Novel heavy duty engine concept for operation dual fuel H2–NH3

A prior paper has presented a novel design of a heavy duty truck engine fuelled with H2. In this design, the customary in-cylinder Diesel injector and glow plug are replaced with a main chamber fuel injector and a jet ignition pre-chamber. The jet ignition pre-chamber is a small volume that is connected to the in-cylinder through calibrated orifices accommodating another fuel injector and a glow or a spark plug that controls the start of combustion. This design permits to operate the engine in four different modes: traditional compression ignition (CI), diffusion, Diesel-like (M1); mixed gasoline/Diesel-like (M2); traditional spark ignition (SI), premixed, gasoline-like (M3); premixed, homogeneous charge compression ignition HCCI-like (M4). In the mode diffusion with jet ignition (M1), an injection occurs in the jet ignition pre-chamber before the main chamber fuel is injected and the engine operates therefore mostly Diesel-like. In the mode mixed diffusion/premixed Diesel/gasoline-like (M2) an injection occurs in the jet ignition pre-chamber after only part of the main chamber fuel is injected and mixed with air. In the mode premixed with jet ignition (M3), an injection occurs in the jet ignition pre-chamber after the main chamber fuel is injected and mixed with air and the engine operates gasoline-like. Finally, in the mode premixed without jet ignition (M4), no injection occurs in the jet ignition pre-chamber and the engine operates HCCI-like. Modelling results have already been presented and discussed with H2 as the main chamber and pre-chamber fuel. This paper considers the option to accommodate a second main chamber injector that will inject the NH3 that will then burn in air thanks to the hot combusting gases from the combustion of H2 and air using the modes M1 and M2 described above. The mode M3 also of interest is not considered here. First results of simulations show the opportunity to achieve better than Diesel fuel energy conversion efficiency thanks to the reduced heat losses of the “cold burning” NH3 and suggest to perform the experiments needed to further support the findings.

► NH3 may be the best option as a hydrogen carrier.
► NH3 may be burned efficiently Diesel-like with the support of H2.
► The proposed design permits fuel conversion efficiencies above 45%.
► NOx reduction is the major problem of the technique.