Effect of N 2 Replacement by CO 2 in Coaxial-Flow on the Combustion and Emission of a Diffusion Flame

Haisheng Zhen, Zhilong Wei and Zhenbin Chen
Additional contact information
Haisheng Zhen: The Mechanical and Electrical Engineering College, Hainan University, Haikou 570228, China
Zhilong Wei: The Mechanical and Electrical Engineering College, Hainan University, Haikou 570228, China
Zhenbin Chen: The Mechanical and Electrical Engineering College, Hainan University, Haikou 570228, China

Energies, 2018, vol. 11, issue 5, 1-16

Abstract: In this study, a double concentric burner burning methane with an annular coaxially-flowing oxidizer was adopted to operate the diffusion flame in lifted flame regime. The effects of coaxial-flow velocity, coaxial-flow composition variation through total and partial replacement of N 2 , and coaxial-flow oxygen enrichment were experimentally investigated in terms of the resultant changes in the flame stability, and thermal and emission characteristics. Consistent with the triple flame theory, the current stability tests show a linear increase in flame lift height with increasing coaxial-flow velocity and the blowout of lifted flames occurred at constant flame tip height. Replacement of N 2 by CO 2 in the coaxial-flow deteriorated the flame stability by significantly reducing the threshold coaxial-flow velocity. Due to combustion enhancement that is caused by oxygen enrichment, the threshold coaxial-flow velocity increased and this increase is more significant for the N 2 -diluted flame than CO 2 -diluted. Two of the most important NO x formation mechanisms, Zeldovich and Fenimore, were analyzed under the relatively low temperature flame conditions, generally below 1300 °C in this study. Results show that NO x is principally produced via the Fenimore mechanism for both N 2 - and CO 2 -diluted flames. NO x productions can be significantly affected by coaxial-flow composition and coaxial-flow velocity. An increase in the velocity of N 2 -diluted coaxial-flow increases NO x emissions, while a reverse trend occurred, as N 2 in the coaxial-flow was replaced or partially replaced by CO 2 , which is ascribed to the strong combustion-resisting behavior of CO 2 . For all cases, CO emissions vary in the opposite direction of NO x emissions. Due to the strong thermal and chemical effects of CO 2 on combustion in comparison to N 2 , total or partial replacement of N 2 by CO 2 results in a steep increase in CO emissions.

Keywords: flame stability; lift off height; coaxial-flow; dilution; CO/NO x emissions (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

Downloads: (external link)
https://www.mdpi.com/1996-1073/11/5/1032/pdf (application/pdf)
https://www.mdpi.com/1996-1073/11/5/1032/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:11:y:2018:i:5:p:1032-:d:142875

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().