Recirculation Zones During the Centrifugal Compressor Surge Cycle: CFD Simulation

2020 ◽  
Author(s):  
Michał Kulak ◽  
Filip Grapow ◽  
Grzegorz Liśkiewicz
Keyword(s):  
Centrifugal Compressor ◽  
Cfd Simulation ◽  
Spatial Dimension ◽  
Flow Recirculation ◽  
Pressure Setting ◽  
Main Target ◽  
Compressor Surge ◽  
Key Issues ◽  
Unsteady Rans ◽  
Recirculation Zones

Abstract In this paper the flow recirculation regions during the full surge cycle were described. It is a known fact that the surge cycle consists of two periods: backflow and recovery. The aim of this paper is to add spatial dimension to this analysis. Therefore, the main target is to identify the regions of backflow and recirculation throughout the surge cycle. The full surge cycle modelled with an application of unsteady RANS methods is demonstrated — the significant push was put to realistic boundary conditions definition, narrowed to establishing pressure setting at both inlet and outlet positions located far from the impeller. The results show that all the backflow appears in the recirculation zones that grow and diminish throughout the surge cycle. The regions of inflow and backflow can concurrently exist at different stages of the surge. The analysis includes areas occupied by both structures and mass flowrates associated with them. Presented research is a part of a project aiming at design and construction of more efficient anti-surge systems. Its overall target is to eventually introduce the anti-surge systems that are made to fit the particular machine. Therefore, the understanding of local flows during and prior to surge are one of the key issues that need to be interpreted.

3D CFD Approach to Predict the Performance of a Centrifugal Compressor With Surge and Choke Limits

2021 ◽  
Author(s):  
Abishek Sriram ◽  
Jeff Schlautman ◽  
Mehul Varshney ◽  
Dipak Maiti ◽  
Shyam Sundar Pasunurthi ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Cfd Simulation ◽  
Pressure Ratio ◽  
Low Flow ◽  
Design Stage ◽  
Test Bed ◽  
Process Industries ◽  
Flow Rates ◽  
Compressor Surge ◽  
Wear And Tear

Abstract Centrifugal compressor has widespread applications in areas such as aerospace, automotive, power and process industries and hence the prediction of its performance is crucial at the design stage. Traditional design, build and test are accelerated through numerical simulation as a virtual test bed for compressor development. In this work, a CFD methodology has been developed to predict the performance of a centrifugal compressor with its surge and choke limits. The transient, compressible flow in a moving domain with body-fitted unstructured mesh is solved in Simerics-MP. The distributed parallel solver of Simerics-MP enables to perform the complete performance map of a centrifugal compressor in a day. The phenomena of surge and choke in a centrifugal compressor is of paramount importance as it determines the limiting points of operation for a particular speed of the compressor. Surge occurs at low flow rates, and it is characterized by instabilities causing undesirable noises that lead to drop in the operational efficiency. It can also result in wear and tear of the impeller blades. Whereas choke occurs at high flow rates with no further increase in pressure and it is accompanied by aberrant vibrations. The CFD simulation predicts the instabilities occurring at surge such as pressure oscillations and flow reversal accurately, which is used as a criterion for the prediction of surge point. The choke phenomenon is characterized by fluid attaining sonic velocity in the impeller or diffuser region of the compressor. The CFD predicted results showed a fair comparison with the experimental results of pressure ratio, power, and efficiency at different speeds.

Flow recirculation zone length and shear rate are differentially affected by stenosis severity in human coronary arteries

2013 ◽  
Vol 304 (4) ◽  
pp. H559-H566 ◽  
Author(s):  
Ashkan Javadzadegan ◽  
Andy S. C. Yong ◽  
Michael Chang ◽  
Austin C. C. Ng ◽  
John Yiannikas ◽  
...  
Keyword(s):  
Shear Rate ◽  
Coronary Arteries ◽  
Recirculation Zone ◽  
Fluid Dynamic ◽  
Zone Length ◽  
Flow Recirculation ◽  
Stenosis Severity ◽  
Recirculation Zones ◽  
The Relationship

Flow recirculation zones and shear rate are associated with distinct pathogenic biological pathways relevant to thrombosis and atherogenesis. The interaction between stenosis severity and lesion eccentricity in determining the length of flow recirculation zones and peak shear rate in human coronary arteries in vivo is unclear. Computational fluid dynamic simulations were performed under resting and hyperemic conditions on computer-generated models and three-dimensional (3-D) reconstructions of coronary arteriograms of 25 patients. Boundary conditions for 3-D reconstructions simulations were obtained by direct measurements using a pressure-temperature sensor guidewire. In the computer-generated models, stenosis severity and lesion eccentricity were strongly associated with recirculation zone length and maximum shear rate. In the 3-D reconstructions, eccentricity increased recirculation zone length and shear rate when lesions of the same stenosis severity were compared. However, across the whole population of coronary lesions, eccentricity did not correlate with recirculation zone length or shear rate ( P = not signficant for both), whereas stenosis severity correlated strongly with both parameters ( r = 0.97, P < 0.001, and r = 0.96, P < 0.001, respectively). Nonlinear regression analyses demonstrated that the relationship between stenosis severity and peak shear was exponential, whereas the relationship between stenosis severity and recirculation zone length was sigmoidal, with an apparent threshold effect, demonstrating a steep increase in recirculation zone length between 40% and 60% diameter stenosis. Increasing stenosis severity and lesion eccentricity can both increase flow recirculation and shear rate in human coronary arteries. Flow recirculation is much more sensitive to mild changes in the severity of intermediate stenoses than is peak shear.

High speed centrifugal compressor surge initiation characterization

1996 ◽  
Author(s):  
William Oakes ◽  
Patrick Lawless ◽  
John Fagan ◽  
Sanford Fleeter
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Compressor Surge

Flow Behavior of a Centrifugal Compressor With Vaneless Diffuser at Design and Off Design Conditions

2012 ◽  
Author(s):  
Chuang Gao ◽  
Weiguang Huang ◽  
Haiqing Liu ◽  
Hongwu Zhang ◽  
Jundang Shi
Keyword(s):  
Centrifugal Compressor ◽  
Flow Behavior ◽  
Travelling Waves ◽  
Leading Edge ◽  
Pressure Oscillation ◽  
Rotating Stall ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Flow Recirculation ◽  
Static Performance

This paper concerns with the numerical and experimental aspects of both steady and unsteady flow behavior in a centrifugal compressor with vaneless diffuser and downstream collector. Specifically, the appearance of flow instabilities i.e., rotating stall and surge is investigated in great detail. As the first step, the static performance of both stage and component was analyzed and possible root cause of system surge was put forward based on the classic stability theory. Then the unsteady pressure data was utilized to find rotating stall and surge in frequency domain which could be classified as mild surge and deep surge. With the circumferentially installed transducers at impeller inlet, backward travelling waves during stall ramp could be observed. The modes of stall waves could be clearly identified which is caused by impeller leading edge flow recirculation at Mu = 0.96. However, for the unstable flow at Mu = 1.08, the system instability seems to be caused by reversal flow in vaneless diffuser where the pressure oscillation was strongest. Thus steady numerical simulation were performed and validated with the experimental performance data. With the help of numerical analysis, the conjectures are proved.

Multistage Centrifugal Compressor Surge Analysis: Part II—Numerical Simulation and Dynamic Control Parameters Evaluation

1999 ◽  
Vol 121 (2) ◽  
pp. 312-320 ◽  
Author(s):  
G. L. Arnulfi ◽  
P. Giannattasio ◽  
C. Giusto ◽  
A. F. Massardo ◽  
D. Micheli ◽  
...  
Keyword(s):  
Active Control ◽  
Centrifugal Compressor ◽  
Dynamic Control ◽  
Point Of View ◽  
Lumped Parameter Model ◽  
Theoretical Point ◽  
Control Parameters ◽  
Compression System ◽  
Compressor Surge ◽  
Multistage Centrifugal Compressor

This paper describes, from a theoretical point of view, the behavior of compression systems during surge and the effect of passive and active control devices on the instability limit of the system. A lumped parameter model is used to simulate the compression system described in Part I of this work (Arnulfi et al., 1999), based on an industrial multistage centrifugal compressor. A comparison with experimental results shows that the model is accurate enough to describe quantitatively all the features of the phenomenon. A movable wall control system is studied in order to suppress surge in the compressor. Passive and active control schemes are analyzed; they both address directly the dynamic behavior of the compression system to displace the surge line to lower flow rates. The influence of system, geometry and compressor speed is investigated: the optimum values of the control parameters and the corresponding increase in the extent of the stable operating range are presented in the paper.

Dynamic Model of Multistage Centrifugal Compressor With a Stage-by-Stage Anti-Surge Recirculating System

2021 ◽  
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Alessio Suman ◽  
Matteo Manganelli ◽  
Mirko Morini ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Suction Side ◽  
System Level ◽  
Low Flow ◽  
Return Flow ◽  
Control Line ◽  
Compressor Surge ◽  
Surge Control ◽  
Surge Line

Abstract The operability region of a centrifugal compressor is bounded by the low-flow (or high-pressure ratio) limit, commonly referred to as surge. The exact location of the surge line on the map can vary depending on the operating condition and, as a result, a typical Surge Avoidance Line is established at 10% to 15% above the stated flow for the theoretical surge line. The current state of the art of centrifugal compressor surge control is to utilize a global recycle valve to return flow from the discharge side of a centrifugal compressor to the suction side to increase the flow through the compressor and, thus, avoid entering the surge region. This is conventionally handled by defining a compressor surge control line that conservatively assumes that all stages must be kept out of surge at all the time. In compressors with multiple stages, the amount of energy loss is disproportion-ally large since the energy that was added in each stage is lost during system level (or global) recycling. This work proposes an internal stage-wise recycling that provides a much more controlled flow recycling to affect only those stages that may be on the verge of surge. The amount of flow needed for such a scheme will be much smaller than highly conservative global recycling approach. Also, the flow does not leave the compressor casing and therefore does not cross the pressure boundary. Compared to global recycling this inherently has less loss depending upon application and specific of control design.

Three-Dimensional/One-Dimensional Combined Simulation of Deep Surge Loop in a Turbocharger Compressor With Vaned Diffuser

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Ghislaine Ngo Boum ◽  
Rodolfo Bontempo ◽  
Isabelle Trébinjac
Keyword(s):  
System Modeling ◽  
Air Flow ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vaned Diffuser ◽  
One Dimensional ◽  
Compressor Surge ◽  
Important Challenge ◽  
Unsteady Rans ◽  
Combined Simulation

High accuracy simulation of compressor surge origin and growth is an important challenge for designers of systems using compressors likely to develop that severe instability. Indeed, understanding its driving phenomena, which can be system dependent, is necessary to build an adequate strategy to avoid or control surge emergence. Computational fluid dynamics (CFD) simulations, commonly used to explore flow in the compressor, need then to be extended beyond the compressor as surge is a system scale instability. To get an insight on the path to surge and through surge cycles, a reliable alternative to full three-dimensional (3D) system modeling is used for a turbocharger compressor inserted in an experimental test rig. The air flow in the whole circuit, is modeled with a one-dimensional (1D) Navier Stokes approach which is coupled with a 3D unsteady RANS modeling of the 360 deg air flow in the centrifugal compressor including the volute. Starting from an initial stable flow solution in the system, the back-pressure valve is progressively closed to reduce the massflow and trigger the instability. An entire deep surge loop is simulated and compared with good agreement with the experimental data. The existence of a system-induced convective wave is revealed, and its major role on surge inception at diffuser inlet demonstrated.

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