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Research Papers

Performance Testing of an Axial Flow Fan Designed for Air-Cooled Heat Exchanger Applications

[+] Author and Article Information
Michael B. Wilkinson

Department of Mechanical and
Mechatronic Engineering,
Stellenbosch University,
Private Bag X1,
Stellenbosch 7602, South Africa
e-mail: mikebrierswilkinson@gmail.com

Sybrand J. van der Spuy, Theodor W. von Backström

Department of Mechanical and
Mechatronic Engineering,
Stellenbosch University,
Private Bag X1,
Stellenbosch 7602, South Africa

Manuscript received June 26, 2018; final manuscript received July 10, 2018; published online December 7, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(5), 051007 (Dec 07, 2018) (9 pages) Paper No: GTP-18-1362; doi: 10.1115/1.4041010 History: Received June 26, 2018; Revised July 10, 2018

An axial flow fan developed in the previous study is tested in order to characterize its performance. The M-fan, a 7.3152 m diameter rotor only axial flow fan was designed to perform well under the challenging operating conditions encountered in air-cooled heat exchangers. Preliminary computational fluid dynamics (CFD) results obtained using an actuator disk model (ADM) as well as a periodic three dimensional model indicate that the fan meets the specified performance targets, with an expected total-to-static efficiency of 59.4% and a total-to-static pressure rise of 114.7 Pa at the operating point. Experimental tests are performed on the M-fan in order to determine its performance across a full range of flow rates. A range of fan configurations are tested in order to ascertain the effect of tip clearance, blade angle, and hub configuration on fan performance. Due to the lack of a suitable facility for testing a large diameter fan, a scaled 1.542 m diameter model is tested on the ISO 5801 type A fan test facility at Stellenbosch University. A Reynolds-averaged Navier–Stokes CFD model representing the M-fan in the test facility is also developed in order to provide additional insight into the flow field in the vicinity of the fan blades. The results of the CFD model will be validated using the experimental data obtained. Both the CFD results and the experimental data obtained are compared to the initial CFD results for the full scale fan, as obtained in the previous study, by means of fan scaling laws. Experimental data indicate that the M-fan does not meet the pressure requirement set out in the initial study at the design blade setting angle of 34 deg. Under these conditions, the M-fan attains a total-to-static pressure rise of 102.5 Pa and a total-to-static efficiency of 56.4%, running with a tip gap of 2 mm. Increasing the blade angle is shown to be a potential remedy, improving the total-to-static pressure rise and efficiency obtained at the operating point. The M-fan is also shown to be highly sensitive to increasing tip gap, with larger tip gaps substantially reducing fan performance. The losses due to tip gap are also shown to be overestimated by the CFD simulations. Both experimental and numerically obtained results indicate lower fan total-to-static efficiencies than obtained in the initial CFD study. Results indicate that the M-fan is suited to its intended application, however, it should be operated with a smaller tip gap than initially recommended and a larger blade setting angle. Hub configuration is also shown to have an influence on fan performance, potentially improving performance at low flow rates.

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References

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Wilkinson, M. B. , van der Spuy, J. , and von Backström, T. W. , 2017, “ The Design of a Large Diameter Axial Flow Fan for Air-Colled Heat Exchanger Applications,” ASME Paper No. GT2017-63331.
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Figures

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Fig. 1

Schematic of the M-fan

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Fig. 3

Illustration of flat plate (L) and box hub (R) configurations as tested

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Fig. 4

ISO 5801 Type A test facility at Stellenbosch University (adapted from Ref. [14])

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Fig. 5

Periodic three-dimensional domain

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Fig. 6

Periodic three-dimensional inlet or outlet domain

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Fig. 7

Comparison of CFD and experimental fan total-to-static pressure versus volume flow rate characteristics for the M-fan with a range of tip gaps and a blade setting angle of 34 deg

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Fig. 8

Comparison of CFD and experimental fan power versus volume flow rate characteristics for the M-fan with a range of tip gaps and a blade setting angle of 34 deg

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Fig. 9

Comparison of CFD and experimental fan total-to-static efficiency versus volume flow rate characteristics for the M-fan with a range of tip gaps and a blade setting angle of 34 deg

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Fig. 10

Fan total-to-static pressure versus volume flow rate characteristic for different blade angles with a 2 mm tip gap

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Fig. 11

Fan power versus volume flow rate characteristic for different blade angles with a 2 mm tip gap

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Fig. 12

Fan total-to-static efficiency versus volume flow rate characteristic for different blade angles with a 2 mm tip gap

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Fig. 13

Comparison of fan total-to-static pressure versus volume flow rate characteristics for the M-fan with box hub and flat plate hub configurations with a 2 mm tip gap

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Fig. 14

Comparison of fan power versus volume flow rate characteristics for the M-fan with box hub and flat plate hub configurations with a 2 mm tip gap

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Fig. 15

Comparison of fan total-to-static efficiency versus volume flow rate characteristics for the M-fan with box hub and flat plate hub configurations with a 2 mm tip gap

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Fig. 16

Comparison of CFD and ADM fan total-to-static pressure characteristics from Wilkinson et al. [3] to scaled CFD and experimental data

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Fig. 17

Comparison of CFD and ADM fan power pressure characteristics from Wilkinson et al. [3] to scaled CFD and experimental data

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Fig. 18

Comparison of CFD and ADM fan total-to-static efficiency characteristics from Wilkinson et al. [3] to scaled CFD and experimental data

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