scholarly journals Effect of Vaneless Diffuser Shape on Performance of Centrifugal Compressor

2020 ◽  
Vol 10 (6) ◽  
pp. 1936
Author(s):  
Qian Zhang ◽  
Qiuhong Huo ◽  
Lei Zhang ◽  
Lei Song ◽  
Jianmeng Yang
Keyword(s):  
Numerical Simulation ◽  
Energy Loss ◽  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Parallel Wall

The influence of four different vaneless diffuser shapes on the performance of centrifugal compressors is numerically studied in this paper. One of the studied shapes was a parallel wall diffuser. Two others had the width reduced only from hub and shroud and the rest had the width reduced from hub and shroud divided evenly. Then the numerical simulation was employed and the overall compressor aerodynamic performance was studied. The detailed velocity and pressure distribution and energy loss within the centrifugal compressor with different diffuser geometries and different operating conditions were analyzed. The results revealed that shroud pinch significantly improved the overall compressor aerodynamic performance more than any other pinch types, and the best performance can be achieved by pinched diffusers under the design condition compared with pinched diffusers under the near surge condition or choking condition. The range of energy loss, namely the static entropy area in the compressor, become reduced with the above three pinches diffusers.

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.

Non-Axisymmetric Flows and Rotordynamic Forces in an Eccentric Shrouded Centrifugal Compressor—Part 2: Analysis

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Jieun Song ◽  
Seung Jin Song
Keyword(s):  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Axisymmetric Flow ◽  
Mass Conservation ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
New Model ◽  
Flow Coupling ◽  
Order Of Magnitude ◽  
Rotordynamic Forces

AbstractAn integrated analytical model to predict non-axisymmetric flow fields and rotordynamic forces in a shrouded centrifugal compressor has been newly developed and validated. The model is composed of coupled, conservation law-based, bulk-flow submodels, and the model takes into account the flow coupling among the blades, labyrinth seals, and shroud cavity. Thus, the model predicts the entire flow field in the shrouded compressor when given compressor geometry, operating conditions, and eccentricity. When compared against the experimental data from part 1, the new model accurately predicts the evolution of the pressure perturbations along the shroud and labyrinth seal cavities as well as the corresponding rotordynamic stiffness coefficients. For the test compressor, the cross-coupled stiffness rotordynamic excitation is positive; the contribution of the shroud is the highest; the contribution of the seals is less than but on the same order of magnitude as that of the shroud; and contribution of impeller blades is insignificant. The new model also enables insight into the physical mechanism for pressure perturbation development. The labyrinth seal pressure distribution becomes non-axisymmetric to satisfy mass conservation in the seal cavity, and this non-axisymmetry, in turn, serves as the influential boundary condition for the pressure distribution in the shroud cavity. Therefore, for accurate flow and rotordynamic force predictions, it is important to model the flow coupling among the components (e.g., impeller, shroud, labyrinth seal, etc.), which determines the non-axisymmetric boundary conditions for the components.

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 Centrifugal Compressor Testing Experience and Practice

1982 ◽  
Author(s):  
R. H. Meier ◽  
C. S. Rhea
Keyword(s):  
Natural Gas ◽  
Centrifugal Compressor ◽  
Performance Testing ◽  
Field Performance ◽  
Field Testing ◽  
Aerodynamic Performance ◽  
Reasonable Accuracy ◽  
Centrifugal Compressors ◽  
Factory Test ◽  
Different Types

Experience with factory and field performance testing of centrifugal compressors in natural gas service is presented. The ability of different types of factory test arrangements to closely predict future field performance is compared. Instrumentation requirements for achievement of reasonable accuracy in field testing are defined and discussed. Major aspects of mechanical and aerodynamic performance testing are addressed.

Cyclostationary Approach for Instabilities Detection and Condition Monitoring of Centrifugal Compressor

2020 ◽  
Author(s):  
Mateusz Stajuda ◽  
David Garcia Cava ◽  
Grzegorz Liśkiewicz
Keyword(s):  
Condition Monitoring ◽  
Centrifugal Compressor ◽  
Operating Conditions ◽  
Periodic Signal ◽  
Centrifugal Compressors ◽  
First Order ◽  
Standard Signal ◽  
Processing Techniques ◽  
Signal Processing Techniques ◽  
Insight Into

Abstract This study intends to explore the capabilities of the cyclostationary approach for instabilities detection and operating conditions monitoring of centrifugal compressors. Cyclostationary approach offers powerful signal analysis methods, applicable to different processes. It was proven useful for analysis of vibration, acoustic and pressure data for systems exhibiting periodicity. Cyclostationarity has been used for extracting subtle changes between cycles of the periodic signal which could be used for condition monitoring. Recent research focuses on employing this method for fault indication. Cyclostationary approach has not been extensively used in the field of turbomachinery, except for a few cases when it was proven to give a better insight into flow structure than standard signal processing techniques and allow for the detection of instabilities in flow systems. Thus, the cyclostationary approach may be suitable for instabilities detection and condition monitoring in centrifugal compressors. This paper exploits various techniques employing a cyclostationary framework for instabilities detection and operating conditions monitoring with the use of pressure signals from the low-speed centrifugal compressor. The most prospective cyclostationarity-based indicators are applied for the detection of instabilities. Due to a lack of second-order cyclostationarity, the study confines to the analysis of first-order cyclostationarity strongly exhibited in the compressor pressure signal. First-order cyclostationarity analysis provides an indication of instabilities and working conditions differentiation, but due to time-domain sampling, it is not fully robust and reliable. The highest potential is perceived in the cyclostationary approach use to extract changes between cycles. Different measures of change in variability could serve as a valuable indicator of instabilities.

Data-Driven Predesign Tool for Small-Scale Centrifugal Compressor in Refrigeration

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mounier Violette ◽  
Picard Cyril ◽  
Schiffmann Jürg
Keyword(s):  
Centrifugal Compressor ◽  
High Efficiency ◽  
Design Procedure ◽  
Integrated System ◽  
Operating Conditions ◽  
Data Driven ◽  
Small Scale ◽  
Centrifugal Compressors ◽  
Starting Point ◽  
Isentropic Efficiency

Domestic scale heat pumps and air conditioners are mainly driven by volumetric compressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. The design procedure of centrifugal compressors starts with predesign tools based on the Cordier line. However, the optimality of the obtained predesign, which is the starting point of a complex and iterative process, is not guaranteed, especially for small-scale compressors operating with refrigerants. This paper proposes a data-driven predesign tool tailored for small-scale centrifugal compressors used in refrigeration applications. The predesign model is generated using an experimentally validated one-dimensional (1D) code which evaluates the compressor performance as a function of its detailed geometry and operating conditions. Using a symbolic regression tool, a reduced order model that predicts the performance of a given compressor geometry has been built. The proposed predesign model offers an alternative to the existing tools by providing a higher level of detail and flexibility. Particularly, the model includes the effect of the pressure ratio, the blade height ratio, and the shroud to tip radius ratio. The analysis of the centrifugal compressor losses allows identifying the underlying phenomena that shape the new isentropic efficiency contours. Compared to the validated 1D code, the new predesign model yields deviations below 4% on the isentropic efficiency, while running 1500 times faster. The new predesign model is, therefore, of significant interest when the compressor is part of an integrated system design process.

Component Matching of Centrifugal Compressors for Turbocharger Application

2017 ◽  
Author(s):  
Hua Chen
Keyword(s):  
Centrifugal Compressor ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Flow Area ◽  
Matching Process ◽  
Compressor Design ◽  
Component Matching ◽  
Key Aspects ◽  
Stage Efficiency

Matching of various components (impeller exducer to impeller inducer, and vaneless diffuser and volute to the impeller) in a centrifugal compressor is critical for stage performance, but this is often neglected during compressor design and selection. This paper studies the importance of flow area matching for stage efficiency and how this matching process can be performed rapidly following a few simple principles. Methods for achieving optimum efficiency under different compressor operating conditions and size constraint are proposed and compared with experimental results. The purpose of this work is to draw attention to the key aspects of the matching, and provide easy-to-use design guidelines for engineers.

Experimental and Numerical Analysis of the Secondary Flow Across the Interphase Balance Drum of a High Pressure Back-to-Back Centrifugal Compressor

2017 ◽  
Author(s):  
Carmine Carmicino ◽  
Francesco Maiuolo ◽  
Emanuele Rizzo
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Numerical Analysis ◽  
Pressure Distribution ◽  
Centrifugal Compressor ◽  
Operating Conditions ◽  
Local Pressure ◽  
Flow Angle ◽  
One Dimensional ◽  
Honeycomb Seal

With the major aim of gathering information on the machine lateral stability in high pressure-high density conditions, and of assessing the prediction capabilities of the in-house design tools and overall process, a back-to-back centrifugal compressor has been instrumented and tested in several operating conditions. The present paper focuses on the secondary flows across the interphase balance drum of the back-to-back compressor, where the sealing is accomplished with a honeycomb seal. The compressor interphase section has been instrumented with dedicated special probes for the clearance measurement associated to pressure and flow angle probes in order to characterize pressure distributions and swirl variations depending on the specific operating range. The experimental data acquired over the machine operation have been compared with a three-dimensional steady-state numerical analysis results obtained from the simulation, carried out with a Reynolds averaged Navier-Stokes (RANS) approach, of the flowfield in the complex interphase secondary system composed by the impeller cavities and the honeycomb seal. This paper addresses the comparison between numerical results and experimental data, which allowed the matching of models with experiments in terms of pressure distribution and the complex flowfield. Finally, all the data have been used to validate an in-house one-dimensional flow network solver for pressure distribution and leakage flow calculations along cavities and seals. Results have shown a general good agreement between measured data and calculation output. In particular, computational fluid dynamic analysis provided detailed pressure and velocity distributions that allowed gaining insight in the physics of such a complex region. The one-dimensional model has been demonstrated to be a fast and reliable tool to well predict local pressure variations inside cavities and seals and, consequently, the residual axial thrust.

The Numerical Simulation of Full Flow Field of Roto-Jet Pump and Analysis of Energy Losses

2012 ◽  
Vol 562-564 ◽  
pp. 1369-1372 ◽  
Author(s):  
Chun Lin Wang ◽  
Chun Lei Zhao ◽  
Tian Fang Zhang ◽  
Dong Liu
Keyword(s):  
Numerical Simulation ◽  
Energy Loss ◽  
Operating Conditions ◽  
Energy Losses ◽  
Steady Flows ◽  
Jet Pump ◽  
Working Principle ◽  
The Difference ◽  
Set Up ◽  
Difference Effect

The structure and working principle are introduced in the paper. Based on the physical model of key parts to roto-jet pump which is set up in Gambit, the 3-D steady flows numerical simulation has been implemented by means of Fluent under design operating conditions. This method could avoid the error in simulating single part of the pump. The result shows the interflow distribution of the pump, the difference effect is very well after installing short blades on impeller. the shape of collecting pipe has little impact on the pressure within rotor cavity and the vertex band is apt to form in the corner of the collecting pipe inlet. By analyzing the energy losses between two different installed types of roto-jet pump. The result shows that the energy loss of rotor cavity in right-closed impeller pump is more than in the left-open impeller pump, but the effect of impeller pressurization in left-open impeller pump is not well, the energy loss caused by collecting pipe is almost the same in the two different pumps. The analyzing results can provide some proposals for structure reforming, performance and efficiency improving.

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.

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