scholarly journals Detection of vaneless diffuser rotating stall by means of dynamic pressure sensors and acoustic measurements

2021 ◽  
Vol 312 ◽  
pp. 11007
Author(s):  
Luca Romani ◽  
Lorenzo Bosi ◽  
Alberto Baroni ◽  
Lorenzo Toni ◽  
Davide Biliotti ◽  
...  
Keyword(s):  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Rotating Stall ◽  
Accurate Estimation ◽  
Sufficient Information ◽  
Acoustic Measurements ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Ensemble Averaging

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors. Several techniques have been proposed to detect the stall onset; inter alia, few dynamic pressure probes have been shown to not only properly detect the phenomenon, but also reconstruct the stall characteristics after an ensemble averaging approach. The massive use of this technique in the field is, however, not a common practice yet. In the present study, the use of dynamic pressure probes has been combined with that of an environmental microphone to evaluate the prospects of this latter for a possible stall onset detection. To this end, experimental tests have been carried out in the experimental test rig of the Department of Industrial Engineering (DIEF) of Università degli Studi di Firenze. Results show that the microphone was able to distinguish the onset of rotating stall accurately and promptly, even though – differently from dynamic pressure sensors - it does not provide sufficient information to determine the characteristics of the stall pattern. On this basis, the use of acoustic measurements could find room for automatic detection of rotating stall onset.

scholarly journals Rotating Stall in Centrifugal Compressor Vaneless Diffuser: Experimental Analysis of Geometrical Parameters Influence on Phenomenon Evolution

2004 ◽  
Vol 10 (6) ◽  
pp. 433-442 ◽  
Author(s):  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Leonardo Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Fast Response ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Response Dynamic ◽  
Frequency Domains

The rotating stall is a key problem for achieving a good working range of a centrifugal compressor and a detailed understanding of the phenomenon is very important to anticipate and avoid it. Many experimental tests have been planned by the authors to investigate the influence on stall behavior of different geometrical configurations. A stage with a backward channel upstream, a 2-D impeller with a vaneless diffuser and a constant cross-section volute downstream, constitute the basic configuration. Several diffuser types with different widths, pinch shapes, and diffusion ratios were tested. The stage was instrumented with many fast response dynamic pressure sensors so as to characterize inception and evolution of the rotating stall. This kind of analysis was carried out both in time and in frequency domains. The methodology used and the results on phenomenon evolution will be presented and discussed in this article.

A Systematic Approach to Estimate the Impact of the Aerodynamic Force Induced by Rotating Stall in a Vaneless Diffuser on the Rotordynamic Behavior of Centrifugal Compressors

2013 ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Elisabetta Belardini ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Journal Bearings ◽  
Rotating Stall ◽  
Squeeze Film ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
The Impact

One of the main challenges of the present industrial research on centrifugal compressors is the need of extending the left margin of the operating range of the machines. As a result, interest is being paid in accurately evaluating the amplitude of the pressure fluctuations caused by rotating stall, which usually occurs prior to surge. The related aerodynamic force acting on the rotor can produce subsynchronous vibrations, which can prevent the machine to further operate, in case their amplitude is too high. These vibrations are often contained thanks to the stiffness of the oil journals. Centrifugal compressors design is, however, going towards alternative journal solutions having lower stiffness levels (e.g. Active Magnetic Bearings or Squeeze Film Dampers), which hence will be more sensitive to this kind of excitation: consequently, a more accurate estimation of the expected forces in presence of dynamic external forces like those connected to an aerodynamically unstable condition is needed to predict the vibration level and the compressor operability in similar conditions. Within this scenario, experimental tests were carried out on an industrial impeller operating at high peripheral Mach number. The dedicated test rig was equipped with several dynamic pressure probes that were inserted in the gas flow path; moreover, the rotor vibrations were constantly monitored with typical vibration probes located near the journal bearings. The pressure field induced by the rotating stall in the vaneless diffuser was reconstructed by means of an ensemble average approach, defining the amplitude and frequency of the external force acting on the impeller. The calculated force value was then included in the rotordynamic model of the test rig: the predicted vibrations on the bearings were compared with the measurements, showing satisfactory agreement. Finally, the prospects of the proposed approach are discussed by investigating the response of a real machine in high-pressure functioning when different choices of journal bearings are made.

Experimental Analysis of the Pressure Field Inside a Vaneless Diffuser From Rotating Stall Inception to Surge

2015 ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Dante Tommaso Rubino ◽  
Lorenzo Ferrari ◽  
Giovanni Ferrara
Keyword(s):  
Transient Analysis ◽  
Pressure Field ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Ensemble Averaging ◽  
Stall Inception ◽  
Key Points ◽  
Real Time Visualization

An accurate estimation of rotating stall is one of the key points for high-pressure centrifugal compressors, as it is often connected with the onset of detrimental subsynchronous vibrations which can prevent the machine from operating beyond this limit. With particular reference to vaneless diffuser rotating stall, the most common practice in industrial machines is to make use of a limited number of dynamic pressure probes to reconstruct the stall characteristics after an ensemble averaging approach. In this study, a 1:1 model of an industrial compressor stage was tested in a dedicated test rig and equipped with 24 pressure probes properly distributed along the diffuser circumference with the scope of providing a real-time visualization of the spatial pressure distribution within the diffuser. The results allowed the assessment of some important characteristics of the stall cells that were historically supposed based on averaged data, e.g. the cells rigidity. Moreover, the present study confirmed the existence of a stall pattern with two almost axisymmetric lobes. Finally, the transient analysis of both the stall inception and the surge onset was carried out, highlighting the flow field evolution in the diffuser under these conditions.

Experimental Analysis of the Pressure Field Inside a Vaneless Diffuser From Rotating Stall Inception to Surge

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Dante Tommaso Rubino ◽  
Lorenzo Ferrari ◽  
Giovanni Ferrara
Keyword(s):  
Transient Analysis ◽  
Pressure Field ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Ensemble Averaging ◽  
Stall Inception ◽  
Key Points ◽  
Real Time Visualization

An accurate estimation of rotating stall is one of the key points for high-pressure centrifugal compressors, as it is often connected with the onset of detrimental subsynchronous vibrations which can prevent the machine from operating beyond this limit. With particular reference to vaneless diffuser rotating stall, the most common practice in industrial machines is to make use of a limited number of dynamic pressure probes to reconstruct the stall characteristics after an ensemble averaging approach. In this study, a 1:1 model of an industrial compressor stage was tested in a dedicated test rig and equipped with 24 pressure probes properly distributed along the diffuser circumference with the scope of providing a real-time visualization of the spatial pressure distribution within the diffuser. The results allowed the assessment of some important characteristics of the stall cells that were historically supposed based on averaged data, e.g., the cells rigidity. Moreover, the present study confirmed the existence of a stall pattern with two almost axisymmetric lobes. Finally, the transient analysis of both the stall inception (SI) and the surge onset (SO) was carried out, highlighting the flow field evolution in the diffuser under these conditions.

A Systematic Approach to Estimate the Impact of the Aerodynamic Force Induced by Rotating Stall in a Vaneless Diffuser on the Rotordynamic Behavior of Centrifugal Compressors

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Elisabetta Belardini ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Journal Bearings ◽  
Rotating Stall ◽  
Squeeze Film ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
The Impact

One of the main challenges of the present industrial research on centrifugal compressors is the need for extending the left margin of the operating range of the machines. As a result, interest is being paid to accurately evaluating the amplitude of the pressure fluctuations caused by rotating stall, which usually occurs prior to surge. The related aerodynamic force acting on the rotor can produce subsynchronous vibrations, which can prevent the machine's further operation, in case their amplitude is too high. These vibrations are often contained due to the stiffness of the oil journals. Centrifugal compressor design is, however, going towards alternative journal solutions having lower stiffness levels (e.g., active magnetic bearings or squeeze film dampers), which will be more sensitive to this kind of excitation: consequently, a more accurate estimation of the expected forces in the presence of dynamic external forces such as those connected to an aerodynamically unstable condition is needed to predict the vibration level and the compressor operability in similar conditions. Within this scenario, experimental tests were carried out on industrial impellers operating at high peripheral Mach numbers. The dedicated test rig was equipped with several dynamic pressure probes that were inserted in the gas flow path; moreover, the rotor vibrations were constantly monitored with typical vibration probes located near the journal bearings. The pressure field induced by the rotating stall in the vaneless diffuser was reconstructed by means of an ensemble average approach, thus defining the amplitude and frequency of the external force acting on the impeller. The calculated force value was then included in the rotordynamic model of the test rig: the predicted vibrations on the bearings were compared with the measurements, showing satisfactory agreement. Moreover, the procedure was applied to two real multistage compressors, showing notable prediction capabilities in the description of rotating stall effects on the machine rotordynamics. Finally, the prospects of the proposed approach are discussed by investigating the response of a real machine in high-pressure functioning when different choices of journal bearings are made.

Some Guidelines for the Experimental Characterization of Vaneless Diffuser Rotating Stall in Stages of Industrial Centrifugal Compressors

2014 ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Marco Giachi ◽  
Elisabetta Belardini ◽  
Libero Tapinassi ◽  
...  
Keyword(s):  
Dynamic Pressure ◽  
Industrial Test ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Design Parameters ◽  
Accurate Estimation ◽  
Pressure Measurements ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Test Models

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors, as it is often connected with the onset of detrimental subsynchronous vibrations which can prevent the machine from operating beyond this limit. With particular reference to the vaneless diffuser stall, much research has been directed at investigating the physics of the phenomenon, the influence of the main design parameters and the prediction of the stall inception. Few of them, however, focused attention on the evaluation of the aerodynamic unbalance due to the induced pressure field in the diffuser, which, however, could provide a valuable contribution to both the identification of the actual operating conditions and the enhancement of the compressor operating range by a suitable choice of the control strategy. Although advanced experimental techniques have been successfully applied to the recognition of the stall pattern in a vaneless diffuser, the most suitable solution for a wider application in industrial test-models is based on dynamic pressure measurements by means of a reduced number of probes. Within this context, a procedure to transpose pressure measurements into the spatial pressure distribution was developed and validated on a wide set of industrial test-models. In this work, the main guidelines of the procedure are presented and discussed, with particular reference to signals analysis and manipulation as well as sensors positioning. Moreover, the prospects of using a higher number of sensors is analyzed and compared to standard solutions using a limited probes number.

Correlation Analysis of Multiple Sensors for Industrial Gas Turbine Compressor Blade Health Monitoring

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Brian Kestner ◽  
Tim Lieuwen ◽  
Chris Hill ◽  
Leonard Angello ◽  
Josh Barron ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Acoustic Pressure ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Compressor Blade ◽  
Blade Vibration ◽  
Multiple Sensors ◽  
Dynamic Pressure Measurements ◽  
Industrial Gas Turbine

This paper summarizes an analysis of data obtained from an instrumented compressor of an operational, heavy duty industrial gas turbine; the goal of the aforementioned analysis is to understand some of the fundamental drivers, which may lead to compressor blade vibration. Methodologies are needed to (1) understand the fundamental drivers of compressor blade vibration, (2) quantify the severity of “events,” which accelerate the likelihood of failure and reduce the remaining life of the blade, and (3) proactively detect when these issues are occurring so that the operator can take corrective action. The motivation for this analysis lies in understanding the correlations between different sensors, which may be used to measure the fundamental drivers and blade vibrations. In this study, a variety of dynamic data was acquired from an operating engine, including acoustic pressure, bearing vibration, tip timing, and traditional gas path measurements. The acoustic pressure sensors were installed on the first four compressor stages, while the tip timing was installed on the first stage only. These data show the presence of rotating stall instabilities in the front stages of the compressor, occurring during every startup and shutdown, and manifesting itself as increased amplitude oscillations in the dynamic pressure measurements, which are manifested in blade and bearing vibrations. The data that lead to these observations were acquired during several startup and shutdown events, and clearly show that the amplitude of these instabilities and the rpm at which they occur can vary substantially.

Acoustic Measurements of Perforated Liners in Hot and Pressurized Flow

2013 ◽  
Author(s):  
Claus Lahiri ◽  
Karsten Knobloch ◽  
Friedrich Bake ◽  
Lars Enghardt
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Numerical Models ◽  
Experimental Tests ◽  
Acoustic Measurements ◽  
Test Rig ◽  
Acoustic Data ◽  
Bias Flow ◽  
Acoustic Instabilities ◽  
Acoustic Losses

Thermo-acoustic instabilities in gas turbine combustors can prevent the implementation of modern combustion concepts, which are essential for higher efficiency and lower emissions. Perforated combustor liners, especially in combination with a bias flow through the liner, are able to suppress the instabilities by increasing the acoustic losses of the system. Some insight into the parameter dependencies of the acoustic absorption has been gained by means of atmospheric testing at ambient temperature. The next step towards realistic testing conditions is taking into account high temperature and high pressure, which increases the effort of the experimental tests and the complexity of their analysis significantly. Tests in a real combustor can serve as a quality check of a given liner design, but are not appropriate for parameter studies. So far, numerical models accurate enough to enable the design of hot stream liners are simply not available, so that the experimental investigation of the liner’s dependency on temperature and pressure is essential for the transfer of laboratory scale results to a real engine application. A new test rig has been designed to overcome these problems. The Hot Acoustic Test rig (HAT) enables the study of the influence of pressure and temperature on the damping performance in an acoustically well defined environment, although the high temperature and high pressure conditions are challenging in terms of accurate acoustic measurements. This paper introduces the Hot Acoustic Test rig with its features and limitations and shows first examples of test results. The focus lies on the hardware, instrumentation, and analysis techniques that are necessary to obtain high quality acoustic data in hot and pressurized flow environments.

The Effects of Radially Distorted Incident Flow on Performance of Axial-Flow Fans With Forward-Skewed Blades

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
B. Yang ◽  
Ch. G. Gu
Keyword(s):  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Axial Flow ◽  
Aerodynamic Characteristics ◽  
Rotating Stall ◽  
Incident Flow ◽  
Fan Performance ◽  
Beneficial Effects ◽  
Unsteady Aerodynamic ◽  
Overall Performance

In this study, experiments and numerical simulations were carried out to evaluate the effects of radially distorted incident flow on the performance of axial-flow fans, which were equipped with three kinds of forward-skewed blades. Loss coefficient and velocity components at exit section as well as overall performance are discussed, both at the design point and the lower mass flow rate point. Furthermore, rotating stall was also observed by use of three dynamic pressure sensors. All results reveal that there are beneficial effects of forward-skewed blades on the fan performance, but the fan performance and its unsteady aerodynamic characteristics are quite affected by the radially distorted incident flow.

Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1995 ◽  
Vol 117 (4) ◽  
pp. 585-592 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncˇl
Keyword(s):  
Development Program ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Disk Friction ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development program for centrifugal compressors are presented. Six-stage configurations with low flow coefficient were tested. The stages had channel width parameter b2/D2 = 0.01 and 0.03. For each value of the width parameter, three different impellers with inlet hub to outlet diameter ratio do/D2 = 0.3, 0.4, and 0.5 were designed. Test rig, instrumentation, and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing, and disk friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with deswirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

Sign in / Sign up

Export Citation Format

Share Document