Experimental and Numerical Investigation of the Unsteady Surface Pressure in a Three-Stage Model of an Axial High Pressure Turbine

2004 ◽  
Vol 128 (2) ◽  
pp. 261-272 ◽  
Author(s):  
Carmen E. Kachel ◽  
John D. Denton
Keyword(s):  
High Pressure ◽  
Velocity Field ◽  
Surface Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Pressure Waves ◽  
Stage Model ◽  
Unsteady Pressure ◽  
Unsteady Surface Pressure ◽  
Blade Row

This paper presents the results of a numerical and experimental investigation of the unsteady pressure field in a three-stage model of a high pressure steam turbine. Unsteady surface pressure measurements were taken on a first and second stage stator blade, respectively. The measurements in the blade passage were supplemented by time resolved measurements between the blade rows. The explanation of the origin of the unsteady pressure fluctuations was supported by unsteady three-dimensional computational fluid dynamic calculations of which the most extensive calculation was performed over two stages. The mechanisms affecting the unsteady pressure field were: the potential field frozen to the upstream blade row, the pressure waves originating from changes in the potential pressure field, the convected unsteady velocity field, and the passage vortex of the upstream blade row. One-dimensional pressure waves and the unsteady variation of the pitchwise pressure gradient due to the changing velocity field were the dominant mechanisms influencing the magnitude of the surface pressure fluctuations. The magnitude of these effects had not been previously anticipated to be more important than other recognized effects.

Experimental and Numerical Investigation of the Unsteady Surface Pressure in a Three-Stage Model of an Axial High Pressure Turbine

2004 ◽  
Author(s):  
Carmen E. Kachel ◽  
John D. Denton
Keyword(s):  
High Pressure ◽  
Velocity Field ◽  
Surface Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Pressure Waves ◽  
Stage Model ◽  
Unsteady Pressure ◽  
Unsteady Surface Pressure ◽  
Blade Row

This paper presents the results of a numerical and experimental investigation of the unsteady pressure field in a three-stage model of a high pressure steam turbine. Unsteady surface pressure measurements were taken on a first and second stage stator blade respectively. The measurements in the blade passage were supplemented by time resolved measurements between the blade rows. The explanation of the origin of the unsteady pressure fluctuations was supported by unsteady three-dimensional computational fluid dynamic calculations of which the most extensive calculation was performed over two stage. The mechanisms affecting the unsteady pressure field were: the potential field frozen to the upstream blade row, the pressure waves originating from changes in the potential pressure field, the convected unsteady velocity field and the passage vortex of the upstream blade row. One-dimensional pressure waves and the unsteady variation of the pitchwise pressure gradient due to the changing velocity field were the dominant mechanisms influencing the magnitude of the surface pressure fluctuations. The magnitude of these effects had not been previously anticipated to be more important than other recognized effects.

scholarly journals Unsteady Interaction Between a Transonic Turbine Stage and Downstream Components

2004 ◽  
Vol 10 (6) ◽  
pp. 495-506 ◽  
Author(s):  
Roger L. Davis ◽  
Jixian Yao ◽  
John P. Clark ◽  
Gary Stetson ◽  
Juan J. Alonso ◽  
...  
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Surface Pressure ◽  
Low Pressure ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Unsteady Pressure ◽  
Low Pressure Turbine ◽  
Unsteady Surface Pressure ◽  
Turbine Vane

Results from a numerical simulation of the unsteady flow through one quarter of the circumference of a transonic high-pressure turbine stage, transition duct, and low-pressure turbine first vane are presented and compared with experimental data. Analysis of the unsteady pressure field resulting from the simulation shows the effects of not only the rotor/stator interaction of the high-pressure turbine stage but also new details of the interaction between the blade and the downstream transition duct and low-pressure turbine vane. Blade trailing edge shocks propagate downstream, strike, and reflect off of the transition duct hub and/or downstream vane leading to high unsteady pressure on these downstreamcomponents. The reflection of these shocks from the downstream components back into the blade itself has also been found to increase the level of unsteady pressure fluctuations on the uncovered portion of the blade suction surface. In addition, the blade tip vortex has been found to have a moderately strong interaction with the downstream vane even with the considerable axial spacing between the two blade-rows. Fourier decomposition of the unsteady surface pressure of the blade and downstream low-pressure turbine vane shows the magnitude of the various frequencies contributing to the unsteady loads. Detailed comparisons between the computed unsteady surface pressure spectrum and the experimental data are shown along with a discussion of the various interaction mechanisms between the blade, transition duct, and downstream vane. These comparisons show-overall good agreement between the simulation and experimental data and identify areas where further improvements in modeling are needed.

Investigation of Turbine Shroud Distortions on the Aerodynamics of a One and One-Half Stage High-Pressure Turbine

2009 ◽  
Author(s):  
Eric A. Crosh ◽  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
D. Graham Holmes ◽  
Brian E. Mitchell
Keyword(s):  
High Pressure ◽  
Surface Pressure ◽  
Turbo Code ◽  
Traditional Approach ◽  
Single Frequency ◽  
Pressure Measurements ◽  
Pressure Loading ◽  
High Pressure Turbine ◽  
Unsteady Pressure ◽  
Blade Row

As part of a proactive effort to investigate the ability of computational fluid dynamic (CFD) tools to predict time-accurate surface-pressure histories, a combined experimental/computational investigation was performed examining the effect of rotor shroud (casing) out-of-roundness on the unsteady pressure loading for the blade row of a full-stage turbine. The casing out-of-roundness was idealized by designing a casing ring with a sinusoidal variation. This casing ring was used to replace a flat casing for an existing turbine and direct comparisons were made between the time-accurate pressure measurements and predictions obtained using the flat and “wavy” casings. For both casing configurations, predictions of the unsteady pressure loading for many locations on the blade and vane were obtained using Numeca’s FINE/Turbo code and the General Electric TACOMA code. This paper will concentrate on the results obtained for the “wavy” casing, but the results for the flat casing are presented as a baseline case. The time-accurate surface-pressure measurements were acquired for the vane and blade of a modern, 3-D, stage and 1/2 high-pressure turbine operating at the design corrected speed and stage pressure ratio. The research program utilized an un-cooled turbine stage for which all three airfoil rows are heavily instrumented at multiple spans to develop a full dataset. The vane-blade-vane count for this machine is 38-72-38. The number of waves in the distorted shroud “wavy wall” is approximately 1.5-times the number of vanes. The resulting changes in aerodynamic surface-pressure measurements were measurable at all blade span wise locations. Variations in time-average surface pressure of up to 5% of the flat casing values were observed. In addition, the frequency content of the time-resolved blade data for the “wavy” casing changed substantially from that measured using the flat casing, with changes in both amplitudes and frequencies. Imposing the casing irregularity changed the fundamental physics of the problem from a single frequency and its harmonics to a multi-frequency problem with mixed harmonics. The unsteady effects of this type of problem can be addressed using the harmonic method within Numeca’s FINE/Turbo code, which is designed to handle multiple blade passing frequencies and harmonics for one blade row. A more traditional approach is included in the paper by employing the TACOMA code in a linearized mode that produces results for a single frequency. These results show that casing irregularity can have a significant influence on the blade surface-pressure characteristics. Further, it is demonstrated that the FINE/Turbo code experienced difficulty predicting the unsteady pressure signal attributed to the “wavy” casing configuration, while at the same time capturing the unsteady signal attributed to the vane passing due to limitations in the current methodology.

Investigation of Turbine Shroud Distortions on the Aerodynamics of a One and One-Half Stage High-Pressure Turbine

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Eric A. Crosh ◽  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
D. Graham Holmes ◽  
Brian E. Mitchell
Keyword(s):  
High Pressure ◽  
Surface Pressure ◽  
Turbo Code ◽  
Single Frequency ◽  
Pressure Measurements ◽  
Pressure Loading ◽  
High Pressure Turbine ◽  
Data Set ◽  
Unsteady Pressure ◽  
Blade Row

As part of a proactive effort to investigate the ability of computational fluid dynamics tools to predict time-accurate surface-pressure histories, a combined experimental/computational investigation was performed, examining the effect of rotor shroud (casing) out-of-roundness on the unsteady pressure loading for the blade row of a full-stage turbine. The casing out-of-roundness was idealized by designing a casing ring with a sinusoidal variation. This casing ring was used to replace a flat casing for an existing turbine, and direct comparisons were made between the time-accurate pressure measurements and predictions obtained using the flat and “wavy” casings. For both casing configurations, predictions of the unsteady pressure loading for many locations on the blade and vane were obtained using Numeca’s FINE/TURBO code and General Electric’s turbine and compressor analysis (TACOMA) code. This paper will concentrate on the results obtained for the wavy casing, but the results for the flat casing are presented as a baseline case. The time-accurate surface-pressure measurements were acquired for the vane and blade of a modern, 3D, 1 and 1/2 stage high-pressure turbine operating at the design corrected speed and stage pressure ratio. The research program utilized an uncooled turbine stage for which all three airfoil rows are heavily instrumented at multiple spans to develop a full data set. The vane-blade-vane count for this machine is 38-72-38. The number of waves in the distorted shroud “wavy wall” is approximately 1.5 times the number of vanes. The resulting changes in the aerodynamic surface-pressure measurements were measurable at all blade spanwise locations. Variations in the time-averaged surface pressure of up to 5% of the flat casing values were observed. In addition, the frequency content of the time-resolved blade data for the wavy casing changed substantially from that measured using the flat casing, with changes in both amplitudes and frequencies. Imposing the casing irregularity changed the fundamental physics of the problem from a single frequency and its harmonics to a multifrequency problem with mixed harmonics. The unsteady effects of this type of problem can be addressed using the harmonic method within Numeca’s FINE/TURBO code, which is designed to handle multiple blade passing frequencies and harmonics for one blade row. A more traditional approach is included in this paper by employing the TACOMA code in a linearized mode that produces results for a single frequency. These results show that casing irregularity can have a significant influence on the blade surface-pressure characteristics. Further, it is demonstrated that the FINE/TURBO code experienced difficulty in predicting the unsteady pressure signal attributed to the wavy casing configuration, while at the same time, in capturing the unsteady signal attributed to the vane passing due to limitations in the current methodology.

scholarly journals Unsteady Interaction Between a Transonic Turbine Stage and Downstream Components

2002 ◽  
Author(s):  
Roger L. Davis ◽  
Jixian Yao ◽  
John P. Clark ◽  
Gary Stetson ◽  
Juan J. Alonso ◽  
...  
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Surface Pressure ◽  
Low Pressure ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Unsteady Pressure ◽  
Low Pressure Turbine ◽  
Unsteady Surface Pressure ◽  
Turbine Vane

Results from a numerical simulation of the unsteady flow through one quarter of the circumference of a transonic high-pressure turbine stage, transition duct, and low-pressure turbine first vane are presented and compared with experimental data. Analysis of the unsteady pressure field resulting from the simulation shows the effects of not only the rotor/stator interaction of the high-pressure turbine stage but also new details of the interaction between the blade and the downstream transition duct and low-pressure turbine vane. Blade trailing edge shocks propagate downstream, strike, and reflect off of the transition duct hub and/or downstream vane leading to high unsteady pressure on these downstream components. The reflection of these shocks from the downstream components back into the blade itself has also been found to increase the level of unsteady pressure fluctuations on the uncovered portion of the blade suction surface. In addition, the blade tip vortex has been found to have a moderately strong interaction with the downstream vane even with the considerable axial spacing between the two blade-rows. Fourier decomposition of the unsteady surface pressure of the blade and downstream low-pressure turbine vane shows the magnitude of the various frequencies contributing to the unsteady loads. Detailed comparisons between the computed unsteady surface pressure spectrum and the experimental data are shown along with a discussion of the various interaction mechanisms between the blade, transition duct, and downstream vane. These comparisons show overall good agreement between the simulation and experimental data and identify areas where further improvements in modeling are needed.

Aeroacoustic analysis of slat tones

2021 ◽  
Vol 263 (1) ◽  
pp. 5650-5663
Author(s):  
Hasan Kamliya Jawahar ◽  
Syamir Alihan Showkat Ali ◽  
Mahdi Azarpeyvand
Keyword(s):  
Wavelet Transform ◽  
Surface Pressure ◽  
Wavelet Coefficient ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Stream Velocity ◽  
High Lift ◽  
Unsteady Surface Pressure ◽  
Slat Noise ◽  
Generation Mechanisms

Experimental measurements were carried out to assess the aeroacoustic characteristics of a 30P30N high-lift device, with particular attention to slat tonal noise. Three different types of slat modifications, namely slat cove filler, serrated slat cusp, and slat finlets have been experimentally examined. The results are presented for an angle of attack of α = 18 at a free-stream velocity of U = 30 m/s, which corresponds to a chord-based Reynolds number of Re = 7 x 10. The unsteady surface pressure near the slat region and far-field noise were made simultaneously to gain a deeper understanding of the slat noise generation mechanisms. The nature of the low-frequency broadband hump and the slat tones were investigated using higher-order statistical approaches for the baseline 30P30N and modified slat configurations. Continuous wavelet transform of the unsteady surface pressure fluctuations along with secondary wavelet transform of the broadband hump and tones were carried out to analyze the intermittent events induced by the tone generating resonant mechanisms. Stochastic analysis of the wavelet coefficient modulus of the surface pressure fluctuations was also carried out to demonstrate the inherent differences of different tonal frequencies. An understanding into the nature of the noise generated from the slat will help design the new generation of quite high-lift devices.

Unsteady Pressure Measurement on Oscillating Blade in Transonic Flow Using Fast-Response Pressure-Sensitive Paint

2017 ◽  
Author(s):  
Toshinori Watanabe ◽  
Toshihiko Azuma ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Chihiro Inoue
Keyword(s):  
Surface Pressure ◽  
Transonic Flow ◽  
Aerodynamic Force ◽  
Fast Response ◽  
Pressure Sensitive Paint ◽  
Unsteady Pressure ◽  
Pressure Distributions ◽  
Pressure Sensitive ◽  
Unsteady Surface Pressure ◽  
Response Pressure

A fast-response pressure-sensitive paint (PSP) technique was applied to the measurement of unsteady surface pressure of an oscillating cascade blade in a transonic flow. A linear cascade was used, and its central blade was oscillated in a translational manner. The unsteady pressure distributions of the oscillating blade and two stationary neighbors were measured using the fast-response PSP technique, and the unsteady aerodynamic force on the blade was obtained by integrating the data obtained on the pressures. The measurements made with the PSP technique were compared with those obtained by conventional methods for the purpose of validation. From the results, the PSP technique was revealed to be capable of measuring the unsteady surface pressure, which is used for flutter analysis in transonic conditions.

Unsteady Flow Structure on a Centrifugal Pump: Experimental and Numerical Approaches

2002 ◽  
Author(s):  
Jose´ Gonza´lez ◽  
Carlos Santolaria ◽  
Eduardo Blanco ◽  
Joaqui´n Ferna´ndez
Keyword(s):  
Numerical Model ◽  
Centrifugal Pump ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Side Wall ◽  
Relative Effect ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Blade Passing Frequency ◽  
Wide Range

Both experimental and numerical studies of the unsteady pressure field inside a centrifugal pump have been carried out. The unsteady patterns found for the pressure fluctuations are compared and a further and more detailed flow study from the numerical model developed will be presented in this paper. Measurements were carried out with pressure transducers installed on the volute shroud. At the same time, the unsteady pressure field inside the volute of a centrifugal pump has been numerically modelled using a finite volume commercial code and the dynamic variables obtained have been compared with the experimental data available. In particular, the amplitude of the fluctuating pressure field in the shroud side wall of the volute at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Once the developed numerical model has shown its capability in describing the unsteady patterns experimentally measured, an explanation for such patterns is searched. Moreover, the possibilities of the numerical model can be extended to other sections (besides the shroud wall of the volute), which can provide plausible explanations for the dynamic interaction effects between the flow at the impeller exit and the volute tongue at different axial positions. The results of the numerical simulation are focused in the blade passing frequency in order to study the relative effect of the two main phenomena occurring at that frequency for a given position: the blade passing in front of the tongue and the wakes of the blades.

Turbulent Pressure-Velocity Measurements in a Fully Developed Concentric Annular Air Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 345-354 ◽  
Author(s):  
R. J. Wilson ◽  
B. G. Jones
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Core Region ◽  
Flow Channel ◽  
Wall Pressure ◽  
Analysis Method ◽  
Local Pressure ◽  
Wall Pressure Fluctuations

An experimental study of the fluctuating velocity field and the fluctuating static wall pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field and fluctuating static wall pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained. The effect of the turbulent core region of the flow on the wall pressure fluctuations was studied by cross-correlating the axial and radial velocity components with the wall pressure fluctuations. A three-sensor, signal subtraction data analysis method using coherence techniques was developed to separate the superimposed local pressure fluctuations and acoustically transmitted noise. This analysis method is shown to adequately isolate the local pressure fluctuation information at each wall of the flow channel. The results of the experimental measurements are compared with existing experimental and numerical information on turbulent annular flow fields and wall pressure statistics. The pressure-velocity correlation indicates that a substantial contribution to the pressure field on the wall of the flow channel is from the turbulent core region outside of the boundary layer. The wall pressure field is shown to be significantly different on the two dissimilar walls. The pressure-velocity correlations show that this difference is due to the geometric difference between the dissimilar volumetric sources which contribute to the wall pressure field. The results of this study show that vibration modeling must incorporate the effects of the flow geometry on the wall pressure statistics, which are used as the driving force for flow-induced vibrations.

Experimental and Unsteady Numerical Investigation of the Tip Clearance Noise of an Axial Fan

2013 ◽  
Author(s):  
Tao Zhu ◽  
Thomas H. Carolus
Keyword(s):  
Surface Pressure ◽  
Temporal Structure ◽  
Pressure Fluctuations ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Far Field ◽  
Axial Fan ◽  
Clearance Ratio ◽  
Wall Pressure Fluctuations ◽  
Unsteady Surface Pressure

The aerodynamic and aeroacoustic performance of axial fans are strongly affected by the unavoidable tip clearance. Two identical fan impellers but with different tip clearance ratio were investigated. Unsteady wall pressure fluctuations in the tip region of the rotating blades and on the interior wall of the duct type shroud and the overall sound radiated were analysed by an unsteady numerical Scale-Adaptive Simulation (SAS) and unsteady surface pressure measurements in both, the stationary and rotating system. Based on SAS-predicted pressure fluctuations on the blade surfaces the acoustic analogy according to Ffowcs Williams and Hawkings (FWH) was employed to calculate the sound pressure in the far field. In general, experimentally and numerically determined unsteady flow were found to be a tendentially good agreement. The spatial and temporal structure of the tip vortex system and the resulting unsteady pressure distribution on the surfaces in the vicinity of the blade tips was revealed in good detail. The vortices’ strength and trajectories as well as the unsteadiness are controlled by the size of the tip clearance and the operating point: As tip clearance is increased blade/vortex interaction becomes more prevalent and with it the unsteady surface pressure and eventually the sound radiated into the far field. The broadband tip clearance noise was acceptably predicted from the simulation results, while the prediction at discrete frequency should still be improved in the further work.

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