Multi-hole liquid ammonia spray collapsing behaviors: Morphologies, collapsing time, and region diagram

The flash-boiling and collapsing behavior of low-boiling-point liquid ammonia multi-hole spray can influence the efficient application of liquid ammonia on internal combustion engines. In order to investigate the mechanism and boundary conditions for liquid ammonia multi-hole spray to collapse, the macroscopic morphology and liquid cross-sectional distribution of liquid ammonia multi-hole spray under different ambient temperatures and pressures are recorded by schlieren high-speed photography and laser sheet Mie-scattering method, and the changes of several spray characteristic parameters such as spray tip penetration, spray angle, and cross-sectional area are obtained. Three different spray collapsing modes are defined: early collapsing, late collapsing, and non-collapsing. The increase of collapsing degree caused by the rise of ambient temperature and the decrease of ambient pressure results in earlier plume merging, accelerated penetration, and a reduced spray cross-sectional area. The time point of spray accelerating penetration, which is gradually advanced with the increase of spray collapsing degree, is defined as collapsing time, and an empirical correlation is proposed to predict the collapsing time under different ambient conditions. Based on the experimental phenomenon, the different spray collapsing modes and behaviors under different ambient conditions are summarized and analyzed, and the transition of spray collapsing mode under different ambient temperatures and pressures is shown by a region diagram.