A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion

Behnam Nikkhahi; Mehrzad Shams; Masoud Ziabasharhagh

Korean Journal of Chemical Engineering, Vol.27, No.6, 1646-1653, November, 2010

DOI10.1007/s11814-010-0268-6 Export Citation

A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion

Behnam Nikkhahi, Mehrzad Shams^†, and Masoud Ziabasharhagh

Faculty of Mech. Engineering, K.N.Toosi University of Technology, Tehran, Iran

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During transonic flow of steam in divergence nozzles, flow first supercools and then nucleates to become two-phase droplet flow. This phenomenon especially occurs in the last stages of steam turbines and affects performance. In this research, a numerical scheme for two-phase flow in nozzle passages is developed. An Eulerian-Eulerian reference frame is used for both phases. The shear stress transport turbulence model is used to model the Reynolds stresses appearing in the averaged Navier-Stokes equations. The homogeneous nucleation model is applied for the mass transfer in the transonic conditions. In this paper three nozzles with different rate of expansion are employed to be under study. Overall pressure ratio (static to total pressure) and droplet size are compared with the experimental data and good agreements are observed.

Keywords:Nucleation;Two-phase Flow;Nozzles;CFD;Eulerian-Eulerian

[References]

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[1] Bakhtar F, Zidi K, Proc. Inst. Mech. Eng., 203, 195 (1989)

[2] Bakhtar F, Zidi K, Proc. Inst. Mech. Eng., 204, 233 (1990)

[3] Gerber AG, ASME J. Fluids Eng., 124, 465 (2002)

[4] Gerber AG, Kermani M, Int. J. Heat Mass Transf., 47(10-11), 2217 (2004)

[5] Simpson DA, White AJ, International J. Heat and Fluid Flow, 26, 71 (2005)

[6] Equations of IAPWS-IF97, A summary by Bernhard Spang, Hamburg, Germany, at The Chemical Engineers’ Resource Page.

[7] IAPWS Equations for Transport Properties and, Surface Tension of Water and Steam, A summary by Bernhard Spang, Hamburg, Germany, at The Chemical Engineers’ Resource Page.

[8] McDonald JE, Am. J. Phys., (1962-1963), 30, 870

[9] Kermani MJ, Zayernouri M, Saffar-Avval M, Generalization of an analytical tow-phase steam flow calculator to high-pressure cases, Department of Mechanical Engineering, Amir Kabir University of Technology, Tehran, Iran.

[10] IAPWS Equations for Transport Properties and, Surface Tension of Water and Steam, A summary by Bernhard Spang, Hamburg, Germany, at The Chemical Engineers’ Resource Page.

[11] ANSYS CFX 11-Solver Theory Guide, Discretization and Solution Theory, 227 (2006)

[12] Teymourtash AR, Mahpeykar MR, A Balde to Balde Inviscid Transonic Flow Analysis of Nucleating Steam in a Turbine Cascade by the Jameson’s Time - Marching Scheme Using Body Fitted Grid, Ferdosi University (2006)