The Effect of Manufacturing Variations on Unsteady Interaction in a Transonic Turbine

2017 ◽  
Author(s):  
John P. Clark ◽  
Joseph A. Beck ◽  
Alex A. Kaszynski ◽  
Angela Still ◽  
Ron-Ho Ni
Keyword(s):  
Fourier Transforms ◽  
Optical Measurement ◽  
Turbine Blades ◽  
Region Of Interest ◽  
Navier Stokes ◽  
Analysis Tool ◽  
Grid Data ◽  
Discrete Fourier Transforms ◽  
Numerical Predictions ◽  
Transonic Turbine

This effort focuses on the comparison of unsteadiness due to as-measured turbine blades in a transonic turbine to that obtained with blueprint geometries via computational fluid dynamics (CFD). A Reynolds-averaged Navier-Stokes flow solver with the two-equation Wilcox turbulence model is used as the numerical analysis tool for comparison between the blueprint geometries and as-manufactured geometries obtained from a structured light optical measurement system. The nominal turbine CFD grid data defined for analysis of the blueprint blade was geometrically modified to reflect as-manufactured turbine blades using an established mesh metamorphosis algorithm. The approach uses a modified neural network to iteratively update the source mesh to the target mesh. In this case the source is the interior CFD surface grid while the target is the surface blade geometry obtained from the optical scanner. Nodes interior to the CFD surface were updated using a modified iterative spring analogy to avoid grid corruption when matching as-manufactured part geometry. This approach avoids the tedious manual approach of regenerating the CFD grid and does not rely on geometry obtained from Coordinate Measurement Machine (CMM) sections, but rather a point cloud representing the entirety of the turbine blade. Surface pressure traces and the discrete Fourier transforms thereof from numerical predictions of as-measured geometries are then compared both to blueprint predictions and to experimental measurements. The importance of incorporating as-measured geometries in analyses to explain deviations between numerical predictions of blueprint geometries and experimental results is readily apparent. Further analysis of every casting produced in the creation of the test turbine yields variations that one can expect in both aero-performance and unsteady loading as a consequence of manufacturing tolerances. Finally, the use of measured airfoil geometries to reduce the unsteady load on a target blade in a region of interest is successfully demonstrated.

The Effect of Manufacturing Variations on Unsteady Interaction in a Transonic Turbine

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
John P. Clark ◽  
Joseph A. Beck ◽  
Alex A. Kaszynski ◽  
Angela Still ◽  
Ron-Ho Ni
Keyword(s):  
Fourier Transforms ◽  
Optical Measurement ◽  
Turbine Blades ◽  
Region Of Interest ◽  
Navier Stokes ◽  
Analysis Tool ◽  
Grid Data ◽  
Discrete Fourier Transforms ◽  
Numerical Predictions ◽  
Transonic Turbine

This effort focuses on the comparison of unsteadiness due to as-measured turbine blades in a transonic turbine to that obtained with blueprint geometries via computational fluid dynamics (CFD). A Reynolds-averaged Navier–Stokes flow solver with the two-equation Wilcox turbulence model is used as the numerical analysis tool for comparison between the blueprint geometries and as-manufactured geometries obtained from a structured light optical measurement system. The nominal turbine CFD grid data defined for analysis of the blueprint blade were geometrically modified to reflect as-manufactured turbine blades using an established mesh metamorphosis algorithm. The approach uses a modified neural network to iteratively update the source mesh to the target mesh. In this case, the source is the interior CFD surface grid while the target is the surface blade geometry obtained from the optical scanner. Nodes interior to the CFD surface were updated using a modified iterative spring analogy to avoid grid corruption when matching as-manufactured part geometry. This approach avoids the tedious manual approach of regenerating the CFD grid and does not rely on geometry obtained from coordinate measurement machine (CMM) sections, but rather a point cloud representing the entirety of the turbine blade. Surface pressure traces and the discrete Fourier transforms (DFT) thereof from numerical predictions of as-measured geometries are then compared both to blueprint predictions and to experimental measurements. The importance of incorporating as-measured geometries in analyses to explain deviations between numerical predictions of blueprint geometries and experimental results is readily apparent. Further analysis of every casting produced in the creation of the test turbine yields variations that one can expect in both aero-performance and unsteady loading as a consequence of manufacturing tolerances. Finally, the use of measured airfoil geometries to reduce the unsteady load on a target blade in a region of interest is successfully demonstrated.

scholarly journals Unsteady Aerodynamic Interaction in a Closely Coupled Turbine Consistent With Contrarotation

2016 ◽  
Vol 138 (6) ◽  
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.

scholarly journals Unsteady Aerodynamic Interaction in a Closely-Coupled Turbine Consistent With Contra-Rotation

2015 ◽  
Author(s):  
Michael K. Ooten ◽  
Richard J. Anthony ◽  
Andrew T. Lethander ◽  
John P. Clark
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Fourier Transforms ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Experimental Tests ◽  
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 the stage-and-one-half transonic turbine via 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 for 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 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.

Effects of Downstream Vane Bowing and Asymmetry on Unsteadiness in a Transonic Turbine

2018 ◽  
Author(s):  
John P. Clark ◽  
Richard J. Anthony ◽  
Michael K. Ooten ◽  
John M. Finnegan ◽  
P. Dean Johnson ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Resolved ◽  
Turbine Engine ◽  
Shock Interactions ◽  
Design Changes ◽  
Post Test ◽  
Measured Time ◽  
Transonic Turbine

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.

The Impact of Excitation and Mode Shape on Non-Linear Blade Vibrations

2020 ◽  
Author(s):  
Johannes Linhard ◽  
Andreas Hartung ◽  
Stefan Schwarz ◽  
Hans-Peter Hackenberg ◽  
Mateusz Sienko
Keyword(s):  
Mode Shape ◽  
Optical Measurement ◽  
Turbine Blades ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Vibration Measurement ◽  
Numerical Predictions ◽  
Non Linear ◽  
Strain Gauge Measurements ◽  
The Impact

Abstract Recently, reliable non-linear dynamic solvers for the analysis of frictionally coupled turbine blades have been developed which are based on either Higher Harmonic Balance Method or Non-linear Modal Analysis. One of these tools is OrAgL which was developed by Institute of Dynamics of Vibrations (Leibniz University of Hannover) and Institute of Aircraft Propulsion Systems (University of Stuttgart). In [1], the rig and engine validation results of with OrAgL performed forced response analyses have been published: The main aim of this paper was the comparison of non-linear numerical predictions (amplitude, frequencies) with the blade-to-blade averaged values of optical measurement results obtained using MTU’s non-contact vibration measurement system for shrouded turbine blades (BSSM-T). Detailed analyses and validations performed over the last two years showed several novel aspects of validation such as the comparison with strain gauge measurements. Moreover, a better understanding of the impact of excitation (magnitude and load distribution over the airfoil) as well as of the impact of the mode shape on the formation of saturation regimes is now possible. The results obtained from the analyses of real turbine blades are presented in this work.

Effects of Downstream Vane Bowing and Asymmetry on Unsteadiness in a Transonic Turbine

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
John P. Clark ◽  
Richard J. Anthony ◽  
Michael K. Ooten ◽  
John M. Finnegan ◽  
P. Dean Johnson ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Resolved ◽  
Turbine Engine ◽  
Shock Interactions ◽  
Design Changes ◽  
Post Test ◽  
Measured Time ◽  
Transonic Turbine

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 (3D), 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 nonuniform pitch.

An Analysis of the Spatial Fluctuations at the Stator-Rotor Interface in a Transonic Turbine

2001 ◽  
Author(s):  
Stanislas Callot ◽  
Pascal Ferrand
Keyword(s):  
Fourier Transforms ◽  
Angular Speed ◽  
Navier Stokes ◽  
Computational Results ◽  
Turbine Stage ◽  
Spatial Fluctuations ◽  
Transonic Turbine ◽  
Spatio Temporal ◽  
Temporal Periodicity

This paper analyses the flow in a transonic turbine stage, using numerical results from a full 3D Navier-Stokes computation over the whole stage. This analysis, based on the combination of time and space Fourier transforms, points out how a spatio-temporal periodicity phenomenon is involved in the so-called stator-rotor interaction. A first comparison is made between the computational results using geometrical approximation and the results achieved by the complete simulation. This analysis points out how the signal is enforced by the numerical conditions at the circumferential boundaries. The stator-rotor interaction produces low spatial harmonics which are identified as spinning modes by means of Fourier series. The analytical theory from Tyler and Sofrin (1962) is then used to define a general model of stator-rotor interaction. This model allows the determination of the angular speed of rotation of the spinning modes, and results are compared with the global numerical simulation. Finally, a first analysis of the axial propagation of the spinning modes is proposed, and attention is focused on the fact, that only few parameters are necessary to reproduce the unsteady signal.

Surrogate Modeling of Manufacturing Variation Effects on Unsteady Interactions in a Transonic Turbine

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Jeffrey M. Brown ◽  
Joseph Beck ◽  
Alexander Kaszynski ◽  
John Clark
Keyword(s):  
Surrogate Model ◽  
Optical Measurement ◽  
Surrogate Modeling ◽  
Point Clouds ◽  
Nearest Neighbor Search ◽  
Model Parameters ◽  
Grid Data ◽  
Reduced Basis ◽  
Small Impact ◽  
Transonic Turbine

This effort develops a surrogate modeling approach for predicting the effects of manufacturing variations on performance and unsteady loading of a transonic turbine. Computational fluid dynamics (CFD) results from a set of 105 as-manufactured turbine blade geometries are used to train and validate the surrogate models. Blade geometry variation is characterized with point clouds gathered from a structured light, optical measurement system and as-measured CFD grids are generated through mesh morphing of the nominal design grid data. Principal component analysis (PCA) of the measured airfoil geometry variations is used to create a reduced basis of independent surrogate model parameters. It is shown that the surrogate model typically captures between 60% and 80% of the CFD predicted variance. Three new approaches are introduced to improve surrogate effectiveness. First, a zonal PCA approach is defined which investigates surrogate accuracy when limiting analysis to key regions of the airfoil. Second, a training point reduction strategy is proposed that is based on the k–d tree nearest neighbor search algorithm and reduces the required training points up to 38% while only having a small impact on accuracy. Finally, an alternate reduction approach uses k-means clustering to effectively select training points and reduces the required training points up to 66% with a small impact on accuracy.

Surrogate Modeling of Manufacturing Variation Effects on Unsteady Interactions in a Transonic Turbine

2018 ◽  
Author(s):  
Jeffrey M. Brown ◽  
Joseph Beck ◽  
Alexander Kaszynski ◽  
John Clark
Keyword(s):  
Surrogate Model ◽  
Optical Measurement ◽  
Surrogate Modeling ◽  
Point Clouds ◽  
Nearest Neighbor Search ◽  
Model Parameters ◽  
Grid Data ◽  
Reduced Basis ◽  
Validation Data ◽  
Transonic Turbine

This effort develops a surrogate modeling approach for predicting the effects of manufacturing variations on blade unsteadiness and performance of a transonic turbine. CFD results from a set of 105 as-manufactured turbine blade geometries are used to train and validate the surrogate models. Blade geometry variation is characterized with point clouds created from a structured light optical measurement system and as-measured CFD grids are generated through mesh morphing of the nominal design grid data. Results from a Reynolds-averaged Navier-Stokes flow solver with the two-equation Wilcox turbulence model are used as training and validation data. Principal Component Analysis (PCA) of the measured airfoil geometry variations is used to create reduced basis of independent surrogate model parameters. Results of the surrogate are compared to the CFD results. It is shown that the surrogate model typically captures between 60% and 80% of the full CFD predicted variance. Three new approaches are introduced to improve the accuracy of the surrogate. A zonal PCA approach is defined which improves surrogate accuracy by focusing on key regions of the airfoil. A training point reduction strategy is proposed that is based on the kd-tree nearest neighbor search algorithm and reduces the required training points by 25%. A second reduction approach uses k-means clustering to effectively select training points from the 105 blade population and is used to reduce the required training points by up to 66%.

Sign in / Sign up

Export Citation Format

Share Document