First Study on Ammonia Spray Characteristics with a Current GDI Engine Injector

Abstract

Using carbon free energy sources is one of the keys to mitigate climate change. Hydrogen promises to be one of these carbon free energies, but its storage is difficult and expensive. Ammonia, however, is interesting as it can store hydrogen safely and can be used in combustion engines instead of hydrocarbon fuels. In this experimental work, the spray characteristics of ammonia under different air densities and temperatures were investigated in constant volume and were compared to a biofuel, ethanol, and a common fuel, gasoline. The Schlieren technique was used to capture images of liquid and liquid + vapor spray. The penetration length, the angle near the injector and the angle at half-penetration length were measured. The results show that the spray geometry of ammonia differs from that of the other fuels and that its sensitivity to air density and temperature is greater. The flash boiling condition at ambient temperature was explored for ammonia and indicated a wider spray at half-penetration length at phase change. Moreover, a semi-empirical correlation for penetration length as a function of physical parameters was found with a high accuracy for the global spray. These experimental data provide the first information about ammonia injection with a current spark-ignition GDI injector.