Estudo de um sistema de eletrificação de gotas em pulverizador costal pneumático pelo método de gaiola de Faraday

Abstract

Estudo de um sistema de eletrificação de gotas em pulverizador costal pneumático pelo método de gaiola de Faraday 1 A aplicação inadequada de agrotóxicos pode causar sérios problemas ao ambiente e o emprego de gotas com pequeno diâmetro pode favorecer a cobertura dos alvos, porém desde que ela aconteça em condições especiais para minimizar a deriva. Objetivou-se, com este trabalho, analisar os fatores que influenciam a relação carga/massa (Q/M) gerada por um sistema de eletrificação de gotas em um pulverizador pneumático costal com kit eletrostático por meio de uma gaiola de Faraday. Montaram-se dois experimentos, o primeiro em delineamento inteiramente casualizado, a fim de verificar a influência da distância entre o pulverizador e o alvo, a vazão de aplicação e a calda de pulverização, no funcionamento do sistema de eletrificação de gotas. Neste experimento, avaliaram-se quatro distâncias (0; 0,5; 1,0 e 2,0 m) entre o pulverizador e a gaiola. No segundo experimento, em esquema fatorial, analisaram-se cinco composições de caldas e cinco vazões (0,25; 0,76; 1,00; 1,45; e 1,58 L min -1 ). A relação Q/M foi determinada por meio da medição da corrente elétrica a partir do volume de calda pulverizado em gaiola de Faraday com um multímetro, dividida pela respectiva massa de líquido. Analisou-se, também, o espectro de gotas produzidas pelo pulverizador, em analisador de partículas por difração de raio laser. Verificou-se que, com o aumento da vazão de pulverização na gaiola de Faraday, menor foi a relação Q/M, o que também ocorreu com a distância do bocal do pulverizador eletrostático da entrada da gaiola. Em relação à calda de pulverização, a relação Q/M aumentou com a adição de óleo mineral, do óleo vegetal e de inseticida. Concluiu-se que a distância entre o bocal do pulverizador e o alvo, a vazão e a calda de aplicação influenciam na eficiência da pulverização eletrostática. Palavras Study of a droplet electrification system in a backpack sprayer in a Faraday cageThis study evaluated the factors affecting the charge/mass ratio (Q/M) generated by a droplet electrification system in a backpack sprayer with an electrostatic kit, using a Faraday cage. Two experiments were conducted in completely randomized design to determine the effect of application rate, the distance between the nozzle and the target, and spraying mixtures on performance of the droplet electrification system. The first study evaluated four distances (0, 0.5, 1.0, and 2.0 m) between the nozzle and the Faraday cage; the second study was conducted in a factorial design, with five tank mixtures and five flow rates (0.25, 0.76, 1.00, 1.45, and 1.58 L min -1 ). The Q/M ratio was determined using a multimeter by measuring the electric current from the volume of mixture sprayed in the Faraday cage, which was divided by the respective liquid mass. Droplet spectrum was analyzed by a particle analyzer using laser diffraction. The Q/M ratio became smaller as the spraying flow rate increased, similarly as observed with increasing distances of the electros...

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