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.

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.

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 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]

Stall Inception in a High-Speed Centrifugal Compressor During Speed Transients

2017 ◽  
Vol 139 (12) ◽  
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 subidle 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 (LE) 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.

Experimental and Numerical Investigation of the Unsteady Flow Field in a Vaned Diffuser of a High-Speed Centrifugal Compressor

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Klemens Vogel ◽  
Reza S. Abhari ◽  
Armin Zemp
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Operating Conditions ◽  
Wake Flow ◽  
Vaned Diffuser ◽  
Wide Range ◽  
The Impact

Vaned diffusers in centrifugal compressor stages are used to achieve higher stage pressure ratios, higher stage efficiencies, and more compact designs. The interaction of the stationary diffuser with the impeller can lead to resonant vibration with potentially devastating effects. This paper presents unsteady diffuser vane surface pressure measurements using in-house developed, flush mounted, fast response piezoresistive pressure transducers. The unsteady pressures were recorded for nine operating conditions, covering a wide range of the compressor map. Experimental work was complemented by 3D unsteady computational fluid dynamics (CFD) simulations using ansys cfx V12.1 to detail the unsteady diffuser aerodynamics. Pressure fluctuations of up to 34.4% of the inlet pressure were found. High pressure variations are present all along the vane and are not restricted to the leading edge region. Frequency analysis of the measured vane surface pressures show that reduced impeller loading, and the corresponding reduction of tip leakage fluid changes the characteristics of the fluctuations from a main blade count to a total blade count. The unsteady pressure fluctuations in the diffuser originate from three distinct locations. The impact of the jet-wake flow leaving the impeller results in high variation close to the leading edge. It was observed that CFD results overpredicted the amplitude of the pressure fluctuation on average by 62%.

Stall Inception in a High-Speed Centrifugal Compressor

2001 ◽  
Author(s):  
Jeong-Seek Kang ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Good Method ◽  
Fast Response ◽  
Stall Inception ◽  
Pressure Transducers ◽  
Stall Warning ◽  
Response Pressure ◽  
Set Up ◽  
Warning Time

Stall inception in a high-speed centrifugal compressor has been examined. The main objective was to find stall precursor and to develop a reliable stall warning method. Eight equally spaced fast-response pressure transducers in the inducer detected the spatial structure of small amplitude perturbations, via spatial Fourier transform, as stall is approached. Near the stall inception point, the phase of spatial Fourier coefficients increased linearly with the speed of impeller rotation for several impeller revolutions at all test speeds, and the spectrum at impeller frequency increased as stall is approached. This is the clear evidence that the impeller frequency participates in the stalling process. For stall warning, a method which uses the spectrum at impeller frequency is suggested. The use of spectrum at impeller frequency as a stall warning method showed a warning time of about two hundreds impeller revolutions. This method uses only one sensor that it has made the stall warning method more useful. And the well-known traveling wave energy method proved to be a good method for stall warning also in a high-speed centrifugal compressor. The warning time was about one hundred impeller revolutions at lower speeds, and about one thousand impeller revolutions at higher speeds. The stall warning methods used here were found to be robust and reliable. Therefore, it seems to be promising to set up a reliable stall avoidance control based on this analysis.

Unsteady Entropy Measurements in a High-Speed Radial Compressor

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. Mansour ◽  
N. Chokani ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Thin Film ◽  
Relative Entropy ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Measurement Techniques ◽  
Flow Region ◽  
Fast Response ◽  
Wake Flow ◽  
Time Dependent ◽  
Operating Condition

The time-dependent relative entropy field at the impeller exit of a centrifugal compressor is measured. This study is part of a broader effort to develop comprehensive measurement techniques that can be applied in the harsh environment of turbomachines. A miniature unsteady entropy probe (diameter of 1.8 mm) is designed and constructed in the present study. The unsteady entropy probe has two components: a one-sensor fast-response aerodynamic probe and a pair of thin-film gauges. The time-dependent total pressure and total temperature are measured from the fast-response aerodynamic probe and pair of thin-film gauges, respectively. The time-dependent relative entropy derived from these two measurements has a bandwidth of 40 kHz and an uncertainty of ±2 J/kg. The measurements show that for operating Condition A, φ=0.059 and ψ=0.478, the impeller exit flowfield is highly three dimensional. Adjacent to the shroud there are high levels of relative entropy and at the midspan there are low and moderate levels. Independent measurements made with a two-sensor aerodynamic probe show that the high velocity of the flow relative to the casing is responsible for the high relative entropy levels at the shroud. On the other hand, at the midspan, a loss free, jet flow region and a channel wake flow of moderate mixing characterize the flowfield. At both the shroud and midspan, there are strong circumferential variations in the relative entropy. These circumferential variations are much reduced when the centrifugal compressor is operated at operating Condition B, φ=0.0365 and ψ=0.54, near the onset of stall. In this condition, the impeller exit flowfield is less highly skewed; however, the time-averaged relative entropy is higher than at the operating Condition A. The relative entropy measurements with the unsteady entropy probe are thus complementary to other measurements, and more clearly document the losses in the centrifugal compressor.

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