Efficiency gain of low-speed axial flow rotors due to forward sweep

The paper aims at discovering the relationship between the spanwise gradient of blade circulation and the total efficiency gain due to forward sweep, in the case of low-speed axial flow fans, at the design point. For this purpose, an extensive set of literature data have been processed and evaluated by statistical means. A trend function has been established for quantifying the aforementioned relationship. By such means, it has been pointed out that the efficiency gain due to forward sweep tends to increase with the spanwise gradient of blade circulation. This means that the purposeful incorporation of forward sweep in the design process offers an increased potential for efficiency improvement in the case of rotors of controlled vortex design. The maximum efficiency gain has been observed to be 2% to 3%, due to an in-house developed design method. It has been noted that the efficiency improvement due to forward sweep tends to be minor for free-vortex rotors. Furthermore, the efficiency tends to deteriorate if spanwise decreasing blade circulation occurs in forward-swept rotors. Remarks have been made on the means of simultaneous reduction of loss and noise related to low-speed axial fans, for a prescribed aerodynamic performance.

[1]  Cs. Horvath,et al.  Aerodynamic effects of forward blade skew in axial flow rotors of controlled vortex design , 2007 .

[2]  János Vad,et al.  Influence of Blade Sweep on the Energetic Behavior of Axial Flow Turbomachinery Rotors at Design Flow Rate , 2004 .

[3]  Alessandro Corsini,et al.  Using sweep to extend the stall-free operational range in axial fan rotors , 2004 .

[4]  Alessandro Corsini,et al.  The application of sinusoidal blade-leading edges in a fan-design methodology to improve stall resistance , 2014 .

[5]  I︠u︡. V. Linnik.  Méthodes des moindres carrés : eléments de la théorie du traitement statistique des observations , 1963 .

[6]  Tamás Benedek,et al.  Beamforming measurements of an axial fan in an industrial environment , 2013 .

[7]  M. Govardhan,et al.  Study of Sweep and Induced Dihedral Effects in Subsonic Axial Flow Compressor Passages—Part I: Design Considerations—Changes in Incidence, Deflection, and Streamline Curvature , 2009 .

[8]  János Vad,et al.  Forward Blade Sweep Applied to Low-Speed Axial Fan Rotors of Controlled Vortex Design: An Overview , 2012 .

[9]  Andrea Lazzaretto,et al.  Design Guidelines to Increase the Performance of a Rotor-Only Axial Fan With Constant-Swirl Blading , 2014 .

[10]  Li Yang,et al.  Optimization Design and Experimental Study of Low-Pressure Axial Fan with Forward-Skewed Blades , 2007 .

[11]  János Vad.  Aerodynamic effects of blade sweep and skew in low-speed axial flow rotors at the design flow rate: An overview , 2008 .

[12]  D. Prithvi Raj,et al.  Closure to “Discussion of ‘Investigations on Axial Flow Fan Impellers With Forward Swept Blades’” (1977, ASME J. Fluids Eng., 99, p. 547) , 1977 .

[13]  János Vad,et al.  Concerted Aerodynamic and Acoustic Diagnostics of an Axial Flow Industrial Fan, Involving the Phased Array Microphone Technique , 2014 .

[14]  János Vad.  Incorporation of forward blade sweep in preliminary controlled vortex design of axial flow rotors , 2012 .

[15]  K. Helming.  Numerical Analysis of Sweep Effects in Shrouded Propfan Rotors , 1996 .

[16]  B. F. Beacher,et al.  The Impact of Forward Swept Rotors on Tip-Limited Low-Speed Axial Compressors , 2003 .