Morphological Characteristics of Propane–Hydrogen Diffusion Flame: Experiments and Correlations

ABSTRACT

This study investigated the flame height and liftoff height of turbulent diffusion jet flames of the Propane–Hydrogen mixed gas. A series of experiments have been conducted to examine their flame height and liftoff height with different concentrations of propane and hydrogen. The experimental results show that the flame height decreases with the increase in hydrogen concentration. The accuracy of the Froude number for the prediction of flame height has been verified. The liftoff height is proportional to the propane flow rate, while it was inversely proportional to the hydrogen concentration due to the increased laminar flame speed. A theoretical model incorporating laminar flame speed, heat release rate, and fuel exit velocity has been obtained. These investigations are crucial for enhancing safety in hydrogen-enriched pipeline systems, which is helpful for the use of hydrogen in energy systems and global sustainability efforts.

KEYWORDS:

• Jet flame
• mixed gas
• hydrogen
• flame height
• lift-off height

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

$\mathit{A}$	=	Nozzle outlet area (m2)
$c_p$	=	specific heat at constant pressure [J/(kg-K)]
$\mathit{D}$	=	Nozzle diameters (mm)
$\mathit{F}{r}_f$	=	Flame Froude number
$f_{\mathit{v},{\mathrm{H}}_2}$	=	H2 volume ratio
$\mathit{G}$	=	Momentum flux (kg m/s2)
$\mathit{h}$	=	Lift-off height (cm)
$\mathit{J}$	=	Buoyancy flux (kg m/s2)
$L_f$	=	Flame height (m)
$L^{\ast }$	=	Dimensionless flame length
${\dot{m}}_0$	=	Mass flow rate of fuel (kg/s)
${\dot{m}}_{\mathit{f}}$	=	Mass flow rate of the flame plume (kg/s)
${{\overline{\text{dotm}}}^{{ }^{\prime \prime \prime }}}_{\mathit{F}}$	=	Mean volumetric mass production rate [kg/(s⋅m3)]
$\mathit{n}$	=	Overall reaction rate
$\dot{Q}$	=	Heat release rate (kW)
${\dot{Q}}_{{\mathrm{C}}_3{\mathrm{H}}_8}$	=	C3H8 heat release rate (kW)
${\dot{Q}}^{\ast }$	=	Dimensionless heat release rate
Re	=	Reynolds number
$\mathit{S}$	=	Stoichiometric ratio
$S_L$	=	Laminar flame speed (cm/s)
$T_f$	=	Flame temperature (K)
$T_{\mathrm{\infty }}$	=	Ambient temperature (K)
$\overline{\mathrm{\Delta }{\mathit{T}}_{\mathit{f},\mathit{a}}}$	=	Characteristic temperature rise (K)
$\mathit{u}$	=	Fuel outlet velocity (m/s)
$u_f$	=	Characteristic flame propagation velocity (m/s)
Greek symbols	=
${\rho }_u$	=	Fuel density (kg/m3),
${\rho }_f$	=	Flame density (kg/m3)
${\rho }_{\mathrm{\infty }}$	=	Ambient density (kg/m3)
$\mathit{\mu }$	=	Dynamic viscosity [Pa-s]

Additional information

Funding

The work was financially supported by the National Natural Science Foundation of China [No. 52274184].