Influence of Injection Duration and Ambient Temperature on the Ignition Delay in a 2.34L Optical Diesel Engine

Malbec, Louis-Marie; Eagle, W. Ethan; Musculus, Mark P.; Schihl, Peter

doi:10.4271/2015-01-1830

Cited by 20 publications

(13 citation statements)

References 49 publications

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“…Under such thermal condition (870 K, 22.8 kg/m 3 ), the end of the first injection pulse may occur before (D250, D750 and F500 cases) or after (F750 and Single_1500 cases) ID. Therefore, injection duration does not seem to have an impact on the ID of the first injection, ID1, consistently with previous work, 46 which shows that this parameter was not influenced by EOI at temperatures of 850 and 900 K. A similar behavior is observed for the measured LOL of the first injection pulse, that is, it does not depend on the injection pattern, even though injection pulse may be shorter than the auto-ignition timing.…”

Section: Resultssupporting

confidence: 90%

Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

Desantes

García-Oliver

García

et al. 2018

International Journal of Engine Research

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Even though studies on split-injection strategies have been published in recent years, there are still many remaining questions about how the first injection affects the mixing and combustion processes of the second one by changing the dwell time between both injection events or by the first injection quantity. In this article, split-injection diesel sprays with different injection strategies are investigated. Visualization of n-dodecane sprays was carried out under both non-reacting and reacting operating conditions in an optically accessible two-stroke engine equipped with a single-hole diesel injector. High-speed Schlieren imaging was applied to visualize the spray geometry development, while diffused background-illumination extinction imaging was applied to quantify the instantaneous soot production (net result of soot formation and oxidation). For non-reacting conditions, it was found that the vapor phase of second injection penetrates faster with a shorter dwell time and independently of the duration of the first injection. This could be explained in terms of one-dimensional spray model results, which provided information on the local mixing and momentum state within the flow. Under reacting conditions, interaction between the second injection and combustion recession of the first injection is observed, resulting in shorter ignition delay and lift-off compared to the first injection. However, soot production behaves differently with different injection strategies. The maximum instantaneous soot mass produced by the second injection increases with a shorter dwell time and with longer first injection duration.

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Section: Resultssupporting

confidence: 90%

Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

Desantes

García-Oliver

García

et al. 2018

International Journal of Engine Research

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“…The ignition process in dual-fuel engines shows a higher complexity than in conventional Diesel engines: besides the chemistry being affected by the methane content of the charge, furthermore, the equivalence ratio and temperature history of fuel parcels are influenced by end-ofinjection-transients and overmixing phenomena, since the injection duration is usually shorter than the ignition delay. During the end of injection transient for short ignition dwell times ignition is accelerated, except in the case of too long ignition dwell when it decelerates due to overmixing [24,25,26,27]. Only by a modification of [28] for this methane influence and the end-of-injection transient Barro et al [27] were able to develop a dual-fuel combustion HRR model with predicting capabilities over a wide range of operating conditions.…”

mentioning

confidence: 99%

POMDME as an Alternative Pilot Fuel for Dual-Fuel Engines: Optical Study in a RCEM and Application in an Automotive Size Dual-Fuel Diesel Engine

Srna

Barro

Herrmann³

et al. 2018

SAE Technical Paper Series

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D ual-fuel natural gas engines are seen as an attractive solution for simultaneous reduction of pollutant and CO 2 emissions while maintaining high engine thermal efficiency. However, engines of this type exhibit a tradeoff between misfire as well as high UHC emissions for small pilot injection amounts and higher emissions of soot and NO X for operation strategies with higher pilot fuel proportion. The aim of this study was to investigate POMDME as an alternative pilot fuel having the potential to mitigate the emissions tradeoff, enabling smokeless combustion due to high degree of oxygenation, and being less prone to misfire due to its higher cetane number. Furthermore, POMDME can be synthetized carbon neutrally. First, characteristics of POMDME ignition in methane/ air mixture and the transition into premixed flame propagation were investigated optically in a rapid compression-expansion machine (RCEM) by employing Schlieren and OH* chemiluminescence imaging. A single-hole coaxial injector mounted at the cylinder periphery was used to admit POMDME or n-dodecane as the reference pilot fuel. In the second stage, POMDME was applied as a pilot-fuel in a VW 2 l 4-cylinder industrial Diesel engine modified for dual-fuel operation. Engine performance with POMDME and EN590 Diesel pilot-fuels was compared. In the RCEM, in air, dodecane and POMDME exhibit similar ignition delay times. In methane/air mixtures, ignition of both pilot fuels was deferred with increasing methane content, with stronger influence on POMDME than on dodecane. Indication of pilot-fuel over-mixing was observed for the shortest considered POMDME injections. In the engine experiment, while keeping the total combustion equivalence ratio constant, POMDME was found to have shorter ignition delays than Diesel fuel, attributed to its higher cetane number. At constant engine load using POMDME instead of Diesel pilot fuel, stable operation with lower pilot-fuel energy and mass input was possible along with soot mass reduction to close to zero.

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“…The start of secondstage combustion is calculated from the zero-crossing of the apparent heat release rate (AHRR) after first-stage heat release. Recent experiments in this engine [35] have shown that the zero-crossing of the AHRR profile correlates very well with the first appearance of high-temperature chemiluminescence emission, indicating that AHRR is a good metric for ignition. The start of injection, when fuel starts to emerge from the injector orifices, is measured using high-speed video of Mie-scattering from the liquid jets.…”

Section: Single-injection Experimental Resultsmentioning

confidence: 94%

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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Influence of Injection Duration and Ambient Temperature on the Ignition Delay in a 2.34L Optical Diesel Engine

Cited by 20 publications

References 49 publications

Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

Optical study on characteristics of non-reacting and reacting diesel spray with different strategies of split injection

POMDME as an Alternative Pilot Fuel for Dual-Fuel Engines: Optical Study in a RCEM and Application in an Automotive Size Dual-Fuel Diesel Engine

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

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