Performance and emission characteristics of fish oil methyl ester in direct injection diesel engine with hydrogen enrichment - an experimental approach

Although fossil fuels are used in various automobile and agriculture sectors, the world is still facing a huge energy demand, which needs to be addressed. This study evaluates the thermal performance and emission characteristics of a diesel engine fueled by using fish oil biodiesel (B20) blend as a main fuel through the fuel injector and introducing hydrogen fuel as a secondary fuel through the air intake manifold. As hydrogen fuel is inducted through the intake manifold along with the air, the emission from the tail pipe is reduced, and the hydrogen flow is varied from 0 to 4 LPM. From the comparison of experimental results on performance analysis with diesel fuel, it is found that with a maximum rate of hydrogen flow as 4 LPM through the intake manifold and with the fish oil B20 blend, the fuel consumption is reduced by about 12.8% compared to diesel fuel which improved the thermal efficiency to 34.5%. However, the thermal efficiency of the engine fueled using fish oil biodiesel (B20) is lower as compared to diesel fuel as the kinematic viscosity of the biodiesel blend is slightly higher, which impacts the fuel penetration through the fuel injector and thereby influences the improper mixing of air fuel mixture in the combustion chamber during combustion. Emission reduction was also observed, with carbon monoxide (CO) emissions at full load reduced by 45.7% and hydrocarbon (HC) emissions reduced by 22% with respect to diesel. Additionally, carbon dioxide (CO2) was lowered by 6.9% because of combustion in hydrogen inflow. However, nitrogen oxide (NOx) emission increased by 17.1% due to elevated combustion temperatures from hydrogen enrichment, consistent with the Zeldovich framework. The research shows that hydrogen-enriched fish oil biodiesel (B20) improves fuel economy while decreasing important pollutants (CO, HC, and CO2), but increases NOx emissions. For practical application, exhaust after-treatment methods may be necessary to reduce NOx. These results point to a dual-fuel strategy using fish oil biodiesel and hydrogen for cleaner, more sustainable combustion in diesel engines.