To play video click here

• The flame videos obtained are converted to frames.


• The frames are analyzed using open source image processing software ImageJ.


• The still images of the flame are processed using Smoothing, Sharpening, Enhance contrast, and Edge detection steps for exact identification of flame tip from the nozzle rim.


• The number of pixels of the flame image along the flame centerline from the burner rim is counted and is scaled with the known dimension, the burner rim diameter, to obtain the jet flame height.

• Visible flame height (H_f) increases linearly with fuel flow rate (Q_f).


• Although the experimentally obtained relationship does not follow the phenomenological relationship derived earlier, the analysis correctly predicted the linear relationship.

Roper’s empirical formula




where
T₀: ambient temperature
T_f : characteristic temperature for calculating diffusivity (1500 K)
Q_F : volumetric flow rate of fuel
S: air-to-fuel volume ratio for complete combustion

• More uncertainty at larger Q_F due to the increase in buoyancy around the flame front which makes the flame tip to oscillate.


• The Roper’s empirical formula is found to underpredict the experimental value due to the assumed T_f.

Where
R_e - Reynolds number
V_F - Fuel jet velocity
ν - Kinematic viscosity of fuel
d_F - Diameter of the burner exit

• The experiments yield a relationship between non-dimensional visible flame height and flow rate in terms of Reynolds number.


• Students are encouraged to explore this relationship further with the help of graphical simulation utility.