Forced thermal ignition of a polydisperse fuel spray

Kats, G.; Greenberg, J.B.

doi:10.1080/00102202.2017.1415893

Cited by 3 publications

(3 citation statements)

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“…of the liquid fuel in larger droplets (see Table 1). This effect is reduced as the initial mixture becomes richer, so that more fuel vapor becomes available for ignition and any heat loss effect due to droplet evaporation is less focused (see also Kats and Greenberg 36 ). In any event, the qualitative shape of the curves and the existence of minimum ignition energy (MIE) type of behavior (see literature 5,6 ) bear some resemblance to independent experimental evidence, 11 albeit for monodisperse sprays, thereby providing some encouragement for the correctness of the theory, within the limits of its basic assumptions.…”

Section: Results For Initially Polydisperse Distributionsmentioning

confidence: 99%

“…In contrast, unsteady governing equations were solved in the literature 36,37 to examine the ignition of a polydisperse fuel spray-air mixture in the half-plane, subject to an initial thermal field. The analysis considers fuel build-up due to droplet evaporation but only seeks conditions of thermal runaway, which define when the temperature rises abruptly.…”

Section: Introductionmentioning

confidence: 99%

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Polydisperse spray flame ignition by a pulsed heat flux

Kats¹,

Greenberg

2021

International Journal of Spray and Combustion Dynamics

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A mathematical analysis of the ignition of a polydisperse spray/air mixture by an infinite surface heated in a pulsed manner is presented. In contrast to previous work in the literature, the entire history of the ignition process is accounted for starting from the flame-embryo progenitor stage, through the thermal runaway stage to the final flame propagation stage. For tractability at the current stage, the chemical kinetics is taken to be that of a single global reaction. The spray is modeled using the sectional approach and the influence of fuel spray characteristics on ignition is determined. Good agreement was found between the theoretical predictions and full numerical simulations. Delay in ignition due to the build-up of vapor from the fuel droplets as well as heat loss to the droplets for evaporation are found to play a significant role under certain operating conditions. Comparison between the critical energy flux and the initial spray polydispersity revealed small differences for larger values of the pulse duration but more significant minor differences for smaller pulse durations. Despite these seemingly minor differences, it was shown that the initial spray polydispersity can have a critical influence on whether flame ignition will occur or fail, even for sprays having the same initial SMD.

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Section: Results For Initially Polydisperse Distributionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polydisperse spray flame ignition by a pulsed heat flux

Kats¹,

Greenberg

2021

International Journal of Spray and Combustion Dynamics

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“…Semenov pioneered the description of thermal explosion processes for gaseous fuels using simple ordinary differential equations [21]. History has shown that simplified Semenov-type models can often describe the main characteristics of self-ignition in the homogeneous case [22]. However, the models built on Semenov's work that focus on sprays quickly became very complex when accounting for various droplet radii [23].…”

Section: Introductionmentioning

confidence: 99%

The Evolutions in Time of Probability Density Functions of Polydispersed Fuel Spray—The Continuous Mathematical Model

2021

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The dynamics of the particle size distribution (PSD) of polydispersed fuel spray is important in the evaluation of the combustion process. A better understanding of the dynamics can provide a tool for selecting a PSD that will more effectively meet the needs of the system. In this paper, we present an efficient and elegant method for evaluating the dynamics of the PSD. New insights into the behaviour of polydispersed fuel spray were obtained. A simplified theoretical model was applied to the experimental data and a known approximation of the polydispersed fuel spray. This model can be applied to any distribution, not necessarily an experimental distribution or approximation, and involves a time-dependent function of the PSD. Such simplified models are particularly helpful in qualitatively understanding the effects of various sub-processes. Our main results show that during the self-ignition process, the radii of the droplets decreased as expected, and the number of smaller droplets increased in inverse proportion to the radius. An important novel result (visualised by graphs) demonstrates that the mean radius of the droplets initially increases for a relatively short period of time, which is followed by the expected decrease. Our modified algorithm is superior to the well-known `parcel’ approach because it is much more compact; it permits analytical study because the right-hand sides of the mathematical model are smooth, and thus eliminates the need for a numerical algorithm to transition from one parcel to another. Moreover, the method can provide droplet radii resolution dynamics because it can use step functions that accurately describe the evolution of the radii of the droplets. The method explained herein can be applied to any approximation of the PSD, and involves a comparatively negligible computation time.

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