Detailed measurements of the flow field in vaneless and vaned diffusers of centrifugal compressors

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.

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Analysis of Measurements in Vaned Diffusers of Centrifugal Compressors

Journal of Turbomachinery ◽

10.1115/1.3262156 ◽

1988 ◽

Vol 110 (1) ◽

pp. 115-121 ◽

Cited By ~ 1

Author(s):

W. Stein ◽

M. Rautenberg

Keyword(s):

Flow Field ◽

Flow Structure ◽

Calculation Method ◽

Geometric Parameters ◽

Variable Geometry ◽

Centrifugal Compressors ◽

Wide Range ◽

Performance Curves ◽

Different Types ◽

Flow Phenomena

In vaned diffusers of centrifugal compressors many different flow phenomena interfere with one another, and different geometric parameters influence the flow field. Variations of these parameters allow the designer to optimize the diffuser for a certain application or to use a variable geometry for controlling the stage over a wide range. Two vaned diffusers that differ only in their passage widths are investigated using different types of measuring technique, in order to analyze the flow structure and to use it as a verification of a calculation method that allows detailed predictions of flow field parameters inside the diffuser, by taking into account geometric variations. Using this method predictions of the flow field of a variable geometry diffuser are made and are compared with the measured performance curves of the stage.

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Effects of Airflow Deflection Angle in Diffuser on Forced Response Caused by Impeller-diffuser Interaction in Centrifugal Compressors

MATEC Web of Conferences ◽

10.1051/matecconf/201817901009 ◽

2018 ◽

Vol 179 ◽

pp. 01009

Author(s):

Sun Peng ◽

Wang Yanrong ◽

Zhang Xiaobo

Keyword(s):

Flow Field ◽

Centrifugal Compressor ◽

Deflection Angle ◽

Forced Response ◽

Significant Issue ◽

Centrifugal Compressors ◽

The Deflection Angle

Aeroelasticity has always been a significant issue of compressors. Impeller-diffuser interaction (IDI) produces periodic aerodynamic excitation which forces the blades to vibrate in centrifugal compressors, and eventually causes the damage of blades. Therefore, it is of great importance to investigate the IDI in centrifugal compressors and the effects on the vibration of blades. In this paper, it is discussed in detail that the deflection angle of the airflow in diffuser affects the IDI of the centrifugal compressor and the vibration of blades. The results show that if deflection angle is positive, the interaction of the diffuser on impeller and the vibration of main blades are decreased. However, on condition that the deflection angle is excessive, the interaction of the diffuser on the flow field of impeller will be intensified, and the vibration of the main blades will be stronger. Therefore, it is necessary to reasonably control the range of the deflection angle so that centrifugal compressors are able to work in a safer environment.

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A Detailed Loss Analysis Methodology for Centrifugal Compressors

10.1115/gt2021-59334 ◽

2021 ◽

Author(s):

Luying Zhang ◽

Loukia Kritioti ◽

Peng Wang ◽

Jiangnan Zhang ◽

Mehrdad Zangeneh

Keyword(s):

Flow Field ◽

Evaluation Method ◽

Deep Understanding ◽

Internal Flow ◽

Tip Clearance ◽

Optimized Design ◽

Centrifugal Compressors ◽

Design Modification ◽

Operational Conditions ◽

The Impact

Abstract A deep understanding of loss mechanisms inside a turbomachine is crucial for the design and analysis work. By quantifying the various losses generated from different flow mechanisms, a targeted optimization can be carried out on the blading design. In this paper an evaluation method for computational fluid dynamics simulations has been developed to quantify the loss generation based on entropy production in the flow field. A breakdown of losses caused by different mechanisms (such as skin friction, secondary flow, tip clearance vortex and shock waves) is achieved by separating the flow field into different zones. Each zone is defined by the flow physics rather than by geometrical locations or empirical correlations, which makes the method a more general approach and applicable to different machine types. The method has been applied to both subsonic and transonic centrifugal compressors, where internal flow is complex due to the Coriolis acceleration and the curvature effect. An evaluation of loss decomposition is obtained at various operational conditions. The impact of design modification is also assessed by applying the same analysis to an optimized design.

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Experimental and Computational Investigation of the NASA Low-Speed Centrifugal Compressor Flow Field

Journal of Turbomachinery ◽

10.1115/1.2929285 ◽

1993 ◽

Vol 115 (3) ◽

pp. 527-541 ◽

Cited By ~ 50

Author(s):

M. D. Hathaway ◽

R. M. Chriss ◽

J. R. Wood ◽

A. J. Strazisar

Keyword(s):

Velocity Field ◽

Flow Field ◽

Centrifugal Compressor ◽

Three Dimensional ◽

Surface Flow ◽

Computational Investigation ◽

Complex Flow ◽

Centrifugal Compressors ◽

Impeller Blade ◽

Low Speed

An experimental and computational investigation of the NASA Low-Speed Centrifugal Compressor (LSCC) flow field has been conducted using laser anemometry and Dawes’ three dimensional viscous code. The experimental configuration consists of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational analysis, and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the rotor as well as surface flow visualization along the impeller blade surfaces provide independent confirmation of the laser measurement technique. The results clearly document the development of the throughflow velocity wake, which is characteristic of unshrouded centrifugal compressors.

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Influence of volute design on flow field distortion and flow stability of turbocharger centrifugal compressors

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407017746281 ◽

2018 ◽

Vol 233 (3) ◽

pp. 484-494 ◽

Cited By ~ 2

Author(s):

Zhenzhong Sun ◽

Xinqian Zheng ◽

Zelin Linghu ◽

Tomoki Kawakubo ◽

Hideaki Tamaki ◽

...

Keyword(s):

Flow Field ◽

Experimental Methods ◽

Flow Stability ◽

Design Methods ◽

Radius Ratio ◽

Centrifugal Compressors ◽

Field Distortion ◽

Stable Flow

Volute-induced distortion of the flow field remarkably exacerbates the flow stability of turbocharger centrifugal compressors; hence, reducing the flow field distortion by modifying the volute design is of great significance. This study investigated the influence of volute design on the flow field distortion and flow stability of turbocharger centrifugal compressors. Volutes with different throat areas and different area-to-radius ratio ([Formula: see text]) distributions were designed, and their performances were analyzed via both numerical and experimental methods. The results show that the throat area and the [Formula: see text] distribution significantly influence the volute-induced pressure distortion. By modifying the volute design, the amplitude of the pressure distortion can be reduced from 8.82% to 3.22%, and the stable flow range can be extended from 49.8% to 58.7%. Additionally, to reduce flow field distortion, the throat area should be appropriate to guarantee a match between the volute and upstream components, and the [Formula: see text] distribution near the volute tongue should have a moderate slope. This study provides design methods for reducing flow field distortion by modifying the volute, and it also verifies the belief that smaller flow field distortion is beneficial to the flow stability of compressors.

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

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4053389 ◽

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.

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Numerical Study of the Combined Free-Forced Convection and Mass Transfer Flow Past a Vertical Porous Plate in a Porous Medium with Heat Generation and Thermal Diffusion

Nonlinear Analysis Modelling and Control ◽

10.15388/na.2006.11.4.14737 ◽

2006 ◽

Vol 11 (4) ◽

pp. 331-343 ◽

Cited By ~ 19

Author(s):

M. S. Alam ◽

M. M. Rahman ◽

M. A. Samad

Keyword(s):

Mass Transfer ◽

Flow Field ◽

Differential Equations ◽

Forced Convection ◽

Heat Generation ◽

Numerical Study ◽

Porous Plate ◽

Integration Scheme ◽

Suction Parameter ◽

Transfer Flow

The problem of combined free-forced convection and mass transfer flow over a vertical porous flat plate, in presence of heat generation and thermaldiffusion, is studied numerically. The non-linear partial differential equations and their boundary conditions, describing the problem under consideration, are transformed into a system of ordinary differential equations by using usual similarity transformations. This system is solved numerically by applying Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. The effects of suction parameter, heat generation parameter and Soret number are examined on the flow field of a hydrogen-air mixture as a non-chemical reacting fluid pair. The analysis of the obtained results showed that the flow field is significantly influenced by these parameters.

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