【作者】 易朋兴；

【导师】 杨叔子； 杜润生；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 混合操作是固体火箭发动机制造的重要工序,而立式捏合机是完成固体推进剂混合工艺的关键设备。针对固体推进剂混合特性及混合要求,本学位论文采用理论研究与工程实践相结合的办法,以立式捏合机为研究对象,综合运用微分几何学、流变学以及随机过程理论等数理手段,以计算机数值模拟以及工程实验分析为研究工具,进行了立式捏合机混合机理与设计方法及有关关键技术研究。首先,详细分析了固体推进剂混合特性以及混合要求,提出立式捏合机设计过程中需要解决的几个关键问题。分析立式捏合机的工作原理,确定了立式捏合机性能分析与评价指标,为后一步研究工作的进行奠定基础。其次,分析立式捏合机桨叶的运动特性,确定立式捏合机桨叶三维造型方法;运用计算流体力学理论和有限元分析工具,建立立式捏合机混合过程有限元分析物理与数学模型,确定数值模拟的边界条件,完成混合过程的数值模拟;对压力场、速度场以及粘度分布场等模拟结果进行分析,由此确定立式捏合机混合过程数字分析与预测方法。再次,通过理论分析与数值模拟,深入研究了搅拌桨叶传动比、螺旋角以及设备的混合间隙等关键结构参数对立式捏合机混合性能的影响,提出这些参数的选用范围与设计准则。研究结果表明:搅拌桨叶公转与自转角速度比值越小,立式捏合机的混合性能越好;当空心桨叶螺旋角取42°~48°范围内的值时,立式捏合机具有最佳的混合性能;混合间隙值越小,搅拌桨壁面和混合锅锅壁对物料的拖拽作用越明显,设备的混合能力越强;各类间隙相等时,立式捏合机具有较好的混合性能。接着,改变转向、转速、固体组分含量等工艺参数条件,进行立式捏合机混合过程数值模拟与分析,研究它们与设备混合性能的关系,通过混合均匀性工艺实验,研究工艺参数与被混物料混合均匀性的关系,并对部分仿真结果进行了验证,由此提出设计与制造过程中相关问题的解决手段。研究结果表明:非周期性地调整搅拌桨叶转向,有助于提高立式捏合机的混合效率,改善被混物料的混合均匀性;转速越高,立式捏合机的混合能力越强,混合效率越高,产品的混合均匀性越好,但对设备工作能力要求越高;适当增大固体组分含量有助于改善立式捏合机的混合性能。最后,对立式捏合机系统可靠性分析、评估与改善方法进行了系统、深入的研究。在假定可靠性信息确定的前提下,以立式捏合机及其子系统的结构与功能分析为基础,建立系统与子系统的可靠性分析方法,并以状态监测子系统为例对该方法进行验证与分析。由于立式捏合机系统及其零部件在试验数据匮乏以及可靠性信息存在不确定性,论文提出一种基于贝叶斯理论、考虑统计不确定性影响的零部件与系统可靠性评估方法,工程实例表明该方法具有一定的先进性。在上述研究的基础上,提出立式捏合机可靠性、安全性改善方法与手段。工程实例表明,文中所提的系统可靠性分析与评估方法对立式捏合机可靠性设计与分析具有指导意义。本课题的研究为立式捏合机的设计、制造与使用提供理论依据和指导方法,不仅对固体推进剂混合设备技术的发展和完善具有重要的理论意义,而且将这些研究成果直接应用生产实践具有重要的现实意义和实用价值。更多还原

【Abstract】 Mixing operation is an important procedure of solid propellant manufacture, and the vertical kneading mixer is the key device to fulfill this procedure. In this dissertation, according to differential geometry, rheology, stochastic process theory and computational fluid dynamics (CFD), some key techniques existing in the design of vertical kneading mixers and performance analysis are systematically investigated by combining theoretical analysis with engineering practice.Firstly, some crucial problems existing in the design process of the vertical kneading mixers are proposed by analyzing the material characteristic of solid propellant and its mixing requirements. Then, the configuration and operating mechanism of the device are investigated. On the basis of the results mentioned above, methods and indices to analyze and evaluate the performance of the vertical kneading mixers, namely torque, pumping capacity, mixing efficiency, reliability and etc, are also presented.Secondly, methods to numerically simulate and analyze the fluid field in the mixing tank of the vertical kneading mixers are proposed by means of application geometry, rheologic theoretic and finite element methods. The methods include developing 3D modeling process of the kneading blades by analyzing the transmission characteristics of the self-rotating speed and the planetary revolution speed of them, establishing the physical and mathematical models of the flow field in the mixing tank of vertical kneading mixers, determining the boundary conditions of numerical simulation, and deeply investigating the characteristics of velocity field, flow pattern, pressure distribution and viscosity distribution of the mixing field numerically simulated by means of CFD software such as ANSYS CFX10.0.Thirdly, the selecting ranges and design rules of some key structural parameters are proposed by investigating their influence on the vertical kneading mixers via numerical simulation and theoretical analysis. The influence of the ratio of the planetary revolution speed to the self-rotating speed of the hollow kneading blade is studied at first, the studied results show that better mixing performance can be achieved if the speed ratio is designed to be lower enough. The helix angle of the kneading blade is then investigated, and the results illustrate that the preferable torque characteristic, higher pumping capacity and steady shearing rate can be achieved when the value of the helix angle of the hollow kneading blade is chosen between 42°and 48°. Also, the investigation of the mixing clearance shows that small mixing clearance can improve the mixing performance of the vertical kneading mixers, and that the lowest power consumption can be achieved if diversified mixing clearances have the same value when the other parameters are determined.Furthermore, to investigate the relationship of the processing parameters and the mixing performance of the vertical kneading mixers, numerical simulation models diversified with different processing parameters which include rotating direction of the kneading blades, rotation speed, and solid constituent proportion in the mixtures, are established. The mixing uniformity experiments are then designed to investigate the influence of the processing parameters on the mixing uniformity of the mixture, and some simulating results can be validated by them. Research results show that favorable mixing efficiency can be achieved if the rotating directions of the kneading blades are altered non-periodically, and that the mixing uniformity of the mixture and the mixing efficiency of the devices arise when the rotation speed is increased. Also, it is advantageous for improving the mixing performance of the mixing devices to increase the solid constituent proportion in the mixtures properly.Finally, methods and techniques to analyze, evaluate, and optimize the system reliability of the vertical kneading mixer are studied in detail. On the assumption that all reliability data , for example, the life cycle of a component, are determinate, a method to analyze the system reliability of the devices and their sub-systems is established, and this procedure is illustrated by using it to solve the reliability problem of the condition monitoring system for the vertical kneading mixers. Nevertheless, in the engineering practice, the test data of the vertical kneading mixers and their components are deficient and the reliability estimate information is uncertain. With consideration of this matter, reliability estimate methods of the vertical kneading mixer and its components are proposed by means of reliability mathematics and Bayesian methods. Application cases are used to illustrate these procedures. In addition, methods to enhance the reliability and safety of the vertical kneading mixer are presented due to forenamed studies. Engineering applications indicate that the system reliability analyzing, estimating and optimizing methods proposed in this dissertation are significant for reliability design of the vertical kneading mixer.The achievements of this dissertation provide significant theoretic foundation and guidance for the development of the optimum design, manufacture and operation of the vertical kneading mixer. Also, it is practical and valuable to apply these achievements to the solid propellant mixing processes.更多还原