Optimising the hydraulic performance of a jet impingement sprinkler by varying elevation angle: A Comparative study with a non-impingement sprinkler

Abstract

A novel jet impingement sprinkler was designed to replace the additional water-dispersing devices usually used in rotating sprinklers to adapt performance for low-pressure conditions. Utilising the asymmetric impingement mode of primary and secondary jets, the design prioritises the secondary nozzle elevation angle. Theoretical expressions were establish between the primary and secondary jet momentum rates. Hydraulic performance experiments, were conducted under intermediate and low-pressure conditions, examining water application rate, wetted radius, and Christiansen's uniformity coefficient at various elevation angles. High-speed photography (HSP) experiments elucidate differences in hydraulic performance, revealing that the impingement jet generally featured a lower maximum water application rate but a smoother distribution compared to its non-impingement counterpart. Using the CRiteria Importance Through Intercriteria Correlation (CRITIC) method, comprehensive scores highlight an optimal arrangement with a 34.5° secondary nozzle elevation angle, illustrating superior performance under low pressure. Comparative analyses between the wetted radius and Christiansen's uniformity coefficient uncover a trade-off, with jet impingement sacrificing wetted radius for increased uniformity. However, this efficiency diminished as jet impingement effects intensify. HSP experiments validate theoretical calculations, with a relative error of less than 4% for jet deflection angle and jet breakup length. Non-linear curve fitting establishes relationships between jet breakup length, mean observed jet deflection angle, operating pressure, and wetted radius. Calculated and measured values exhibited a relative error within 5%, affirming the applicability of the developed equation for predicting wetted radius in jet impingement sprinklers.