Simple 3D Numerical Analysis of Flow in a Centrifugal Fan

Detailed analysis of flows in centrifugal fans is required for improvement of efficiency and for noise reduction. However, both experimental and numerical analysis of the flow are very difficult, because the geometric configuration of the fan causes 3D flow. Even though a 2D model is applied for the analysis in regard to the flow through a part of the impeller in the rotational co-ordinate, it is not easy to determine the boundary condition at the position of the side wall of the scroll. Therefore totally 3D analysis of the whole flow field is required, but it is very time-consuming. This paper describes a simple numerical method of 3D analysis of the flow in a model of a flat-blade centrifugal fan with a scroll. In this method, the 3D flow through the partly divided portion of the fan at an arbitrary scroll angle is analyzed in rotational co-ordinates by assuming that the side wall of the scroll is replaced by the velocity boundary determined by the volume-increasing ratio at the scroll angle