Numerical and experimental investigations on internal flow characteristic in the impact sprinkler

Abstract

An integral 3D numerical model based on the structural characteristics of the impact sprinkler was constructed to simulate the relationship between flow rates and inlet pressures as well as the flow field distribution by computational fluid dynamics (CFD). A commonly used PY140 sprinkler in China with three different flow straighteners in lengths of 80, 140 mm and 200 mm respectively and without flow straightener was investigated under inlet pressures ranging from 300 kPa to 500 kPa numerically and experimentally. The simulation results obtained revealed that the predicted relationship of flow rates and inlet pressures was in good agreement with the measurements. Fixing a proper flow straightener can effectively improve the turbulent flow state inside the sprinkler and lead to a more uniform velocity at the nozzle outlet. The sprinkler with a flow straightener resulted in a larger pressure loss within the internal flow than the sprinkler without flow straightener. A longer flow straightener caused a smaller turbulent kinetic energy at the nozzle outlet, which indicated that the length of flow straightener had no significant effect on the flow rate. As well, it was found that reversed flow happened near the nozzle outlet with a diffused angle of 90° could be observed clearly. The decrease of the diffused angle from 90° to 60° can supply a larger flow rate, which was verified by an experiment.