Research Papers: Gas Turbines: Turbomachinery

Forward Blade Sweep Applied to Low-Speed Axial Fan Rotors of Controlled Vortex Design: An Overview

[+] Author and Article Information
János Vad

Department of Fluid Mechanics,
Budapest University of
Technology and Economics,
Bertalan Lajos u. 4–6,
H-1111 Budapest, Hungary

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 16, 2012; final manuscript received July 12, 2012; published online November 21, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(1), 012601 (Nov 21, 2012) (9 pages) Paper No: GTP-12-1152; doi: 10.1115/1.4007428 History: Received June 16, 2012; Revised July 12, 2012

An overview is given on the research maintained by the author about the design aspects of three-dimensional blade passage flow in low-speed axial flow industrial fan rotors, affected by spanwise changing design blade circulation due to controlled vortex design (CVD), blade forward sweep (FSW), and their combination. It was pointed out that, comparing the CVD method to the free vortex design, the fluid in the blade suction side boundary layer has an increased inclination to migrate radially outward, increasing the near-tip blockage and loss. It was concluded that the benefit of FSW, in terms of moderating loss near the tip, can be better utilized for the rotors of the CVD, in comparison to the free vortex design. Compared to the free vortex design, the FSW applied to the blades of the CVD was found to also be especially beneficial in loss reduction away from the endwalls, via shortening the flow paths on the suction side—in any case being elongated by the radially outward flow due to CVD—and thus, reducing the effect of wall skin friction. The necessity of correcting the swept blades was pointed out for matching with the prescribed CVD circulation distribution.

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Fig. 1

Fan rotors of the CVD and the FSW/FSK

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Fig. 2

Secondary flow vector diagrams for a CVD rotor [18] on planes normal to the rotational axis. The leading and trailing edges are at X = 0 and X = 1, respectively.

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Fig. 3

Secondary flow vector plots for rotor exit planes

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Fig. 4

Plots of the rotor exit relative kinetic energy defect coefficient ζ. Increment: 0.05.

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Fig. 5

Contribution of the effect of the spanwise changing blade circulation to the endwall blockage

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Fig. 6

Sketch of the suppression of the radially outward flow of the SS BL fluid by means of the FSW

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Fig. 7

Examples for the variance of the total pressure loss with blade solidity

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Fig. 8

Flow path-elongating effect due to the CVD; shortening of the flow path by means of the FSW

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Fig. 10

Evolution of the total pressure loss coefficient inside the blade passages at 10% and 98% blade chord (adapted from Ref. [1]). Bold arrows: location of the entrance and exit of the studied flow paths. (LE and TE: leading and trailing edges.)

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Fig. 9

Computed static pressure coefficient Cp distribution and limiting streamlines on the USW and FSW blades on the SS (adapted from Ref. [1]). The studied flow paths are indicated with bold lines. (LE and TE: leading and trailing edges.)

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Fig. 11

Computed inlet axial velocity profiles along the span. White dots: USW. Black dots: FSK.

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Fig. 12

Isentropic total pressure rise distributions along the span. (a) Computations [11]. White dots: USW. Black dots: FSK. (b) Measurements [36].

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Fig. 13

The USW rotors of the FVD versus the CVD: comparison of the SS phenomena

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Fig. 14

Applying the FSW to the rotors of the FVD versus the CVD: comparison of the SS phenomena




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