نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه مهندسی بیوسیستم، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران
2 گروه مهندسی مکانیک، دانشکده مهندسی، دانشگاه فردوسی مشهد، خراسان رضوی، ایران.
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
A cylindrical sieve, characterized by its simple structure, lightweight, negligible vibration, and lower energy consumption compared to other separation systems used in combines. This type of screen can serve as an alternative cleaning system for rice-threshed mixture when combined with air flow. This research employed computational fluid dynamics (CFD) and the discrete element method (DEM) to explore and enhance the understanding of the operational parameters influencing the performance of the cleaning sieve. The study examined the impact of air flow velocity and the rotational speed of the sieve on various separation indices, such as the cleanliness ratio, loss ratio, and efficiency. Findings indicated that air flow velocity significantly influences the average axial speed of the mixture components. The rotational speed of the sieve has a significant effect on both the loss ratio and the sieve's efficiency. In this study, Rocky DEM software was utilized as an alternative to EDEM for simulating the discrete flow of granular materials. The results of this study were validated through comparisons with earlier research that utilized EDEM software for simulations. Rocky DEM software developed by the provider of ANSYS Fluent, Rocky DEM enables the simulation of interactions between discrete particles and fluid flow using the coupled CFD-DEM method. Consequently, it serves as a viable replacement for EDEM, which has been extensively applied in agricultural research and engineering.
کلیدواژه‌ها [English]
The rotary cylindrical sieve is distinguished by its simple design, low weight, negligible vibration, user-friendly operation, and higher energy efficiency when compared to other separation systems. When combined with airflow, it functions as a supplementary cleaning method for threshed rice. A limited amount of research has been carried out on particle theory and the factors affecting separation in rotary cylindrical sieves. Previous research has primarily centered on experimental approaches or mathematical models, treating the mass of biological entities as separate entities, with each entity interacting with its surrounding counterparts.
This research utilized a combination of coupled computational fluid dynamics (CFD) and discrete element method (DEM) to gain a deeper understanding of the operational parameters affecting the sieve's capacity to distinguish grains from non-grain materials. The density of air, approximately 1.29 kg/m³ at standard atmospheric pressure, is notably lower than that of each component in the harvested rice mixture, which spans a range of 300 to 1300 kg/m³, thereby requiring the application of one-way CFD-DEM coupling. The material flow was simulated using the Rocky DEM software, known for its sophisticated particle modelling abilities, whereas the airflow was modelled with ANSYS Fluent software, which is valued for its reliable computational fluid dynamics platform. This combined strategy demands additional computational time, yet it offers a detailed representation of interactions between particles, as well as between gas and solid phases, and between solid and gas phases, all of which are crucial for conducting a precise analysis of separation performance.
Given the size of the threshed rice components, the dimensions of the sieve were carefully chosen to optimize separation efficiency: hole diameter of 10 mm, length of 700 mm, and diameter of 300 mm. A 3D model of rice grains and straw was created using Rocky DEM software, incorporating additional parameters recommended by the software to enhance the simulation accuracy. Upon conducting the simulations, it was observed that certain grains move toward the sieve surface, and upon contact, they pass through the holes and existed the sieve. Most of the straw and empty grains were expelled from the end of the sieve because of their low density and the influence of airflow.
The study investigated how the airflow velocity and rotational speed of the sieve affected the movement rules and screening characteristics, such as the cleanliness ratio, loss ratio, and efficiency of the components of the rice-threshed mixture (grains, shriveled grains, and stalks). The results indicate that the airflow velocity significantly influences the average axial speed of the mixture components and consequently affects the cleanliness, loss ratio, and screening efficiency. Conversely, although the rotational speed of the sieve does not affect the cleanliness ratio, it does have a notable impact on both the loss ratio and the sieve efficiency.
The results of this study were validated by comparing them with those of previous studies that used EDEM software for simulations and experimental assessments. The Rocky DEM software is a convenient alternative to EDEM software for simulating discrete material flows because of its compatibility with ANSYS Fluent software during the coupling process.
Conceptualization, M.J. and M.N.; methodology, K.S.H.; software, K.S.H. and M.N.; validation, K.S.H., M.J. and M.N.; formal analysis, K.S.H., M.J. and M.N; investigation, M.J.; resources, M.J.; data curation, K.S.H.; writing—original draft preparation, K.S.H., Y.T.; writing—review and editing, K.S.H., M.J. and Y.T.; visualization, K.S.H.; supervision, M.J.; project administration, M.J. and M.N.; funding acquisition, M.J. All authors have read and agreed to the published version of the manuscript.
Data available on request from the authors.
The authors gratefully acknowledge the financial support from IUT (Isfahan University of Technology, Isfahan, Iran).
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
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