A Numerical Smith Diagram Revision for Modern Low Pressure Turbine Profiles
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Abstract
Smith diagram is historically one of the standard tools used
for turbine design, especially in concept design phase (CD) and
for assessment/comparison of turbine configurations. For each
turbomachinery stage, this graph provides a relation among
stage loading factor (y), flow coefficient (f) and aerodynamic
performance (). However, various essential inputs such as
stage reactions (R), aspect ratios (AR) or Reynolds numbers
(Re), or outputs like flow deflections (d), profile weights and
stresses are not directly taken into account.
In the work here presented, traditional loss correlation
models (Craig & Cox (C&C) and Ainley & Mathieson, Dunham
& Came, Kacker & Okapuu (AMDCKO)), are used to evaluate
stage performance and then to derive a more complete vision of
key parameters. Starting from a representative turbine
configuration, once some main characteristic boundary
conditions (BC) have been defined, few parameters are changed
in order to obtain a stage operating in a specific region of the
Smith diagram. By this way, it has been possible to compare
experimental data from original Smith with computational
results obtained with such approach. Moreover, additional
details previously missing (both aerodynamic and mechanical)
have been obtained and optimal design considerations have
been investigated under a multidisciplinary point of view.
In addiction, by means of dedicated tools, blade geometries
have been prepared for some of these configurations. Some
preliminary CFD 3D analyses have then been run to improve
specific understandings.
This research leads to extend Smith diagram with many
other important information for turbine module design and to
numerically revise the diagram itself, adjusting it with data
coming from modern high performance profile’s analyses