Fuel Gases Combustion Values

Overview

Engineering reference data for Fuel Gases Combustion Values in combustion engineering.

Key Formulas

Heat Release

$Q = \dot{m} \cdot HV$

Fuel energy release rate.

Air-Fuel Ratio

$AF = \frac{m_{air}}{m_{fuel}}$

Mass of air per mass of fuel.

Excess Air

$EA = \frac{O_2}{21 - O_2} \times 100\%$

From flue gas oxygen measurement.

Variables

Symbol	Description	Unit
$Q$	Heat release rate	W
$\dot{m}$	Mass flow rate	kg/s
$HV$	Heating value	J/kg
$AF$	Air-fuel ratio	—

Combustion Values Data

Unit Conversion Factors

The combustion values in Btu/ft³ can be converted to other common units:

$1 \, \text{Btu/ft}^3 = 8.9 \, \text{kcal/m}^3$

$1 \, \text{Btu/ft}^3 = 3.73 \times 10^4 \, \text{J/m}^3$

Notes on Specific Gravity

• *Specific gravity < 1.0: Gas is lighter than air and will rise when released
  • Examples: Hydrogen (0.07), Methane (0.55), Natural Gas (0.66)
• *Specific gravity > 1.0: Gas is heavier than air and will settle in low areas
  • Examples: Butane (1.95), Propane (1.77), Acetylene (0.91)
• Air has a specific gravity of 1.0 (reference value)

Data Notes

• Manufactured Gas and Natural Gas show ranges because composition varies by source and region
• Propane-Butane Mix values depend on the mixing ratio (typically 60/40 or 70/30)
• Combustion values represent higher heating value (HHV) unless otherwise specified

References

• Original Source