Resumo:
HVO and green hydrogen are highly promising alternative fuels with great potential to meet increasingly stringent environmental regulations regarding greenhouse gases emissions. In this context, this study presents an experimental analysis of the performance, combustion, and emissions of a compression ignition engine operating with HVO in dual-fuel mode, using port-fuel injection of hydrogen or compressed natural gas (CNG). For this purpose, a fully instrumented test bench was developed, and a compression ignition engine, model FPT NEF 67, was adapted to operate in dual-fuel mode, by using pilot injection of HVO or diesel and port-fuel injection of hydrogen or CNG. The experimental tests were divided into three stages: conventional operation tests with diesel and HVO separately; dual-fuel operation with diesel as the pilot fuel and injections of hydrogen or CNG separately; and dual-fuel tests with HVO as the pilot fuel and the same gaseous fuels. The results indicated that single-fuel operation with HVO presented significant advantages over diesel, such as higher combustion efficiency and fuel conversion efficiency, even without adjustments to the engine’s injection parameters. Additionally, there were reductions in CO2 emissions (an average of 3.16 %), NOx (an average of 6.63 %), as well as lower formation of HC, CO, and particulate matter. In dual-fuel operation, an increase in in-cylinder pressure was observed with the injection of H2 or CNG, regardless of the pilot fuel used. Nevertheless, both the pressure rise rate and the IMEP covariance remained close to the values observed in single-fuel operation. Increases were also observed in the maximum heat release rate and the maximum temperature in the combustion chamber, along with a longer ignition delay, longer combustion duration, and a reduction in fuel conversion efficiency. Even so, the HVO-hydrogen combination showed potential for reducing NOx and CO2 emissions, representing a viable alternative to replace diesel. Finally, implementing a programmable system to optimize injection conditions may be a strategy to mitigate efficiency losses.
