Completed the 3D PDA measurement of the apex flow field of the axial fan impeller

According to the experimental data, the blade tip flow was 94%, 96%, 98%, and 101% at the blade height. The experimental conditions are: the speed is 1800r/min, and the efficiency is at the highest efficiency point of the fan. At 94% of the blade height, the flow inside the blade runner is very stable, and the outlet flow is smooth and undisturbed, completely in the mainstream zone. At 96% of the blade height, the flow inside the blade runner begins to be slightly disturbed, and the outlet flow field also produces a slight disturbance. The flow field is basically the mainstream flow zone, and there is no obvious turbulent zone. At the blade height of 98%, the flow disturbance inside the blade flow channel is already obvious. The vortex starts to appear, and the outlet flow field is disordered. The flow field begins to be divided into the main flow zone and the turbulent flow zone, and there is a countercurrent vortex, and the turbulent flow zone appears. Mainly concentrated after the 50% chord length of the blade. At 101% relative to the blade height (ie, at the top of the blade), the internal disturbance of the blade runner is further aggravated, the disturbance of the outlet flow field is strengthened, the zone flow in the mainstream zone and the turbulent zone is more obvious, and the countercurrent vortex is further enlarged, turbulent The zone begins at 30% of the chord length of the blade.

Overall, the flow of more than 98% of the blade leaf height is more complicated than the flow of less than 98% of the blade leaf height. At the gap at the top of the blade, the flow is further complicated by the effects of leakage and countercurrent vortices. The experimentally measured flow field data is in good agreement with the flow field distribution obtained by the numerical calculation software. Through experimental research, several key problems affecting the accuracy and efficiency of PDA measurement in the experiment are solved, namely the choice of the form of measurement window, the selection of scattering particles, the selection of scattering particle addition mode, the overcoming of measurement blind zone, and the flow noise. Processing. The 3D PDA measurement of the apex flow field of the axial fan impeller was completed well, and the 3D flow field data of the turret tip of the axial fan was obtained. The measured data better reflects the zonal flow in the main flow zone and turbulent flow zone of the fan impeller tip area, providing a large amount of experimental data for the development of efficient turbomachinery.