Design and Study of Performance Characteristics of Flat Wall Rectilinear 3D Diffuser with Square Inlet and Rectangular Outlet

doi:10.23940/ijpe.20.05.p2.691701

Abstract

Abstract:

The present study explores the design of a flat wall rectilinear 3D diffuser with square inlet and a rectangular outlet for subsonic, incompressible flow. In this 3D diffuser, the diffuser walls are diverged in the horizontal plane to control the flow separation from the walls of the diffuser, which results in a decrease in the coefficient of static pressure recovery; this is a phenomenon called ‘stall’. In case of a wide angled 2D diffuser, 'stall' is a serious issue. In present work, a 3D diffuser was designed with the same area ratio (4), aspect ratio (1), and non-dimensional length (8.21) as those of a 2D diffuser. With varying Reynolds numbers, it was found that the coefficient of static pressure recovery increases continuously for the 3D diffuser. In case of the 2D diffuser, it decreases as the Reynolds number exceeds 2×10⁵. From CFD analysis, it was found that vectors lie in the mid-longitudinal plane. A three-hole probe was used to measure local velocity to achieve velocity profiles at five different -2 equally distant planes between the inlet and outlet. The maximum error in the experimental results and that of the CFD analysis for the velocity profile and coefficient of static pressure recovery were 9% and 1.02%, respectively.

Key words: flat wall rectilinear 3D diffuser, stall, coefficient of static pressure recovery, CFD analysis, three-hole probe

Manish Kumar and Shailendra Kumar. Design and Study of Performance Characteristics of Flat Wall Rectilinear 3D Diffuser with Square Inlet and Rectangular Outlet [J]. Int J Performability Eng, 2020, 16(5): 691-701.

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Figures/Tables 22

Figure 1.

Table 1

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Figure 2.

Figure 3.

Figure 4.

Table 5

Fluid properties at atmospheric conditions"

Temperature	t = 36 $℃$
Atmospheric pressure	73.3cm of Hg = 97793.928Pa
Density of air at 36 degree Celsius	= 1.102kg/m³
Density of water at 36 degree Celsius	= 996.087kg/m³

Table 5

Figure 5.

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Table 6

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References 11.

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i		Average static pressure in mm of the inclined water column	Average static pressure in mm of the vertical water column	in (Pa)	%
1	0.5781	-22.00	-19.13	-187.01	75.29
2	0.6624	-17.25	-15.07	-147.27	79.67
3	0.7468	-14.00	-12.18	-118.98	82.77
4	0.8312	-11.25	-9.77	-95.49	85.29
5	0.9156	-9.50	-8.17	-79.84	87.03

I		Average static pressure in mm of inclined water column	Average static pressure in mm of vertical water column	in (Pa)	%
1	0.5781	-22.00	-19.13	-187.01	75.29
2	0.6624	-17.25	-15.07	-147.27	79.67
3	0.7468	-14.00	-12.18	-118.98	82.77
4	0.8312	-11.25	-9.77	-95.49	85.29
5	0.9156	-9.50	-8.17	-79.84	87.03