Flow in a Centrifugal Fan Impeller at Off-Design Conditions

Abstract

Predicted and measured surface velocity and pressure distributions in the internal flow channels of a centrifugal fan impeller are presented for volume flow rates between 80 and 125 percent of design flow rate. Predictions are based on a fully three-dimensional, finite element analysis of the inviscid, incompressible blade channel flow. Additional predictions using a conventional quasi-three-dimensional analysis are presented for comparison. Experimental results were developed using extensive blade and sidewall surface pressure taps installed in a scale model of an airfoil-bladed centrifugal fan impeller designed for heavy industrial and power generation applications. The results illustrate the ability of both flow analyses to predict the dominant features of the impeller flow field, including peak blade surface velocities and adverse gradients at flows far from the design point. In addition, the experimental results provide valuable insight into the limiting channel diffusion values for typical centrifugal cascade performance, and the influence of viscous effects as seen in deviations from the ideal flow predictions.

Numerical simulations of flows in centrifugal turbomachinery

“…[18,19,201. This fan is typical of those used in fossil fuel power plants and in industrial eration and local time stepping were used in both the inviscid and viscous flow calculations.…”

“…Conclusions A quasi-three-dimensional Navier-Stokes procedure has been modified and applied to steady and unsteady flows in centrifugal turbomachinery. The numerical analysis (RADFAN) was validated using the radial fan geometry of Wright [18,19,201. Predicted blade loadings and performance parameters showed very good agreement with the experimental data.…”

“…The RADFAN procedure was chosen for this investigation because its flexible C-type computational grid topology eases the burden of grid generation for centrifugal geometries and because of the numerical algorithm's proven accuracy and efficiency, in both steady and time-dependent problems [lS, 17, 151. Validation of the RADFAN analysis was accomplished by performing inviscid and viscous simulations of the Row through the Wright radial fan [18,19,201, and comparing the results to experimental data. To assess the ability of RADFAN to predict impeller performance at off-design flow conditions, numerical simulations were performed for the Worthington impeller [21] a t three different operating conditions, and the predicted numerical results were compared with -'…”

Unsteady Pressure Measurements in a Rotating Centrifugal Impeller

“…MUller and Fiala [11] used a pressure probe which was traversed at several locations inside the channel of a centrifugal fan in order to determine the mean static pressure, and the mean vector of the relative velocity and its fluctuation. Measurements of the steady static pressure distribution on the blade and side wall surfaces of a centrifugal impeller were carried out by Wright et al [12] using a rotating scanivalve unit. Kjork and Lofdahl [13] determined the three mean velocity components as well as five of the Reynolds stresses of the impeller channel flow using a hotwire probe.…”

Fluid Flow Analysis of a Single-Stage Centrifugal Fan with a Ported Diffuser

“…Secondly, the cooling fan takes shaft space and a longer and thicker shaft has to be used compared to the through-flow type units. The through flow type units are used in most of the household vacuum cleaners (Wright, 1984;Wright, Tzou and Madhavan, 1984;Yu et al, 2005). Since the main air flow sucked by the working fan flows through the motor and cools the motor, the air has to be clean.…”