Study on Poincare Plot Characteristics of Dynamic Pressure at Outlet of Centrifugal Compressor Based on Edge Crawling Algorithm

2021 ◽  
Author(s):  
Yan Liu ◽  
Yan Huang ◽  
Jun Xiao
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Poincaré Plot

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.

The Aerodynamics of Three-Dimensional Vaned Diffusers in Industrial Centrifugal Compressors

2005 ◽  
Author(s):  
Ahmed Abdelwahab
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Pressure Recovery ◽  
Navier Stokes ◽  
Spanwise Direction ◽  
Two Dimensional ◽  
Blade Loading ◽  
Recovery Capacity ◽  
Close Proximity

Vaned diffusers have been used successfully as efficient and compact dynamic pressure recovery devices in industrial centrifugal compressor stages. Typically such diffusers consist of a cascade of two-dimensional blades distributed circumferentially at close proximity to the impeller exit. In this paper three low-solidity diffuser blade geometries are numerically investigated. The first geometry employs variable stagger stacking of similar blade sections along the blade span. The second employs linearly inclined stacking to generate blade lean along the diffuser span. The third geometry employs the conventional two-dimensional low-solidity diffuser geometry with no variable stagger or lean. The variable stagger blade arrangement has the potential of better aligning the diffuser leading edges with the highly non-uniform flow leaving the impeller. Both variable stagger and linearly leaned diffuser blade arrangements, however, have the effect of redistributing the blade loading and flow streamlines in the spanwise direction leading to improved efficiency and pressure recovery capacity of the diffuser. In this paper a description of the proposed diffuser geometries is presented. The results of Three-dimensional Navier-Stokes numerical simulations of the three centrifugal compressor arrangements are discussed. Comparisons between the performance of the two and three-dimensional diffuser blade geometries are presented. The comparisons indeed show that the variable stagger and leaned diffusers present an improvement in the diffuser operating range and pressure recovery capacity over the conventional two-dimensional diffuser geometry.

scholarly journals Rotating Stall in Centrifugal Compressor Vaneless Diffuser: Experimental Analysis of Geometrical Parameters Influence on Phenomenon Evolution

2004 ◽  
Vol 10 (6) ◽  
pp. 433-442 ◽  
Author(s):  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Leonardo Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Fast Response ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Response Dynamic ◽  
Frequency Domains

The rotating stall is a key problem for achieving a good working range of a centrifugal compressor and a detailed understanding of the phenomenon is very important to anticipate and avoid it. Many experimental tests have been planned by the authors to investigate the influence on stall behavior of different geometrical configurations. A stage with a backward channel upstream, a 2-D impeller with a vaneless diffuser and a constant cross-section volute downstream, constitute the basic configuration. Several diffuser types with different widths, pinch shapes, and diffusion ratios were tested. The stage was instrumented with many fast response dynamic pressure sensors so as to characterize inception and evolution of the rotating stall. This kind of analysis was carried out both in time and in frequency domains. The methodology used and the results on phenomenon evolution will be presented and discussed in this article.

scholarly journals Descriptions of Entropy with Fractal Dynamics and Their Applications to the Flow Pressure of Centrifugal Compressor

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 266 ◽  
Author(s):  
Yan Liu ◽  
Dongxiao Ding ◽  
Kai Ma ◽  
Kuan Gao
Keyword(s):  
Autocorrelation Function ◽  
Centrifugal Compressor ◽  
Hurst Exponent ◽  
Flow Instability ◽  
Dynamic Pressure ◽  
Stable State ◽  
Nonlinear Dynamic System ◽  
Original Data ◽  
Fractal Spectrum ◽  
Fractal Characteristics

In this study, some important intrinsic dynamics have been captured after analyzing the relationships between the dynamic pressure at an outlet of centrifugal compressor and fractal characteristics, which is one of powerful descriptions in entropy to measure the disorder or complexity in the nonlinear dynamic system. In particular, the fractal dynamics of dynamic pressure of the flow is studied, as the centrifugal compressor is in surge state, resulting in the dynamic pressure of flow and becoming a serious disorder and complex. First, the dynamic pressure at outlet of a centrifugal compressor with 800 kW is tested and then obtained by controlling the opening of the anti-surge valve at the outlet, and both the stable state and surge are initially tested and analyzed. Subsequently, the fractal dynamics is introduced to study the intrinsic dynamics of dynamic pressure under various working conditions, in order to identify surge, which is one typical flow instability in centrifugal compressor. Following fractal dynamics, the Hurst exponent, autocorrelation functions, and variance in measure theories of entropy are studied to obtain the mono-fractal characteristics of the centrifugal compressor. Further, the multi-fractal spectrums are investigated in some detail, and their physical meanings are consequently explained. At last, the statistical reliability of multi-fractal spectrum by modifying the original data has been studied. The results show that a distinct relationship between the dynamic pressure and fractal characteristics exists, including mono-fractal and multi-fractal, and such fractal dynamics are intrinsic. As the centrifugal compressor is working under normal condition, its autocorrelation function curve demonstrates apparent stochastic characteristics, and its Hurst exponent and variance are lower. However, its autocorrelation function curve demonstrates an apparent heavy tail distribution, and its Hurst exponent and variance are higher, as it is working in an unstable condition, namely, surge. In addition, the results show that the multi-fractal spectrum parameters are closely related to the dynamic pressure. With the state of centrifugal compressor being changed from stable to unstable states, some multi-fractal spectrum parameters Δα, Δf(α), αmax, and f(αmin) become larger, but αmin in the multi-fractal spectrum show the opposite trend, and consistent properties are graphically shown for the randomly shuffled data. As a conclusion, the proposed method, as one measure method for entropy, can be used to feasibly identify the incipient surge of a centrifugal compressor and design its surge controller.

scholarly journals An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV

2000 ◽  
Vol 123 (2) ◽  
pp. 418-428 ◽  
Author(s):  
Mark P. Wernet ◽  
Michelle M. Bright ◽  
Gary J. Skoch
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Transient Flow ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Transient Pressure ◽  
Pressure Transducers ◽  
Stable Operating ◽  
Particle Imaging

Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle, and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to control these events successfully. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to capture transient velocity and pressure measurements simultaneously in the nonstationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique that is ideally suited for studying transient flow phenomena in high-speed turbomachinery and has been used previously to map the stable operating point flow field in the diffuser of a high-speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.

Excitation of Blade Vibration due to Surge of Centrifugal Compressors

1992 ◽  
Author(s):  
D. Jin ◽  
U. Haupt ◽  
H. Hasemann ◽  
M. Rautenberg
Keyword(s):  
Centrifugal Compressor ◽  
Rotational Speed ◽  
High Performance ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Blade Vibration ◽  
High Rotational Speed ◽  
Blade Thickness ◽  
Periodic Pressure ◽  
Compressor Surge

Centrifugal compressor surge at high rotational speed and reduced blade thickness can produce dangerous excitation effects which have numerous resulted in problems in the past. This paper presents an investigation of blade excitation during surge in a high performance single stage centrifugal compressor with various impeller and diffuser geometry. The blade vibration was measured using blade mounted strain gages. The flow characteristics during surge as the cause of blade excitation were simultaneously determined by fast response dynamic pressure transducers. The experiments have been performed using a radial and a backswept impeller, as well as a vanless and vaned diffusers. The rotational speed of the compressor was varied from 5,000 to 14,500 rpm. The characteristics of unsteady flow during surge, such as, the flow pattern of rotating stall and the non-periodic pressure fluctuation during surge were studied in detail. The experimental results demonstrated that, in addition to the excitation of rotating stall during surge, strong non-periodic pressure fluctuations at the beginning and the end of the surge induced dangerous blade excitations in all compressor configurations. The maximum strain values of blade vibration for all compressor versions at different rotational speeds of the compressor were measured to estimate the danger of blade excitation during surge. The results showed that the blade excitation during compressor surge with vaned diffusers is stronger than the excitation with a vanless diffuser and that the blade excitation with a radial impeller is stronger than the excitation with a backswept impeller.

scholarly journals Obtaining Information about Operation of Centrifugal Compressor from Pressure by Combining EEMD and IMFE

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 424
Author(s):  
Yan Liu ◽  
Kai Ma ◽  
Hao He ◽  
Kuan Gao
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Stable State ◽  
Time Sequence ◽  
Fuzzy Entropy ◽  
Unstable State ◽  
Intrinsic Mode Functions ◽  
Improved Method ◽  
Multi Scale ◽  
Unstable States

Based on entropy characteristics, some complex nonlinear dynamics of the dynamic pressure at the outlet of a centrifugal compressor are analyzed, as the centrifugal compressor operates in a stable and unstable state. First, the 800-kW centrifugal compressor is tested to gather the time sequence of dynamic pressure at the outlet by controlling the opening of the anti-surge valve at the outlet, and both the stable and unstable states are tested. Then, multi-scale fuzzy entropy and an improved method are introduced to analyze the gathered time sequence of dynamic pressure. Furthermore, the decomposed signals of dynamic pressure are obtained using ensemble empirical mode decomposition (EEMD), and are decomposed into six intrinsic mode functions and one residual signal, and the intrinsic mode functions with large correlation coefficients in the frequency domain are used to calculate the improved multi-scale fuzzy entropy (IMFE). Finally, the statistical reliability of the method is studied by modifying the original data. After analysis of the relationships between the dynamic pressure and entropy characteristics, some important intrinsic dynamics are captured. The entropy becomes the largest in the stable state, but decreases rapidly with the deepening of the unstable state, and it becomes the smallest in the surge. Compared with multi-scale fuzzy entropy, the curve of the improved method is smoother and could show the change of entropy exactly under different scale factors. For the decomposed signals, the unstable state is captured clearly for higher order intrinsic mode functions and residual signals, while the unstable state is not apparent for lower order intrinsic mode functions. In conclusion, it can be observed that the proposed method can be used to accurately identify the unstable states of a centrifugal compressor in real-time fault diagnosis.

Experimental and Numerical Analysis of Unsteady Flow Structure in a Centrifugal Compressor With Variable Vaned Diffuser

2018 ◽  
Author(s):  
Xiang Xue ◽  
Tong Wang ◽  
Yuchang Shao ◽  
Bo Yang ◽  
Chuangang Gu
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Flow Structure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Operating Conditions ◽  
Experimental Result ◽  
Vaned Diffuser ◽  
Tip Leakage ◽  
Stall Precursor

The unsteady flow at small flow rates is always the most important of typical unsteady phenomena in centrifugal compressors, since it is closely related to the operating safety and efficiency. To study the mechanism of stall and surge generation, an experimental research on an industrial centrifugal compressor with variable vaned diffuser is carried out to study the unsteady flow structure from design point to surge. A multi-phase dynamic pressure measurement is conducted, based on 23 dynamic pressure sensors mounted on the shroud side casing surface of the compressor. The sensors are circumferentially distributed in a non-uniform manner at seven different radial positions, including the impeller region, the vaneless region and the diffuser throat region. Real-time data is recorded during the whole valve-adjusting process. The characteristics of pressure fields at some specific operating conditions are focused on, especially the pre-stall, stall precursor, stall and surge conditions. According to the multiphase data association, the originating position of the stall precursor can be determined. The features of the unsteady flow structure are also obtained, such as the surge pattern and the propagation direction of stall cells. In addition, when the diffuser vane setting angle (OGV) is turned up, the core factors to trigger total instability will change. In order to visually show how the tip leakage and separation vortex in the impeller gradually affect the flow structure in the vaned diffuser region and even the whole machine, numerical simulation and dynamic mode decomposition (DMD) method are used to study the flow mechanisms. The numerical simulation result is well matched with the experimental result. With the help of the DMD method, a few low-frequency tip leakage vortex structures are extracted from the unsteady numerical result over a period of time, which correlate with the experimental result. Meanwhile, on this issue, the feasibility of dynamic experimental analysis combined with multi-channel numerical simulation analysis is verified and discussed. Through the two analytic methods, a detailed understanding of the unsteady flow structure in the centrifugal compressor with variable vaned diffuser is obtained.

The Influence of Low Solidity Vaned Diffusers on the Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute

2000 ◽  
Author(s):  
James M. Sorokes ◽  
Jay M. Koch
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Dynamic Pressure ◽  
Pressure Profile ◽  
Vaneless Diffusers ◽  
Discharge Pressure ◽  
Dynamics Analyses ◽  
Work Done

The paper is a sequel to an earlier work by Sorokes et al. 1998, “Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute.” The earlier work described experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor with vaneless diffusers. This paper describes additional testing and analytical work done using low solidity vaned diffusers (LSD’s) in place of select vaneless diffusers to determine the alternate diffuser’s effectiveness in eliminating or reducing the magnitude of the non-uniform pressure field. As in the earlier studies, the experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge pressure. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided. Concurrent with the experimental work, CFD runs were completed to study the effect of the alternate vaned diffusers. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data. Conclusions are drawn regarding: a) the effectiveness of the LSD’s on the pressure non-uniformity; b) the associated effects on the measured dynamic strains in the impellers; and c) the usefulness of computational fluid dynamics (CFD) in assessing the aerodynamic forces associated with the non-uniformity.

scholarly journals The Interpretation of Internal Pressure Patterns of Rotating Stall in Centrifugal Compressor Impellers

1993 ◽  
Author(s):  
J. Chen ◽  
H. Hasemann ◽  
U. Seidel ◽  
D. Jin ◽  
X. Huang ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Centrifugal Compressor ◽  
High Performance ◽  
Dynamic Pressure ◽  
Internal Flow ◽  
Pressure Oscillation ◽  
Rotating Stall ◽  
Time Period ◽  
Dynamic Pressure Measurement ◽  
Mixed Pattern

Dynamic pressure measurement on the shroud wall for a high performance single stage centrifugal compressor has been implemented to record the unsteady pressure data during rotating stall. Apart from the frequency analysis of the stall characteristics, a computer-aided method has been developed to enable the unsteady internal pressure patterns inside the blade channel near shroud surface to be described and shown in an animated visualisation. Typical results of internal pressure patterns for a backswept impeller with two cell rotating stall occurrence at the impeller speed of 16000 rpm are presented in detail. The internal flow structure can be interpreted by pressure patterns of three types emerged consecutively within one time period of stall pressure oscillation: the normal pattern, the mixed pattern and the stalled pattern. The mixed pattern is characterized by a coexistence of the reverse movement of high pressure region towards inlet and the inlet separation. The stalled pattern is characterized by a collapse of pressure loadings in the blade channel. Such observation is thought to be useful for exploring the flow mechanism of rotating stall.

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