Project Title:
A New Approach to the Prediction of Transition in Gas Turbines
94-1 02.01 2600 AMOUNT REQUESTED $
A New Approach to the Prediction of Transition in Gas Turbines
Abstract:
The objective of this proposal is to develop advanced analysis
software based on three-dimensional computational fluid dynamic
(CFD) methods to support the design and optimization of gas
turbines.
In fact, due to the process of transition from a laminar to a
turbulent boundary layer on the blade, great uncertainty presently
exists in predicting convective heat transfer rates from the blade.
Current CFD techniques using inadequate transition criteria, based
on local pressure gradient and boundary-layer thickness parameters,
fail to address the fact that the competing effects of high
external stream turbulence and severe streamwise acceleration can
lead to the boundary layer being in an intermediate state between
laminar and turbulent over much of the blade surface. We propose to
use a well-validated procedure, based on state-of-the-art
turbulence modeling, for predicting momentum and heat transfer
rates in boundary layers with especial reference to the transition
from laminar to turbulent (or semi-turbulent) flow induced by high
levels of external stream turbulence.
Phase I will focus on demonstrating the innovative technology and
assessing our turbulence models in the design of gas turbines. This
will be accomplished by modeling the development of a boundary
layer on the blade surface under the influence of various free
stream turbulence energy levels. The state-of-the-art in turbulence
modeling will include the use of low-Reynolds number RNG-based
eddy-viscosity models, non-linear k-e, explicit algebraic stress
models and other alternatives to a full low-Re second-moment
closure.
Phase II will focus on improving and enhancing physical models as
deemed necessary in Phase I, as well as employing the use of
sophisticated full Reynolds-stress closures that incorporate
sufficiently general sub-models of the different processes at work
for there to be good prospects of it predicting transition with
reasonable accuracy.
The proposed work employs many basic features that will find wide
usage in industry. The code developed may be used for modeling
blade-cascade flows over a wide range of operating conditions and
will be a valuable tool for the design and optimization of gas
turbines.
KEY WORDS
Fluent Inc.
10 Cavendish Ct.
Lebanon, NH 03766