Cellularization and intrinsic instability characteristics of 2-methylfuran spherical expanding flame

ABSTRACT

The flame morphology, flame instability and thermodynamic parameters of 2-methylfuran (2-MF) spherically expanding flame were studied at different initial temperatures, initial pressures, and equivalence ratios. Quantitative analysis of 2-MF flame surface cracks and cell structures was performed. The radius for the crack to enter the accelerated growth stage is reduced by 52.9% as the initial pressure increases from 2 bar to 4 bar. Also, the radius at which the crack enters the accelerated growth stage is reduced by 16.4% when the equivalence ratio is increased by 0.1. The radius required for the average cell area to stabilize is reduced by 31.5% when the initial pressure increases from 2 bar to 4 bar. Additionally, instability parameters were studied, and the results revealed that hydrodynamic instability and thermal-diffusion stability increase with increasing Peclet number. The relationship between the local instability and stability curves was discussed. The average wavenumber fitting line is closer to the upper limit of the instability curve when the equivalence ratio is 1.4, which is 8.5% higher than that of the equivalence ratio of 1.3. Next, the flame self-acceleration was studied, the initial pressure and equivalence ratio greatly promote the self-acceleration of the flame, but the temperature has no obvious effect, and the self-acceleration exponent of 2-MF flame is less than 1.5. Finally, the flame image information was reconstructed by a reconstruction algorithm and the cellularity factor was formulated to measure the degree of flame cellular. The cellularity factor is affected by initial pressure and equivalence ratio. Comparing and analyzing the evolution of flame cracks, flame self-acceleration, and cellularity factor, it was found that flame cracks promote flame self-acceleration and exacerbate flame cellularization and instability.

KEYWORDS:

• 2-methylfuran (2-MF)
• spherical expanding flame
• cellularization
• intrinsic instability
• flame self-acceleration

Nomenclature

Acronyms	=
2-MF	=	2-methylfuran
CVCB	=	Constant volume combustion bomb
C2H2	=	Acetylene
EA	=	Ethyl acetate
Symbols	=
Pe	=	Peclet number
Ti	=	Initial temperature
Tu	=	Unburnt mixture temperature
Pi	=	Initial pressure
Tad	=	Adiabatic temperature
$L{e}_{eff}$	=	Effective Lewis number
$Pr$	=	Prandt number
$L{e}_E$	=	Excess fuel Lewis number
$L{e}_D$	=	Deficient fuel Lewis number
$L_b$	=	Markstein length
$M_b$	=	Markstein number
$S_b$	=	Stretched flame speed
$\overline{S_b}$	=	Dimensionless flame speed
$S_b^0$	=	Unstretched flame speed
$K_a$	=	Karlovitz number
tc	=	Initiating time of cellularization
Rc	=	Initiating radius of cellularization
$n$	=	Wavenumber
Greek symbols	=
$\mathrm{\Omega }$	=	Thermal diffusion coefficient
$\sigma$	=	Thermal expansion ratio
$\beta$	=	Zeldovich number
$\omega$	=	Hydrodynamic coefficient
$R_L$	=	Logarithmic growth rate

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The financial support from the Zhejiang Provincial Natural Science Foundation of China (LZ23E060002), the Ningbo Major Science and Technology Project (20212ZDYF020041), the National Natural Science Foundation of China (No. 52076010) and the National Natural Science Foundation of China Research Fund for International Young Scientists (52350410458) is much appreciated

Notes on contributors

Enzhong Wu

Enzhong Wu is a graduate student at College of Mechanical and Electrical Engineering, China Jiliang University. He earned his Bachelor’s Degree in mechanical and electronic Engineering from China Jiliang University. Since 2021, he is pursuing Master’s Degree in Electronic and Information Engineering from the College of Mechanical and Electrical Engineering, China Jiliang University, China.

Cangsu Xu

Dr Cangsu Xu is an associate Professor at College of Energy Engineering, Zhejiang University, China. He earned his PhD in Power Engineering and Engineering Thermal Physics from Shanghai Jiao Tong University, China in 1996. His research area includes laminar combustion characteristics of biomass fuels, spray characteristics at high temperature and high back pressure, and visual single-cylinder engine research. He has published more than 120 papers.

Xiaolu Li

Dr Xiaolu Li is a Professor at College of Mechanical and Electrical Engineering, China Jiliang University, China. He earned his PhD in Power Engineering and Engineering Thermal Physics from Shanghai Jiao Tong University, China in 2005. His research area includes inspection technologies and devices, and the application of artificial intelligence to power plants. He has published more than 180 papers, of which more than 60 are included in SCI, and more than 30 invention patents are authorized.

Yangan Bao

Yangan Bao is a graduate student at the School of Mechanical and Electrical Engineering, China Jiliang University, China. He earned his Bachelor’s Degree in mechanical and electronic Engineering from China Jiliang University. Since 2021, he is pursuing Master’s Degree in Electronic and Information Engineering from the College of Mechanical and Electrical Engineering, China Jiliang University. He has published more than 2 papers in various national and international journals.

Yuntang Li

Dr Yuntang Li is a Professor at College of Mechanical and Electrical Engineering, China Jiliang University, China. He earned his PhD from Shanghai Jiao Tong University, China in 2007. His research area includes Static pressure gas bearing, cable-stayed bridge cable inspection and maintenance robot, UAV power inspection. He has published more than 70 academic papers and authorized more than 20 invention patents.

Francis Oppong

Dr Francis Oppong is a Lecturer at the College of Mechanical and Electrical Engineering, China Jiliang University. He earned his PhD in Thermal Power Engineering from Zhejiang University, China P. R in 2021. His research area includes flame instability, thermoacoustic instability, laminar burning velocity, explosion characteristics, turbulent jet ignition, artificial intelligence in combustion, chemical mechanisms, and quantum chemistry. He has published more than 30 papers in prestigious energy and combustion science journals.