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Electrostatic Spraying with a Knapsack Sprayer

E. Moser
Professor
lnstitute for AgrartechnikUniversitat HohenheimGarbenstr. 9, 7000 Stuttgart 70, West Germany

Md. Daulat Hussain
Assistant Prof.
Dept. of Farm Power and MachineryBangladesh Agricultural UniversityMymensingh, Bangladesh

Abstract/ Executive Summary:

The possibility of installing the electrostatic charging methods of spray liquid with small sprayers has been investigated. The usability of these sprayers with different variable parameters has been studied. The influences of different charging methods, voltages and number of electrodes on the amount of electrodes were observed. The results obtained by using the electrostatic charging methods were compared with the results obtained by the conventional method of spraying. The distribution of de-position has been studied in three conditions: laboratory, field and green house. The original state of the sprayers were kept constant. The electrostatic charging unit was an additional input into the sprayers. Five sprayers were used in the experiment. Similar results with all the sprayers were obtained. The results obtained by using a knapsack sprayer with an air shear nozzle has been described.

Keywords: Knapsack Sprayer, Electrostatic spraying,

Location: Dept. of Farm Power and Machinery, Bangladesh Agricultural University Mymensingh, Bangladesh

Start Date:

End Date:

Program Area: Farm Mechanization

Commodity: Performance evaluation

Objectives:

To a great extent to solve problems of chemical plant protection.

Methodology:

There are three electrostatic charging methods which may be successfully applied for the production of charged droplets in plant protection machines (14, 15, 16, l7). In the contact charging system (1b), the high voltage is directly connected to the whole spraying system to the liquid, whereas with the corona charging system (la), the spray particles are charged in the corona, produced by the high voltage around sharp electrodes. In the case of the induction charging method (1c) the droplets are charged in an electric field. This system requires insulation between conductive liquid and electrode, which can be realized by an air stream of high velocity. Contact and influence charging, usually needs new and expensive constructions of spraying machines, corona charging systems can be mounted at conventional sprayers. In the case of the corona charging method, the number of electrodes may be 1 to 4 or more. For the safety of operation, the sprayers should be grounded during spraying and an insulation should be provided between the gap of the sprayer and the high voltage generator. A l2-volt battery or a l2-volt DC generator in hand or shoulder-carried sprayers may be used to supply the input voltage to the high voltage generator. For a wheel bar-row type sprayer, a l2-volt car battery may also be used. The functions and details of a knapsack sprayer's head using the corona charging method are shown. A two-stroke petrol engine (a) is used to run the radial blower (b). At maximum throttle, the engine rotates at 6200 rpm. Due to direct coupling, the rpm of the radial blower is identical to the rpm of the engine. The maximum air-velocity supplied by the sprayer at the spraying point is 30 m/s. This sprayer delivers air 598 m³/h. The amount of flow-rate through the nozzle can be controlled by manual adjustment (h). The output through the nozzle varies depending on the nozzle numbers. The pesticide tank (c) has a capacity of 12 litres. The total weight of the sprayer with full tank-pesticide is nearly 20 kg. With one filling, this sprayer can be used for about 30 minutes in the field. Spray-liquids from the tank to the nozzle can be controlled by means of a two-way-control valve(d). The high voltage generator (f) furnishes the high voltage (70 kV) to the charging electrodes (g) through the high voltage distributor (i). A 12 volt DC is supplied and directed to the high voltage generator (HVG). This can be furnished from a 12 volt battery O or from 8 x 1,5 volt dry cells or from a 12 volt DC generator. The electrical capacity of the high voltage circuit is very small and also there is very low current flowing in the circuit. As a result, the problem of the electrical hazards is automatically solved. It is possible, too, to charge the spray-liquid by using the contact charging method. The contact charging method, however, requires very good insulation. This is very costlyand more advanced technology is needed. Therefore, this method is normally not used for knapsack sprayer to charge sprays. The corona charging method, on the other hand, can easily be installed with this sprayer.

Source of Information: VOL.I6 NO.3 1985 AGRICULTURAL MECHANIZATION IN ASIA, AFRICA AND LATIN AMERICA

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It can be concluded that by using the electrostatic charging method, spray deposition and their distribution is much better than with conventional spraying methods. The small droplets can be effectively deposited on a desired target and simultaneously, the drift can be reduced to a great extent to solve problems of chemical plant protection. The electrostatic charging method can be successfully installed in small sprayers.

Knowledge Management: Journal