Using hydrogen as alternative fuel in internal combustion engines

Renewable fuels have become a significant issue of research because of the environmental issues such as global warming, climate change, e.t.c. Furthermore, limited fossil fuel reserves, hazardous effects of pollutants caused by diesel and gasoline engines for human health, price increment of petroluem fuels, stringent emission regulations resulted in research of new technologies by automotive manufacturers. Especially, augmentation on diesel fuels within last years and environmental dangers of diesel fuels, gaseous fuels such as LPG and methane inspired the development of LPG and CNG conversion equipments for diesel engines. Hydrogen has unique chemical properties, in addition it doesn? t contain any carbon atom. Hydogen has high combustion efficiency, low ignition energy, wide flammability limits and low emission properties. Moreover, its properties are suitable for internal combustion engines. Hydrogen was used with diesel as hybrid fuel in this study, because it is a promising fuel. Pure hydrogen can? t be used in diesel engines owing to its high autoignition tempereature. Hydrogen will be introduced into intake manifold, and ignition can be started with pilot diesel injection. In this study, first of all 0%, 25% and 50% hydrogen of total fuel? s energy was introduced into intake manifold and pilot injection method was used at full load and at different engine speeds. In the second test, initially the engine was operated at 1100 rpm and 1300 rpm constant speeds and at the same brake engine torques and different hydrogen levels were tested. Secondly, the effect of hydrogen using pilot diesel injection was tested at part load conditions. The emissions (HC, CO, CO2, NOx, Smoke) and thermal efficiency were tested using hydrogen-diesel mixture as hybrid fuel in diesel CFR engine. During these tests, introduced heat energy for each cycle and excess air ratio were tried to adjust same values (except 1100 rpm and 1300 rpm constant speed and same brake torque tests). According to test results, CO, CO2 and smoke values were improved with hydrogen addition and HC emissions was modestly increased when hydrogen was used with diesel fuel. NOx emissions was decreased at part load conditions with using hydrogen-diesel hybrid fuel, but NOx emissions was increased at full loads by increasing hydrogen energy content in the total fuel energy. Nevertheless, released heat value was increased by increasing hydrogen level during pre-mixed combustion period, and released heat value was decreased by increasing hydrogen level during mixed combustion period. According to test results, CO, CO2 and smoke (particle matters) emissions were improved, HC emissions were modestly increased and NOx emissions were decreased by using hydrogen-diesel hybrid fuel at part load operations. Using hydrogen in diesel engines with pilot diesel injection method is convenient for urban traffic conditions which engines were run only at part loads operations.