Prestall Instability in Axial Flow Compressors

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Mario Eck ◽  
Roland Rückert ◽  
Dieter Peitsch ◽  
Marc Lehmann
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Propagation Speed ◽  
Flow Coefficient ◽  
Spectral Signature ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Flow Disturbances

Abstract The aim of the present paper is to improve the physical understanding of discrete prestall flow disturbances developing in the tip area of the compressor rotor. For this purpose, a complementary instrumentation was used in a single-stage axial compressor. A set of pressure transducers evenly distributed along the circumference surface mounted in the casing near the rotor tip leading edges measures the time-resolved wall pressures simultaneously to an array of transducers recording the chordwise static pressures. The latter allows for plotting quasi-instantaneous casing pressure contours. Any occurring flow disturbances can be properly classified using validated frequency analysis methods applied to the data from the circumferential sensors. While leaving the flow coefficient constant, a continuously changing number of prestall flow disturbances appears to be causing a unique spectral signature, which is known from investigations on rotating instability. Any arising number of disturbances is matching a specific mode order found within this signature. While the flow coefficient is reduced, the propagation speed of prestall disturbances increases linearly, and meanwhile, the speed seems to be independent from the clearance size. Casing contour plots phase-locked to the rotor additionally provide a strong hint on prestall disturbances clearly not to be caused by a leading edge separation. Data taken beyond the stalling limit demonstrate a complex superposition of stall cells and flow disturbances, which the title “prestall disturbance” therefore does not fit to precisely any more. Different convection speeds allow the phenomena to be clearly distinguished from each other. Furthermore, statistical analysis of the pressure fluctuations caused by the prestall disturbances offer the potential to use them as a stall precursor or to quantify the deterioration of the clearance height between the rotor blade tips and the casing wall during the lifetime of an engine.

A Novel Stall Warning Indicator: Part II — Underlying Flow Mechanism

2019 ◽  
Author(s):  
Mario Eck ◽  
Roland Rückert ◽  
Marc Lehmann ◽  
Dieter Peitsch
Keyword(s):  
Axial Compressor ◽  
Propagation Speed ◽  
Flow Coefficient ◽  
Spectral Signature ◽  
The Novel ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Flow Disturbances ◽  
Stall Warning ◽  
Rotating Instability

Abstract The aim of the present paper is to improve the physical understanding of flow irregularities in the blade passing signal of turbomachinery rotors, since the novel stall warning method presented in part I is based upon those irregularities. For this purpose, a complementary instrumentation was used in a single stage axial compressor. A set of pressure transducers evenly distributed along the circumference surface mounted in the casing near the rotor tip leading edges is measuring the time-resolved wall pressures simultaneously to an array of transducers recording the chord-wise static pressures. The latter allows for plotting quasi-instantaneous 2D-pressure contours. Any occurring flow disturbances causing the before mentioned irregularity can later be classified using validated frequency analysis methods being applied to the data from the circumferential sensors. While leaving the flow coefficient constant, a continuously changing number of prestall flow disturbances appears to be causing the very spectral signature which is known from investigations on Rotating Instability. Any arising number of disturbances is matching a specific mode order to be found within the spectral signature. While the flow coefficient is reduced the propagation speed of prestall disturbances increases linearly as the speed seems to be independent from the clearance size. Data taken beyond the stalling limit demonstrate a complex superposition of stall cells and flow disturbances which the title “prestall disturbance” therefore doesn’t fit to precisely any more. Different convection speeds allow the phenomena to be clearly distinguished from each other.

Upstream Potential Propagation Effects of Unsteady Stator-Rotor Interaction in an Axial Flow Blower: Numerical Analysis and Experimental Validation

2006 ◽  
Author(s):  
J. M. Ferna´ndez Oro ◽  
K. M. Argu¨elles Di´az ◽  
C. Santolaria Morros ◽  
R. Ballesteros Tajadura
Keyword(s):  
Pressure Fluctuations ◽  
Axial Flow ◽  
Leading Edge ◽  
Potential Effect ◽  
Potential Interaction ◽  
Rotor Blades ◽  
Axial Distance ◽  
Pressure Transducers ◽  
Wake Interactions ◽  
Rotor Stator Interaction

The potential effect of the inlet guide vanes blockage is predominant in an axial one-stage configuration when the upstream flow field is considered. In the same way, rotor downstream, the main unsteadiness is provoked by the rotor wakes mixing-out at the machine discharge. Nevertheless, if the gap between the rows is significantly reduced, the stator wakes are not allowed to be mixed out before impinging the rotor blades, so a chopping effect overcomes, stretching and tilting them, and generating wake-wake interactions and new loss sources at the exit. On a similar trend, it is expected that a reduced axial gap allows the potential unsteadiness of the rotor blockage between the blades to be propagated upstream, modulating the flow conditions at the stator passages, and even at vanes leading edge locations. In this paper, the evolution of the rotor potential interaction within the stator passages and up to the vanes leading edge is analyzed. The main goal is placed on the analysis of the propagation, relating the axial distance with the attenuation of those potential mechanisms. A numerical 3D simulation of a complete single stage axial flow blower has been developed and executed using a commercial code that resolves the URANS set of equations. The axial gap between the 13-IGVs stator and the 9-blade rotor has been modified in order to evaluate its influence on the potential distortion propagated upstream of the stator. For the closing of turbulence, a LES scheme with a Smagorinsky-Lilly model is used in the computations. Finally, due to the LES characteristics, a phase-averaged procedure has to be introduced for the simulation post-processing. Complementary, experimental measurements have been carried out over a test rig with modifiable axial gap between the fixed and rotating blade rows. As a matter of fact, pressure transducers were placed all along the machine shroud to capture pressure fluctuations related to potential sources radiated from the rotor blades. These measurements have been analyzed using frequential analysis, which is essential to identify the origin of the flow inlet distortions. The final objective is to complete the rotor-stator interaction scenario both downstream and upstream the stage. Previous works were focused on the downstream conditions and now the upstream potential propagation is studied in detail.

An Experimental and Computational Investigation of Tip Clearance Flow and Its Impact on Stall Inception

2010 ◽  
Author(s):  
Matthew A. Bennington ◽  
Mark H. Ross ◽  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Juan Du ◽  
...  
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Momentum Balance ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Clearance Flow

A numerical and experimental study was conducted to investigate the tip clearance flow and its relationship to stall in a transonic axial compressor. The CFD results were used to identify the existence of an interface between incoming axial flow and the reverse tip clearance flow. A surface streaking method was used to experimentally identify this interface as a line of zero axial shear stress at the casing. The position of this line, denoted xzs, moved upstream with decreasing flow coefficient in both the experiments and computations. The line was found to be at the rotor leading edge plane when the compressor stalled. Further measurements using rotor offset and inlet distortion further corroborated these results, and demonstrated that the movement of the interface upstream of the leading edge leads to the generation of rotating (“spike”) disturbances. Stall was therefore interpreted to occur as a result of a critical momentum balance between the approach fluid and the tip-leakage flow.

An Experimental Investigation of Stator Clocking Effects in a Two-Stage Low-Speed Axial Compressor

2011 ◽  
Author(s):  
J. Sta¨ding ◽  
D. Wulff ◽  
G. Kosyna ◽  
B. Becker ◽  
V. Gu¨mmer
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Global Scale ◽  
Flow Coefficient ◽  
Maximum Efficiency ◽  
Pressure Measurements ◽  
Low Speed ◽  
The Impact

The impact of stator clocking on performance and flow of a 2.5-stage axial compressor has been investigated. Stator clocking, the circumferential indexing of adjacent stator rows with equal blade counts, is known as a potential means to modify the flow field in multistage turbomachinery and increase overall efficiencies of both turbines and compressors. These potential effects on turbomachine performance are due to wake-airfoil interactions and primarily depend on the alignment of the downstream stator row with the upstream stator wake path. The present survey describes and discusses the experimental research on stator clocking effects in a low-speed 2.5-stage axial flow compressor, using front loaded CDA blade sections and cantilevered stator rows with identical blade counts. Conventional static pressure tappings were used to locate global peaks in compressor performance for varying Stator 2 clocking positions at different flow coefficients. Results of unsteady total pressure measurements obtained by means of a high-frequency pressure transducer, embedded in the Stator 2 leading edge, give information on Stator 1 wake propagation. Traverse data from pneumatic 5-hole probes show the impact of stator indexing on Stator 2 exit total pressure at different blade spans. Regardless of flow coefficient, the variations of overall compressor efficiency due to Stator 2 clocking are around 0.2% and are exhibiting a near-sinusoidal trend over the clocking angle. It is shown that total pressure measurements at mid-span of Stator 2 leading edge suggest best overall performances for design and low loading conditions, if the Stator 1 wakes pass through mid-passage of Stator 2. At high loading, however, maximum efficiency locates the wake path directly at the leading edge. Due to a considerable span-wise skewness of the upstream stator wake, the aerodynamic clocking position for Stator 2 varies from hub to tip. While it is shown again that this effect weakens the advantages of airfoil indexing on a global scale, stator clocking shows much more potential if only a single blade section is considered.

Effect of Clocking on the Second Stator Pressure Field of a One and a Half Stage Transonic Turbine

2004 ◽  
Author(s):  
J. Gadea ◽  
R. De´nos ◽  
G. Paniagua ◽  
N. Billiard ◽  
C. H. Sieverding
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Static Pressure Distribution ◽  
Transonic Turbine

This paper focuses on the experimental investigation of the time-averaged and time-resolved pressure field of a second stator tested in a one and a half stage high-pressure transonic turbine. The effect of clocking and its influence on the aerodynamic and mechanical behaviour are investigated. The test program includes four different clocking positions, i.e. relative pitch-wise positions between the first and the second stator. Pneumatic probes located upstream and downstream of the second stator provide the time-averaged component of the pressure field. For the second stator airfoil, both time-averaged and time-resolved surface static pressure fields are measured at 15, 50 and 85% span with fast response pressure transducers. Regarding the time-averaged results, the effect of clocking is mostly observed in the leading edge region of the second stator, the largest effects being observed at 15% span. The surface static pressure distribution is changed locally, which is likely to affect the overall performance of the airfoil. The phase-locked averaging technique allows to process the time-resolved component of the data. The pressure fluctuations are attributed to the passage of pressure gradients linked to the traversing of the upstream rotor. The pattern of these fluctuations changes noticeably as a function of clocking. Finally, the time-resolved pressure distribution is integrated along the second stator surface to determine the unsteady forces applied on the vane. The magnitude of the unsteady force is very dependent on the clocking position.

Influence of Flow Coefficient, Stagger Angle, and Tip Clearance on Tip Vortex in Axial Compressors

2006 ◽  
Vol 128 (6) ◽  
pp. 1274-1280 ◽  
Author(s):  
Yong Sang Yoon ◽  
Seung Jin Song ◽  
Hyoun-Woo Shin
Keyword(s):  
Pressure Fluctuations ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Tip Vortex ◽  
Time Resolved ◽  
Pressure Transducers ◽  
High Frequency Response ◽  
Response Pressure ◽  
Casing Pressure ◽  
Stagger Angle

Experiments have been performed on the low speed research compressor (LSRC) at General Electric Aircraft Engines to investigate the effects of flow coefficient, stagger angle, and tip clearance on tip vortex. Time resolved casing pressure distributions over the third stage rotor have been acquired with high-frequency-response pressure transducers. Also, tip vortex strength and trajectory have been estimated from the casing pressure fluctuations which have been obtained simultaneously from various axial locations. As flow coefficient decreases, tip vortex gets strengthened and migrates upstream. The stagger angle increase weakens the tip vortex and moves it downstream slightly because the blade loading is decreased. However, tip leakage vortex is influenced mainly by tip clearance, and there exists a “critical” tip clearance which determines the type of tip vortex trajectory (“straight” or “kinked”). As predicted by others, tip vortex gets strengthened with increasing tip clearance. However, unlike the predictions, the tip vortex trajectory moves upstream with increasing tip clearance. Furthermore, with tip clearance above a “critical” value, the tip vortex trajectory is no longer straight but shows a kink in the passage.

Improved criteria for stall-free preliminary design of axial compressor of aero gas turbine engines

2018 ◽  
Vol 233 (9) ◽  
pp. 3286-3297 ◽  
Author(s):  
MR Aligoodarz ◽  
A Mehrpanahi ◽  
M Moshtaghzadeh ◽  
A Hashiehbaf
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Axial Compressor ◽  
Axial Flow ◽  
Design Criterion ◽  
Flow Coefficient ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Parameter Ranges ◽  
Axial Flow Compressors

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes.

Early Stall Warning Technique for Axial-Flow Compressors

2006 ◽  
Vol 129 (3) ◽  
pp. 448-456 ◽  
Author(s):  
Nobuyuki Tahara ◽  
Masahiro Kurosaki ◽  
Yutaka Ohta ◽  
Eisuke Outa ◽  
Takurou Nakajima ◽  
...  
Keyword(s):  
Risk Index ◽  
Axial Flow ◽  
Leading Edge ◽  
Warning Signal ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Case Scenario ◽  
Worst Case ◽  
Stall Margin ◽  
Stall Warning

This paper proposes a unique stall risk index based on pressure signals by high-response transducers on the casing wall at the rotor leading-edge location. The aim of the research is to explore the possibility of reducing current excessive stall margin requirement for compressor design based on the worst-case scenario. The index is generated by computing correlation degradation of pressure time histories of current and one revolution before over each blade pitch. Tests conducted on a single-stage low-speed compressor exhibits that the correlation diminishes significantly with proximity to stall, and the proposed technique might have the capability of generating a stall warning signal sufficiently in advance of spike inception. Extensive experiments on a research compressor show that the degree of the index degradation depends on various factors, such as flow coefficient, tip clearance, and rotor blade incidence. In order to obtain a reliable stall warning signal in practical use, these effects must be carefully examined.

The Influence of Tip Clearance Momentum Flux on Stall Inception in a High-Speed Axial Compressor

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Joshua D. Cameron ◽  
Matthew A. Bennington ◽  
Mark H. Ross ◽  
Scott C. Morris ◽  
Juan Du ◽  
...  
Keyword(s):  
Momentum Flux ◽  
High Speed ◽  
Axial Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Axial Position ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage

Experimental and numerical studies were conducted to investigate tip-leakage flow and its relationship to stall in a transonic axial compressor. The computational fluid dynamics (CFD) results were used to identify the existence of an interface between the approach flow and the tip-leakage flow. The experiments used a surface-streaking visualization method to identify the time-averaged location of this interface as a line of zero axial shear stress at the casing. The axial position of this line, denoted xzs, moved upstream with decreasing flow coefficient in both the experiments and computations. The line was consistently located at the rotor leading edge plane at the stalling flow coefficient, regardless of inflow boundary condition. These results were successfully modeled using a control volume approach that balanced the reverse axial momentum flux of the tip-leakage flow with the momentum flux of the approach fluid. Nonuniform tip clearance measurements demonstrated that movement of the interface upstream of the rotor leading edge plane leads to the generation of short length scale rotating disturbances. Therefore, stall was interpreted as a critical point in the momentum flux balance of the approach flow and the reverse axial momentum flux of the tip-leakage flow.

scholarly journals Design and Test of a New Axial Compressor for the Nuovo Pignone Heavy Duty Gas Turbines

1996 ◽  
Author(s):  
Erio Benvenuti
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Leading Edge ◽  
Meridional Flow ◽  
Heavy Duty ◽  
Pressure Transducers ◽  
Easy Integration

This axial compressor design was primarily focused to increase the power rating of the current Nuovo Pignone PGT10 Heavy-Duty gas turbine by 10%. In addition, the new 11-stage design favourably compares with the existing 17-stage compressor in terms of simplicity and cost. By seating the flowpath and blade geometry, the new aerodynamic design can be applied to gas turbines with different power ratings as well. The reduction in the stage number was achieved primarily through the meridional flow-path redesign. The resulting higher blade peripheral speeds achieve larger stage pressure ratios without increasing the aerodynamic loadings. Wide chord blades keep the overall length unchanged thus assuring easy integration with other existing components. The compressor performance map was extensively checked over the speed range required for two-shaft gas turbines. The prototype unit was installed on a special PGT10 gas turbine setup, that permitted the control of pressure ratio independently from the turbine matching requirements. The flowpath instrumentation included strain-gages, dynamic pressure transducers and stator vane leading edge aerodynamic probes to determine individual stage characteristics. The general blading vibratory behavior was proved fully satisfactory. With minor adjustments to the variable stator settings the front stage aerodynamic matching was optimized and the design performance was achieved.

Sign in / Sign up

Export Citation Format

Share Document