Performance Analysis of a Centrifugal Compressor Based on Circumferential Flow Distortion Induced by Volute

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Mengying Shu ◽  
Mingyang Yang ◽  
Kangyao Deng ◽  
Xinqian Zheng ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Simulation Method ◽  
Tip Clearance ◽  
Flow Distortion ◽  
Aerodynamic Stability ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Local Gradient

A volute is one of the key components in a centrifugal compressor. The aerodynamic stability of the compressor deteriorates remarkably when a volute is employed. This paper investigates the influence of volute-induced circumferential flow distortion on aerodynamic stability of a centrifugal compressor via experimentally validated three-dimensional (3D) numerical simulation method. First, the compressor performance is analyzed based on a newly developed stability parameter. The impeller is confirmed to be the main contributor to the instability of the investigated compressor. Next, the influence of volute on impeller performance is studied by circumferentially distorted boundary conditions at the impeller exit which are extracted from flow field at the volute inlet. Results show that the performance of an impeller passage is determined by not only the back pressure but also the local gradient of pressure distribution in the circumferential direction. Moreover, these passages confronted with pressure reduction in the rotational direction are most unstable, while those confronted with pressure rise have better performance. Consequently, the circumferentially distorted distribution at impeller exit results in a loop of passage performance encapsulating the performance of uniform case. The size of the loop is enhanced by the distortion amplitude. Moreover, the influence of volute-induced distortion on the impeller performance is concluded into two main reasons: the imbalance of the force on flow and the imbalance of tip clearance flow taken by passages. The force imbalance influences the accumulation of secondary flow, while the imbalance of the tip clearance flow results in discrepancies of the low momentum flow in passages.

A Comparison Between the Design Point and Near-Stall Performance of an Axial Compressor

1990 ◽  
Vol 112 (1) ◽  
pp. 109-115 ◽  
Author(s):  
N. M. McDougall
Keyword(s):  
Rotor Blade ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Design Point ◽  
Blade Row ◽  
Clearance Flow ◽  
Stator Blade

Detailed measurements have been made within an axial compressor operating both at design point and near stall. Rotor tip clearance was found to control the performance of the machine by influencing the flow within the rotor blade passages. This was not found to be the case in the stator blade row, where hub clearance was introduced beneath the blade tips. Although the passage flow was observed to be altered dramatically, no significant changes were apparent in the overall pressure rise or stall point. Small tip clearances in the rotor blade row resulted in the formation of corner separations at the hub, where the blade loading was highest. More representative clearances resulted in blockage at the tip due to the increased tip clearance flow. The effects that have been observed emphasize both the three-dimensional nature of the flow within compressor blade passages, and the importance of the flow in the endwall regions in determining the overall compressor performance.

A Comparison Between the Design Point and Near Stall Performance of an Axial Compressor

1989 ◽  
Author(s):  
N. M. McDougall
Keyword(s):  
Rotor Blade ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Design Point ◽  
Blade Row ◽  
Clearance Flow ◽  
Stator Blade

Detailed measurements have been made within an axial compressor operating both at design point and near stall. Rotor tip clearance was found to control the performance of the machine by influencing the flow within the rotor blade passages. This was not found to be the case in the stator blade row, where hub clearance was introduced beneath the blade tips. Although the passage flow was observed to be altered dramatically, no significant changes were apparent in the overall pressure rise or stall point. Small tip clearances in the rotor blade row resulted in the formation of corner separations at the hub, where the blade loading was highest. More representative clearances resulted in blockage at the tip due to the increased tip clearance flow. The effects which have been observed emphasize both the three dimensional nature of the flow within compressor blade passages, and the importance of the flow in the endwall regions in determining the overall compressor performance.

Effect of Upstream Unsteady Flow Conditions on Rotor Tip Leakage Flow

2002 ◽  
Author(s):  
Borislav T. Sirakov ◽  
Choon S. Tan
Keyword(s):  
Three Dimensional ◽  
Pressure Rise ◽  
Tip Clearance ◽  
High Loading ◽  
Causal Mechanism ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
The Impact

A study has been conducted, using unsteady three-dimensional Reynolds-averaged Navier-Stokes simulations to determine the impact on rotor performance of the interaction between the stator wakes and rotor tip clearance flow. The key effects of the interaction are: (1) a decrease in loss and blockage associated with tip clearance flow; (2) an increase in passage static pressure rise. Performance benefit is seen in the whole operability range of interest, from near design to high loading. The benefit is modest near design and increases with loading. Significant beneficial changes occur when the phenomenon of tip clearance flow double-leakage is present. Double-leakage occurs when the tip clearance flow passes through the tip gap of the neighboring blade. Double-leakage typically takes place at high loading but can be present at design condition, as well. A benefit due to unsteady interaction is also observed in the operability range of the rotor. A new generic causal mechanism is proposed to explain the observed changes in performance. It identifies the interaction between the tip clearance flow and the pressure pulses, induced on the rotor blade pressure surface by the upstream wakes, as the cause for the observed effects. The direct effect of the interaction is a decrease in the time-average double-leakage flow through the tip clearance gap so that the stream-wise defect of the exiting tip flow is lower with respect to the main flow. A lower defect leads to a decrease in loss and blockage generation and hence an enhanced performance compared to that in the steady situation. The performance benefits increase monotonically with loading and scale linearly with upstream wake velocity defect.

Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 127-142
Author(s):  
Wei Zhu ◽  
Songtao Wang ◽  
Longxin Zhang ◽  
Jun Ding ◽  
Zhongqi Wang
Keyword(s):  
Numerical Simulations ◽  
Dynamic Balance ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Phenomena

This study aimed to enhance the understanding of flow phenomena in low-reaction aspirated compressors. Three-dimensional, multi-passage steady and unsteady numerical simulations are performed to investigate the performance sensitivity to tip clearance variation on the first-stage rotor of a multistage low-reaction aspirated compressor. Three kinds of tip clearance sizes including 1.0τ, 2.0τ and 3.0τ are modeled, in which 1.0τ corresponds to the designed tip clearance size of 0.2 mm. The steady numerical simulations show that the overall performance of the rotor moves toward lower mass flow rate when the tip clearance size is increased. Moreover, energy losses, efficiency reduction and stall margin decrease are also observed with increasing tip clearance size. This can be mostly attributed to the damaging impact of intense tip clearance flow. For unsteady simulation, the result shows periodical oscillation of the tip leakage vortex and a “two-passage periodic structure” in the tip region at the near-stall point. The occurrence of the periodical oscillation is due to the severe interaction between the tip clearance flow and the shock wave. However, the rotor operating state is still stable at this working point because a dynamic balance is established between the tip clearance flow and incoming flow.

Physics of Tip Clearance Flow in Turbomachinery (Keynote Paper)

2002 ◽  
Author(s):  
Masahiro Inoue ◽  
Masato Furukawa
Keyword(s):  
Flow Field ◽  
Physical Interpretation ◽  
Vortex Core ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

In a recent advanced aerodynamic design of turbomachinery, the physical interpretation of three-dimensional flow field obtained by a numerical simulation is important for iterative modifications of the blade or impeller geometry. This paper describes an approach to the physical interpretation of the tip clearance flow in turbomachinery. First, typical flow phenomena of the tip clearance flow are outlined for axial and radial compressors, pumps and turbines to help comprehensive understanding of the tip clearance flow. Then, a vortex-core identification method which enables to extract the vortical structure from the complicated flow field is introduced, since elucidation of the vortical structure is essential to the physical interpretation of the tip clearance flow. By use of the vortex-core identification, some interesting phenomena of the tip clearance flows are interpreted, especially focussing on axial flow compressors.

Mesh-Generation Parameters Influence on Centrifugal Compressor Simulation for Design Optimization

2004 ◽  
Author(s):  
Guillaume Dufour ◽  
Xavier Carbonneau ◽  
Pierre Arbez ◽  
Jean-Bernard Cazalbou ◽  
Patrick Chassaing
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Numerical Accuracy ◽  
Specific Flow ◽  
Design Decisions ◽  
Tip Clearance Flow ◽  
Experiment Method ◽  
Clearance Flow ◽  
Flow Quantity

As advocated by Denton [1], three-dimensional CFD calculations are more and more used in the process of designing centrifugal compressors. Therefore, numerical accuracy is an issue if valuable design decisions are to be based on CFD results. This paper aims at correlating mesh-parameters and calculated flow quantities. The design-of-experiment method (DOE) is used to identify which mesh-parameters influence any given flow quantity. The emphasis is put on global performances (mass-flow rate, pressure-ratio and efficiency), and on local features (friction co-efficients and local velocity-profiles). The outcome of the study is the connection between mesh-parameters and specific flow-properties. This can be further used to derive numerical bench-marks, such as reported by Dufour et al. [2] for the tip-clearance flow.

Effect of Unsteady Stator Wake—Rotor Double-Leakage Tip Clearance Flow Interaction on Time-Average Compressor Performance

2003 ◽  
Vol 125 (3) ◽  
pp. 465-474 ◽  
Author(s):  
Borislav Todorov Sirakov ◽  
Choon-Sooi Tan
Keyword(s):  
Pressure Rise ◽  
Tip Clearance ◽  
High Loading ◽  
Causal Mechanism ◽  
Tip Clearance Flow ◽  
Reduced Frequency ◽  
Clearance Flow ◽  
Compressor Performance ◽  
Time Average ◽  
The Impact

A study has been conducted, using unsteady three-dimensional Reynolds-averaged Navier-Stokes simulations to determine the impact on rotor performance of the interaction between upstream (steady defect and time-varying defect) stator wakes and rotor tip clearance flow. The key effects of the interaction between steady stator wakes and rotor tip clearance flow are: 1) a decrease in loss and blockage associated with tip clearance flow; 2) an increase in passage static pressure rise. Performance benefit is seen in the operability range from near design to high loading. The benefit is modest near design and increases with loading. Significant beneficial changes due to the stator-rotor interaction occur when the phenomenon of tip clearance flow double-leakage is present. Double-leakage occurs when the tip clearance flow passes through the tip gap of the adjacent blade. It is detrimental for compressor performance. The effect of strong stator-rotor interaction is to suppress double-leakage on a time-average basis. Double-leakage typically takes place at high loading but can be present at design condition as well, for modern highly loaded compressor. A benefit due to unsteady interaction is also observed in the operability range of the rotor. A new generic causal mechanism is proposed to explain the observed changes in performance. It identifies the interaction between the tip clearance flow and the pressure pulses, induced on the rotor blade pressure surface by the upstream wakes, as the cause for the observed effects. The direct effect of the interaction is a decrease in the time-average double-leakage flow through the tip clearance gap so that the stream-wise defect of the exiting tip flow is lower with respect to the main flow. A lower defect leads to a decrease in loss and blockage generation and hence an enhanced performance compared to that in the steady situation. The performance benefits increase monotonically with loading and scale linearly with upstream wake velocity defect. With oscillating defect stator wakes, rotor performance shows dependence on oscillation frequency. Changes in the tip region occur at a particular reduced frequency leading to (1) decrease in blockage, and (2) increase in passage loss. The changes in rotor performance at a particular reduced frequency are hypothesized to be associated with the inherent unsteadiness of the tip clearance vortex and its resonance behavior excited by the oscillating wakes.

Numerical Study of the Tip Clearance Flow Development in a Propulsion Pump Stage

1996 ◽  
Author(s):  
Yu-Tai Lee ◽  
Chunill Hah ◽  
James Loellbach
Keyword(s):  
Vortex Structure ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
High Reynolds

This paper summarizes a numerical investigation of the fundamental structure of the rotor tip-clearance vortex and its interaction with a passage trailing-edge vortex in a single-stage stator-rotor pump. The flow field of a highly-loaded rotor measured in a high Reynolds number pump facility (HIREP) is used for comparison. The numerical solution was obtained by solving the three-dimensional Reynolds averaged Navier-Stokes equations. The calculated results are visualized in order to understand the details of the tip-vortex structure. The study shows that the tip geometry should be accurately represented to predict the tip-vortex structure correctly.

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