Sage Journals: Discover world-class research

Abstract

Common blade design techniques are based on the assumption of the airflow laying on cylindrical surfaces. This behaviour is proper only for free-vortex flow, whereas radial fluid migration along the span is always present in case of controlled vortex design blades. The paper presents a design procedure to increase aeraulic efficiency of fan rotors originally designed using a controlled vortex criterion, based on the assumption that a blade section positioning taking into account the actual airflow direction could be beneficial for rotor aeraulic performance. The proposed procedure employs a three-dimensional aerofoil positioning and blade forward sweep. The procedure is applied to a rotor-only tube-axial fan featuring a 0.44 hub-to-tip ratio, an almost constant swirl velocity distribution at the rotor outlet and a quite low blade Reynolds number. Rotor prototypes deriving from step-by-step blade modifications are experimentally tested on an ISO 5801 standard test rig. Results show the importance of considering radial fluid migration for highly loaded rotors.

Keywords

Rotor-only tube-axial fan fan efficiency forward sweep controlled vortex axial fan arbitrary vortex ducted fan

Get full access to this article

View all access options for this article.

References

Regulation of the European Commission (EU of 30 March 2011). Implementing Directive 2009/125/EC of the European Parliament and of the Council of the European Union with regard to ecodesign requirements for fans driven by motors with an electric input power between 125 W and 500 kW. Official Journal of the European Union, No.327/2011, 6 April 2011, pp.8–21.

Downie

Thompson

Wallis

. An engineering approach to blade designs for low to medium pressure rise rotor-only axial fans. Exp Therm Fluid Sci 1993; 6: 376–401.

Vad

. Correlation of flow path length to total pressure loss in diffuser flows. Proc IMechE, Part A: J Power and Energy 2011; 225: 481–496.

Vad

. Radial fluid migration and endwall blockage in axial flow rotors. Proc IMechE, Part A: J Power and Energy 2010; 224: 399–417.

Vad

Halász

Benedek

. Efficiency gain of low-speed axial flow rotors due to forward sweep. Proc IMechE, Part A: J Power and Energy 2015; 229: 16–23.

Vad

. Incorporation of forward blade sweep in preliminary controlled vortex design of axial flow rotors. Proc IMechE, Part A: J Power and Energy 2012; 226: 462–478.

Masi M and Lazzaretto A. A simplified theory to justify forward sweep in low hub-to-tip ratio axial fan. In: ASME Turbo Expo 2015: turbine technical conference and exposition, Montreal, Canada, 15–19 June 2015, ASME paper GT2015-43029, Vol. 1A: Aircraft engine; fans and blowers. New York: ASME.

Masi M, Piva M and Lazzaretto A. Design guidelines to increase the performance of a rotor-only axial fan with constant-swirl blading. In: ASME Turbo Expo 2014: turbine technical conference and exposition, Düsseldorf, Germany, 16–20 June 2014, Vol. 1A: Aircraft engine; fans and blowers. New York: ASME.

ISO 5801:2011. Industrial fans – performance testing using standardized airways.

10.

Wallis

. Axial flow fans and ducts, Reprint ed. Malabar: Krieger Publishing, 1993.

11.

Emery C, Herrig LJ, Erwin JR, et al. Systematic two-dimensional cascade tests of NACA 65-series compressor blades at low speeds. NACA Report 1368, Langley Memorial Aeronautical Laboratory, Langley Field, VA, January 1958.

12.

Pelz

Stonjek

. The influence of Reynolds number and roughness on the efficiency of axial and centrifugal fans-a physically based scaling method. J Eng Gas Turbine Power 2013; 135.

Forward sweep to improve the efficiency of rotor-only tube-axial fans with controlled vortex design blades

Abstract

Keywords

Get full access to this article

References