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編號
無錫太湖學院
畢業(yè)設計（論文）
相關資料
題目： 雙軸式和面機設計
信機 系 機械工程及自動化專業(yè)
學 號： 0923210
學生姓名： 孫 勇
指導教師： 戴寧 （職稱：副教授 ）
（職稱： ）
2013年5月25日
目 錄
一、畢業(yè)設計（論文）開題報告
二、畢業(yè)設計（論文）外文資料翻譯及原文
三、學生“畢業(yè)論文（論文）計劃、進度、檢查及落實表”
四、實習鑒定表
無錫太湖學院
畢業(yè)設計（論文）
開題報告
題目： 雙軸式和面機設計
信機 系 機械工程及自動化 專業(yè)
學 號： 0923210
學生姓名： 孫勇
指導教師： 戴寧 （職稱：副教授）
（職稱： ）
2012年11月25日
課題來源
自擬課題
科學依據（包括課題的科學意義；國內外研究概況、水平和發(fā)展趨勢；應用前景等）
（1）課題科學意義
和面機又稱調粉機，是面食加工的主要設備，它主要用于將小麥粉與水按1：0.38—0.45的比例，根據用戶加工工藝要求（有時加食油、食堂、及其他食物和食物添加劑）混合制成面團，廣泛適用于食堂、飯店及面食加工單位的面食加工。
隨著市場份額的發(fā)展，手工和面的產量已跟不上人們的日常需求，和面機也應運而生。和面機操作方便，自動化程度高，不僅節(jié)省了人力，還省事省力，真正的做到了化勞力為動力的要求。和面機的產生使得面粉事業(yè)得到了更一步的發(fā)展。
和面機模擬手工和面的原理，使面筋網絡快速形成，使得蛋白組織結構均衡，使面的的產量大大高于手工和面，且生產出來的面品，口感光滑，透明度高，彈性好。
雙軸和面機的特點：
雙軸和面機是在單軸和面機的基礎上加以改進而成，其性能較單軸和面機優(yōu)越。
1該機有兩根旋轉軸，每根軸上垂直安裝數個葉片，構成平行，以相同方向轉動的攪拌器。
2傳動方式可以由主電機通過變速箱分別帶動兩軸做同向旋轉，也可以將一根作為主動軸，，通過齒輪傳動實現同向轉動。
（2）和面機的研究狀況及其發(fā)展前景
隨著食品行業(yè)的日益發(fā)展壯大，生產設備產能變大的要求變得日益強烈。和面機是大多數食品行業(yè)必備的生產設備，且一般處在生產流程的上游，和面機的產能，穩(wěn)定性，對整個生產線來說就顯得非常重要。如果單純靠增加設備的數量，產能雖然可以上去，但是不但設備的費用回大大增加，人力成本和故障率也會增加。
為了很好的解決以上問題，于是大型和面機誕生了。大型和面機自動化程度高，機器故障率低，一個人可以輕松看護兩臺大型和面機，其產量可以滿足大中型食品企業(yè)的需求。
研究內容
1熟練掌握雙軸式和面機的工作原理與結構；
2熟悉雙軸式和面機中和面過程的運動攪拌器結構設計與受力分析；
3熟練掌握雙軸式和面機的各參數的設計和各傳動的結構的設計；
擬采取的研究方法、技術路線、實驗方案及可行性分析
研究方法：
根據課題所確定的和面機種類，用途及生產能力確定和面機的主要構件（例如槳葉，容器）機構形式和尺寸參數，運動參數及動力參數（電機功率）。
根據雙軸式和面機主要構件的形式，性質及運動參數，擬定整機的機械傳動鏈和傳動系統(tǒng)圖。計算并確定各級傳動的傳動比，皮帶轉動，齒輪轉動等傳動構件的結構參數及尺寸，擬定機器的結構方案圖。
根據結構方案圖，在正式圖紙上擬定傳動構件及執(zhí)行構件的位置，然后依次進行執(zhí)行構件及傳動系統(tǒng)設計機體，操縱機構設計，密封及潤滑的結構設計。
研究計劃及預期成果
研究計劃：
2012年10月12日-2012年12月31日：按照任務書要求查閱論文相關參考資料，完成畢業(yè)設計開題報告書。
2013年1月1日-2013年1月27日：學習并翻譯一篇與畢業(yè)設計相關的英文材料。
2013年1月28日-2013年3月3日：畢業(yè)實習。
2013年3月4日-2013年3月17日：雙軸式和面機的主要參數計算與確定。
2013年3月18日-2013年4月14日：雙軸式和面機總體結構設計。
2013年4月15日-2013年4月28日：零件圖及三維畫圖設計。
2013年4月29日-2013年5月21日：畢業(yè)論文撰寫和修改工作。
預期成果：
根據提供的主要構件參數而計算出的傳動構件的參數，尺寸及機體等是合理的，可以進行正常的生產組裝，最終達到雙軸式和面機的工作要求。
特色或創(chuàng)新之處
造型優(yōu)美，占地面積小，機器操作噪音小。故障率低，使用壽命長。雙軸式和面機可以均勻的進行攪拌，使得面團得到良好的拉伸和揉捏，適于調制韌性面團。
已具備的條件和尚需解決的問題
1、設計方案思路已經非常明確，已經具備使用CAD制圖的能力和了解和面機原理結構等知識。
2、使用CAD制圖能力尚需加強，結構設計能力尚需加強。
指導教師意見
指導教師簽名：
年 月 日
教研室（學科組、研究所）意見
教研室主任簽名：
年 月 日
系意見
主管領導簽名：
年 月 日
英文原文
New energy-saving mechanical mixer and Overview of adaptable die design for
extrusion
Abstract
In the work there are described the results from the laboratory researches of the basic characteristics (performance) of one new type of energy-saving mechanical mixer, conditionally named ‘Eleron’. These characteristics (performance) are compared with respective results of the other known in the literature and successfully used in practice mixers. The mixer is designed for mixing and aerating liquid systems and it will be effective for mixing in the ferment reactors for biochemical industries, where the processes are energy absorbing.
Keywords: Mixer; Air-saturation; Power-number; Heat and mass-transfer during mixing; Aeration-number
1. Introduction
In implementing a long-term, energy-saving program for industry [1], the department of Heat and Mass-Transfer Technics in TU-Sofia, under the guidance of the author, has conditionally created for patent an original construction of energy-saving mixer. It has a universal function for mixing liquid systems in chemical, food, wine, tobacco, and biochemical industries. We expect our mixer to take its place with dignity in fermentation technics, because of its easy manufacture, good results in air-saturation and low energy consumption.
Till now it was the investigated laboratory version of ‘Eleron-1’ mixer, which is a small type, with D=(0.25/0.35)T. Universal appearance of mixer is shown in Fig. 1. It consists of a central round disk (1), which is carrying pap (2) and four wings (3). The wings are cut through in the middle (a–a) and in the beginning, near the round disk (c–c), and the receiving pieces are bend arch-shaped up and downward, making four blades with radius R=(0.05/0.07)D. Their length is L=0.8pR, as (considered) from line of bend. The blades on each following wing are in different order in bend direction, and because of this in working conditions there are circumstances for vortexes. This is very important when there is more than one mixer on a shaft (Figs. 1 and 2).
When mounting, we observe the axial flows, created by curved blades, to meet each other (if we aim air saturation) or to pass each other, when we aim mixing without aeration. In this way we create multitude of symmetrical current lines (vortexes), which spread symmetrically vessel.
2. Experimental
For researching characteristics (performances) of mixer ‘Eleron-1’ there are used two identical laboratory reactors with plane bottom and releasers, respectively with volumes 6.5 and 24 dm3. Reactor’s diameters are, respectively 190 and 300 mm, and mixers are make up with D_0.35T. As pattern substances there are used water and die thylene glycol, which under 20°C have dynamical viscosity and Pa · s. Reactor’s configuration is on Fig. 2 and the experiment tal installation, which is used, is on Fig. 3.
With this installation’s configuration we are researching the power consumption, working with and without aeration , heat-transfer during mixing with ‘Eleron-1’, that is why reactors have heat-transfer bogies-worm-pipes (serpentines) with respective tube diameter d1 and wind up diameter dS, which are on Fig. 2. For measuring DO2 (dissolved oxygen) in liquid phase during aeration, installation also has a bottle with nitrogen, air-compressor, sensor for DO2and a writing instrument, which register on the tape the oxygen absorption (Fig. 3).
Fig. 1. Scheme of mechanical mixer ‘Eleron-1’ in appearance from above.
2.1. Power coefficient determination
For this mixer’s characteristic are usedtwo reactors and two pattern substances, and the rotation frequency of mixer’s shaft is changing from 100 to 1200 min_1. Rotation frequency is chosen and fixed and after that is controlled with electronic cyclometer. Eu-number is determined under equation and it is read net power consumption P, for respective rotation frequency . The dependency is in Fig. 4 and is compared with the dependency of Rush ton-turbine.
2.2. Aeration-number determination
This exponent is defined under known methods, which is adopted for mixing technics. In our reactor with volume 6.5 dm3, with the help of air-distributed mechanism, the air is entranced with flow of qG_0.1 to1.5 V . The researching results are on Fig. 5 and are compared and heat-transfer surface (serpentine).
Fig. 2. Configuration of laboratory reactors with mechanical mixer
Fig. 3. Scheme of experimental installations: 1, thermostat; 2, reactor; 3, pressure vessel; 4, heat-transfer surface (serpentine)
2.3. Mass-transfer coefficient determination during mixing with ‘Eleron-1’
There are used two reactors with different volumes, which have air-distributed mechanisms and sensor form easuring and registering of CO2 in water. We work under 20°C, and the liquid phase, before each attempt, is scavenged with nitrogen until initial oxygen concentrationC0, which is changing progressively and is writing on the tape till establishing an equilibrium (saturation concentration)
.
3 Traditional Mixer
3.1 Different ways to classify the mixers.
3.1.1 According to the number of mixing spindles .There are single-spindle mixers and double-spindle or even triple-spindle mixers.
3.1.2 According to their mixing speed .There are slow-speed mixers(less than 30rev/min), high speed mixers (above 35rev/min), and variable speed mixers.
3.1.3 According to their operation mode. They can be classified into batch mixers and continuous mixers.
3.1.4 According to the axis position of the mixing spindle from which the mixing arms receive torque and motion .They can be classified into vertical mixers and horizontal mixers .In this chapter, he machines will be discussed in terms of this classification.
Investigations show that horizontal mixers are still the dominant mixing equipment in today’s modern bakery and snack industry, for they are of simple construction, simple in operation, and cheaper to run. They also have varied capacities and can be used for a wide variety of mixtures from a thin batter for cookie depositing to extremely tough dough for Chinese snack casing.
3.2 HORIZONTAL MIXERS
Horizontal mixers are characterized by having a horizontally located mixing spindle on which the mixing arms are fixed into the mixing bowl .Fig.2.1 is a typical front view of this kind of mixer.
3.2.1 Construction
A typical horizontal mixer consists of a mixing bowl，one or two mixing spindles by which the mixing arm(s) is or are driven through transmission mechanisms，and a main frame made of either cast iron or unitary construction of heavy steel plate，One or two motors are mounted below for mixing and bowl tilting functions together with a facia control and an electric interlock system to prevent access when the machine is running.
There are two types of weighing systems: one is separate from the mixer; the other calculates the weight change of the complete mixer before and after the addition of an ingredient, the mixer being located on a suitable weighing scale or platform. In this case the mixer is often referred to as a weigh-mixer.
3.2.2 Mixing bowl
The bowl of the horizontal mixers is of trough-like design with a curved bottom (U-shaped in cross section) and flat ends. The bowl surfaces in contact with the dough are commonly of stainless steel or stainless clad steel. This is the usual construction for the bowl ends, where the bearings are fixed to support the mixing spindles. The bowls of large modern mixers are generally double-‘skinned’in the form of a jacket through which chilled water or refrigerant can be circulated to prevent the dough warming up to too high a temperature as a result of mixing friction.
To avoid flour and other ingredients splashing, especially at the beginning of mixing, and for safety as well as food hygiene, the bowl is always equipped with a lid which is either removable or hinged for dough discharge and cleaning. For large mixers, he lid usually has provision for assisted ingredients feed.
There are two methods of dough discharging: by tilting the bowl(110。to 180。),or by mechanically sliding down the door in front of the stationary bowl to allow the dough to fall into an underlying hopper. For a ground-floor installation, the dough is often discharged into a dough tub which is usually fabricated in heavy gauge stainless steel and is supplied separately by the manufacturer.
The bowl-tilting operation is generally carried out by a worm-gear mechanism in which the worm-gear is fixed on the bowl sidewall.
Feeding of the bowl is carried out either manually for small mixers, or automatically through the corresponding pipes above the mixer and by means of a weighing system for large horizontal mixers.
Bowls are manufactured in a wide range of volumes which allow from a few kilograms up to 1500 kg of food materials to be mixed in them. The larger the bowl size, the greater the required power of the mixing motor, so that bigger batches of dough can be mixed, resulting in a higher rated capacity for the mixer. For most large mixers, the bowl is tilted by a separate reversible motor ranging from 0.75 to 2.26Kw.
3.2.3 Mixing arms
Mixing speed
The mixing operation is directly performed by the mixing arms, while its power is transmitted by its driving spindle (shaft or axle).That is, the speed of the mixing arm is dependent on the speed of its spindle. Horizontal mixers are designed in either a single or dual mixing speed mode. For the dual mode, its lower speed is half the rated maximum speed. As dough mixing is often carried out in two stages-blending of the ingredients, and developing the gluten-it is essential that the first stage should be accomplished at a lower speed(for example 36 rev/min) and the second stage at the rated speed (which will be 72 rev/min).Generally speaking, the machine with a mixing speed below 30rev/min is referred to as a slow-speed mixer, and that with a speed above 35rev/min as a high-speed mixer.Modern mixers commonly cover a wide range of speed variation from 20 to 145 rev/min or even up to more than 200 rev/min, which high speed allows a quick development of gluten elastic dough by means of suitable mixing arms.
The slow-speed mixers are generally used in short and soft dough mixing since a much longer time would be needed for hard and bread dough。
For of the mixing arms
The mixing arms are designed in various configurations and cross-sections for different mixing functions such as blending, dispersing, beating, shearing, scraping, stretching, or kneading to form either a uniform mass or a dispersion or a solution, or aeration (that is, either a soft dough or hard dough, a sponge dough or batter or topping with other food material).
Some mixing tools have a floral-hoop type, oval-type, or twisting-plate type and comprised only one or two loop-like arms without a centre shaft; they are referred to as‘shaftless’a agitators or mixing arms. The corresponding machines are referred to as ‘shaftless’ mixers. In the group, there are some other types of arm such as Z-type and S-type. Their cross-section is large to ensure strength . Their relatively complex configurations are commonly cast in one piece or are welded after forging .Attention should be paid to the coaxiality of the two sides of the arm during manufacturing to avoid severe trouble in the later mixing operation.
This type of mixer can be used for a wide range of dough with different consistencies, from thin batter to extremely tough dough., as the ‘shaftless’ arms are especially efficient in dealing with extensible dough, since in their rotation orbit there is always a limited clearance from the bowl inner walls, which is beneficial in showing the dough to be stretched and kneaded repeatedly to form an oriented gluten network.
Some other mixing tools (agitators) comprise simple shaped arms and a centre shaft. This kind of segmented construction is easy to manufacture and assemble, and its maintenance is lower than that of those described earlier. However, to deal with sticky dough, this group of agitators are at a disadvantage since the tendency of sticky dough is to adhere to the shaft, and the circular velocity at the centre shaft area is very low, resulting in a dead space and therefore improper mixing. Sometimes the centre shaft is covered by dough, layer upon layer.
The term “adaptable die design” is used for the methodology in which the tooling shape is determined or modified to produce some optimal property in either product or process. The adaptable die design method, used in conjunction with an upper bound model, allows the rapid evaluation of a large number of die shapes and the discovery of the one that produces the desired outcome. In order for the adaptable die design method to be successful, it is necessary to have a realistic velocity field for the deformation process through extrusion dies of any shape and the velocity field must allow flexibility in material movement to achieve the required material flow description. A variety of criteria can be used in the adaptable die design method. For example, dies which produce minimal distortion in the product. A double optimization process is used to determine the values for the flexible variables in the velocity field and secondly to determine the die shape that best meets the given criteria. The method has been extended to the design of dies for non-axisymmetric product shapes.
? 2006 Elsevier B.V. All rights reserved.
Keywords: Extrusion; Die design; Upper bound approach; Minimum distortion criterion
1. Introduction
New metal alloys and composites are being developed to meet demanding applications. Many of these new materials as well as traditional materials have limited workability. Extrusion is a metalworking process that can be used to deform these difficult materials into the shapes needed for specific applications. For a successful extrusion process, metalworking engineers and designers need to know how the extrusion die shape can affect the final product. The present work focuses on the design of appropriate extrusion die shapes. A methodology is presented to determine die shapes that meet specific criteria: either shapes which pro-duce product with optimal set of specified properties, such as minimum distortion in the extrudate, or shapes which produce product by an optimized process, such as minimum extrusion pressure. The term “adaptable die design” is used for the method nology in which the die shape is determined or modified to produce some optimal property in either product or process. This adaptable die design method, used in conjunction with anupper bound model, allows the rapid evaluation of a large number of die shapes and the discovery of the one that can optimize the desired outcome. There are several conditions that need to be met for the adaptable die design method to be viable. First, a generalized but realistic velocity field is needed for use in an upper bound model to mathematically describe the flow of the material during extrusion through dies of any shape. Second, a robust crite-
rion needs to be established for the optimization of the die shape. The criterion must be useable within an upper bound model. The full details of the method are presented elsewhere [1–6]. In the present paper, following a review of previous models for extrusion, the flexible velocity field for the deformation region in a direct extrusion will be briefly presented. This velocity field is able to characterize the flow through a die of almost any configuration. The adaptable equation, which describes the die shape, is also presented. The constants in this die shape equation are optimized with respect to a criterion. The criterion, which can be used to minimize distortion, is presented. Finally, the shape of an adaptable die, which produces of an extruded product with minimal distortion, is presented. The objective of the present paper is to provide a brief overview of the adaptable die design method.
2. Background
2.1. Axisymmetric extrusion
Numerous studies have analyzed the axisymmetric extrusion of a cylindrical product from a cylindrical billet. Avitzur[7–10] proposed upper bound models for axisymmetric extrusion through conical dies. Zimerman and Avitzur [11] modeled extrusion using the upper bound method, but with generalized shear boundaries. Finite element methods were used by Chen et al. [12] and Liu and Chung [13] to model axisymmetric extrusion through conical dies. Chen and Ling [14] and Nagpal [15] analyzed other die shapes. They developed velocity fields for axisymmetric extrusion through arbitrarily shaped dies. Richmond[16] was the first to propose the concept of a streamlined die shape as a die profile optimized for minimal distortion. Yang et al. [17] as well as Yang and Han [18] developed upper bound models for streamlined dies. Srinivasan et al.[19] proposed a controlled strain rate die as a streamlined shape, which improved the extrusion process for materials with limited workability. Lu and Lo [20] proposed a die shape with an improved strain rate control.
2.2. Distortion