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TECHNICAL PAPERS

The Application of an Aerodynamic Shroud for Axial Ventilation Fans

[+] Author and Article Information
D. R. Neal

Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824nealdoug@msu.edu

J. F. Foss

Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824

J. Fluids Eng 129(6), 764-772 (Jan 02, 2007) (9 pages) doi:10.1115/1.2734206 History: Received June 27, 2006; Revised January 02, 2007

An experimental investigation of an aerodynamic shroud applied to an axial ventilation fan system is reported. The aerodynamic shroud consists of a pressurized plenum and Coanda attachment surface, which also serves as the shroud for the fan. This combination delivers a curved surface wall jet of high momentum air into the tip region of the fan and subsequently into the downstream diffuser region. Simultaneous improvements of performance and efficiency were found for a specific fan geometry with an aerodynamic shroud system when compared with a standard production fan (no shroud) system. Overall, the addition of the aerodynamic shroud was able to increase the system flowrate by 34% while simultaneously improving the efficiency by 13%. A higher efficiency condition (+17%) was also found that resulted in a somewhat lower improvement in flow rate (+23%). These results clearly show that the best blade design for the aerodynamic shroud system is different than the best blade design for a system that does not include the aerodynamic shroud. Particle image velocimetry measurements made at the exit plane of the system’s diffuser provide insight into the mechanistic basis for the performance measurements.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Axial ventilation fans in greenhouse applications

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Figure 2

The aerodynamic shroud concept

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Figure 3

AFRD facility with test fan assembly

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Figure 4

Detailed view of the experimental configuration

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Figure 5

Fan A (left) and Fan B (right)

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Figure 6

Geometric details for Fan A

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Figure 7

Geometric details for Fan B

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Figure 8

Schematic of standard production assembly

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Figure 9

Geometric variables for the diffuser (as described in Table 1)

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Figure 10

Performance data for Fan A with various “shroud on” conditions. (Note: the uncertainty in the ordinate position 0.03Pa is much smaller than the symbol for Figs.  10111213. The abscissa uncertainty is 0.02m3∕s for Figs.  1012. This is also smaller than the symbol.) The scaling parameters for Ψ versus ϕ are found in Table 2.

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Figure 11

Efficiency data for Fan A with various “shroud on” conditions. (Note: the uncertainty in η* is of the order 1.5% for ΔPsys=25Pa.) The scaling parameters for Ψ versus η* are found in Table 2.

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Figure 12

Performance data for Fan B with “shroud on” conditions versus Fan A in the “shroud off” condition. The scaling parameters for Ψ versus ϕ are found in Table 2.

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Figure 13

Efficiency data for Fan B with “shroud on” conditions versus Fan A in the “shroud off” condition. The scaling parameters for Ψ versus η* are found in Table 2.

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Figure 14

Location PIV measurement regions

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Figure 15

Exit velocity profiles for Fan A in both the “shroud off” and best-case “shroud on” conditions

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Figure 16

Exit velocity profiles for Fan B in both the “shroud off” and best-case “shroud on” conditions

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