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To counteract the harmful effects of vehicle emissions on humans and the environment, such as global warming due to greenhouse gases, there is a focus on gaseous fuels as an alternative energy source of transportation. Heavy-duty natural gas vehicles are widely used to improve the air quality of urban areas in Korea because natural gas has the advantage of low greenhouse gas emission levels. However, more in-depth study is required in order for clean fuel vehicles to hold a dominant position over well-developed diesel vehicles. It is difficult to meet reinforced emission standards with only a lean combustion strategy without an aftertreatment system in a lean-burn natural gas engine. Hydrogen-natural gas (HCNG) blends have been proposed as an alternative to improve fuel economy and emissions of lean-burn natural gas engines, since they have a wider flammability range and faster burning speed. HCNG blends could also play a role as a technical bridge for the hydrogen era.

Finding an alternative fuel and solving the environmental pollution are the main targets for the future internal combustion engines. CNG(Compressed Natural Gas) bus is used for a public transportation in Korea because it has low carbon/hydrogen ratio and discharges low pollutant emissions. But CNG fuel has low burning rate. Therefore, in this study, hydrogen is added and DSP(Dual Spark Plugs) are used for making up for the demerits in CNG. HCNG(Hydrogen-CNG) as a fuel is now considered as one of the alternative fuels due to its low pollutant emissions and high burning rate. An experimental study was carried out to obtain the fundamental data about the combustion and emission characteristics of premixed hydrogen and CNG in a CVC(Constant Volume Chamber) with various fraction of Hydrogen-CNG blends using SSP(Single Spark plug) and DSP.