Research On Mixing Of Solid Propellant Slurry In Tanks Of The Vertical Kneaders

Mixing process is one of the key processes for the production of solid propellants. The mixing performance of the solid propellant slurry directly affects machining properties, mechanical properties and combustion characteristics of the propellants. Mixing, expressed as mapping in mathematics, is a special form of fluid flowing, and it can be described by Lagrangian Method or Eulerian Method.According to the axial symmetry of geometry of the mixing domain of the fluid dynamics system in the mixing tank of a vertical kneader, definitions of Ergodicity Rate, Mixing Rate, Mixing Time, etc., were presented in the dissertation. The influences of parameters of geometry and kinematics of the kneader on ergodic and mixing performance of the system were analyzed. By introducing impact factor of crossing, the influences of crossing on the mixing performance were quantitatively studied, and results revealed that ergodicity and mixing are different processes of a system, of which, the continuous changes of velocity directions of the trajectory of the fluid in ergodic process accelerate the mixing process.A method of constructing fluid dynamics system of mixing based on Smale Horseshoe Mapping Model was put forward. The influences of parameters of geometry and kinematics of the kneader on Mixing Rate and Mixing Time of the system were analyzed. Results show that there is such an optimal range of speed ratio of rotation and revolution of the hollow blade for certain parameters of geometry and kinematics of the kneader that makes the fluid dynamics system hold strong chaotic properties. With assumption of fluid dynamics system being quasi-static, the characteristics of stream-function distributions of the two-dimensional systems of single screw blade and that of double screw blades were analyzed. Results show that double screw blades with different revolution speeds can make changes of the shapes of the trajectory in the mixing tank, and area of the zero shear rate region decreases as a result, which prohibits the generation of regular islands.By adopting Dynamic Mesh Model, mesh auto-updating with the planetary motion of the screw blades was realized after source code, based on User Defined Functions, being edited, compiled and hooked. Assume that the solid propellant slurry, which was prepared following the ordinary mixing process and reached some standard of mixing uniformity, is the continuous phase of a mixture of a fluid dynamics system, then the influences of parameters of geometry and kinematics of the kneader on the movement course of solid phase particles of the solid propellant slurry were analyzed by the use of Discrete Phase Model, and the movement characteristics of solid phase particles of the slurry was revealed. Moreover, the chaotic properties of the solid propellant sluny dynamics system in the mixing tank of the kneader was analyzed by the use of Eulerian Model, and the mixing mechanism of the solid propellant slurry in a complex mixing domain was revealed.Volume-weighted Intensity of Segregation was defined, and it was employed to compute and analyze the deviation of the tested density from the average value of the solid propellant slurry, then the evaluation of mixing uniformity of the slurry was obtained. Major parameters of the mixing process and their significant levels affecting the mixing performance of the slurry were also obtained by means of range analysis and variance analysis of the tested results of mixing uniformity of the solid propellant slurry.