Closure to “Discussion of ‘On the Development and Application of the Fast-Response Aerodynamic Probe System for Turbomachines—Part 3: Comparison of Averaging Methods Applied to Centrifugal Compressor Measurements’ ” [ASME J. Turbomach., 122, No. 3, p. 527–535 (2000)]

2000 ◽  
Vol 122 (3) ◽  
pp. 536-536
Author(s):  
Peter Kupferschmied
Keyword(s):  
Centrifugal Compressor ◽  
Fast Response ◽  
Averaging Methods ◽  
Probe System

[S0889-504X(00)01903-6]

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]

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]

On the Development and Application of the Fast-Response Aerodynamic Probe System in Turbomachines—Part 1: The Measurement System

1999 ◽  
Vol 122 (3) ◽  
pp. 505-516 ◽  
Author(s):  
Peter Kupferschmied ◽  
Pascal Ko¨ppel ◽  
Christian Roduner ◽  
Georg Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
Measurement System ◽  
Axial Flow ◽  
Fast Response ◽  
Data Evaluation ◽  
Sensor Calibration ◽  
Mean Flow ◽  
Efficient Operation ◽  
Probe System ◽  
Probe Calibration

This contribution gives an overview of the current state, performance, and limitations of the fast-response aerodynamic probe measurement system developed at the Turbomachinery Lab of the ETH Zurich. In particular, the following topics are addressed:  • Probe technology: Miniature probes with tip diameter ranging from 0.84 to 1.80 mm (one-sensor and three-sensor probes, respectively) have been developed. New technologies derived from microelectronics and micromechanics have been used to achieve an adequate packaging of the microsensor chips used. Both the sensor packaging and the sensor calibration (time-independent and time-dependent) are crucial issues for the DC accuracy of any measurement.  • Aerodynamic probe calibration: The methods used for the sensor calibration and the aerodynamic probe calibration, the pertinent automated test facilities, and the processing of the output data are briefly presented. Since these miniature probes are also capable of measuring the mean flow temperature, aspects related to the effective recovery factor and the self-heating of the probe tip are treated and some recommendations related to sensor selection are given.  • Measurement system and data evaluation: The early measurement chain described in Gossweiler et al. (1995) has evolved into the fast-response aerodynamic probe system. This automatic system incorporates dedicated measurement concepts for a higher accuracy and a more efficient operation in terms of time and failures. An overview of the data evaluation process is given. The fast-response aerodynamic probe system has been tested in real-sized turbomachines under industrial conditions within the temperature limits of 140°C imposed by the sensor technology (axial-flow turbofan compressor, axial-flow turbine, centrifugal compressor). These applications confirmed the potential of the system and encouraged its further development. Now, the system is routinely used in the facilities of the Turbomachinery Lab and in occasional measurement campaigns in other laboratories. Part 2 of this contribution (Roduner et al.) will focus on the application of the fast-response aerodynamic probe system in a transonic centrifugal compressor of the ETH Turbomachinery Laboratory, while Part 3 (Ko¨ppel et al.) treats more sophisticated data analysis methods. [S0889-504X(00)01003-5]

Comparison of Measurement Data at the Impeller Exit of a Centrifugal Compressor Measured With Both Pneumatic and Fast-Response Probes

1999 ◽  
Vol 121 (3) ◽  
pp. 609-618 ◽  
Author(s):  
C. Roduner ◽  
P. Ko¨ppel ◽  
P. Kupferschmied ◽  
G. Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Measurement Data ◽  
Fast Response ◽  
Angle Distribution ◽  
Present Contribution ◽  
Velocity Magnitude ◽  
Speed Flow ◽  
Measurement Results ◽  
Probe System

The main goal of these investigations was the refined measurement of unsteady high-speed flow in a centrifugal compressor using the advanced FRAP® fast-response aerodynamic probe system. The present contribution focuses on the impeller exit region and shows critical comparisons between fast-response (time-resolving) and conventional pneumatic probe measurement results. Three probes of identical external geometry (one fast and two pneumatic) were used to perform wall-to-wall traverses close to the impeller exit. The data shown refer to a single running condition near the best point of the stage. The mass flow obtained from different probe measurements and from the standard orifice measurement were compared. Stage work obtained from temperature rise measured with a FRAP® probe and from impeller outlet velocity vectors fields by using Euler’s turbine equation are presented. The comparison in terms of velocity magnitude and angle distribution is quite satisfactory, indicating the superior DC measurement capabilities of the fast-response probe system.

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.

Comparison of Measurement Data at the Impeller Exit of a Centrifugal Compressor Measured With Both Pneumatic and Fast-Response Probes

1998 ◽  
Author(s):  
C. Roduner ◽  
P. Köppel ◽  
P. Kupferschmied ◽  
G. Gyarmathy
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Measurement Data ◽  
Fast Response ◽  
Angle Distribution ◽  
Present Contribution ◽  
Velocity Magnitude ◽  
Speed Flow ◽  
Measurement Results ◽  
Probe System

The main goal of these investigations was the refined measurement of unsteady high-speed flow in a centrifugal compressor by using the advanced FRAP® fast-response aerodynamic probe system. The present contribution focusses on the impeller exit region and shows critical comparisons between fast-response (time-resolving) and conventional pneumatic probe measurement results. Three probes of identical external geometry (1 fast and 2 pneumatic) were used to perform wall-to-wall traverses close to the impeller exit. The data shown refer to a single running condition near the best point of the stage. The mass flow obtained from different probe measurements and from the standard orifice measurement were compared. Stage work obtained from temperature rise measured with a FRAP® probe and from impeller outlet velocity vectors fields by using Euler’s turbine equation are presented. The comparison in terms of velocity magnitude and angle distribution is quite satifactory, indicating the superior DC measurement capabilities of the fast-response probe system.

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.

Prediction and Validation of the Transient Pressure Field in a Centrifugal Compressor With Vaned Diffuser for the Application in High Cycle Fatigue Stress Estimations

2021 ◽  
Author(s):  
Gökay Bacakci ◽  
Friedrich Fröhlig ◽  
Lukas Stuhldreier ◽  
Johannes Deutsch ◽  
Peter Jeschke
Keyword(s):  
Centrifugal Compressor ◽  
High Cycle Fatigue ◽  
Pressure Field ◽  
Transient Flow ◽  
Pressure Fluctuations ◽  
Fast Response ◽  
Pressure Measurements ◽  
Cycle Fatigue ◽  
Transient Pressure ◽  
Response Pressure

Abstract In this paper, the transient pressure field in a centrifugal compressor is predicted by the Nonlinear Harmonic (NLH) method, as well as the unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations and validated by transient pressure measurements. The accurate prediction of these pressure fluctuations is crucial, because they have a significant influence on the High-Cycle-Fatigue (HCF) behavior in turbomachinery applications. As the first step, excited and non-excited rotational speeds, caused by rotor-stator interactions, are identified by modal analysis performed on a single segment impeller assembly. In order to eliminate any additional pressure fluctuations caused by blade vibrations, three non-excited operating points at different rotational speed levels are selected for the transient flow simulations. The transient pressure fields predicted by these methods are validated by transient pressure measurements at three circumferentially different locations on the impeller shroud. A study of the modeling of these fast-response pressure probes in numerical calculations also falls within the scope of this work in order to identify its effect on the transient pressure amplitudes. The results of the numerical calculations and measurements are compared in the frequency domain by performing Fast-Fourier Transformations (FFT) and Short-Time Fourier Transformations (STFT) on the numerical and experimental data respectively. It is shown that the transient pressure field in a single staged centrifugal compressor is calculated accurately by both of the numerical methods in comparison to the transient flow measurements. This paper demonstrates that the numerical modeling of the fast-response pressure sensors has a significant impact on the unsteady pressure amplitudes, which needs to be taken into account for a reliable experimental validation process.

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