Numerical and experimental study of unsteady flow in a centrifugal fan

Abstract

In the current work, computational fluid dynamics (CFD) technique coupled with experimental investigations has been used in order to study the complex phenomena related to the unsteady flow in a centrifugal fan.The studied phenomena are the interactions and unsteadiness induced by the rotating blades motion relatively to the volute and their impact on the aeroacoustic behaviour of the fan. Thus, three-dimensional and two-dimensional unsteady simulations have been carried out using unsteady Reynolds averaged Navier-Stokes approach. Turbulence has been modelled with the k-ω-shear stress model and a sliding mesh technique has been applied to the interfaces in order to allow unsteady interactions between the rotating (impeller) and the stationary zones (volute casing). The overall performances predicted by the computations have been validated at different flowrates.In order to locate the flow unsteadiness and perturbations, the near field wall pressure fluctuations at different strategic points on the volute surface have been computed. In addition to this, the unsteady flow variables provided by the CFD calculations have been used as inputs in the Ffowcs Williams-Hawkings equation in order to estimate the tonal noise generated by the centrifugal fan. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found. fields provides efficient tool for analysis and design. Thus, flow analysis techniques using unsteady Reynolds averaged Navier-Stokes (URANS) approach have made remarkable progress in several engineering applications.Recently, more attention has been paid to the study of unsteady phenomena in turbomachines. These phenomena are the interactions and unsteadiness induced by the relative motion of the rotor with respect to the stator.As concerns centrifugal fans, Liu et al.[1] used three-dimensional numerical simulations of the complete unsteady flow field to obtain the aerodynamic sound sources. In their study, the aerodynamic sound is calculated using the Lowson equation [2]. Using this technique, they showed the effect of the distance between the impeller tip and the volute tongue on JPE445

Influence of Impeller Geometry on the Unsteady Flow in a Centrifugal Fan: Numerical and Experimental Analyses

“…The grid refinement has been studied and adapted to the flow morphology minimizing element distortion and to achieve required resolution in high-gradient regions. The details of this study are reported in previous papers by Younsi et al [7,8]. An example of the retained grid mesh International Journal of Rotating Machinery is shown in Figure 6.…”

Experimental study on the noise reduction of an industrial forward-curved blades centrifugal fan

“…And most of them focus their attentions on the FC multi-blade, BC blades and radial blades centrifugal fans. With respect to the noise generation mechanism of centrifugal fans, Velarde-Suárez et al [4,5], Younsi et al [6] and Lin et al [7] studied the unsteady flow and aerodynamic tonal noise of FC multi-blade centrifugal fans. In the other paper, Sasaki [8] explored the influence of Karman Vortex Street on the broadband noise generated from an FC multi-blade fan.…”

Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

“…Sampling begins when it is stable after calculation for 10 cycles. Figure 3 shows the diagram of the experimental system for the aerodynamic performance, where an outlet chamber is established to measure the related physical parameters [8]. The discharge static pressure of the tested fan is measured using a pressure transducer installed in the chamber.…”