An analysis of fuel–oxidizer mixing and combustion induced by swirl coaxial jet injector with a model of gas–gas injection

Mixing and combustion characteristics of swirl coaxial jet injector for gas–liquid injection are investigated numerically with a model of gas–gas injection. The gas–liquid injector, widely used in a high-performance combustor, consists of a central oxidizer post and peripheral fuel holes for fluid injection. The gaseous oxidizer passes through a central passage and liquid kerosene is injected tangentially for annular swirl flow. Upon injection, kerosene fuel is assumed to be vaporous because it is heated up to around its critical temperature while passing through a regenerative cooling channel before its injection to the chamber. With this assumption, the process of interaction between fuel and oxidizer inside the injector can be approximated to be gas–gas interaction. In addition to the model of gas–gas injection, an actual condition with high chamber pressure is scaled down to a model condition with an atmospheric pressure for investigation of fundamental features of mixing and combustion. From the numerical results calculated with this modeling and scaling, it is found that the spreading angle of the mixture jet and flame is decreased with recess length of the oxidizer post and flame is anchored more stably with it. Momentum flux ratio is another controlling parameter for spreading angle, flame shape, and reaction.