Noise Characteristics Corresponding to High-Level Rotor Blades Nonsynchronous Vibrations in an Axial Compressor

Rotating instability can be observed in the tip flow region of axial compressor stage while stable operation. In order to investigate the noise characteristics in a multi-stage axial compressor, the noise inner compressor casing is measured simultaneously with the vibration of the rotor blades on a high pressure compressor component rig testing. An azimuthal mode analysis and theoretical formulation of the rotating source mechanism are applied to the unsteady pressure at the casing wall immediately upstream of the inlet plane of the rotor. It is shown that RIs might be described by a group of superimposed modes. This is the reason why RIs can be identiﬁed as an amplitude increase in a frequency band. The mode orders of RI are consecutively numbered riseing with frequency. The frequency in the source frame (ωN) closed to the frequency in the rotating frame (ωN) can be got well recovered. The results presented in this paper can be a reference for further understanding of the characteristics of unsteady flow field and the effects of the high intensity sound waves on the rotor blades.

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Analysis of the Inter-Row Flow Field Within a Transonic Axial Compressor: Part 2 — Unsteady Flow Analysis

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/2000-gt-0497 ◽

2000 ◽

Cited By ~ 1

Author(s):

Xavier Ottavy ◽

Isabelle Trébinjac ◽

André Vouillarmet

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Flow Analysis ◽

Axial Compressor ◽

Leading Edge ◽

Rotor Blades ◽

Time Averaging ◽

Flow Phenomena ◽

Order Of Magnitude ◽

Transonic Axial Compressor

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor inter-row region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time averaging procedure and the purely time-dependent velocity fluctuations which occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the 3D rotor time-averaged simulations.

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Analysis of the Interrow Flow Field Within a Transonic Axial Compressor: Part 2—Unsteady Flow Analysis

Journal of Turbomachinery ◽

10.1115/1.1328086 ◽

2000 ◽

Vol 123 (1) ◽

pp. 57-63 ◽

Cited By ~ 12

Author(s):

Xavier Ottavy ◽

Isabelle Tre´binjac ◽

Andre´ Vouillarmet

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Flow Analysis ◽

Three Dimensional ◽

Axial Compressor ◽

Leading Edge ◽

Rotor Blades ◽

Time Averaging ◽

Order Of Magnitude ◽

Transonic Axial Compressor

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor interrow region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time-averaging procedure and the purely time-dependent velocity fluctuations that occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the three-dimensional rotor time-averaged simulations.

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Influence of a Cylindrical Exhaust Hood Installation on the Last Stage Rotor Blades of a Low Pressure Model Steam Turbine

Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines ◽

10.1115/gt2017-63280 ◽

2017 ◽

Author(s):

Fabian F. Müller ◽

Markus Schatz ◽

Damian M. Vogt ◽

Jens Aschenbruck

Keyword(s):

Flow Field ◽

Steam Turbine ◽

Operating Conditions ◽

Rotor Blades ◽

Pressure Measurements ◽

Exhaust Hood ◽

Blade Vibration ◽

Time Resolved ◽

Vibration Behavior ◽

Last Stage

The influence of a cylindrical strut shortly downstream of the bladerow on the vibration behavior of the last stage rotor blades of a single stage LP model steam turbine was investigated in the present study. Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam turbine exhaust hoods are generally not modified, the last stage rotor blades frequently move closer to installations within the exhaust hood. To capture the influence of such an installation on the flow field characteristics, extensive flow field measurements using pneumatic probes were conducted at the turbine outlet plane. In addition, time-resolved pressure measurements along the casing contour of the diffuser and on the surface of the cylinder were made, aiming for the identification of pressure fluctuations induced by the flow around the installation. Blade vibration behavior was measured at three different operating conditions by means of a tip timing system. Despite the considerable changes in the flow field and its frequency content, no significant impact on blade vibration amplitudes were observed for the investigated case and considered operating conditions. Nevertheless, time-resolved pressure measurements suggest that notable pressure oscillations induced by the vortex shedding can reach the upstream bladerow.

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Aerodynamic-Rotordynamic Interaction in Axial Compression Systems—Part I: Modeling and Analysis of Fluid-Induced Forces

Journal of Turbomachinery ◽

10.1115/1.1576430 ◽

2003 ◽

Vol 125 (3) ◽

pp. 405-415

Author(s):

Ammar A. Al-Nahwi ◽

James D. Paduano ◽

Samir A. Nayfeh

Keyword(s):

Flow Field ◽

Axial Compressor ◽

Pressure Rise ◽

Essential Element ◽

Rotor Blades ◽

Tip Clearance ◽

Analytical Models ◽

Modeling And Analysis ◽

Equal Importance ◽

Consistent Treatment

This paper presents a first principles-based model of the fluid-induced forces acting on the rotor of an axial compressor. These forces are primarily associated with the presence of a nonuniform flow field around the rotor, such as that produced by a rotor tip clearance asymmetry. Simple, analytical expressions for the forces as functions of basic flow field quantities are obtained. These expressions allow an intuitive understanding of the nature of the forces and—when combined with a rudimentary model of an axial compressor flow field (the Moore-Greitzer model)—enable computation of the forces as a function of compressor geometry, torque and pressure-rise characteristics, and operating point. The forces predicted by the model are also compared to recently published measurements and more complex analytical models, and are found to be in reasonable agreement. The model elucidates that the fluid-induced forces comprise three main contributions: fluid turning in the rotor blades, pressure distribution around the rotor, and unsteady momentum storage within the rotor. The model also confirms recent efforts in that the orientation of fluid-induced forces is locked to the flow nonuniformity, not to tip clearance asymmetry as is traditionally assumed. The turning and pressure force contributions are shown to be of comparable magnitudes—and therefore of equal importance—for operating points between the design point and the peak of the compressor characteristic. Within this operating range, both “forward” and “backward” rotor whirl tendencies are shown to be possible. This work extends recent efforts by developing a more complete, yet compact, description of fluid-induced forces in that it accounts for all relevant force contributions, both tangential and radial, that may influence the dynamics of the rotor. Hence it constitutes an essential element of a consistent treatment of rotordynamic stability under the action of fluid-induced forces, which is the subject of Part II of this paper.

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Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach

Volume 1: Compressors, Fans and Pumps; Turbines; Heat Transfer; Combustion, Fuels and Emissions ◽

10.1115/gtindia2017-4762 ◽

2017 ◽

Author(s):

Kirubakaran Purushothaman ◽

Sankar Kumar Jeyaraman ◽

Ajay Pratap ◽

Kishore Prasad Deshkulkarni

Keyword(s):

Aspect Ratio ◽

Rotor Blade ◽

Axial Compressor ◽

Operating Conditions ◽

Rotor Blades ◽

Blade Profile ◽

Interaction Technique ◽

Compressor Rotor ◽

Blade Shape ◽

Blade Geometry

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.

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Experimental Assessment of Fouling Effects in a Multistage Axial Compressor

E3S Web of Conferences ◽

10.1051/e3sconf/202019711007 ◽

2020 ◽

Vol 197 ◽

pp. 11007

Author(s):

Nicola Casari ◽

Michele Pinelli ◽

Pier Ruggero Spina ◽

Alessio Suman ◽

Alessandro Vulpio

Keyword(s):

Gas Turbine ◽

Axial Compressor ◽

Operating Conditions ◽

Rotor Blades ◽

Small Scale ◽

Performance Loss ◽

Machine Performance ◽

Internal Surfaces ◽

Analysis Package ◽

Multistage Axial Compressor

The study of the adhesion of micro sized particles to gas turbine internal surfaces, commonly known as gas turbine fouling, has gained increasing attention in the last years due to its dramatic effect on machine performance and reliability. On-field fouling analysis is mostly related to visual inspections during overhaul and/or programmed stops, which are performed, in particular, when gas turbine performance degradation falls under predetermined thresholds. However, these analyses, even if performed in the most complete as possible way, are rarely (or never) related to the conditions under which the gas turbine contamination takes place since the affecting parameters are difficult or even impossible to be adequately monitored. In the present work, a small scale multistage axial compressor is used to experimentally simulate the fouling phenomenon. The test rig allows the accurate control of the most relevant operating parameters which influence the fouling phenomenon. The compressor performance loss due to particle contamination has been quantitatively assessed. Soot particles appear stickier, especially in the presence of high humidity, and represent the most harmful operating conditions for the compressor unit. The deposits on the stator vanes and the rotor blades have been detected and post-processed, highlighting the most affected regions of each compressor stage employing an image analysis package tool.

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Aerodynamic-Rotordynamic Interaction in Axial Compression Systems: Part I — Modeling and Analysis of Fluid-Induced Forces

Volume 4: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30488 ◽

2002 ◽

Author(s):

Ammar A. Al-Nahwi ◽

James D. Paduano ◽

Samir A. Nayfeh

Keyword(s):

Flow Field ◽

Axial Compressor ◽

Pressure Rise ◽

Essential Element ◽

Rotor Blades ◽

Tip Clearance ◽

Analytical Models ◽

Modeling And Analysis ◽

Equal Importance ◽

Consistent Treatment

This paper presents a first principles-based model of the fluid-induced forces acting on the rotor of an axial compressor. These forces are primarily associated with the presence of a nonuniform flow field around the rotor, such as that produced by a rotor tip clearance asymmetry. Simple, analytical expressions for the forces as functions of basic flow field quantities are obtained. These expressions allow an intuitive understanding of the nature of the forces and—when combined with a rudimentary model of an axial compressor flow field (the Moore-Greitzer model)—enable computation of the forces as a function of compressor geometry, torque and pressure-rise characteristics, and operating point. The forces predicted by the model are also compared to recently published measurements and more complex analytical models, and are found to be in reasonable agreement. The model elucidates that the fluid-induced forces comprise three main contributions: fluid turning in the rotor blades, pressure distribution around the rotor, and unsteady momentum storage within the rotor. The model also confirms recent efforts in that the orientation of fluid-induced forces is locked to the flow nonuniformity, not to tip clearance asymmetry as is traditionally assumed. The turning and pressure force contributions are shown to be of comparable magnitudes—and therefore of equal importance—for operating points between the design point and the peak of the compressor characteristic. Within this operating range, both “forward” and “backward” rotor whirl tendencies are shown to be possible. This work extends recent efforts by developing a more complete, yet compact, description of fluid-induced forces in that it accounts for all relevant force contributions, both tangential and radial, that may influence the dynamics of the rotor. Hence it constitutes an essential element of a consistent treatment of rotordynamic stability under the action of fluid-induced forces, which is the subject of Part II of this paper.

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Flow Structure and Unsteady Behavior of Hub-Corner Separation in a Stator Cascade of a Multi-Stage Transonic Axial Compressor

Volume 2A: Turbomachinery ◽

10.1115/gt2018-76480 ◽

2018 ◽

Cited By ~ 1

Author(s):

Seishiro Saito ◽

Kazutoyo Yamada ◽

Masato Furukawa ◽

Keisuke Watanabe ◽

Akinori Matsuoka ◽

...

Keyword(s):

Data Mining ◽

Flow Field ◽

Unsteady Flow ◽

Axial Compressor ◽

Flow Fields ◽

Suction Surface ◽

Corner Separation ◽

High Loss ◽

Stator Blade ◽

Transonic Axial Compressor

This paper describes unsteady flow phenomena of a two-stage transonic axial compressor, especially the flow field in the first stator. The stator blade with highly loaded is likely to cause a flow separation on the hub, so-called hub-corner separation. The flow mechanism of the hub-corner separation in the first stator is investigated in detail using a large-scale detached eddy simulation (DES) conducted for its full-annulus and full-stage with approximately 4.5 hundred million computational cells. The detailed analysis of complicated flow fields in the compressor is supported by data mining techniques. The data mining techniques applied in the present study include vortex identification based on the critical point theory and topological analysis of the limiting streamline pattern. The simulation results show that the flow field in the hub-corner separation is dominated by a tornado-type separation vortex. In the time averaged flow field, the hub-corner separation vortex rolls up from the hub wall, which is generated by the interaction between the mainstream flow, the leakage flow from the front partial clearance and the secondary flow across the blade passage toward the stator blade suction side. The hub-corner separation vortex suffers a vortex breakdown near the mid chord, where the high loss region due to the hub-corner separation expands drastically. In the rear part of the stator passage, a high loss region is migrated radially outward by the induced velocity of the hub-corner separation vortex. The flow field in the stator is influenced by the upstream and downstream rotors, which makes it difficult to understand the unsteady effects. The unsteady flow fields are analyzed by applying the phase-locked ensemble averaging technique. It is found from the phase-locked flow fields that the wake interaction from the upstream rotor has more influence on the stator flow field than the shock wave interaction from the downstream rotor. In the unsteady flow field, a focal-type separation also emerges on the blade suction surface, but it is periodically swept away by the wake passing of the upstream rotor. The separation vortex on the hub wall connects with the one on the blade suction surface, forming an arch-like vortex.

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