Optimization and experiment of adjustable structural parameters for vertical impact sprinkler with working pressure

Abstract: The adjustable structural parameters of sprinkler were optimized in order to get the optimal hydraulic performance of vertical impact sprinkler. The variation coefficient of sprinkler irrigation, average application rate of sprinkler irrigation, uniformity coefficient under square arrangement and uniformity coefficient under regular triangle arrangement were taken as response indices to analyze the influence of distance between counterweight and rotational center, working pressure and nozzle diameter on hydraulic performance. The experimental study on the adjustable parameters of vertical impact sprinkler with working pressure was performed with the central composite design and the response surface methodology. The multiple regression models between the different response indices and working parameters were established. The analysis of variance was used to analyze the influence of the factors and their interactions on different indices according to the analytical results. The multiple regression models were used to optimize the indices by single-objective optimization and multi-objective optimization. Finally, the effectiveness was validated through an experiment. The results showed that: the significance order of impact factors for variation coefficient of sprinkler irrigation was working pressure, nozzle diameter, and distance between counterweight and rotational center; that for average application rate of sprinkler irrigation was nozzle diameter, distance between counterweight and rotational center, and working pressure; that for uniformity coefficient under square arrangement was working pressure, distance between counterweight and rotational center, and nozzle diameter; that for uniformity coefficient under regular triangle arrangement was working pressure, distance between counterweight and rotational center, and nozzle diameter. R2 value of multiple regression models for variation coefficient of sprinkler irrigation, average application rate of sprinkler irrigation, uniformity coefficient under square arrangement and uniformity coefficient under regular triangle arrangement were 0.9576, 0.9696, 0.9559 and 0.9546 respectively. Under the condition of single-objective optimization, the optimal parameter combination for the minimum variation coefficient of sprinkler irrigation was figured out as follows: the distance between counterweight and rotational center was 126 mm, the working pressure was 600 kPa, and the nozzle diameter was 16.6 mm; the optimal parameter combination for the minimum average application rate of sprinkler irrigation was that the distance between counterweight and rotational center was 115 mm, the working pressure was 219 kPa, and the nozzle diameter was 12.5 mm; the optimal parameter combination for the maximum uniformity coefficient under square arrangement was that the distance between counterweight and rotational center was 143 mm, the working pressure was 585 kPa, and the nozzle diameter was 23.7 mm; the optimal parameter combination for the maximum uniformity coefficient under regular triangle arrangement was that the distance between counterweight and rotational center was 115 mm, the working pressure was 219 kPa, and the nozzle diameter was 12.5 mm. Under the condition of multi-objective optimization, the optimal parameter combination for the minimum variation coefficient of sprinkler irrigation and average application rate of sprinkler irrigation, the maximum uniformity coefficient under square arrangement and uniformity coefficient under regular triangle arrangement was that the distance between counterweight and rotational center was 146 mm, the working pressure was 583 kPa, and the nozzle diameter was 23.4 mm; and its corresponding variation coefficient of sprinkler irrigation, average application rate of sprinkler irrigation, uniformity coefficient under square arrangement and uniformity coefficient under regular triangle arrangement were 0.27, 6.37 mm/h, 87.60% and 87.93%, respectively. The optimization results were validated, and the error between predicted values and experimental values was less than 5%, which indicated the predicting regression models had high credibility. The study provides the reference for designing the vertical impact sprinkler and properly regulating the working parameters to get the optimal hydraulic performance.