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A Gas Turbine Compressor Simulation Model for Inclusion of Active Control Strategies

The need for a wider operability range of modern compressors for 
gas turbine applications is the "prime mover" for a large research 
effort that is nowadays undertaken in many international laboratories, 
organisations, companies and universities. This effort is both 
experimental and computational. The overall behaviour of a gas 
turbine compressor outside its stability range has been understood and 
can be modelled using a simplified lumped parameters approach 
(Greitzer, 1976, Baghdadi ct al., 1982). Many detailed experimental 
analysis are nowadays focused on stall inception (Day et al, 1999, 
Camp-Day 1998, Spakovsky et al., 1999) to understand the fluid- 
dynamic mechanism of formation and to be able to improve its 
computational modelling. On the other hand the computational models 
for the analysis of a multistage compressor in steady flow (through- 
flow or 3D Navier-Stokes) are not directly applicable to unsteady 
Oransient or dynamic) flows because they are either inappropriate 
(standard through-flow) or they require an excessive computational 
effort (3D Navier-St0kes). The most simplified approach is the zero 
dimensional lumped parameter technique that considers each 
component Of the compression system as a node and by wriling (he 
balance for mass flow, momentum and energy it results in a set Of 
differential equations to be solved with respect to time (Greitzer, 
1976, Massardo ct al. 1989, Botros, 1994). 
The one dilnensional model for the analysis Of the unsteady flow in a 
compression system can be a good compromise between the accuracy 
in capturing the main system performances and the computational 
effort. This approach introduces the conservation equations 
(continuity, momentum and energy) for a continuum and, after a 
domain discretization, are integrated using a time-marching technique; 
the effect of blades, mass bleeds, friction etc.... are introduced as 
external body forces. This technique has been considered and a time- 
marching technique, previously developed for 21)/3D turbomachinery 
flows (Cravero. 1995), has been converted in ID form with the 
insertion of the appropriate external forces to model the dynamic of 
the compression system. The ID lime-marching approach is preferred 
over the lumped parameter technique, because it allows the analysis