Experimental study on flame height, gas temperature and oxygen concentration profiles under spray fire scenario in an enclosed compartment

ABSTRACT

Spray fire is one of the most frequent fire accidents in ship engine compartments, drawing much attention to spray fire safety. Currently, a series of spray fire tests was conducted in a 2.0 m (L) × 2.0 m (W) × 1.88 m (H) enclosed compartment. Experimental results indicate that the combustion process can be divided into three stages and the injecting pressure has significant effect on the flame height, gas temperature, oxygen concentration, etc. The dimensionless flame height is proportional to the 1/9 power of the dimensionless heat release rate. With the increase in injecting pressure, both the slope of gas temperature rise and maximum average gas temperature increase, meanwhile the corresponding oxygen concentration and average oxygen concentration all decreases linearly. For estimating the average gas temperature and average oxygen concentration, two corresponding equations were established and verified by the current measured data. Moreover, the dimensionless gas temperature correlates well with the dimensionless oxygen concentration.

KEYWORDS:

• Spray fire
• flame height
• enclosed compartment
• gas temperature

Nomenclature

$A_s$	=	Compartment inner superficial areas, m2
$c_p$	=	Specific heat of gas, W/(kg·K) or W/(kg·°C)
D	=	Nozzle diameter, m
$g$	=	Gravity acceleration, m/s2
H	=	Flame height, m
H0	=	Spray height, m
$h$	=	Convective heat transfer coefficient, W/(m2·K) or W/(kg·°C)
K	=	Nozzle factor
$k$	=	Slope of gas temperature rise
$p$	=	Injecting pressure, MPa
${\dot{Q}}^{\ast }$	=	Dimensionless heat release rate
$\dot{Q}$	=	Effective heat release rate, kW
$r$	=	Stoichiometric air to fuel ratio
$T_{\mathrm{\infty }}$	=	Ambient temperature, °C or K
$T$	=	Average gas temperature, °C or K
$V$	=	Kerosene spray volume, L
$V_c$	=	Compartment volume, m3
$v$	=	Kerosene volume flow rate, L/min
${X_O}_2$	=	Oxygen volume concentration, %
$X_{\mathrm{\infty }}$	=	Ambient oxygen volume concentration, %
${Y_O}_2$	=	Oxygen mass concentration, %
$Y_{\mathrm{\infty }}$	=	Ambient oxygen volume concentration, %
$\mathrm{\Delta }{H}_c$	=	Enthalpy of kerosene, kJ/kg
$\mathrm{\Delta }T$	=	Average gas temperature rise above ambient temperature, °C or K

Greek Symbols

	=	Kerosene density, kg/m3
	=	Gas density, kg/m3
	=	Ambient density, kg/m3
	=	Combustion efficiency

Subscripts

c	=	Compartment
fuel	=	Kerosene
$g$	=	Gas
o2	=	Oxygen
s	=	Superficial
$\mathrm{\infty }$	=	Ambient

Additional information

Funding

This project was supported by The National Key Research and Development Program of China (No. 2017YFC0805100) and National Natural Science Foundation of China (No. 51806054).