Characterization of Fuel Vapor Concentration Inside a Flash Boiling Spray

Adachi, Masayuki; McDonell, Vincent; Tanaka, Daisuke; Senda, Jiro; Fujimoto, Hajime

doi:10.4271/970871

Cited by 83 publications

(32 citation statements)

References 6 publications

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“…When the bubble growth rate is less than a value of 27, the breakup void fraction is nearly independent of the bubble growth rate. This trend agrees with the hypothesis of Senda et al [19] and Adachi et al [20] , which states that the breakup occurs when the void fraction is larger than a prescribed value. However, when the bubble growth rate is larger, the breakup void fraction decreases dramatically with the increase of bubble growth rate, and the breakup void fraction has slightly lower values at higher radius ratio.…”

Section: Bubble Breakupsupporting

confidence: 88%

Numerical modeling of dimethyl ether (DME) bubble growth and breakup

Zhang

2009

Chin. Sci. Bull.

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A numerical program is written to simulate the process of vapor bubble growth with spherical symmetry from the thermodynamic critical radius in an initially uniformly superheated liquid. The program is validated by the experimental data of superheated water. The calculated results agree with those of experiments well. The program takes into account the variations of properties with temperature precisely to simulate the DME bubble growth under flash boiling conditions. Considering the influences of pressure, surface tension and viscous stress, the linear stability analysis method is adopted to deduce the dispersion equation to represent the disturbance development during the bubble growth, and a new criterion for bubble breakup is established. The results show the bubble becomes more unstable with the increase of bubble Weber number and void fraction, and that with the increase of bubble growth rate or the decrease of initial radius ration of droplet to bubble, the breakup time of bubble becomes shorter.dimethyl ether, flash boiling, bubble growth, instability, bubble breakupThe flash boiling spray has potential in improving engine performance since it can be used to promote the atomization of fuels with a larger spray cone angle and a smaller droplet Sauter Mean Diameter (SMD) and so on [1,2] . As a clean fuel with potential long-lasting resources, DME has been considered as a promising alternative fuel for compression-ignition engines in recent years. The low boiling point and high saturated vapor pressure nature make the DME spray undergo flash boiling at lower ambient pressure [3,4] . Therefore, the research on DME spray under flash boiling conditions is of great significance.As two stages of flash boiling spray, bubble growth and breakup [5] , are becoming more central to the deep understanding of the spray atomization under flash boiling conditions. So, a single bubble in the infinite liquid field is chosen as the investigated subject in this paper and a computational program is presented for the solution of DME bubble growth based on the one-dimensional mathematic model. In addition, the linear stability theory is applied to solve the instable problem during the DME bubble growth, and a more complete dispersion equation is obtained, which is helpful to improve the study on the atomization mechanism of flash boiling spray.

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Section: Bubble Breakupsupporting

confidence: 88%

Numerical modeling of dimethyl ether (DME) bubble growth and breakup

Zhang

2009

Chin. Sci. Bull.

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“…Therefore, it is assumed that N decreases as time elapses in the nozzle orifice and droplets. It was reported that the number of bubble nuclei obtained by numerical simulation using this assumption agrees with the experimental data [19]. The number density N of bubble nuclei are approximately expressed by the following equation:…”

Section: Bubble Nucleationsupporting

confidence: 67%

Numerical study on flash‐boiling spray of multicomponent fuel

Kawano

Ishii

Suzuki

et al. 2006

Heat Trans. Asian Res.

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Flash-boiling occurs when a fuel is injected into a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in the fuel spray when injected into the combustion chamber of an internal combustion engine under high pressure. In addition the multicomponent mixture of high-and low-volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in an internal combustion engine. It was found that the multicomponent fuel produces flash-boiling with an increase in the initial fuel temperature. Therefore, it is important to investigate these flash-boiling processes in fuel spray.In the present study, the submodels of a flash-boiling spray are constructed. These submodels consider the bubble nucleation, growth, and disruption in the nozzle orifice and injected fuel droplets. The model is implemented in KIVA3V and the spray characteristics of multicomponent fuel with and without flashing are numerically investigated. In addition, these numerical results are compared with experimental data obtained in the previous study using a constant volume vessel. The flashing spray characteristics from numerical simulation qualitatively show good agreement with the experimental results. In particular, it is confirmed from both the numerical and experimental data that flash-boiling effectively accelerates the atomization and vaporization of fuel droplets. This means that a lean homogeneous mixture can be quickly formed using flash-boiling in the combustion chamber.

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“…where h i,eff,s is the coefficient for the contribution of heat transfer by internal circulation at the saturation temperature, a sh is the heat transfer enhancement through the effect of nucleation which is modeled using the correlation of Adachi et al (1997). Detailed description of the boiling process modeling is given in Appendix B in Electronic Annex 1.…”

Section: Modeling the Boiling Processmentioning

confidence: 99%