Emission and performance estimation in hydrogen injection strategies on diesel engines

Recently, the increasing demand for energy requires the use of alternative fuels, especially in fossil fueled power systems. As a promising alternative fuel for next-generation diesel engines that utilize fossil fuel, hydrogen fuel is one step ahead due to its positive properties. In this study, the effects of hydrogen on the performance of a diesel engine have been numerically investigated with respect to different injection ratios and timings. The numerical results of the study for 25% load conditions on a single-cylinder, four-stroke diesel engine have been validated against experimental data taken from literature and good agreement has been observed for pressure results. Emission parameters such as NOx, CO and performance parameters such as cylinder temperature, pressure, power, thermal efficiency and IMEP are presented comparatively. The results of numerical analyses show that the maximum pressure, temperature and heat release rate are observed with injection ratio of H15 and early injection timing (20 degrees CA BTDC). Besides that, engine power, thermal efficiency and IMEP are greatly improved with increasing injection ratio and early injection timing. Although combustion chamber performance parameters improve with rising the hydrogen injection ratio, higher NOx emissions have also been detected as a negative side effect. Furthermore, while early injection timing increases diesel engine performance, it also causes an increase in NOx emissions. Therefore, precise determination of injection timing together with the optimum amount of hydrogen has revealed that it brings crucial improvement in engine performance and emissions. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.