Conference Paper

Aerodynamic and Aeroacoustic Performance of a Skewed Rotor

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Abstract

This paper presents an experimental investigation and numerical simulation of the aerodynamic and aeroacoustic performance of an axial-flow fan with skewed rotating blades in the design and off-design operation. The blade is designed with a forward skew angle for which the stacking line is directed towards the rotating direction on the circumferential section. A detailed investigation of a three-dimensional flow field in the inter-blade row and passage using five-hole probes and a hot-wire anemometer at the upstream and downstream locations of the rotors has been carried out and compared with a fan with unskewed rotor blades. Noise testing was performed in the anechoic chamber. The experiments were performed at three rotating speeds. Aerodynamic curves show that the performance of the skewed blade increased at a higher pressure rise of 13.1% and gave a larger flow rate of about 5% and a higher efficiency of more than 3%. The higher efficiency in the skewed rotor was due to the practical and advantageous spanwise redistribution of aerodynamic parameters, a greater boundary movement into the main flow, a secondary flow reduction and the thinness of the rotor wake. Aeroacoustic performance and frequency spectra in almost the whole frequency domain showed a noise reduction of 2 to 4 dBA in the skewed fan. Lower noise in the skewed blade comes from the broadband noise reduction owing to a thinner wake layer, a phase difference in rotor radiation and tip leakage noise reduction. A wider stall margin for more than 20% is obtained in the skewed blade due to the proportional distribution of aerodynamic parameters. The three-dimensional Navier-Stokes approach is simulated in the inner blade flow.

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... In the design of turbomachinery blades [4][5][6][7][8][9][10], the use of sweep, lean, and skew (stacking line in rotational direction) in the axial flow compressor rotor has recently become a matter of interest. These blade shape parameters are normally added to minimize shock losses, corner separation in the blade hub and tip clearance losses in the transonic compressor rotor, creating a three-dimensional stacking line. ...
... There have been a variety of research conducted on the benefits of a distorted rotor. Cai, et al. [10] researched the aerodynamic and aeroacoustic characteristics of a skewed blade axial flow fan. With the reduction of the secondary flow and the thinness of the rotor wake, the broadband noise was reduced. ...
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... Recently, the use of sweep, lean (dihedral), and skew (stacking line in rotational direction) in axial flow compressor rotor has become a matter of interest in the design of turbomachinery blades [4][5][6][7][8][9][10]. These blade shape parameters, which form a three-dimensional stacking line, are generally introduced to reduce shock losses, corner separation in the blade hub, and tip clearance losses in transonic compressor rotor. ...
... A number of studies have been done on the advantages of a skewed rotor. Cai, et al. [9] studied on aerodynamic and aeroacoustic characteristics of an axial flow fan with skewed blade. With the reduction of a secondary flow and the thinness of a rotor wake, they reduced a broadband noise. ...
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... The use of sweep, lean (dihedral), and skew (shifting stacking line in rotational direction) in an axial flow compressor rotor has become a matter of interest in the design of turbomachinery blades by many researchers [1][2][3][4][5]. These blade shape parameters, which form a three-dimensional stacking line, are generally introduced to reduce shock losses, corner separation in the blade hub, and tip clearance losses in transonic compressor rotors. ...
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