On the Development and Application of the Fast-Response Aerodynamic Probe System in Turbomachines—Part 3: Comparison of Averaging Methods Applied to Centrifugal Compressor Measurements

1999 ◽  
Vol 122 (3) ◽  
pp. 527-535 ◽  
Author(s):  
Pascal Ko¨ppel ◽  
Christian Roduner ◽  
Peter Kupferschmied ◽  
Georg Gyarmathy
Keyword(s):  
Data Processing ◽  
Centrifugal Compressor ◽  
Fast Response ◽  
Rotating Stall ◽  
Time Averaging ◽  
Simple Arithmetic ◽  
Flow Measurements ◽  
Time Resolved ◽  
Averaging Methods ◽  
Probe System

Typically several hundred million data points arise from a comprehensive measurement campaign carried out in a centrifugal compressor test rig with the fast-response aerodynamic probe system (see Part 1). In order to obtain a maximum of information about the unsteady flow at any position in this turbomachine, the time-resolved data processing method has to be optimized. In contrast to the standard time-averaged flow measurements with pneumatic probes, the objective of fast-response aerodynamic probe measurements and of data processing is to extract novel information about crucial unsteady phenomena like turbulence, row-to-row interaction, modal or rotating stall, leakage flow effects, etc. In such cases, the simultaneous measurement of static and total pressures and flow vectors is of particular interest. Novel information means the analysis of averaged and time-resolved (wavelet) spectra, autocorrelations or time averages properly conserving physical fluxes, etc. Different averaging methods are applied to compress the time-dependent data measured by a one-sensor-probe (see Part 2) in a centrifugal compressor. Such results could be used for comparison with pneumatic sensor measurements and CFD calculations. The comparison of averaging methods includes the averaging theories by Traupel and by Dzung, which are compared to simple arithmetic time averaging. From there the specific stage work is calculated. In analyzing the time dependency, several ensemble-averaging procedures for flow pressure and velocity are utilized for separating deterministic from stochastic fluctuations, extracting blade row finger prints or investigating low-frequency surge type fluctuations. With respect to the selection and overall optimization of data processing methods, an overview of generic tools is given and the modularity of the processing procedures is discussed. [S0889-504X(00)01203-4]

scholarly journals On the Development and Application of the FRAP® (Fast-Response Aerodynamic Probe) System in Turbomachines: Part 3 — Comparison of Averaging Methods Applied to Centrifugal Compressor Measurements

1999 ◽  
Author(s):  
Pascal Köppel ◽  
Christian Roduner ◽  
Peter Kupferschmied ◽  
Georg Gyarmathy
Keyword(s):  
Data Processing ◽  
Centrifugal Compressor ◽  
Low Frequency ◽  
Rotating Stall ◽  
Time Averaging ◽  
Ensemble Averaging ◽  
Simple Arithmetic ◽  
Flow Measurements ◽  
Time Resolved ◽  
Averaging Methods

Typically several hundred million data points arise from a comprehensive measurement campaign carried out in a centrifugal compressor test rig with the FRAP® system (see Part 1). In order to obtain a maximum of information about the unsteady flow at any position in this turbo machine the time-resolved data processing method has to be optimized. In contrast to the standard time-averaged flow measurements with pneumatic probes, the objective of FRAP® measurements and of data processing is to extract novel information about crucial unsteady phenomena like turbulence, row-to-row interaction, modal or rotating stall, leakage flow effects etc. In such cases the simultaneous measurement of static and total pressures and flow vectors is of particular interest. Novel information means the analysis of averaged and time-resolved (wavelet) spectra, autocorrelations or time averages properly conserving physical fluxes, etc.. Different averaging methods are applied to compress the time dependent data measured by a 1-sensor-probe (see Part 2) in a centrifugal compressor. Such results could be used for comparison with pneumatic sensor measurements and CFD calculations. The comparison of averaging methods includes the averaging theories by Traupel and by Dzung which are compared to simple arithmetic time averaging. From there the specific stage work is calculated. In analysing the time dependency several ensemble-averaging procedures for flow pressure and velocity are utilized for separating deterministic from stochastic fluctuations, extracting blade row finger prints or investigating low-frequency surge type fluctuations. With respect to the selection and overall optimization of data processing methods an overview of generic tools is given and the modularity of the processing procedures is discussed.

On the Development and Application of the Fast-Response Aerodynamic Probe System in Turbomachines—Part 2: Flow, Surge, and Stall in a Centrifugal Compressor

1999 ◽  
Vol 122 (3) ◽  
pp. 517-526 ◽  
Author(s):  
Christian Roduner ◽  
Peter Kupferschmied ◽  
Pascal Ko¨ppel ◽  
Georg Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
Fast Response ◽  
Rotating Stall ◽  
Period Length ◽  
Absolute Pressure ◽  
Time Behavior ◽  
Ensemble Averaging ◽  
Vaned Diffuser ◽  
Averaging Methods ◽  
Probe System

The present paper, Part 2 of a trilogy, is primarily focussed on demonstrating the capabilities of a fast-response aerodynamic probe system configuration based on the simplest type of fast-response probe. A single cylindrical probe equipped with a single pressure sensor is used to measure absolute pressure and both velocity components in an essentially two-dimensional flow field. The probe is used in the pseudo-three-sensor mode (see Part 1). It is demonstrated that such a one-sensor probe is able to measure high-frequency rotor-governed systematic fluctuations (like blade-to-blade phenomena) alone or in combination with flow-governed low-frequency fluctuations as rotating stall (RS) and mild surge (MS). However, three-sensor probes would be needed to measure stochastic (turbulence-related) or other aperiodic velocity transients. The data shown refer to the impeller exit and the vaned diffuser of a single-stage high-subsonic centrifugal compressor. Wall-to-wall probe traverses were performed at the impeller exit and different positions along the vaned diffuser for different running conditions. The centrifugal compressor was operated under stable as well as unstable (pulsating or stalled) running conditions. The turbomachinery-oriented interpretation of these unsteady flow data is a second focus of the paper. A refined analysis of the time-resolved data will be performed in Part 3, where different spatial/temporal averaging methods are compared. Two different averaging methods were used for the data evaluation: impeller-based ensemble-averaging for blade-to-blade systematic fluctuations (with constant period length at a constant shaft speed), and flow-based class averaging for the relatively slow MS and RS with slightly variable period length. Due to the ability of fast-response probes to simultaneously measure velocity components and total and static pressure, interesting insights can be obtained into impeller and diffuser channel flow structures as well as into the time behavior of such large-domain phenomena as RS and MS. [S0889-504X(00)01103-X]

scholarly journals On the Development and Application of the FRAP® (Fast-Response Aerodynamic Probe) System in Turbomachines: Part 2 — Flow, Surge and Stall in a Centrifugal Compressor

1999 ◽  
Author(s):  
Christian Roduner ◽  
Peter Kupferschmied ◽  
Pascal Köppel ◽  
George Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
Low Frequency ◽  
Fast Response ◽  
Rotating Stall ◽  
Period Length ◽  
Absolute Pressure ◽  
Time Behavior ◽  
Ensemble Averaging ◽  
Vaned Diffuser ◽  
Averaging Methods

The present paper, Part 2 of a trilogy, is primarily focussed on demonstrating the capabilities of a FRAP® system configuration based on the simplest type of fast-response probe. A single cylindrical probe equipped with a single pressure sensor is used to measure absolute pressure and both velocity components in an essentially two-dimensional flow field. The probe is used in the pseudo-3-sensor mode (see Part 1). It is demonstrated that such a 1-sensor probe is able to measure high-frequency rotor-governed systematic fluctuations (like blade-to-blade phenomena) alone or in combination with flow-governed low-frequency fluctuations as rotating stall (RS) and mild surge (MS). However 3-sensor probes would be needed to measure stochastic (turbulence-related) or other aperiodic velocity transients. The data shown refer to the impeller exit and the vaned diffuser of a single-stage high-subsonic centrifugal compressor. Wall-to-wall probe traverses were performed at the impeller exit and different positions along the vaned diffuser for different running conditions. The centrifugal compressor was operated under stable as well as under unstable (pulsating or stalled) running conditions. The turbomachinery oriented interpretation of these unsteady flow data is a second focus of the paper. A refined analysis of the time-resolved data will be done in Part 3 where different spatial/temporal averaging methods are compared. Two different averaging methods were used for the data evaluation. Impeller based ensemble averaging for blade-to-blade systematic fluctuations (with constant period length at a constant shaft speed) and flow-based class averaging for the relatively slow MS and RS with slightly variable period length. Due to the ability of fast-response probes to simultaneously measure velocity components as well as total and static pressure, interesting insights can be obtained into impeller and diffuser channel flow structures as well as into the time behavior of large-domain phenomena as RS and MS.

Effect of Tip Clearance on the Flow and Performance of a Centrifugal Compressor

2003 ◽  
Author(s):  
Soon-Sam Hong ◽  
Matthias Schleer ◽  
Reza S. Abhari
Keyword(s):  
Centrifugal Compressor ◽  
Fast Response ◽  
Tip Clearance ◽  
Wake Region ◽  
Clearance Ratio ◽  
Flow Measurements ◽  
Time Resolved ◽  
Compressor Impeller ◽  
Blade Tip ◽  
And Performance

To see the tip clearance effect on a centrifugal compressor, time-resolved flow measurements were carried out at the discharge of a centrifugal compressor impeller, which is 30 deg back swept from radial and operated at the blade tip speed of 260 m/s. Tested were six cases of tip clearance ratio ranged from 0.06 to 0.21. A fast response aerodynamic probe equipped with a single pressure sensor was used for the flow measurements. From the distribution of time-resolved relative velocity, the jet-wake structure was observed. The wake downstream of the splitter blade was located in the shroud-suction corner, but that downstream of the full blade was in the mid-shroud. By increasing the tip clearance, the wake region was increased and the deficit of the relative total pressure governed the wake region, therefore, the loss was enlarged.

Stall Inception in a High Speed Centrifugal Compressor During Speed Transients

2017 ◽  
Author(s):  
Fangyuan Lou ◽  
John C. Fabian ◽  
Nicole L. Key
Keyword(s):  
Heat Transfer ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Flow Instability ◽  
Leading Edge ◽  
Fast Response ◽  
Rotating Stall ◽  
Transient Performance ◽  
Stall Inception ◽  
Pressure Transducers

The inception and evolution of rotating stall in a high-speed centrifugal compressor are characterized during speed transients. Experiments were performed in the Single Stage Centrifugal Compressor (SSCC) facility at Purdue University and include speed transients from sub-idle to full speed at different throttle settings while collecting transient performance data. Results show a substantial difference in the compressor transient performance for accelerations versus decelerations. This difference is associated with the heat transfer between the flow and the hardware. The heat transfer from the hardware to the flow during the decelerations locates the compressor operating condition closer to the surge line and results in a significant reduction in surge margin during decelerations. Additionally, data were acquired from fast-response pressure transducers along the impeller shroud, in the vaneless space, and along the diffuser passages. Two different patterns of flow instabilities, including mild surge and short-length-scale rotating stall, are observed during the decelerations. The instability starts with a small pressure perturbation at the impeller leading edge and quickly develops into a single-lobe rotating stall burst. The stall cell propagates in the direction opposite of impeller rotation at approximately one third of the rotor speed. The rotating stall bursts are observed in both the impeller and diffuser, with the largest magnitudes near the diffuser throat. Furthermore, the flow instability develops into a continuous high frequency stall and remains in the fully developed stall condition.

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.

Impeller Rotating Stall as a Trigger for the Transition From Mild to Deep Surge in a Subsonic Centrifugal Compressor

1993 ◽  
Author(s):  
Beat Ribi ◽  
Georg Gyarmathy
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Critical Value ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
Compressor Map ◽  
Operating Points

The present paper concerns the transition from mild to deep surge in a single stage centrifugal compressor using a vaned diffuser. Time-resolved measurements of the mass flow rate and the static pressures at various locations of the compressor were analyzed for different diffuser geometries and different operating points in the compressor map. When the throttle valve was gradually closed at an impeller tip Mach number (Mu) above 0.4, the compressor showed first mild and then deep surge whereas at Mu=0.4 rotating stall was the dominant instability. This single-cell rotating stall was identified to be caused by the impeller. During mild surge at higher Mach numbers the instantaneous flow and pressure traces showed that the overall flow at the stage inlet intermittently dropped below the critical value associated with the occurence of impeller rotating stall. Rotating stall appeared for a while but vanished as soon as the flow increased again. With further throttling, however, a threshold was reached at which rotating stall triggered deep surge. The results show that triggering only occurred if the flow deficiency causing rotating stall persisted long enough to permit the stall cell to make at least one or two revolutions.

Time-resolved flow measurements with fast-response aerodynamic probes in turbomachines

2000 ◽  
Vol 11 (7) ◽  
pp. 1036-1054 ◽  
Author(s):  
Peter Kupferschmied ◽  
Pascal Köppel ◽  
William Gizzi ◽  
Christian Roduner ◽  
Georg Gyarmathy
Keyword(s):  
Fast Response ◽  
Flow Measurements ◽  
Time Resolved
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