it may be shorter or longer with the dwell time increasing due to the different entrainment of surrounding gas [8].…”

Section: Introductionmentioning

confidence: 99%

Study of the soot quantification for two-stage injection of hydrogenated catalytic biodiesel in a constant-volume combustion chamber

Cao

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The effect of two-stage injection strategies on the soot formation of 0# fossil diesel were investigated experimentally using a constant volume combustion chamber. The ambient conditions was kept constant as injection pressure 150 MPa, ambient gas temperature 900 K, ambient gas pressure 45 bar. A high-speed diffused back-illumination extinction imaging technique was employed to make quantitative measurement on temporal soot evolution and reacting spray liquid length and a direct high-speed camera was used to measure the ignition delay. Two-stage injection strategies were varied with different pilot and main injection time, including a sweep of dwell time in pilotmain injection and pilot injection duration. The results show that the ignition delay decreases with the increasing dwell time. It may result from the entrained surrounding gas enhance the spray combustion process. In the reacting condition, the liquid-phase penetration is slightly longer with the shorter dwell time. However, the pilot injection duration shows slighter impact. The longer dwell time contributes to more total soot mass while the different pilot injection duration barely affect the total soot mass of the main injection. In non-reacting conditions, the spray of the main injection penetrates faster within a shorter dwell time investigated by Mie-scatter and CFD models [8]. When the two-stage injection duration are same, the second injection vapor phase penetration is longer and faster [9][10][11] [12]. For combustion characteristics, ignition delay of main injection is much shorter than that of the pilot injection and it may be shorter or longer with the dwell time increasing due to the different entrainment of surrounding gas [8]. In the multiple injection strategy investigation, the dwell time between injections and the pilot injection duration were seen as the two main factors. Seong-Young Lee et al. [13] found that it exists a slight reduction of the soot mass at the 0.3/0.65/1.2 ms condition. Fang et al. [14]measured the soot production of the biomass to liquid fuel using multiband flame measurement and two-color pyrometry. They found that the pilot injection results in a lower soot level compared with single injection with the same injection quality, while the pilot injection shown little impact on No. 2 diesel soot generation. However, in the study of [15], more fuel quantity during the first injection resulted in less soot emission with no increase in NOx emission when the pilot injection quantity is relative small to the main injection. Coupling the two factors, Carlucci et al. [16] found that both injection timing and duration show similar effect on the soot formation and oxidation. From the discussion before, in conslusion the soot formation in the multiple injection strategy isn't still precisely understanding. In this study, the ignition delay, reacting spray liquid length and total soot mass evolution of 0# fossil diesel were measured in a high-temperature high-pressure constant volume combustion chamber, the objective i...

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Visualization of Ignition Processes in High-Pressure Sprays with Multiple Injections of n-Dodecane

Cited by 96 publications

References 41 publications

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

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

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

Study of the soot quantification for two-stage injection of hydrogenated catalytic biodiesel in a constant-volume combustion chamber

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