In combustion analysis, what is the most likely cause of flames that are lifting off the burner?

• A. The air supply is insufficient for complete combustion
• B. The flow rate of the fuel is too low compared to the oxidizer
• C. The temperature of the burner is too high
• D. The burner is clogged with residue

Answer: (B)

Verified step by step guidance

1. Understand that in combustion analysis, a flame lifting off the burner means the flame is not stable and is detaching from the burner tip.
2. Recognize that flame stability depends on the balance between the fuel flow rate and the oxidizer (usually air) flow rate.
3. If the fuel flow rate is too low compared to the oxidizer, the flame speed decreases and the flame can lift off because the mixture is too lean to stay attached to the burner.
4. Consider that insufficient air supply usually causes a yellow, sooty flame due to incomplete combustion, not flame lift-off.
5. Note that a clogged burner or high burner temperature typically affects flame shape or color but does not cause the flame to lift off.