【作者】 杨福馨；

【导师】 王生泽；

【作者基本信息】 东华大学 ， 机械设计及理论， 2011， 博士

【摘要】 在粘性流体灌装计量充填中,对于计量精度要求越来越高。特别是贵重的食品、药品和保健品计量精度要求很高。而影响计量精度的关键在于计量充填机构的充填出流口处的断流。断流指流体在灌装机械中进行计量充填时完成一个单元流体物料的结束过程。流体物料在计量充填机构充填动作完成后往往产生粘连,使流体物料单元之间或流体物料与充填出流口之间不能断开,有时导致物料粘附在包装封口处影响封口质量,粘稠流体的充填更为突出。分析表明影响粘稠流体在灌装计量充填的断流效果关键因素之一是充填管口特性。本研究问题就是探索充填管口特性对粘性流体断流效果的影响理论与技术问题。粘性流体在充填管口内的压力分布及其变化,将影响到断流。充填管口内流体的压力分布和变化与管口孔形有直接的关系。试验表明,用不同的充填管口进行计量,充填口处产生压力降,压力降小的充填管口更有利于断流。这是因为压力降小,使流体物料在管口内滞留的时间短,从而有利于断流。而在出流口处,因施压而使流体流出进行充填,其流体分别产生层流、紊流和流层能量损失。这些流动特性决定了出口处液滴的形成问题,进一步影响到流体充填时的断流。影响断流的因素很多,包括孔径,充填机构挤出压力,流体在孔口壁处的表面张力,流体粘度和温度,流体的毛细管现象、充填管出流孔口结构与形状等。本文的研究具有较大的理论性。建立粘性流体的动表面张力模型和断流管径数学模型,并研究流体特性与出流计量机构流通管径之间的内在关系,是一种全新的研究探索。借助流体力学和机械传动已有的三种研究方法。理论分析法、实验研究法、数值计算法。本文的研究主要采用理论分析法与实验研究法相结合进行,可丰富现有的流体机械理论和灌装机械设计理论。第一章将流体断流研究相关理论分成两个阶段进行文献综述。这两个阶段就是流体断流相关的流体力学研究历史回顾和流体断流相关的当代研究。前一阶段主要是流体力学的研究,其中包含一些流体断流的局部内容；后一阶段形成了一些与流体断流相关概念,但是都没有系统的研究。同时论述了课题拟研究的问题、研究的方法和研究的学术意义与应用价值。第二章根据雷诺实验的研究方法和流体在管道中的流动特性,研究分析了流体流经表面对圆管层流特性的影响,管口流体出流特性,断流的物理意义,流体单元受力等问题。然后设计了粘性流体断流实验系统(装置),最后根据出流管口粘性流体的平衡问题建立了粘性流体断流的数学模型。分别得到了铅垂方向圆形出流管口(喷嘴)在动力学条件下断流管径的数学模型和静力学条件下断流管径的数学模型,按雷诺数来界定,前者适应高速充填包装,后者适应于中低速充填包装。第三章利用能量法对粘性流体在流动中的损失进行了研究。分别分析了对理想流体、实际流体流动中的能量平衡,圆管内层流沿程损失、圆管内紊流沿程损失、圆管内流体沿程损失和变截面内流体沿程损失问题,同时研究了不同变截管孔的当量直径。它们都会影响到粘性流体在流动中的断流,其决定因素雷诺数和能量。。第四章主要研究不同孔口出流时的压力、出流状态、不同出流孔口形状对粘性流体断流的影响和比较。重点研究均压方孔间隙流动,均压平行端面的径向流动,孔口间隙与功率损失的关系,出流管口对粘性流体断流效果的影响。这些都影响到粘性流体的流动特性和断流,分析结论表明圆孔比方孔更利于断流。第五章对试验步骤、方法、过程进行了设计,确定四种不同粘度流体物料进行试验,利用建立的数学模型式进行断流管径试验,得到相关数据,并对试验数据进行统计、整理和分析。最后通过对数学模型的线性化分析,验证了流体断流管径数学模型的可靠性。第六章对所研究的粘性流体断流理论与技术进行总结与展望。对研究工作进行系统总结,对进一步深化工作予以展望。主要从理论分析、试验两方面进行总结,并归纳出本文研究的创新点,同时对断流管径相关的结构、内部形状及高速灌装的定量分析进行展望。更多还原

【Abstract】 In the process of measurement and filling of packing viscous fluid, the accuracy of the measurement has to meet more demads. Especially for costly food, medicines and health protection, the accuracy of the measurement is very high.Flow-stop is the process of fluid form a unit fluid materiel by metering and filling in packing machinery.Fluid materiel usually make adhesion after the completion of metering and filling.Because of this,it can not disconnect between units of fluid materiel,or between fluid materiel and filling orifice entrance.Some times,it make the materiel glue to the seal of packaging,and impair the quality of sealing,especially for the filling of viscous fluid. The analyzed results indicate that one of the key factors of influencing the effect of flow-stop of viscous fluid in metering and filling is the characteristic of pipe orifice.This research is to explore the influence of orifice shape on the flow-stop result of viscous fluid.The pressure distribution and change of viscous fluid in filling pipe orifice will effect the flow-stop.the perssure distribution and change of fluid in pipe orifice is directly related to the shape of pipe orifice. Tests have shown that there will produce pressure drop in the pipe orifice by using different shapes of pipe orifice to meter. Filling pipe orifice with lower pressure drop is more beneficial for flow-stop.This is because lower pressure drop,shorter the residence time of materiel stay at pipe orifice,and pipe orifice is beneficial for flow-stop.And at the orifice flow,because of repeatedly pressure,fluid has flowed to fill,fluid produce laminar flow, turbulent flow and the energy loss.These flow characteristics control the formation of droplet at the exit,further effect the flow-stop of fluid while filling. There are many factors of influencing flow-stop,such as pore diameter, extrusion pressure of extender mechanism, surface tension of fluid in orifice wall,viscosity and temperature of fluid,capillary of fluid[and some other things.The research in this paper has a higher theoretical level.Buliding dynamic surface tension of fluid model and flow-stop pipe diameter mathematical model,and researching the internal relation between fluid characteristics and metering mechanism outflow pipe orifice,that is an entirely new explore.There already have three research methods,analytical method,experimental method,numerical method by the aid of fluid mechanics and mechanical rotation.This study mainly uses the combination of analytical method and experimental method,that also is a method has wide application prospects,and it can enrich content of existing fluid machinery theory and packaging machinery design theory.The first chapter discusses relative theory of fluid flow-stop into two phases,historical review of fluid mechanics research in relation to fluid flow-stop,and modern research of fluid flow-stop.The first phase mainly research fluid mechanics,include local content of fluid flow-stop.The second expound the conception of fluid flow-stop without systematic study.At the same time,this chapter elaborates on the problem,method,academically significance and application value intended to research in the task.In chapter two,accroding to the reseach method of reynolds experiment and the flow characteristic of fluid in pipe,this paper analyses the influence of fluid flow through the surface on the characteristic of pipe laminar flow,outflow characteristic of fluid at pipe orifice,physical significance of flow-stop,unit pressure of fluid and so on.And then, this paper designed flow-stop test system of viscous fluid,finally found flow-stop mathematical model of viscous fluid accroding to the balance problem of viscous fluid at outflow orifice.We get flow-stop pipe diameter mathematical model of round outflow pipe orifice on dynamical conditions in vertical direction,and flow-stop pipe diameter mathematical model on static conditions.Defined by reynolds number,the former adapted to high-speed filling packaging,the latter adapted to middle-low speed filling packaging.In chapter three,loss of viscous fluid in flowing is studied by energy method.This chapter respectively analyses the energy balance of ideal fluid and actual fluid in flowing,on-way loss of laminar flow in round tube, on-way loss of turbulent flow in round tube, on-way loss of flow in round tube, on-way loss of flow inside variable cross-section.At the same time,this chapter researches equivalent diameter of different variabe cross-section pipe hole.They all effect flow velocity and reynolds number,and the flow-stop of viscous fluid in flowing.Chapter four mainly researches outflow pressure of different pipe orifice.outflow state,influence and comparison of viscous fluid flow-stop in different shape of outflow orifice.This chapter makes a deep study of pressure equalizing square hole clearance flow,pressure equalizing parallel face radial flow,relationship between orifice clearance and power loss,influence of outflow orifice on flow-stop effect.They all influence flow characteristic and flow-stop of viscous fluid.The result showed that round hole is easier than square hole for flow-stop.Chapter five designed the experimental procedures,method and process,defined four kinds materials of different viscosity to test.To conduct flow-stop pipe diameter experiments by mathematical model,get related data,count the experimental data,collation and analysis.at last, the reliability of flow flow-stop pipe diameter is verified through the linear analysis of mathematical model.Chapter six give a summary and prospect of viscous fluid flow-stop theories and techniques.It systematically summarizes research work and give an overview of the work that hope to do but have not done.This chapter mainly summarizes from theory analysis and experiment and generalizes the innovations in the dissertation,at together,looks forward related structure of flow-stop pipe diameter,shape inside and quantitative analysis of high-speed filling.更多还原