玉米脱粒机工作过程分析及优化设计【含CAD图纸、SW三维模型】
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毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文 译文题目：Investigation of the maize ear threshing process玉米脱粒过程的研究 学生姓名： 学号： 专业： 机械设计制造及其自动化 所在学院： 机电工程学院 指导教师： 职 称： 年 3月 3日Investigation of the maize ear threshing processS. Petkevichiusa ,L.Shpokas ,H.-D.KutzbachbWet maize ears of the Benicia variety with a moisture content of 32.5% and medium dry maize ears of Attribut variety with a moisture content of 18.5% were fed in parallel and perpendicular to the drum shaft of a conventional threshing drum. Maize ears fed in parallel with the drum shaft in the concave clearance moved twice as fast (45 m s1),received twice as few (57) rasp bar impacts, and 1020% of the threshed grain passed through the concave when compared to threshing with the maize ears fed perpendicular to the drum shaft.Threshing losses of wet Benicia maize ears did not exceed the permissible range of0.5% when drum rasp bars moved at the speed of 16 m/s and the concave clearance was in the front 21 mm and at the end 6 mm (216 mm). When medium dry Attribut maize ears were threshed, the concave clearance was in the front 27 mm and at the end 15 mm. When maize ears were fed perpendicular to the drum shaft, the clearance could be increased by 2 mm as the maize ears moved through the concave at an approximately 1.8 m/s slower speed, and received 8 additional rasp bar impacts. During the threshing of wet Benicia maize ears the threshing damage was 30% greater as compared with the threshing damage of medium dry maize ears of Attribut variety. Wet maize should be immediately crushed and preserved as silage.1. IntroductionMaize production is increasing in Europe as maize crops are grown not only for a silage and grain but also for biogas production. Since 2000, maize varieties with shorter vegetation periods have been grown in Lithuania. In good weather conditions the grains in ears mature to 35% moisture content after which they are harvested during the second half of October (Bulgakov et al., 2006). However, it is not economic to dry such grains to a14%moisture content. Thus, a new wet maize processing technology was tested (Shpokas & Petke-vichius, 2005). When the maize moisture reached 35%, the ears were harvested using the corn head, maize grains wereCrushed on-site, and the silage was kept in a trench. However, the threshing process of the wet maize ears was not investigated and the optimum parameters for the threshing apparatus were not determined.The most important quality indices for maize ears threshing are grain loss, damage, concave separation, and the degree of the ear length reduction. The threshing process depends on the maize variety characteristics, the design and structure of the threshing apparatus, and its adjustment.Kravchenko and Kuceev (1979) determined that adhesion between a grain and the maize cob depends on the grain moisture content and its location on the ear. At the ear base kernel attachment is the strongest and at the top it is the weakest. As grains dry, their adhesion to the cob increases. In order to detach grains from the cob some force should be applied longitudinal or perpendicular to the ear axis (Kravchenko & Kurasov, 1988; Danilevich, 1961). When threshing the ears approximately 66% of power is used to overcome the friction forces between the grains and only 34% of power is used for the ear deformation (Kelemen, 1967; Kurasov & Kuceev , 1999). The main influences on maize threshing are the gap between drum rasp bars and the concave and the drum peripheral velocity. Rudakov (1962) established that the ear diameter decreases during the threshing; thus, the clearance at the concave end should be less than that at the concave front. He also stated that the speed of the threshing drum rasp bar of (7 m/s) was not sufficient to separate grain from the ear .Kravchenko and Kuceev (1987) found that the optimum speed of the threshing drum rasp bar was 11 m/s. This was about 2.5times less than the movement speed of the rasp bars when the grain crops were being threshed ( Gasparetto et al., 1977).Most investigations of the threshing of ears with a medium moisture content concentrate on grain damage. Wacker (2005) found that the least maize grain damage (11%) occurred when the moisture content was 28% wet basis. On threshing of maize grains on a41% moisture wet basis, grain damage increased to 33%.Wacker (1987) also stated that grain damage from an axial threshing machine is less that of a tangential machine. Data obtained by Vindizhev and Blaev (1983)showed that maize grain damage occurred when the drum rasp bars operated at a rate of 7 m/s and their impact direction coincided with the longitudinal axis of a grain .When the impact direction is at an angle with the grain longitudinal axis, the damage appears at rasp bar speeds of15 m/s. During the harvesting of maize the number of ears fed to the threshing drum varies considerably. It has been shown (Jakumenkov, 1965) that the grains damage increases with an increase of ears feed rate .Kustermann (1987)states that during the first impact of the rasp bar the greatest number of grain are threshed. The degree of grain threshing depends on the ear orientation with respect to the drum shaft position (Kuceev, 2000). When the ear axis is parallel to the drum shaft grain threshing losses are 2.3 times lower than in case of threshing the ears fed perpendicular to the drum shaft.Most research into maize threshing has evaluated the ear threshing process with respect to grain damage and grain loss during threshing. However, the reasons for grain damage or loss during the threshing do not often evaluate the movement of ears in the threshing apparatus. Crop movement in the threshing apparatus was investigated by Gasparetto et al. (1989) and ear movement by Rudakov (1962), who found that the threshed dry ear in the concave moved 4 times slower than the threshing drum rasp bars and that the threshed grains moved in several directions in the threshing apparatus .The threshing of ears with a moisture content greater than30% has not been fully investigated because grain moisture should be less than 30% when maize ears are harvested for storage. The objectives of this research were to determine the influence of the drum peripheral velocity and concave clearance on the ear feed rate through the concave, the number of rasp bar impacts, grain damage, separation, the degree of the cob crumble, and to determine the optimum adjustments of the threshing apparatus.2. Material and methodsBiometric indices of maize ears were determined by measuring the length and diameter of 100 ears of different varieties (measurement accuracy of 0.1 mm) and counting the number of vertical and horizontal grain rows. The mass of the grains, ears, and 1000 grain mass (measurement accuracy of 0.1 g) was evaluated at 14% moisture content.The aerodynamic properties of the grain were determined the using a test rig for determining terminal velocity which varied air-flow from 5 to 20 m/s. Grain samples of 500g were replicated three times and divided into five groups. The variation of grain terminal velocity was calculated and an integral curve of grain dispersion constructed.The moisture of grains (U1) and cobs (U2) has been determined during drying. Five samples of grain and cob pieces were heated in the drying oven for 24 h at 1051C.The process of maize threshing was tested in Hohenheim University (Germany) using a test rig (Fig. 1), that consisted of a six-rasp-bar threshing drum (2), whose diameter was 0.45m and width was 0.5 m. The concave (8) surrounded the drum at an angle of 951. It consisted of a metal sheet with 10perpendicular rows of holes; the length of the rows was40 mm and the width was 19 mm. There were transverse bars welded between the rows of holes and the width and the height of the bars was 10 mm. The concave was divided into five equal parts the area of each was 0.047 m2. The threshed materials passing through different parts of the concave were collected into separate trays (1014), weighed, and then cleaned. The grain was weighed (measurement accuracy of 0.1 g) and the grain separation through the first part (0.141 m2) and the second part (0.094m2) of the concave was calculated.The average cob length was calculated from the measurements of 50 maize cobs thrown from the concave (measurement accuracy of 0.1 mm). Five grain samples of 50g screened through the concave were taken, the damaged grains were separated, and the average grain damage was estimated.Ears of Benicia and Attribut maize varieties were threshed. The threshing drum peripheral velocity (Vb), the concave clearance (a), and the ear position with reference to the drum shaft were varied during the tests. The ears were fed into the threshing apparatus either parallel or perpendicular to the threshing drum shaft (Fig. 1). When placed on the guideboard they were pushed until the drum rasp bar touched the ear. The ear threshing process, the passing of the ear through the concave surface, grain separation, and movement in the threshing clearance were recorded using a high-speed 4500 frames s) camera and images were analysed with a Kodak Ektapro HS 4540mx motion analyser. This enabled the ear and grain behavior during its movement through the concave, the average velocity of the ear movement, and the number of impacts of the rasp bars to be determined.The permissible range of threshing loss (0.5%) and the grain fraction thrown from concave to the straw walkers (20%)determine the main parameters of the threshing apparatus .Grain damage was not as important since wet maize should be immediately crushed and preserved as silage.Statistical tests were carried out using Analysis of Variance and significance tests. Confidence intervals for mean values were calculated using 0.95probability. 3. Results3.1. Biometrical indices of maize earsThe biometric indices of ears of maize varieties Benicia andAttribut grown in Germany, and maize variety G12 grown in Lithuania, are shown in Table 1.The most important biometric indices are the diameter of the maize ear and its cob. This is because at the front part of the concave the clearance must be less than the ear diameter and at the end of the concave this clearance must be less than the cob diameter. The average diameter of the ears and cobs from Germany and Lithuania varied approximately by 3 mm. Ear length has little influence on the threshing process. Thus, he results of investigations of ear threshing in Germany could be used in Lithuania for preparing the combine-harvesters for the maize ear harvesting.表.13.2. Maize grain aerodynamic characteristicsWhen the threshing drum rotates the rasp bars and the coverings cause an air-flow. To avoid grain being blown onto the straw walkers this air-flow should be less than the terminal velocity of the grain. The tests showed that roughly10% of threshed grains had a terminal velocity less than11 m/s (Fig. 2).3.3. Investigation of the maize ear threshing processWet Benicia ears (moisture contentU132.5%) and mediumdry Attribut ears (U118.5%) were threshed whilst being fed in parallel with the drum shaft of the threshing drum. The rasp bar movement speed was varied from 12 to 20 ms.When the threshing drum rasp bars moved 12 m/s (Fig. 3a), the threshing losses of the wet Benicia ears as the threshed grains passed through the concave were 27% and 42%. When the rasp bar speed was increased to 20 m/s, threshing losses of the grain were decreased to 5%, but this exceeds the permissible 0.5% rate. The grain separation through the concave increased to 71% and grain damage increased from10% up to 23% (Fig. 4).When drum rasp bars moved at 12 m/s, at the concave front (gap of 29 mm) the ear rolled to the third transverse bar before threshing started. After rasp bars had pushed the ear further behind the sixth transverse bar (gap of 22 mm), grain was being threshed intensively, but 58% of the threshed grain was unable to pass through the concave (Fig. 3a). The cob was thrown out from the concave after five impacts of the rasp bar (Fig. 5b). The ear moved at an average speed of 4.5 m/s through the threshing zone (Fig. 5a).When the drum rasp bar speed was increased to 20 m/s, the speed of the ear through the concave increased up to6.3 m/s (Fig. 5a). Most of the grains were threshed between the third and seventh transverse bars of the concave; thus, only about 30% of threshed grains did not pass through the concave. Grain threshing losses were minimised to 5% (Fig. 3a). When the wet ears were threshed the clearance between the drum and the concave should be reduced to allow the threshed grains to pass through the concave and as a result less than 20% of threshed grains would be thrown onto the straw walkers. When the medium dry Attribut ears (Fig. 3b) were fed parallel to the drum shaft, drum rasp bars moved at 12 m/s, more grains were threshed at the concave front compared with the threshing of Benicia ears. After every impact of the rasp bar the ear rose up from the concave to the drum between rasp coverings. Grain was most intensively threshed when the ear moved between the third and the fifth transverse bars of the concave. Threshing losses, the part of grain that passes through the concave, and damaged grains were 1.5%, 76% and 4%, respectively (Fig. 4). Grain threshing losses of ears of the Attribut variety did not exceed the permissible rate when the rasp bars moved 15 m/s, but more than 20% of the threshed grains were thrown on to the straw walkers (Fig. 3b). Also 78% of the threshed grains passed through the concave and 7% of the grain was damaged (Fig. 4).The average movement speed of the ear through the concave was about 4 m/s. The optimum speed of the drum rasp bars was 16 m/s because at that speed less than 20% of the threshed grains were thrown from the concave.Following analysis of test results the conclusion was drawn that a drum rasp bar speed of 16 m/s is too high for threshing medium dry grains of Attribut ears fed in parallel to the drum shaft when the concave clearance was 2918 mm. The impact of drum rasp bars moving20 m/s was insufficient to thresh grains of wet Benicia ears. As a result the concave clearance had to be reduced to produce acceptable threshing at the front of the concave.When wet and dry ears were threshed and drum peripheral velocity was varied, threshed grains in the concave moved in several directions, changing direction after striking the concave, the drum rasp bars, or the coverings. The air-flow caused by drum rotation was sufficient to keep some part of the grains suspended in the air and even to be blown from the concave.When Benicia ears were fed perpendicular to the drum shaft (vb20 m/s ; a298 mm) at the front of the concave they remained on the two parallel bars or the tops of the ears caught on the third transverse bar. The drum rasp bars bent the ear, some grains were threshed, but the ear did not move forward. After six rasp bar impacts, when some of the grain had been threshed, the ear started to be pushed forward. The ear was broken into two pieces and these parts moved forward chaotically, changing directions. After twelve impacts of rasp bars (Fig. 5b) cob pieces of approximately 65 mm were thrown from the concave.Grain threshing losses were reduced to 3% (Fig. 6a), but exceeded the permissible rate by 0.5%, the grain separation through the concave was 83%, and more than 40% of the grain was damaged (Fig. 4). The ear moved in the concave at approximately 4 m/s.Twelve impacts of rasp bars moving at a speed of 20 m/s were insufficient to thresh wet Benicia ears. When wet ears were threshed the clearance at the concave front had to be reduced in order to thresh more grains.Attribut variety ears fed perpendicular to the drum shaft(Fig. 6b) were threshed after thirteen impacts of rasp bars moving at 15 m/s (concave clearance 2918 mm). The ear moved in the concave at 2.2 m/s (Fig. 5a). Grain losses during threshing did not exceed the permissible rate, 84% of grains passed through the concave, cobs were not broken, and their average length did not exceed 160 mm. Thus, when the clearance between the drum and the concave was 2918mm the optimum speed of the drum rasp bars was 15 m/s.Threshing losses of grains, the grain separation through the concave, and grain damage were determined whilst changing the concave clearance from 216 to 3730 mm. When Benicia ear was fed in parallel with the drum shaft (Fig. 7a) and when the gap between rasp bars and the concave was 216 mm, threshing losses of the grain made up 1.4%, 86% of all threshed grain passed through the concave, and 33% of grain was damaged (Fig. 8). Grain losses during the threshing exceeded the permissible level as the ear moved through the concave, rotated about its axis, and jumped, the rasp bars broke it into two pieces, and thus their average length was96 mm. The average speed of the ear through the concave was 4.5 m/s, and it received five impacts from the rasp bars (Fig. 9). The drum rasp bars had to move at the speed of18 m/s in order not to exceed the permissible grain loss during threshing and less than 20% of the threshed grains were thrown onto the straw walkers.When medium dry Attribut ears were fed in parallel with the drum shaft, the optimum concave clearance was2715 mm, because after seven impacts of rasp bars the threshing losses of grains were less than the permissible rate,80% of threshed grains passed through the concave (Fig. 7b),and 8% of the grains were damaged (Fig. 8). The average speed of the ear through the concave was 4.6 m/s (Fig. 9a).When Benicia ears were fed perpendicular to the drum shaft with the concave clearance set at 238 mm (Fig. 10a),88% of grains passed through the concave, but 37% of threshed grains were damaged because the ear moved through the concave at a speed of 2.8 m/s, and they received eight impacts from the rasp bars. The greatest number of rasp bar impacts (from five to eight) occurred at the front part of the concave and it pushed the ear forward. Concave clearance must be such that after the impact of the rasp bar the ear rises from the concave and the next rasp bar pushes it forward. When medium dry Attribut ears were fed perpendicular to the drum shaft and the concave clearance was 2918 mm, the threshing grain losses did not exceed the permissible rate, 84% of grain passed through the concave (Fig. 10), 7% of grain was damaged, the ear moved through the concave at 2.2 m/s (Fig. 9), and it received 13 impacts of the rasp bars. The drum rasp bars bent the ear whilst moving it along its axis and slowly threshing grains. After a significant part of the grains was threshed, and the cob rose from the concave it was hit with a rasp bar and the next rasp bar began to push it forward. When the ear moved through the concave, it was rarely broken into two pieces; thus, the average length of cob thrown from the concave was 150 mm. 4. ConclusionsThe analysis of wet Benicia and medium dry Attribut ears showed that the grain moisture content, the position of the threshed ear with reference to the drum shaft, the drum peripheral velocity, and the concave clearance influenced the threshing losses of grains, their separation through the concave, and grain damage.In order to thresh wet Benicia ears with losses less than0.5% and less than 20% of threshed grains thrown from the concave, drum rasp bars should move at 18 m/s, the clearance at the front of the concave should be equal to the cob average diameter (21 mm), and the clearance at the end should be about 6 mm.Wet Benicia ears fed perpendicular to the drum shaft were threshed more intensively at the front part of the concave compared with ears fed parallel because they received twice as many rasp bar impacts (12) because they moved through the concave at half the speed. For threshing of the wetBenicia ears the optimum drum peripheral velocity vbwas16 m/s with the clearance between drum rasp bars and concave transverse barsa238 mm. The reduction of the clearance between the drum and concave had a greater impact on grain loss during the threshing than the increase of the rasp bar movement speed.When wet Benicia ears were threshed 40% of grains were damaged; thus, they should be immediately crushed and silage made. When threshed medium dry Attribut ears were fed in parallel with the drum shaft the optimum speed of drum rasp bars was 16 m/s and the concave clearance was 2715 mm. When ears were fed perpendicular to the drum shaft the clearance was 2918 mm. As the ears moved through the concave at half the speed compared to ears fed parallel with the drum shaft, they received twice the impacts of the rasp bar (13) and 10% more threshed grains passed through the concave. Grain damage was about 19%.The analysis of the threshing process helped to determine that the grains moved longer distances than the ear in the concave clearance. Grains moved in various directions after they hit the drum rasp bars, its coverings, and the concave. Some part of the grains moved in the air-flow produced by the drum or were thrown from the concave. To increase grain separation through the concave, the concave with the greatest active separation area should be used, and the adjustment of threshing apparatus should be changed following estimation of the ear diameter, maturity, and its moisture content.玉米脱粒过程的研究S. Petkevichius ，L. Shpokas ，H.-D. Kutzbach摘要“Benicia”品种的湿玉米果穗含水量为32.5%，“Attribut”品种的中等干度玉米果穗含水量为18.5%。将它们平行或垂直于滚筒轴喂入脱粒机。相比于垂直喂入，玉米穗以平行滚筒轴喂入脱粒机时在凹板间隙移动快了一倍（45米每秒），受到纹杆影响少了一半，且有多于1020%的脱净谷物通过凹板。当滚筒的纹杆以16米/秒的速度转动且凹板间隙为6毫米到16毫米时，“Benicia”品种的湿玉米穗脱粒过程的损失不能超过其允许的范围（0.5%）。“Attribut”品种的中等干度玉米穗在脱粒的时候，凹板间隙在15毫米到27毫米之间。当玉米穗垂直于滚筒轴喂入时，间隙需要增加2毫米，因为玉米穗通过凹板的速度大约下降了1.8毫米/秒。“Benicia”品种的玉米穗的脱粒损失比“Attribut”品种的中等干度玉米穗的脱粒损失多30%。湿玉米需要立即被压碎和保存来作为饲料。1 介绍 玉米作物不止可以作为饲料与粮食还可以作为沼气，因此在欧洲玉米产量增加。在两千年前，立陶宛人就已经种植短植株的玉米。在天气条件良好时，玉米穗成熟时的含水量为35%，一般在下半年十月中旬可以收获。但是，一旦它被干燥到14%时，他就不具有经济性。因此，科学家正在研究一项新的湿玉米加工技术。当玉米的含水率达到35%，玉米穗从顶端开始收获。在种植玉米农场，玉米饲料保存在地窖中。然而湿玉米穗的脱粒过程还没有进行实验，脱粒装置的最优参数还不确定。玉米穗脱粒质量的最重要指标是谷物的损失率、损伤率以及玉米穗长度缩短的程度。脱粒过程依赖于玉米品种特性、脱粒装置的设计和结构。玉米粒与玉米棒之间的附着力主要取决于玉米籽粒的含水率以及玉米籽粒所处于玉米穗的位置决定。处于玉米穗底部的玉米粒的附着力是最强的，顶部则最弱。当对谷物进行干燥后，玉米籽粒的附着力就会降低。为了将玉米籽粒从玉米穗上剥离下来，所施加的力应该是垂直或者平行于玉米穗的。在进行玉米穗脱粒时，约66%的力为与谷物间的摩擦力，约34%的力用来阻碍玉米穗变形。玉米脱粒的主要影响因素是滚筒纹杆与凹板之间的距离以及滚筒的圆周速度。建立玉米穗在脱粒中的模型，在脱粒时玉米穗直径是逐渐减小的，因此凹板末端间隙应小于前端间隙。脱粒时滚筒外围线速度速度（7米/秒）不足以使全部谷粒从玉米穗上脱落。最理想的脱粒滚筒线速度是11米/秒。大多数对于中等水分含量的玉米穗的研究专注于谷粒的损失。研究发现当湿基含水量为28%时，玉米籽粒损伤率最小（11%）。当玉米脱粒时湿基含水量为41%时，谷粒损伤率增加到33%。研究还指出，轴流式脱粒机对谷粒的损伤率小于切流式脱粒机。这些数据由Vindizhev和 Blaev两位学者于1983年发表的论文中获得。谷粒与纹杆以一定的角度进行脱粒，当纹杆速度以15米/秒运行时最容易使谷粒损伤。当收获时玉米穗喂入脱离滚筒的量有很大的变化。科学家Jakumenkov于1965年证明谷粒的损伤率随着玉米穗的喂入速度的增加而增加。科学家Kustermann于1987指出脱离效果的首要影响因素是喂入量。科学家Kuceev于2000指出谷物的脱粒程度取决于玉米穗相对于滚筒轴的位置与方向。当玉米穗平行于脱粒滚筒轴喂入时，其谷粒损失率比垂直喂入低2.3倍。大多数对于玉米脱粒过程的研究是评估玉米脱粒过程的损失以及损伤。然而人们不常研究玉米穗在脱粒装置中的运动状态对谷粒的损伤以及损失的影响。Gasparetto 等学者于1989年对谷粒在脱粒装置中的运动进行研究， Rudakov于1962年对玉米穗的运动进行研究，他们发现干玉米穗在凹板中运动的速度比纹杆的旋转速度低4倍，并且脱落的谷粒在脱粒机中无规则的运动。对于含水率大于30%的玉米穗进行脱粒时的情况并没有进行深入的研究。因为玉米收获后进行存储时，含水率必须低于30%。此次研究的目的是确定脱粒滚筒的圆周速度、玉米穗喂入凹板的速度、纹杆的数量对玉米谷粒损失与损伤的影响，以及调整脱粒装置的最优参数。2 材料与方法玉米穗的生物指标由测量100个不同品种的玉米穗的长度和直径（精确到0.1毫米），并计算横向纵向谷粒的数量来确定。玉米穗的质量和谷粒的质量（精确到0.1克）都是测量自含水率为14%的玉米。通过实验装置测定粮食的空气动力学特性。500克的粮食分成五组，重复测试三次。通过计算末端速度的变化对谷粒分散程度的影响绘制曲线。当谷物晾晒后，谷粒（U1）和玉米棒（U2）的水分含量已经确定。五组实验品在105摄氏度的温度下烘烤24小时。霍恩海姆大学观测玉米的脱粒过程使用了一个实验装置，它由一个直径为0.45米宽0.5米的六纹杆脱粒滚筒组成。凹板围绕在滚筒周围，其角度为95度。它由一个金属薄片组成，上面有10排垂直的孔洞；每排孔长度为40毫米，宽度为19毫米。一根横向的钢筋焊接在孔洞之间，它的高度与宽度都是10毫米。凹板分为五个相同的部分，每个部分的面积为0.047平方米。凹板的五个部分将脱粒后的玉米谷粒收集于单独的托盘上，称重，然后清洗。谷粒的称重精度为0.1克，通过凹板的第一部分（0.141平方米）和第二部分（0.094平方米）进行计算。通过测量50根玉米棒得出其平均长度值（计算精度为0.1毫米）。将被凹板筛选出的五组各50克谷粒样品中的受损谷粒分离出来，计算出平均谷粒损失率。将“Benicia” 和“Attribut”两品种的玉米穗脱粒。脱粒滚筒的圆周速度（vb）、凹板间隙（a）以及相对于滚筒轴的参考位置在测试中都是不同的。将玉米穗以平行或者垂直于脱粒滚筒轴的方向喂入脱粒装置。其落入导板上并被推至与滚筒纹杆相接触。玉米穗的脱粒过程，玉米穗通过凹板表面，经过谷粒分离步骤，谷粒在脱粒的过程都会被一个高速摄像机（4500帧/秒）记录下来并且用柯达运动分析器进行图像分析。这样可以准确测得谷粒在凹板中的运动过程、平均速度、作用中的纹杆数量等参数。3 结果3.1玉米穗的生物统计学指标玉米穗的生物统计学指标。“Benicia”和“Attribut”两种品种的玉米生长在德国，“G12”品种的玉米生长在立陶宛。如表1所示。玉米最重要的生物统计学指标是玉米穗和玉米棒的直径。这是因为凹板的前一部分间隙必须小于玉米穗的直径而后一部分的间隙必须小于玉米棒的直径。来自德国以及立陶宛的不同品种的玉米穗与玉米棒平均直径相差3毫米。而穗的长度对脱粒过程几乎没有影响。因此，对于德国品种的玉米脱粒过程的调查可以运用于立陶宛的玉米品种。这为联合收割机收获不同品种的玉米做准备。表1 玉米穗生物统计学指标指数玉米种类BeniciaAttributG12G12德国立陶宛200420042005玉米穗直径/毫米玉米穗长度/毫米垂直谷粒行数平行谷粒行数谷粒质量/克谷粒数量1000个谷粒质量/克玉米穗质量/克玉米棒质量/克43.30.4468.93.316.00.328.01.0113.08.5422.022.7267.718.214.42.525.10.640.10.6182.14.413.00.334.01.4116.07.5424.027.3273.616.819.22.223.20.441.01.3177.05.014.00.3231.01.13112.07.1395.017.2300.56.216.81.821.90.4242.30.5200.83.913.50.330.00.5132.06.0482.022.0272.911.227.20.924.10.43.2 玉米谷粒的空气动力学特性当脱粒滚筒的旋转纹杆相对于包络表面运动时，就会产生气流。为了避免谷粒被气流吹到逐稿器，气流速度必须小于谷粒的末端速度。测试表明大于10%的脱落谷粒的末端速度小于11米/秒。3.3 玉米脱粒过程的研究将“Benicia”品种的湿玉米穗（谷粒U1行穗率为32.5%）以及“Attribut”品种的中等干度玉米穗（谷粒U1行穗率为18.5%）这两品种平行于滚筒轴的方向喂入脱粒滚筒。纹杆以12米/秒到20米
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