طراحي، ساخت و ارزيابي دستگاه خردكن ذرت علوفه‌اي با محركه الكتريكي

Design, Construction and Evaluation of a Silage Corn Chopper Equipped with Electromotor Power Unit

در اغلب دامداری‌های سنتی كوچك و متوسط، خرد كردن ذرت علوفه‌ای به‌روش دستی انجام می‌گیرد. در این تحقیق به‌منظور رفع نیاز واحدهای كوچك دامپروری، دستگاه خردكن ذرت علوفه‌ای در مقیاس كوچك به‌وسیله نرم‌افزار Solid Works طراحی و ساخته شد. برای ارزیابی دستگاه، تأثیر سرعت دوران تیغه‌ خردكن (400، 550، 700 دور در دقیقه) و سرعت دوران غلتك‌های تغذیه (350، 400، 450 دور در دقیقه) بر عملكرد دستگاه خردكن شامل انرژی مصرفی مخصوص تیغه‌ خردكن، انرژی مصرفی مخصوص غلتك‌های تغذیه، طول ذرت خرد شده و ظرفیت دستگاه در قالب طرح كاملاً تصادفی و در سه تكرار با نرم‌افزار آماری SPSS مورد بررسی قرار گرفت. نتایج تحلیل تنش نشان داد كه در شرایط كاری تعیین شده (سرعت دورانی تیغه، عرض تیغه و میزان تغذیه) دستگاه می‌تواند به‌طور ایمن كار كند. با مطالعه مقدار نیروی برش ساقه ذرت، توان مورد نیاز دستگاه حدود 4 كیلووات و ظرفیت نظری آن 1/13 كیلوگرم در ثانیه محاسبه گردید. نتایج نشان داد كه در سطح احتمال یك درصد، تأثیر هر دو عامل و نیز اثر متقابل آن‌ها بر میزان انرژی مصرفی مخصوص تیغه‌ خردكن، طول ذرت خرد شده و ظرفیت دستگاه معنی‌دار است. ظرفیت دستگاه با افزایش سرعت تیغه خردكن از 400 به 550 دور در دقیقه افزایش یافت، اما در سرعت 700 دور در دقیقه، كاهش پیدا كرد. كمترین انرژی مصرفی مخصوص (1/26 مگاژول بر تُن) و بیشترین ظرفیت دستگاه (950 كیلوگرم بر ساعت) با توجه به طول مناسب ذرت خرد شده (20 تا 30 میلی‌متر) در سرعت تیغه‌ 550 دور در دقیقه و سرعت تغذیه 400 دور در دقیقه به‌دست آمد.

Introduction In most small and medium-size traditional animal farms, silage corn is chopped manually. In order to prepare appropriate chopper for small animal production firms, a small electrical powered chopper was designed and developed. Materials and Methods The machine consisted of different parts, including chassis, driveline, power transmission, feeding and cutting unit. To provide the power for cutting cylinder and feeding rollers, 3.7 kW and 1.5 kW electro-motors were selected and used, respectively. Power was transferred from electro-motors to the cutting cylinder and feeding rollers by pulley and belts. Feeding entrance area was 62.5 cm2with theoretical capacity of 1.13 kgs-1 and feeding unit power consumption of 0.97 kW. The main parts of feeding and cutting units were analyzed by ANSYS Software. Silage corn was provided at harvest time from the Dashte-Naz, Sari province, and transported to laboratory, immediately. The effect of cutting blades speed (400, 550 and 700 RPM) and feed rollers speed (350, 400 and 450 RPM) on the chopper performance (cutting and feeding energy consumption, chopped corn length and machine capacity) were investigated. The results then analyzed using completely randomized design in triplicates. Results and Discussion Analysis of variance showed that the speed of cutting blades, speed of feeding rollers and their interactions had significant effect on the energy consumption of cutting blades and machine capacity. The effect of speed of feeding rollers was significant on the energy consumption of feeding rollers at 1% level of significance. Also, The effect of speed of chopping blades, speed of feeding rollers and their interactions were significant on the length of chopped corn. Machine capacity increased by increasing in speed of chopping blades from 400 to 550 RPM and decreased by increasing from 550 to 700 RPM. Increasing in the speed of the blades at the moment of impact, caused to effectively cut the stem fibers before being compressed or bent. Increasing the speed beyond 550 RPM provided insufficient time for stem movement toward the blades and therefore, machine capacity decreased. By increasing the speed of feeding rollers, the consumed energy by cutting blades decreased and the energy consumption of feeding rollers, the length of chopped corn and the machine capacity increased. Since the machine capacity is depending on time, increasing in feeding rollers speed, decreased the time for chopping the feed stems resulted decreasing in machine capacity. Also, results depicted that the interaction between speed of cutting blades and feeding rollers had meaningful effect on the consumed energy by cutting blades. The maximum energy consumption was at the blade speed of 700 RPM and the feeding rollers speed of 350 RPM, and the minimum energy consumption was at the blade speed of 400 RPM and feeding rollers speed of 450 RPM. The maximum and minimum length of chopped corns was obtained at the blade speed of 400 RPM and 700 RPM, respectively and correspondingly at the rollers speed of 450 RPM and 350 RPM, respectively. The maximum capacity of the machine was obtained at the blade speed of 550 RPM and rollers speed of 450 RPM. Conclusions Since the length of the chopped corn for animal feeding is 20-30 mm, the optimum speed of cutting blades, minimum energy consumption and maximum machine capacity was obtained as 550 RPM and the optimum speed of feeding rollers was at 400 RPM. For feeding high yielding dairy cows, goats and sheeps that need smaller sized forage, it recommended that feeding rollers speed to be adjusted at 350 RPM. At the same speed, the mean length of chopped corn was 8-19 mm.