Investigation of Nonaxisymmetric Endwall Contouring and Three-Dimensional Airfoil Design in a 1.5 Stage Axial Turbine—Part II: Experimental Validation

Niewoehner, Jens; Poehler, Thorsten; Jeschke, Peter; Guendogdu, Yavuz

doi:10.1115/1.4029477

Cited by 16 publications

(6 citation statements)

References 4 publications

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“…Since the rotor has no shroud and the casing is cylindrical, this improvement must result from a homogenization of the stator outflow, resulting in an improved radial incidence distribution at the rotor inlet. Such a homogenization was in fact reported in previous measurements of this F3D configuration by Niewoehner et al (2015). Above 50% channel height, the purge flow has no effect on the flow, leading to basically congruent curves in both configurations.…”

Section: Numerical Validationsupporting

confidence: 84%

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Aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage axial turbine with nonaxisymmetric end wall contouring

Schäflein

Janssen

Brandies

et al. 2023

J. Glob. Power Propuls. Soc.

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This paper presents an investigation of the aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage turbine with non-axisymmetric end walls and a bowed stator using experimental flow measurements and unsteady RANS simulations. The study focuses on the secondary vortex structures formed in the rotor passages of the 1.5-stage axial turbine rig. Through performance map measurements, it was found that the efficiency gain of the non-axisymmetric configuration is partially eliminated by the injection of purge flow. Numerical investigations, which are supported by detailed flow measurements with five-hole probes and hot-wire probes, revealed that the injection of purge air flow intensifies vortex structures near the hub, thereby generating additional losses. These resulting vortex structures are highly similar both in the axisymmetric baseline and the non-axisymmetric configuration and are the result of jet-like vortices emerging from the cavity. From these findings, it can be concluded that the non-axisymmetric contour and the bowed stator no longer provides any efficiency benefit near the hub. Only the near the casing, where the flow is not affected by the purge flow, the optimized configuration continues to improve the efficiency of the rig by homogenizing the stator outflow and thus reducing the secondary flow structures in the rotor passages.

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Section: Numerical Validationsupporting

confidence: 84%

“…This end wall optimization was combined with a bowed first stator. Experimental validations by Niewoehner et al (2015) showed that these design choices helped improve the efficiency of the rig by 0.59%.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage axial turbine with nonaxisymmetric end wall contouring

Schäflein

Janssen

Brandies

et al. 2023

J. Glob. Power Propuls. Soc.

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“…Germain et al 16 and Schu¨pbach et al 17 designed NAEP for a turbine by using an automatic numerical optimization method, which resulted in reduced secondary flow and an improvement of stage efficiency by 1% AE 0.4%. Poehler et al 18 and Niewoehner et al 19 carried out an investigation of NAEP separately and its combination with bowed blading in a 1.5-stage axial turbine. Significant increase in efficiency for both configurations was observed, and the designs were beneficial under off-design conditions.…”

Section: Introductionmentioning

confidence: 99%

“…18 and Niewoehner et al. 19 carried out an investigation of NAEP separately and its combination with bowed blading in a 1.5-stage axial turbine. Significant increase in efficiency for both configurations was observed, and the designs were beneficial under off-design conditions.…”

Section: Introductionmentioning

confidence: 99%

Flow physics of highly loaded tandem compressor cascade with non-axisymmetric endwall profiling

Cao

Guo

Song

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part A:

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Tandem configuration is an effective methodology to reduce flow separation on compressor blade suction surface and to improve blade loading. However, in modern highly loaded cases, corner separation remains as its single blade counterpart. In this study, non-axisymmetric endwall profiling (NAEP) was utilized in a highly loaded tandem cascade (diffusion factor D = 0.69), aiming at reducing its severe corner separation and revealing the unique flow mechanism while NAEP is utilized in tandem cascade. NAEP was designed in both forward (F) blade and rare (R) blade separately, and was investigated numerically in tandem environment. Results show that, NAEP in F blade passage can effectively eliminate the corner separation and reduce loss generation, whereas NAEP in R blade passage has no positive effect on corner separation and even promotes loss production. The optimal NAEP approximately removes the corner separation completely, with loss coefficient reducing by as much as 37.8%. The optimal NAEP for the tandem cascade features optimal axial location at the origin of corner separation. There is an optimal NAEP height (0.02 of blade height), under which NAEP can achieve pretty good control effect while the peak of NAEP varies in a large axial location range. In the tandem configuration, it is found that NAEP transfers blade loading from R blade to F blade; the static pressure increases significantly for the entire cascade, but the static pressure distribution of F blade does not exhibit as the design intent of NAEP. In addition, it is interesting to find that the flow turning near endwall reduces after endwall profiling, which is unique in tandem cascade and is contrast to the view on conventional configuration. On the contrary, NAEP in R blade has no influence on the corner separation of the tandem cascade; due to the decrement of cross-passage pressure gradient for R blade, the flow overturning near endwall reduces.

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“…15 and Niewoehner et al. 16 investigated non-axisymmetric endwall profiling and 3D airfoil design in a 1.5-stage axial turbine.…”

Section: Introductionmentioning

confidence: 99%

Non-axisymmetric endwall profiling in a highly loaded compressor cascade

Cao

Liu

Zhang³

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part A:

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Very few studies of non-axisymmetric endwall profiling in compressor have been conducted in published literatures. This study investigates the control mechanism of non-axisymmetric endwall on the flow field of a highly loaded compressor cascade and the guidelines for the design of non-axisymmetric endwall. First, CFD method was validated with existing experimental data. Then, the design method of non-axisymmetric endwall based on trigonometric function and Bezier curve was introduced. The design strategies of non-axisymmetric endwall considering axial position effect, height effect and different patterns of concave/convex were investigated in detail. Results show that non-axisymmetric endwall is an effective way to control the near endwall flow field of the compressor cascade. With the optimal non-axisymmetric endwall in this study, the loss coefficient of the cascade is reduced by 5.5%, and the cascade exhibited suppressed corner separation, reduced passage vortex and more uniformly distributed outflow angles. The optimal axial position of the concave was at 0.22 axial chord, which was near the onset of corner separation, so the best control effect was obtained. There is an optimal height for the concave of the non-axisymmetric endwall. A lower concave will not have sufficient effect on the cascade, whereas a higher concave will be detrimental on the contrary. It is indicated that the influence mechanism of non-axisymmetric endwall on the compressor cascade is basically derived from the superimposed effect of reduced cross-passage pressure gradient and increased spanwise inward pressure gradient. The cross-passage pressure gradient can be reduced by both concave on the suction side and convex on the pressure side of the endwall. However, concave can introduce spanwise inward pressure gradient, whilst convex can introduce spanwise outward pressure gradient. For better improving the performance of compressor cascades, non-axisymmetric endwall is suggested to be a concave on the entire endwall, which introduces both reduced cross-passage pressure gradient and increased spanwise inward pressure gradient.

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Investigation of Nonaxisymmetric Endwall Contouring and Three-Dimensional Airfoil Design in a 1.5 Stage Axial Turbine—Part II: Experimental Validation

Cited by 16 publications

References 4 publications

Aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage axial turbine with nonaxisymmetric end wall contouring

Aerodynamic influence of rim seal purge flow injection on the main flow in a 1.5-stage axial turbine with nonaxisymmetric end wall contouring

Flow physics of highly loaded tandem compressor cascade with non-axisymmetric endwall profiling

Non-axisymmetric endwall profiling in a highly loaded compressor cascade

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