Effect of the exhaust gas recirculation ratio and the energy share of the gaseous fuel on basic operating parameters and exhaust emissions in a dual-fuel compression ignition engine operating on natural gas

For many years in the Department of Automobiles and Internal Combustion Engines at Kazimierz Pulaski University of Technology and Humanities in Radom there are carried out investigations on dual-fuel combustion system in a compression ignition engine. The majority of literature reviews, as well as the authors' studies were limited to the older generation engines, i.e. naturally aspirated engines that are not equipped with the exhaust gas recirculation system. The paper presents results of investigations on a turbocharged engine equipped with an EGR system. The authors tried to assess the effect of the recirculation ratio on engine performances (mainly the mean effective pressure and the engine overall efficiency as well as exhaust emissions). The obtained results indicate that it is possible to apply high energy shares of the gaseous fuel maintaining at the same time high engine overall efficiency and visibly reducing the particulate matter emission. It was also noticed that the NOx emission may be visibly reduced introducing the exhaust gas recirculation system. Unfortunately, an increase of the gaseous fuel energy share results in slightly higher hydrocarbon and carbon monoxide emissions.