Faithin Omaha eBook Collection

Download or read book Numerical Investigation of the Influence of the Injector Geometry on Flashing Behavior written by Lionel [Verfasser] Gury and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: So-called Green Propellants for in-space propulsion gained attention during the last years and are a growing field of research due to the anticipation of the ban of traditional toxic liquid monopropellants. Liquid propellants based on highly energetic inorganic salt Ammonium Dinitramide (ADN) were identified as a possible alternative. Prior to the design of new families of thrusters using new propellants, knowledge has to be gained the injection of propellants under near vacuum conditions involves intense phase change which can be problematic in the case of the injection of a dissolved salt. Injection tests were carried out at DLR Lampoldshausen. Eight different geometries were tested with water and saline solution in order to identify the parameters driving the spray behavior.The aim of this study is to simulate with the help of computational fluid dynamics software, the flow behavior in the injector, and particularly the interphase mass transfer. Secondly, parameters influencing the shattering of the spray and the internal flow behavior are identified.The simulations were carried out for four different injectors with different geometries and under different temperatures. The phase change in the injectors was modeled from the Rayleigh-Plesset equation for bubble growth and a test case was validated against experimental results. The results of the simulations indicated that the pressure drop in the injector reached the saturation pressure under certain conditions, which led to cavitation and subsequently to the choking of the injector. Qualitative comparison with experimental data showed that the shattering of the spray in a two phase effluent was coincident with the cavitation in the injector nozzle. It was also established that not only the pressure loss, but also the mechanism of pressure loss in the injector had an important influence on the spray behavior.*****So-called Green Propellants for in-space propulsion gained attention during the last years and are a growing field of research due to the anticipation of the ban of traditional toxic liquid monopropellants. Liquid propellants based on highly energetic inorganic salt Ammonium Dinitramide (ADN) were identified as a possible alternative. Prior to the design of new families of thrusters using new propellants, knowledge has to be gained the injection of propellants under near vacuum conditions involves intense phase change which can be problematic in the case of the injection of a dissolved salt. Injection tests were carried out at DLR Lampoldshausen. Eight different geometries were tested with water and saline solution in order to identify the parameters driving the spray behavior.The aim of this study is to simulate with the help of computational fluid dynamics software, the flow behavior in the injector, and particularly the interphase mass transfer. Secondly, parameters influencing the shattering of the spray and the internal flow behavior are identified.The simulations were carried out for four different injectors with different geometries and under different temperatures. The phase change in the injectors was modeled from the Rayleigh-Plesset equation for bubble growth and a test case was validated against experimental results. The results of the simulations indicated that the pressure drop in the injector reached the saturation pressure under certain conditions, which led to cavitation and subsequently to the choking of the injector. Qualitative comparison with experimental data showed that the shattering of the spray in a two phase effluent was coincident with the cavitation in the injector nozzle. It was also established that not only the pressure loss, but also the mechanism of pressure loss in the injector had an important influence on the spray behavior.