Concentric elliptical jet diffusion flames with co- and cross-flows

Kashkousha, OA; Kamal, M. M.; Abdulaziz, A. M.; Nosier, M. A.

doi:10.1016/j.expthermflusci.2012.03.033

Cited by 11 publications

(7 citation statements)

References 29 publications

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“…This is illustrated with the aid of the vortical patterns in Figure 5. As recently found by Kashkousha et al., 17 when the inner velocity is larger than the outer velocity (which is the case here for an inverse diffusion flame where the air jet velocity in the central hole becomes higher) the optimum angular orientation is 35°. This is due to the favorable combination of having relative positions of 0° (whereby the entrainment vortices for the two elliptical jets are counteracting to produce the maximum shearing strain) and 90° (whereby the inner jet major axis tips become closer to the surrounding flow thus providing a smaller flow gap for enlarging the axial velocity strain).…”

Section: Resultssupporting

confidence: 68%

“…Higher strain rates are achievable upon changing the relative angular orientation between the concentric streams. Since this was done on normal diffusion flames (as previously described 17 ), the performance enhancement was obtained upon switching to the inverse diffusion flames (in accordance with the central high velocity air stimulated turbulence). At this stage, the cross-flow provides the stagnation impact that enables the extension of the stable firing limits to involve higher velocities so as to enrich the rates of flow strain.…”

Section: Resultsmentioning

confidence: 99%

“…For such purpose, the favorable effect of changing the angular orientation of elliptical jets on inverse diffusion and partially premixed flames is currently investigated (where the inner flame envelope (A) and the outer flame envelope (B) in Figure 1(a) are proposed to be strained). In a recent work, 17 the optimum angular orientation between two concentric elliptical jets was found to depend on their aspect ratios whose increase delays the axial location at which axis switching takes place thus resulting in less fluid entrainment. 13,18 It is thus required to examine if the same optimum value of angular shift properly fits the inverse diffusion and inverse partially premixed flames.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Inverse diffusion and partially premixed flames with elliptical/swirling- and cross-flows

Kashkousha

Kamal

Abdulaziz

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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The combustion performance of inverse diffusion and partially premixed flames was optimized by employing concentric elliptical ports with variable relative angular orientation, co-swirling, and cross-flow opposing jets of different inclination angles. The flexible and favorably active control of combustion was pronounced by changing the nozzle relative angular orientation. The optimum angular shift was found to be 20° where the flame length was shortened by 39% from the case of 0° and the NOx levels were reduced to about 0.51 g/kg of fuel for the inverse partially premixed flames. At such optimum angular shift, the minimum CO and NOx emissions respectively decreased to 17.1 and 1.52 g/kg of fuel for the inverse diffusion flames. The elliptical jets increased the size of the swirling flow recirculation zone by about 28%. Increasing the inner aspect ratio consistently increased the combustion efficiency, where the CO emissions reach minimum values of 12.3 and 6.22 g/kg of fuel respectively for the inverse diffusion and partially premixed flames. The correspondingly minimum NOx emissions were thus 0.89 and 0.51 g/kg of fuel at a cross-flow momentum flux ratio of 2.0. Splitting the opposing cross-flow air jets by increasing their inclination angle above 0° duplicated the stagnation zone vortical impact to enrich the average turbulent energy at the major axis tips. The inclination angle of 15° was the optimum at no swirl while increasing the outer swirl angle shifted the optimum inclination angle to 25°. The inner/outer co-swirl of 45°/60° thus provided a minimum CO emission of 11.1 g/kg of fuel for the inverse diffusion flame and 2.65 g/kg of fuel for the inverse partially premixed flame.

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Section: Resultssupporting

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Inverse diffusion and partially premixed flames with elliptical/swirling- and cross-flows

Kashkousha

Kamal

Abdulaziz

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…此外, Fernandes 等人 [12] 对对冲交叉射流进行了研究, 采用实验手段测量了对冲交叉射流的时均速度分布和对冲涡结构等特性. Kashkousha 等人 [13] [18,19] . 格子 Boltzmann 方法(LBE)与传统数值…”

Section: 在能源工程领域气固两相交叉射流中的空气unclassified

气固两相交叉射流相间传热的lbe-Dem模拟

桂¹,

徐²,

闫³

et al. 2014

Chin. Sci. Bull.

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“…It was found that elliptic burner diffusion flames when properly employed in elliptic coflow could reduce certain pollutants. Jet diffusion flames of another concentric elliptic burner with co-and cross-flow streams were examined in [25]. Shadow graphic imaging using ultraviolet laser was performed on non-premixed flame issuing from concentric elliptic burner, [26].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Stability and Structure of Vertical LPG Inverse Diffusion Flames Issuing from an Elliptic Burner

Mahgoub

Hussien

Emara

2021

Engineering Research Journal

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The present paper experimentally examines the influence of the progressive variations of the central air jet velocity in a concentric circular-elliptical inverse diffusion flame (IDF) on the visual and thermal structure and stability of the developed flames. All experiments are conducted at a fixed fuel flow rate (liquefied petroleum gas) throughput that emerges from the annular elliptic passage having an aspect ratio of 2:1. The visual images are aided via a digital camera and shadowgraphs, while the thermal structure (axial and radial temperature profiles) is acquired using a bare fine wire (125 µm) thermocouple; rendering radiation loss insignificant. The visual images and shadowgraphs clearly indicate the existence of four regimes: (i) an annular partially premixed region at the burner rim, (ii) an inner central premixed blue flame, (iii) an outer luminous yellowish post combustion zone and (iv) the flame tip buoyant zone. The progressive increases of the central average air velocity ( ̅ = 7.4 m/s up to 31.3 m/s) result in shortening the visible flame length and narrowing the flame width. These are coupled with changing the flame appearance from a yellowish diffusion flame with a sooty core regime to an intense central premixed flame surrounded by a soot ring to blue flames exhibiting intense central radiation regime associated with soot oxidation. At extremely high air velocity > 21 m/s, locals flame extinction and re-ignition occurs at the boundaries of the ellipse minor axis and further increase of ̅ causes complete extinction of the main flame. These findings are very much supported by the mean gas temperature measurements that indicate steep temperature rise associated with the formation of a central premixed combustion within the flame core which is followed by the diffusion mode of combustion. A plateau of the axial temperature profiles is observed in the transition zone between the two regions whereby the rise in temperature due to soot oxidation is balanced by the radiation loss.

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Concentric elliptical jet diffusion flames with co- and cross-flows

Cited by 11 publications

References 29 publications

Inverse diffusion and partially premixed flames with elliptical/swirling- and cross-flows

Inverse diffusion and partially premixed flames with elliptical/swirling- and cross-flows

气固两相交叉射流相间传热的lbe-Dem模拟

Experimental Investigation of Stability and Structure of Vertical LPG Inverse Diffusion Flames Issuing from an Elliptic Burner

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