Abstract
It is expected that liquid fossil fuels will be replaced by gaseous fuel within twenty years, and hydrogen may be of great importance by the mid-twenty-first century. However, recently, it has been difficult to secure a hydrogen economy, which starts from the establishment of a hydrogen infrastructure and leads to production, storage, and application. A transitional strategy should be prepared, and it is believed that a kind of partial application, such as reforming hydrocarbon fuel, could be a technical bridge to a hydrogen economy. Natural gas as an energy source for transportation has the advantage of emission at low levels. However, more technical researches should be carried out to hold a dominant position of clean fuel over well-developed diesel vehicles. Hydrogen/natural gas blends (HCNG) are promising fuels for solving the problems of present natural gas vehicles. It may possibly meet reinforced emission regulation, and North America and some European countries have already begun the development of an HCNG vehicle and the supply project of an HCNG station. The HCNG research project of Korea started in 2009 for developing an HCNG bus that meets the EURO-VI standard. In order to study the performance and emission characteristics of an HCNG engine, an 11-L, heavy duty, lean burn engine was used. The level of nitrogen oxides (NO_x), the most important component of emissions, is closely related to operation strategy. Therefore, operating parameters, including excess air ratio and spark advance timing, were optimized, and other parameters for high thermal efficiency were also examined.
