What is the Difference Between Flame Speed and Burning Velocity?

The key difference between flame speed and burning velocity lies in what they represent in the context of combustion reactions:

• Flame Speed: This is the rate of expansion of the flame front in a combustion reaction. It represents the speed at which the flame front moves outward from the source of ignition.
• Burning Velocity: This is the speed at which a flame front propagates relative to the unburned gas. It represents the rate of movement of chemical reactants into the reaction.

There are different types of burning velocity, such as:

1. Laminar Burning Velocity (SL): This is the speed at which a laminar (planar) combustion wave propagates relative to the unburned gas mixture ahead of it.
2. Fundamental Burning Velocity (Su): This is a characteristic parameter referring to standardized unburned gas conditions, which has been corrected for nonidealities in the measurement. It is generally not identical to the observed laminar burning velocity.
3. Turbulent Burning Velocity (St): This exceeds the burning velocity measured under laminar conditions and is influenced by turbulence in the gas mixture.

In summary, flame speed measures the rate of expansion of the flame front, while burning velocity measures the rate of movement of chemical reactants into the reaction, with different types of burning velocity accounting for different conditions and levels of turbulence in the gas mixture.

Comparative Table: Flame Speed vs Burning Velocity

Flame speed and burning velocity are two important aspects of fuel combustion characteristics, but they represent different concepts. Here is a table highlighting the differences between flame speed and burning velocity:

The key difference between flame speed and burning velocity is that flame speed represents the rate of expansion of the flame front, whereas burning velocity represents the rate of movement of chemical reactants into the reaction.