Conversion of a 15kW diesel engine to operate in dual fuel mode with hydrogen and diesel

A 15kW diesel engine has been modified in the laboratory to operate in dual fuel combustion mode. The engine is a three-cylinder, displacement of 1 liter, fueled with diesel in its original configuration. It fulfills the emission standard by means of EGR system and three-way catalyst at the exhaust. The first system has been deactivated in the dual fuel operation mode of the engine. The engine has been modified to set three PFI injectors, facing the intake valves, in the intake manifold of the engine. The hydrogen injection is phased with the opening of the valve in the engine combustion cycle by delay units. The diesel injection with the standard ECU has been used as the start of combustion within the cylinder. The engine operation in dual fuel mode has been tested at maximum torque and power of the engine. To achieve the torque/power at several engine speeds both the quantity of diesel by the accelerator pedal position and the quantity of hydrogen adjusting the PFI injectors duration have been accordingly varied. The first constraint has been the reduction of the amount of diesel injected into the cylinder and the second one has been to prevent the autoignition or knocking problem due to high quantity of injected hydrogen. The engine performed reliably in all tested areas. The highest hydrogen energy replacement ratio (HES) achieved was 70% at low rpm and high load. At higher HES, the MAPO index began to increase. A premixed fuel equivalence ratio of 0.32 was identified as the limit beyond which hydrogen self-ignition began to occur. Regarding cylinder-by-cylinder variation, different fillings of the three cylinders were noted, which directly influences the cylinder equivalence ratio and combustion performance of each cylinder.