To optimize the efficiency of modern aero-gas turbine engines the turbine tip clearances must be tightly controlled so as to minimize leakage losses. In addition, the clearance control system must be able to respond with sufficient rapidity to engine thermal transients. One method of achieving turbine tipclearance control is to manipulate the turbine casing temperature, and thereby radial growth, by convective cooling. The consequent clearance control system represents a particularly complex thermo-mechanical design problem. The current experimental study aims to simulate the heat loads to which the internal surfaces of the casing are typically exposed and to characterize the radial and axial displacement of the free-body casing under varying external cooling conditions. Importantly, the newly commissioned test facility allows a realistic assessment of the casing cooling impact on dimensional control, and also the rapid characterization and comparison of different concepts. The test facility comprises a model of a high-pressure/intermediate-pressure * Address all correspondence to this author. turbine casing with generic impingement cooling manifolds. A radiant heater is mounted within the casing model such that a near-uniform heat flux condition can be established on the casing wall inner surface. Extensive surface mounted thermocouples are welded to the casing wall to monitor variations in metal temperature. Radial and axial displacement of the casing is monitored using laser triangulation and linear variable differential transformer sensors. Experiments have been conducted over a range of heat load conditions and with engine representative levels of casing cooling applied. Importantly, the new test facility allows for the characterization of the casing cooling system as a whole. NOMENCLATURED displacement. E axial expansion. l casing axial length. r HP casing radius. Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 05/29/2015 Terms of Use: http://asme.org/terms RDG reading. FSO full scale output.

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This paper describes the design and development of a major new facility capable of reproducing flow conditions for large civil aero engine turbine and compressor segment cavities. The facility reproduces in 3-D, typical secondary air system cruise temperatures, pressures and mass flows. The facility allows better understanding of the circumferential heat transfer effects of air system flows on turbine and compressor casings, as these have a significant influence on both steady-state and transient blade tip clearance behavior. Different air system architectural solutions are considered and 1-D transient air system modelling is used to design architecture to ensure that they meet tight performance requirements in terms of allowable pressure and temperature ripples when subject to fast switching of flows. An explanation of the design of the double-skin pressure vessel using 2-D axisymmetric thermo-mechanical analysis to understand the life-limiting features of the design is discussed. Finally we conclude the paper with some experimental results from rig commissioning and the use of these results in the determination of engine casing transients is discussed.

The transient heat transfer facility (THTF) was developed to test full-scale high pressure compressor and turbine casing air systems using gas turbine engine representative secondary air system conditions. Transient casing response together with blade and disk responses governs achievable tip clearances in both compressors and turbines. This paper investigates the use of air impingement as a means to speed up the casing response. The thermal growth of the casing was characterized by surface temperature rise over a given period to assess achievable dynamic response. The experimental setup resembles a typical aircraft engine with features that can lead to circumferential temperature nonuniformities, as evident from the experimental results. The experimental data were compared against numerical predictions from a conjugate heat transfer (CHT) model. The studies show the significance of analyzing the full annulus, at engine representative conditions and the benefit of an impingement array to potentially speed up casing response for future engines.