Introduction
With the increasingly prominence of energy and environment
problems, it is important to explore new fuels instead of the
petroleum-based fuel and develop efficient low-pollution internal
combustion engine. In recent years, the natural gas has
been known as the high-quality gaseous fuel. In addition, some
gaseous fuels with lower heat value (such as coal-bed methane,
biogas, etc.) are becoming the research focus around the world
[1,2]. The coal-bed methane is mainly composed by 40%w80%
methane and 20% w 60% nitrogen and the biogas is mainly
composed by 40% w 60% methane and 40% w 60% carbon dioxide
[3]. In these fuels, the proportion of the methane (CH4)
content is relatively lower and that of non-hydrocarbon gases
(mostly CO2, N2, etc.) are higher in general. Therefore, the heat
values of those fuels are lower compared with nature gas.