Did you know that the methane number of a gas provides an indication of the knock tendency of a fuel? It is a product of the different constituent gases within the natural gas, particularly the proportions of methane, ethane, propane and butane. Understanding the knock resistance is important when specificing an engine for a gas-powered combined heat and power plant.
Methane, which has a high knock resistance, is given an index value of 100. Hydrogen, which burns quickly relative to methane, has a low knock resistance and is given the index value of 0. If a gas mixture has a methane number of 80, its knock resistance is equivalent to that of a gas comprised of 80% methane and 20% hydrogen. There are gas constituents which have a higher methane number than 100 therefore it is also possible for a gas composite to have a higher methane number than 100. Biogas often has a methane number in excess of 100.
Understanding the methane number of the natural gas fuel is an important factor when determining the appropriate engine version to select.