Droplet collision of hypergolic propellants

Abstract

In the present mini‐review, droplet impacting on a liquid pool, jet impingement, and binary droplet collision of nonreacting liquids are first summarized in terms of basic phenomena and the corresponding nondimensional parameters. Then, two representative hypergolic bipropellant systems, a hypergolic fuel of N,N,N′,N′‐tetramethylethylenediamine (TMEDA) and an oxidizer of white fuming nitric acid (WFNA) and a monoethanolamine‐based fuel (MEA‐NaBH4) and a high‐density hydrogen peroxide (H2O2), are discussed in detail to unveil the rich underlying physics such as liquid‐phase reaction, heat transfer, phase change, and gas‐phase reaction. This review focuses on quantifying and interpreting the parametric dependence of the gas‐phase ignition induced by droplet collision of liquid hypergolic propellants. The advances in droplet collision of hypergolic propellants are important for modeling the real hypergolic impinging‐jet (spray) combustion and for the design optimization of orbit‐maneuver rocket engines.

Hypergolic Ignition by Off-Center Binary Collision of Monoethanolamine-NaBH4 and Hydrogen Peroxide Droplets

“…To imitate such type of mixing, the authors established an experimental apparatus where a pair of freely moving droplets collide and mix with each other. The ignition of bipropellants of white fuming nitric acid (WFNA) and N,N,N ′ ,N ′ -tetraacetylethylenediaminemine (TMEDA) was first examined as reported in [4,[8][9][10]. The development of the ignition process was fully interpretated, and the dependence of ignition delay on collisional dynamic parameters, i.e., the Weber number (We, ratio of inertial force to droplet surface tension), droplet size ratio (∆), and impact parameter, (B, measuring the degree of off-center collision effect, where B = 0 represents head-on collision and 0 < B < 1 represents the off-center collisions) was explicitly established.…”