0.928。An experiment was carried out to investigate hydraulic performance in internal flow passage of a PY-140 impact sprinkler with different bullet-shaped straighteners and nozzles. The results showed that total friction loss in internal flow passage was in direct ration to nozzle diameter, length of straightener and inlet pressure. A regression model describing their relations was established. The ratio of friction loss in sprinkler tube to total friction loss was averaged as 0.666. The paper indicated that as inlet pressure was kept constant, nozzle pressure was in inverse proportion to nozzle diameter and length of straightener, and the maximum relative error of flow rate was 4.7%. Finally, the paper recommended that the average discharge coefficient for a conical nozzle angle of 40° was 0.928.