Influence of Design Parameters on the Global Performances of Low-Speed Counter-Rotating Axial-Flow Fans
Juan Wang, Florent Ravelet, Farid Bakir
2014
Volume 1B, Symposia: Fluid Machinery; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Multiscale Methods for Multiphase Flow; Noninvasive Measurements in Single and Multiphase Flows
unpublished
The present work aims at experimentally investigating the effects of some parameters on the performances of a counterrotating stage, and on the instationary flow between the rotors. Three counter-rotating fans, which have the same design point, have been designed. These systems differ by the distribution of the loading and of the ratio of angular velocity between the front rotor and the rear rotor. All the configurations have been tested in a normalized test rig, where the ratio of angular
more »
... ities and the axial distance between the two rotors can be varied. The influence of these parameters are then addressed by analysing the experimental results of the static pressure rise and static efficiency, as well as of the wall pressure fluctuations registered by a microphone at the wall. The three systems achieve the design point with a high efficiency. The counter-rotating systems lead to at least a 10 percentage points gain in static efficiency at the design flow rate, compared to the typical peak efficiency of a traditional rotor-stator stage. Meanwhile, counter-rotating systems display good working stabilities at very low volume flow rates. In addition, at the design speed ratio, the overall performance decreases almost monotonically with the axial distance. Nevertheless, an optimum in axial distance can be found for higher speed ratios. Finally, the investigations of the wall pressure fluctuations show that the amplitudes of power spectral density corresponding to the blade passing frequency of the rear rotor are significantly higher than that of the front rotor. The interaction peaks are also stronger for an equal distribution of the work on the two rotors. NOMENCLATURE ∆P t Total pressure rise (Pa) ∆P s Static pressure rise (Pa) D Pipe diameter (mm) Q v Volume flow rate (m 3 .s −1 ) R tip Blade tip radius(mm) R hub Blade hub radius (mm) N Rotational speed of rotor (rpm) θ Rotational speed ratio N RR N FR L Distribution of load ∆P t, RR ∆P t, FR +∆P t, RR Z Number of blades P w Power consumption of the rotor (W) Z p Axial position of microphone S Axial distance between front rotor and rear rotor (mm) L chord Blade chord (mm) W Relative velocity (m.s −1 ) U Rotor velocity (m.s −1 ) C a Axial velocity (m.s −1 ) p ′ Wall pressure fluctuation (Pa) γ Stagger angle ρ a Density of air (kg.m −3 ) τ torque (N.m) µ Dynamic viscosity of the fluid (Pa.s) 1
doi:10.1115/fedsm2014-22172
fatcat:b7svl6qjqnfcfprdkezq3vuomq
