A team at Beijing University of Technology has assessed four load control strategies for an ammonia-hydrogen dual fuel Miller cycle spark ignition engine in a hybrid system. The strategies evaluated include throttle, ammonia-hydrogen ratio, air-fuel ratio, and variable valve timing. Their findings are detailed in a paper published in the journal Fuel.
This Miller cycle engine with a compression ratio of 10.7 was equipped with a set of hydrogen common rail and ammonia common rail installed on the intake manifold, allowing for controllable supply of ammonia and hydrogen.
While GM found ammonia combustion engines to be less thermally efficient than gasoline-fueled engines during the 1960s, researchers noted the fast-burning, wide flammable limit and low ignition energy of hydrogen make it an ideal additive to ammonia.
The team discovered that the throttle strategy provides the widest output range, with BMEP increasing from a minimum of 1 bar to 7.4 bar. The ammonia-hydrogen mixing ratio strategy is best suited for cold start conditions, fully utilizing hydrogen’s excellent combustion characteristics while minimizing its use in the heat engine process as much as possible.
The air-fuel ratio strategy offers the highest thermal efficiency with a maximum BTE nearing 40%, making it ideal for energy-saving in single-point working conditions of the engine in the series hybrid mode.
Xin et al.
The variable valve timing strategy can switch between BMEP values of 3.5 bar and 6.5 bar, and keep BTE above 33%. The valve timing strategy provides wider load adjustment ranges while maintaining high thermal efficiency.
… combining the effects of the four control strategies and the typical operating modes of the hybrid system, this study suggests that the throttle strategy is suitable for the feed mode, the VVT strategy is suitable for the parallel mode, the ammonia-hydrogen mixture ratio strategy is suitable for the cold start condition, and the air-fuel ratio control is suitable for the series mode.
—Xin et al.
Resources
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Gu Xin, Changwei Ji, Shuofeng Wang, Chen Hong, Hao Meng, Jinxin Yang, Fangxu Su (2023) “Experimental study on the load control strategy of ammonia-hydrogen dual-fuel internal combustion engine for hybrid power system,”
Fuel, Volume 347, doi: 10.1016/j.fuel.2023.128396
