Hydrogen has the very high heating value by comparing with other fuels and its combustion exhausts no carbon. But hydrogen causes the very high adiabatic flame temperature which generates thermal NOx. In this study, two cases of experiments were performed to compare engine characteristics. First and second cases are for only diesel combustion engine and mixed hydrogen diesel engine respectively. To verify the effect of mixed hydrogen-diesel combustion engine, the exhausted gas from modified dual fuel diesel engine was analyzed. In addition, diesel consumption per kWh for each case was estimated to validate its economic feasibility. By mixing hydrogen with 5kW brown(hydrogen-oxygen mixture) gas generator, the amount of CO(carbon mono-oxide) decreased from 330ppm to 210ppm by improving combustion and the amount of NOx increased from 390ppm to 520ppm by higher temperature of combustion chamber. Diesel consumption per kWh decreased from 450cc to 410cc but actually increased until 480cc because of the power of brown gas generator

The stoichiometric gas from an advanced alkaline electrolysis process as developed by Yull Brown is called as HHO gas or Brown gas. By this process, two moles of H2 and 1mole of O2 gases are generated stoichiometrically in a wellpremixed state. Due to the fact that very clean fuel can be obtained relatively easily by the simple equipment of electrolysis, the research of this gas has been continuously performed, even though the criticism has been made by many researcher of this area. The main controversial argument is in that the use of high quality electrical energy is used again for the generation of another combustible fuel with less than 100% efficiency in its energy transform. In fact, since Brown gas exists in the state of a completely mixed state only with oxygen molecule, there is no time delay due to turbulent mixing occurring in practical combustion process. Therefore, the high reaction rate is likely to have a high chance of backfire. Further, since there is no inert material like nitrogen as in air, the flame temperature rises unnecessarily high. In order to prevent the backfire phenomenon, the increase of injection velocity of fuel nozzle causes the formation of very unstable long flame with good chance of flame lift-off. One of practical application methods, the co-combustion of Brown gas with other fuel like gasoline and LNG, etc has been reported in open literature in order not only to increase the combustion efficiency but also for the reduction of pollutant emission such as NOx. In order to control the negative aspect of flame characteristics of Brown gas, in this study, an novel method is employed by premixing Brown gas with water vapor and the co-combustion performance and characteristics has been studied numerically for a combustor operated for kiln drying method. To this end, a commercial code(STAR-CCM+7.06) has been employed with the program verification against operational data of kiln drying combustor and a parametric numerical calculation has been made with the change of the amount of water vapor in the fuel mixture of Brown gas and water vapor. The calculation results show that the combustion feature looks quite stable without showing any unstable flame feature like long thin flame and backfire. Further temperature and streamline contours with the amount of water vapor content look consistent and physically acceptable. This result suggests that the addition of water vapor in the Brown gas looks one of promising method for the use of Brown gas as clean fuel.