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Design, development and evaluation of air assisted boom sprayer for orchard application

This study was aimed to develop an air assisted orchard boom sprayer for effective deposition of pesticides inside the tree canopy. In order to predict airflow characteristics and to determine parameters of a suitable air duct, similitude studies were first conducted in the laboratory. Based on the parameters of air ducts, determined in similitude, studies an experimental air assisted sprayer was developed. The sprayer was tested on an artificial canopy under controlled conditions. A prototype of the field sprayer was fabricated and tested on citrus orchard with the optimum levels of machine and operating parameters. The results of the study are based on the results of the study, following conclusions could be drawn. The velocity was successfully predicted by linear regression on dimensionless numbers. The coefficient of determination was 0.85 for middle orifice and 0.82 for extreme orifice. Designed values of duct diameter and orifice diameter were 30 cm and 5 cm, respectively.

A threshold air velocity at the canopy surface was required to penetrate the canopy. Higher volume of air with velocity at threshold level gave good penetration. For air velocity of 15 m/s at the canopy surface, a maximum velocity of 2.1 m/s was achieved at the centre of canopy with air duct having 25 number of orifice. A linear relation was found between decay coefficient and leaf area density.

Higher the leaf area density, lower was the droplet density at all level of variable. Higher volume with threshold velocity was advantageous in penetration and deposition of spray. Higher the leaf area density, lower was VMD and the ratio VMD and SMD, at the center of canopy. It could be concluded that smaller droplets were advantageous in penetration in dense foliate. Nozzle produces droplets of various sizes. The number of nozzles increased droplet density at different locations inside the artificial canopy, however, at 7 number of nozzles, liquid started to run off from the target due to high discharge rates. Droplet density along the centerline of canopy did not change appreciably with increase in nozzle pressure. Higher number of nozzles increase the droplets in air stream. However, the VMD at the center increased with increase in number of nozzles. Higher the nozzle pressure, lower was the droplet size. Therefore, less energy was required to transport the spray. More uniform deposition was achieved at higher nozzle pressure.

From the similitude studies air duct parameters, namely diameter of duct, diameter of orifice and length of air duct were designed and they were 30 cm, 5 cm and 330 cm. Based on the test results obtained with experimental sprayer, the air velocity of 15 m/s at canopy surface was found to give best performance. The five number of nozzles with 550 kPa resulted better performance and hence it was recommended for prototype air assisted boom sprayer.


Agriculture Sprayers and Dusters by ASPEE Group Of Companies, India. www.aspee.com

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This article is written by Shri. Vinod Kumar Bhargav of Indian Agricultural Research Institute, New Delhi on behalf of ASPEE Agriculture Research and Development Foundation. ASPEE Group of Companies is the leading manufacturer and exporter of Agriculture Sprayers and Dusters


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