This paper investigates further development of a diesel-hydrogen dual fuel concept of engine of passenger car size via hydrotreated vegetable oil (HVO). The diesel-hydrogen concept significantly decreases tailpipe emission of CO2 and allows utilization of hydrogen, which has a great potential for temporary storage of excess of energy from renewable sources with fluctuating power. Moreover, benefits of hydrogen combustion as a main or supplementary fuel might initiate a gradual development of hydrogen infrastructure. An option of a diesel fuel only operation of the dual fuel engine might overcome one-sided dependence on the hydrogen infrastructure, as it is in case of a fuel cell or mono fuel vehicles. Furthermore H2 purity requirements is lower than that for fuel cells. The analysis consists of experimental and simulation parts. Experimental results were obtained on a single cylinder research compression ignition engine with a bore of 85 mm and piston stroke of 90 mm with optimized compression ratio. The engine is equipped with a diesel fuel direct injection common rail system and port fuel injection of hydrogen. The maximum observed hydrogen share reaching 98% by energy. Based on experimental results a steady state performance and emissions maps of a turbocharged four cylinder hydrogen – diesel dual fueled engine were compiled. Peak of performance achieves 83 kW at 4000 rpm. A particular implementation of a dual fuel hydrogen – diesel engine in a passenger van in a WLTP driving cycle was simulated. Simulations showed a potential of almost 70 percent driving cycle CO2 emissions reduction for the hydrogen-diesel dual fuel concept, compared to the pure diesel operation. Vehicle range with a reasonable hydrogen storage exceeds 460 km. The level of hydrogen share in dual fuel diesel-hydrogen engine is mostly limited at low loads and speeds by the low chemical efficiency of combustion and retardation of combustion. Low loads and speeds are typical operation modes of engine of passenger cars, therefore improving the parameters at these operation modes highlights the effects of dual fuel operation. HVO enables an increase of hydrogen share and further decrease of CO2 emission, while other energetic and emission parameters can be improved or unchanged. The analysis was based on experiments performed on the single cylinder engine mentioned above. HVO provides better ignitibility, which is more pronounced at cold conditions, higher cetane number and zero aromatic content. These parameters lead to the higher possible share of hydrogen at low loads, while the chemical efficiency of combustion is not worsened in comparison with the use of the regular diesel fuel. Another benefits of-hydrogen dual fuel operation compared to the pure diesel one are decreasing of CO, unburned hydrocarbon and significant reduction of particle emissions (expressed as PN). HVO highlights these advantages of dual fuel hydrogen operation. Combination of HVO and hydrogen has a potential to reduce the tail pipe emission of CO2 from combustion engines to the levels below the future regulations requirements. Furthermore, well to wheel emission of CO2 is reduced by production of both HVO and hydrogen from renewable sources.

Ing. Ivan Bortel, Czech Technical University in Prague, CZECH REPUBLIC Dr.-Ing. Jiří Vávra, Czech Technical University in Prague, CZECH REPUBLIC Prof. Dr.-Ing. Michal Takáts, Czech Technical University in Prague, CZECH REPUBLIC