Unsteady Strong Shock Interactions in a Transonic Turbine: Experimental and Numerical Analysis

Accurate predictions of unsteady forcing on turbine blades are essential for the avoidance of high-cycle-fatigue issues during turbine engine development. Further, if one can demonstrate that predictions of unsteady interaction in a turbine are accurate, then it becomes possible to anticipate resonant-stress problems and mitigate them through aerodynamic design changes during the development cycle. A successful reduction in unsteady forcing for a transonic turbine with significant shock interactions due to downstream components is presented here. A pair of methods to reduce the unsteadiness was considered and rigorously analyzed using a three-dimensional, time resolved Reynolds-Averaged Navier Stokes (RANS) solver. The first method relied on the physics of shock reflections itself and involved altering the stacking of downstream components to achieve a bowed airfoil. The second method considered was circumferentially-asymmetric vane spacing which is well known to spread the unsteadiness due to vane-blade interaction over a range of frequencies. Both methods of forcing reduction were analyzed separately and predicted to reduce unsteady pressures on the blade as intended. Then, both design changes were implemented together in a transonic turbine experiment and successfully shown to manipulate the blade unsteadiness in keeping with the design-level predictions. This demonstration was accomplished through comparisons of measured time-resolved pressures on the turbine blade to others obtained in a baseline experiment that included neither asymmetric spacing nor bowing of the downstream vane. The measured data were further compared to rigorous post-test simulations of the complete turbine annulus including a bowed downstream vane of non-uniform pitch.

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Numerical Analysis of Shock Interactions with the Example of Painleve Paradox with a “Slanted” Fall of a Rod

Automation and Remote Control ◽

10.1134/s0005117919100059 ◽

2019 ◽

Vol 80 (10) ◽

pp. 1835-1846

Author(s):

B. M. Miller ◽

E. Ya. Rubinovich

Keyword(s):

Numerical Analysis ◽

Painlevé Paradox ◽

Shock Interactions

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Investigation on the Reduction of Trailing Edge Shock Losses for a Highly Loaded Transonic Turbine

Volume 2B: Turbomachinery ◽

10.1115/gt2016-56131 ◽

2016 ◽

Cited By ~ 5

Author(s):

Wei Zhao ◽

Weiwei Luo ◽

Qingjun Zhao ◽

Jianzhong Xu

Keyword(s):

Turbine Blades ◽

Strong Shock ◽

Suction Side ◽

Loss Reduction ◽

Blade Profile ◽

Trailing Edge ◽

Pressure Loss Coefficient ◽

Reflected Shock ◽

Transonic Turbine ◽

Highly Loaded

A shock loss reduction method for highly loaded transonic turbine blades with convergent passages is presented. The method is illustrated with an improved blade profile that employs a negative curvature curve on its uncovered suction side. The improved profile and a conventional baseline profile are applied to two cascades with the same solidity, chord and aspect ratio respectively. The numerical simulation results for the two cascades show that a reduction of 4.58% in the total pressure loss coefficient is obtained for the improved profile at the design condition. The effects of back pressures on the performance of both cascades are also presented, and the improved blade profile shows a much better part-load performance. The paper compares the flow fields of the baseline and the improved blade profiles to understand loss reduction mechanism especially by analyzing the shock interactions downstream of the trailing edge. It is found that, for the improved profile, the reflected shock of pressure side leg of the trailing-edge shock rotates forward and the suction side leg of the trailing-edge shock rotates backward. Therefore, the two shocks delay their intersection points where they merge into a relatively strong shock, and consequently produce less shock losses than those of the baseline profile.

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Ghost Fluid Method for Strong Shock Interactions Part 2: Immersed Solid Boundaries

AIAA Journal ◽

10.2514/1.43153 ◽

2009 ◽

Vol 47 (12) ◽

pp. 2923-2937 ◽

Cited By ~ 51

Author(s):

Shiv Kumar Sambasivan ◽

H. S. UdayKumar

Keyword(s):

Strong Shock ◽

Ghost Fluid Method ◽

Shock Interactions

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Numerical analysis of the aerodynamic performance & heat transfer of a transonic turbine with a partial squealer tip

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2019.02.066 ◽

2019 ◽

Vol 152 ◽

pp. 878-889 ◽

Cited By ~ 4

Author(s):

Jae Hoon Kim ◽

Seung Yeob Lee ◽

Jin Taek Chung

Keyword(s):

Heat Transfer ◽

Numerical Analysis ◽

Aerodynamic Performance ◽

Transonic Turbine

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Unsteady Aerodynamic Interaction in a Closely Coupled Turbine Consistent With Contrarotation

Journal of Turbomachinery ◽

10.1115/1.4032284 ◽

2016 ◽

Vol 138 (6) ◽

Cited By ~ 3

Author(s):

Michael K. Ooten ◽

Richard J. Anthony ◽

Andrew T. Lethander ◽

John P. Clark

Keyword(s):

Experimental Data ◽

Numerical Analysis ◽

Fourier Transforms ◽

Incidence Angle ◽

Fluid Dynamic ◽

Pressure Ratio ◽

Three Dimensional ◽

Analysis Tool ◽

Discrete Fourier Transforms ◽

Transonic Turbine

The focus of the study presented here was to investigate the interaction between the blade and downstream vane of a stage-and-one-half transonic turbine via computation fluid dynamic (CFD) analysis and experimental data. A Reynolds-averaged Navier–Stokes (RANS) flow solver with the two-equation Wilcox 1998 k–ω turbulence model was used as the numerical analysis tool for comparison with all of the experiments conducted. The rigor and fidelity of both the experimental tests and numerical analysis methods were built through two- and three-dimensional steady-state comparisons, leading to three-dimensional time-accurate comparisons. This was accomplished by first testing the midspan and quarter-tip two-dimensional geometries of the blade in a linear transonic cascade. The effects of varying the incidence angle and pressure ratio on the pressure distribution were captured both numerically and experimentally. This was used during the stage-and-one-half post-test analysis to confirm that the target corrected speed and pressure ratio were achieved. Then, in a full annulus facility, the first vane itself was tested in order to characterize the flowfield exiting the vane that would be provided to the blade row during the rotating experiments. Finally, the full stage-and-one-half transonic turbine was tested in the full annulus cascade with a data resolution not seen in any studies to date. A rigorous convergence study was conducted in order to sufficiently model the flow physics of the transonic turbine. The surface pressure traces and the discrete Fourier transforms (DFT) thereof were compared to the numerical analysis. Shock trajectories were tracked through the use of two-point space–time correlation coefficients. Very good agreement was seen when comparing the numerical analysis to the experimental data. The unsteady interaction between the blade and downstream vane was well captured in the numerical analysis.

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