http://yetl.yabesh.ir/yetl1/handle/yetl/19061 Sat, 04 Apr 2026 07:04:00 GMT 2026-04-04T07:04:00Z http://localhost:80/yetl1/bitstream/id/184260/ http://yetl.yabesh.ir/yetl1/handle/yetl/19061 http://yetl.yabesh.ir/yetl1/handle/yetl/4311046 Control of Three-Dimensional Corner Separation Flow in a Highly Loaded Compressor Cascade via Dynamic Surface Deformation Ren, Xuyang; Wang, Mingyang; Yao, Lipan; Huang, Enliang; Lu, Xingen When the Reynolds (Re) number decreases below the critical value, the intensified turbulent mixing in the corner region rapidly deteriorates the performance of compressors, including efficiency and stability. However, multiscale vortices and transition processes at low Re lead to extremely complex corner flow, and it is difficult in loss control. This article explores the possibility of dynamic surface deformation (DSD) to reduce the loss in the corner region of a highly loaded compressor cascade at Re = 1.8 × 105 and 9.3 × 104. Results show that the dynamics of flapping spanwise vortex (FSV) induced by DSD are directly related to the loss control. At a high DSD oscillation frequency, FSV is unstable and rises to a higher spanwise height, which promotes the transition in the mid-span and reduces the local viscous dissipation. However, it increases the near-endwall viscous dissipation. In contrast, FSV under a low-frequency DSD inhibits transverse flow and radial migration of vortices, thus reducing the near-endwall viscous dissipation. For the single-frequency DSD, the optimal oscillation frequency of DSD matches well with the concentrated shedding vortex (CSV) characteristic frequency, reducing the viscous dissipation by 33.4%. A multifrequency DSD, superimposing the characteristic frequencies of Kelvin–Helmholtz (K–H) vortex and CSV, is superior to single-frequency DSD in terms of loss reduction, and the overall viscous dissipation is 48.6% lower than that of the uncontrolled case. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311046 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4311019 The Impact of Manufacturing Variations on the Aerothermal Performance of High-Pressure Turbine Blade Shrouds Hulhoven, Bram; Coull, John D.; Jackson, Dougal; Atkins, Nicholas R. High-pressure turbine blade (HPTB) shrouds suffer manufacturing variations in both platform alignment and inter-platform gap width. Compared to hub endwalls, the aerothermal effects of shroud platform steps and gaps has had little attention, which introduces uncertainty in the sentencing of such manufacturing variations. This article presents a shroud step sentencing correlation developed using a parametric quasi-2D (Q2D) model of a shroud endwall step. The use of a Q2D model follows from the study of a 3D steady Reynolds-averaged Navier–Stokes (RANS) simulation matrix of engine-representative platform steps and gap widths, based on a sample of scanned HPTB castings and finished parts. This study showed that the aftchord shroud step flow is Q2D and resembles canonical step flow with enhanced heat transfer at the reattachment point. The shroud step sentencing correlation is tested on the platform steps in the simulation matrix giving prediction errors below 20% for the majority of cases. Finally, the correlation is tuned using experimental data to mitigate the uncertainty associated with RANS simulations of separated flows. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311019 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4311004 Gradient-Free Aerodynamic Optimization With Structural Constraints and Surge Line Control for Radial Compressor Stage Schaffrath, Robert; Nicke, Eberhard; Forsthofer, Nicolai; Kunc, Oliver; Voß, Christian The concept and design of high-temperature heat pumps (HTHP) including their components for specific temperature needs is a time-consuming and interdisciplinary task. Especially, the design of compressor geometries have a big impact on the overall performance and the initial costs of the system. For this reason, in this work, an automated aerodynamic gradient-free optimization including structural constraints for the geometry of a radial compressor impeller blade as well as diffusor vane geometry for water steam, that is applied in a reverse Rankine cycle-based HTHP, is presented. The objective of the optimization is the isentropic efficiency in the aerodynamic design point (ADP) of the compressor. The requirements for the cycle simulation of the whole HTHP system and structural needs are satisfied by constraints for pressure ratio, mass flowrate, and limits for stresses in the blade and disk geometry. The optimization method is based on evolutionary algorithms and stochastical surrogate models. Additionally, a highly throttled operating point is regarded to achieve an acceptable distance to the surge line. These types of optimization problems are often characterized by many unconverged iterations due to unstable computational fluid dynamic (CFD) simulations. To encounter this, a study of the optimization process with different surrogate models is presented. The results are discussed with respect to convergence history as well as objective and constraint improvement. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4311004 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310997 Multistage Turbomachinery Optimization for High-Temperature Heat Pumps With the Reverse Rankine Cycle Schaffrath, Robert; Stathopoulos, Panagiotis; Schmitz, Andreas; Nicke, Eberhard The electrification of process heat generation will be a key to achieving carbon neutrality in the coming decades. One of the most promising approaches is to replace conventional heat supply systems with high-temperature heat pumps (HTHPs). A promising heat pump concept is based on the reverse Rankine cycle that uses water as its working fluid. By using turbomachinery for the compression process in this cycle, the performance of the HTHP can be increased compared to the volumetric displacement systems, like screw or piston compressors. Although the design of the compressor geometry can be done sequentially in relation to the HTHP cycle design, better results can be obtained by an approach that integrates turbomachinery and the thermodynamic cycle design. Against this background, an automated optimization method for a reverse Rankine HTHP with two radial turbo-compressors in series is presented. In contrast to the current state of the art, the presented novel optimization approach uses 3D computational fluid dynamics data to calculate the compressor’s performance. Furthermore, the integration of low-fidelity compressor specific reduced-order models are used to accelerate the gradient-free optimization process by a CO-Kriging surrogate model. The advantages of the novel approach are justified by comparing the numerical effort and the final values of the optimization objectives. Wed, 01 Jan 2025 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4310997 2025-01-01T00:00:00Z