Structural optimization and performance analysis of button pressure-compensating emitters

Abstract: A Pressure-Compensating emitter (PC) has been characterized by the constant flow rate at the varying inlet pressures in agricultural water-saving irrigation under complex conditions, such as long-distance pipelines and undulating terrain. However, the PC emitters still depend mainly on imports or appearance imitation in the domestic market. It is also lacking in the reasonable design theory of PC products in practice. At the same time, there can be a great challenge for the long-term development of the water industry in China. In this study, a kind of button PC emitter was developed with a configuration of the elastic sphere as the compensating element and spiral tunnel, particularly for better performance, simple production procedure, high assembly accuracy, and cost saving in the heavy equipment. The silicone rubber was preliminarily selected as the material of the compensating element, and polypropylene was as the body of the PC emitter. A bi-directional fluid-structure coupling simulation was firstly performed on the COMSOL Multiphysics platform. Four configurations were carried out to determine the optimal combination of spherical limit surface and space spiral pair flow channel. A single-factor experiment was then conducted on the key parameters of the channel and compensating element. As such, the best interval was optimized and verified the simulation using three factors and three levels of orthogonal experiment. Furthermore, a quadratic polynomial regression model was established by Design-Expert 8.0.6 software. Therefore, the influencing factors to the flow state index were ranked in descending order of the hardness of compensating element, the widths, and the depths of the channel. Simultaneously, a Box-Behnken response surface analysis was used for the interaction between various factors. The results showed that there was a strong correlation between the channel depths and compensating element hardness, while the channel widths and compensating element hardness. But there was no interaction between the width and depth of the channel. The optimal combination of factors was finally selected as: the depth of 0.14 mm, the width of 0.65 mm, and the PC component hardness of 53 HA. The verification test showed that the compensation interval was 0.075-0.30 MPa, the flow index was 0.067, and the average flow rate in the compensation interval was 2.32 L/h. The improved manufacturing process greatly reduced the production cost, compared with the commonly-used PC emitters. Consequently, the bi-directional fluid-structure coupling modelling with Box-Behnken response surface analysis can be expected to shorten the development cycle in the PC emitters. An anti-clogging performance can be further explored for the specific mechanism and configuration of self-developed PC emitters in the future. A better substitute for the improved PC emitters can be served as the traditional emitter. The finding can also provide valuable information for the PC emitters on the configuration and strategy during water-saving irrigation in precise agriculture.