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Minimizing Planter Fan Exhaust Velocity to Reduce Environmental Effects



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Vacuum fans are a critical component of planters used to draw seeds to a rotating perforated disc for precision sowing. As seeds adhere to the disc it is possible for the coatings to become dislodged, pass through the vacuum fan, and be exhausted into the surroundings. To minimize the possible environmental effects from the fan exhaust, the International Organization for Standardization (ISO) passed the ISO 17962 standard. It sets limits on the air velocity measured at a 2 m radius from the fan, and specifies that the exhaust from the fan must be directed groundward. In partnership with CNH Industrial, research was performed to assess the ability of the CNH Industrial vacuum fan to meet this standard. The research had two main goals: to determine if the vacuum fan could meet the standard, and to show that computational fluid dynamics (CFD) could be an effective tool for measuring compliance with the standard. The first part of the project was to experimentally determine the ability of the fan to meet the standard. This was accomplished by building and testing three fan configurations using the parameters specified in the ISO standard. The first configuration was inverting the fan to direct its exhaust groundward. The second was attaching a two-dimensional (2D) square diffuser to the fan, which reduced the exhaust velocity and redirected it to the ground. The third was attaching a manifold diffuser to the fan, which divided the exhaust into multiple slower exhaust jets, directed towards the ground. Results from all three configurations indicated exhaust velocities that were measured to be below the ISO standard thresholds (less than 2 m/s or 4 m/s, depending on measurement elevation, with the higher velocity limit imposed closer to the ground). The second part of the project was to create CFD simulations of the inverted fan and 2D square diffuser configurations, and compare them to the experimental results. The models were able to predict the locations and magnitudes of peak velocities around both configurations. This showed that CFD could be an effective tool for measuring standard compliance. Finally, the CFD models were used to compare the inverted fan to the 2D square diffuser, in terms of impact on the surroundings. It was found that by reducing the fan exhaust velocity, less air would become entrained by the exhaust jet, indicating a reduced likelihood of spreading fugitive seed coatings. Also, the slow exhaust jet would create less of a disturbance when impinging upon the ground.



Fluid Mechanics, CFD, Agricultural Machinery, Diffuser Design, Environment, Agriculture, Centrifugal Fan



Master of Science (M.Sc.)


Mechanical Engineering


Mechanical Engineering


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