Probabilistic CFD Analysis of High Pressure Turbine Blades Considering Real Geometric Effects

Abstract

This paper addresses the consideration of variability due to manufacturing and abrasion of high pressure turbine (HPT) blades through probabilistic CFD investigations. Currently, the influences of those effects onto relevant aerodynamic quantities are covered by safety factors and conservative assumptions. The probabilistic investigation on the other hand, based on realistic input parameters, will enable designers to possibly reduce safety factors and provide the foundation for more robust blade designs. In order to establish a sound statistical database, 500 new and used HPT blades were digitised with an optical 3D scanning system in order to record the outer geometric variability. As described in the work of Heinze et al. [1], the measured point clouds are parameterized using classical profile parameters and a process to rebuild various blade geometries has been developed. In terms of probabilistic investigations, in our case by applying sampling-based methods, a large number of 3D CFD simulations for a 1.5 HPT stage have been conducted using probabilistic blade geometries, followed by a sensitivity analysis and a detailed investigation of the probabilistic system behaviour. For visualization of possible correlations, the technique of Statistics on Passage (SoP) was chosen, as described in [2].

Robust Turbine Blade Optimization in the Face of Real Geometric Variations

“…where subscript o indicates the model built with one omitted parameter [2]. Figure 15 presents both the rank correlation coefficient and COI computed with 100 samples and the defeatured CFD model.…”

“…Several relevant UQ studies describe the effects of turbine blade deviations based on actual manufacturing process-related data [1,2,3,4,9]. Notably, a previous version of the correlation-based parameterization method also used in this paper was used as part of a UQ study [2]. The statistical basis consisted of 500 digitized new and used high-pressure (HP) turbine blades.…”

“…For example, deviations can stem from manufacturing variations, corrosion, foreign object damage, creep, fatigue and operating condition abnormalities such as hot streaks. In the literature, it is well-known that even minimal perturbations in certain areas, whatever the cause, can have substantial detrimental effects on blade performance [1,2,3,4]. For turbines in particular, this concerns the capacity, pressure losses, blade temperatures and as a consequence thereof blade life.…”

“…The contribution of this paper relative to prior work is the incorporation of a previously developed parameterization method [2] and UQ workflow [6] into a coherent RDO workflow for turbine blades, which, to the best of our knowledge, is the first such heuristic to incorporate real variations of the entire blade shape. It is shown that artificially generated blades for UQ can recreate the stochastic performance of real scans and that the optimization effectively produces robust turbine blade designs.…”

Influence of combined compressor and turbine deterioration on the overall performance of a jet engine using RANS simulation and pseudo bond graph approach

“…However, the modified compressor and turbine aerodynamics with further deteriorations such as a reduced leading/trailing edge, max. thickness and the resulting stagger angle are investigated in serval studies (Scharfenstein et al, 2013;Reitz et al, 2014;Ernst et al, 2016). These results exhibit that the positions of the characteristic curve (mass flow, pressure ratio and efficiency) are qualitatively and quantitatively dependents on the type of deterioration.…”