Numerical Simulation of Regulating Performance of Direct-Operated Pressure Regulator for a Microirrigation Lateral

International audienceA lateral inlet direct-operated pressure regulator is a novel device for microirrigation system that ensures the equal operating pressure of the lateral inlet required for high uniformity. This study develops a computational fluid dynamics (CFD) model in combination with inlet pressure and regulation assembly displacement to analyze the outlet pressure of the pressure regulator. The model is validated by a comparison of experimental measurements, and the predicted results show good agreement. The effects of the regulation assembly displacement and geometrical structure (regulation assembly inlet height) on regulating performance are investigated. Results show that the magnitude of the regulation assembly movement affecting by inlet pressure, preset pressure, and flow rate significantly changes in the beginning of the regulation range and then changes slowly. The spring parameters can be designed according to the force–displacement characteristic (the F–Lv curve) of the T-shape regulating plunger. A greater regulation assembly inlet height corresponds to a lower preset pressure and less sensitivity of pressure loss to the movement of the regulation assembly. The pressure distribution through the regulator provides an improved understanding of the pressure difference in the regulating plunger with various displacements. The CFD model can reflect the motion characteristics of the regulation assembly and reveal the key factor of the regulator design. The results form the sound basis for future design and performance optimization of pressure regulator

Perda de carga em microtubos e conectores utilizados em microaspersão Head loss in microtubes and connectors used in microsprinkler systems

Este trabalho foi desenvolvido com o objetivo de ajustar equações que estimam a perda distribuída de carga em microtubos utilizados em microaspersão e a perda localizada de carga na passagem lateral do fluxo por meio dos conectores na linha lateral. A perda distribuída de carga foi determinada em quatro diâmetros de microtubos com nove a dez repetições para 15 vazões, por meio da aplicação do teorema de Bernoulli. O fator de atrito (f) foi estimado fixando-se o valor de m = 0,25 e calibrando-se o valor do parâmetro c (0,290). A perda localizada de carga foi determinada por diferença entre perda de carga no microtubo mais conector e perda de carga no microtubo. Dois modelos de conectores foram utilizados e caracterizados quanto ao diâmetro interno e dimensões. Uma aproximação matemática foi proposta para calcular a perda localizada de carga com base em coeficiente de carga cinética do conector (K'), que leva em consideração as dimensões do conector e do microtubo e independência das forças viscosas para Re > 5.000. As variações de vazão e de pressão entre os emissores situados nos extremos da linha lateral mostraram-se sensíveis à perda de carga na passagem lateral pelo conector mais a perda de carga no microtubo.<br>This work was carried out aimed at presenting equations to estimate the continuous head loss in microtubes and the local head loss in the connector used on microsprinklers lateral lines. The continuous head loss was determined using Bernoulli's theorem for four microtubes diameters, each one with nine to ten replications for 15 flowrates. The Darcy-Weisbach friction factor was estimated by setting m to 0.25 and by calibrating the parameter value c to 0.290. The local head loss was determined by subtracting the head loss on the connector and microtube from the head loss on the microtube. Two types of connectors were used and characterized by its internal diameters and its dimensions. A mathematical approach to compute the local head loss was proposed based on a kinetic head connector coefficient (K'). This coefficient is a function of connector and microtube dimensions and independent of viscous forces up to Re > 5,000. Flowrate and pressure at emitters located at the far end of the lateral line were sensitive the head losses at the connectors and in the microtube