Soot Evolution in Multiple Injection Diesel Flames

Ehleskog, Rickard; Ochoterena, Raul Lima

doi:10.4271/2008-01-2470

Cited by 18 publications

(11 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several studies have presented the explanation that post injections reduce engine-out soot by enhancing mixing within the cylinder [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. Ultimate soot yield depends on a balance between formation and oxidation (discussed in more detail in the following section), and enhanced mixing could conceivably affect formation and/or oxidation.…”

Section: Enhanced Mixingmentioning

confidence: 99%

Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding

O’Connor

Musculus

2013

SAE Int. J. Engines

142

View full text Add to dashboard Cite

This work is a technical review of past research and a synthesis of current understanding of post injections for soot reduction in diesel engines. A post injection, which is a short injection after a longer main injection, is an in-cylinder tool to reduce engine-out soot to meet pollutant emissions standards while maintaining efficiency, and potentially to reduce or eliminate exhaust aftertreatment. A sprawling literature on post injections documents the effects of post injections on engine-out soot with variations in many engine operational parameters. Explanations of how post injections lead to engineout soot reduction vary and are sometimes inconsistent or contradictory, in part because supporting fundamental experimental or modeling data are often not available. In this paper, we review the available data describing the efficacy of post-injections and highlight several candidate in-cylinder mechanisms that may control their efficacy. We first discuss three in-cylinder mechanisms that have been frequently proposed to explain how post injections reduce engine-out soot. Thereafter, to provide a foundation for interpretation of past research, we briefly review basic soot formation and oxidation chemistry, and soot/fluid processes in fuel sprays and engine flows. Next, we provide a comprehensive overview of the literature on the efficacy of post-injections for soot reduction as a function of engine operational parameters including injection duration and dwell, exhaust-gas recirculation, load, boost, speed, swirl, and spray targeting. We conclude by identifying major remaining research questions that need to be addressed to help achieve a design-level understanding of the mechanisms of soot reduction by post injections.

show abstract

Section: Enhanced Mixingmentioning

confidence: 99%

Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding

O’Connor

Musculus

2013

SAE Int. J. Engines

142

View full text Add to dashboard Cite

show abstract

“…In lights of this, the focus of the current study is on the understanding of mechanisms by which a split injection changes the combustion of a diesel spray. The suggested explanations for the effects of split injection in the literature can be categorized into three main mechanims [8]: (i) the split injection enhances the mixing and it reduces the local equivalence ratio and improves premixing before the start of high-temperature combustion [11][12][13][14][15]. In this work, we call this mechanism the equivalence ratio effects, and it will act in favor of reducing the rate of soot formation.…”

Section: Introductionmentioning

confidence: 99%

The role of a split injection strategy in the mixture formation and combustion of diesel spray: A large-eddy simulation

Hadadpour

Jangi

Pang

2019

Proceedings of the Combustion Institute

View full text Add to dashboard Cite

Link to publicationCitation for published version (APA): Hadadpour, A., Jangi, M., Pang, K. M., & Bai, X-S. (2019). The role of a split injection strategy in the mixture formation and combustion of diesel spray: A large-eddy simulation. AbstractThe role of a split injection in the mixture formation and combustion characteristics of a diesel spray in an enginelike condition is investigated. We use large-eddy simulations with finite rate chemistry in order to identify the main controlling mechanism that can potentially improve the mixture quality and reduces the combustion emissions. It is shown that the primary effect of the split injection is the reduction of the mass of the fuel-rich region where soot precursors can form.Furthermore, we investigate the interaction between different injections and explain the effects of the first injection on the mixing and combustion of the second injection. Results show that the penetration of the second injection is faster than that of the first injection. More importantly, it is shown that the ignition delay time of the second injection is much shorter than that of the first injection. This is due to the residual effects of the ignition of the first injection which increases the local temperature and maintains a certain level of combustion some intermediates or radical which in turn boosts the ignition of the second injection.

show abstract

“…Despite many reports on the effects of the multiple-injection strategies, the underlying physics involved in such flow are still not fully understood. In an extensive review, O'Conor et al [3] pointed out a number of remaining research questions, and summarised three main possible effects of multiple-injection: enhanced mixing [7][8][9][10]; increased combustion tempreture [11][12][13][14], and the injection duration effects [1, [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Jet-jet interaction in multiple injections: A large-eddy simulation study

Hadadpour

Jangi

Bai

2018

Fuel

View full text Add to dashboard Cite

This paper reports on studies of multiple-injection strategies of gaseous fuel in a model combustion chamber and the role of jet-jet interactions on the mixing processes in the chamber using large-eddy simulation (LES). A highpressure non-reacting gas flow injected through a jet with a nozzle diameter of 1.35 mm into a quiescent inert air environment is considered. First, we validate the method and our computational setup by comparing the simulation results of a single injection case with available experimental data. It is shown that the transient ensemble-averaged LES results agree well with the experimental measurements. Second, we simulate and compare fourteen injection strategies in order to understand the effect of the main and the post-injections duration, the dwell time and the mass flow rate of post-injection on the mixing, jet penetration, and near-nozzle mixture. The contribution of each injection in the local mixture composition is quantified by solving transport equations for the mixture fraction of each injection.The results show that the turbulence generated in the main injection is enhanced when the post-injection flow into the main injection flow. The increase of the local turbulence intensity is in favor of increasing the scalar dissipation rate and enhancing the mixing rate. However, the penetration of the post-injection flow into the main injection flow and the level of the gas flow from the interaction of two injections depend on the dwell time and the momentum of the post-injection.The results also show that the post-injection modifies the near-nozzle mixture. The comparison of cases with different mass flow rates in the post-injection indicates that the momentum of the post-injection can be optimized either to push away the near-nozzle remaining gas from the main injection and reduce the near-nozzle residue by more than 25% or enrich this fuel-lean region and increase the near-nozzle gasses by more than 43%. These results are very interesting for optimization of the post-injection to reduce engine-out emissions. Highlights• A high-momentum short post-injection reduces the near-nozzle residue gases.• A low-momentum short post-injection enriches the near-nozzle over-lean mixture.• The longer the dwell time, the lower the peak mass of the fuel-rich mixture.• The cases with shorter dwell time and longer post-injection have more significant jet-jet interaction.

show abstract

Soot Evolution in Multiple Injection Diesel Flames

Cited by 18 publications

References 14 publications

Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding

Post Injections for Soot Reduction in Diesel Engines: A Review of Current Understanding

The role of a split injection strategy in the mixture formation and combustion of diesel spray: A large-eddy simulation

Jet-jet interaction in multiple injections: A large-eddy simulation study

Contact Info

Product

Resources

About