Application of Scaling to the Analysis of Unstable Flow Phenomena

2015 ◽  
pp. 53-57 ◽  
Author(s):  
J.-Y. Parlange ◽  
T.S. Steenhuis ◽  
R.J. Glass
Keyword(s):  
Unstable Flow ◽  
Flow Phenomena

Experimental Analysis of Surge-Detection System Based on Pressure Derivatives At Part-Speed Operation

2021 ◽  
Author(s):  
Grzegorz Liskiewicz ◽  
Kirill Kabalyk ◽  
Andrzej Jaeschke ◽  
Filip Grapow ◽  
Michal Kulak ◽  
...  
Keyword(s):  
Flow Instability ◽  
Detection System ◽  
Rotating Stall ◽  
Unstable Flow ◽  
Monitoring Point ◽  
Optimal Position ◽  
Flow Disturbances ◽  
Flow Phenomena ◽  
Valve Opening ◽  
Low Mass

Abstract This paper presents tests of an anti-surge system based on pressure derivatives. The control algorithm was proven to work on different machines and with different unstable flow phenomena. Compressors are known to be affected by unstable flow conditions appearing at low mass flow rate conditions. The best known and most dangerous phenomenon is surge, which is a global instability affecting the entire impeller and regions upstream and downstream from it. A list of identified local phenomena includes among others: impeller rotating stall, diffuser rotating stall and inlet recirculation. All have a specific pressure signature that is used for early identification. The method presented in this paper is based on a control parameter named the Rate of Derivative Fluctuation (RDF). This approach involves a simple measure of flow instability that is universal and reacts to flow disturbances. RDF has been already confirmed to identify inlet recirculation and surge. The aim of this study is to conduct real-time tests of an anti-surge system implementing the RDF algorithm triggering the safety valve opening. The study confirmed the optimal position of the monitoring point. The results showed that the RDF is indeed sensitive to different types of flow instabilities appearing in different impellers, and that it provides efficient flow stability monitoring.

Numerical Simulation of Inner Flow in a Double Blades Pump Based on OpenFOAM and its PIV Verification

2012 ◽  
Author(s):  
Yun Ren ◽  
Houlin Liu ◽  
Kai Wang ◽  
Minggao Tan ◽  
Denghao Wu ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Energy Performance ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Unstable Flow ◽  
Software Packages ◽  
Flow Phenomena ◽  
Particle Imaging

The presence of unstable flow phenomena may significantly alter the flow pattern and characteristics of centrifugal pumps; that is, the unstable flows may seriously deteriorate the pumps performance. In this paper, considering the high cost of running license fees and not available with all the computing resources, a high quality Open Source CFD simulation platform like OpenFOAM instead of commercial software packages is adopted. Furthermore, the required capability such as GGI is added and boundary conditions are specialized to better simulate complex flow behavior through rotor-stator components in a double blades pump, whose specific speed is 115.6. In order to disclose the characteristics completely, six research schemes are developed and are now presented in this paper. The ratios (Q/Qd) of the flow rate are 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, respectively. The task mainly focuses on the comparison of energy performance under different operating conditions between numerical calculations and experiments, the analysis of the inner flow in the impeller and the comparison of the velocity field in the impeller mid-height between simulation data and the Particle Imaging Velocimetry (PIV) experimental data. The results show that good agreements are found both in terms of the energy performance with experimental results and computed velocities with the PIV data, but improvements can be made.

scholarly journals Unstable Flow Structures Present at Different Rotational Velocities of the Centrifugal Compressor

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4146
Author(s):  
Grzegorz Liśkiewicz ◽  
Kirill Kabalyk ◽  
Andrzej Jaeschke ◽  
Filip Grapow ◽  
Michał Kulak ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Energy Systems ◽  
Flow Structures ◽  
Spectral Structure ◽  
Flow Conditions ◽  
Unstable Flow ◽  
Closed Type ◽  
Flow Phenomena ◽  
Surge Protection ◽  
Method Accuracy

Unstable flow structures cause inevitable energy losses in all power energy systems, including turbomachines. In this study, a set of analyses was conducted with the use of spectral maps on the pressure signals obtained from an industrial centrifugal compressor. The spectral maps provide one a detailed visualization of the flow conditions present in the machine along the performance curve and to distinguish the flow phenomena present prior to the surge. The method accuracy is especially useful in detecting the inlet recirculation. The study was conducted at four impeller rotational speeds with varying loads imposed by a valve at the outlet. At each speed, the machine experienced different stages of unstable flow conditions prior to the surge. Five main frequency peaks that appeared in all cases were identified and discussed. The surge was observed at all impeller speeds. At lower ones, however, it appeared at higher valve closures. At higher speeds, the surge was much more intense. The study has also shown that the inlet recirculation appears also for the closed-type industrial impeller. The phenomenon was present in all conditions. The higher impeller speed, the faster onset of the inlet recirculation was. This structure has a strong potential for an early instability warning because it appears in various types of impellers, has a very particular spectral structure and its positioning is very predictable. This study gives another example of the inlet recirculation universality and potential for efficient anti-surge protection.

On the Challenge of Determining the Surge Limit of Turbocharger Compressors: Part 2 – Capabilities of a Geometrically Reduced Numerical Model

2021 ◽  
Author(s):  
Dominik Paul ◽  
Johannes Ratz ◽  
Werner Eißler
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Research Paper ◽  
Flow Structures ◽  
Complete Model ◽  
Unstable Flow ◽  
Operation Conditions ◽  
Starting Point ◽  
Flow Phenomena ◽  
Model Setup

Abstract Steady-state numerical simulations are an essential instrument in the design process of centrifugal compressors for automotive turbochargers in an industrial environment. Although this method is state-of-the-art, the natural unsteadiness of the compressor flow especially close to stall and surge is suppressed by this kind of simulation. Unsteady numerical simulations of the complete compressor geometry are necessary to detect unstable flow structures leading to surge. As numerical costs and thus the time needed for unsteady simulations correlate with the size of numerical setup, it is not possible for industrial applications to investigate an unsteady operation condition of a centrifugal compressor. On account of that fact, it would be beneficial to reduce the model and include only the most decisive components which are responsible for the significant flow phenomena within the impeller leading to surge. The objective of this research paper is the investigation of the CFD simulation capabilities of a reduced radial compressor model for steady-state operation conditions using as a robust basis for further transient analysis. Thus, the results of a reduced model setup of one blade segment are compared to a full model setup. It is concluded that the segment model approach is capable of investigating flow phenomena within the impeller without neglecting fundamental flow structures. In addition, the consequences of the geometric reduction to a diffuser segment without volute on different flow variables are studied. This provides the guidance for further transient studies. The complete model setup, in conjunction with its validation by experimental data, serves as the starting point for this research paper. Dielenschneider et al.[1] present in the first part of the paper the procedure and a detailed comparison of complete model results with experimental analysis.

Experimental Analysis of Surge-Detection System Based on Pressure Derivatives at Part-Speed Operation

2020 ◽  
Author(s):  
Grzegorz Liskiewicz ◽  
Kirill Kabalyk ◽  
Andrzej Jaeschke ◽  
Filip Grapow ◽  
Michał Kulak ◽  
...  
Keyword(s):  
Flow Instability ◽  
Detection System ◽  
Rotating Stall ◽  
Unstable Flow ◽  
Monitoring Point ◽  
Optimal Position ◽  
Flow Disturbances ◽  
Flow Phenomena ◽  
Valve Opening ◽  
Low Mass

Abstract This paper presents tests of an anti-surge system based on pressure derivatives. The control algorithm was proven to work on different machines and with different unstable flow phenomena. Compressors are known to be affected by unstable flow conditions appearing at low mass flow rate conditions. The best known and most dangerous phenomenon is surge, which is a global instability affecting the entire impeller and regions upstream and downstream from it. A list of identified local phenomena includes among others: impeller rotating stall, diffuser rotating stall and inlet recirculation. All have a specific pressure signature that is used for early identification. The method presented in this paper is based on a control parameter named the Rate of Derivative Fluctuation (RDF). This approach involves a simple measure of flow instability that is universal and reacts to flow disturbances. RDF has been already confirmed to identify inlet recirculation and surge. The aim of this study is to conduct real-time tests of an anti-surge system implementing the RDF algorithm triggering the safety valve opening. The study confirmed the optimal position of the monitoring point. The results showed that the RDF is indeed sensitive to different types of flow instabilities appearing in different impellers, and that it provides efficient flow stability monitoring.

scholarly journals Dynamical system analysis of unstable flow phenomena in centrifugal blower

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
David Garcia ◽  
Matthew Stickland ◽  
Grzegorz Liśkiewicz
Keyword(s):  
Dynamical System ◽  
Working Conditions ◽  
System Analysis ◽  
Singular Spectrum Analysis ◽  
Statistical Correlation ◽  
Control Points ◽  
Original Signal ◽  
Centrifugal Blower ◽  
Unstable Flow ◽  
Flow Phenomena

AbstractMethods of dynamical system analysis were employed to analyze unsteady phenomena in a centrifugal blower. Pressure signals gathered at different control points were decomposed into their Principal Components (PCs) by means of Singular Spectrum Analysis (SSA). Certain number of PCs was considered in the analysis based on their statistical correlation. Projection of the original signal onto its PCs allowed to draw the phase trajectory that clearly separated non-stable blower working conditions from its regular operation.

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