Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance—Part II: Assessments of Methodology

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
K. L. Coleman ◽  
O. G. McGee, III
Keyword(s):  
Structural Design ◽  
High Speed ◽  
Control Strategies ◽  
Structural Parameters ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Engine Performance ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Low Speed

A theoretical assessment was made explaining how aeromechanical feedback control can be implemented to stabilize rotating stall inception in high-speed axial compression systems. Ten aeromechanical control strategies were quantitatively evaluated based on the control-theoretic formulations and dimensionless performance analysis outlined in the Part I companion paper (McGee and Coleman, 2013, “Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance—Part I: Control-Theoretic Models,” ASME J. Fluids Eng., 135(3), p. 031101). The maximum operating range for each aeromechanical control scheme was predicted for optimized structural parameters. Predictability and changeability in the hydrodynamic pressure, temperature, density, operability, and aeromechanical performance of dynamically-compensated, high-speed compressor maps of corrected pressure, corrected mass flow, corrected speeds, temperature ratios, and optimum efficiency were compared for the various aeromechanical control strategies. Compared with dynamically-compensated, low-speed compressor maps of pressure rise and flow coefficient (Gysling and Greitzer, 1995, “Dynamic Control of Rotating Stall in Axial Flow Compressors Using Aeromechanical Feedback,” ASME J. Turbomach., 117(3), pp. 307–319; McGee et al., 2004, “Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part I: Development of Models and Metrics, ASME J. Turbomach, 126(1), pp. 52–62; Fréchette et al., 2004, “Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part II: Evaluation of Approaches,” ASME J. Turbomach., 126(1), pp. 63–72), the present study shows that the most promising aeromechanical designs and controls for a class of high-speed compressors were the use of dynamic fluid injection. Dynamic compensations involving variable duct geometries and dynamically-re-staggered IGV and rotor blades were predicted to yield less controllability under high-speed flow environments. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided in high-speed compression systems as in low-speed ones by designing sufficiently rigid structures to prevent casing ovalization or other structurally-induced variations in tip clearance.

Effect of Tip Clearance on Stall Evolution Process in a Low-Speed Axial Compressor Stage

2004 ◽  
Author(s):  
Masahiro Inoue ◽  
Motoo Kuroumaru ◽  
Shinichi Yoshida ◽  
Takahiro Minami ◽  
Kazutoyo Yamada ◽  
...  
Keyword(s):  
Spectral Power ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Short Length ◽  
Tip Clearance ◽  
Evolution Process ◽  
Length Scale ◽  
Compressor Stage ◽  
Low Speed

Effect of the tip clearance on the transient process of rotating stall evolution has been studied experimentally in a low-speed axial compressor stage with various stator-rotor gaps. In the previous authors’ experiments for the small tip clearance, the stall evolution process of the rotor was sensitive to the gaps between the blade rows. For the large tip clearance, however, little difference is observed in the evolution processes independently of the blade row gap. In the first half process, it is characterized by gradual reduction of overall pressure-rise with flow rate decreasing, and the number of short length-scale disturbances is increasing with their amplitude increasing. In the latter half a long length-scale disturbance develops rapidly to result in deep stall. Just before the stall inception the spectral power density of the casing wall pressure reveals the existence of rotating disturbances with broadband high frequency near a quarter of the blade passing frequency. This is caused by the short length-scale disturbances occurring intermittently. A flow model is presented to explain mechanisms of the rotating short length-scale disturbance, which includes a tornado-like separation vortex and tip-leakage vortex breakdown. The model is supported by a result of a numerical unsteady flow simulation.

Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall: Part II — Evaluation of Approaches

2003 ◽  
Author(s):  
L. G. Fre´chette ◽  
O. G. McGee ◽  
M. B. Graf
Keyword(s):  
Structural Parameters ◽  
Axial Compressor ◽  
Coupled System ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Theoretical Evaluation ◽  
Axial Compressors ◽  
Spatial Modes ◽  
Control Authority

A theoretical evaluation was conducted delineating how aeromechanical feedback control can be utilized to stabilize the inception of rotating stall in axial compressors. Ten aeromechanical control methodologies were quantitatively examined based on the analytical formulations presented in the first part of this paper (McGee et al, 2003a). The maximum operating range for each scheme is determined for optimized structural parameters, and the various schemes are compared. The present study shows that the most promising aeromechanical designs and controls for a class of low-speed axial compressors were the use of dynamic fluid injection. Aeromechanically incorporating variable duct geometries and dynamically re-staggered IGV and rotor blades were predicted to yield less controllability. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided by designing sufficiently rigid structures to prevent casing ovalization or other structurally-induced variations in tip clearance. Control authority, a metric developed in the first part of this paper, provided a useful interpretation of the aeromechanical damping of the coupled system. The model predictions also show that higher spatial modes can become limiting with aeromechanical feedback, both in control of rotating stall as well as in considering the effects of lighter, less rigid structural aeroengine designs on compressor stability.

Characteristics of the Tip Leakage Vortex in a Low-Speed Axial Compressor With Different Rotor Tip Gaps

2012 ◽  
Author(s):  
Zhibo Zhang ◽  
Xianjun Yu ◽  
Baojie Liu
Keyword(s):  
Axial Compressor ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Tip Clearance ◽  
Test Facility ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Low Speed ◽  
Tip Leakage

The detailed evolutionary processes of the tip leakage flow/vortex inside the rotor passage are still not very clear for the difficulties of investigating of them by both experimental and numerical methods. In this paper, the flow fields near the rotor tip region inside the blade passage with two tip gaps, 0.5% and 1.5% blade height respectively, were measured by using stereoscopic particle image velocimetry (SPIV) in a large-scale low speed axial compressor test facility. The measurements are conducted at four different operating conditions, including the design, middle, maximum static pressure rise and near stall conditions. In order to analyze the variations of the characteristics of the tip leakage vortex (TLV), the trajectory, concentration, size, streamwise velocity, and the blockage parameters are extracted from the ensemble-averaged results and compared at different compressor operating conditions and tip gaps. The results show that the formation of the TLV is delayed with large tip clearance, however, its trajectory moves much faster in an approximately linear way from the blade suction side to pressure side. In the tested compressor, the size of the tip gap has little effects on the scale of the TLV in the spanwise direction, on the contrary, its effects on the pitch-wise direction is very prominent. Breakdown of the TLV were both found at the near-stall condition with different tip gaps. The location of the initiation of the TLV breakdown moves downstream from the 60% chord to 70% chord as the tip gap increases. After the TLV breakdown occurs, the flow blockage near the rotor tip region increases abruptly. The peak value of the blockage effects caused by the TLV breakdown is doubled with the tip gap size increasing from 0.5% to 1.5% blade span.

scholarly journals Active flow control at a 1.5-stage low-speed research compressor with varying rotor tip clearance

2011 ◽  
Vol 225 (7) ◽  
pp. 886-896 ◽  
Author(s):  
M Künzelmann ◽  
R Urban ◽  
R Mailach ◽  
K Vogeler
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stall Inception ◽  
Low Speed ◽  
Operating Range ◽  
Compressor Rotor ◽  
Active Flow

The stable operating range of axial compressors is limited by the onset of rotating stall and surge. Mass injection upstream of the tip of an axial compressor rotor is a stability enhancement approach which can be effective in suppressing stall in tip-critical rotors, and thus increasing the operating range of compressors. In this article, investigations on active flow control related to the rotor tip gap sensitivity are discussed. The experiments were performed in a 1.5-stage low-speed research compressor. Measurements at part speed (80 per cent) and full speed (100 per cent) with varying injection rates are discussed. These tests were performed for two rotor tip clearances of 1.3 per cent and 4.3 per cent of rotor blade tip chord. Results on the compressor map, the flow field as well as transient measurements to identify the stall inception are discussed. Supplementary, the numerical results are compared to the experiments based on the configuration with the greatest benefit in operating range enhancement.

Tailored Structural Design and Aeromechanical Control of Axial Compressor Stall—Part II: Evaluation of Approaches

2004 ◽  
Vol 126 (1) ◽  
pp. 63-72 ◽  
Author(s):  
L. G. Fre´chette ◽  
O. G. McGee ◽  
M. B. Graf
Keyword(s):  
Structural Parameters ◽  
Axial Compressor ◽  
Coupled System ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Theoretical Evaluation ◽  
Axial Compressors ◽  
Spatial Modes ◽  
Control Authority

A theoretical evaluation was conducted delineating how aeromechanical feedback control can be utilized to stabilize the inception of rotating stall in axial compressors. Ten aeromechanical control methodologies were quantitatively examined based on the analytical formulations presented in the first part of this paper. The maximum operating range for each scheme is determined for optimized structural parameters, and the various schemes are compared. The present study shows that the most promising aeromechanical designs and controls for a class of low-speed axial compressors were the use of dynamic fluid injection. Aeromechanically incorporating variable duct geometries and dynamically re-staggered IGV and rotor blades were predicted to yield less controllability. The aeromechanical interaction of a flexible casing wall was predicted to be destabilizing, and thus should be avoided by designing sufficiently rigid structures to prevent casing ovalization or other structurally induced variations in tip clearance. Control authority, a metric developed in the first part of this paper, provided a useful interpretation of the aeromechanical damping of the coupled system. The model predictions also show that higher spatial modes can become limiting with aeromechanical feedback, both in control of rotating stall as well as in considering the effects of lighter, less rigid structural aeroengine designs on compressor stability.    

Experimental Study on Different Tip Clearance of Low-Speed Axial Fan

2021 ◽  
Author(s):  
Ming Zhang ◽  
Jia Li ◽  
Xu Dong ◽  
Dakun Sun ◽  
Xiaofeng Sun
Keyword(s):  
Experimental Studies ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Signal Spectrum ◽  
Tip Clearance Flow ◽  
Low Speed ◽  
Clearance Flow ◽  
Casing Pressure

Abstract Tip clearance flow is not only the source of undesirable noise but also a potential indicator for critical operating conditions with rotating stall or surge. It can induce blade vibration, which would cause premature blade failure when the vibration is strong enough. The paper presents experimental studies on the effects of tip clearance on the stall inception process in a low-speed high-load single stage fan with different tip clearance. From the point of view of flow range, it has been proved by computations that there is an optimal gap value, and an explanation is given according to different stall mechanisms of large and small tip clearance. However, the experiment of no tip clearance is not easy to achieve. In this experiment, a wearable soft wall casing was used to achieve “zero clearance”, and an explicit conclusion was obtained. The pressure rise and efficiency are improved at small tip clearance. Instantaneous Casing Pressure Field Measurement was carried out: instantaneous casing pressure fields were measured by 9 high response pressure transducers mounted on the casing wall. At the near stall point with large tip clearance, a narrow band increase of the amplitudes in the frequency spectrum at roughly half of the blade passing frequency can be observed according to the spectrum of static pressure at points on the endwall near the leading-edge and above the rotor. This phenomenon was explained from two aspects: tip clearance flow structure and pressure signal spectrum.

Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance— Part I: Control-Theoretic Models

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
O. G. McGee ◽  
K. L. Coleman
Keyword(s):  
High Speed ◽  
Axial Compressor ◽  
Engine Performance ◽  
Maximum Flow ◽  
Rotating Stall ◽  
Design Flow ◽  
Systematic Evaluation ◽  
Stable Operation ◽  
Stall Inception ◽  
Axial Compressors

General methodologies are proposed in this two-part paper that further phenomenological understanding of compressible stall inception and aeromechanical control of high-speed axial compressors and engine performance. Developed in Part I are strategies for passive stabilization of compressible rotating stall, using tailored structural design and aeromechanical feedback control, implemented in certain classes of high-speed axial compressors used in research laboratories and by industry. Fundamentals of the stability of various dynamically-compensated, high-speed compressors was set down from linearized, compressible structural-hydrodynamic equations of modal stall inception extended further in this study from previous work. A dimensionless framework for performance-based design of aeromechanically-controlled compression system stall mitigation and engine performance is established, linking specified design flow and work-transfer (pressure) operability to model stages or local blade components, velocity triangle environment, optimum efficiency, extended stall margin and operability loci, and aeromechanical detailed design. A systematic evaluation was made in Part II (Coleman and McGee, 2013, “Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance—Part II: Assessments of Methodology,” ASME J. Fluids Eng. (to be published)) on the performance of ten aeromechanical feedback controller schemes to increase the predicted range of stable operation of two laboratory compressor characteristics assumed, using static pressure sensing and local structural actuation to rudimentary postpone high-speed modal stall inception. The maximum flow operating range for each of the ten dynamically-compensated, high-speed compression systems was determined using optimized or “tailored” structural controllers, and the results described in Part II of the companion paper are compared to maximum operating ranges achieved in corresponding low-speed compression systems.

scholarly journals Prestall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Jen-Ping Chen ◽  
Michael D. Hathaway ◽  
Gregory P. Herrick
Keyword(s):  
High Performance ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Direction ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Compressor Stage ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Fast Fourier Transform Analysis

Computational fluid dynamics calculations using high-performance parallel computing were conducted to simulate the prestall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial fast Fourier transform analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.

Combined Effects of Forward Sweep and Tip Clearance on the Performance of Axial Flow Compressor Stage

2009 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Numerical Work ◽  
Low Speed ◽  
Operating Range ◽  
Axial Flow Compressor ◽  
Flow Compressor

There are a number of performance indices for a turbomachine on the basis of which its strength is evaluated. In the case of axial compressors, pressure ratio, efficiency and stall margin are few such indices which are of major concern in the design phase as well as in the evaluation of performance of the machine. In the process of improving the blade design, 3D blade stacking, where the aerofoil sections constituting the blade are moved in relation to the flow. Tilting the blade sections to the flow direction (blade sweep) would increase the operating range of an axial compressor due to modifications in the pressure and velocity fields on the suction surface. On the other hand, blade tip gap, though finite, has great influence on the performance of a turbomachine. The present work investigates the combined effect of these two factors on various flow characteristics in a low speed axial flow compressor. The objective of the present paper is thereby confined to study the collective effects of sweep and tip clearance without attempting to suggest an outright new design. In the present numerical work, the performance of Tip Chordline Sweeping (TCS) and Axial Sweeping (AXS) of low speed axial compressor rotor blades are studied. For this, 15 computational domains were modeled for five rotor sweep configurations and three different clearance levels for each rotor. Through the results, 20°AXS rotor is found to be distinctive among all the rotors with highest pressure rise, higher operating range and less tip clearance loss characteristics. TCS rotors produced improved total pressure rise at the low flow coefficients when the tip gap is increased. Hence there is a chance that an “optimum” tip gap exists for the TCS rotors in terms of total pressure coefficient and operating range, while AXS rotors are at their best with the minimum possible clearance.

Prediction of Low Speed Compressor Rotor Flowfields With Large Tip Clearances

2003 ◽  
Author(s):  
Anurag Gupta ◽  
S. Arif Khalid ◽  
G. Scott McNulty ◽  
Lyle Dailey
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Low Speed ◽  
Compressor Rotor ◽  
Wide Range ◽  
Measured Pressure

Rotor tip modeling fidelity, grid resolution, and near wall modeling have been examined to determine the requirements for an accurate prediction of the effects of large tip clearance in a low-speed axial compressor rotor. The effort, using a Reynolds-Averaged Navier-Stokes (RANS) solver, aimed to obtain the most accurate predictions from a three-dimensional, steady, single blade row simulation. A recently tested, modern low speed rotor, was used as the test geometry; the measured pressure rise characteristic as well as detailed data near stall was used to evaluate the ability of different modeling strategies to capture the correct flow structure. The leakage flow was quantified to show that a wide range of tip blockage could be obtained for different simulations of the same geometry and conditions. The results show that using a square tip and gridding to fully resolve the real tip gap was better able to capture the effects of loading on the leakage flow than either of the approximate models studied. Sufficient clustering near the casing to capture the shear layers was also found to be critical. While wall integration provided the best results in simultaneously improving the prediction of pressure rise characteristics and flow range, higher fidelity wall modeling and a casing y+ of approximately 3 were found to provide similar benefits.

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