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反向旋转型双螺杆挤压机及挤压部件的设计 反向 旋转 螺杆 挤压 部件 设计

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无锡太湖学院信 机系 机械工程及自动化 专业毕 业 设 计论 文 任 务 书一、题目及专题：1、题目 反向旋转型双螺杆挤压机及挤压部件设计 2、专题 二、课题来源及选题依据 螺杆挤压机能将一系列的化工基本单元过程集中在挤压机中进行，螺杆挤出已连续生产代替间歇生产，必然有较高的生产率和较低的能耗，也已实现自动化，同时螺杆的搅拌作用业提高了混合质量这些因数加在一起，避让降低生产成本。挤压加工技术作为一种经济实用的新型加工方法广泛应用于食品生产中，并得到迅速的发展。 反向旋转型双螺杆挤出机因其具有突出的高效工作性能, 受到了食品行业的广泛重视。根据收集的相关文献, 对反向双螺杆挤压机在食品工业中的应用、发展前景、主要组成部分，以及挤压机的各项参数等进行综合的分析和论述,希望对我国反向型双螺杆食品挤压的研究与发展有益。 三、本设计（论文或其他）应达到的要求： 了解挤压机的工作原理； 4 了解挤压机的内结构； 熟练掌握反向旋转型双螺杆机压机的优缺点； 熟练绘制双螺杆挤压机的装备图，挤压部件装配图，挤压机零件图。 四、接受任务学生： 班 姓名 五、开始及完成日期：自2012年11月12日 至2013年5月25日六、设计（论文）指导（或顾问）：指导教师签名 签名 签名教研室主任学科组组长研究所所长签名 系主任 签名2012年11月12日编号无锡太湖学院毕业设计（论文）相关资料题目： 反向旋转型双螺杆挤压机 及挤压部件设计 机电 系 机械工程及自动化专业学 号： 学生姓名： 指导教师：（职称：副教授 ） （职称： ）2013年5月25目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目： 反向旋转型双螺杆挤压机 及挤压部件设计 机电 系 机械工程及自动化 专业学 号： 学生姓名： 指导教师： （职称：副教授 ） （职称： ）2012年11月25日 课题来源用于食品生产的工程实践性自拟课题。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）（1）课题科学意义挤压机是挤压加工技术的关键。 挤压加工技术作为一种经济实用的新型加工方法在食品生产中得到迅速发展。 挤压加工主要由一台挤压机一步完成原料的混炼、熟化、粉碎、杀菌、预干燥、成型等工艺, 制成膨化、组织化产品或制成不膨化的产品。 只要简单地更换挤压模具, 便可以很方便地改变产品的造型。反向型螺杆挤压机用于食品生产具有工艺简单、一机多能、生产连续化、效率高、能耗低、投资少、收效快的特点。生产出来的食品口感细腻、易消化吸收、营养成份损失少、贮藏时间长、不易产生“回生”现象、食用方便. 目前，挤压技术已经发展成为最常用的膨化食品生产技术之一。反向型双螺杆挤压机的研究与开发也势在必行。（2）反向双螺杆挤压机的研究状况及其发展前景上世纪60 年代, 开始出现了双螺杆挤压机, 并用于食品加工领域. 我国从70 年代开始研究食品挤压技术和挤压加工机械. 1980 年3 月, 北京食品研究所仿制出第一台自热式PJ ) 1 型谷物膨化挤压机. 1982 年无锡轻工业大学从法国Clext ral 公司引进一台BC ) 45 型双螺杆挤压机, 开始了对挤压加工技术的研究。与此同时, 国内许多生产厂家也先后从世界各大公司引进了先进的挤压设备。国际上有代表性的挤压机生产企业除法国Clext ral 公司外，还有美国Wenger 公司，德国的WP 公司, 意大利MAP 公司，日本的恩奴比食品有限公司，瑞士的Buchcler 公司等。在引进国外设备的同时，国内的许多厂家也先后生产了不同类型的挤压设备。反向型双螺杆挤压技术在近几年得到了迅速地发展。研究表明,反向型双螺杆挤出技术具有无法比拟的优越性能, 如物料能充分、彻底混合揉捏, 并且在反向型双螺杆挤出机运转时, 由于反向双螺杆互相啮合而具有自行擦净的功能, 避免了螺杆堵塞的物料在套筒内产生表面结焦的现象。同时反向型双螺杆挤压机还具有广泛的原料适应性的优点。反向型双螺杆挤出机因其具有突出的高效工作性能, 受到了食品行业的广泛重视。根据收集的相关文献, 对反向双螺杆挤压机在食品工业中的应用、发展前景、主要组成部分，以及挤压机的各项参数等进行综合的分析和论述,希望对我国反向型双螺杆食品挤压的研究与发展有益。 研究内容 螺杆挤压机的挤压膨化原理和结构特点 反向旋转型双螺杆挤压机的工作原理 反向旋转型双螺杆挤压机主要参数计算 反向旋转型双螺杆挤压机的总体结构设计 反向旋转型双螺杆挤压机挤压部件的设计拟采取的研究方法、技术路线、实验方案及可行性分析（1）实验方案 掌握反向旋转型双螺杆挤压机的工作原理，通过对其结构及特点的研究了解挤压机的内部结构，从而进行对挤压部件的研究和设计。（2）研究方法 通过实验了解挤压机的结构参数，对挤压部件的参数进行计算及确定，按照挤压机的结构进行装配图及挤压部件零件图的绘制。研究计划及预期成果研究计划：2012年10月12日-2012年12月31日：按照任务书要求查阅论文相关参考资料，完成毕业设计开题报告书。2013年1月1日-2013年1月27日：学习并翻译一篇与毕业设计相关的英文材料。2013年1月28日-2013年3月3日：毕业实习。2013年3月4日-2013年3月17日：反向旋转型双螺杆挤压机螺杆、机筒的主要参数计算与确定。2013年3月18日-2013年4月14日：反向旋转型双螺杆挤压机总体结构设计。2013年4月15日-2013年4月28日：部件及零件图设计。2013年4月29日-2013年5月21日：毕业论文撰写和修改工作。 预期成果：了解挤压机的工作原理、内部结构以及反向旋转型双螺杆挤压机的优缺点，熟练绘制挤压机的装配图，挤压部件的零件图。特色或创新之处 双螺杆挤压机在食品工业中应用更广泛。 反向旋转型双螺杆挤压机结构简单，更适合对高粘度食品的输送加工。已具备的条件和尚需解决的问题 设计方案思路已经非常明确，已经具备机械设计的能力和图纸处理方面的知识。 结构设计的能力尚需加强。指导教师意见 指导教师签名：2012年 12 月 15 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名： 年 月 日A simplified twin screw co-rotating food extruder: design, fabrication and testingAbstract A simplified co-rotating twin screw food extruder was designed, fabricated and tested in England, followed by extensive testing in Sri Lanka. It was built as a model to meet the specic product and nancial constraints of less developed countries and was expected to be used in those countries to widen the production capabilities of extruded foods. The machine had an estimated delivery of 10 kg/h and was made mainly with mild steel. Two types of screw were made, one with a constant pitch of 14 mm and the other with varying pitch in segments of 14, 12 and 10 mm. The machine was powered by a 2.2 kW electric motor with electronic speed controls. The machine also had electrical heating with a temperature controller and a pressure sensing device. The cost of fabrication of the machine was estimated at 2000 with most of the parts built in a fairly simple workshop. A mixture of rice and dried banana was successfully extruded as a potential snack food and on the basis of maximum expansion the best results was obtained from a barrel temperature of 120C, screw speed 125 rpm, feed moisture 15% and with a die orice size of 3 mm. When the alternative compression screw was tested very similar results were achieved with no signicant improvement in product expansion. 1999 Elsevier Science Ltd. All rights reserved.Keywords: Twin screw extruder; Design; Low cost; Snack food; Continuous cooker; Local construction; Cereal mixturesNomenclatureA Die diameter (mm)B Channel width (mm)C Screw circumference (mm)d Screw core diameterD Outer diameter of screws (mm)H Flight depth (mm)M Moisture content (% wet basis)n Number of fight turnsN Speed angular (rev/min)p Pitch (mm)Q Delivery rate (mm3/min)S Total helical length of screws (mm)t Temperature (C)T Residence time (min) Overlap angle of screw fights (degrees) Calender gap (mm) Side clearance (mm) Product density (g/mm3 ) Helix angle (degrees)1. Introduction Extrusion cooking is finding ever increasing applications in the food process industry. Apart from providing a means of manufacturing new products, it has successfully revolutionised many conventional manufacturing processes (Harlow, 1985, Frame, 1994). Today,extruders come in a wide variety of sizes, shapes and method of operation. There are three types of food extruder found in industry: hydraulic ram, roller and screw type extruders (Frame, 1994). The screw extruders are very different to the other two having special features such as continuous processing and mixing ability. Single and twin screw types are both widely used in the food process industry. Unfortunately, most of the food extruders available in the market are either so costly that less developed countries cannot a.ord to buy them except by some form of assistance or outside investment or else are not appropriate for the wide variety of materials that need to be processed. As a result the growth of extrusion technology of food into these countries has been hindered despite its many advantages. In particular there appears not to be a suitable twin screw extruder available at suffciently low cost for use in developing countries. The high cost of these machines is largely due to the sophisticated constructional features with many controls that are not essential for many applications.The initial purchase cost is therefore a major barrier to the wider introduction of extrusion to developing countries where many raw materials are available to be processed into nutritious and palatable food items. Attempts have been made to utilise low pressure and simple extruders for baby weaning foods some of which have been very successful with programs through organizations such as Feed the Millions (Santa Monica,California, 90406, USA) and Thriposha (USDA/USAID). The need has long been recognised for simple,yet versatile machines at affordable prices which are capable of exploiting the natural food resources (Sahagun,1977), Jansen and Harper (1980), Harper and Jansen(1985). These could incorporate all the usual cereals such as rice, millet, maize and sorghum with a rich variety of nutritional and tasty additives such as fruits,vegetables and spices. The objective of this study therefore was to eliminate or simplify many of the unnecessary features of the currently available machines so that fabrication could be done in an unsophisticated workshop, while ensuring the versatility to permit the production of acceptable extruded foods especially using blends of fruits and cereals. This latter technique was developed by Gamlath (1995) using a single screw extruder to produce a range of extrudates that she adjudged to show great promise as a snack food or breakfast cereal in Sri Lanka in particular but also in many developing countries and also as a high value export. These products were largely based on mixtures of fruit and cereals such as mango, banana and tomato with maize, rice and wheat. Attractively textured and flavoured items were produced which could easily be further flavoured with spices, sugar and salt. Many developing countries use home based businesses to produce snacks and ready-to-eat meals and these product well into this well established culture. Machines made in the developing country, however, need to be low cost and relatively simple, easy to maintain and operate. In this study the particular features required were good transport characteristics for sticky materials and good mixing ability which are needed for the blended crops selected. Short residence times and low to medium pressures were acceptable.2. Design approach The design of the extruder in this study was mostly based on the results of extrusion studies done using a single screw laboratory scale extruders (Brabender,Warrington, Cheshire, UK) as part of the same programme,and supported by engineering principles and constraints applicable to a developing country. In the design process, the level of pressure likely to be developed within the extruder barrel becomes the most important factor as it determines the sizes of all the important components of the extruder such as bearings,shaft diameters and barrel dimensions. As these machines often operate under elevated temperatures, pressure tends to vary unpredictably because of complex rheological properties of food dough as related to varying temperature along the barrel. Therefore, actual measurements of extruder process variables, were made on the chosen range of food materials on the laboratory single screw extruder. This approach was reckoned to be more appropriate rather than a theoretical one, that cannot be generalised especially for materials of unknown rheology. Hence, approximate values for some of the most important parameters such as die sizes, pressures,temperatures etc. were quantified. These values were then tested again in the experiments described later for the twin screw system.2.1. Single vs twin screws Many comparisons between twin and single screw extruders have been made (Harper, 1992) (Hauck, 1985 ) (Hauck & Ben Gera, 1987) (Van Zuilichem, Stolp & Janssen, 1984) and many of the features discussed are relevant to the current application. Single screw machines meet most of the criteria for developing countries but unfortunately certain of the technical requirements can only be met by twin screws such as versatility, adequateow of feed into the screws and, particularly in this case, ow of the material down the barrel without spinning within it. This is a common problem with the rather sticky or high moisture materials that were envisaged with the incorporation of fruits and vegetables and other tropical crops and flavours and experienced by Gamlath (1995). The forward motion of the food dough relies entirely on the friction between the material and the interior surfaces of both screw and barrel. This is particularly so in a single screw but less so in a twin screw. Single screw extruders are generally cheaper than the twin screw type owing to their simpler construction, but they are more likely to block than twin screw extruders. The dilemma facing the designer, therefore, is that although the operational problems can be avoided by using twin screws their sophisticated constructional features would have to be simplified significantly to achieve the low cost objective. In twin screw extruders the screws can be made as either co-rotating or counter rotating, with differing amounts of intermesh, pitch and clearances, all of which affect the processing characteristics of the machine (Martelli, 1983). Since the flight of one screw engages the channel of the other the twin screws prevent material from sticking to the screws and rotating with the screw, hence encouraging forward motion of dough with reduced slip (Jansen, 1978). This also enhances the mixing of materials in the channels of the screws. The counter rotating type of twin screw extruder can give better material ow characteristics pushing the material positively forward towards the die but reducing the degree ofmixing of materials within the extruder. Another unfortunate feature is that separating forces between the screws can cause severe wear of the side walls. On the other hand, co-rotating, twin screw extruders give additional advantages such as pressure balance in transverse planes of the screws and a wiping action of the fights due to the opposing linear velocities at the fights of intermeshing region. Therefore, it was decided that a twin screw co-rotating extruder would provide all the versatility and characteristics required for processing the food materials envisaged in a developing country. The only problem then was to design a satisfactory machine that would also meet the cost criteria.2.2. Screws The central part of an extruder is the screw. The screws rotate in a tightly fitting barrel and convey the material from feed end to die end, mixing and com-pressing the ingredients. The capacity of the extruder is mainly determined by the screw outer and root diameters, pitch and fight width (Fig. 1). Therefore, the screw overall dimensions have to be first determined according to the desired output to initiate the design process. One other important factor is the residence time, as it determines the degree of cooking taking place in the extruder. Exploratory trials and the work of Gamlath (1995) indicated that a residence time of about 16 s would be adequate at the mean speed. It is, however, influenced by many of the design parameters including the length, diameter and pitch of the screws although it can be controlled largely by the operational screw speed of the extruder and the selected die size. The rheology of the material also has a major influence on the throughput so residence time cannot be accurately predicted. In this study several dimensions of the screws were determined in order to suit the expected output and residence time. The geometry and equations relating many of these factors are given in Fig. 1 and Eqs. (1)(3) below. The maximum output was not the rst priority but similar sized extruders and single screw trials indicated a typical delivery rate of up to 10 kg/h. The residence time was designed to be short as the novel products planned were not expected to rely on long processing times. The short residence time was particularly sought in order to maintain the vitamin C content of perishable products which could be easily destroyed if cooked too long (Seiler, 1984). The influence of screw pitch is such that low values with small helix angles lead to longer residence times because of the increased number of cycles that the material has to go through. On the other hand, large pitches would reduce the degree of mixing and uniformity of heat distribution due to the increase in volume of material contained in the screw channels. Furthermore, if the fight width is also in-creased in proportion with the pitch to avoid large gaps between engaging fights, the power consumption is in-creased due to the increased surface area of shear be-tween the fight tip and the barrel. Therefore, in order to maintain the channel volume within reasonable limits and to have a fairly short residence time the pitch was selected as 14 mm. In view of the foregoing the outer diameter of the extruder was chosen at 30 mm with a helix angle at 8.5 which is in the range recommended by Martelli (1983) for similar plastic extrusion machines. The parameter most affected by the outer diameter is the extruder throughput, which was not a critical factor in this study apart from it being a low value to suit a large numbers of experiments. Another feature affected by the outer diameter is the screw center distance which in turn determines the fight height and the amount of intermesh. The screw center distance is vital as it establishes the space available for thrust bearings. Therefore, the screw center distance, the amount of intermesh and the root diameter all have to be carefully adjusted so that a maximum space is made available for the thrust bearings. The screw length, with pitch, governs the number of fight turns and has a major influence on the residence time which was planned to be short compared to most extruders. The length of the screws had to be relatively short therefore which was fortunate as this suited the manufacturing facilities available to construct a twin screw extruder barrel. It is not easy to machine two overlapping holes to accommodate the twin screws with a simple machine tool especially when the length is large as drills tend to wander. The length of barrel and screws to give the required residence time was 224 mm. The foregoing design choices permitted calculation of the number of turns as 16 (Eq. (1) with a preliminary value of fight height of 4 mm.The residence time is dened assuming no slip as,Referring to Fig. 1, the non-intermeshing part of the screws the length of circumference, C can be written as, ,=overlap angle= (1)The channel width is a major factor affecting the volume of screw channels and hence the throughput. Since the pitch is already xed, the value of the channel width depends on the selection of the values for the width of the fight and the clearance needed between engaging fight flanks. Considering the primary dimensions of the screw profile, the fight width at the root was calculated as 5 mm, leaving a reasonable side clearance of 2 mm. This established the channel width as 9 mm. The channel height was taken as 4 mm to have an output of 10kg/h at 200 rpm. A simple volumetric determination based on no-back flow was used to estimate the delivery rate (Q) as given by Eq. (2). (2)Referring to Fig. 1, the root diameter and the center distance between two screws were calculated as 22 and 27 mm, respectively, leaving a clearance (calender gap) of 1 mm between the tip of the screw fight and the bottom of the channel of the other screw.The fight flank angle of 7 was selected to avoid possible binding of the fights in operation. The minimum angle was given by the Eq. (3) (Jansen, 1978). (3)Compression of the product in the single screw barrels can be achieved by one of several methods as described by Harper (1979). These include varying pitch with constant root and outer diameters, use of tapered screws having constant pitch and tapered root diameter with constant outer diameter. Not all these possibilities can be applied to twin screws because of their geometrical interdependency. One of the simplest way of making screws achieve compression is to change the pitch along the screw and thus change the channel volume from feed end to die end. In this study it was decided to give the screws three different pitches in equal lengths along the screw using a lathe. The pitches selected were 14, 12 and 10 mm and in equal lengths along the screw with aclearance of 7 mm between each segment allowed for machining purposes. An alternative for simple compression screw design is to increase the root diameter of the screws from feed to delivery but this was considered to be somewhat harder to make on a simple lathe than the system chosen.2.3. Barrel The extruder barrel that accommodates the screws should be mechanically strong enough to withstand the pressures developed in the barrel and to resist the wear. The exact pressures inside the barrel are not known and, therefore to estimate the barrel wall thickness as well as to design the thrust bearings a level of pressure had to be assumed. It was measured during the preliminary work in the single screw extruders and from quoted work for similar materials. Pressures in commercial extrusion machines can reach up to 17 MPa (2500 psi) (Harper,1979), depending on type of material, length of extruder and many other factors. In this study a maximum pressure of 10 MPa as design pressure was considered to be more than adequate especially with such a shortbarrel. The minimum barrel wall thickness was calculated as 6 mm from thin cylinder theory (Ryder, 1953) that would withstand a hoop stress of 100 MPa. The barrel, shown in Figs. 2 and 3, was designed to t together in two parts, each 112 mm long for ease of manufacture, as it can be dicult to retain the correct alignment of the bores otherwise. These were bolted end to end with locating pins, each portion was also split into two halves length ways for easy dismantling in theevent of a serious blockage.2.4. Dies The die of an extruder plays an important role in deciding the product physical properties such as density, expansion, surface texture and the final shape of the product. When the product emerges from the die hole,due to the rapid release of pressure flashing o. steam, the product tends to swell (Harper, 1979). Therefore the product shape is not the same as the die shape. The shape of the product depends on the ratio of length to cross sectional area of the die hole. Smith (1986) reported that swelling of the product decreases with the increase of length to diameter ratio due to the loss of memory from the entrance to the die outlet. Materials accumulated at the die entrance so ready removal of the dies was essential in order to help the cleaning up process after each run of the extruder. Die changing was an important feature in setting up randomised experiments but for a commercial machine with longer runs this would become far less frequent. In order to ensure the smooth flow of material from the screws to the dies the die plate was machined in the shape of a double cone to t the pointed end of the two screws as shown in Fig. 2. The dies were circular in shape and were made so that they could be externally screwed to the die plate.简单的双螺杆挤压设备的设计，制造和测试S.A.M.A.N.S. Senanayake a, B. Clarke摘要：简单的双螺杆食品挤压机被设计，制造和测试之后，紧接着大量的测试在斯里兰卡进行。它是用来满足一些特殊产品的的制造，而且期望能够应用于欠发达地区来扩大食品产品的生产范围。这个机器的生产能力为10Kg/h,大部分是用软钢制造而成。这个机器有两种螺杆，一种是14mm的螺距，另一种是具有14，,12和10三种变化的螺距。这个机器由2.2KW的可调电动机驱动。它还有电加热系统，拥有温度控制和压力感应功能。这款机器在一般的工厂里的制造成本约为2000英镑。大米和干香蕉的混合物被成功的挤压膨化为一种方便食品，是在机筒温度为120度，螺杆转速为125r/min，食品含有水分占15%并且挤出空的直径为3mm的时候挤出的。其它种类的螺杆在没有特别改进的情况下获得的挤压结果与此相似。 1999年Elsevier Science 有限公司的专利。关键词：双螺杆挤压机；设计；低成本；休闲食品；连续烹；地方建设；谷物混合。符号： a 挤出直径（mm） B 通道宽度（mm） C 螺杆周长（mm） d 螺杆中心距（mm） D 螺杆直径（mm） H 螺纹深度（mm） M 含水量（%） n 螺纹头数（mm） N 转速（r/min） P 螺纹高（mm） Q 生产流量（） S 螺杆长度（mm） t 温度（） T 停留时间（s） 螺纹升角（） 间隙（mm） 侧间隙（mm） 产品密度（g/ 螺旋角1简介挤压机是找到的不断为食品加工也提供应用的机器，除了提供了一系列的生产新产品之外，它已经成功的改善了许多传统制造工艺。现在也诞生了一系列不同尺寸、形状和操作方法的挤压机。工业上有三种基本的挤压机：液压挤压机、辊式挤压机和螺杆式挤压机。螺杆挤压机和其它两种类型的挤压机有着明显不同的特征，比如连续的生产能力。单、双螺杆挤压机都广泛地应用在食品加工领域，但是，市场上销售的挤压机成本太高，一般欠发达地区购买不到，除非接受援助或者有外来投资介入，或者这些机器不能适应来加工更多品种的原料，所以就导致了食品挤压机技术在这些地区的发展被阻碍，尽管它具有这些技术的优势。特别是看上去在发展中国家，存在着应用并不合适的但是成本较低的双螺杆挤压机。这种机器之所以成本高，大部分是因为其有许多的复杂结构特征，比如对其他机械来说并不必要的控制系统。初次购买最大的障碍就是却反更广泛地介绍，让欠发达地区的人们知道很多原料都可以用挤压机来加工成营养谷物食品，人们已经在尝试用低压和简单的挤压机以生产婴儿断奶食品，而且部分产品已经在某些公司取得成功，如Feed The Millions和Thriposha。这种需要一直都可以被认可，所以价格和合理多功能机可利用多种食品原料。这些机械可以混合所有常见的谷物如大米、粟、玉米和高粱以及富含营养的口感也很好的水果蔬菜和香料。之前的研究主要是为了限制和简化现在使用的机器的一些不必要结构，这样就能使制造一些不太复杂的同时又能保证多样性来生产各种挤压膨化食品，特别是和谷物的混合食品，这种技术在1995年被Gamlath应用于一个单螺杆挤压机来生产一系列的挤压膨化食品这使得她生产的休闲食品和谷物早餐不仅在许多发展中地区显得尤为特别，也可以作为一个高附加值的出口产品。这些产品大多是基于水果和谷物的混合物，比如芒果、香蕉、西红柿和玉米、大米、小麦混合，纹理美观味道好，被生产之后，能够进一步假如香料、糖和盐。许多发展中地区用地方特产来生产休闲和方便食品，这些食品业和复合当地已有的文化。机械的制造在发展中地区需要降低成本要更容易运行和操作，在这份研究中，所要求的特殊的结构特征是对粘性物料来说好的运输方式和高混合能力以便对于有需要的谷物混合，要求的停留时间短，低中压比较适合。2.设计步骤在这份研究中关于挤压机的设计大部分基于已较成熟的实验室单螺杆挤压机中的螺杆的研究，这符合机械行业的准则，但是也限制其再发展中地区的应用。在设计过程中，挤压机桶内压力的大小成为了决定挤压机轴承、轴的直径和筒尺寸等最重要的因素。因为机器在工作的时候由于视频预料的复杂流变性能以及在筒内的温度变化，导致温度不断提升，压力的变化具有不可预测性，因此，实际上挤压机筒内压力的变化范围的测量是通过在食品原料在实验室内单螺杆挤压机上来测定的。用这种方法来估算比理论计算更准确，理论计算对于原料的流变性能未知的原料更不准确，因此，估算可将一些重要的参数如尺寸、压力、温度等量化。这些数据被测算后，菁修改后应用于双螺杆的系统中。2.1单、双螺杆关于单、双螺杆的比较有很多，许多关于结构的讨论都和现在的应用有关。单、双螺杆机器可以满足发展中国家的标准，但是对于一些非标的技术要求只能通过双螺杆来满足，比如有多功能的要求、连续充足喂料的，特别是对于流入筒内的没有自旋的原料，对于高粘度或者高水分的原料。Gamlath曾设想把水果、蔬菜和其他一些典型的农作物及调味料混在一起。食品面团前期的运动主要是由于原料和两个螺杆以及筒表面间的摩擦，这种情况早单螺杆的机器中要比在双螺杆中更明显。单螺杆挤压机因其更简单的结构所以比双螺杆机型更便宜。但比双螺杆更容易制造，双螺杆的设计更困难，尽管运行问题可以通过双