Numerical investigation of deep surge in a centrifugal compressor with vaned diffuser and large plenum

2019 ◽  
Vol 234 (2) ◽  
pp. 143-155
Author(s):  
Zhao Yang ◽  
Xi Guang ◽  
Wang Zhiheng ◽  
Zhang Pengfei
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Deep Understanding ◽  
Internal Flow ◽  
Impeller Blade ◽  
Vaned Diffuser ◽  
Blade Loading ◽  
Transient Feature ◽  
Different Characteristics

As the flow rate decreases from stable point to surge point, the complex unsteady flow phenomenon of surge occurs in a centrifugal compressor, which has a significant influence on vast aspects of a compressor. To advance deep understanding of the feature of the deep surge phenomenon, the RANS/URANS numerical simulation is conducted on a centrifugal compressor with a large plenum to analyze the detailed internal flow field in the compressor together with the macroscopic characteristics of the deep surge cycle. The anticlockwise limit cycle obtained from the simulation is firstly analyzed to show the transient characteristics of the stage. Then the variation of blade torque and axial force is presented to show the transient feature in surge cycle together with the proposed prediction of blade torque versus mass flow rate. Meanwhile, there exist different characteristics of the pressure fluctuation along the streamwise direction of the impeller blade, especially the large variation of blade loading near the trailing edge. And the fluctuation of flow field can respectively suppress or promote the hub-corner separation at the process of acceleration or deceleration region, affecting the development of diffuser stall in the surge cycle. The detailed analysis can be helpful to develop the surge model of lumped parameters and determine the effect of surge on impeller blades or downstream components.

Improving a Vaned Diffuser for a Given Centrifugal Impeller by 3D Inverse Design

2002 ◽  
Author(s):  
Mehrdad Zangeneh ◽  
Damian Vogt ◽  
Christian Roduner
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Centrifugal Compressor ◽  
Inverse Method ◽  
Flow Distribution ◽  
Inverse Design ◽  
Centrifugal Impeller ◽  
Design Code ◽  
Vaned Diffuser ◽  
Blade Loading

In this paper the application of 3D inverse design code TURBOdesign−1 to the design of the vane geometry of a centrifugal compressor vaned diffuser is presented. For this study the new diffuser is designed to match the flow leaving the conventional impeller, which is highly non-uniform. The inverse method designs the blade geometry for a given specification of thickness and blade loading distribution. The paper describes the choice of loading distribution used in the design as well as the influence of the diffuser inlet flow distribution on the vane geometry and flow field. The flow field in the new diffuser is analysed by a 3D viscous flow code and the result is compared to that of the conventional diffuser. Finally the results of testing the stage performance of the new diffuser is compared with that of the conventional stage.

scholarly journals Experimental Flow Field Investigation in a Centrifugal Compressor Vaned Diffuser

1995 ◽  
Author(s):  
Ali Pinarbasi ◽  
Mark W. Johnson
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Field Investigation ◽  
Vaneless Diffuser ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Impeller Blade ◽  
Vaned Diffuser ◽  
Flow Angle

The purpose of this study was to improve the understanding of the flow physics in a centrifugal compressor vaned diffuser. A low speed compressor with a 19 bladed backswept impeller and diffuser with 16 wedge vanes was used. The measurements were made at three inter-vane positions and are presented as mean velocity, turbulent kinetic energy and flow angle distributions on eight diffuser cross sectional planes. The impeller blade wakes mix out rapidly within the vaneless space and more rapidly than in an equivalent vaneless diffuser. Although the flow is highly non uniform in velocity at the impeller exit, there is no evidence in the results of any separation from the diffuser vanes. The results do however suggest that the use of twisted vanes within the diffuser would be beneficial in reducing losses.

Influences of Tip Leakage Flows Discharged From Main and Splitter Blades on Flow Field in Transonic Centrifugal Compressor Stage

2018 ◽  
Author(s):  
Masanao Kaneko ◽  
Hoshio Tsujita
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Blade Loading ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Transonic Centrifugal Compressor ◽  
Tip Leakage Flows

A transonic centrifugal compressor impeller is generally composed of the main and the splitter blades which are different in chord length. As a result, the tip leakage flows from the main and the splitter blades interact with each other and then complicate the flow field in the compressor. In this study, in order to clarify the individual influences of these leakage flows on the flow field in the transonic centrifugal compressor stage at near-choke to near-stall condition, the flows in the compressor at four conditions prescribed by the presence and the absence of the tip clearances were analyzed numerically. The computed results clarified the following noticeable phenomena. The tip clearance of the main blade induces the tip leakage vortex from the leading edge of the main blade. This vortex decreases the blade loading of the main blade to the negative value by the increase of the flow acceleration along the suction surface of the splitter blade, and consequently induces the tip leakage vortex caused by the negative blade loading of the main blade at any operating points. These phenomena decline the impeller efficiency. On the other hand, the tip clearance of the splitter blade decreases the afore mentioned acceleration by the formation of the tip leakage vortex from the leading edge of the splitter blade and the decrease of the incidence angle for the splitter blade caused by the suction of the flow into the tip clearance. These phenomena reduce the loss generated by the negative blade loading of the main blade and consequently reduce the decline of the impeller efficiency. Moreover, the tip clearances enlarge the flow separation around the diffuser inlet and then decline the diffuser performance independently of the operating points.

Non-Axisymmetric Flow Structure in Vaneless Diffuser of Centrifugal Compressor for Turbochargers

2012 ◽  
Author(s):  
Chuanjie Lan ◽  
Xinqian Zheng ◽  
Hideaki Tamaki
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Vaneless Diffuser ◽  
Asymmetric Flow ◽  
Oil Flow ◽  
Flow Visualizations

Turbocharger technology is widely used in internal combustion engines. With the downsizing of internal combustion engines and the introduction of strict emission regulations, there is urgent demand for turbochargers featuring centrifugal compressors with a wide flow range. The flow in a centrifugal compressor of a turbocharger is non-axisymmetric due to the inherent asymmetry of the discharge volute. The asymmetric flow field inside the diffuser has great influence on the performance of centrifugal compressor. In order to develop a flow control method that facilitates a wider flow range of turbocharger compressors, further understanding of the asymmetric flow structure is very important. The main subject of this study is to reveal the asymmetrical characteristics of the flow field in the vaneless diffuser of a centrifugal compressor followed by a volute. Oil flow visualizations and numerical simulations were used. The results of the numerical simulations are consistent with that of the oil flow visualizations near choke and at designed flow rate. The results show that a “dual-zone mode” asymmetric flow structure exists near the shroud of the vaneless diffuser at near choke condition. A bifurcation point at the volute tongue that divides the flow and creates two distinct flow patterns was found. The asymmetry of the flow structure near the hub was much less significant than that near the shroud. At the design flow rate, asymmetric flow patterns are found neither near shroud nor near hub. At near surge condition, the pattern of the oil flow traces near the shroud is very different from those near choke.

Investigation of Internal Flow and Characteristic Instability of a Mixed Flow Pump

2009 ◽  
Author(s):  
Masahiro Miyabe ◽  
Akinori Furukawa ◽  
Hideaki Maeda ◽  
Isamu Umeki
Keyword(s):  
Flow Rate ◽  
Internal Flow ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Suction Surface ◽  
Mixed Flow ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Pressure Surface ◽  
Flow Pump

The relationship between pump characteristic instabilities and internal flow was investigated in a mixed flow pump with specific speed of 700 (min−1 m3/min, m) or 1.72 (non-dimensional) by using a commercial CFD code and a dynamic PIV (DPIV) measurement. This pump has two positive slopes of a head-flow characteristic at the flow rates of about 60%Qopt and 82%Qopt. In the authors’ previous study, it was clarified that the characteristic instability at 82%Qopt is caused by the diffuser rotating stall (DRS) and the backflow near the hub of the vaned diffuser plays an important role on the onset of the diffuser rotating stall. In the present paper, the investigation is focused on the instability at about 60% Qopt. Based on both of experimental and numerical results, it was clarified that the characteristic instability at 60%Qopt is caused by the backflow at the inlet of the impeller tip and the leakage flow from the impeller pressure surface to the suction surface plays an important role on the onset of the backflow. The behaviors of backflow at the impeller inlet were visualized by the DPIV measurements and CFD simulation. Moreover, internal flow was investigated in detail and the occurrence of characteristic instability is assumed as follows: At the partial flow rate, the flow angle at the inlet of the impeller tip decreases and the flow hits the impeller pressure surface. Then, the blade loading at the inlet of impeller tip is increased and the recirculation at the leading edge and the leakage flow rate from pressure surface to suction surface increases. The leakage flow causes to generate vortices at the inlet of the suction surface of the impeller. As the flow rate is further decreased, the vortices develop to backflow with swirl. The leakage flow has peripheral component of absolute velocity and the swirling energy is continuously supplied by the backflow. Therefore, even the passage flow at the inlet of the impeller has been getting pre-swirling. The theoretical head, the Euler head is decreased due to the pre-swirling. Moreover, based on the CFD results, the pre-swirling and unsteady vortices near the suction surface of the impeller causes pump characteristic instability. When the flow rate is decreased further more, total head rises because the flow pattern in the impeller changes to centrifugal type due to the backflow from the vaned diffuser at the hub region.

Impeller Rotating Stall as a Trigger for the Transition From Mild to Deep Surge in a Subsonic Centrifugal Compressor

1993 ◽  
Author(s):  
Beat Ribi ◽  
Georg Gyarmathy
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Critical Value ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
Compressor Map ◽  
Operating Points

The present paper concerns the transition from mild to deep surge in a single stage centrifugal compressor using a vaned diffuser. Time-resolved measurements of the mass flow rate and the static pressures at various locations of the compressor were analyzed for different diffuser geometries and different operating points in the compressor map. When the throttle valve was gradually closed at an impeller tip Mach number (Mu) above 0.4, the compressor showed first mild and then deep surge whereas at Mu=0.4 rotating stall was the dominant instability. This single-cell rotating stall was identified to be caused by the impeller. During mild surge at higher Mach numbers the instantaneous flow and pressure traces showed that the overall flow at the stage inlet intermittently dropped below the critical value associated with the occurence of impeller rotating stall. Rotating stall appeared for a while but vanished as soon as the flow increased again. With further throttling, however, a threshold was reached at which rotating stall triggered deep surge. The results show that triggering only occurred if the flow deficiency causing rotating stall persisted long enough to permit the stall cell to make at least one or two revolutions.

Off-Design Flow Measurements in a Centrifugal Compressor Vaneless Diffuser

1995 ◽  
Vol 117 (4) ◽  
pp. 602-608 ◽  
Author(s):  
A. Pinarbasi ◽  
M. W. Johnson
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Secondary Flows ◽  
Design Flow ◽  
Vaneless Diffuser ◽  
Flow Measurements ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Flow Rates ◽  
Study Results

Detailed measurements have been taken of the three-dimensional velocity field within the vaneless diffuser of a backswept low speed centrifugal compressor using hot-wire anemometry. A 16 percent below and an 11 percent above design flow rate were used in the present study. Results at both flow rates show how the blade wake mixes out more rapidly than the passage wake. Strong secondary flows inherited from the impeller at the higher flow rate delay the mixing out of the circumferential velocity variations, but at both flow rates these circumferential variations are negligible at the last measurement station. The measured tangential/radial flow angle is used to recommend optimum values for the vaneless space and vane angle for design of a vaned diffuser.

Surge Characteristics and Range Extension With Steam Injection in a Centrifugal Compressor With Vaned Diffuser

2013 ◽  
Author(s):  
Chuang Gao ◽  
Weiguang Huang ◽  
Weijia Yao ◽  
Jicheng Duan
Keyword(s):  
Stability Analysis ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Flow Behavior ◽  
Steam Injection ◽  
Experimental Results ◽  
Saturated Steam ◽  
Vaned Diffuser ◽  
Surge Margin ◽  
Static Performance

This paper describes the experimental results of both steady and unsteady flow behavior and surge extension with steam injection in a centrifugal compressor with vaned diffuser and downstream collector. Specifically, the stage stability analysis and effects of steam injection on surge margin are reported based on experimental results in detail. As the first step, a meanline analysis based on empirical correlations is utilized to find the possible stability dominated component. Then surge extension methods are put forward on the investigated compressor to enhance field operability. To validate the meanline analysis, the static performance of both stage and components from the experiments were analyzed and the root cause of system surge was again given based on the classic stability theory. The experimental results not only prove the validity of the former stability analysis but also extend the surge margin at least 9.0% with only 0.3% saturated steam of designed mass flow rate. During the experiments, it was also found that the surge margin improvement was not in proportion to the flow injected. In certain cases, the injected steam at large flow rate can even trigger system surge earlier. To the authors’ known, this is the first report on surge extension with steam injection in open literature.

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