Experimental Off-Design Investigation of Unsteady Secondary Flow Phenomena in a Three-Stage Axial Compressor at 68% Nominal Speed

2004 ◽  
Author(s):  
Andreas Bohne ◽  
Reinhard Niehuis
Keyword(s):  
Dynamic Pressure ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Pressure Transducers ◽  
Surge Margin ◽  
Clearance Flow ◽  
Flow Phenomena

This paper deals with unsteady measurements in a highspeed three-stage axial compressor with inlet guide vanes (IGV) and controlled diffusion airfoils (CDA) at off-design conditions. The compressor under consideration exhibits design features of real industrial compressors. The main emphasis is put on the experimental investigation of two operating points at 68% nominal speed where a significant mismatching of the stages occurs. The first operating point is the last stable one near the surge margin whereas the second one represents choke. Probe traverses with a high resolution both in space and time show the significant potential upstream influence of the rotor blades. This effect and the disturbances caused by the convected wakes do strongly influence the unsteady boundary layer behaviour of the stator blades which are detected by glue-on hot-film sensors at different spanwise positions. Dynamic pressure transducers on the casing show that the structure of the rotor tip clearance flow strongly depends on the operating conditions of the compressor. Conclusions can be drawn concerning the consideration of the discussed unsteady effects within the design process of multistage axial compressors with respect to the presented results.

scholarly journals Experimental investigation of unsteady flow phenomena in a three-stage axial compressor

2003 ◽  
Vol 217 (4) ◽  
pp. 341-348 ◽  
Author(s):  
R Niehuis ◽  
A Bohne ◽  
A Hoynacki
Keyword(s):  
Measurement Techniques ◽  
Axial Compressor ◽  
Global Scale ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena ◽  
Rotor Stator Interaction ◽  
Interaction Phenomena

In the past years, a three-stage axial compressor equipped with a modern controlled diffusion airfoil (CDA) blading has been investigated in much detail, applying state-of-the-art steady and unsteady measurement techniques, at RWTH Aachen University. The compressor under investigation exhibits design features of real industrial compressors. By performing high-resolution measurements both in space and time, a thorough insight into various flow phenomena in the compressor has been achieved, leading to a better understanding of various flow phenomena such as rotor—stator interaction, tip clearance flow and viscous flow effects in a multistage compressor environment. After a short summary of some performance characteristics at design and off-design, this paper focuses on the analysis of interaction phenomena present in the three-stage axial compressor. The interaction phenomena are described on a more global scale. In order to quantify the upstream and downstream influence of the three rotor blades, a suitable parameter is presented.

Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 127-142
Author(s):  
Wei Zhu ◽  
Songtao Wang ◽  
Longxin Zhang ◽  
Jun Ding ◽  
Zhongqi Wang
Keyword(s):  
Numerical Simulations ◽  
Dynamic Balance ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Phenomena

This study aimed to enhance the understanding of flow phenomena in low-reaction aspirated compressors. Three-dimensional, multi-passage steady and unsteady numerical simulations are performed to investigate the performance sensitivity to tip clearance variation on the first-stage rotor of a multistage low-reaction aspirated compressor. Three kinds of tip clearance sizes including 1.0τ, 2.0τ and 3.0τ are modeled, in which 1.0τ corresponds to the designed tip clearance size of 0.2 mm. The steady numerical simulations show that the overall performance of the rotor moves toward lower mass flow rate when the tip clearance size is increased. Moreover, energy losses, efficiency reduction and stall margin decrease are also observed with increasing tip clearance size. This can be mostly attributed to the damaging impact of intense tip clearance flow. For unsteady simulation, the result shows periodical oscillation of the tip leakage vortex and a “two-passage periodic structure” in the tip region at the near-stall point. The occurrence of the periodical oscillation is due to the severe interaction between the tip clearance flow and the shock wave. However, the rotor operating state is still stable at this working point because a dynamic balance is established between the tip clearance flow and incoming flow.

scholarly journals Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

1996 ◽  
Vol 118 (2) ◽  
pp. 218-229 ◽  
Author(s):  
K. L. Suder ◽  
M. L. Celestina
Keyword(s):  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Peak Efficiency ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Design Speed

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part-speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100 percent design speed and at near peak efficiency at 60 percent design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only five times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the end-wall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part-speed conditions is also discussed.

Numerical simulation of unsteady tip clearance flow in an isolated axial compressor rotor blades row

2011 ◽  
Vol 226 (1) ◽  
pp. 82-93 ◽  
Author(s):  
R Taghavi-Zenouz ◽  
S Eslami
Keyword(s):  
Experimental Data ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Clearance Flow

Three-dimensional unsteady numerical simulations were carried out to analyse tip clearance flow in a low-speed isolated axial compressor rotor blades row. A flow solver has been used for the current study utilizing the large eddy simulation (LES) technique. Periodic tip leakage flow and its propagation trajectories were simulated in detail. A number of pseudo pressure transducers were imposed on the pressure side of the blade for detection of unsteady surface pressures to provide a calculation of tip leakage flow frequencies. Two different sizes of tip clearance were considered for simulations and analyses. Non-dimensional frequencies of the tip leakage flow were calculated and final results were compared to those of existing numerical and experimental data. Final results demonstrated that in contrast to the Reynolds averaged Navier–Stokes (RANS) model, the LES method shows considerable dependency of frequency characteristics of the tip leakage flow to the gap size and can detect different frequency spectrums along the blade surface. All the results obtained through the current numerical approach were in close agreement with those of existing experimental data.

On Improving the Surge Margin of a Tip-Critical Axial Compressor Rotor

2017 ◽  
Author(s):  
Marcus Lejon ◽  
Tomas Grönstedt ◽  
Niklas Andersson ◽  
Lars Ellbrant ◽  
Hans Mårtensson
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Incoming Flow ◽  
Objective Functions ◽  
Blade Loading ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Surge Margin ◽  
Clearance Flow

Delaying breakdown of the flow in the tip region of a tip-critical compressor rotor as long as possible, i.e. improving the surge margin, is of great interest to the turbomachinery community and is the focus of this study. The surge margin of ten compressor rotors is evaluated numerically, each with different blade loading and geometry at the tip. Previous work in the field has shown the dependence of an interface in the tip region of a compressor rotor between the incoming flow and the tip clearance flow with the passage flow coefficient ϕ. Previous work in the field has also shown that a higher incoming meridional momentum in the tip region can be beneficial to the surge margin of a tip-critical rotor. The present study generalizes these findings by taking into account the local blade loading of the rotor tip section and the level of loss in the tip region. The surge margin is found to improve if the blade loading of the rotor tip section is increased, which acts to increase the incoming mass flow rate and improve the surge margin provided that an increase in loss, mainly related to the strength and direction of the tip clearance flow, does not negate the effect as the compressor is throttled. Two quantities are proposed as objective functions to be used for optimization to achieve a compressor rotor with high surge margin based on the flow field at the design point. Finally, an optimization and analysis of the results is made to demonstrate the proposed objective functions in practise.

3-D Digital PIV Measurements of the Tip Clearance Flow in an Axial Compressor

2002 ◽  
Author(s):  
Mark P. Wernet ◽  
Dale Van Zante ◽  
Tony J. Strazisar ◽  
W. Trevor John ◽  
P. Susan Prahst
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Image Velocimetry ◽  
Clearance Flow ◽  
Compressor Performance ◽  
Tip Clearance Vortex

The accurate characterization and simulation of rotor tip clearance flows has received much attention in recent years due to their impact on compressor-performance and stability. At NASA Glenn the first known three dimensional Digital Particle Image Velocimetry (DPIV) measurements of the tip region of a low speed compressor rotor have been acquired to characterize the behavior of the rotor tip clearance flow. The measurements were acquired phase-locked to the rotor position so that changes in the tip clearance vortex position relative to the rotor blade can be seen. The DPIV technique allows the magnitude and relative contributions of both the asynchronous motions of a coherent structure and the temporal unsteadiness to be evaluated. Comparison of measurements taken at the peak efficiency and at near stall operating conditions characterizes the mean position of the clearance vortex and the changes in the unsteady behavior of the vortex with blade loading. Comparisons of the 3-D DPIV measurements at the compressor design point to a 3D steady N-S solution are also done to assess the fidelity of steady, single-passage simulations to model an unsteady flow field.

scholarly journals Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

1994 ◽  
Author(s):  
Kenneth L. Suder ◽  
Mark L. Celestina
Keyword(s):  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Peak Efficiency ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Design Speed

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock / leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock / vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part speed conditions is also discussed.

Experimental Investigation of the Unsteady Tip Clearance Flow in a Low-Speed Axial Contra-Rotating Compressor

2018 ◽  
Author(s):  
Shaoyuan Yue ◽  
Yangang Wang ◽  
Liguo Wei ◽  
Hao Wang ◽  
Shuanghou Deng
Keyword(s):  
Correlation Analysis ◽  
Dynamic Pressure ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Tip Clearance Flow ◽  
Cross Correlation Analysis ◽  
Clearance Flow ◽  
Tip Clearance Vortex

This paper experimentally investigated the evolution of the tip clearance flow of a CRAC (Contra-Rotating Axial Compressor) test rig by means of high-response dynamic pressure measurements. The unsteady pressure field along both chordwise and circumferential directions in the tip clearance is recorded. The tip clearance vortex trajectory is captured using RMS (Root-Mean Square) method. Pressure spectrum analysis indicates that the unsteadiness of tip clearance vortex occurred when the flow coefficient approaches low enough even in the stable operating point. The unsteadiness of tip clearance vortex gets stronger as the flow coefficient drops until rotating stall occurs. According to this feature, the auto-correlation analysis and the cross-correlation analysis combined probability statistics method are used to work as pre-stall warning methods. In addition to, rotating instability which is caused by disturbances propagating along circumferential direction occurred at some flow condition.

Experimental Demonstration of the Tip Clearance Flow Resonance Behind Compressor Non-Synchronous Vibration

2008 ◽  
Author(s):  
Jean Thomassin ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
Shear Layer ◽  
Rotor Blade ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Experimental Apparatus ◽  
Clearance Flow ◽  
Blade Tip ◽  
Blade Tip Clearance

Non-Synchronous Vibration (NSV) is a particular type of aero-elastic phenomenon where the rotor blades vibrate at non-integral multiples of the shaft rotational frequencies. NSV behaviour appears similar to off-design stall flutter but with a particular blade tip flow evolution. This paper demonstrates the link between NSV and the resonance induced by the tip clearance flow, based on a proposed hypothesis. At off-design operating conditions, the rotor blade tip clearance shear layer flow can evolve tangentially. It is proposed that this tangential flow becomes a support for an acoustic feedback wave that settles between rotor blades. The feedback wave is driven by the blade vibratory motion. This forms a closed loop system where the feedback wave synchronizes the shear layer vortical structures with the blade vibration frequency. Depending on the blade tip local temperature, and when the feedback wavelength matches within one or two blade pitches, the system becomes resonant and very high vibrations can occur on the blade. An axial stage compressor test rig is used to look into the underlying mechanism behind NSV. The experimental apparatus consists of the first stage of a High Pressure Compressor (HPC) driven by an electric motor. The test section is built to minimize the effects of the adjacent stator blade rows to isolate the role of rotor blade tip clearance flow on NSV. Sensitivity studies are carried out to assess the effects of the rotor blade tip clearance and inlet temperature on NSV. Finally, evidence of the staging phenomena, inherent to the proposed NSV mechanism, is experimentally obtained.

The Tip Clearance Flow Resonance Behind Axial Compressor Nonsynchronous Vibration

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Jean Thomassin ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
Shear Layer ◽  
Rotor Blade ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Experimental Apparatus ◽  
Clearance Flow ◽  
Blade Tip ◽  
Blade Tip Clearance

Nonsynchronous vibration (NSV) is a particular type of aero-elastic phenomenon, where the rotor blades vibrate at nonintegral multiples of the shaft rotational frequencies. NSV behavior appears similar to off-design stall flutter but with a particular blade tip flow evolution. This paper demonstrates the link between NSV and the resonance induced by the tip clearance flow based on a proposed hypothesis and experimental confirmation. At off-design operating conditions, the rotor blade tip clearance shear layer flow can evolve tangentially. It is proposed that this tangential flow becomes a support for an acoustic feedback wave that settles between rotor blades. The feedback wave is driven by the blade vibratory motion and synchronizes the shear layer vortical structures with the blade vibration frequency. Depending on the blade tip local temperature, and when the feedback wavelength matches within one or two blade pitches, the system becomes resonant and very high vibrations can occur on the blade. An axial stage compressor test rig is set-up to look into the underlying mechanism behind NSV through targeted measurements using both static and rotating instrumentation. The experimental apparatus consists of the first stage of a high pressure compressor driven by an electric motor. The test-section is built to minimize the effects of the adjacent stator blade rows in order to isolate the role of rotor blade tip clearance flow on NSV. Sensitivity studies are carried out to assess and demonstrate the effects of the rotor blade tip clearance and inlet temperature on NSV and validate the predicted resonance for NSV occurrence under various conditions. Vibrations and surface pressure data from adjacent blades are collected to demonstrate the predicted interactions between neighboring rotor blades. Finally, evidence of the staging phenomenon, inherent to the proposed NSV mechanism, is experimentally obtained. All the data obtained are consistent with and thus in support of the proposed mechanism for NSV.

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