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193812

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

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Last updated: 04 Jan 2025

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Abstract

  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 (𝑉̅𝑎 = 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 𝑉̅𝑎 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.

DOI

10.21608/erj.2021.193812

Keywords

Inverse diffusion flame, Elliptic burner, Liquefied petroleum gas, Flame structure, Flame stability

Authors

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A. Mahgoub

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Affiliation

Department of Mechanical Power Engineering, Faculty of Engineering at El-Mataria, Helwan University, Massaken El-Helmia, P.O. 11718, Cairo, Egypt.

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First Name

A.

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M. Hussien

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Department of Mechanical Power Engineering, Faculty of Engineering at El-Mataria, Helwan University, Massaken El-Helmia, P.O. 11718, Cairo, Egypt.

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First Name

K.

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A. Emara

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Department of Mechanical Power Engineering, Faculty of Engineering at El-Mataria, Helwan University, Massaken El-Helmia, P.O. 11718, Cairo, Egypt.

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Volume

171

Article Issue

0

Related Issue

27526

Issue Date

2021-09-01

Receive Date

2021-09-09

Publish Date

2021-09-01

Page Start

119

Page End

137

Print ISSN

1110-5615

Article File

ERJ_Volume 171_Issue 0_Pages 119-137.pdf

PDF . 1.6MB

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https://erj.journals.ekb.eg/article_193812.html

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https://erj.journals.ekb.eg/service?article_code=193812

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Original Article

Type Code

998

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Publication Title

Engineering Research Journal

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https://erj.journals.ekb.eg/

MainTitle

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

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Article

Created At

22 Jan 2023