Accession Number:

ADA235507

Title:

Radial Mixing in Turbomachines

Descriptive Note:

Final rept. 1 Jul 1989-31 Jul 1990

Corporate Author:

VRIJE UNIV BRUSSELS (BELGIUM) DEPT OF FLUID MECHANICS

Personal Author(s):

Report Date:

1991-03-31

Pagination or Media Count:

195.0

Abstract:

A method for computing the effects of radial mixing in a turbomachinery blade row has been developed. The method fits in the framework of a quasi-3D flow computation and hence is applied in a corrective fashion to through flow distributions. The method takes into account both secondary flows and turbulent diffusion as possible sources of mixing. Secondary flow velocities determine the magnitude of the convection terms in the energy redistribution equation while a turbulent diffusion coefficient determines the magnitude of the diffusion terms. Secondary flows are computed by solving a Poisson equation for a secondary streamfunction on a transversal S3-plane, whereby the right-hand side axial vorticity is composed of different contributions, each associated to a particular flow region inviscid core flow, end-wall boundary layers, profile boundary layers and wakes. The turbulent mixing coefficient is estimated by a semi-empirical correlation. Secondary flow theory is applied to the VUB cascade testcase and comparisons are made between the computational results and the extensive experimental data available for this testcase. This comparison shows that the secondary flow computations yield reliable predictions of the secondary flow pattern, both qualitatively and quantitatively, taking into account the limitations of the model. However, the computations show that use of a uniform mixing coefficient has to be replaced by a more sophisticated approach -- using increased mixing levels in the end wall boundary layers.

Subject Categories:

  • Fluid Mechanics
  • Jet and Gas Turbine Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE