ارزیابی یک نوع چرخ‌فلک ماشین برداشت نخود با صفحه مشبک در دماغه

یکی از بزرگ‌ترین مشکلاتی که در کشت بقولاتی مانند نخود وجود دارد، برداشت این محصولات با ریزش بسیار زیاد است. هدف از اجرای این پژوهش، برداشت مکانیزه نخود با تلفات کم و عملکرد مزرعه‌ای مناسب است. طراحی این ماشین به گونه‌ای است که همانند کمباین‌های متداول برداشت غلات قابلیت تنظیم موقعیت چرخ فلک نسبت به دماغه و تغییر ارتفاع را دارد. همچنین برای کاهش ریزش دانه ناشی از بازگشت محصول برداشت شده صفحه مشبکی به زیر چرخ‌فلک اضافه شد. در این تحقیق چرخ‌فلک برداشت نخود با هدف کاهش تلفات دانه مورد ارزیابی قرار گرفته و مدل‌سازی، تحلیل دینامیکی و استاتیکی چرخ‌فلک ماشین‌برداشت نخود انجام گرفته است. سامانه باز طراحی شده با تغییر عوامل تاثیرگذار شامل دماغه با صفحه مشبک و بدون صفحه مشبک، ارتفاع شانه برش نسبت به زمین در سه سطح 10، 15 و 20 سانتی‌متر و فاصله چرخ‌فلک از شانه در سه سطح 3، 5 و 7 میلی‌متر در سه تکرار مورد ارزیابی قرار گرفت. تحلیل آزمایش‌ها در قالب طرح کاملاً تصادفی انجام شد. نتایج آماری نشان داد، استفاده از صفحه مشبک تاثیر معنی‌داری در سطح یک درصد بر مقدار برداشت و ریزش داشته است اما در مورد نخود باقی‌مانده بر روی بوته این اثر در سطح 5 درصد معنی‌دار شد. تاثیر ارتفاع دماغه از سطح زمین بر میزان برداشت در سطح 5 درصد معنی‌دار بود. همچنین اثر متقابل ارتفاع برداشت و صفحه مشبک نیز بر میزان ریزش در سطح 5 درصد معنی‌دار شد. بیشترین تاثیرگذاری بر نخود باقی‌مانده بر روی بوته در اثر فاصله بین چرخ‌فلک و دماغه به‌وجود آمد. علاوه بر آن برای بهینه‌سازی ابعادی اجزای چرخ و فلک از روش اجزای محدود سه بعدی با تحلیل تغییر شکل و شکست با معیار ون میسز (von-mises) استفاده شد. به کمک مدل‌سازی رایانه‌ای و با توجه به تجزیه و تحلیل دینامیکی مدل جدید‌ی از چرخ‌فلک برای ماشین برداشت با هدف کاهش وزن، ارائه شد. در طرح ارائه شده با توجه به نیروی متقابل بین محصول و چرخ‌فلک ماشین برداشت نخود، میزان قابل‌توجهی از وزن چرخ‌فلک کاسته شد.

evaluation of a chickpea harvesting header with perforated plate

introductionone of the biggest problems in growing legumes like peas is harvesting these types of crops. during the machine harvesting process the harvest loss is very high. therefore, in most parts of iran chickpea harvested by hand and this is very tedious. based on the literature review there are different types of harvesting machines which designed, constructed and optimized by miller et al., 1990; golpira, 2015; shahbazi, 2011; jalali and abdi, 2014; mahamodi, 2016. but using different varieties of chickpea in mountainous areas has limited the use of harvesting mechanisms. the purpose of this study is mechanization of the harvesting process of chickpea with low losses and suitable performance. moreover the optimization process of lowering the weight of the header was carried out by modeling of software.materials and methodsto reduce the amount of chickpea losses from the reel, a perforated plate with defined holes was installed in the header, where the separated chickpea pods fell behind the plate without returning to the farm. by using the plate in the header of the chickpea harvesting machine and by changing the harvesting height at the three levels of 10, 15 and 20 cm and the distance of the cutter at three levels of 3, 5 and 7 mm, the performance of the machine was evaluated. the experiments were carried out with caboli variety cultivated in kurdistan province, which is proper for mountainous areas without regular watering condition in three replications. the plants were placed in a fiber, wooden plate considering farm conditions. in addition, the header was modeled statically and dynamically under the influence of the external forces applied to the header using ansys and abaqus software. based on the actual data, the validity of the applied model was determined and according to the verification results the optimization of the header was performed considering minimal weight (to reduce energy consumption).results and discussionthe evaluation results of the performance of header showed that the effects of using perforated plate and the height of the header for harvesting on the chickpea harvesting and losses are significant at the level of 1% and 5%, respectively, and the interaction between perforated plate and the header height on the chickpea loss is significant at 5%. using a perforated plate in the harvesting machine increases the amounts of chickpea collected from the farm increases. in this condition the chickpea pods separated from the plant and passed through the plate. with the separation of the stems, due to the proper wear that exists between the plate and the reel, the pods are properly separated and pass through the perforated plate. moreover, the chickpea loss is higher for the system without perforated plate. the effect of the distance between the reel and header plate is affects the remaining chickpea on the plate. by increasing the distance from 5 mm to 7 mm the amount of harvested had a considerable effect. the best method of harvesting chickpeas is at the kinematic index of 1.5 with perforated plate, the harvesting height of 15 cm and the distance of 5 mm. according to modeling processes of the reel and the results of the static analysis, the minimum and maximum stress values were recorded about 3.31 mpa and 6.50 mpa (based on the von misses criteria), respectively, which is very small compared to the yield stress of the reel constructed with st-37. also, the results of the dynamic analysis of the reel showed that the maximum von misses stress occurred with increasing the kinematic index. the maximum stress for kinematic index of 1, 1.5 and 2 was observed about 32.2, 40.1 and 52.72 mpa, respectively. the results of 3d model validation showed that the applied model with abaqus software (r2>0.9264) was able to predict the amount of stress in different parts of the reel.conclusionin this study, the changes were made on the chickpea harvesting machine to get the proper performance and increasing machine efficiency. a perforated plate was used to prevent pea’s losses. the best condition for the harvesting process is obtained with the harvesting height of 15 cm and the distance of 5 mm. by using 3d modeling of the reel weight was reduced about 10%.