ANALYSIS OF GAS TURBINE ROTATING CAVITIES: ESTIMATION OF ROTOR DISK PUMPED MASS FLOW RATE

摘要

The dependable design of secondary air system is one of the main tasks for the safety, reliability and performance of gas turbine engines. To meet the increasing demands of gas turbine design, improved tools in prediction of the secondary air system behaviour over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore its analysis is not carried out using a complete CFD approach. Usually, these predictions are performed using codes, based on simplified approach which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and little calculation time. Generally the available simplified commercial packages allow to correctly solve only some of the components of a real air system and often the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design-tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for a steady one-dimensional axysimmetric flow using experimental correlations both to incorporate flow phenomena caused by multidimensional effects, like heat transfer and flow field losses, and to evaluate the circumferential component of velocity. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow both with a Batchelor and/or Stewartson flow structures. Several studies have been carried out by the authors to develop suitable correlations for the discs friction coefficients and for co-rotation factor evaluation. The results of these analyses are available in the literature. In the present paper the authors develop, using CFD tools, reliable correlation for rotor disk pumped mass flow rate and provide a full ID-code validation comparing, due to a lack of experimental data, the in-house design code predictions with those evaluated by CFD.