| 摘要 |
<p>A gas turbine engine (10) with a system (i) for cooling the turbine section and (ii) for providing tip clearance control between turbine blades and the shroud surrounding the turbine blades. The system includes a turbine section cooling sub-system which diverts a first cooling air flow received from the compressor section to a heat exchanger and then to the turbine section to cool components thereof. The first cooling air flow by-passes the combustor (15) and is cooled in the heat exchanger. The turbine section cooling subsystem has a first valve (1) arrangement which regulates the first cooling air flow. The system further includes a tip clearance control sub-system which supplies a second cooling air flow to an engine case to which the segments are mounted. The second cooling air flow regulates thermal expansion of the case and thereby controls the clearance between the shroud and the outer tips. The tip clearance control sub-system has a second valve (2) arrangement which regulates the second cooling air flow. The system further includes a closed-loop controller (K) which issues first and second demand signals to respectively the first and the second valve arrangements (1, 2). Each of the first and second demand signals are determined on the basis of: (i) a value of the first demand signal at a previous time step, and a measurement or estimate of turbine section component temperature, and (ii) a value of the second demand signal at a previous time step, and a measurement or estimate of tip clearance.
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