Influence of Pre-Swirl, Rotor Speed and Blade Count on Aeroelastic Coupling Mechanisms During Stall Inception of a Transonic Compressor

2021 ◽  
Author(s):  
Daniel Franke ◽  
Maximilian J\xfcngst ◽  
Daniel M\xf6ller ◽  
Heinz-Peter Schiffer ◽  
Thomas Giersch
Keyword(s):  
Rotor Speed ◽  
Stall Inception ◽  
Transonic Compressor ◽  
Coupling Mechanisms

Influence of Pre-Swirl, Rotor Speed and Blade Count on Aeroelastic Coupling Mechanisms During Stall Inception of a Transonic Compressor

2020 ◽  
Author(s):  
Daniel Franke ◽  
Maximilian Jüngst ◽  
Daniel Möller ◽  
Heinz-Peter Schiffer ◽  
Thomas Giersch
Keyword(s):  
Phase Synchronization ◽  
Unsteady Aerodynamics ◽  
Propagation Speed ◽  
Experimental Investigations ◽  
Rotor Speed ◽  
Blade Vibration ◽  
Stall Inception ◽  
Global Trends ◽  
Transonic Compressor ◽  
Experimental Findings

Abstract The aeroelastic effects during stall inception in modern axial compressors have been a research focus for decades and yet are not fully understood. Experimental investigations, conducted at the 1.5-stage transonic compressor test rig at TU Darmstadt, using extensive unsteady aerodynamic and structural instrumentation, show global trends and influencing parameters on non-synchronous vibration and associated unsteady aerodynamics. During stall inception, aerodynamic disturbances occur and vary in count, size, cell speed and trajectory. The interaction with non-synchronous blade vibration results in changing stability mechanisms, indicating influences of pre-swirl, rotor speed and blade count on the traveling aerodynamic wave as well as the coupling with the structural wave. Supplementary numerical simulations of the test setup extend the available set of aerodynamic and aeromechanical data, and support the experimental findings. The study reveals the convective nature of NSV, influenced by the propagation speed of aerodynamic pre-stall disturbances, depending on rotor speed and pre-swirl, as well as its interaction with blade vibration, based on specific phase synchronization conditions and rotor blade count.

Numerical Investigations on Partial Surge Initiated Inception and Stall Evolution in a Transonic Compressor

2017 ◽  
Author(s):  
Jiaguo Hu ◽  
Tianyu Pan ◽  
Wenqian Wu ◽  
Qiushi Li ◽  
Yifang Gong
Keyword(s):  
High Performance ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Rapid Decline ◽  
Second Phase ◽  
Stall Inception ◽  
Transonic Compressor ◽  
Transient Simulations ◽  
Two Factors

The instability has been the largest barrier of the high performance axial compressor in the past decades. Stall inception, which determines the route and the characteristics of instability evolution, has been extensively focused on. A new stall inception, “partial surge”, is discovered in the recent experiments. In this paper full-annulus transient simulations are performed to study the origin of partial surge initiated inception and explain the aerodynamic mechanism. The simulations show that the stall inception firstly occurs at the stator hub region, and then transfers to the rotor tip region. The compressor finally stalled by the tip region rotating stall. The stall evolution is in accord with the experiments. The stall evolution can be divided into three phases. In the first phase, the stator corner separation gradually merged with the adjacent passages, producing an annulus stall cell at the stator hub region. In the second phase, the total pressure rise of hub region emerges rapid decline due to the fast expansion of the annulus stall cell, but the tip region maintains its pressure rise. In the third phase, a new rotating stall cell appears at the rotor tip region, leading to the onset of fast drop of the tip region pressure rise. The stall cells transfer from hub region to the tip region is caused by two factors, the blockage of the hub region which transfers more load to the tip region, and the separation fluid fluctuations in stator domain which increase the circumferential non-uniformity in the rotor domain. High load and non-uniformity at the rotor tip region induce the final rotating stall.

An Unsteady Numerical Investigation on the Hysteresis Stall Loop of a Counter-Rotating Compressor

2011 ◽  
Author(s):  
Zhuoqi Wang ◽  
Wei Yuan ◽  
Qiushi Li ◽  
Yajun Lu
Keyword(s):  
Numerical Simulation ◽  
Recovery Process ◽  
Characteristic Line ◽  
Rotor Speed ◽  
Stall Inception ◽  
Rotating Speed ◽  
Flow Phenomena ◽  
Stall Cells ◽  
Unsteady Numerical Simulation ◽  
Good Agreement

For investigating the flow phenomena in the stall process, a full annular unsteady numerical simulation has been carried out on a low speed counter-rotating compressor. The numerical results are in good agreement with experimental results. According to the CFD results, the stall inception was found in the tip region of the front rotor. The rotating speed of stall cells in the front rotor are about 41% of the rotor speed and the direction is the same with the rotor rotating direction. The stall cells occupies about 20% of the blade span away from the casing wall when the compressor is in deep stall. The flow phenomena is well captured which explained why the compressor characteristic line appears as a hysteresis loop in the stall inception-recovery process.

Influence of Compressor Deterioration on Engine Dynamic Behavior and Transient Stall-Margin

1999 ◽  
Author(s):  
Z. S. Spakovszky ◽  
J. B. Gertz ◽  
O. P. Sharma ◽  
J. D. Paduano ◽  
A. H. Epstein ◽  
...  
Keyword(s):  
Analytical Investigation ◽  
Tip Clearance ◽  
Shaft Speed ◽  
Rotor Speed ◽  
Commercial Aircraft ◽  
Stall Inception ◽  
Stall Margin ◽  
Engine Dynamic ◽  
System Mode ◽  
Flow Blockage

This paper presents an experimental and analytical investigation of compressor stability assessment during engine transient operation. A 2-dimensional, linear, compressible, state-space analysis of stall-inception (Feulner et al. (1996)) was modified to account for engine transients and deterioration, with the latter modeled as increased tip-clearance and flow blockage. Experiments were performed on large commercial aircraft engines in both undeteriorated and deteriorated states. Unsteady measurements of pressure in these test engines during rapid accelerations revealed the growth of pre-stall disturbances, which rotate at rotor speed and at approximately half rotor speed. These disturbances are stronger in deteriorated engines. The model showed that the signal at shaft speed was the first compressible system mode, whose frequency is near shaft speed, excited by geometric nonuniformities. The computed behavior of this mode during throttle transients closely matched engine data. The signal increased in strength as stall was approached and as the engine deteriorated. This work firmly establishes the connection between observed signals in the these engines and first principles stability models.

Experimental investigations on instability evolution in a transonic compressor at different rotor speeds

2015 ◽  
Vol 229 (18) ◽  
pp. 3378-3391 ◽  
Author(s):  
Qiushi Li ◽  
Tianyu Pan ◽  
Tailu Sun ◽  
Zhiping Li ◽  
Yifang Gong
Keyword(s):  
Low Frequency ◽  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Rotor Speed ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
New Type ◽  
Flow Compressor

Experimental investigations are conducted to study the instability evolution in a transonic axial flow compressor at four specific rotor speeds covering both subsonic and transonic operating conditions. Two routes of evolution to final instability are observed in the test compressor: at low rotor speeds, a disturbance in the rotor tip region occurs and then leads to rotating stall, while at high rotor speeds, a low-frequency disturbance in the hub region leads the compressor into instability. Different from stall and surge, this new type of compressor instability at high rotor speed is initiated through the development of a low-frequency axisymmetric disturbance at the hub, and we name it “partial surge”. The frequency of this low-frequency disturbance is approximately the Helmholtz frequency of the system and remains constant during instability inception. Finally, a possible mechanism for the occurrence of different instability evolutions and the formation of partial surge are also discussed.

Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Influence of Groove Location and Depth on Flow Instability

2013 ◽  
Author(s):  
Yasunori Sakuma ◽  
Toshinori Watanabe ◽  
Takehiro Himeno ◽  
Dai Kato ◽  
Takeshi Murooka ◽  
...  
Keyword(s):  
Flow Instability ◽  
Flow Behavior ◽  
Vortical Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Optimal Position ◽  
Stall Inception ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Stability Enhancement

The effect of circumferential single grooved casing treatment on the stability enhancement of NASA Rotor 37 has been examined with CFD analysis. Stall inception mechanism of Rotor 37 is presented first with principal focus on the tip leakage flow behavior, passage blockage, and the vortical flow structures. Detailed observation showed that the combined interaction of the stagnated flow of tip leakage vortex breakdown and the jet-like leakage flow from the mid-chord region leads to the blade tip-initiated stall inception. The result of numerical parametric study is then demonstrated to show the effect of varying the axial location and the depth of a circumferential single groove. The evaluation based on stall margin improvement showed a higher potential of deeper grooves in stability enhancement, and the optimal position for the groove to be located was indicated to exist near the leading edge of the blade.

Breakdown of Tip Leakage Vortices in Compressors at Flow Conditions Close to Stall

1997 ◽  
Author(s):  
Stefan Schlechtriem ◽  
Michael Lötzerich
Keyword(s):  
Vortex Breakdown ◽  
Stability Limit ◽  
Flow Conditions ◽  
Mixed Flow ◽  
Stall Inception ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Flow Compressor ◽  
The Stability ◽  
Operating Points

The breakdown of tip leakage vortices at operating points close to the stability limit of transonic compressor rotors has been detected. The aerodynamic phenomenon is considered to have a major impact on stall inception. Computations have been carried out and a detailed visualization of the phenomenon is given. In addition the connection of vortex breakdown to rotating instabilities and stall is discussed. Furthermore the tip flow field of the axial rotor is compared to the results for a centrifugal and a mixed flow compressor operating at similar tip speeds.

Effects of Rotating Inlet Distortion on Multisage Compressor Stability

1994 ◽  
Author(s):  
J. P. Longley ◽  
H.-W. Shin ◽  
R. E. Plumley ◽  
P. D. Silkowski ◽  
I. J. Day ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Stability Margin ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Peak ◽  
Rotor Speed ◽  
Stall Inception ◽  
Stall Margin ◽  
Inlet Distortion ◽  
Two Peaks

In multi-spool engines, rotating stall in an upstream compressor will impose a rotating distortion on the downstream compressor, thereby affecting its stability margin. In this paper experiments are described in which this effect was simulated by a rotating screen upstream of several multistage low-speed compressors. The measurements are complemented by, and compared with, a theoretical model of multistage compressor response to speed and direction of rotation of an inlet distortion. For co-rotating distortions (i.e., distortions rotating in the same direction as rotor rotation), experiments show that the compressors exhibited significant loss in stability margin and that they could be divided into two groups according to their response. The first group exhibited a single peak in stall margin degradation when the distortion speed corresponded to roughly 50% of rotor speed. The second group showed two peaks in stall margin degradation corresponding to distortion speeds of approximately 25–35% and 70–75% of rotor speed. These new results demonstrate that multistage compressors can have more than a single resonant response. Detailed measurements suggest that the two types of behavior are linked to differences between the stall inception processes observed for the two groups of compressors and that a direct connection thus exists between the observed forced response and the unsteady flow phenomena at stall onset. For counter-rotational distortions, all the compressors tested showed minimal loss of stability margin. The results imply that counter-rotation of the fan and core compressor, or LP and HP compressors, could be a worthwhile design choice. Calculations based on the two-dimensional theoretical model show excellent agreement for the compressors which had a single peak for stall margin degradation. We take this first-of-a-kind comparison as showing that the model, though simplified, captures the essential fluid dynamic features of the phenomena. Agreement is not good for compressors which had two peaks in the curve of stall margin shift versus distortion rotation speed. The discrepancy is attributed to the three-dimensional and short length scale nature of the stall inception process in these machines; this includes phenomena that have not yet been addressed in any model.

1997 Best Paper Award—Controls and Diagnostics Committee: Active Stabilization of Rotating Stall and Surge in a Transonic Single-Stage Axial Compressor

1998 ◽  
Vol 120 (4) ◽  
pp. 625-636 ◽  
Author(s):  
H. J. Weigl ◽  
J. D. Paduano ◽  
L. G. Fre´chette ◽  
A. H. Epstein ◽  
E. M. Greitzer ◽  
...  
Keyword(s):  
Mass Flow ◽  
Control Strategies ◽  
Axial Compressor ◽  
Gain Control ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Stage ◽  
Rotor Speed ◽  
Stall Inception ◽  
Spatial Harmonics

Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular array of twelve separately modulated air injectors. At tip relative Mach numbers of 1.0 and 1.5 the control achieved 11 and 3.5 percent reductions in stalling mass flow, respectively, with injection adding 3.6 percent of the design compressor mass flow. The aerodynamic effects of the injection have also been examined. At a tip Mach number, Mtip, of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the prestall perturbations using constant gain feedback. At a Mtip of 1.5 (design rotor speed), the prestall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. At design speed, the instability was initiated by approximately ten rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include more than one lightly damped mode, which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150 percent of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed. A dynamic, model-based robust controller was therefore used to stabilize the multiple modes that comprise the first three harmonic perturbations in this transonic region of operation.

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