Experimental and Numerical Investigation of Optimized Blade Tip Shapes: Part I — Turbine Rainbow Rotor Testing and CFD Methods

Cernat, Bogdan C.; Pátý, Marek; Maesschalck, C. De; Lavagnoli, Sergio

doi:10.1115/gt2018-76564

Cited by 5 publications

(1 citation statement)

References 50 publications

(41 reference statements)

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“…Maesschalck [24][25][26] apllied the carved and squealer-like tip to promote the aerodynamic thermal performance and proposed the optimization strategy. Cernat 27,28 researched the aerothermal performance of a multi-cavity squealer-like tip and a contoured shape tip by the detailed experimental and the numerical studies. The result indicated that the two tip structures had the greater impact on the static pressure coefficient (C p ) after 50%C ax .…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study of novel tip configurations in a turbine cascade

Jin

Song

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part A:

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Two novel tip modeling methods are proposed in this paper. One novel tip is established by the mathematical method and the other is generated by the B-spline surface. And the genetic algorithm, the orthogonal design and the Kriging model are applied to optimize two kinds of novel tips numerically. The optimal mathematical tip and the optimal B-spline tip are acquired respectively. The aerodynamic tests were investigated at the wind tunnel test section, including the flat tip, the squealer tip, the optimal mathematical tip and the optimal B-spline tip. The static pressure distributions on the casing and the blade surface were measured by the pressure taps. Meanwhile, the secondary flow and the loss were obtained by the five-hole probe at the exit section. A comparison of the simulation analysis results with the experimental results shows good agreement. Compared with the flat tip, the measured loss on the squealer tip, the optimal mathematical tip and the optimal B-spline tip is decreased by 7.2%, 10.5% and 12.6% respectively.

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Section: Introductionmentioning

confidence: 99%

Experimental and numerical study of novel tip configurations in a turbine cascade

Jin

Song

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part A:

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A Novel Vortex Identification Technique Applied to the 3D Flow Field of a High-Pressure Turbine

Pátý

Lavagnoli

2019

Volume 2B: Turbomachinery

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The efficiency of modern axial turbomachinery is strongly driven by the secondary flows within the vane or blade passages. The secondary flows are characterized by a complex pattern of vortical structures that origin, interact and dissipate along the turbine gas path. The endwall flows are responsible for the generation of a significant part of the overall turbine loss because of the dissipation of secondary kinetic energy and mixing-out of non-uniform momentum flows. The understanding and analysis of secondary flows requires a reliable vortex identification technique to predict and analyse the impact of specific turbine designs on the turbine performance. However, literature shows a remarkable lack of general methods to detect vortices and to determine the location of their cores and to quantify their strength. This paper presents a novel technique for the identification of vortical structures in a general 3D flow field. The method operates on the local flow field and it is based on a triple decomposition of motion proposed by Kolář. In contrast to a decomposition of velocity gradient into the strain and vorticity tensors, this method considers a third, pure shear component. The subtraction of the pure shear tensor from the velocity gradient remedies the inherent flaw of vorticity-based techniques which cannot distinguish between rigid rotation and shear. The triple decomposition of motion serves to obtain a 3D field of residual vorticity whose magnitude is used to define vortex regions. The present method allows to locate automatically the core of each vortex, quantify its strength and determine the vortex bounding surface. The output may be used to visualize the turbine vortical structures for the purpose of interpreting the complex three-dimensional viscous flow field, as well as to highlight any case-to-case variations by quantifying the vortex strength and location. The vortex identification method is applied to a high-pressure turbine with three optimized blade tip geometries. The 3D flow-field is obtained by CFD computations performed with Numeca FINE/Open. The computational model uses steady-state RANS equations closed by the Spalart-Allmaras turbulence model. Although developed for turbomachinery applications, the vortex identification method proposed in this work is of general applicability to any three-dimensional flow-field.

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Aerothermal Optimization of Turbine Squealer Tip Geometries With Arbitrary Cooling Injection

Maesschalck

Andreoli

Paniagua

et al. 2019

Volume 5B: Heat Transfer

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The optimization of the turbine rotor tip geometry remains a vital opportunity to create more efficient and durable engines. Balancing the aerodynamic and thermal aspects, while maintaining the mechanical integrity is key to reshape one of the most vulnerable and life determining parts of the entire turbine. The ever-increasing turbine gas temperatures, combined with the difficulty of cooling the tip and the aerodynamically penalizing nature of the overtip leakage vortex, makes the design of the tip a truly multi-disciplinary challenge. While many earlier efforts focused on uncooled geometries, or studied the aerothermal impact with a fixed cooling configuration, the current paper presents the outcome of a multi-objective optimization where both the squealer rim geometry as well as the cooling injection pattern was allowed to vary simultaneously. This study explores a significantly wider design space, seeking a further synergistic aerothermal benefit through the combination of a quasi-fully arbitrary cooling arrangement, with mutating squealer rim structures. Specifically, the current manuscript presents the results of over 330 cooled and uncooled squealer tip geometries. The high pressure turbine tip was automatically altered using a novel parametrization strategy adopting a maximum of 40 design variables to vary the squealer rim structures, as well as the size and location of the various cooling holes. The aerodynamic and thermal characteristics of every design were evaluated through Reynolds-Averaged Navier-Stokes CFD simulations with the k-ω SST model for the turbulence closure, adopting an unstructured hexahedral grid typically containing more than 8 million cells. A multi-objective differential evolution algorithm was used to obtain a Pareto front of designs which maximize the aerodynamic efficiency, while minimizing the overtip thermal loads. Eventually, a detailed investigation and robustness study was performed on a set of prime squealer geometries, to further investigate the aerodynamic flow topology, and the effect of various cooling injection schemes on the heat transfer patterns.

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Experimental and Numerical Investigation of Optimized Blade Tip Shapes: Part I — Turbine Rainbow Rotor Testing and CFD Methods

Cited by 5 publications

References 50 publications

Experimental and numerical study of novel tip configurations in a turbine cascade

Experimental and numerical study of novel tip configurations in a turbine cascade

A Novel Vortex Identification Technique Applied to the 3D Flow Field of a High-Pressure Turbine

Aerothermal Optimization of Turbine Squealer Tip Geometries With Arbitrary Cooling Injection

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