本文選題：割草壓扁機 + 仿形系統(tǒng)��； 參考：《中國農業(yè)大學》2017年博士論文

【摘要】：為了實現(xiàn)苜蓿高效、低損和優(yōu)質收獲,論文從苜蓿刈割壓扁收獲機械工作過程出發(fā),在研究苜蓿莖葉連接力學特性的基礎上,通過虛擬樣機技術與田間試驗相結合,對苜蓿刈割壓扁機的仿形系統(tǒng)和切割壓扁系統(tǒng)的設計參數進行了優(yōu)化,對機械系統(tǒng)在喂入區(qū)產生的氣流場進行了模擬和實測研究。論文進行了苜蓿莖葉連接力學特性研究,為機械系統(tǒng)與苜蓿植株作用過程的研究提供理論參考。對于新鮮苜蓿植株,進行拉伸破壞時的最大載荷值根據破壞方式不同由大到小的排列順序為:順茬拉伸、垂直拉伸和逆茬拉伸;順茬拉伸時莖葉連接點被拉扯破壞,逆茬拉伸時莖葉連接點被撕裂破壞,而垂直拉伸時則處于兩者之間,從力學特性角度分析,收獲時順茬喂入為理想喂入方式。仿形系統(tǒng)是刈割壓扁機實現(xiàn)高效收獲的關鍵,論文建立了仿形系統(tǒng)的虛擬樣機模型,并進行了四因素三水平虛擬正交實驗,以平均割茬高度、割茬穩(wěn)定性系數和割刀觸土深度為優(yōu)化指標,得出仿形系統(tǒng)最佳設計和工作參數為滑掌長度188 mm,割臺傾角4.06°,拉力重力比0.85,前進速度2 m/s。在此條件下,利用仿形系統(tǒng)虛擬樣機仿真的結果為平均割茬高度為69.77 mm,割茬穩(wěn)定性系數為46.96%,割刀無觸土現(xiàn)象。切割壓扁系統(tǒng)是刈割壓扁機實現(xiàn)低損收獲的關鍵,論文通過建立切割壓扁系統(tǒng)的虛擬樣機模型,在不同切割壓扁運行參數下進行了仿真試驗,假設并定義了評判切割壓扁系統(tǒng)對苜蓿植株的破碎作用程度的碎草系數ε的模型,得到切割壓扁系統(tǒng)最佳運行參數為割刀轉速ng=1875 r/min,壓扁輥轉速ny=749 r/min,此時切割壓扁系統(tǒng)對苜蓿植株的破碎作用最小。樣機田間試驗表明:實測碎草率與碎草系數ε呈線性正相關,相關系數平方R2=0.9588,驗證了碎草系數模型的正確性。刈割壓扁機械系統(tǒng)形成的氣流場能輔助完成苜蓿收獲過程,論文利用CFX對喂入區(qū)氣流場進行了模擬計算,發(fā)現(xiàn)了機器前方存在"氣流交匯點",通過對氣流速度分析得出,該交匯點上方、后方和前方的氣流分別能起到避免重割、輔助喂入和利于切割的作用。利用響應面分析得到了關鍵氣流場參數隨切割壓扁運行參數變化的關系模型。對機械系統(tǒng)進行優(yōu)化后的9GYZ-1.2型自走式苜蓿刈割壓扁機,田間作業(yè)的割茬高度為55.5 mm,超茬損失率為0.31%,碎草率為2.32%,壓扁率為98.36%,均達到國家標準對刈割壓扁機作業(yè)質量的要求。與人工收獲的未壓扁的苜蓿相比,利用樣機進行壓扁調制收獲的苜蓿,田間晾曬時的干燥速率明顯加快,樣機壓扁調制取得了理想的效果。
[Abstract]:In order to achieve high efficiency, low loss and high quality harvest of alfalfa, the paper studied the mechanical properties of alfalfa stem and leaf connection, and combined it with field experiment through virtual prototyping technology, based on the working process of cutting and flattening harvesting machine. The design parameters of the copying system and cutting flattening system of alfalfa cutting flattening machine were optimized. The airflow field produced by the mechanical system in the feeding area was simulated and measured. In this paper, the mechanical properties of alfalfa stem and leaf connection are studied, which provides a theoretical reference for the study of the interaction between the mechanical system and alfalfa plants. For fresh alfalfa plants, the order of maximum load during tensile damage was as follows: following stubble stretching, vertical stretching and reverse stubble stretching; The joint point of stem and leaf was torn and destroyed during the extension of the reverse stubble, but it was in the middle of the two in the vertical stretching. From the angle of mechanical properties, the ideal feeding mode was to feed along the stubble at harvest. The copying system is the key to the high efficiency harvest of the cutting and flattening machine. The virtual prototype model of the copying system is established, and the virtual orthogonal experiment of four factors and three levels is carried out to average the stubble height. The optimum design and working parameters of the copying system are as follows: the length of the slide palm is 188 mm, the slope angle of the cutting table is 4.06 擄, the pull gravity ratio is 0.85, and the forward speed is 2 m / s. Under this condition, the simulation results show that the average stubble height is 69.77 mm, the stubble stability coefficient is 46.96, and the cutting knife has no contact with soil. Cutting and flattening system is the key to realize low loss harvest of cutting flattening machine. This paper establishes a virtual prototype model of cutting flattening system and carries out simulation experiments under different cutting flattening operation parameters. Suppose and define the model of breaking coefficient 蔚 of cutting and flattening system to evaluate the degree of fragmentation of alfalfa plants. The optimum operating parameters of the cutting and flattening system were obtained as follows: cutting speed ng=1875 rmin and flattening roll speed ny=749 r / min. At this time, the cutting and flattening system had the least effect on the breaking of alfalfa plants. The field test of the prototype showed that there was a linear positive correlation between the measured sloppiness and the breaking coefficient 蔚, and the correlation coefficient square R _ (2) was 0.958 8, which verified the correctness of the model. The airflow field formed by the cutting and flattening mechanical system can assist in the alfalfa harvest process. In this paper, the air flow field in the feeding area is simulated by CFX, and the "air flow intersection point" in front of the machine is found, which is obtained by the analysis of the airflow velocity. The air flow above, behind and ahead of the intersection can avoid recutting, assist feeding and facilitate cutting. Based on the response surface analysis, the relation model of the key airflow field parameters with the cutting flattening operation parameters is obtained. After optimizing the mechanical system, the 9GYZ-1.2 self-walking cutting and flattening machine of alfalfa, the stubble height of field operation is 55.5mm, the loss rate of excess stubble is 0.31mm, the rate of sloppy crushing is 2.32cm, and the flattening rate is 98.36. All of them meet the requirements of the national standard for the operation quality of cutting flattening machine. Compared with the unflattened alfalfa harvested by artificial harvesting, the drying rate of the alfalfa, which was compressed and modulated by the prototype, was obviously accelerated when it was dried in the field, and the ideal effect was obtained by the flattening modulation of the prototype.
【學位授予單位】：中國農業(yè)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：S817.11

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