Landwards Summer 2022
Biosystems Engineering
Biosystems Engineering, owned by the IAgrE, and the official scientific journal of EurAgEng, is published monthly with occasional special issues.
Biosystems Engineering Volume 214, February 2022, Pages 165-176 Airflow temperature and humidity patterns in a screenhouse with a flat insect-proof screen roof and impermeable sloping walls – Computational fluid dynamics (CFD) results Meir Teitel, Shay Ozer, Vered Mendelovich Institute of Agricultural Engineering, The Volcani Center, Israel Insect-proof screenhouses are commonly used to grow plants in warm climates. However, there is relatively little literature on their microclimate compared to greenhouses. This study presents computational fluid dynamics (CFD) results of airflow, temperature, and humidity ratio patterns in a screenhouse with a roof consisting of a large flat insect-proof screen and impermeable walls. First, vertical profiles of velocity, temperature, and humidity at the centre of the screenhouse were obtained by 2D steady-state CFD simulations and validated by experimental results. The main deviation of the CFD results from the experimental results was observed with the air velocity in the upper region of the screenhouse. Inflow and outflow in the leeward and windward parts of the flat roof were observed, respectively. This resulted in large-scale airflow within the screenhouse opposite the outside wind direction at the canopy level. The results suggested that the leeward section of the screenhouse is warmer than the windward one and has a lower humidity ratio. Large-scale rotating airflow formed in the centre of the screenhouse, close to the roof, a large area with a humidity ratio similar to ambient conditions.
Biosystems Engineering Volume 215, March 2022, Pages 143-155 Intelligent ballast control system with active load-transfer for electric tractors Shengli Zhang, Bin Xie, Changkai Wen, Yirong Zhao, Yuefeng Du, Zhongxiang Zhu, Zhenghe Song College of Engineering, China Agricultural University, Beijing, China Beijing Key Laboratory of Optimised Design for Modern Agricultural Equipment, Beijing, China State Key Laboratory of Power System of Tractor, Luoyang, China For agricultural tractors fixed ballast cannot provide high-efficiency traction under time-varying resistance in the field. Combining the characteristics of electric tractors with high-weight battery packs, this paper develops an intelligent
ballast control system including a battery position adjustment (BPA) mechanism and an active ballasting control method. A tractor traction performance prediction model was developed to predict traction performance parameters and load-transfer in real time. The movement of the battery pack enables load-transfer based on the BPA. To ensure the lowest sliding rate of optimal tractive efficiency, an active ballasting control method based on a particle swarm optimisation algorithm was proposed that enabled control of the optimal battery position. The results of a hardware in the loop test showed that the average tractive efficiency in the mode of active ballasting mode higher than that of the no ballasting mode (> 6.6%) and fixed ballasting mode. Mean wheel slip in active ballasting mode was lower than that of the no ballasting mode and the fixed ballasting mode. This study provides theoretical support and technical reference for optimising the traction performance of electric tractors.
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