<p>In this study, we injected liquid ammonia in a constant volume chamber and observed the changes of the spray morphology and propagation characteristics under various chamber pressures. The constant volume chamber had a 100 × 100 × 100&#xa0;mm³ inner volume and a multi-hole injector was put at the top of the chamber. The chamber pressure was controlled by nitrogen gas and set to 10 bar and 70 bar at constant temperature of 100&#xa0;°C. The spray morphology was captured by a high-speed camera with 9,000&#xa0;fps and 10&#xa0;μs exposure time. The spray morphology shows a jet shape at the low chamber pressure because the momentum of ammonia is high enough to push out nitrogen gas. An entrainment region opposite to the mainstream of the jet at the tip was observed. Diluted ammonia was also observed around the jet in the influence of atomization from flash boiling at the jet morphology. When the chamber pressure was increased to 70 bar, the liquid ammonia was dispersed to radial direction and formed a cone shape morphology due to high resistance of the ambient nitrogen. Clear ammonia morphology was observed around the spray compared to the jet shape turns out to be a non-flash boiling condition.</p> Graphical abstract <p></p>