A team of researchers from Beijing University of Technology has published a paper in the journal Fuel that evaluates the effectiveness of four load control strategies for an ammonia-hydrogen dual fuel Miller cycle spark ignition engine in a hybrid system.
The four strategies are throttle, ammonia-hydrogen ratio, air-fuel ratio, and variable valve timing.
The engine, which has a compression ratio of 10.7, was modified with a set of hydrogen common rail and ammonia common rail installed on the intake manifold to enable the controllable supply of ammonia and hydrogen.
The team noted that in the 1960s, GM conducted a study on the performance of ammonia combustion engines and found that they were significantly less thermally efficient than gasoline-fueled engines. However, hydrogen burns quickly, has a wide flammable limit, and has low ignition energy, making it an ideal additive to ammonia.
The researchers found that the throttle strategy provides the widest output range, with a maximum BMEP of 7.4 bar, up from a minimum of 1 bar. The ammonia-hydrogen mixing ratio strategy is ideal for cold start conditions, as it fully utilizes the good combustion characteristics of hydrogen while minimizing the amount of hydrogen used in the heat engine process.
The air-fuel ratio strategy provides the highest thermal efficiency, with a maximum BTE of nearly 40%. It meets the energy-saving demand in the series hybrid mode’s single-point working condition.
The variable valve timing strategy allows for switching between BMEP of 3.5 bar and 6.5 bar while maintaining a BTE above 33%. The valve timing strategy not only provides a wider load adjustment range but also maintains high thermal efficiency, according to the researchers.
The findings have the potential to impact the automotive industry significantly. Ammonia-hydrogen dual fuel engines can significantly reduce greenhouse gas emissions, and the evaluated load control strategies can increase engine performance and efficiency.
The research’s challenges include the need for more comprehensive testing and verification of the findings, as well as the need for the development of suitable infrastructure for the mass production and distribution of ammonia fuel.
Overall, the Beijing University of Technology’s research has shown promising results in the development of efficient and clean dual fuel engines, contributing to the global effort to combat climate change.