اثر زاویه حمله بر عملکرد یک تیغه باریک تغییریافته

خاک‌ورزی یکی از مهم‌ترین عملیات مزرعه‌ای است که به‌منظور بهبود ساختار و شرایط فیزیکی خاک و کمک به تهیه بستر مناسب رشد گیاه انجام می‌شود. خاک‌ورزی حفاظتی یکی از روش‌های خاک‌ورزی است که سبب کاهش هزینه‌های خاک‌ورزی می‌گردد. در خاک‌ورزی حفاظتی، تیغه مورد استفاده جهت انجام خاک‌ورزی، اهمیت بسیاری دارد. هدف از این پژوهش، تعیین زاویه حمله بهینه تیغه باریک تغییریافته در دو حالت بدون باله و باله‌دار، در خاک مزرعه می‌باشد. سه زاویه حمله تیغه (20 ، 25 و 30) درجه، دو سطح عمق خاک‌ورزی (15 و 20) سانتی‌متر و دو سطح سرعت پیشروی ( 2 و 3) کیلومتر بر ساعت تیمارهای این پژوهش بودند. پارامترهای اندازه‌گیری شده در این پژوهش؛ نیروی مقاومت کششی، مصرف سوخت تراکتور، لغزش چرخ محرک تراکتور، سطح مقطع به‌هم‌خورده خاک، سطح مقطع بالاآمده خاک و مقاومت ویژه خاک‌ورز بودند. آزمایش‌های مزرعه‌ای در طرح آماری کرت‌های دو بار خردشده بر پایه طرح بلوک کامل تصادفی و در سه تکرار انجام گردید. به‌منظور تعیین مقادیر بهینه تیمارهای ذکر شده، از روش رگرسیون چند متغیره خطی استفاده شد. مقادیر بهینه زاویه حمله تیغه، عمق خاک‌ورزی و سرعت پیشروی تراکتور، به‌ترتیب برای حالت تیغه بدون باله 20 درجه، 20 سانتی‌متر و 2.21 کیلومتر بر ساعت و برای حالت تیغه باله‌دار به‌ترتیب برابر 30 درجه، 20 سانتی‌متر و 2.03 کیلومتر بر ساعت به‌دست آمد.

Evaluation of the Effect of Rake Angle on the Performance of a Modified Narrow Blade

IntroductionTillage is one of the most important field operations to improve soil structure and physical conditions and provide the proper plant site. Conservation tillage is one of the methods of tillage that reduces tillage costs. The blade is one of the most important consumed components of tillage tools in the conservation tillage, which is very important for how it is adjusted and its effect on the quality of tillage and energy required of tillage tools. According to the research conducted on the importance of optimizing tillage implements, the aim of this study was oriented to determine the optimum rake angle of a narrowmodified winged and nonwinged blade in the field soil.Materials and MethodsThe tests were conducted in the 22nd part of farms in Agriculture School (Bajgah zone) of Shiraz University. Three levels of blade rake angles (20, 25, and 30 degrees), two levels of tillage depth (15 and 20 cm), and two levels of forward speed (2 and 3 km h1) were the treatments of this study. Draft, fuel consumption, slippage, soil disturbance area, soil upheaving area, and specific draft were the measured parameters and they were measured for each combination of the treatments. The RNAM test code was then used to measure the draft force. In order to measure fuel consumption, two flow meters were used in the round way as a closedloop. The encoder and the fifth wheel were also employed to measure the slippage. The profilometer and laser meter were applied to measure the soil upheaving and disturbance areas. The splitsplit plot on randomized complete block design was used to do the field experiments in three replication and the data analysis was performed by SAS software (9.4 edition). Multivariate linear regression was used to determine the optimum values of the mentioned parameters. For this purpose, the lowest value of draft, fuel consumption, specific draft, tractor driver wheel slip, and the highest soil disturbance and upheaving areas was considered.Result and DiscusionThe results showed that the magnitude of draft increased with rake angle, therefore, the minimum draft was obtained in the rake angle of 20°. As the blade rake angle increased, the amount of soil disturbance area was increased and the maximum soil disturbance was obtained in the rake angle of 30°. The mean slip values of the tractor driver wheels when using nonwinged blade were not significant for three levels of blade rake angles and it was significant for two velocity levels. With increasing in rake angle from 20 to 25°, the mean values of specific draft were increased, but with changeing the rake angle from 25 to 30°, there was not significant difference between specific draft values. The difference between the magnitude of tractor driver wheels slip for three levels of rake angle was not significant. Increasing the rake angle had a significant effect on tractor fuel consomption, such that it increased by increasing the rake angle values.ConclusionsThe optimum rake angle for the nonwinged blade mode was 20° with R2 of 0.73 and for the winged blade mode was 30° with R2 of 0.90. The optimum depth for the nonwinged blade was 19.98 cm with R2 of 0.99 and for the winged blade was 20 cm with R2 of 0.97. Also, the optimum forward speed values for the nonwinged blade was 2.21 km h1 with R2 of 0.43 and for the winged blade was 2.03 km h1 with R2 of 0.84.