An Enhanced Greitzer Compressor Model Including Pipeline Dynamics and Surge

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Se Young Yoon ◽  
Zongli Lin ◽  
Christopher Goyne ◽  
Paul E. Allaire
Keyword(s):  
System Dynamics ◽  
Centrifugal Compressor ◽  
Pressure Rise ◽  
Wide Frequency Range ◽  
Tip Clearance ◽  
Stable Operation ◽  
Compression System ◽  
Output Pressure ◽  
Theoretical Frequency ◽  
Measured Response

The modeling of a centrifugal compressor system with exhaust and plenum piping acoustics is presented in this paper. For an experimental centrifugal compressor test rig with modular inlet and exhaust piping, a mathematical model of the system dynamics is derived based on the Greitzer compression system model. In order to include the dynamics of the piping acoustics, a transmission line model is added to the original compressor equations and different compressor-piping configurations were tested. The resulting mathematical representations of the compression system dynamics are compared with the measured response of the experimental setup. Employing active magnetic bearings to perturb the axial impeller tip clearance of the compressor, the compression system is excited over a wide frequency range and the input-output response from the impeller tip clearance to the plenum pressure rise is analyzed. Additionally, the simulated surge oscillations are compared with the measured response in the surge condition. A good agreement is observed between the experimental and theoretical frequency responses of from the tip clearance to the output pressure, both in stable operation and during surge.

scholarly journals Active Stabilization of Centrifugal Compressor Surge

1990 ◽  
Author(s):  
J. E. Pinsley ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
E. M. Greitzer
Keyword(s):  
Centrifugal Compressor ◽  
Control Strategies ◽  
Pressure Rise ◽  
Control Valve ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Time Resolved ◽  
Compression System ◽  
Compressor Surge ◽  
Surge Line

Active suppression of centrifugal compressor surge has been demonstrated on a centrifugal compressor equipped with a servo-actuated plenum exit throttle controller. The control scheme is fundamentally different from conventional surge control techniques in that it addresses directly the dynamic behavior of the compression system to displace the surge line to lower mass flows. The method used is to feed back perturbations in plenum pressure rise, in real time, to a fast acting control valve. The increased aerodynamic damping of incipient oscillations due to the resulting valve motion allows stable operation past the normal surge line. For the compressor used, a 25% reduction in the surge point mass flow was achieved, over a range of speeds and pressure ratios. Time-resolved measurements during controlled operation revealed that the throttle required relatively little power to suppress the surge oscillations, because the disturbances are attacked in their initial stages. Although designed for operation with small disturbances, the controller was also able to eliminate existing, large amplitude, surge oscillations. Comparison of experimental results with theoretical predictions showed that a lumped parameter model appeared adequate to represent the behavior of the compression system with the throttle controller and, perhaps more importantly, to be used in the design of more sophisticated control strategies.

Active Stabilization of Centrifugal Compressor Surge

1991 ◽  
Vol 113 (4) ◽  
pp. 723-732 ◽  
Author(s):  
J. E. Pinsley ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
E. M. Greitzer
Keyword(s):  
Centrifugal Compressor ◽  
Control Strategies ◽  
Pressure Rise ◽  
Control Valve ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Time Resolved ◽  
Compression System ◽  
Compressor Surge ◽  
Surge Line

Active suppression of centrifugal compressor surge has been demonstrated on a centrifugal compressor equipped with a servo-actuated plenum exit throttle controller. The control scheme is fundamentally different from conventional surge control techniques in that it addresses directly the dynamic behavior of the compression system to displace the surge line to lower mass flows. The method used is to feed back perturbations in plenum pressure rise, in real time, to a fast-acting control valve. The increased aerodynamic damping of incipient oscillations due to the resulting valve motion allows stable operation past the normal surge line. For the compressor used, a 25 percent reduction in the surge point mass flow was achieved over a range of speeds and pressure ratios. Time-resolved measurements during controlled operation revealed that the throttle required relatively little power to suppress the surge oscillations, because the disturbances are attacked in their initial stages. Although designed for operation with small disturbances, the controller was also able to eliminate existing, large-amplitude, surge oscillations. Comparison of experimental results with theoretical predictions showed that a lumped parameter model appeared adequate to represent the behavior of the compression system with the throttle controller and, perhaps more importantly, to be used in the design of more sophisticated control strategies.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

scholarly journals Experimental Investigation of Centrifugal Compressor Stabilization Techniques

2003 ◽  
Author(s):  
Gary J. Skoch
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
External Source ◽  
Tip Clearance ◽  
Stable Operation ◽  
Injection Angle ◽  
Surge Margin ◽  
Air Supply ◽  
Stabilizing Effect ◽  
Design Speed

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection vs. bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

Effect of the tip clearance variation on the performance of a centrifugal compressor with considering impeller deformation

2011 ◽  
Vol 225 (8) ◽  
pp. 1143-1155 ◽  
Author(s):  
H-L Wang ◽  
G Xi ◽  
J-Y Li ◽  
M-J Yuan
Keyword(s):  
Centrifugal Compressor ◽  
Great Influence ◽  
Pressure Rise ◽  
Aerodynamic Performance ◽  
Structure Design ◽  
Tip Clearance ◽  
Working Environment ◽  
Field Analysis ◽  
The Real ◽  
Aerodynamic Pressure

The effects of impeller tip clearance variation on centrifugal compressor performance have been investigated experimentally and numerically in a centrifugal compressor. In order to accurately calculate the real tip clearance, the influence of impeller geometry deformation caused by the thermal load (temperature variation) and mechanical loads (aerodynamic pressure and centrifugal force) under working condition on the compressor aerodynamic performance is taken into account by fluid/solid interaction method during the computational fluid dynamics flow field analysis process. In this article, tip clearance flow under the real working environment is investigated with three different tip clearance cases. The impeller deformation combined with the adjustment of tip clearance causes some influence on the aerodynamic performance and on the structure reliability of the compressor system. For the aerodynamic design, an increase in the impeller tip clearance decreases the overall pressure rise and isentropic efficiency of the compressor, mainly due to the tip clearance loss in the impeller. Regarding structure design, the uniform relative tip clearance from the inlet to the outlet CR = 7.3 per cent is changed to non-uniform distribution from 6.4 per cent to 4.15 per cent. The largest deformation location occurs at the blade inducer and trailing-edge tip. The relative clearance near the outlet of the blade is reduced about 3.15 per cent which will cause great influence on the impeller working reliability.

Clearance Effects on Centrifugal Compressor Characteristic and Stability

2007 ◽  
Author(s):  
Yong Sang Yoon ◽  
Shin Hyung Kang ◽  
Seung Jin Song
Keyword(s):  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Component Level ◽  
Stall Inception ◽  
Stability Model ◽  
Number Of Cells

The effects of impeller inlet tip clearance and diffuser width on centrifugal compressor characteristic and stability have been experimentally investigated in a centrifugal compressor with a vaneless diffuser. An increase in the impeller inlet tip clearance decreases the overall pressure rise across the compressor, mainly due to the tip clearance loss in the impeller. However, the effect of inlet tip clearance on diffuser pressure rise or compressor stability is weak. A decrease in the diffuser width significantly lowers the compressor pressure rise, especially at hight flow rates. At the component level, the impeller is insensitive to the diffuser width variation, and the pressure rise across the diffuser actually increases as diffuser width is decreased. Upon further investigation, it has been found that the overall compressor characteristic is strongly influenced by the region between the impeller exit and the diffuser inlet. Also, a decrease in the diffuser width delays stall inception by increasing the radial velocity of the flow in the diffuser. Thus, the stalling flow coefficient is more sensitive to the variation in the diffuser than the inlet tip clearance. In all cases, rotating stall consists of two or three cells rotating at about approximately one tenth of the compressor rotational speed. When the number of cells changes from three to two, the rotational speed drops. However, when the number of cells remains constant, the cells’ rotational speed increases as flow coefficient is lowered. All of these trends agree well with predictions from a new stability model developed by the first author.

Study of the Flow in Centrifugal Compressor

2009 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Method ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Low Flow ◽  
High Pressure Ratio ◽  
Surge Margin

An unshrouded centrifugal compressor would give up clearance very large in relation to the span of the blades, because centrifugal compressors produce a sufficiently large pressure rise in fewer stages. This problem is more acute for a low flow high-pressure ratio impeller. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range for a centrifugal compressor is a great challenge. This paper describes a new development of high efficiency and a large surge margin flow coefficient of 0.145 centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in this centrifugal compressor design. The new compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A three-dimensional low solidity diffuser design method is proposed and applied to this design. This design demonstrated to be successful to extend the low solidarity diffusers to high-pressure ratio compressor. The design performance range showed the total to static efficiency of the compressor being about 85% and stability range over 35%. The experimental results showed that the test results are in good agreement with the design.

Aerodynamic Effects in a Transonic Compressor With Nonaxisymmetric Tip Clearance

2018 ◽  
Author(s):  
Maximilian Jüngst ◽  
Samuel Liedtke ◽  
Heinz Peter Schiffer ◽  
Bernd Becker
Keyword(s):  
Mass Flow ◽  
Current Knowledge ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Stability Margin ◽  
Tip Clearance ◽  
Stable Operation ◽  
Stall Inception ◽  
Transonic Compressor ◽  
Eccentric Rotor

Future axial compressor designs tend to be built with larger relative tip gaps and eccentricity, since the core engines are reduced in size. Our knowledge of the aerodynamic effects due to eccentric tip gaps is largely based on low-speed work. The aim of this study is to widen current knowledge by using the 1.5 stage Darmstadt Transonic Compressor, which is representative of the front stage of a high pressure compressor. Efficiency, peak pressure rise and stability margin of the compressor are reduced linearly at design speed when the tip clearance is increased from 0.9% to 2.5% tip chord length. This holds true for configurations with eccentric rotor tip gap, if their circumferentially averaged gaps are considered. For a compressor with 96% eccentricity and 1.7% average tip clearance, corrected mass flow at rotor exit varies locally with up to ±20% and ±10% at stator exit, which can result in inlet distortions for subsequent stages in a multi-stage configuration. Also, the redistribution of flow massively influences stall inception during throttling at constant speed. Propagating disturbances are damped in sectors with higher inlet mass flow and lower incidence. Thus, overall operation remains stable, even though some sectors are highly disturbed. Consequently, the maximum clearance of an eccentric stage is not limiting the stable operation of the whole stage.

Numerical Investigation of Unsteady Shock Wave Motion in a Transonic Centrifugal Compressor

2017 ◽  
Author(s):  
Richard Amankwa Adjei ◽  
Weizhe Wang ◽  
Jishen Jiang ◽  
Yingzheng Liu ◽  
Tomoki Kawakubo
Keyword(s):  
Boundary Layer ◽  
Centrifugal Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Boost Pressure ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Shock Unsteadiness ◽  
Transonic Centrifugal Compressor ◽  
The Impact

In order to meet the requirements of automobile engines and marine-use diesel engines, turbochargers must be developed with high boost pressure and appreciably high levels of efficiency. The high pressure rise typically achieved in transonic compressors lead to a stage characterized by high inlet relative Mach numbers. Losses generated in transonic compressors are to a large extent due to the formation of shockwaves at the inducer with interactions between the shock, tip leakage vortex and boundary layer. Significant efficiency reduction occurs at the tip region of the impeller due to the complex interaction of the tip clearance flow and shocks, resulting in significant overall performance degradation. A study has been conducted on the unsteady motion of shockwaves in a transonic centrifugal compressor with vaned diffuser using time-resolved three-dimensional Reynolds average Navier-Stokes simulation. Focus is placed on the impact of the shock motion and post shock unsteadiness on stage performance and impeller-diffuser interaction. The key findings were that the interaction of the shockwave with the tip leakage flow and the boundary layer were the most influential in loss generation with a consequence of increased aerodynamic loss. For the unsteady blade row interaction, the influence of upstream flow unsteadiness on diffuser vanes had significant effect on the flow incidence angle. Periodic jet and wake structure from the impeller and the progressive pressure waves which interacts with the vanes at the interface strongly determines the intensity and position of the vane shock. This has implications on performance in terms of stall inception and static pressure rise across the diffuser.

scholarly journals Experimental Investigation of Centrifugal Compressor Stabilization Techniques

2003 ◽  
Vol 125 (4) ◽  
pp. 704-713 ◽  
Author(s):  
Gary J. Skoch
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
External Source ◽  
Tip Clearance ◽  
Stable Operation ◽  
Injection Angle ◽  
Surge Margin ◽  
Air Supply ◽  
Stabilizing Effect ◽  
Design Speed

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 6.5 points of additional surge margin over the baseline surge margin of 11.7 points.

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