Measurements of Laminar Flame Speeds of Alternative Gaseous Fuel Mixtures

Global warming and the ever increasing emission levels of combustion engines have forced the engine manufacturers to look for alternative fuels for high engine performance and low emissions. Gaseous fuel mixtures such as biogas, syngas, and liquefied petroleum gas (LPG) are new alternative fuels that have great potential to be used with combustion engines. In the present work, laminar flame speeds (S_L) of alternative fuel mixtures, mainly LPG (60% butane, 20% isobutane, and 20% propane) and methane have been studies using the tube method at ambient conditions. In addition, the effect of adding other fuels and gases such as hydrogen, oxygen, carbon dioxide, and nitrogen on S_L has also been investigated. The results show that any change in the fuel mixture composition directly affects S_L. Measurements of S_L of CH₄/LPG–air mixtures have found to be about 56 cm/s at ø = 1.1 with 60% LPG in the mixture, which is higher than S_L of both pure fuels at the same ø. Moreover, the addition of H₂ and O₂ to the fuel mixtures increases S_L notably, while the addition of CO₂/N₂ mixture to the fuel mixture, to simulate the EGR effect, decreases S_L of CH₄/LPG–air mixtures.