Use of computational fluid dynamics (CFD) to model the complex, 3D disk cavity flow and heat transfer in conjunction with an industrial finite element analysis (FEA) of turbine disk thermomechanical response during a full transient cycle is demonstrated. The FEA and CFD solutions were coupled using a previously proposed efficient coupling procedure. This iterates between FEA and CFD calculations at each time step of the transient solution to ensure consistency of temperature and heat flux on the appropriate component surfaces. The FEA model is a 2D representation of high pressure and intermediate pressure (IP) turbine disks with surrounding structures. The front IP disk cavity flow is calculated using 45 deg sector CFD models with up to 2.8 million mesh cells. Three CFD models were initially defined for idle, maximum take-off, and cruise conditions, and these are updated by the automatic coupling procedure through the 13,000 s full transient cycle from stand-still to idle, maximum take-off, and cruise conditions. The obtained disk temperatures and displacements are compared with an earlier standalone FEA model that used established methods for convective heat transfer modeling. It was demonstrated that the coupling could be completed using a computer cluster with 60 cores within about 2 weeks. This turn around time is considered fast enough to meet design phase requirements, and in validation, it also compares favorably to that required to hand-match a FEA model to engine test data, which is typically several months. [DOI: 10.1115/1.4003242

A combined CFD and FE method, which could be applied to a wide range of internal air system rotor-stator cavities and which overcomes the disadvantages of many non-coupled approaches, is presented. It is used to predict windage and heat transfer in the HP compressor rear cone outer cavity of a service aeroengine. From the CFD it is shown that rotor wall torque, and hence windage, decreases as cavity throughflow increases, and that the data from several engine cavities can be reduced to a single characteristic of windage versus mass flow. Stator wall torque is also presented. A comparison with engine thermocouple data shows that further development of the modelling is required before engine testing could be replaced.

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.

In an engine design process, thermo-mechanical analyses of compressor drums and casings are undertaken, to predict component temperatures and displacements, which are ultimately used for material selection, blade clearance control and lifing of components. The thermal boundary conditions are sourced from a small number of standard flow field and heat transfer solutions, leading to a reliance on engine thermocouple tests to provide calibration factors on the boundary conditions, which with changes in inlet flows and cavity geometry from the tested arrangements are unproven, limiting the ability to readacross the test information into new designs. Given that the thermal boundary conditions in compressor drum and casing components are largely driven by complex flow physics, in the absence of suitable test information, CFD methods can be used to provide boundary specification of the thermo-mechanical problem, incorporating the complex physics involved. Without the insight of the flow field solution in complex flow regions, specification of the boundary conditions is rather subjective and mostly based on intuition. This study shows the use of CFD to provide the boundary conditions for the rotor-stator cavity at the front of an IP compressor drum. The CFD is run adiabatically and through a set of unit heat transfer cases on separate sections of the cavity wall, at key points in the flight cycle. The analyses provide appropriately characterized thermal boundary conditions (specifically heat transfer coefficients and adiabatic wall temperatures) that are transferred into the thermo-mechanical model, which can then be run through a wide range of cycles without the need for further CFD calculations.

When a gas turbine is shut down it cools asymmetrically due to natural convection. After some time, a thermal gradient develops across the rotor drum as the top section cools slower than the bottom. This induces a thermal stress that causes the shaft to deflect — a phenomenon known as rotor or thermal bow. In some cases, this can lead to compressor tip rubs. All engines are affected by rotor bow to some degree. However, the mechanisms of natural convective heat transfer and impact of design features on rotor bow is not well understood; thus, the issue is not identified until late in the design stage, hampering an engines development. A novel experimental technique and facility has been developed that allows for accurate, detailed measurements of natural convective heat transfer in a gas turbine annulus to be made. The apparatus has the capacity to test circumferential and axial variations in temperature distribution, in addition to an isothermal wall boundary. An IR camera looking directly at the rotor surface is used to provide high-resolution heat transfer measurements. The test piece for this study consisted of a cylinder section and a conical section. Results from the isothermal cylinder test cases agreed quite well with previously published data, which gives confidence to the method that has been employed. The addition of a conical section had a profound effect on the results; however, more work is required before a method can be developed which will accurately predict the heat transfer coefficients based on initial temperature distribution. A 2D concentric cylinder methodology has also been developed that gives results in strong agreement with previously published data. Going forward, this new facility and the CFD method will be further developed to help quantify the effect of various design features on the natural convective heat transfer performance of a large civil gas turbine.