The single-cylinder engine in the Motorlab at NTNU is now operational with direct injection of ammonia and biodiesel. The diesel fuel system has been upgraded, improving the reliability and stability of the injection pressure. The GDI injection has been synchronized to the engine encoder, offering full control of injection timing with high precision.

Figure 1: Single-cylinder engine with ammonia and diesel injection installed.

Initial tests have been performed with injection of ammonia and biodiesel yielding the first combustion results. The data has been analyzed and is presented in a Work-in-Progress Poster at the International Symposium on Combustion in Vancouver in July 2022. The tests include a parameter sweep of the injection timing of ammonia between -18° and -8° after top dead center (aTDC), with a fixed injection timing of the biodiesel pilot at -12° aTDC. The energy fraction of ammonia was held constant at 67 % and two air intake temperatures at 22°C and 55°C were tested. The test case is however not optimized, only providing early indications of the effect of ammonia injection timing on emissions and performance. The results show that the earliest injection timings of ammonia yield the highest thermal efficiency, while monotonically decreasing with delayed ammonia injection timings. CO is increased for earlier injections of ammonia, which could be due to the larger portion of liquid ammonia evaporating prior to the biodiesel pilot injection, which cools the charge and reduces the combustion efficiency of the biodiesel fraction. CO is also observed to be higher for higher intake temperatures for the early injections of ammonia, which could also be due to a higher amount of ammonia being evaporated compared to the cold intake case, cooling the charge.

Figure 2: Break thermal efficiency with NH3 and biodiesel for different injection timings of ammonia.

The following step in ACTIVATE WP1 is to perform an extensive parameter study of ammonia and biodiesel combustion, studying emissions of nitric oxides and nitrogen dioxide, combustion efficiency, engine performance, and ammonia injection characteristics.