Effect of Varying Inflow Reynolds Number on Pressure Recovery and Flow Uniformity of 3-D Turning Diffuser

Abstract:

Various diffuser types characterized by the geometry are introduced in the flow line to recover the energy. A 3-D turning diffuser is a type of diffuser that its cross-section diffuses in all 3 directions of axes, i.e. x, y and z. In terms of applicability, a 3-D turning diffuser offers compactness and more outlet-inlet configurations over a 2-D turning diffuser. However, the flow within a 3-D turning diffuser is expected to be more complex which susceptible to excessive losses. As yet there is no established guideline that can be referred to choose a 3-D turning diffuser with an optimum performance. This paper aims to investigate the effects of varying inflow Reynolds number (Re_in) on the performance of 3-D turning diffuser with 90^o angle of turn. The outlet pressure recovery (C_p) and flow uniformity (σ_u) of 3-D turning diffuser with an area ratio (AR = 2.16) and outlet-inlet configurations (W₂/W₁ = 1.44, X₂/X₁ = 1.5), operated at inflow Reynolds number of Re_in = 5.786E+04 - 1.775E+05 have been experimentally tested. The experimental rig was developed by incorporating several features of low subsonic wind tunnel. This was mainly to produce a perfect fully developed and uniform flow entering diffuser. Particle image velocimetry (PIV) was used to examine the flow quality, and a digital manometer was used to measure the average static pressure of the inlet and outlet of turning diffuser. There is a promising improvement in terms of flow uniformity when a 3-D turning diffuser is used instead of a 2-D turning diffuser with the same AR. An unexpected trend found with a drop of pressure recovery at maximum operating condition of Re_in = 1.775E+05 shall require further investigations. The results obtained from this study will be in future used to validate the numerical codes. Upon successful validation, several other configurations will be numerically tested in order to establish the guidelines in the form of mathematical models.

• Periodical: Applied Mechanics and Materials (Volume 699)
• Pages: 422-428
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.699.422
• Online since: November 2014
• Authors: Normayati Nordin, Zainal Ambri Abdul Karim, Safiah Othman, Vijay R. Raghavan
• Keywords: Flow Uniformity, Particle Image Velocimetry (PIV), Pressure Recovery, Turning Diffuser

References

[1] N. Nordin, V.R. Raghavan, S. Othman and Z.A.A. Karim, Compatibility of 3-D turning diffusers by means of varying area ratios and outlet-inlet configurations, ARPN Journal of Engineering and Applied Sciences 7(6) (2012) 708-713.

[2] N. Nordin, Z.A.A. Karim, S. Othman and V.R. Raghavan, Experimental Investigation of 2-D Turning Diffuser Performance by Varying Inflow Reynolds Number in 2nd International Conference on Mechanical, Automotive and Aerospace Engineering (ICMAAE 2013), Kuala Lumpur, (2013).

[3] R.W. Fox and S.J. Kline, Flow regime data and design methods for curved subsonic diffusers, J. Basic Eng. ASME 84 (1962) 303-312.

DOI: 10.1115/1.3657308

[4] C.J. Sagi and J.P. Johnson, The design and performance of two-dimensional, curved diffusers, J. Basic Eng. ASME 89 (1967) 715-731.

[5] G. Guohui and B.R. Saffa, Measurement and computational fluid dynamics prediction of diffuser pressure-loss coefficient, Applied Energy 54(2) (1996) 181-195.

DOI: 10.1016/0306-2619(95)00078-x

[6] B. Majumdar and D.P. Agrawal, Flow characteristics in a large area ratio curved diffuser, Proc. Instn. Mech. Engrs. 210 (1996) 65.

[7] E.G. Tulapurkara, A.B. Khoshnevis and J.L. Narasimhan, Wake boundary layer interaction subject to convex and concave curvatures and adverse pressure gradient, Exp. In Fluids 31 (2001) 697-707.

DOI: 10.1007/s003480100337

[8] C.K. Nguyen, T.D. Ngo, P.A. Mendis and J.C.K. Cheung, A flow analysis for a turning rapid diffuser using CFD, J. Wind Eng. 108 (2006) 749-752.

[9] T.P. Chong, P.F. Joseph and P.O.A.L. Davies, A parametric study of passive flow control for a short, high area ratio 90 deg curved diffuser, J. Fluids Eng. 130 (2008).

DOI: 10.1115/1.2969447

[10] W.A. El-Askary and M. Nasr, Performance of a bend diffuser system: Experimental and numerical studies, Computer & Fluids 38 (2009) 160-170.

DOI: 10.1016/j.compfluid.2008.01.003

[11] Y.C. Wang, J.C. Hsu and Y.C., Lee, Loss characteristics and flow rectification property of diffuser valves for micropump applications Int. J. of Heat and Mass Transfer 52 (2009) 328-336.

DOI: 10.1016/j.ijheatmasstransfer.2008.06.010

[12] N. Nordin, Z.A.A. Karim, S. Othman and V.R. Raghavan, Design & development of low subsonic wind tunnel for turning diffuser application, Advanced Material Research 614-615 (2013) 586-591.

DOI: 10.4028/www.scientific.net/amr.614-615.586

[13] N. Nordin, V. R. Raghavan, S. Othman and Z. A. A. Karim, Numerical investigation of turning diffuser performance by varying geometric and operating parameters, Applied Mechanics and Materials Journal 229-231 (2012) 2086-(2093).

DOI: 10.4028/www.scientific.net/amm.229-231.2086

[14] N. Nordin, S. Othman, V.R. Raghavan and Z.A.A. Karim, Verification of 3-D stereoscopic PIV operation and procedures, International Journal Engineering and Technology IJET/IJENS, 12(4) (2012) 19-26.

[15] N. Nordin, Z.A.A. Karim, S. Othman and V.R. Raghavan, Verification of fully developed flow entering diffuser and particle image velocimetry procedures, 3rd International Conference of Mechanical Engineering (ICME 2012), Batu Pahat, Malaysia: submitted to Applied Mechanics and Materials Journal (2012).

DOI: 10.4028/www.scientific.net/amm.465-466.1352