Effects of blade rotation on axial turbine tip leakage vortex breakdown and loss

2016 ◽  
Vol 231 (9) ◽  
pp. 1634-1649
Author(s):  
Jie Gao ◽  
Qun Zheng ◽  
Yunning Liu ◽  
Ping Dong
Keyword(s):  
Vortex Breakdown ◽  
Great Influence ◽  
Main Flow ◽  
Leakage Flow ◽  
Centrifugal Forces ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Blade Rotation ◽  
Coriolis And Centrifugal Forces ◽  
Blade Tip

The tip leakage vortex breakdown occurs under a few conditions in modern turbines, which leads to extra vortex breakdown losses, but the mechanisms of vortex breakdown and its influencing factors still remain unclear. This paper is a continuation of the previous effort and focuses on the effect of blade rotation on the leakage vortex dynamics in an unshrouded turbine. The analyses on leakage vortex breakdown characteristics are first shown, and then the isolating effects of relative casing motion and Coriolis and centrifugal forces on leakage vortex breakdown and loss are investigated. Based on these, the overall effects of blade rotation on leakage vortex breakdown characteristics are examined. Results indicate that the scraping effects of the casing endwall have a great influence on the blade tip leakage vortex breakdown and loss. However, the effect of Coriolis and centrifugal forces is relatively small. Although the mismatch of both velocity components of the leakage flow and the main flow becomes slightly small with the casing motion, the blade tip mixing loss per unit leakage flow increases due to the fact that the leakage vortex breaks down in advance.

Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

2008 ◽  
Author(s):  
Dianliang Yang ◽  
Xiaobing Yu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Relative Motion ◽  
Turbulence Models ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blade Height ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Rotation ◽  
Blade Tip

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.

Numerical Investigation Into the Mechanism of Tip Flow Unsteadiness in a Transonic Compressor

2017 ◽  
Author(s):  
Guangyao An ◽  
Yanhui Wu ◽  
Jinhua Lang ◽  
Zhiyang Chen ◽  
Bo Wang ◽  
...  
Keyword(s):  
Vortex Breakdown ◽  
Pressure Oscillation ◽  
Operating Point ◽  
Recirculation Region ◽  
Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Flow Unsteadiness ◽  
Transonic Compressor ◽  
Evolution And Development

It is well known that tip flow unsteadiness has profound effects on both performance and stability of axial compressors. A number of numerical simulations have been performed in transonic compressors to uncover the nature of tip flow unsteadiness. From this research, tip flow unsteadiness can be attributed to many factors, such as the movement of the primary and secondary leakage flow, the interaction between shock and vortex, and the tip leakage vortex breakdown. However, no final conclusion has yet been reached on this matter. The current investigation is carried out to explore the origin of tip flow unsteadiness from the perspective of the evolution and development of tip leakage vortex breakdown. In this paper, unsteady RANS simulations have been performed to investigate the fluid dynamic processes in a tip-critical transonic compressor, NASA Rotor 35. A vortex core visualization method based on an eigenvector method is introduced as an important tool to identify the vortex arising from tip leakage flow. As the flow rate varies, three critical operating points with distinctive features of flow unsteadiness are observed. At the first critical operating point, bubble-type breakdown occurs, and gives rise to a weak unsteadiness with high frequency in the rotor passage due to the oscillation of the recirculation region induced by the tip leakage vortex breakdown. At the second critical operating point, the vortex breakdown has transformed from bubble-type to spiral-type, which leads to the frequency of the pressure oscillation reduced almost by half and the amplitude increased significantly. At the third critical operating point, a new vortex that is perpendicular to the pressure surface comes into being in the tip region, which leads to a prominent pressure oscillation of the tip flow and another jump in amplitude. As a result, the evolution and development of tip leakage vortex breakdown are closely related to the tip flow unsteadiness of the investigated rotor.

Numerical analysis of the groove effect on the tip leakage vortex cavitating flow

2019 ◽  
Vol 234 (6) ◽  
pp. 836-847
Author(s):  
Zhaodan Fei ◽  
Rui Zhang ◽  
Hui Xu ◽  
Tong Mu
Keyword(s):  
Flow Pattern ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Curvature Effects ◽  
The Mean

In this paper, the groove effect on the tip leakage vortex cavitating flow characteristics of a simplified NACA0009 hydrofoil with tip gap is studied. Considering local rotation characteristics and curvature effects of the tip leakage vortex flow, the rotation-curvature corrected shear-stress-transport turbulence model is applied to simulate the time-averaged turbulent flow. The Zwart–Gerber–Belamri cavitation model is used to simulate the cavitating flow. The results show that the groove could affect the tip leakage vortex cavitating flow. The groove enhances the interaction between the tip leakage flow and main flow, and then it affects the cavitation of the tip leakage vortex. Compared with the non-groove case, for groove cases of αgre ≤75°, the tip leakage vortex cavitating flow is suppressed, the flow pattern in the gap is improved, and the mean leakage velocity Vlk < 0.8. The region of high leakage velocity is eliminated and the distribution of the pressure is more uniform. The tip leakage vortex cavitation area is reduced, and the maximum decrease is 72.90%. While for groove cases of αgre≥90°, neither the tip leakage vortex cavitating flow nor flow pattern in the tip gap is ameliorated, the mean leakage velocity Vlk lies the range from 0.90 to 0.96. The region of high leakage velocity still exists and even the tip leakage vortex cavitation area is increased. Based on three-dimensional streamlines and vorticity transport equation, the interaction between the tip leakage flow and main flow leads to the variation of the tip leakage vortex cavitating flow. This paper aims for a useful reference to mitigate the tip leakage vortex cavitation and control the influence of the tip leakage vortex cavitating flow for the hydraulic machinery.

Numerical investigations on tip leakage flow characteristics and vortex trajectory prediction model in centrifugal compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 757-772 ◽  
Author(s):  
Huijing Zhao ◽  
Zhiheng Wang ◽  
Shubo Ye ◽  
Guang Xi
Keyword(s):  
Prediction Model ◽  
Flow Instability ◽  
Leading Edge ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Blade Tip

To better understand the characteristics of tip leakage flow and interpret the correlation between flow instability and tip leakage flow, the flow in the tip region of a centrifugal impeller is investigated by using the Reynolds averaged Navier–Stokes solver technique. With the decrease of mass flow rate, both the tip leakage vortex trajectory and the mainflow/tip leakage flow interface are shifted towards upstream. The mainflow/tip leakage flow interface finally reaches the leading edge of main blade at the near-stall condition. A prediction model is proposed to track the tip leakage vortex trajectory. The blade loading at blade tip and the averaged streamwise velocity of main flow within tip clearance height are adopted to determine the tip leakage vortex trajectory in the proposed model. The coefficient k in Chen’s model is found to be not a constant. Actually, it is correlated with h/b (the ratio of blade tip clearance height to blade tip thickness), because h/b will significantly influence the flow structure across the tip clearance. The effectiveness of the proposed prediction model is further demonstrated by tracking the tip leakage vortex trajectories in another three centrifugal impellers characterized with different h/b (s).

Study of Shock/Blade Tip Leakage Vortex/Boundary Layer Interaction in a Transonic Rotor With IDDES Method

2013 ◽  
Author(s):  
Ke Shi ◽  
Song Fu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Vortex Breakdown ◽  
Leading Edge ◽  
Wave Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Layer Interaction ◽  
Boundary Layer Interaction ◽  
Blade Tip

In the present study, Improved Delayed Detached Eddy Simulation (IDDES) based on k-ω-SST turbulence model is applied to study the unsteady phenomenon in a transonic compressor rotor. Particular emphasis is on the understanding of the complex underlying mechanisms for the flow unsteadiness caused by the interaction of passage shock, blade tip leakage vortex (BTLV) and the blade boundary layer. The sources of the significant unsteadiness of the flow are shown. At the lower span height, where the BTLV is far away, the shock wave ahead of the blade leading edge impinges on the suction surface boundary layer of the adjacent blade, causing the shock wave/boundary layer interaction (SWBLI). Boundary layer thickness grows, while flow separates after the interaction. Predicted by IDDES calculation, this shock-induced separation exists as a separation bubble. The flow reattaches very soon after separation. At the near tip region, the shock wave surface deforms due to the strong interaction between the shock and the BTLV. Oscillation of the shock wave surface near the vortex core infers an unsteady contend between the shock and the vortex. Iso-surfaces of the Q parameter are applied to identify the vortex and its structure. Normally, the vortex breakdown in the rotor passage will lead to stall. However, in the present transonic case, the vortex breakdown was observed even at the near peak efficiency point. While the mass flow rate decreases, the shock waves formed ahead of the rotor blade leading edge were pushed upstream, causing earlier casing wall boundary layer separation. Upstream moving behavior of the shock is considered a new stall process.

Effects of Stream Surface Inclination on Tip Leakage Flow Fields in Compressor Rotors

1998 ◽  
Vol 120 (4) ◽  
pp. 683-692 ◽  
Author(s):  
M. Furukawa ◽  
K. Saiki ◽  
K. Nagayoshi ◽  
M. Kuroumaru ◽  
M. Inoue
Keyword(s):  
Boundary Layer ◽  
Vortex Breakdown ◽  
Axial Flow ◽  
Flow Fields ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Wall Boundary Layer ◽  
Wall Boundary

Experimental and computational results of tip leakage flow fields in a diagonal flow rotor at the design flow rate are compared with those in an axial flow rotor. In the diagonal flow rotor, the casing and hub walls are inclined at 25 deg and 45 deg, respectively, to the axis of rotation, and the blade has airfoil sections with almost the same tip solidity as that of the axial flow rotor. It is found out that “breakdown” of the tip leakage vortex occurs at the aft part of the passage in the diagonal flow rotor. The “vortex breakdown” causes significant changes in the nature of the tip leakage vortex: disappearance of the vortex core, large expansion of the vortex, and appearance of low relative velocity region in the vortex. These changes result in a behavior of the tip leakage flow that is substantially different from that in the axial flow rotor: no rolling-up of the leakage vortex downstream of the rotor, disappearance of the casing pressure trough at the aft part of the rotor passage, large spread of the low-energy fluid due to the leakage flow, much larger growth of the casing wall boundary layer, and considerable increase in the absolute tangential velocity in the casing wall boundary layer. The vortex breakdown influences the overall performance, also: large reduction of efficiency with the tip clearance, and low level of noise.

Rotor-Tip Flow Fields Near Inception Point of Rotating Instability in an Axial-Flow Fan

2011 ◽  
Author(s):  
Takahiro Nishioka ◽  
Toshio Kanno ◽  
Kiyotaka Hiradate
Keyword(s):  
Vortex Breakdown ◽  
Rotor Blades ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Stall Inception ◽  
Tip Leakage ◽  
Rotating Instability ◽  
End Wall ◽  
Stagger Angle

Stall inception patterns at three stagger-angle settings for the highly loaded rotor blades were experimentally investigated in a low-speed axial-flow fan. Rotor-tip flow fields were also numerically investigated to clarify the mechanism behind the stall inception from a rotating instability. The rotating instability is confirmed near stall condition at the high stagger-angle settings for the highly loaded rotor blades as same as that for the moderate loaded rotor blades. The rotating instability is induced by an interaction between the incoming flow, the reversed tip-leakage flow, and the end-wall backflow from the trailing edge. At the high stagger-angle settings for the rotor blades, the interface between the incoming flow and the reversed tip leakage flow becomes parallel to the leading edge plane near and at the stall condition. Moreover, the tip leakage flow spills from the leading edge of the adjacent blade at the stall condition. The changes in the end-wall flow at the rotor tip are consistent with the criteria for the spike initiation suggested by Vo et al. and Hah et al. However, the short length-scale stall cell is not observed at the high stagger-angle settings. The tip-leakage vortex breakdown is confirmed at the three stagger-angle settings. The end-wall blockage induced by the tip-leakage vortex breakdown influences the development of the stall cell. Moreover, the development of the three-dimensional separation vortex induced by the tip-leakage vortex breakdown seems to be one of the criteria for spike-type stall inception.

Numerical Investigation On the Influences of Boundary Layer Ingestion On Tip Leakage Flow Structures and Losses in a Transonic Axial-Flow Fan

2021 ◽  
Author(s):  
Zhe Yang ◽  
Hanan Lu ◽  
Tianyu Pan ◽  
Qiushi Li
Keyword(s):  
Boundary Layer ◽  
Vortex Breakdown ◽  
Axial Flow ◽  
Leakage Flow ◽  
Shock Interaction ◽  
Tip Leakage Flow ◽  
Local Loss ◽  
Tip Leakage ◽  
Distorted Region ◽  
Blade Tip

Abstract In a boundary layer ingesting (BLI) propulsion system, the fan is continuously exposed to inflow distortions. The distorted inflows lead to non-uniform loss distributions along the radial and circumferential directions. Since the rotor tip suffers from higher intensive distortion, the local loss increment is a major contributor to the BLI fan performance penalty. To explore the effects of distorted inflows on tip leakage flow evolutions and associated mechanisms for increased loss in a BLI fan, three-dimensional full-annulus unsteady simulations are conducted. Results show that about 54% of total additional losses due to distortion are formed in tip region and more than 80% of tip entropy generation is related to the tip leakage flow. The intensities of leakage vortex-shock interactions vary at different annulus locations. When the rotor moves into distorted region, the vortex-shock interaction is weaker than the undistorted locations due to attenuated leakage flow. At the locations where the rotor is moving out from distorted region, the vortex-shock interaction is notably enhanced because the front part of blade tip airfoil suffers a higher load, resulting in a rapid vortex core expansion and eventually vortex breakdown. The increase of flow blockage in the front section of blade tip passages at local circumferential positions leads to a corresponding rise of flow loss. The findings in this study highlight the impacts of tip leakage flow on aerodynamic loss of fan working under BLI inflow distortion and provide improved understandings of loss mechanisms in a BLI fan.

Effects of Stream Surface Inclination on Tip Leakage Flow Fields in Compressor Rotors

1997 ◽  
Author(s):  
Masato Furukawa ◽  
Kazuhisa Saiki ◽  
Kenya Nagayoshi ◽  
Motoo Kuroumaru ◽  
Masahiro Inoue
Keyword(s):  
Boundary Layer ◽  
Vortex Breakdown ◽  
Axial Flow ◽  
Flow Fields ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Wall Boundary Layer ◽  
Wall Boundary

Experimental and computational results of tip leakage flow fields in a diagonal flow rotor at the design flow rate are compared with those in an axial flow rotor. In the diagonal flow rotor, the casing and hub walls are inclined at 25 degrees and 45 degrees, respectively, to the axis of rotation, and the blade has airfoil sections with almost the same tip solidity as that of the axial flow rotor. It is found out that “breakdown” of the tip leakage vortex occurs at the aft part of the passage in the diagonal flow rotor. The “vortex breakdown” causes significant changes in the nature of the tip leakage vortex: disappearance of the vortex core, large expansion of the vortex, and appearance of low relative velocity region in the vortex. These changes result in the behavior of the tip leakage flow substantially different from that in the axial flow rotor: no rolling-up of the leakage vortex downstream of the rotor, disappearance of the casing pressure trough at the aft part of the rotor passage, large spread of the low-energy fluid due to the leakage flow, much larger growth of the casing wall boundary layer, and considerable increase in the absolute tangential velocity in the casing wall boundary layer. The vortex breakdown influences the overall performance, also: large reduction of efficiency with the tip clearance, and low level of noise.

scholarly journals Numerical investigation into the mechanism regarding the inception and evolution of flow unsteadiness induced by the tip leakage flow in a transonic compressor

2020 ◽  
pp. 095765092091059
Author(s):  
Guangyao An ◽  
Yanhui Wu ◽  
Stephen Spence ◽  
Jinhua Lang ◽  
Zhiyang Chen ◽  
...  
Keyword(s):  
Vortex Breakdown ◽  
Axial Flow ◽  
Operating Point ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Flow Unsteadiness ◽  
The Third ◽  
Flow Fluctuation ◽  
Blade Tip

Unsteady flow in the blade tip region of modern axial flow compressors is one of the sources of loss, noise, and blade vibration. In some cases, it is potentially linked to stall inception. In this paper, the complex flow fields in the blade tip region of a transonic axial flow compressor rotor have been numerically investigated. The predicted results were validated by experimental data. Analyses of monitoring results of numerical probes showed that three typical flow characteristics occurred as the operating condition approached the stability limit: no flow fluctuation at the first operating point; flow fluctuation with high frequency and low amplitude at the second operating point; flow fluctuation with low frequency and high amplitude at the third operating point. Further analysis of the tip flow field showed that the evolution of the tip leakage vortex experienced three stages as the rotor was throttled. At the first stage, the TLV did not breakdown. At the second stage, a bubble-type breakdown of the tip leakage vortex occurred. At the third stage, a spiral-type breakdown of tip leakage vortex occurred. The current study demonstrated that the flow unsteadiness that appears within the test rotor was induced by the tip leakage vortex breakdown. Furthermore, with the transformation of the vortex breakdown form, the characteristic frequency and amplitude of the flow oscillation substantially changed.

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