Unsteady Pressure Measurements in a Single Stage Low Pressure Axial Compressor: Tip Vortex Flow and Stall Inception

2009 ◽  
Author(s):  
J. F. Brouckaert ◽  
N. Van de Wyer ◽  
B. Farkas ◽  
F. Ullmann ◽  
J. Desset ◽  
...  
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Pressure Probe ◽  
Pressure Measurements ◽  
Stall Inception ◽  
Unsteady Pressure ◽  
Unsteady Pressure Measurements

The experimental investigation of the unsteady flow field in a single stage low pressure axial compressor designed for a counter-rotating turbofan engine architecture is presented in this paper. The rotor casing was instrumented with fast response pressure transducers to perform a detailed survey of the tip flow features during stable operation, near stall and during stall. Tests were performed at two different Reynolds numbers representative of cruise and take-off conditions in the VKI-R4 closed loop compressor test rig. Simultaneous time-resolved measurements with a miniature fast response total pressure probe were performed by radial traverses at the rotor exit to support the tip flow field investigation. 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. These experimental results are discussed and compared to CFD simulations, showing good agreement. Stall inception and rotating stall patterns are investigated as well and described in this paper. They are based both on hot wire measurements and on the casing unsteady pressure measurements.

Experimental Investigation of the Steady and Unsteady Flow Field in a Single Stage Low Pressure Axial Compressor With a Circumferential Groove Casing Treatment

2010 ◽  
Author(s):  
N. Van de Wyer ◽  
B. Farkas ◽  
J. Desset ◽  
J. F. Brouckaert ◽  
J.-F. Thomas ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Unsteady Flow ◽  
Axial Compressor ◽  
Low Pressure ◽  
Fast Response ◽  
Single Stage ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Circumferential Groove

This paper deals with the experimental investigation of the influence of a circumferential groove casing treatment on the performance and stability margin of a single stage low pressure axial compressor. The design of the compressor stage is representative of a booster stage for the new counter-rotating turbofan engine architecture and is characterized by unusually high loading and flow coefficients. The choice of the circumferential groove is described on the basis of a numerical parametric study on the number of grooves, the axial position, the depth and width of the groove. The experiments were performed at a Reynolds number corresponding to cruise conditions in the von Karman Institute closed loop high speed compressor test rig R4. The detailed performance characterization of the compressor stage with casing treatment was mapped at four operating points from choke to stall at design speed. The compressor stall limit was determined at several other off-design speeds. Detailed steady and unsteady measurements were performed to determine the flow field characteristics of the rotor and of the complete stage. Conventional pressure, temperature and directional probes were used along with fast response pressure sensors in the rotor casing and in the groove. Simultaneous traverses with a fast response total pressure probe were used to map the unsteady flow field at the rotor exit allowing an experimental capture of the tip leakage vortex path and extension through the rotor passage. A comparison of the flow features with and without casing treatment was performed and the results are discussed against 3D viscous computational predictions. The casing treatment did not present any improvement of the compressor stall margin but no significant performance degradation was observed either. The CFD predictions showed a good agreement with the measurements and their analysis supported the experimental results.

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.

scholarly journals Unsteady Transition Characteristics of Rotating Stall in a Single-Stage Transonic Axial Compressor

1999 ◽  
Author(s):  
Chaoqun Nie ◽  
Jingyi Chen ◽  
Xingmin Gui ◽  
Qing Yu ◽  
Tongqing Wang
Keyword(s):  
Flow Field ◽  
Dynamic Behavior ◽  
Frequency Spectrum ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Single Stage ◽  
Frequency Spectra ◽  
Stall Inception ◽  
Blade Passage ◽  
Transonic Axial Compressor

The unsteady transition characteristics of rotating stall have been studied experimentally in a single-stage transonic axial compressor. Three tested conditions in the near design and below design speed range, at tip relative Mach numbers from 1.26 to 1.0, were performed. The characteristics of rotating stall were studied by its dynamic behavior on the scale of compressor circumference and also by the flow field details in the blade passage. The dynamic behavior was analyzed by the technique of successive frequency spectrum and the flow field details were studied through internal transient pressure patterns in the blade passage plotted by the dynamic pressure data measured on the compressor shroud. It has been shown that intermittent pre-stall perturbations are evident for all the tested speeds and distinct by the different time and length scale of their existence. These are also interpreted by the difference of pressure loading and shock structure visualized in the pressure plots in the blade passage during stall inception. The pre-stall perturbations, with rather scattered frequency spectra, grow into fully developed stall abruptly. Nevertheless, the frequency spectrum of rotating stall falls into constant fraction of the frequency of compressor rotation for all the tested conditions. The increasing trend of the amplitude of pressure oscillation of rotating stall while gathering at its frequency spectrum could be detected in the stage of stall inception. Based on these two observations, there is a possibility of warning the stall precursors even for the high speed transonic compressor like the one tested in this paper.

Identification of Spinning Mode in the Unsteady Flow Field of a Low Pressure Turbine

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Davide Lengani ◽  
Berardo Paradiso ◽  
Andreas Marn ◽  
Emil Göttlich
Keyword(s):  
Flow Field ◽  
Guide Vane ◽  
Low Pressure ◽  
Fast Response ◽  
Turbine Rotor ◽  
Pressure Probe ◽  
Model Parameters ◽  
Time Resolved ◽  
Flow Angle ◽  
Lp Turbine

This paper presents an experimental investigation of the vane-blade unsteady interaction in an unshrouded low pressure (LP) turbine research rig with uneven blade/vane count (72 blades and 96 vanes). The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put on the adjustment of all relevant model parameters. In particular blade count ratio, airfoil aspect ratio, reduced mass flow, reduced speed, and Mach and Reynolds numbers were chosen to reproduce the full scale LP turbine at take off condition. Measurements by means of a fast-response pressure probe were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The probe has been fully traversed both in circumferential and radial traverses. The rotor exit is characterized by strong perturbations due to the tip leakage vortex and the rotor blade wake. Circumferential nonuniformities due to the upstream vane wake and to the downstream exit guide vane potential effects are also identified. Furthermore, in the present configuration with an uneven blade/vane count the nonuniformities due to the stator and rotor row are misaligned along the whole turbine circumference and create a spinning mode that rotates in direction opposite to the rotor at a high frequency. The aeroacoustic theory is employed to explain such further unsteady pattern. The variations of the exit flow angle within a cycle of such pattern are not negligible and almost comparable to the ones within the blade passing period.

scholarly journals Time-resolved flow field investigation in an industrial centrifugal compressor application involving TR-PIV synchronized with unsteady pressure measurements

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Joachim Klinner ◽  
Melanie Voges ◽  
Michael Schroll ◽  
Alessandro Bassetti ◽  
Christian Willert
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Laser System ◽  
Power Spectra ◽  
Field Investigation ◽  
High Repetition Rate ◽  
Pressure Measurements ◽  
Time Resolved ◽  
Unsteady Pressure ◽  
Unsteady Pressure Measurements

We report on combined velocity and unsteady pressure measurements obtained on an radial compressor with vaneless diffuser and asymmetric volute. Time-resolved PIV recordings were acquired at 26 kHz both upstream of the impeller as well as within the vaneless diffusor at several rotation speeds at clean conditions and prior to the onset of instabilities within the rotor. The velocity data was acquired with a high-repetition rate, double-pulse laser system consisting of two combined DPSS lasers and a high-speed CMOS camera that was synchronized with multi-point unsteady pressure measurements. Details on the facility, the utilized instrumentation and data processing are provided with particular focus on the spectral and coherence analysis. Power spectra obtained from time records of the inlet velocity and unsteady pressure reveal an increase of low-frequency fluctuations below the blade passing frequency and the occurrence of a mode-locked behaviour indicating the presence of rotating instabilities. High levels of correlation between velocity and unsteady pressure signals not only confirm the temporal coherence of the acquired data but also reveal a direct coupling between flow field and pressure signature that is more prominent upstream of the rotor rather than in the diffusor.

Unsteady Flow Interactions Between a High- and Low-Pressure Turbine: Part 2 — Rotor-Synchronic Averaging and Proper Orthogonal Decomposition of the Unsteady Flow Fields

2019 ◽  
Author(s):  
M. Dellacasagrande ◽  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Proper Orthogonal Decomposition ◽  
Low Pressure ◽  
Fast Response ◽  
Orthogonal Decomposition ◽  
Pressure Probe ◽  
Low Pressure Turbine ◽  
Aerodynamic Pressure ◽  
Proper Orthogonal

Abstract This paper, the second of two parts, presents an experimental investigation of the unsteady flow field evolving in a two-stage two-spool test turbine facility. The experimental setup, which was designed to reproduce the operating condition of modern commercial aero-engines, consists of a high-pressure turbine (HPT) stage followed by a turbine center frame (TCF) with non-turning struts, and a co-rotating low-pressure turbine (LPT) stage. Measurements carried out with a fast-response aerodynamic pressure probe (FRAPP) were post-processed to describe the unsteady evolution of the flow downstream of the HPT rotor, through the TCF duct, and at the exit of the LPT stage. The time-resolved results presented in the first part of this paper show that deterministic fluctuations due to both rotors characterize the flow field downstream of the LPT. In order to characterize the deterministic unsteadiness induced by all the components constituting the turbine facility (HPT, TCF and LPT) and their interactions, measurements were carried out in three different planes located downstream of the HPT, at the exit of the TCF and downstream of the LPT stage. The unsteady results obtained in the plane located at the exit of the LPT are discussed in more details in this second part of this paper, providing information about the interactions between the two rotors. A proper phase-average procedure, known as rotor synchronic averaging (RSA), which takes into account the rotorrotor interaction, was adopted to capture the unsteadiness due to both rotors. Proper Orthogonal Decomposition (POD) was also applied to provide a characterization of the major contributors in terms of energy to the deterministic unsteadiness occurring in the test turbine facility. At the exit of the LPT rotor, the perturbations induced by the HPT stage and the interactions between the two rotors were found to dominate over the unsteadiness due to the LPT only.

Effect of back pressure and freestream dynamic pressure on a typical Ramjet engine duct under realistic supersonic inlet condition

2017 ◽  
Vol 122 (1247) ◽  
pp. 83-103 ◽  
Author(s):  
R. Saravanan ◽  
S.L.N. Desikan ◽  
T.M. Muruganandam
Keyword(s):  
Dynamic Pressure ◽  
Back Pressure ◽  
Flow Visualisation ◽  
Pressure Measurements ◽  
Shock Train ◽  
Unsteady Pressure ◽  
Expansion Waves ◽  
Ramjet Engine ◽  
Flap Deflection ◽  
Unsteady Pressure Measurements

ABSTRACTThe present study investigates the behaviour of the shock train in a typical Ramjet engine under the influence of shock and expansion waves at the entry of a low aspect ratio (1:0.75) rectangular duct/isolator at supersonic Mach number (M = 1.7). The start/unstart characteristics are investigated through steady/unsteady pressure measurements under different back and dynamic pressures while the shock train dynamics are captured through instantaneous Schlieren flow visualisation. Two parameters, namely pressure recovery and the pressure gradient, is derived to assess the duct/isolator performance. For a given back pressure, with maximum blockage (9% above nominal), the duct/isolator flow is established when the dynamic pressure is increased by 23.5%. The unsteady pressure measurements indicate different scales of eddies above 80 Hz (with and without flap deflection). Under the no flap deflection (no back pressure) condition, the maximum fluctuating pressure component is 0.01% and 0.1% of the stagnation pressure at X/L = 0.03 (close to the entry of the duct) and X/L = 0.53 (middle of the duct), respectively. Once the flap is deflected (δ = 8°), decay in eddies by one order is noticed. Further increase in back pressure (δ ≥ 11°) leads the flow to unstart where eddies are observed to be disappeared.

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