新疆棉田塑料残膜回收过程中起膜和残茬分离撕裂机理研究

The cotton cultivated area using plastic film was about 1.5 million hectares in 2014 in Xinjiang, and the yield was about 3300 million kilogrammes. Covered plastic film brought powerful economic intrests to the production of cotton, but simultaneously the cultivated field was severly polluted by plastic film residue because it could not be recycled completely in time. The major causes of less-effective recycling were that the film residue was damaged when removing,and separating plastic film from stubbles, which destroyed the completeness of plastic film and increased the recycling dificulties. The project is to analyze the removing and separation of stiffener plastic film and ordinary plastic film during recycling plastic film residue, the former of which was successfully invented by our research group. The mechanical properties of the tearing process of removing the film residue and the tearing process of separation between film residue and cotton stalk are to be analyzed. The relationship between mechanical properties and geometrical characteristic of the damage of removed film and the avulsion of the sperated film will be confirmed. The mechanical mode of the damage of removed film and the avulsion of the sperated film will be established. The finite element simulation of which is to be carried out and testified by field experiment. By comparing the recycling of stiffener plastic film and ordinary film, the optimal film covering and the recycling of film residue are to be put forward, which will supply the theoretical guidance for the film covering technology and prevent “White Pollution” of cotton field more effectively.

目前，新疆覆膜种植棉花面积超过150万公顷，总产量达到330万吨，覆膜播种给新疆棉花生产带来了很大经济效益。但是由于残膜不能及时全部回收，耕地遭到严重的残膜污染。残膜整膜回收效果不好的主要原因是由于起膜、残茬和残膜分离时导致残膜破损，破坏了残膜的完整性，回收难度增大，回收残膜中残茬较多，残膜利用率低。本项目针对研制成功的加强筋地膜和普通地膜整膜回收过程中起膜、分离进行研究分析，对残膜起膜、残膜和棉杆分离撕裂破损过程的力学特性进行分析，确定残膜起膜和分离撕裂破损的力学性能与几何特征的关系，建立残膜起膜和分离撕裂的力学模型；解决残膜和残茬分离问题，使回收残膜干净可利用；对残膜起膜和分离撕裂破损进行高速摄影观测和有限元仿真模拟，利用田间试验进行验证。并对各类残膜回收效率进行比较，提出适合新疆的最优覆膜方式和残膜回收技术，为新疆棉花作物覆膜技术提供理论指导，有效防治棉田“白色污染”。

目前，新疆覆膜种植棉花面积超过150万公顷，总产量达到330万吨，覆膜播种给新疆棉花生产带来了很大经济效益。但是由于残膜不能及时全部回收，耕地遭到严重的残膜污染。残膜整膜回收效果不好的主要原因是由于起膜、残茬和残膜分离时导致残膜破损，破坏了残膜的完整性，回收难度增大，回收残膜中残茬较多，残膜利用率低。本项目调研了新疆阿拉尔附近团场的耕层土壤残膜污染现状，针对目前常用的普通PE地膜、耐候PE地膜、和加强型PE地膜，开展膜下温湿度、力学性能、膜-土粘附力试验研究，分析膜下温湿度和新旧膜不同方向拉伸性能和直角撕裂强度的变化趋势，为确定地膜回收期的起膜方式和设计起膜装置提供理论依据。基于离散元法建立了残膜的虚拟模型，并对虚拟模型进行了虚拟拉伸、虚拟撕裂，模拟仿真了残膜的拉伸和撕裂机理。基于钉齿原理设计了第一代耕层残膜回收机设计，主要包括起膜钉齿、钉齿辊筒、毛刷脱膜辊，等，完成了第一代样机的研制和试验；为了解决第一代样机的缠膜率高问题，设计了第二代梳齿式耕层残膜回收机，主要包括梳齿、梳齿辊筒、带刷脱膜辊，等、并完成了第二代样机的研制和试验，试验结果表明回收率为74.8%，回收效率为0.07076ha/h。本文提出并验证了2种耕层残膜回收方式，为解决新疆棉田的“白色污染”问题提供了理论和技术支持。