Atomization and vaporization for flash-boiling multi-hole sprays with alcohol fuels

Zeng, Wei; Xu, Min; Zhang, Gaoming; Zhang, Yuyin; Cleary, David

doi:10.1016/j.fuel.2011.08.048

Cited by 268 publications

(84 citation statements)

References 21 publications

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“…Experiments showed that the multi-jet spray might collapse to a single-jet spray when flash-boiling occurred by either increasing the fuel temperature or decreasing the ambient pressure [18,20,39]. The EDI injector used in the present study was a six-hole nozzle.…”

Section: Combustion Characteristics With Edi Heating At the Original mentioning

confidence: 99%

Investigation of the effect of heated ethanol fuel on combustion and emissions of an ethanol direct injection plus gasoline port injection (EDI + GPI) engine

Huang

Hong

2016

Energy Conversion and Management

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a b s t r a c tEthanol direct injection plus gasoline port injection (EDI + GPI) is a new technology to utilise ethanol fuel more efficiently and flexibly in spark ignition engines. One issue needs to be addressed in the development of EDI + GPI is the ethanol fuel's low vapour pressure and large latent heat which slow down the ethanol's evaporation and result in the mixture unready for combustion by the time of spark ignition and the consequent increase of CO and HC emissions. Heating the ethanol fuel to be directly injected (EDI heating) has been proposed to address this issue. This paper reports the investigation of the effect of EDI heating on the combustion and emissions of a research engine equipped with EDI + GPI. The results showed that EDI heating effectively reduced the CO and HC emissions of the engine due to the increase of evaporation rate and reduced fuel impingement and local over-cooling. The reduction of CO and HC became more significant with the increase of ethanol ratio. When the temperature of the ethanol fuel was increased by 40°C, the CO and HC were reduced by as much as 43% and 51% respectively in EDI only condition at the original spark timing of 15 CAD BTDC, and 15% and 47% respectively at the minimum spark advance for best torque (MBT) timing of 19 CAD BTDC. On the other hand, the NO emission was slightly increased, but still much smaller than that in GPI only condition due to the strong cooling effect and low combustion temperature of EDI. The IMEP and combustion speed were slightly reduced by EDI heating due to the decrease of injector fuel flow rate and spray collapse of flash-boiling. The largest decrease of IMEP was 5% at the original spark timing and 3% at the MBT timing. Moreover, at the MBT timing, the IMEP increased continuously with the increase of ethanol ratio in the entire range from 0% to 100%. This indicated that the decrease of IMEP in high ethanol ratio conditions at the original spark timing could be avoided by adjusting the spark timing. Therefore EDI heating is effective to address the issues of ethanol's low evaporation rate in low temperature engine environment and over-cooling effect at high ethanol ratio condition in the development of EDI + GPI engine.

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Section: Combustion Characteristics With Edi Heating At the Original mentioning

confidence: 99%

Investigation of the effect of heated ethanol fuel on combustion and emissions of an ethanol direct injection plus gasoline port injection (EDI + GPI) engine

Huang

Hong

2016

Energy Conversion and Management

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“…Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation. Zeng shows this behaviour for an eight-hole injector [5]. For low degrees of superheating, spray width is enhanced and penetration depth decreased.…”

Section: Introductionmentioning

confidence: 74%

Flashboiling atomization in nozzles for GDI engines

Bornschlegel

Conrad

Eichhorn

et al. 2017

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

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Flashboiling denotes the phenomenon of rapid evaporation and atomization at nozzles, which occurs when fluids are injected into ambient pressure below their own vapor pressure. It happens in gasoline direct injection (GDI) engines at low loads, when the cylinder pressure is low during injection due to the closed throttle valve. The fuel temperature at the same time approaches cylinder head coolant temperature due to the longer dwell time of the fuel inside the injector. Flash boiling is mainly beneficial for atomization quality, since it produces small droplet sizes and relative broad and homogenous droplet distributions within the spray. Coherently, the penetration depth normally decreases due to the increased aerodynamic drag. Therefore the thermal properties of injectors are often designed to reach flash boiling conditions as early as possible. At the same time, flash boiling significantly increases the risk of undesired spray collapsing. In this case, neighbouring jets converge and form a single jet. Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation. In order to understand the underlying physics, it is important to study the occurring phenomena flashboiling and jet-to-jet interacting i.e. spray collapsing separately. To this end, single hole injectors are built up to allow for an isolated investigation of flashboiling. The rapid expansion at the nozzle outlet is visualized with a microscopic high speed setup and the forces that lead to the characteristic spray expansion are discussed. Moreover, the results on the macroscopic spray in terms of penetration, cone angles and vapor phase are shown with a high speed Schlieren setup. Resulting droplet diameters and velocities are measured using LDA/PDA. As a result, we find a comprehensive picture of flash boiling. The underlying physics can be described and discussed for the specific case of high pressure injection at engine relevant nozzle geometries and conditions, but independently from neighbouring jets. These findings provide the basis to understand and investigate flashboiling and jet-to-jet interaction as distinct, but interacting subjects rather than a combined phenomenon.

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“…Flash boiling [111] starts occurring at a superheat degree of 1.0, goes through transitional regime when superheat degree is between 1.0 and 0.3, and flare-flash-boiling occurs for superheat degree less than 0.3. It is observed that with ethanol, higher temperatures are required to induce flash boiling [112].…”

Section: Flash-boiling Of Gdi Spraysmentioning

confidence: 99%

A Review on Atomization and Sprays of Biofuels for IC Engine Applications

Boggavarapu

Ravikrishna

2013

International Journal of Spray and Combustion Dynamics

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Ever increasing energy requirements, environmental concerns and energy security needs are strongly influencing engine researchers to consider renewable biofuels as alternatives to fossil fuels. Spray process being important in IC engine combustion, existing literature on various biofuel sprays is reviewed and summarized. Both experimental and computational research findings are reviewed in a detailed manner for compression ignition (CI) engine sprays and briefly for spark ignition (SI) engine sprays. The physics of basic atomization process of sprays from various injectors is included to highlight the most recent research findings followed by discussion highlighting the effect of physico-chemical properties on spray atomization for both biofuels and fossil fuels. Biodiesel sprays are found to penetrate faster and have narrow spray plume angle and larger droplet sizes compared to diesel. Results of analytical and computational models are shown to be useful in shedding light on the actual process of atomization. However, further studies on understanding primary atomization and the effect of fuel properties on primary atomization are required. As far as secondary atomization is concerned, changes in regimes are observed to occur at higher air-jet velocities for biodiesel compared to those of diesel. Evaporating sprays revealed that the liquid length is longer for biodiesel. Pure plant oil sprays with potential use in CI engines may require alternative injector technology due to slower breakup as compared to diesel. Application of ethanol to gasoline engines may be feasible without any modifications to port fuel injection (PFI) engines. More studies are required on the application of alternative fuels to high pressure sprays used in Gasoline Direct Injection (GDI) engines.

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Atomization and vaporization for flash-boiling multi-hole sprays with alcohol fuels

Cited by 268 publications

References 21 publications

Investigation of the effect of heated ethanol fuel on combustion and emissions of an ethanol direct injection plus gasoline port injection (EDI + GPI) engine

Investigation of the effect of heated ethanol fuel on combustion and emissions of an ethanol direct injection plus gasoline port injection (EDI + GPI) engine

Flashboiling atomization in nozzles for GDI engines

A Review on Atomization and Sprays of Biofuels for IC Engine Applications

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