Abstract: The air field distribution and spray efficiency are influenced by the internal structure of an air-assisted sprayer. In this paper, computational simulation was applied to analyze effects of the distributor number on the internal wind flow field in an air duct. Effects of cylindrical, conical and semi-elliptical fluid director structures on the duct wind flow field outlet speed and pressure loss were simulated. The form and structure of fluid director were optimized to obtain high efficiency. A prototype machine was made and comparative analysis was conducted with the measured duct performance before and after oriented object installation. Results indicated that the proper amount of deflector was from four to five pieces. After fluid director was installed, power saving reached to 4.88% when the fan speed was at 2926.5r/min. The installed deflectors were benefit for turning the rotating air flow to the axial air flow within the duct and generated pressure loss. The oriented object’s structure had great effects on the duct pressure loss rate and outlet wind speed. A minimum pressure loss rate was obtained by using the semi-elliptical oriented object.