Numerical and experimental investigations on internal flow characteristic in the impact sprinkler
Haijun Yan, Yangjun Ou,
Kazuhiro Nakano and Chengbo Xu
Summary
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.