Numerical simulation of wet steam expansion in a supersonic low-pressure turbine cascade

摘要

This paper presents a numerical investigation of the flow structure of a supersonic wet steam expansion in a quasi-2-D,linear turbine cascade design,designed by General Electric.Stationary cascade tests are commonly employed in the late design stages to gain a better understanding of profile losses,with the obvious goal of improving the efficiency.The blade cascade studied here represents the tip section of the last stage of rotor blades of a low-pressure steam turbine.This section,entirely confined in the wet steam region,is also known to exhibit supersonic conditions at the outlet,and strong transonic velocities immediately downstream of the inlet.In order to “extend” and to “calibrate” the experimental tests,a series of numerical simulations of the aero-thermo fluiddynamic phenomena occurring in the test bench was performed with Ansys FLUENT(R).The steady RANS system for multiphase flows,under realistic conditions(turbulent compressible 2-phase flow),are solved coupled with a 2-phase Eulerian model,based on the classical nucleation theory corrected for non-isothermal effects.Results are reported and compared with existing numerical data.