RESUMO:Este trabalho foi desenvolvido com o objetivo de determinar, em condições laboratoriais, o coeficiente de descarga (C d ) dos emissores fixos tipo "spray" (Senninger, Nelson e Fabrimar) utilizados em equipamentos pivô central no Brasil. Foram avaliados 45 bocais Senninger, 42 bocais Nelson e 36 bocais Fabrimar, com três repetições, totalizando 369 bocais ensaiados. As pressões de funcionamento variaram entre 6 e 30 PSI (41,37 a 206,84 kPa), com intervalo de leitura a cada 2 PSI (13,79 kPa), totalizando 13 pressões analisadas por bocal. Foram ajustadas as curvas do coeficiente de descarga em função do diâmetro de bocal, para quatro pressões de operação: 10; 15; 20 e 30 PSI (68,95; 103,42; 137,90 e 206,84 kPa). Utilizou-se de dois manômetros de precisão (analógico e digital) previamente calibrados em um manômetro de peso morto. As vazões foram obtidas utilizando três medidores eletromagnético-indutivos, calibrados em recipiente volumétrico. O diâmetro dos bocais foi mensurado através de uma ampliação em projetor de perfil da marca Starrett, modelo HB 400. Os resultados evidenciaram que o coeficiente de descarga varia em função da pressão e do diâmetro do bocal. Nos ensaios conduzidos, obtiveram-se C ds compreendidos na faixa de 0,88 a 0,98 para a faixa de emissores analisados. PALAVRAS-CHAVE:irrigação; hidráulica agrícola, pressão de funcionamento, aplicação de bocais. NOZZLE DISCHARGE COEFFICIENT FOR CENTER-PIVOT SYSTEMABSTRACT: This study aimed to determine the discharge coefficients (C d ) of sprinkler fixednozzles (Senninger, Nelson and Fabrimar), used in Brazilian center-pivot equipment, under laboratory conditions. These tests used the pressure range standard existing in the nozzle market (psi). A set of 45 Senninger, 42 Nelson and 36 Fabrimar nozzles were assessed, with three replications, in a total of 369 tested nozzles. Operating pressures ranged from 6 to 30 psi (41.37 to 206.84 kPa), with a reading gap of 2 psi (13.79 kPa), totaling 13 measures for nozzle. Discharge coefficient curves were drawn as function of nozzle size and operating pressures, which were 10, 15, 20, and 30 psi (68.95, 103.42, 137.90 and 206.84 kPa). Two precision pressure gauges (one analog and one digital) were used; being calibrated against a dead weight gauge. F low rates were obtained using three electromagnetic induction gauges calibrated with volumetric data. Nozzle diameters were measured using a profile projector Model HB 400 (Starrett, São Paulo, Brazil). The results evidenced that discharge coefficient varies with nozzle diameter and operating pressure. Tests showed C ds within the range of 0.88 to 0.98, for the assessed nozzles.
PORTABLE SAND FILTER FOR SMALL DRIP IRRIGATION SYSTEMS CLEOMAR FERREIRA DE OLIVEIRA1; MARCONI BATISTA TEIXEIRA2*; ADRIANA RAMOS3; RENATO MOREIRA DA SILVA4; PEDRO HENRIQUE PINTO RIBEIRO5 E JOSÉ ANTÔNIO FRIZZONE6 1 Engenheiro Agrônomo, Prof. Dr. IFMinas Gerais - Campus Muzambinho, MG.2 Engenheiro Agrônomo, Prof. Dr. IFGoiano - Campus Rio Verde, GO. *E-mail: marconibt@gmail.com3 Engenheira Agrônoma, Profa. Dra. Universidade Estadual de Santa Cruz – Ilhéus, BA.4 Engenheiro Agrônomo, Doutor, Departamento de Engenharia de Biossistemas, LEB - ESALQ/USP, Piracicaba - SP.5 Tecnólogo em Irrigação e Drenagem, Doutorando, Departamento de Engenharia Rural, UNESP/FCA, Botucatu, SP.6 Engenheiro Agrônomo, Prof. Titular, Departamento de Engenharia de Biossistemas, LEB - ESALQ/USP, Piracicaba - SP. 1 ABSTRACT Filters in drip irrigation systems are fundamental to ensure effective control of water quality and to reduce clogging of emitters. Current study aims at constructing a low cost portable sand filter for small localized irrigation systems (up to 1.0 ha) and at determining its head loss due to flow. Tests were carried out in the Hydraulic Laboratory of Biosystems Engineering Department of Agriculture School “Luiz de Queiroz”, University of São Paulo. Magnetic-induction Conaut Krohne model IFS 4000 w/6 with IFC 090 D signal convert of discharge, reading range between 0 and 90 m3.h-1 and 99% precision, was used for flow rate measurements. Pressure loss at each observation point was determined indirectly by two differential pressure gauges with a mercury column. A set of 20 flow readings was performed in three replications. Results showed that maximum filter discharge complied with ASAE guidelines and the cost of materials for manufacture of the filter was U$ 382.15. Linear mathematical model adequately describes the loss of pressure of the sand filter due to flow variation. Rates of minimum and maximum flow recommended range between 0.0257 m3.h-1 and 0.556 m3.h-1, and thus may satisfy small trickle irrigation projects. Keywords: Filtration, water quality, head loss, flow rate.
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