外文翻譯--一個簡化雙螺桿旋轉食品擠壓機設計制造和檢驗

1、<p>　　A simplified twin screw co-rotating food extruder: design, fabrication and testing</p><p>　　S.A.M.A.N.S. Senanayake a, B. Clarke b,*</p><p>　　Division of Agricultural and Plantation E

2、ngineering, The Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka</p><p>　　Department of Postharvest Technology, School of Agriculture, Food and Environment, Silsoe</p><p>　　Collage, Cra

3、nfield University, Silsoe, Bedfordshire MK45 4DT,UK</p><p>　　Received 6 July 1998; accepted 10 February 1999</p><p><b>　　Abstract</b></p><p>　　A simplified co-rotating t

4、win 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 specific product and financial constraints of less developed countri

5、es 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

6、, one with a constant pitch of 14 </p><p>　　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 pot

7、ential snack food and on the basis of maximum expansion the best results was obtained from a barrel temperature of 120°C, screw speed 125 rpm, feed moisture 15% and with a die orifice size of 3 mm. When the alternat

8、ive compress ion screw was tested very similar results were achieved with no significant improvement in product expansion. © 19</p><p>　　Keywords: Twin screw extruder; Design; Low cost; Snack food; Cont

9、inuous cooker; Local construction; Cereal mixtures</p><p>　　Nomenclature</p><p>　　a Die diameter (mm)</p><p>　　B Channel width (mm)</p><p>　　C Screw circumference (mm)&

10、lt;/p><p>　　d Screw core diameter</p><p>　　D Outer diameter of screws (mm)</p><p>　　H Flight depth (mm)</p><p>　　M Moisture content (% wet basis)</p><p>　　n N

11、umber of fight turns</p><p>　　N Speed angular (rev/min)</p><p>　　p Pitch (mm)</p><p>　　Q Delivery rate (mm3/min)</p><p>　　S Total helical length of screws (mm)</p>

12、;<p>　　t Temperature (℃)</p><p>　　T Residence time (min)</p><p>　　a Overlap angle of screw fights (degrees)</p><p>　　d Calender gap (mm)</p><p>　　e Side clearanc

13、e (mm)</p><p>　　q Product density (g/mm3 )</p><p>　　/ Helix angle (degrees)</p><p>　　* Corresponding author. Fax: +01525-863277; e-mail: b.clarke@cran-</p><p>　　®e

14、ld.ac.uk</p><p>　　0260-8774/99/$ ± see front matter©1999 Elsevier Science Ltd. All rights reserved.</p><p>　　PII: S 0 2 6 0 - 8 7 7 4 ( 9 9 ) 0 0 0 4 9 – 7</p><p>　　1. Int

15、roduction</p><p>　　Extrusion cooking is finding ever increasing applications in the food process industry. Apart from providing a means of manufacturing new products, it has successfully revolution is many c

16、onventional 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,

17、roller and screw type extruders (Frame, 1994). The screw extruders are very different to the</p><p>　　Fig. 2. Plan drawing of the twin screw extruder with drive system. 1-V belt pulley, 2-gear box, 3-food se

18、al, 4-¯ange clamp bolt, 5-die plate, 6-die, 7-two segments of the extruder chamber, 8-extruder screw.</p><p>　　were made so that they could be externally screwed to the die plate.2.5. Drive system The m

19、achine was driven by an electric motor of 2.2kW using a twin belt drive between the motor and a gearbox shown in Fig. 2. The speed reduction in the box was2.08 while an electronic speed controller was used to control the

20、 speed continuously over the range required.</p><p>　　Fig. 3. Front portion of barrel showing provision for heaters, temperature and pressure sensors. 1-slots for heaters, 2-end flanges, 3-side flanges to ba

21、rrel, 4-hole for pressure sensor, 5-twin holes to form the barrel.</p><p>　　2. Motor power</p><p>　　In twin screw extruders the motor power is utilized mainly to compress and shear the food dou

22、gh that squeezes through various gaps in the intermeshing screws and the gap between the screws and the barrel. When dealing with a wide range of foods under different process conditions the shear resistance can vary wid

23、ely because of changes in the rheological behaviour which would prevent accurate estimate of the motor power. Owing to the unknown character therefore of the novel materials a motor power</p><p>　　3. Gear bo

24、x</p><p>　　In the co-rotating extruder the two screw shafts are driven at the same speed in the same direction. The main problem is that they are very close together. The gearbox was designed to drive two pi

25、nions, coupled to the shafts by shear pins, by using a gear wheel of more than double the width of the pinions. In this way the two pinions could ®t side by side driven simultaneously and maximise their diameter spa

26、ce as shown in Fig. 2. Lubricated phosphor bronze thrust bearings were used to resist the</p><p>　　2.6. Heating and temperature control</p><p>　　Heating of the barrel to give necessary thermal i

27、nput for cooking the food was done by two sets of cartridge heaters having capacities of 800 and 1200 W. The heaters were positioned in the grooves made on the top and bottom of the barrel towards the die end as shown in

28、 Fig. 3. A single temperature controller was set up together with a thermocouple to sense the temperature inside the barrel very close to die plate. Owing to the shortness of the barrel only one thermocouple was consider

29、ed necessar</p><p>　　4. Pressure sensor</p><p>　　Pressure measurements are not so important in the commercial production processes as it cannot be directly controlled to monitor the product char

30、acteristics. Neither was such a device needed as a safety measure as this was covered by an overload cut out on the electrical supply. However, in experimental work the measurement of pressure is useful to ascertain the

31、relationship between the pressure and the other controllable parameters such as die size, temperature, moisture content and speed. In t</p><p>　　Fig. 4. Position of pressure and temperature sensors on the ex

32、truder barrel. 1-location of strain gauges on the pressure sensor, 2-cantilever support to plunger, 3-temperature sensor.</p><p>　　5. Testing and evaluation</p><p>　　A range of rice and banana m

33、ixtures were selected as being both novel yet having high potential as processed foods in Sri Lanka. These materials are cheap and common crops in most developing countries and represent an opportunity to produce an attr

34、active, nutritious and tasty snack food. This would provide labour, utilisation of excess perishable fruits in season and a means of storing them for at least one year in appropriate packages. The main product qualities

35、were assessed as part of the sam</p><p>　　variable levels were studied in two sets of experiments. In both sets the throughput was measured when the flow became stable.</p><p>　　Initial trials i

36、ndicated no significant difference in performance due to the variable pitch screws as a means of compressing the feed so all subsequent trials and the results quoted in this paper are for the fixed pitch screws. The extr

37、udate diameter was measured using a vernier calliper immediately after extrusion and before any further drying took place which could cause some further reduction in ratio but not to affect the general result. All tests

38、were replicated three times making 48 indivi</p><p>　　Experiment 1</p><p>　　Fixed settings:</p><p>　　Speed (N) 125 rev/min</p><p>　　Die size (a) 5 mm diameter</p>

39、<p>　　Variables:</p><p>　　Barrel temperature (t) two levels (100°C and 120°C)</p><p>　　Feed moisture content (M) four levels (15%, 20%,</p><p><b>　　25%, 30%)&

40、lt;/b></p><p>　　Experiment 2. This experiment was carried out using fixed settings of barrel temperature and the feed moisture determined in experiment 1 on the basis that maximum product expansion repres

41、ented the best quality.</p><p>　　Fixed settings:</p><p>　　Barrel temperature (t).120°C</p><p>　　Feed moisture content (M).15%</p><p>　　6. Testing and evaluation<

42、;/p><p>　　A range of rice and banana mixtures were selected as being both novel yet having high potential as processed foods in Sri Lanka. These materials are cheap and common crops in most developing countries

43、 and represent an opportunity to produce an attractive, nutritious and tasty snack food. This would provide labour, utilisation of excess perishable fruits in season and a means of storing them for at least one year in a

44、ppropriate packages. The main product qualities were assessed as part of the sam</p><p>　　variable levels were studied in two sets of experiments. In both sets the throughput was measured when the flow becam

45、e stable.</p><p>　　Initial trials indicated no significant difference in performance due to the variable pitch screws as a means of compressing the feed so all subsequent trials and the results quoted in thi

46、s paper are for the fixed pitch screws. The extrudate diameter was measured using a vernier calliper immediately after extrusion and before any further drying took place which could cause some further reduction in ratio

47、but not to affect the general result. All tests were replicated three times making 48 indivi</p><p>　　Experiment 1</p><p>　　Fixed settings:</p><p>　　Speed (N) 125 rev/min</p>

48、<p>　　Die size (a) 5 mm diameter</p><p>　　Variables:</p><p>　　Barrel temperature (t) two levels (100°C and 120°C)</p><p>　　Feed moisture content (M) four levels (15%

49、, 20%,</p><p><b>　　25%, 30%)</b></p><p>　　Experiment 2. This experiment was carried out using fixed settings of barrel temperature and the feed moisture determined in experiment 1 on

50、 the basis that maximum product expansion represented the best quality.</p><p>　　Fixed settings:</p><p>　　Barrel temperature (t).120°C</p><p>　　Feed moisture content (M).15%<

51、;/p><p><b>　　Table 1</b></p><p>　　Results of Experiment 1 (Die orifice diameter=5 mm, screw speed=125 rpm)</p><p>　　Temperature (°C) Feed moisture (%) Throughput (g/s)

52、 Expansion ratio Pressure (MN/m2)</p><p>　　100 15 3.76 1.01 2.97 100 20 2.56 1.00 2

53、.38 </p><p>　　100 25 2.04 1.00 1.83 100 30 1.25 1.00 1.38 </p&g

54、t;<p>　　120 15 2.16 1.06 2.91 </p><p>　　120 20 2.00 1.05 2.07 &l

55、t;/p><p>　　120 25 1.18 1.01 1.59 </p><p>　　120 30 1.02 1.00 1.38</p&

56、gt;<p>　　Variables:</p><p>　　Die orifice diameter (a) two levels (3, 4 mm)</p><p>　　Speed (N) four levels (100, 125, 150, 175 rev/min)</p><p>　　4. Results and discussion</

57、p><p>　　4.1. Machine performance</p><p>　　Generally the extruder performed very satisfactorily.The extrudates produced by the machine were fairly well expanded. During extrusion operations it did n

58、ot become necessary to dismantle the barrel lengthways by splitting into two halves as it never seized up. In order to clean the screw and barrel the latter barrel was very easily pulled o. from the screws within a few m

59、inutes after extrusion. This was in part due to a shorter than usual barrel length. This suggests that the horizontal splitti</p><p>　　problems due to a temperature rise close to the feed hopper. This happen

60、ed because some heaters were installed a little too close to the feed point so these were later removed and the difficulties were overcome as mentioned earlier. Many extruders have cooling facilities in this region but t

61、hese were not found to be necessary. Those heaters further from the feed point and close to the die end proved to be sufficient to gelatinize the rice grits. The extrudate was observed to change from a powder</p>

62、<p>　　7. Extruder settings and product characteristics</p><p>　　It can be seen from Table 1 and Fig. 5 that the throughput dropped with each increase of feed moisture content at both the barrel temperat

63、ures used. When the feed moisture was increased from 15% to 30%, the throughput was reduced by 66.8% and 52.7% at 100℃ and 120℃barrel temperatures, respectively. This effect was probably caused by an increase in backflow

64、 allowed by the reduced viscosity which the increase in moisture produced. Another important observation made was the variation of product exp</p><p>　　The results of Experiments 2 are tabulated in Table 2 b

65、elow.</p><p>　　Fig. 5. Throughput as a function of feed moisture content with die diameter 5 mm and screw speed 125 rev/min.</p><p>　　Fig. 6. Pressure and expansion ratio as a function of feed m

66、oisture content at feed moisture 15%, die diameter 5 mm and screw speed 125 rev/min</p><p>　　Fig. 7 and Table 2 show that the throughput increased with the speed due to increased rate of material conveyance.

67、 The pressure changes with screw speed was not found to be significant. The product expansion, however, showed a downward trend with the increase of speed as evident from Fig. 8. This reduction can be attributed to the r

68、eduction of pressure and lower degree of gelatinization due to reduced residence time. At settings of 125 rpm, feed moisture 15%, temperatures 120°C, die size 3 or 4 </p><p>　　The overall performance of

69、 the machine was found to be quite satisfactory in achieving all the parameter settings and measurements required. Each trial only lasted a few minutes in running time which was mainly spent in reaching equilibrium condi

70、tions indicated by the temperature reading but after 48 trials no significant wear was observed even though the prototype was in mild steel.</p><p>　　Cleaning and maintenance was quick and simple and in the

71、event of a complete seizure of the screws the barrel could be split on this machine.</p><p>　　The gearbox was of a bolted construction to permit modifications but future designs should be welded together. Th

72、e 2.2 kW motor was found to be amply capable and most of the time it only consumed about 0.5kW. No mechanical breakdowns were experienced.</p><p>　　The prospects for use of this design in developing countrie

73、s seem to be good from these experiments. Scale up to a higher capacity would bring some difficulties as discussed by Levine (1989); Singh, Smith and Frame (1998) and Yacu (1992) and although these issues were not addres

74、sed they are not considered to be insurmountable.</p><p>　　Fig. 7. Throughput as a function of speed with feed moisture 15% and barrel temperature 120°C.</p><p>　　Fig. 8. Pressure and expan

75、sion ratio as a function of speed with 3 mm die size, feed moisture 15% and barrel temperature 120°C.</p><p>　　8. Conclusions</p><p>　　The following conclusions were made from this study.&l

76、t;/p><p>　　· Simplified extruders for specialised applications can successfully be made and operated in less developed countries to process local food materials.</p><p>　　· All components

77、 can be made in an unsophisticated workshop except gears, seals, motor, temperature</p><p>　　sensor and heaters.</p><p>　　· Simple machining processes such as drilling and boring can be use

78、d to produce twin holed barrels to accommodate the intermeshing screws. Horizontal splitting of the barrel is not essential in this type of</p><p>　　machine so that fabrication of the barrel for these machin

79、es can be simple enough for developing country manufacture.</p><p>　　· A simple construction of gear box, using straight spur gears driven by a single large gear wheel is quite adequate to run the twin

80、screws in the same direction.</p><p>　　· An attractive and acceptable snack food was produced from the prototype machine from mixture of cereals and fruits.</p><p>　　References</p>&

81、lt;p>　　Frame, N. D. (1994). The technology of extrusion cooking. Blackie Academic and Professional, London.</p><p>　　Gamlath, G. G. S. G. (1995). Nutritional, Physico-chemical and sensory evaluation of ex

82、truded cereals with perishables. Ph.D. thesis, Cranfield University, Bedford, England.</p><p>　　Harlow, N. (1985). Revolutionising a cereal need. Food Processing, pp. 29-30.</p><p>　　Harper, J.

83、M., & Jansen, G. R. (1985). Production of nutritious precooked foods in developing countries by low cost extrusion</p><p>　　Technology. Food Review International, 1, 27± 97.</p><p>　　Ha

84、rper, J. M. (1979). Food extrusion: critical reviews in food science and nutrition. Florida: CRC press.</p><p>　　Harper, J. M. (1992). A comparative analysis of single and twin screw extruders. In J. L. Koki

85、ni, C.-T. Ho & M. V. Karwe, Food</p><p>　　extrusion science and technology. New York: Marcel Dekker.</p><p>　　Hauck, B. W. (1985). Comparison of single and twin screw extruders- 2. Food Trad

86、e Review (Suppl. 5-9).</p><p>　　Hauck, B. W., & Ben Gera (1987). Single and twin screw extruders. Milling, pp. 18±20.</p><p>　　Jansen, G. R., & Harper, J. M. (1980). Applications of

87、 Low cost extrusion cooking to weaning foods in feeding programs. FAO</p><p>　　Food and Nutrition, 6(1), 2-9; (1) 15-23.</p><p>　　Jansen, L. P. B. (1978). Twin screw extrusion. Amsterdam: Elsevi

88、er.</p><p>　　Levine, L. (1989). Scale-up, experimentation and data evaluation. In C. Mercier, P. Linko & J. M. Harper, Extrusion cooking (pp. 57-90). USA, DC: American Association of Cereal Chemists.<

89、/p><p>　　Martelli, F. G. (1983). Twin screw extruders- A basic understanding. New York: Van Nostrand Reinhold.</p><p>　　Rossen, J. L., & Miller, R. C. (1973). Food extrusion. Food Technology (C

90、hicago), 27(8), 46-53.</p><p>　　Ryder, G. H. (1953). Strength of materials (pp. 259-261). LondonW8: Cleaver-Hume Press.</p><p>　　Seiler, K. (1984). Extrusion cooking and Food processing. Food Tr

91、ade Review, 124/127.</p><p>　　Sahagun, J. (1977). Parameters a.ecting the performance of a low cost extrusion cooker. M.S. Thesis, Department of Agricultural and Chemical Engineering, Colorado State Universi

92、ty, Fort Collins,USA.</p><p>　　Singh, N., Smith, A. C., & Frame, N. D. (1998). E.ect of process variables and monoglycerides on extrusion of maize grits using two sizes of extruder. J. Food Engrg., 35(1)

93、, 91-109.</p><p>　　Smith, A. (1986). Cooker extruder die design-some fundamentals.</p><p>　　Food Trade Review, 56, August 1986, Impulse Food Suppl. (6-12).</p><p>　　Yacu, W. A. (199

94、2). Scale-up of food extruders. In J. L. Kokini, C. Ho & M. V. Karwe, Food Extrusion Science and Technology (pp. 465 -472). New York: Marcel Dekker.</p><p>　　Van Zuilichem, D. J., Stolp, W., & Jansse

95、n, L. P. B. M. (1984). Engineering aspects of single and twin screw extrusion cooking of bio-polymers. In R. Jowett, Extrusion Cooking Technology. Amsterdam: Elsevier.</p><p>　　一個簡化雙螺桿旋轉食品擠壓機：設計，制造和檢驗</p&

96、gt;<p>　　S.A.M.A.N.S.Senanayake,B.Clarke</p><p>　　農業(yè)的和耕地工程學的分割。斯里蘭卡的開放型大學， 納瓦拉 ，，斯里蘭卡</p><p>　　技術部，農業(yè)、食物和環(huán)境的學校，悉爾索農業(yè)大學，克蘭菲爾德大學，悉索爾，貝德福德郡，MK45 4DT,UK</p><p>　　收到1998年7月6日;接受19

97、99年2月10日</p><p><b>　　摘要</b></p><p>　　一個簡化雙螺桿旋轉食品擠壓機的設計，制造和測試在英國，之后在斯里蘭卡廣泛的測試應用。它是作為一個模式來滿足特定的產品和金融限制，較不發(fā)達國家，預計將在這些國家擴大生產能力，膨化食品。機器有一個 10 公斤／小時的估計輸出而且主要是碳鋼所做。螺旋的兩類型被做了，一個有固定攤位的14毫米和其他

98、不同的音高段14, 12和10 mm。這個機器是采用變頻電機與電子速度控制。該機也有電加熱溫度控制器和一個壓力感應裝置。制造成本的估計2000歐元，大多數部分建立在一個相當簡單的工作坊。一個米的混合物和干燥的香蕉成功地當做潛在的點心食物和根據最大展延被擠出，最好的結果從一個 120 的滾筒式打印機溫度被獲得℃，螺旋加速 125個轉/每分，輸送水分 15%而且與一鋼模囗 3 毫米的尺寸相當。當其它可能的壓縮螺旋被測試非常相似的結果與沒有產

99、品展延中的重要的改良一起達成。1999全文電子期刊公司。版權所有。</p><p>　　關鍵詞：雙螺桿擠出機，設計低成本，休閑食品，連續(xù)蒸煮器，地方建設，谷類混合物</p><p><b>　　1.驅動系統(tǒng)</b></p><p>　　這臺機器是由電機和齒輪箱之間使用雙皮帶傳動的電動機（220KW）驅動的（圖2）。箱子減速器是用電子調控器來達到

100、持續(xù)變化范圍內的速度的要求的。</p><p>　　圖2用傳動系統(tǒng)的對螺旋擠壓機的平面圖制圖。單一三角皮帶滑車 2-齒輪箱、 3 食物的封囗，4-凸緣夾子螺栓， 5 一鋼模的屏，6-一鋼模，擠壓機室的 7- 兩個片段，8-擠壓機轉。</p><p><b>　　電機功率</b></p><p>　　在雙螺桿擠出機電機功率的利用主要壓縮和剪切食物

101、生面團擠壓，通過各種差距在嚙合螺絲和螺絲之間的差距和桶。當處理一個范圍廣泛的食品不同工藝條件下的剪切阻力可能差異很大，因為變化的流變行為，防止準確的電機功率。由于未知的變化和新奇材料等，一個馬達的能力被選擇了基于一個安全界限和從布拉班德擠壓機的探索試驗在相似的按規(guī)定尺寸制作擠壓機中為相似的材料。羅森 和銑床為從 0.02 到 0.10KWh/kg 的不同的擠壓機提供多種比能量消費數據。在10kw吞吐量時，這給一個1kw的最大動力要求而布

102、拉班德審訊傾向于表明一個相關的電源要求這個的一半值。2.2 KW，被用的 3 相位交流電動機加上所有其他磁盤摩擦損失等供給充足有能力。</p><p><b>　?。?）齒輪箱</b></p><p>　　在同向旋轉擠壓機中，螺旋橋以相同的方向和相同的速度被驅使。主要的問題是他們在一起非常接近。齒輪箱被設計成駕駛兩個小齒輪，藉著剪梢對橋加倍了，藉由使用齒輪比倍更多小齒

103、輪的寬度。這樣，這兩個小齒輪會并排安裝并且同時地驅使，如圖 2 所顯示的他們的直徑空間增加至最大限度.被加油的磷青銅推力方位被用來抵抗沿著事物產生的橋方向的負載。</p><p><b>　　2.加熱與溫度控制</b></p><p>　　滾筒式打印機的加熱給煮熟食物的必需的熱輸入分兩組卷筒加熱器有800W 和1200W的容量。加熱器在槽─向如 Fig.3 所顯示的一