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

Yun, Hanho; Reitz, Rolf D.

doi:10.1115/1.2180812

Cited by 49 publications

(26 citation statements)

References 14 publications

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“…For example, for soot reduction, there are different explanations. O’Connor and Musculus in their review paper [2] categorized these explanations into three main categories, including enhanced mixing effect [6–9], increase temperature effect [10–13] and injection duration effect [14–17]. …”

Section: Introductionmentioning

confidence: 99%

The Effect of Splitting Timing on Mixing in a Jet with Double Injections

Hadadpour

Jangi

Bai

2018

Flow Turbulence Combust

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We present large-eddy simulation (LES) of a high-pressure gas jet that is injecting into a quiescent inert environment. The injection is through a nozzle with a diameter of 1.35 mm. Four injection strategies are considered in which the results of a single continuous injection case are compared with those of double injection cases with different injection splitting timing. In all double injection cases, the injection pulsing interval is kept the same, and the total injected mass is equal to that of the single injection case. On the other hand, the splitting timing is varied to investigate the effects of various injection splitting strategies on the mixture formation and the penetration length of the jet. Results show that the jet penetration length is not so sensitive to the splitting timing whereas the mixing quality can significantly change as a result of shifting the onset of injection splitting toward the end of injection. Especially, it is found that by adopting a post-injection strategy where a single injection splits into the main injection and late small injection near the end of injection period the mixing between the injected gas and ambient air is significantly improved. This trend is not as obvious when the injection splitting timing shifts toward the beginning or even in the middle of injection period. The increase of entrainment in the tail of each injection is one of the underlying physics in the mixing improvement in double injection cases. In addition to that, splitting a single injection into two smaller injections increases the surrounding area of the jet and also stretches it along the axial direction. It can potentially increase the mixing of injected gas with the ambient air.

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Section: Introductionmentioning

confidence: 99%

The Effect of Splitting Timing on Mixing in a Jet with Double Injections

Hadadpour

Jangi

Bai

2018

Flow Turbulence Combust

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“…In general, post injections are less effective at reducing soot at higher loads for a range of injection schedules and intake conditions [18,28,46]. In general, post injections are less effective at reducing soot at higher loads for a range of injection schedules and intake conditions [18,28,46].…”

Section: Introductionmentioning

confidence: 97%

“…The most prevalent explanation is that the post-injection jet enhances mixing of the main-injection mixture with fresh oxygen [13,15,17,20,23,[26][27][28][29], This mixing can have two effects. The most prevalent explanation is that the post-injection jet enhances mixing of the main-injection mixture with fresh oxygen [13,15,17,20,23,[26][27][28][29], This mixing can have two effects.…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies have included load in parametric variations to study post-injection performance [18,19,27,28,30,32,40]. Many of these studies varied load as part of a standard drive cycle, such as the new European drive cycle (NEDC) or the European stationary cycle (ESC) [41,42], In this type of study, operational parameters suchn as load, speed, and boost are typically varied simultane ously in order to simulate various operating conditions representa tive of the drive cycle.…”

Section: Introductionmentioning

confidence: 99%

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

O’Connor

Musculus

2014

Journal of Engineering for Gas Turbines and Power

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A s s is ta n t P ro fe sso r M e c h a n ic a l and N uclear E n g in e e rin g D epartm ent, C enter fo r C o m b u s tio n , P ow er and P ro p u ls io n , P e n nsylva nia State U nive rsity, 111 R esearch East B u ild in g , U n iv e rs ity Park, PA 1 6 8 0 2 e -m a il: jx o 2 2 @ e n g r.p s u .e d u M a rk M usculusT e ch n ica l S taff E n g in e C o m b u s tio n D epartm ent, C o m b u s tio n Research F a cility, S andia N ational Lab o ra to rie s, P.O. B ox 969 , M S 9 05 3 , L iv e rm o re , C A 94551 e -m a il: m p m u s c u @ s a n d ia .g o vThe use o f 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 injec tions, short injections o f 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.

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“…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

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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.

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

Cited by 49 publications

References 14 publications

The Effect of Splitting Timing on Mixing in a Jet with Double Injections

The Effect of Splitting Timing on Mixing in a Jet with Double Injections

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

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

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