Measurements of Liquid Ammonia Sprays Using the ECN Spray M Injector with Injector-To-Injector Comparisons

Liquid ammonia is receiving increasing attention as a carbon-free energy carrier for use in internal combustion engines, particularly in the maritime sector. While gaseous ammonia injection has been widely studied, liquid-phase injection offers potential advantages in terms of fuel-air mixing and power density, but introduces challenges associated with evaporation, flash boiling, and spray collapse. This study presents a comprehensive experimental investigation of liquid ammonia sprays generated using a multihole ECN Spray M injector and a commercially available injector. Experiments were conducted in a nitrogen-filled constant volume chamber over a wide range of ambient pressures (1-15 bar) and at two injection pressures (100 and 150 bar). High-speed shadowgraph imaging was used to characterize spray morphology and macroscopic spray parameters, including tip penetration length, tip penetration speed, and spray cone angle, following the SAE J2715 standard. In parallel, instantaneous mass flow rate was measured using a pressure-based technique upstream of the injector, enabling quantification of injected mass under the tested conditions. The results show that ammonia spray behavior is strongly governed by the saturation-to-ambient pressure ratio (r _p), with three distinct regimes identified: drag-dominated, evaporation-dominated, and flare flash boiling. Compared to the commercial injector, the ECN Spray M injector exhibits an earlier onset of spray collapse at lower r _p values, attributed to differences in injector geometry, particularly the longer counterbore promoting in-nozzle cavitation. Despite these morphological differences, the mass flow rate and total injected mass from the ECN Spray M injector were found to be largely insensitive to ambient pressure, in contrast to previous observations with other injector designs. This work presents the first open-literature data set of mass flow rate and high-resolution macroscopic spray parameters for the multihole ECN Spray M injector under flashing conditions. The results provide valuable insights into injector design effects on ammonia fuel injection and offer a robust experimental benchmark for future computational model validation.