Research On The Oscillation Characteristics Of Liquid-Liquid Swirl Coaxial Injector

Liquid-liquid swirl coaxial injectors are widely used in liquid rocket engines.The research on the steady-state spray characteristics of the injector is sufficient,but the research on the oscillation characteristics is lacking.In this paper,the combination of experimental and numerical simulation methods is used to study the oscillation characteristics of liquid-liquid swirl coaxial injectors and its external injector.The spray oscillation phenomenon and characteristics of the liquid-liquid swirl coaxial injector and its outer injector were studied by the test method.When the oscillation occurs,the spray pattern will periodically oscillate,and the surface wave amplitude will gradually increase during the development of the liquid film downstream,and the spray has a significant oscillation frequency.The oscillation frequency increases with the increase of the outer injector Weber number.If the outer injector We_iber number does not change,the oscillation frequency is basically unchanged.The research on the influence of Venturi tube and several key structural parameters on the oscillation characteristics was carried out.It was found that the Venturi tube and the injector worked together to cause spray oscillation.Cavitation of the Venturi tube was the excitation source of the oscillation.Under the internal mixing flow,the liquid film impacts and generates a shock wave,which affects the stability of the liquid film and results in higher oscillation frequency.The presence of the rounded exit of the outer injector makes the liquid film at the outlet thinner,which will also cause the oscillation frequency to increase,When the length to diameter ratio is large,the flow of the liquid film in the nozzle is gradually stabilized,which can weaken the spray oscillation.The larger the tangential hole area,the lower the oscillation frequency.Based on the numerical simulation method,the unsteady flow characteristics of the liquid-liquid swirl coaxial injector and its external injector were studied.The liquid film formation process,internal flow field structure and air core oscillation phenomenon in the injector were analyzed.The air core inside the outer injector is in a symmetrical periodic scaling form.