Analysis of flow in a multi-blade fan is required for improvement of efficiency and for noise reduction. This paper describes experimental investigation of flow in a multi-blade fan by qualitative and quantitative visualization. Intake flows of the fan are qualitatively visualized by means of laser-light-sheet technique and velocity distributions in the scroll of the fan are measured by processing of images obtained by dual-beam-sweep illumination technique. The results obtained show that the intake flow pattern changes with flow rate and the velocity in the scroll at large angle is larger than it at trailing edge of the blades.
