Experimental Study on Flame‒Flame Interaction and Its Merging Features Induced by Double Rectangular Propane Diffusion Burners With Various Aspect Ratios

ABSTRACT

An experimental study is conducted to reveal the flame‒flame interaction (including completely continuous merging phenomenon, intermittent merging phenomenon, and non-merging phenomenon) of and the merging flame length of double propane diffusion flame with various aspect ratios, and its influence is measured in terms of the fire heat release rates, separate spaces between rectangular sources and different pool aspect ratios (1:1, 1:2, 1:4, and 1:8). The flames merging behaviors are recorded by a charge-coupled device (CCD) camera. The merging probability of double propane diffusion flame is found to increase with the increasing of the heat release rate and the pool aspect ratio. A correlation has been developed to estimate the merging probability of the double propane diffusion flame under different aspect ratios and separate spaces. The correlation is proposed to describe the merging flame length of two rectangular diffusion flames with various aspect ratios, which is an inverse proportional function of dimensionless heat release rate.

KEYWORDS:

• Double diffusion flame
• merging probability
• separate space
• aspect ratio
• flame interaction

Nomenclature

$A$	=	The width of rectangular nozzle (mm)
$B$	=	The length of rectangular nozzle (mm)
$C_1$	=	Constant
$C_P$	=	Specific heat capacity of air
$D^{\ast }$	=	Equivalent diameter
$D^{\ast \ast }$	=	Equivalent diameter
$g$	=	Gravitational acceleration
$l$	=	Inside separate space
$L$	=	Central separate space
$Q$	=	Heat release rate (HRR)
${\dot{Q}}_n^{\ast }$	=	Dimensionless heat release rate
$s$	=	Section area of the burner
$T_{\mathrm{\infty }}$	=	Ambient temperature
$t$	=	Time of visible flame at steady stage
$t^{\prime }$	=	Time recorded by the CCD camera at steady stage of the pool fire
$P_s$	=	Visible probability of single pool fire
$P_m$	=	Merging probability of double pool fires
$n$	=	Aspect ratio (B/A)

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [Grant No.71431003], China Postdoctoral Science Foundation funded project [Grant No.2016M602008] and Fundamental Research Funds for the Central Universities of China [Grant No. JZ2017HGTB0208].