Flame development characteristics inside a reverse-flow combustor at early stages of combustion

Mollahoseini, Zahra; Heydarlaki, Ramin; Kostka, P.; Aitchison, William; Kheirkhah, Sina

doi:10.1016/j.expthermflusci.2020.110254

Cited by 6 publications

(2 citation statements)

References 67 publications

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“…In this subsection, the procedures for reduction of the chemiluminescence and shadowgraphy images, which are used for studying the ignition delay and the droplet burning rate, are discussed. The chemiluminescence data reduction is similar to that discussed in several past investigations, see for example [94][95][96]. Figure 8(a) presents a raw chemiluminescence image.…”

Section: Data Reductionmentioning

confidence: 76%

Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

Mosadegh¹,

Ghaffarkhah²,

Kuur³

et al. 2021

Preprint

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Effects of graphene oxide nanomaterials addition and oxidation level on ignition delay and burning rate of ethanol droplets are experimentally investigated. Three graphene oxide samples are synthesized and characterized. Separate high-speed OH * chemiluminescence and high-speed shadowgraphy images are collected. The results suggest that increasing the loading concentration from 0 to 0.1% (by weight) generally increases the ignition delay, except for ethanol doped with the highly oxidized graphene. The results show that unlike pure ethanol droplets, atomization may occur for the doped ethanol droplets.It is demonstrated that, independent of the tested conditions, atomization occurs in the second half of the droplet lifetime. The probability density function of the atomized baby droplet diameter, initial projected velocity, and length of the projected trajectory are similar for all tested conditions and independent of the oxidation level and loading concentration of the additives. The joint probability density function calculated for the atomization-related parameters against one another suggests that the majority of the baby droplets feature a relatively short lifetime, indicating they may potentially burn inside the flame envelope. Using droplet surface regression curves versus time, the burning rate for periods in which the atomization does not occur, and for the periods that the atomization is present are estimated. The former burning rate is shown to enhance by increasing the loading concentration and reducing the oxidation level of graphene. However, supported by Fourier-Transform Infrared spectroscopy of the graphene oxide samples, it is found that a maximum increase in the latter burning rate for both loading concentrations occurs for ethanol doped with the graphene oxide that features maximum amount of infrared radiation absorption. To quantify the effect of atomization on the droplet mass loss, a conservation of mass framework is utilized, and it is shown that relatively intense atomization suppresses the mass loss. Doping ethanol with graphene oxide and increasing the loading concentration from 0.01 to 0.1% enhances the overall burning rate, with a maximum enhancement of 8.4% pertaining to addition of reduced oxidized graphene oxide and for the loading concentration of 0.1%.

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Section: Data Reductionmentioning

confidence: 76%

Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

Mosadegh¹,

Ghaffarkhah²,

Kuur³

et al. 2021

Preprint

Self Cite

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“…All acquired chemiluminescence images were subtracted by the background image (averaged for 200 chemiluminescence images before the droplet ignition) and were normalized for the spatially dependent sensitivity of the imaging equipment, similar to our past work 6,23,24 that utilized the same diagnostics. To minimize the electronics noise, a 7×7 pixels 2 window median-based filter was applied to the chemiluminescence images.…”

Section: Data Reductionmentioning

confidence: 99%

The role of atomization in the coupling between doped droplets dynamics and their flames

Mosadegh,

Kheirkhah

2022

Preprint

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The droplet and flame chemiluminescence dynamics as well as their coupling during atomization events of graphene oxide doped diesel are investigated experimentally.The tested doping concentrations are 0, 0.001, 0.005, 0.01, and 0.02% by weight. To minimize heat transfer between the droplet and its suspension mechanism, small diameter fibers are used for the droplet suspension. Separate shadowgraphy and OH * chemiluminescence measurements are performed at 4000 Hz to study the droplet and flame dynamics, respectively. The results show that both the droplet diameter squared and the flame chemiluminescence feature intermittent oscillations. The droplet diameter squared oscillations RMS is positively related to the number and intensity of the atomization events and the graphene oxide doping concentration. The probability density function of the inverse of the time separation between two consecutive atomization events and the power spectrum density of the droplet diameter squared oscillations feature dominant large probabilities and powers at about 25 Hz prior to the occurrence of the first intense atomization event. After the occurrence of the first intense atomization event, this frequency decreases to about 5 Hz for both.Although the intense atomization triggers the large amplitude oscillations at 5 Hz, it was argued that the retracting motion of the igniter induces the oscillations at 25 Hz.Our findings suggest that the atomization events are the root cause of the smaller frequency coupling between liquid fuel droplets doped with graphene oxide and their flames. This has implications for spray combustion research.

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Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

Mosadegh

Ghaffarkhah

Kuur³

et al. 2022

Combustion and Flame

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Flame development characteristics inside a reverse-flow combustor at early stages of combustion

Cited by 6 publications

References 67 publications

Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

The role of atomization in the coupling between doped droplets dynamics and their flames

Graphene oxide doped ethanol droplet combustion: Ignition delay and contribution of atomization to burning rate

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