Coaxial injectors are used for the injection and mixing of propellants
H-2/O-2 in cryogenic rocket engines. The aim of the theoretical and e
xperimental investigations presented here is to elucidate some of the
physical processes in coaxial injector flow with respect to their sign
ificance for atomization and mixing. Experiments with the simulation f
luids H2O and air were performed under ambient conditions and at eleva
ted counter pressures up to 20 bar. This article reports on phenomenol
ogical studies of spray generation under a broad variation of paramete
rs using nanolight photography and high-speed cinematography (up to 3
x 10(4) frames/s). Detailed theoretical and experimental studies of th
e surface evolution of turbulent jets were performed. Proof was obtain
ed of the impact of internal fluid jet motions on surface deformation.
The m = 1 nonaxisymmetric instability of the liquid jet seems to be s
uperimposed onto the small-scale atomization process. A model is prese
nted that calculates droplet atomization quantities as frequency, drop
let diameter, and liquid core shape. The overall procedure for impleme
nting this model as a global spray model is also described and an exam
ple calculation is presented.