Characterizing Cryogenic Jet Flames: Insights into Droplet Dynamics

Recent research has focused on the dynamics of cryogenic jet flames, particularly in the context of rocket-type combustors. The study titled "Droplet size and velocity measurements in a cryogenic jet flame of a rocket-type combustor using high speed imaging" by Nicolas Fdida, Lucien Vingert, Arnaud Ristori, and Yves Le Sant explores the atomization process in these flames, which is crucial for understanding combustion efficiency and performance in rocket engines.

The primary objective of the research was to characterize a liquid oxygen (LOX) spray in a gaseous hydrogen (GH2) environment under reacting conditions. The authors utilized high-speed shadowgraph imaging techniques to measure droplet sizes and velocities within the combustion chamber. This method was chosen due to the limitations of laser-based drop size techniques, which often struggle with low validation data rates in the breakup region where liquid particles are not spherical.

The experiments were conducted on the Mascotte test bench at Onera, where the LOX spray characteristics were analyzed. The study compared the reacting case with a cold flow test using gaseous helium (He) instead of GH2, allowing for a qualitative assessment of the spray dynamics.

The findings revealed that the velocity of the dispersed phase in reacting conditions could be accurately obtained using two different imaging methods applied to the same shadowgraphs. The results included correlations between droplet size and velocity, highlighting the influence of the flame on droplet size evolution. These insights are significant for improving the design and efficiency of cryogenic rocket engines, which are increasingly used in modern space exploration.

For further details, the full paper can be accessed at arXiv: arXiv:2408.17132.