The Whole-Engine Model for Clearance Evaluation

Abstract

The evaluation of the blading clearance at the design stage is important for heavy duty gas turbine efficiency. The minimum clearance value at base load is limited by the pinch point clearance during startup and/or shutdown. Therefore, transient analysis is necessary for different operating conditions. 3D transient analysis of a whole engine is labor-intensive; however 2D axisymmetric analysis does not allow consideration of different 3D effects (e.g. twisting, bending, ovality, rotor alignment). In order to overcome these cost and time limitations, the combination of 2D, axisymmetric, whole-engine model results and the scaled deflections caused by different 3D effects is used for the axial and radial clearance engineering assessment during engine operation. The basic rotor and stator closures are taken from the transient analysis using a 2D finite element (FE) model composed of axisymmetric solid and plane stress elements. To take into account 3D effects of airfoil twisting and bending, the 3D FE displacements of the blade are included in the clearance evaluation process. The relative displacements of airfoil tip and reference point at the blade or vane hub are taken from 3D steady-state FE analyses. Then the steady-state displacements of the airfoils are scaled for transient conditions using the proposed technique. Different 3D rotor / stator effects (cold-build clearances and their tolerances, rotor position with respect to stator after assembly, casing bending, deformations of compressor and turbine vane carrier inducing of casing ovalization, exhaust gas housing movements, movements of the rotor in bearings and CVC and TVC support, etc.) are also included as a contributor to the clearances. The results of the calculations are analyzed and compared with good agreements to the clearances measured in engine testing under real operation conditions. The proposed methodology allows assessing the operating clearances between the stator and rotor during the design phase. Optimization of the running clearance is one key measure to upgrade and improve the engine performance during operating experience.

Multi-fidelity Kriging-assisted structural optimization of whole engine models employing medial meshes

“…The output sets are post-processed to give maximum local radial displacement values which are then used as design constraints in Section 4. This maximum local radial displacement value is an approximation of the maximum pinch point metric for tip clearance studies of gas turbine engine casings (Arkhipov et al 2009). The calculation first involves the fitting of a least-squares circle to the deformed points in each output set on the y-z plane.…”

“…Due to advances in computational power and simulation efficiency, whole engine models (WEMs) have become a staple tool in the design process of gas turbine engines in industry (Voutchkov et al 2006;Arkhipov et al 2009;Toal et al 2014). Analyzing WEMs allows engineers to capture both the physics of inter-component interactions and also emergent behaviour that would otherwise be lost if the analysis was done on each component in isolation.…”

An Introduction Into the Clearance Management of Ansaldo GT36 From Development to Validation

“…As early as the conceptual design phase a whole engine model (WEM) for transient clearance analyses was set-up. It follows the well-established design principals as outlined in [3] and [4].…”

Multifidelity Multidisciplinary Whole-Engine Thermomechanical Design Optimization

“…As discussed by Benito et al [2] and Arkhipov et al [3], whole engine transient thermo-mechanical (WETTM) analyzes can be considerably expensive to perform. In order to make the application of such simulations feasible within a design optimization, either the simulation needs to be as cheap as possible (including both the runtime and the setup time) or the number of such simulations performed needs to be minimized.…”

“…As demonstrated throughout the literature, [14] the clearance between the casing and the tip of a compressor or turbine blade has a considerable impact on the fuel consumption of an engine. While eorts have been made in the past to control the impact of these clearances through changes in casing shape or topology, [1,5] previous studies have employed either simplied shell models of the whole engine in a mechanical analysis [5] or a combination of 2D axisymmetric transient whole engine analysis and 3D blading and rotor/stator deformations [3]. Only using a fully transient thermomechanical simulation of the whole engine can tip clearances be accurately predicted [2,3].…”