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Research Papers: Flows in Complex Systems

Investigations Into the Flow Behavior in a Nonparallel Shrouded Diffuser of a Centrifugal Fan for Augmented Performance

[+] Author and Article Information
N. Madhwesh

Department of Mechanical and
Manufacturing Engineering,
Manipal Institute of Technology,
Manipal Academy of Higher Education,
Manipal 576104, Karnataka, India
e-mail: madhwesh.n@manipal.edu

K. Vasudeva Karanth

Department of Mechanical and
Manufacturing Engineering,
Manipal Institute of Technology,
Manipal Academy of Higher Education,
Manipal 576104, Karnataka, India
e-mail: kv.karanth@manipal.edu

N. Yagnesh Sharma

Department of Mechanical and
Manufacturing Engineering,
Manipal Institute of Technology,
Manipal Academy of Higher Education,
Manipal 576104, Karnataka, India
e-mail: yagnesh.sharma@manipal.edu

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 27, 2017; final manuscript received February 13, 2018; published online March 29, 2018. Assoc. Editor: Kwang-Yong Kim.

J. Fluids Eng 140(8), 081103 (Mar 29, 2018) (12 pages) Paper No: FE-17-1615; doi: 10.1115/1.4039413 History: Received September 27, 2017; Revised February 13, 2018

It is a well-known fact that the diffuser of a centrifugal fan plays a vital role in the energy transformation leading to better static pressure rise and efficiency. Many researchers have worked on modified geometry with respect to both impeller and diffuser so as to extract better efficiency of the fan. This paper highlights a unique numerical study on the performance of a centrifugal fan, which has a diffuser having nonparallel shrouds. The shroud geometry is parametrically varied by adopting various convergence ratios (CR) for the nonparallel shrouds encompassing the diffuser passage. It is revealed in the study that there exists an optimal CR for which the performance is improved over the regular parallel shrouded diffuser passage (base model). It is observed from the numerical analysis that for a nonparallel convergent shroud corresponding to a CR of 0.35, a relatively higher head coefficient of 3.6% is obtained when compared to that of the base model. This configuration also yields a higher theoretical efficiency of about 2.1% corroborating the improvement in head coefficient. This study predicts a design prescription for nonparallel diffuser shrouds of a centrifugal fan for augmented performance due to the fact that the converging region accelerates and guides the flow efficiently by establishing radial pressure equilibrium.

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Figures

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Fig. 1

Experimental test rig used for the study

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Fig. 2

Plot of overall efficiency at various capacity coefficients

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Fig. 3

Graphical layout of centrifugal fan test rig

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Fig. 4

Meridional view of diffuser shroud configurations used in the current analysis: (a) base model and (b) converging shroud

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Fig. 5

Geometric configurations of the diffuser shrouds considered for the study: (a) parallel shroud model (base model) and (b) convergent diffuser shroud model

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Fig. 6

Three-dimensional CFD fluid flow domain of the centrifugal fan

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Fig. 7

Grid Independence test results based on head coefficient

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Fig. 8

Grid Independence test results based on theoretical efficiency

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Fig. 9

An enlarged picture of meshing of computational domain

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Fig. 10

Variation of static pressure difference with respect to capacity coefficient

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Fig. 11

Numerical and experimental validation curves: (a) main characteristics and (b) operating characteristics

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Fig. 12

Normalized velocity vector plots for the base model configuration: (a) normalized velocity vector plot for the base model configurations (front view), (b) normalized velocity vector plot for the base model configuration (profile view), and (c) magnified view across section AA–BB

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Fig. 13

Variation of static pressure rise coefficient for various convergent diffuser shrouded configurations for higher mass flow rate

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Fig. 14

Normalized velocity vector plots for different convergent diffuser shrouded configurations: (a) configuration C1 (CR = 0.07), (b) configuration C2 (CR = 0.14), (c) configuration C3 (CR = 0.21), (d) configuration C4 (CR = 0.28), (e) configuration C5 (CR = 0.35), and (f) configuration C6 (CR = 0.42)

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Fig. 15

Variation of total pressure loss coefficient for various convergent diffuser shrouded configurations for higher mass flow rate

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Fig. 16

Variation of static pressure rise coefficient and turbulent viscosity ratio for various convergent diffuser shrouded configurations for higher mass flow rate

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Fig. 17

Variation of static pressure rise coefficient and skin friction loss coefficient for various convergent diffuser shrouded configurations for higher mass flow rate

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Fig. 18

Front view of normalized velocity vector plot for the configuration C5 (CR = 0.35)

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Fig. 19

Normalized velocity contour plot for C5 configuration (CR = 0.35) of convergent diffuser shrouds

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Fig. 20

Normalized velocity contour plot for C6 configuration (CR = 0.42) of convergent diffuser shrouds

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Fig. 21

Variation of static pressure rise coefficient for various convergent diffuser shrouded configurations

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Fig. 22

Plot of main characteristics for the best nonparallel diffuser shrouded configuration and the base model based on the exit of the diffuser

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Fig. 23

Plot of theoretical efficiency for the best nonparallel diffuser shrouded configuration and base model

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Fig. 24

Plot of main characteristics for the best nonparallel diffuser shrouded configuration and the base model based on the exit of the impeller

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