高剪切式單螺桿擠壓機設(shè)計

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編號 無錫太湖學院 畢業(yè)設(shè)計（論文） 相關(guān)資料 題目： 高剪切式單螺桿擠壓機設(shè)計 信機 系 機械工程及自動化專業(yè) 學 號： 　　　 0923202　　　　 學生姓名： 沈 川 指導教師： 　 戴寧 （職稱：副教授 ） 2013年5月25日 目 錄 一、畢業(yè)設(shè)計（論文）開題報告 二、畢業(yè)設(shè)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(shè)計（論文） 開題報告 題目： 高剪切式單螺桿擠壓機設(shè)計 信機 系 機械工程及自動化 專業(yè) 學 號： 0923202 學生姓名： 沈 川 指導教師： 戴寧 （職稱：副教授 ） 2012年11月25日 課題來源 自擬題目 科學依據(jù)（包括課題的科學意義；國內(nèi)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 擠壓機是擠壓加工技術(shù)的關(guān)鍵. 擠壓加工技術(shù)作為一種經(jīng)濟實用的新型加工方法廣泛應用于食品生產(chǎn)中, 并得到迅速發(fā)展. 擠壓加工主要由一臺擠壓機一步完成原料的混煉、熟化、破碎、殺菌、預干燥、成型等工藝, 制成膨化、組織化產(chǎn)品或制成不膨化的產(chǎn)品. 只要簡單地更換擠壓模具, 便可以很方便地改變產(chǎn)品的造型。 （2）擠壓機的研究狀況及其發(fā)展前景 . 近十年來，擠壓機行業(yè)發(fā)展迅速，CAD/CAM的電腦軟件應用，數(shù)控切割機，電火花機床，加工中心等電腦控制機床的運用普遍運用于擠壓模具的制造，極大滿足了擠壓制品的復雜程度，表面質(zhì)量，尺寸精度。同時，用于冷擠和熱擠的工具材料越來越多，滿足了擠壓工具的多樣性選擇。材料的熱處理也越來越規(guī)范，提高了擠壓工具的使用壽命。連續(xù)擠壓因其連續(xù)性、投資小，見效快的優(yōu)點廣泛被小型企業(yè)采用。連續(xù)擠壓主要運用在鋁及鋁合金擠壓管材，簡單界面的擠壓制品生產(chǎn)。 擠壓技術(shù)作為食品工業(yè)中得一項重要技術(shù)并得到更大的發(fā)展。它能將食品原料直接 擠壓成型得到我們需要的產(chǎn)品。現(xiàn)代食品工業(yè)用的螺桿擠壓機集混合、融和、蒸煮、改性反應、 調(diào)質(zhì)、組織化、成型、膨化等多種功能于一身，體現(xiàn)出有利于自動控制、 便于靈活轉(zhuǎn)產(chǎn)以及節(jié)能、節(jié)勞力、節(jié)省生產(chǎn)場地等優(yōu)點。同時，擠壓技術(shù)生產(chǎn)嬰兒食 品、制品的性狀發(fā)生改變，產(chǎn)品的速溶性、沖調(diào)性提高，產(chǎn)品極易消化，且提高了氨基酸的含量。 研究內(nèi)容 ① 高剪切式單螺桿擠壓機在食品工業(yè)中的應用及工作原理 ② 高剪切式單螺桿擠壓機的總體結(jié)構(gòu) ③ 高剪切式單螺桿擠壓機的主要參數(shù)計算 ④ 高剪切式單螺桿擠壓機的傳動系統(tǒng)及擠壓部件設(shè)計 擬采取的研究方法、技術(shù)路線、實驗方案及可行性分析 （1）實驗方案 掌握高剪切式單螺桿擠壓機的工作原理，通過對其結(jié)構(gòu)及特點的研究了解擠壓機的結(jié)構(gòu)，從而進行對擠壓部件的研究和設(shè)計。 （2）研究方法 通過學習了解擠壓機的結(jié)構(gòu)參數(shù)，對擠壓部件的參數(shù)進行計算及確定，按照擠壓機的結(jié)構(gòu)進行裝配圖及擠壓部件零件圖的繪制。 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(guān)參考資料，完成畢業(yè)設(shè)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(shè)計相關(guān)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：單螺桿擠壓機的主要參數(shù)計算與確定。 2013年3月18日-2013年4月14日：高剪切式單螺桿擠壓機的總體結(jié)構(gòu)設(shè)計。 2013年4月15日-2013年4月28日：零件圖及三維畫圖設(shè)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： 了解擠壓機的工作原理,內(nèi)部結(jié)構(gòu)以及高剪切式單螺桿擠壓機的優(yōu)缺點,熟練繪制擠壓機的裝配圖,傳動系統(tǒng)及擠壓部件的零件圖。 特色或創(chuàng)新之處 ① 單螺桿擠壓機在食品工業(yè)中操作更簡單。 ② 高剪切式單螺桿擠壓機結(jié)構(gòu)簡單、易操作、裝拆方便。 已具備的條件和尚需解決的問題 ① 設(shè)計方案思路已經(jīng)非常明確，已經(jīng)具備機械設(shè)計的知識。 ② 研究問題的能力尚需加強，結(jié)構(gòu)設(shè)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(lǐng)導簽名： 年 月 日 英文原文 Ability of a ‘‘very low-cost extruder’’ to produce instant infant flours at a small scale in Vietnam C. Mouqueta,*, B. Salvignolb, N. Van Hoanb, J. Monvoisc, S. Tre`ched aUR106, Nutrition, limentation Socie′tes, IRD, BP 182, Ouagadougou 01, Burkina Faso bGRET, 269 Kim Ma Street, Hanoi, Viet Nam cGRET, 213 rue La Fayette, 75010 Paris, France dUR106, IRD, BP64501, F34 394 Montpellier cedex France Received 25 July 2002; received in revised form 18 November 2002; accepted 21 November 2002 Abstract Extrusion cooking is a useful process for the production of instant infant flours, as it allows gelatinisation and partial dextrinisation of starch, as well as reduction of the activity of some antinutritional factors. But existing extrusion equipment is not suited to the context of developing countries as it requires considerable financial investment and the production capacity (minimum300 kg/h) is too high. The aim of our study was to improve traditional extruders with low production capacity (about 30 kg/h) manufactured in Vietnam and to test their performance in the production of infant flours. Several blends made with rice, sesame and/or soybean have been extruded with the modified equipment that we name ‘‘very low-cost extruder’’. In the case of blends containing soybean, starch gelatinisation was not complete, and decreased with an increase in the lipid content of the blend. The rate of trypsin inhibitor destruction evolved in a similar way. Adding water before extrusion, or extruding the blends twice was not effective in increasing the rates of starch gelatinisation or trypsin inhibitor destruction. However, the ‘‘very low-cost extruder’’ proved its ability to process the rice–sesame blend that had a lipid content of less than 6 g/100 g DM, and low initial water content [around 10%, wet basis (wb)]. In this case, extrusion led to total starch gelatinisation and the extent of starch dextrinisation, which was measured by comparing the viscosity of gruels prepared from crude and corresponding extruded blends, was sufficient to prepare gruels with substantially increased energy density. With the addition of roasted soybean flour, sugar, milk powder, vitamins and minerals, this blend could provide a nutritious instant flour usable as complementary food for infants and young children. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Extrusion cooking; Instant flour; Complementary food; Gelatinisation; Dextrinisation; Trypsin inhibitor destruction 1. Introduction Extrusion cooking is one of several different processes used to produce infant flours. This particular process has many advantages that have been extensively reviewed (Bjo¨ rck & Asp, 1983; Camire, Camire, & Krumhar, 1990; Harper & Jansen, 1985). From a nutritional point of view, extrusion cooking allows inactivation of certain antinutritional factors like trypsin inhibitor factors thus increasing protein digestibility. The high temperature generated during processing ensures satisfactory hygienic quality, and in general results in starch gelatinisation, thus leading to an instant flour. If not truly instant, the flour is at least pre-cooked, and the subsequent time required to cook the gruel is considerably reduced. During extrusion cooking, raw materials also undergo high shear, thus allowing partial starch hydrolysis (Colonna, Doublier, Melcion, De Monredon, & Mercier, 1984). The extent of hydrolysis determines the energy density at which it will be possible to prepare a gruel of semi-liquid consistency that is acceptable to infants. At a given consistency, the more important the starch is hydrolyzed, the higher the gruel energy density will be. In spite of these advantages, the adoption of extrusion cooking processing for the production of infant flour in developing countries is still limited. Only a few industrial units produce extruded flour at a large scale mainly in response to the need of international or non-govern- 0308-8146/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0308-8146(02)00545-9 Food Chemistry 82 (2003) 249–255 www.elsevier.com/locate/foodchem *Tel.: +226-30-67-37; fax: +226-31-03-85. E-mail address: claire.mouquet@ird.bf (C. Mouquet). mental organisations for emergency supplies. The main reason for this is that most extruders are designed for large-scale production, thus requiring very high investment and technical knowledge. Even the so-called low-cost extruders, or dry extruders that were developed for the production of complementary foods at the beginning of the 1980s by the university of Colorado (Harper, 1995; Harper & Jansen, 1985; Said, 2000), are too costly and their production capacity is too high (about 55,000 dollars for a machine with a production capacity of 1 ton per hour), and are thus not affordable for developing countries. The development of a small simple machine, with a small production capacity (about 30 kg/h) is therefore of great potential interest. The Vietnamese context is particularly well suited for the development of the production of infant flour by extrusion cooking for several reasons. 1. In rural areas and particularly in the plains, mothers prepare a thermos of boiled hot water each morning in order to have a supply of safe drinking water available during the day, and this water could easily be used for the preparation of a gruel with an instant flour 2. A rudimentary extrusion cooking process has been used for many years in the countryside; simple extruders with very small production capacity already exist and are used for the production of snacks or cassava noodles sold in the street. These machines were probably originally designed in the United States at the end of the nineteenth century for the extrusion of plastic. 3. These small extruders are now manufactured locally in small mechanical workshops, and it is also easy and cheap to construct spare parts locally for the maintenance of the machines. Occasional attempts have been made to produce instant infant flours using these rudimentary local extruders but these efforts have not continued, firstly because their impact on nutritional quality of infant flours was not satisfactory, and secondly because the machines were not sturdy and often broke down during production. Taking the features of this specific context into account, we modified the rudimentary type of local extruder to improve their ability to produce infant flour, as well as their sturdiness. These improved extruders with limited production capacity were named ‘‘very low-cost extruders’’ in reference to the low-cost extruders that Harper and Jansen already developed for the production of nutritious precooked foods for developing countries (Harper &Jansen,1985). The objective of this study was to test the performance of these improved ‘‘very low-cost extruders’’ and, in particular, to evaluate the instant character of the flour, the extent of starch dextrinisation and the residual trypsin inhibitor activity of extruded blends. 2. Materials and methods 2.1. Extrusion cooking equipment The ‘‘very low-cost extruder’’ we used is a simple single- screw autogenous extruder manufactured in Vietnam by a small enterprise named ‘‘Mechanical Workshop no. 14700, (Phan Chu Trinh Street, Da nang City) according plans that we furnished (see photo in Fig. 1). The drive motor has a power of 10.5 kW. The barrel length is 200 mm with a length/diameter ratio of 5 and has a central cylindrical die of 5 mm in diameter and 9 mm in length. The rotating speed of the screw is high (500 rpm), thus allowing high shear. The design of the screw was modified (constant pitch and gradual decrease in the flight depth), to allow a progressive increase in friction forces and consequently in the temperature inside the barrel. The screw diameter is 40 mm and the root diameter increases gradually from 33 to 38 mm (see photo in Fig. 2) The extruder barrel wall has reverse helical grooves to enhance forward conveyance of the product. To ensure a regular feeding rate, the extruder is equipped with a motorised feeding screw that allows feeding rates from 5 to 39 kg/h. Residence time is between 4 and 20 s, which is very short in comparison to other extruders but longer than the residence time observed in rudimentary Vietnamese extruders. 2.2. Raw materials The raw materials used to prepare composite flours were the cheapest and the most easily available on the Vietnamese market. The basic cereal was polished rice. Soybean and sesame were added to increase lipid and protein contents. All raw materials were bought locally. Soybean was dried in an oven to reach a dry matter content above 92%, wet basis (wb), before being dehulled in an abrasive disk huller equipped with a cyclone to remove hulls and straws. After dehulling, the abrasive disks were brought closer and the soybean passed a second time in the machine to be roughly ground to a size of about 2 mm. Different infant flour formulas (flours A, B, C and D) were calculated to achieve the minimum protein and lipid contents of respectively, 12 and 8 g/100 g DM required for complementary foods, after addition of a premix to the extruded blends (Table 1). The premix C. Mouquet et al. / Food Chemistry 82 (2003) 249–255 Fig. 1. The ‘‘very low-cost extrusion-cooker’’ used for experiments (designed and manufactured in Vietnam). 1. Feeding hopper; 2. screw and barrel; 3. central cylindrical die; 4. control panel (amperage, temperature, feeding screw On/Off, extruder On/Off); 5. feeding screw speed variator. Fig. 2. Main spare parts of the ‘‘very low-cost extrusion-cooker’’. 1. Barrel; 2. screw with gradual decrease in the flight depth and constant pitch; 3. cylindrical die of 5 mm in diameter and 9 mm in length. Table 1 Formulas and calculated protein and lipid contents of final composite flours Composition (g/100 g dry matter) Nutrient content of final flour (g/100 g DM) Ingredients blended Ingredients added Lipid Protein before extrusion after extrusion Rice Soybean Sesame Roasted soybean Premix Flour A 49.9 21.7 5.7 0.0 22.7 10.03 15.45 Flour B 50.2 27.1 0.0 0.0 22.7 8.05 16.63 Flour C 50.2 24.7 2.3 0.0 22.7 8.82 16.70 Flour D 52.4 0.0 4.9 20.0 22.7 10.12 16.33 Calculated from Souci et al. (2000). Premix prepared by blending sugar (66%), milk powder (22%), salt (4%), vitamins and minerals (7%) and vanilla aroma (1%). Total N content multiplied by 5.80, 5.30, 5.71 and 6.38 for rice, soybean, sesame and milk powder, respectively. (sugar 66%, milk powder 22%, salt 4%, aroma 1%, vitamins and minerals 7%, wt.) was added in order to meet recommendations for vitamin and mineral contents and confer suitable organoleptic characteristics to the flours. For blend D, the formula was calculated taking into account the addition of roasted soybean flour bought on the local market after extrusion to achieve required protein and lipid contents. The formula calculations were made with data from food composition tables (Souci, Fachman, & Kraut, 2000). Extrusion cooking experiments were performed on rice alone and on the different blends of rice, soybean and/or sesame used for the preparation of flours A, B, C and D (Table 2). After extrusion, all extrudates were ground (particle size <500 mm) before biochemical analysis. C. Mouquet et al. / Food Chemistry 82 (2003) 249–255 Table 2 Composition and calculated lipid and protein contents of rice and blends before extrusion Composition (g/100 g DM) Nutrient contenta (g/100 g DM) Rice Soybean Sesame Lipid Proteinb Rice 100.0 0.0 0.0 0.71 7.84 Blend A 64.5 8.1 7.4 11.18 18.25 Blend B 65.0 35.0 0.0 8.61 19.78 Blend C 65.0 32.0 3.0 9.60 19.09 Blend D 91.4 0.0 8.6 5.47 8.82 Calculated from Souci et al. (2000). Total N content multiplied by 5.80, 5.30 and 5.71 for rice, soybean and sesame, respectively. 2.3. Starch gelatinisation rate Total starch content of composite flours was determined by the enzymatic method of Batey (1982). Analyses were made in duplicate and both values are given. The extent of starch gelatinisation during extrusion cooking was determined in duplicate by a method based on the evaluation of amyloglucosidase hydrolysis susceptibility (Chiang & Johnson, 1977; Kainuma, Matsunaga, Itagawa, & Kobayashi, 1981). The gelatinisation rate is the ratio of starch fraction susceptible to amyloglucosidase hydrolysis and total starch (minimum, maximum and mean values are given). 2.4. Preparation of gruels Crude and extruded blend were ground and the flours obtained were used for the preparation of gruels with different dry matter contents using: 1. A ‘‘cooking procedure’’ comprising mixing flour with cold demineralised water into a slurry and cooking on a hot plate (300 C) with continuous stirring for 5 min once the mixture started to boil. 2. An ‘‘instant procedure’’ comprising adding demineralised water heated to 75 C to the flour and stirring vigorously. After preparation, gruels were allowed to cool to 45 C before viscosity measurements. Dry matter contents of the gruels were determined by oven drying at 105 C to constant weight. 2.5. Apparent viscosity measurements Apparent viscosity measurements were performed on gruels with a Haake viscometer VT550 with SV-DIN coaxial cylinders driven by a PC computer with the Rheowin 2.67 software. We applied the measurement procedure proposed by Mouquet and Tre`che (2001), i.e. shear rate of 83 s1, shear time of 10 min and measurement temperature of 45.00.5 C. 2.6. Procedure used to check the instant character of extruded blends To our knowledge, the term ‘‘instant’’, which usually describes dehydrated precooked food usable after the simple addition of hot water, is not accurately defined from a biochemical point of view. As starch becomes easier to digest when it is completely gelatinised and swollen, we chose to evaluate the instant character by comparing apparent viscosity of gruels prepared by the ‘‘instant’’ and the ‘‘cooking’’ procedures with the same dry matter content. Two scenarios can be expected: if the apparent viscosity of the gruel prepared with the ‘‘instant procedure’’ is equal or slightly higher than the viscosity of the gruel prepared with the ‘‘cooking procedure’’, then the flour can be considered as ‘‘instant’’. If it is lower, it implies that part of the flour starch is not totally precooked during the extrusion cooking stage and will continue to swell during the cooking of the gruel, thus leading to an increase in viscosity. 2.7. Trypsin inhibitor activity Trypsin inhibitor activity (TIA) was determined induplicate by the method of Kakade, Rackis, MacGhee, and Puski (1974), modified by Smith, Van Megen, Twaalfhoven, and Hitchcock (1980), and both values, expressed in trypsin inhibitor units (TIU) per 100 g DM, are given. The percentage of trypsin inhibitor destroyed during extrusion cooking were calculated from the ratio between TIA before and after extrusion, and mean, minimum and maximum values are given. 3. Results and discussion 3.1. Effect of very low-cost extruder on starch gelatinisation rate The main characteristics of the different extruded blends are given in Table 3. In all cases, we observed an increase in dry matter content after extrusion cooking. This increase is due to water loss by instant vaporisation at the exit of the die. For extruded rice and blend D only, the gelatinisation rate exceeded 90%, from which we estimated that gelatinisation rate had reached a satisfactory level. For extruded blends A, B and C, the gelatinisation rate after extrusion cooking ranged from 56 to 83%. The remaining native and, thus, non-digestible starch content was non negligible, and we consequently considered that the corresponding flours could not be used as ‘‘instant’’ flours, even though they appeared to be precooked. C. Mouquet et al. / Food Chemistry 82 (2003) 249–255 Table 3 Effects of processing with the ‘‘very low-cost extruder’’ on the starch gelatinisation rate and the trypsin inhibitor activity of rice and different blends Blend used for Dry matter Total starch Gelatinised Gelatinisation Trypsin inhibitor activity TI destroyed TIdestroyed (%) extrusion cooking content content starch content rate(%)c (g/100g, wb) (g/100g DM) (g/100g DM) TIU/g DM TIU/g DM of soybean Rice Before ECa 86.0 91.9–93.9 10.8–11.5 12 (11–12) – – – eRice After EC 90.5 85.0–87.8 93 (91–96) A Before EC 88.9 55.5–57.3 9.4–10.9 18 (16–20) 12,213–12,246 44,250–44,490 eA After EC 90.4 30.3–33.3 57 (53–60) 5766–6091 20,890–22,066 52 (50–53) B Before EC 90.1 61.2–65.9 10.6–12.7 18 (16–21) 13,518–13,900 37,655–38,719 eB After EC 95.5 51.1–53.8 83 (78–87) 3140–3491 954