scholarly journals Stall Mode Transformation in the Wide Vaneless Diffuser of Centrifugal Compressors

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6067
Author(s):  
Yaguang Heng ◽  
Bo Hu ◽  
Qifeng Jiang ◽  
Zhengwei Wang ◽  
Xiaobing Liu
Keyword(s):  
Critical Condition ◽  
Characteristic Time ◽  
Rotating Stall ◽  
Large Radius ◽  
Time Analysis ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Mode Transformation ◽  
Stall Cells ◽  
Tangential Directions

A review on the rotating stall in the vaneless diffuser of centrifugal compressors is presented showing that different stall modes characterized by different numbers of cells can be detected within the diffuser even if the operating condition remains unchanged. The interaction between the inlet perturbation and the stall cells near the diffuser outlet is supposed to be the trigger of the stall mode transformation. In order to determine if the inlet perturbation will interact with the downstream stall cells, a characteristic time analysis is proposed to estimate the characteristic time of the perturbation in radial and tangential directions. An additional theoretical model which focused on the development of the vaneless diffuser rotating stall is presented to determine the propagation velocity of the cells. The comparison between the characteristic time in two directions shows that one stall mode is able to evolve into another stall mode if a critical condition is met, and the stall mode transformation is more likely to start from a mode with a higher number of cells and is more likely to occur in the diffuser with a large radius ratio. Experimental results are also employed to validate the proposed critical condition, and good agreements are obtained.

Effects of Non-Axisymmetric Volute on Rotating Stall in the Vaneless Diffuser of a Centrifugal Compressor

2020 ◽  
Author(s):  
Zitian Niu ◽  
Zhenzhong Sun ◽  
Baotong Wang ◽  
Xinqian Zheng
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Stability Boundary ◽  
Rotating Stall ◽  
Evolution Process ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Centrifugal Compressors ◽  
Specific Location

Abstract Rotating stall is an important unstable flow phenomenon that leads to performance degradation and limits the stability boundary in centrifugal compressors. The volute is one of the sources to induce the non-axisymmetric flow in a centrifugal compressor, which has an important effect on the performance of compressors. However, the influence of volute on rotating stall is not clear. Therefore, the effects of volute on rotating stall by experimental and numerical simulation have been explored in this paper. It’s shown that one rotating stall cell generates in a specific location and disappears in another specific location of the vaneless diffuser as a result of the distorted flow field caused by the volute. Also, the cells cannot stably rotate in a whole circle. The frequency related to rotating stall captured in the experiment is 43.9% of the impeller passing frequency (IPF), while it is 44.7% of IPF captured by three-dimensional unsteady numerical simulation, which proves the accuracy of the numerical method in this study. The numerical simulation further reveals that the stall cell initialized in a specific location can be split into several cells during the evolution process. The reason for this is that the blockage in the vaneless diffuser induced by rotating stall is weakened by the mainstream from the impeller exit to make one initialized cell disperse into several ones. The volute has an important influence on the generation and evolution process of the rotating stall cells of compressors. By optimizing volute geometry to reduce the distortion of the flow field, it is expected that rotating stall can be weakened or suppressed, which is helpful to widen the operating range of centrifugal compressors.

Some Guidelines for the Experimental Characterization of Vaneless Diffuser Rotating Stall in Stages of Industrial Centrifugal Compressors

2014 ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Marco Giachi ◽  
Elisabetta Belardini ◽  
Libero Tapinassi ◽  
...  
Keyword(s):  
Dynamic Pressure ◽  
Industrial Test ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Design Parameters ◽  
Accurate Estimation ◽  
Pressure Measurements ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Test Models

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors, as it is often connected with the onset of detrimental subsynchronous vibrations which can prevent the machine from operating beyond this limit. With particular reference to the vaneless diffuser stall, much research has been directed at investigating the physics of the phenomenon, the influence of the main design parameters and the prediction of the stall inception. Few of them, however, focused attention on the evaluation of the aerodynamic unbalance due to the induced pressure field in the diffuser, which, however, could provide a valuable contribution to both the identification of the actual operating conditions and the enhancement of the compressor operating range by a suitable choice of the control strategy. Although advanced experimental techniques have been successfully applied to the recognition of the stall pattern in a vaneless diffuser, the most suitable solution for a wider application in industrial test-models is based on dynamic pressure measurements by means of a reduced number of probes. Within this context, a procedure to transpose pressure measurements into the spatial pressure distribution was developed and validated on a wide set of industrial test-models. In this work, the main guidelines of the procedure are presented and discussed, with particular reference to signals analysis and manipulation as well as sensors positioning. Moreover, the prospects of using a higher number of sensors is analyzed and compared to standard solutions using a limited probes number.

scholarly journals ЗБІЛЬШЕННЯ ДІАПАЗОНУ СТІЙКОЇ РОБОТИ СТУПЕНЯ ВІДЦЕНТРОВОГО КОМПРЕСОРА З БЕЗЛОПАТКОВИМ ДИФУЗОРОМ

2019 ◽  
pp. 4-9
Author(s):  
Микола Васильович Калінкевич ◽  
Микола Іванович Радченко
Keyword(s):  
Mathematical Model ◽  
Gas Injection ◽  
Rotating Stall ◽  
Low Flow ◽  
Stable Operation ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Flow Separation Control ◽  
Flow Part ◽  
Vaneless Diffusers

Centrifugal compressors often operate at different capacities, so it is important to ensure their stable operation over a wide flow range. Stages with vaneless diffusers have several advantages compared to stages with other types of diffusers: they are more technologically advanced to manufacture, and more uniform pressure distribution behind the impeller improves the dynamics of the rotor. At low flows, due to the occurrence of a rotating stall and surge, the efficiency of stages with vaneless diffusers rapidly decreases. The occurrence of unstable operating modes of centrifugal compressor stages at low flow rates is associated with the appearance of developed backflows in the flow part. To expand the range of stable operation of the stages, it is necessary to use methods of flow separation control. Separation of the flow can be controlled either by special profiling the flow part channels or by actively influencing the flow, for example, by injecting gas. To solve this problem, a mathematical model of the gas flow in a vaneless diffuser with gas injection is developed. The characteristics and parameters of the flow in the vaneless diffusers with various meridional profiles with and without injecting gas were calculated. A comparison of the calculated and experimental characteristics of the vaneless diffusers and flow parameters in diffusers with different geometries and with different injection modes confirms the adequacy of the mathematical model. Investigations have confirmed the possibility of improving the characteristics of the stages of centrifugal compressors through the use of vaneless diffusers and diffusers with gas injection. Gas injection diffusers extend the stable operation range of the stages. The use of gas injection in a vaneless diffuser allows reducing the power consumption during antisurge control in comparison with the widespread bypass suction system at the entrance to the impeller

scholarly journals Rotating Stall in Vaneless Diffuser of Large Radius Ratio.

1995 ◽  
Vol 61 (591) ◽  
pp. 3842-3847
Author(s):  
Jun Matsui ◽  
Junichi Kurokawa ◽  
Michiharu Mino ◽  
Eiji Hiroki ◽  
Takaya Kitahora
Keyword(s):  
Rotating Stall ◽  
Radius Ratio ◽  
Large Radius ◽  
Vaneless Diffuser

A Systematic Approach to Estimate the Impact of the Aerodynamic Force Induced by Rotating Stall in a Vaneless Diffuser on the Rotordynamic Behavior of Centrifugal Compressors

2013 ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Elisabetta Belardini ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Journal Bearings ◽  
Rotating Stall ◽  
Squeeze Film ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
The Impact

One of the main challenges of the present industrial research on centrifugal compressors is the need of extending the left margin of the operating range of the machines. As a result, interest is being paid in accurately evaluating the amplitude of the pressure fluctuations caused by rotating stall, which usually occurs prior to surge. The related aerodynamic force acting on the rotor can produce subsynchronous vibrations, which can prevent the machine to further operate, in case their amplitude is too high. These vibrations are often contained thanks to the stiffness of the oil journals. Centrifugal compressors design is, however, going towards alternative journal solutions having lower stiffness levels (e.g. Active Magnetic Bearings or Squeeze Film Dampers), which hence will be more sensitive to this kind of excitation: consequently, a more accurate estimation of the expected forces in presence of dynamic external forces like those connected to an aerodynamically unstable condition is needed to predict the vibration level and the compressor operability in similar conditions. Within this scenario, experimental tests were carried out on an industrial impeller operating at high peripheral Mach number. The dedicated test rig was equipped with several dynamic pressure probes that were inserted in the gas flow path; moreover, the rotor vibrations were constantly monitored with typical vibration probes located near the journal bearings. The pressure field induced by the rotating stall in the vaneless diffuser was reconstructed by means of an ensemble average approach, defining the amplitude and frequency of the external force acting on the impeller. The calculated force value was then included in the rotordynamic model of the test rig: the predicted vibrations on the bearings were compared with the measurements, showing satisfactory agreement. Finally, the prospects of the proposed approach are discussed by investigating the response of a real machine in high-pressure functioning when different choices of journal bearings are made.

A Systematic Approach to Estimate the Impact of the Aerodynamic Force Induced by Rotating Stall in a Vaneless Diffuser on the Rotordynamic Behavior of Centrifugal Compressors

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Alessandro Bianchini ◽  
Davide Biliotti ◽  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Elisabetta Belardini ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Pressure ◽  
Journal Bearings ◽  
Rotating Stall ◽  
Squeeze Film ◽  
Accurate Estimation ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Centrifugal Compressors ◽  
The Impact

One of the main challenges of the present industrial research on centrifugal compressors is the need for extending the left margin of the operating range of the machines. As a result, interest is being paid to accurately evaluating the amplitude of the pressure fluctuations caused by rotating stall, which usually occurs prior to surge. The related aerodynamic force acting on the rotor can produce subsynchronous vibrations, which can prevent the machine's further operation, in case their amplitude is too high. These vibrations are often contained due to the stiffness of the oil journals. Centrifugal compressor design is, however, going towards alternative journal solutions having lower stiffness levels (e.g., active magnetic bearings or squeeze film dampers), which will be more sensitive to this kind of excitation: consequently, a more accurate estimation of the expected forces in the presence of dynamic external forces such as those connected to an aerodynamically unstable condition is needed to predict the vibration level and the compressor operability in similar conditions. Within this scenario, experimental tests were carried out on industrial impellers operating at high peripheral Mach numbers. The dedicated test rig was equipped with several dynamic pressure probes that were inserted in the gas flow path; moreover, the rotor vibrations were constantly monitored with typical vibration probes located near the journal bearings. The pressure field induced by the rotating stall in the vaneless diffuser was reconstructed by means of an ensemble average approach, thus defining the amplitude and frequency of the external force acting on the impeller. The calculated force value was then included in the rotordynamic model of the test rig: the predicted vibrations on the bearings were compared with the measurements, showing satisfactory agreement. Moreover, the procedure was applied to two real multistage compressors, showing notable prediction capabilities in the description of rotating stall effects on the machine rotordynamics. Finally, the prospects of the proposed approach are discussed by investigating the response of a real machine in high-pressure functioning when different choices of journal bearings are made.

Application of Low Solidity Vaned Diffusers to Prevent Rotating Stall in Centrifugal Compressors: Experimental Investigation

2003 ◽  
Author(s):  
A. Cellai ◽  
M. De Lucia ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Stall Inception ◽  
And Performance

Rotating stall is a key problem in centrifugal compressors especially for high-pressure applications. Among the several solutions proposed to prevent this problem, low solidity vaned diffusers (LSDs) have been successfully applied. The aim of this research is to find an optimized LSD configuration in terms of stall inception and performance for the tested compressor. The influence of the vane leading and trailing edge radii, maintaining the same solidity and null deflection were investigated. The geometrical parameters of tested configurations were methodically chosen in order to achieve a design of experiment (DOE) analysis. In view of the above, a series of tests on five low solidity vaned diffuser configurations were carried out. Tests allowed determination of 2 different LSDs that showed the best behavior in terms of working range and performance. These LSDs were then compared with the standard and the reduced-width vaneless diffuser to better understand the best solution to the stall problem.

scholarly journals Limits of Rotating Stall and Stall in Vaneless Diffuser of Centrifugal Compressors

1978 ◽  
Author(s):  
Y. Senoo ◽  
Y. Kinoshita
Keyword(s):  
Flow Behavior ◽  
Rotating Stall ◽  
Critical Conditions ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Flow Rates ◽  
Vaneless Diffusers

Based on the theory in Reference (3), the flow behavior is predicted in four vaneless diffusers with different geometries at the flow rates just before rotating stall and just before stall, which have been experimentally determined. Since the predicted velocity distributions at the critical conditions are physically reasonable for rotating stall and for stall are tentatively set so that the critical conditions are predictable using the theory. Prediction is made for two cases for backward leaning blade impellers and three cases for radial blade impellers in the literature in addition to the authors’ experiments. Satisfactory results are obtained except one example.

Effects of Non-Axisymmetric Volute On Rotating Stall in the Vaneless Diffuser of Centrifugal Compressors

2022 ◽  
Author(s):  
Zitian Niu ◽  
Zhenzhong Sun ◽  
Baotong Wang ◽  
Xinqian Zheng
Keyword(s):  
Flow Field ◽  
Stability Boundary ◽  
Rotating Stall ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Centrifugal Compressors ◽  
Cfd Simulations ◽  
Specific Location ◽  
Stable Operating ◽  
The Stability

Abstract Rotating stall is an important unstable flow phenomenon that leads to performance degradation and limits the stability boundary in centrifugal compressors. The volute is one of the sources inducing non-axisymmetric flows in centrifugal compressors, which has an important effect on compressors' aerodynamic performance. However, the influence of volute on rotating stall is unclear. Therefore, the effects of volute on rotating stall behavior have been explored in this paper by experiments and numerical simulations. The frequency of the rotating stall captured by the experiments is 43.9% of the impeller passing frequency, while it is 44.7% of IPF calculated from the numerical results, which proves the accuracy and capability of the numerical method in this work to study the rotating stall behavior. The flow fields from CFD simulations further reveal that one stall cell initializing in a particular location deforms into several stall cells while rotating along the circumferential direction and becomes much smaller in a specific location during the evolution process, and finally, it is suppressed in another specific location as a result of the distorted flow field caused by the volute. By optimizing volute geometry to reduce the distortion of the flow field, it is expected that the rotating stall can be weakened or suppressed, which is helpful to extend the stable operating range of centrifugal compressors.

Sign in / Sign up

Export Citation Format

Share Document