Influence of Mach Number and Aerodynamic Loading on Rotating Instability in an Annular Compressor Cascade

2012 ◽  
Author(s):  
Christian Beselt ◽  
Dieter Peitsch
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
Steady Flow ◽  
Field Measurements ◽  
Sudden Increase ◽  
Compressor Cascade ◽  
Time Resolved ◽  
Aerodynamic Loading ◽  
Rotating Instability ◽  
Time Resolved Measurements

An experimental study was conducted to investigate the influence of Mach number and aerodynamic loading on Rotating Instability (RI). Investigations were performed on an annular compressor cascade with radial clearance at the hub. In addition to steady flow field measurements, time resolved measurements of static wall-pressure at the hub, close to the tip clearance, were performed. For a specific range of incidence angles, RI could be detected at all flow speeds (Ma = 0.2–0.7). Shortly before the inception of RI, a sudden increase in pressure loss coefficient and outflow angle was detected by steady flow field measurements. The time resolved measurements showed an abruptly broadband increase of amplitude in the frequency range, in which RI occurs at higher loadings. RI propagates with 25–33% of the circumferential component of the upstream flow speed. Furthermore it is possible to scale the power spectral density function of the unsteady data with Strouhal number.

Time Resolved Measurements in an Annular Compressor Cascade With High Aerodynamic Loading

2002 ◽  
Author(s):  
Jo¨rg Weidenfeller ◽  
Martin Lawerenz
Keyword(s):  
Pressure Sensors ◽  
Experimental Investigations ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Time Resolved ◽  
Blade Loading ◽  
Inlet Velocity ◽  
Aerodynamic Loading ◽  
Flow Phenomena ◽  
Time Resolved Measurements

In order to identify unsteady flow phenomena this paper presents experimental investigations inside an isolated compressor cascade under off-design conditions. The results of extensive time resolved measurements, which were performed by piezo-resistive pressure sensors and hot wire anemometry show an interaction of aerodynamic and acoustic mechanisms. For a certain operating range the measurements indicate, that vortices, caused by boundary layer separations, oscillate with the pipe mode of the test section. In addition so-called rotating instabilities occur at high blade loading. They rotate with 48% of the circumferential component of the inlet velocity.

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Unsteady Interaction ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Evaluating the Influence of Rotor-Casing Eccentricity on Turbine Efficiency Including Time-Resolved Flow Field Measurements

2021 ◽  
pp. 1-33
Author(s):  
Eric DeShong ◽  
Shawn Siroka ◽  
Reid A. Berdanier ◽  
Karen A. Thole
Keyword(s):  
Flow Field ◽  
Magnetic Levitation ◽  
Field Measurements ◽  
Tip Clearance ◽  
Time Resolved ◽  
Flow Angle ◽  
Turbine Efficiency ◽  
Eccentric Rotor ◽  
Blade Tip ◽  
Manufacturing Techniques

Abstract The clearance that exists between the casing and turbine blade tips is one of the key drivers of efficiency in gas turbine engines. For this reason, engine manufacturers utilize precise manufacturing techniques and may employ clearance control systems to minimize tip clearances to reduce associated losses. Despite these efforts, turbines typically exhibit some nominal casing ovality or rotor-casing eccentricity, and changes to blade tip clearance during operation commonly occur due to thermal and mechanical stresses. The present study investigates non-axisymmetric tip clearance effects by creating a rotor-casing eccentricity in a one-stage axial test turbine operating in a continuous-duration mode at engine relevant conditions with engine representative hardware. A magnetic levitation bearing system was leveraged to move the turbine shaft to vary the rotor-casing eccentricity without test section disassembly. The results of this study indicate that rotor-casing eccentricity does not affect overall turbine efficiency over the range that was tested, but does locally influence efficiency and the rotor exit flow field. Comparisons of flow angle and secondary flow kinetic energy agreed with previous studies and existing analytical methods, respectively. Collectively, these results indicate that tip clearance can be studied locally on an eccentric rotor.

Time resolved flow-field measurements of a turbulent mixing layer over a rectangular cavity

2010 ◽  
Vol 51 (1) ◽  
pp. 51-63 ◽  
Author(s):  
Shiyao Bian ◽  
James F. Driscoll ◽  
Brian R. Elbing ◽  
Steven L. Ceccio
Keyword(s):  
Flow Field ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Field Measurements ◽  
Rectangular Cavity ◽  
Time Resolved ◽  
Turbulent Mixing Layer

Time-Resolved Flow Field Measurements of Momentum Driven Pulsed, Transient Jets

2017 ◽  
Author(s):  
Zheng Zhang ◽  
Dhuree Seth ◽  
Sravan Kumar Artham ◽  
John G. Leishman ◽  
Ebenezer P. Gnanamanickam
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Time Resolved

Vortex-Wake-Blade Interaction in a Shrouded Axial Turbine

2004 ◽  
Author(s):  
J. Schlienger ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Interaction Mechanism ◽  
Leading Edge ◽  
Field Measurements ◽  
Second Phase ◽  
Time Resolved ◽  
Axial Turbine ◽  
High Loss ◽  
High Level

This paper presents the results of time-resolved flow field measurements of a multistage shrouded axial turbine. The unsteady interaction mechanism between the rotor’s secondary flow vortices, the rotor’s wake and the adjacent blading at the exit plane of the first turbine stage is of prime interest and analysed in detail. Three key phases are identified for one blade passing event. The first phase shows a quasi undisturbed convection of the rotor’s secondary flow field into the downstream stator. The second phase shows a migration of high loss fluid from the wake layer into the passage and horse-shoe vortices at the rotor hub section. The relative motion between the rotor and stator blades brings the two vortices closer to the wake layer and lets the flow features interact with each other. The third phase focuses on the rotor indigenous hub vortices that are bent and stretched around the stator’s leading edge. The signal analysis of the time-resolved flow field indicates a high level of unsteadiness at the stator’s pressure side. The associated unsteadiness within the flow field is evaluated and quantified on the basis of pitchwise averaged space-time diagrams. The obtained results are finally discussed and explained using two flow schematics within and at the end of the paper.

Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part I — Experimental Investigations

2014 ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analysed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. Part I of this two-part paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-PIV measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Experimental Analysis of Rotating Instability Using Hot Wire Triggered PIV and Wavelet Transform

2014 ◽  
Author(s):  
Georg Hermle ◽  
Martin Lawerenz
Keyword(s):  
Wavelet Transform ◽  
Temporal Resolution ◽  
Sampling Rate ◽  
Hot Wire ◽  
Mean Flow ◽  
Compressor Cascade ◽  
Time Resolved ◽  
Piv Measurements ◽  
Rotating Instability ◽  
Phase Angles

The authors present initial results of hot wire anemometry triggered PIV measurements of periodic effects in an annular compressor cascade. The investigations are focused on the unsteady effect of a rotating instability (RI) and are based on PIV measurements performed within the passage of a highly loaded annular compressor cascade. Simultaneously, hot wire measurements were conducted within the same passage. Post-processing the hot wire signal by means of the wavelet transform obtained the time resolved frequency spectrum as well as the time resolved phase angles. Such spectra allow filtering the PIV results to select only the results that feature the investigated effect of PI. The corresponding phase angles of the wavelet transform enable grouping the selected PIV results in phase classes. The average of each class gives the statistical mean flow field for the corresponding phase angle. Afterwards, the statistical mean period of the RI can be displayed by discrete ensemble averaged PIV results. The presented method improves the possible temporal resolution of PIV systems beyond their technical sampling rate. In the case presented, the statistical method leads to a temporal resolution corresponding to a sampling rate of 1.5 kHz, whereas the effective sampling rate of the PIV system used is 4 Hz. The possible resolution in time is only limited by the number of phase classes and accordingly by the number of PIV measurements.

Time-Resolved Measurements of the Unsteady Flow Field in a Single Stage Low Pressure Axial Compressor

2013 ◽  
Author(s):  
J. Sans ◽  
G. Dell’Era ◽  
J. Desset ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Time Resolved Measurements

The experimental investigation of the unsteady flow field in a highly loaded single stage low pressure axial compressor, also called a booster, is presented in this paper. The compressor design is representative of an advanced direct drive turbofan booster. Tests were performed on different speed lines at choke, design, and near stall, in the VKI-R4 closed loop compressor test rig. The rotor casing was instrumented with fast response pressure transducers to perform a detailed survey of the tip flow features. Simultaneous time-resolved measurements with fast response aerodynamic pressure probes were performed by radial and circumferential traverses to map the unsteady flow field at rotor and stator exit. The originality of this paper also resides in the fact that unsteady flow angle data are presented as the probe was used in a virtual 3-hole mode. The casing measurements allow to map the direction and extension of the tip leakage vortex. The flow path measurements show its extension at the exit of the rotor blade passage and its evolution as throttling is increased towards the compressor stability limit. The results are presented in terms of periodic and random fluctuations. These experimental results are combined to provide a three-dimensional view of the experimental flow field. They are discussed and compared to CFD simulations, showing that, in some regions, important features are not captured by the numerical model. In particular, the presence of a second wake has been observed in the unsteady yaw angle map at rotor exit. This uncommon feature is currently under further investigation.

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