Experimental Study of the Instationary Flow Between Two Ducted Counter-Rotating Rotors

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. An experimental study on counter-rotating axial-flow fans was carried out. The fans of diameter D = 375 mm were designed to match the specification point using an original method. The counter-rotating fans operate in a ducted-flow configuration and the overall performances are measured in a normalized test bench. The rotation rate of each fan is independently controlled and the axial spacing between rotors can be varied from S = 10 to S = 180 mm. Systematic measurements of the global performances and local measurements of the velocity field and of the wall pressure fluctuations are performed, in order to first validate the design method, and to explore the effects of the two specific free parameters of the system: the axial spacing and the ratio of rotation rates. The results show that the efficiency is strongly increased compared to a conventional rotor or to a rotor-stator stage. The developped design method slightly over-predicts the pressure rise and slightly under-predicts the best rotation ratio. The system is moreover highly efficient on a wide range of flow-rates and pressure rises: this system has thus a very flexible use, with a large patch of high efficient operating points in the parameter space.Atmospheric

Experimental investigation on the effect of load distribution on the performances of a counter-rotating axial-flow fan

“…In the design procedure of a CRS that has been developed at the DynFluid Laboratory [9], the front rotor is first designed to achieve a part of the total pressure rise at the design flow rate. This is done with the in-house software MFT (Mixed Flow Turbomachinery), described in Ref.…”

“…The volumetric flow rate and total pressure rise are the same as for the first prototype -HSN-described and analyzed in Ref. [9]. All the rotors are made of blades of circular-arc camber lines, with NACA65 profiles.…”

“…The rear rotor has two functions: it converts part of the rotational kinetic energy of the flow coming from the front rotor to static head and also supplies energy to the fluid. A high performance and compact turbomachine can therefore been designed, with a reduction of the rotational speed and a better homogenization of the flow downstream of the stage, compared to a single rotor or rotor-stator stage [8][9][10]. On the other hand, counter-rotating turbomachines present some drawbacks such as an increase in mechanical complexity, or a potential increase in noise generation.…”

“…Cao et al [15] used Computational Fluid Dynamics results to re-design the rear rotor of a counter-rotating pump and obtain an increase in performances with respect to the original rear rotor conventional design. Finally, in the Dynfluid Laboratory from Arts et Métiers-ParisTech University, series of experiments focused on the validation of an original design method for ducted low-speed counter-rotating axial-flow fans have been performed [9]. Based on this work, three different counter-rotating stages (JW1, JW2 and JW3) have been designed to attain the same specifications, while varying the distribution of the work performed by the front and rear rotors.…”

Unsteady Flow Condition between Front and Rear Rotor of Contra-Rotating Small Sized Axial Fan

“…The blade row distance between the front and rear rotors is a key parameter to consider the wake and potential interaction for the contra-rotating fan. The influence of the blade row distance between the front and rear rotors and pressure fluctuations on the casing wall were investigated for the counter rotating fan with fan diameter D = 375 mm [4] [8]. On the other hand, the conventional design method and the theory for the turbomachinery should be modified for small-sized axial fans because small-sized axial fans applied to electrical devices belong to extremely small size field in the turbomachinery [9].…”