Session: 32-08 Fan & Propulsor Design

Paper Number: 103871

103871 - Part Ii: Validation and Verification of Cfd Analysis for Nasa Sdt Transonic Fan Stage Coupled With Nacelle 

The Low Pressure Turbine (LPT) commonly used in both commercial and military engines is generally experiencing low Reynolds numbers at high altitude cruise condition.  Understanding the complex flow physics in an LPT stage is critical in providing adequate work output while maintaining target efficiency at low Reynolds number situations.

 

With the complex laminar to turbulent transition flow physics in mind, the high lift LPT design requires an understanding of the turbulent transition response to design and operating conditions which is not currently met with existing design methodologies.  The RANS based turbulence models like k – ω and SST, are not able to provide meaningful transition analysis. 

 

The focus of this paper is to understand the LES time-step size requirements needed for Reynolds’ Lapse rate estimation an LPT cascade.  Multiple controlled numerical experiments were executed on 4 sets of LPT cascade geometries.  Findings include that time step size needs to be small to promote the creation of 3D eddies and that the time step size used for the Dual-Time Stepping method need to be smaller than the Convection time step size (ΔTc )  to provide consistent Pt loss estimation between simulations using various value of time step size. 

 

The analysis results are verified against experimental data to determine the appropriate timestep size for LPT cascade LES analysis, so that new novel geometries can be evaluated prior to build and test.

Presenting Author: Daryl Y. Lee ADS CFD Inc

Presenting Author Biography: Daryl Lee is a senior CFD engineer from ADS CFD Inc. He holds an MS in mechanical engineering from University of California Davis.

Authors:

Daryl Y. Lee ADS CFD Inc
Gregorio Robles Vega ADS CFD Inc
Michael Ni ADS CFD Inc.
Ron Ho Ni ADS CFD Inc