Understanding high-pressure gas-liquid interface phenomena in Diesel engines

Dahms, Rainer N.; Manin, Julien; Pickett, Lyle M.; Oefelein, Joseph C.

doi:10.1016/j.proci.2012.06.169

Cited by 122 publications

(71 citation statements)

References 35 publications

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“…The lack of sharpness denotes that the interfacial gradient may not be as steep as in the top sequence. These observations are compatible with the broadening of the interface proposed by Dahms and coworkers [2], and described in the introduction. The disruption of the fluid feature and ostensible mass transfer to the surrounding continue in the subsequent images, with only faint disconnected structures remaining in the last image of this sequence.…”

Section: Resultssupporting

confidence: 93%

“…Such droplets are tracked to observe whether the optical sharpness of the interface and refraction spot remain, indicating classical evaporation, or degrade, suggesting diffusive mixing. As commented in the previous paragraph, the disappearance of the refraction spot and the observed degradation of the droplet boundaries can be associated with interface broadening and surface tension drop, as suggested by the theoretical calculations carried out by Dahms et al [2]. Such modifications in the interface state result in lower intermolecular forces, driving the feature to rapidly lose cohesion and disappear in the ambient when subjected to local turbulence and other aerodynamic forces.…”

Section: Resultsmentioning

confidence: 63%

“…1 Density was measured according to the ASTM D4052 standard method. 2 Kinematic viscosity was measured according to the ASTM D445 standard method. 3 Surface tension for the multi-component fuels was measured via the plate-method [11].…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…Such an issue concerns the multi-phase mixing process under elevated pressures and temperatures. Recent theoretical studies aiming at resolving the interface between the liquid and the ambient gas under diesel-like conditions, as well as the state of the mixture, suggest that the high pressures and temperatures the injected fluid is subjected to may broaden this interface [2,3]. As a result, the surface tension between the two fluids may decrease dramatically to the point that the interface enters the continuum regime.…”

Section: Introductionmentioning

confidence: 99%

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Transcritical mixing of sprays for multi-component fuel mixtures

Manin

Crua

Pickett

2017

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

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The mixing of fuels with oxidizer has been an increasingly interesting area of research with new engine technologies and the need to reduce emissions, while leveraging efficiency. High-efficiency combustion systems such as diesel engines rely on elevated chamber pressures to maximize power density, producing higher output. In such systems, the fuel is injected under liquid state in a chamber filled with pressurized air at high temperatures. Theoretical calculations on the thermodynamics of fuel mixing processes under these conditions suggest that the injected liquid can undergo a transcritical change of state. Our previous experimental efforts in that regard showed through highspeed imaging that spray droplets transition to fluid parcels mixing without notable surface tension forces, supporting a transcritical process. Only mono-component fuels were used in these studies to provide full control over boundary conditions, which prevented extrapolation of the findings to real systems in which multi-component fuels are injected. Multi-component fuels add another layer of complexity, especially when detailed experiments serve model development, requiring the fuels to be well characterized. In this work, we performed high-speed microscopy in the near-field of high-pressure sprays injected into elevated temperature and pressure environments. A reference diesel fuel and several multi-component surrogates were studied and compared to single component fuels. The results support that a transition occurs under certain thermodynamic conditions for all fuels. As anticipated, the transition from classical evaporation to diffusive mixing is affected by ambient conditions, fuel properties, droplet size and velocity, as well as time scales. Analogous to previous observations made with the normal alkane sprays, the behavior of the multi-component fuels correlate well with their bulk critical properties. KeywordsDiesel sprays, Transcritical mixing, Multi-component fuels. IntroductionDespite the growth of alternative technologies for power generation in transportations systems, these technologies only represent a fraction of the worldwide vehicle fleet. Forecasts predict that thermal engines are still going to be highly dominant in decades to come [1]. The same predictions expect a 75 % increase in fuel demand between air, marine and rail transportation, while heavy-duty alone would account for 40 % of the total transportation energy demand. Even with the substantial improvements in gasoline direct-injection and the development of promising new combustion strategies (e.g., homogeneous-charge compression-ignition, spray-guided spark ignition or gasoline compression-ignition), heavy-duty, marine and rail transportation are expected to rely on diesel combustion for years to come. The mixing process between the injected fuel and the oxidizer in diesel engines has been long identified as a key parameter to efficient and clean combustion. Experiments have been devoted to understanding mixing under such conditions, but gaps remain ...

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 63%

Section: Experimental Apparatusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transcritical mixing of sprays for multi-component fuel mixtures

Manin

Crua

Pickett

2017

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

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“…When a fluid parameter reaches and exceeds critical values, the latent heat approaches zero. Dahms et al [15] visualized the structure of n-dodecane jets at conditions of relevance to diesel engines. They noticed that for higher temperature, the transition from liquid to gaseous state appeared to be much smoother than at lowtemperature conditions.…”

Section: Introductionmentioning

confidence: 99%

Autoignition and combustion of n-hexane spray in subcritical and supercritical environments

Kapusta

Pielecha

Wisłocki

et al. 2015

J Therm Anal Calorim

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In this study, processes of a liquid fuel spray ignition and heat release during its combustion were under investigation. The purpose of this study was to elucidate whether the ignition properties and heat release process of a liquid fuel injected into the environments of parameters exceeding its critical values differ from those obtained for subcritical regimes. Therefore, the fuel was injected into the environments of parameters below, around and above its critical values. The ignition and combustion processes were observed by monitoring the pressure in the combustion chamber and by using a high-speed camera through transparent piston. The ignition process was characterized by ignition delay, while the combustion process by heat release and rate of heat release. The ignition delay was determined by pressure rise according to tangential method. Ignition delay determined that way included both physical delay and chemical delay. Obtained results revealed stochastic nature of the spray ignition of n-hexane. No major difference in ignition delay in terms of exceeding critical parameters was noticed. The only parameter directly influencing the ignition delay was the injectant initial temperature.

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Fuels for Engines and the Impact of Fuel Composition on Engine Performance

Mueller

Cannella

Kalghatgi

2014

Encyclopedia of Automotive Engineering

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Fuel is required for an engine to produce work. Reciprocating internal combustion engines are classified by the manner by which this fuel is ignited: spark ignition (SI) or compression ignition (CI). The specific effects of changing a given fuel property depend on many detailed parameters of the engine and combustion strategy in which the fuel is used, as well as the conditions over which the engine is operated. SI engines typically perform better with higher volatility fuels that resist autoignition (gasolines), while conventional CI engines tend to perform better with fuels exhibiting the opposite volatility and autoignition characteristics (diesel fuels). Fuels and engine technologies are currently evolving, however, and as a result, these historical fuel distinctions may become less relevant in the future. As such, it is important to understand how the chemical composition of a fuel determines its operational attributes, including autoignition quality and volatility, as well as many others. This chapter provides a broad overview of topics related to the selection and use of fuels for reciprocating internal combustion engines, including the following: petroleum‐based, alternative, and renewable fuel production techniques; the compositional characteristics of liquid‐ and gas‐phase fuels; key physical and chemical properties of fuels; and the specifications that have been developed to ensure that fuels perform as required in their given applications. The chapter concludes with a brief summary and outlook for the future of fuels for reciprocating internal combustion engines.

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Understanding high-pressure gas-liquid interface phenomena in Diesel engines

Cited by 122 publications

References 35 publications

Transcritical mixing of sprays for multi-component fuel mixtures

Transcritical mixing of sprays for multi-component fuel mixtures

Autoignition and combustion of n-hexane spray in subcritical and supercritical environments

Fuels for Engines and the Impact of Fuel Composition on Engine Performance

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