What is the Difference Between Flame Speed and Burning Velocity

Thekey difference between flame speed and burning velocityis that flame speed represents the rapidness of the traveling of the flame from an absolute reference point, whereas burning velocity represents the rate of movement of chemical reactants into the reaction sheet from a local reference point that is located on the flame front.

Flame speed and burning velocity are two different terms that are useful in studies related to flames. Flame speed is the rate of expansion of the flame front in acombustion reaction. Burning velocity, on the other hand, is thespeedat which a flame front propagates relative to the unburnt gas.

1.Overview and Key Difference
2.What is Flame Speed
3.What is Burning Velocity
4.Flame Speed vs Burning Velocity in Tabular Form
5.Summary – Flame Speed vs Burning Velocity

What is Flame Speed?

Flame speed is the rate of expansion of the flame front in a combustion reaction. Generally, flame propagates spherically, and we can name the velocity of the radial flame propagation as flame speed. Generally, flame speed represents the rapidness of the traveling of the flame from an absolute reference point. On the other hand, burning velocity represents the moving rate of chemical reactants into the reaction sheet from a local reference point that is located on the flame front (There, chemical reactants are usually unburnt gases while reaction sheet refers to the flame front).

When considering aninternal combustion engine, we can describe the flame speed as a property that can determine the ability of the engine to undergo controlled combustion withoutdetonation. We can use flame speed along with adiabatic flame temperature for the determination of the engine’s efficiency. However, flame speed is not the actual engine flame speed. For example, the 12:1 compression ratio gasoline engine that performs at 1500 rpm tends to have a flame speed of around 16.5 m/s while a similar hydrogen engine tends to yield 48.3 m/s.

What is Burning Velocity?

Burning velocity can be described as the speed at which a flame front propagates relative to the unburnt gas. A derivative of this term is the laminar burning velocity, which can be defined as the speed at which a laminar (planar) combustion wave propagates relative to the unburnt gas mixture that is ahead of it.

What is the Difference Between Flame Speed and Burning Velocity?

Flame speed and burning velocity are two different terms that are useful in studies related to flames. The key difference between flame speed and burning velocity is that flame speed represents the rapidness of the traveling of the flame from an absolute reference point, whereas burning velocity represents the rate of movement of chemical reactants into the reaction sheet from a local reference point that is located on the flame front.

The following table summarizes the difference between flame speed and burning velocity.

Summary – Flame Speed vs Burning Velocity

Flame speed is the rate of expansion of the flame front in a combustion reaction. Burning velocity is the speed at which a flame front propagates relative to the unburnt gas. The key difference between flame speed and burning velocity is that flame speed represents the rapidness of the traveling of the flame from an absolute reference point, whereas burning velocity represents the rate of movement of chemical reactants into the reaction sheet from a local reference point that is located on the flame front.

Reference:

1. “Flame Speed.” An Overview | ScienceDirect Topics.
2. Hacohen, J., et al. “Flame Speeds in a Spark Ignition Engine.”Flame Speeds in a Spark Ignition Engine.