Unsteady Investigation on Tip Flow Field and Rotating Stall in Counter-Rotating Axial Compressor

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Limin Gao ◽  
Ruiyu Li ◽  
Fang Miao ◽  
Yutong Cai
Keyword(s):  
Flow Field ◽  
Second Harmonic ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Tip Leakage ◽  
Future Goals

Contra-rotating axial compressor/fan (CRAC) is a promising technology to meet the future goals aircraft industry. Massive time accurate simulations are performed to investigate rotating stall in CRAC containing two counter-rotating rotors. Particularly, the back pressure increasing with a very small step to avoid missing flow field transition from stability to instability. Due to the canceling of the stator, the instability of downstream rotor is more stronger. The present studies mostly focus on the downstream rotor. The tip leakage flow field is analyzed in detail under near stall condition, which indicates that a secondary leakage flow plays an important role in the unsteadiness of CRAC's unsteady flow field. The frequency analysis in the tip clearance of downstream rotor under multiple near stall conditions captured the transition of the second harmonic frequency which can be used as stall inception signal. Moreover, the rotating stall onset process in real CRAC is simulated on the numerical stall.

scholarly journals Influence of Tip Clearance on Flow Characteristics of Axial Compressor

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1445
Author(s):  
Moru Song ◽  
Hong Xie ◽  
Bo Yang ◽  
Shuyi Zhang
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Axial Compressor ◽  
Suction Side ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Tip Clearance Vortex

This paper studies the influence of tip clearance on the flow characteristics related to the performance. Based on full-passage numerical simulation with experimental validation, several clearance models are established and the performance curves are obtained. It is found that there exists an optimum clearance for the stable working range. By analyzing the flow field in tip region, the role of the tip leakage flow is illustrated. In the zero-clearance model, the separation and blockage along the suction side is the main reason for rotating stall. As the tip clearance is increased to the optimum value, the separation is suppressed by the tip leakage flow. However, with the continuing increasing of the tip clearance, the scale and strength of the tip clearance vortex is increased correspondingly. When the tip clearance is larger than the optimum value, the tip clearance vortex gradually dominates the flow field in the tip region, which can increase the unsteadiness in the tip region and trigger forward spillage in stall onset.

Numerical Investigation of the Behavior of Tip Leakage Flow in a Low-Speed Axial Compressor Rotor at Near-Stall Condition

2012 ◽  
Author(s):  
Zhenzhen Duan ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Axial Compressor ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Stall Inception ◽  
Low Speed ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Corner Vortex

In the present work, time-accurate simulations were performed to investigate the unsteady flow fields in the tip region of a low-speed large-scale axial compressor rotor at near-stall condition. Firstly, the steady performance characteristic of the rotor was obtained by steady simulations. Secondly, a series of unsteady simulations were carried out to investigate the physical processes as the rotor approaching stall and the role of complex tip flow mechanism on flow instability in the rotor. The characteristics of tip leakage vortex were compared between design condition and near-stall condition. Detailed analyses were then employed to emphasize the development of stall inception and the comprehensions of the internal flow field. Two flow phenomena, spillage at the leading edge and backflow at the trailing edge, are found beyond the flow solution limit, which are both linked to the tip leakage flow. And the breakdown of the tip leakage vortex has been captured. The flow visualization and the quantification of passage blockage expose that the tip leakage vortex and corner vortex contribute most to the total passage blockage. Therefore, they are considered to be the key flow structures contributing to the rotating stall. Further analyses indicate that, in the current rotor, the interaction of the tip leakage flow and the corner vortex is clarified to be the key factor that leads to the rotating stall. In addition, the very initial disturbances of stall inception are discussed. And the interaction of the boundary layer migration on the blade suction side and the tip leakage vortex also plays a significant role in the stall inception.

Impact of Sinusoidal Tip Gaps on Axial Compressor Rotor Performance: A Flow Field Investigation

2019 ◽  
Author(s):  
Shraman Goswami ◽  
Ashima Malhotra
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Field Investigation ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Stall Margin ◽  
Tip Leakage ◽  
Compressor Rotor

Abstract Performance of an axial compressor rotor depends largely on the tip leakage flow. Tip leakage flow results in tip leakage vortex which is a source of loss. This has an impact on the compressor efficiency as well as stall margin. A lot of work has been done to understand the tip leakage flow and controlling the same. Active and passive stall margin improvement methods mainly target the tip leakage vortex. In the current study, numerical investigations are carried out to understand flow fields near tip region of rotors. The blade tip designed to have a tip gap as sine and cosine waves (single and double waves). Numerical methodology is validated with NASA Rotor37 test results. The performance parameters of the rotors with modified tip gap shapes are compared with constant tip clearance rotor. A detailed flow field investigation is presented to compare the tip flow structure and its impact on overall performance of the compressor.

Numerical study of the unsteady behaviors and rotating stall inception process in a counter-rotating axial compressor

2016 ◽  
Vol 230 (14) ◽  
pp. 2716-2727 ◽  
Author(s):  
Xiaochen Mao ◽  
Bo Liu
Keyword(s):  
Numerical Study ◽  
Axial Compressor ◽  
Leading Edge ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Suction Surface ◽  
Trailing Edge ◽  
Stall Inception ◽  
Tip Leakage

Unsteady computations of a counter-rotating axial compressor are performed and analyzed to investigate the unsteady behaviors in the compressor and the role of the tip leakage flow together with the rotating stall inception process. The results show that the oscillation on the pressure side is much stronger than that on the suction surface for both rotors, especially near the tip region where the trajectory of the tip leakage vortex (TLV) interacts with the blades most often. There exists a periodical leading edge spillage of the interface in rotor2 due to the unsteadiness of tip leakage flow (TLF) at near-stall condition. The blockage generated by the TLV increases dramatically due to the increasing strength of the TLV and the backflow phenomenon as the mass flow decreased. The appearance of the frequency components of 0.5 blade passing frequency (BPF) and 1.5BPF from 0.64BPF can be viewed as the rotating stall inception warning. The fluctuation strength of oscillation frequencies of 0.5BPF and 1.5BPF decreases rapidly from leading edge to trailing edge in rotor2, which indicates that the unsteady fluctuation of TLF at the leading edge in rotor2 is responsible for the stall inception of the compressor. Additionally, both the leading edge spillage and trailing edge backflow phenomena are observed for spike initiated rotating stall at stall point.

Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Application to Two Different Compressor Rotors

2014 ◽  
Author(s):  
Yasunori Sakuma ◽  
Toshinori Watanabe ◽  
Takehiro Himeno ◽  
Dai Kato ◽  
Takeshi Murooka ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
The Stability

The effect of a single circumferential casing groove on the stability enhancement of two different transonic compressors has been examined with CFD analysis. The differences in flow field and stall inception mechanism between two rotors are presented with principal focus on passage blockage and tip leakage flow behavior. Detailed observation showed that the blockage flow which leads the compressor to stall was different between each other. A parametric study conducted with respect to the axial location of the groove has clarified that the effect which groove has on the tip leakage flow behavior changes according to the blade tip loading and the design tip clearance gap at the location where the groove is applied. When the casing treatment was applied to the compressors with different instability mechanism, whether the casing treatment could enhance the stability of compressor or not was not only dependant on the extent of the influence which it had on the flow field but also on whether it could affect the original stall-initiating phenomena at the adequate location.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

Study of the Standard k-ε Model for Tip Leakage Flow in an Axial Compressor Rotor

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Yanfei Gao ◽  
Yangwei Liu ◽  
Luyang Zhong ◽  
Jiexuan Hou ◽  
Lipeng Lu
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Axial Compressor ◽  
Leakage Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor

AbstractThe standard k-ε model (SKE) and the Reynolds stress model (RSM) are employed to predict the tip leakage flow (TLF) in a low-speed large-scale axial compressor rotor. Then, a new research method is adopted to “freeze” the turbulent kinetic energy and dissipation rate of the flow field derived from the RSM, and obtain the turbulent viscosity using the Boussinesq hypothesis. The Reynolds stresses and mean flow field computed on the basis of the frozen viscosity are compared with the results of the SKE and the RSM. The flow field in the tip region based on the frozen viscosity is more similar to the results of the RSM than those of the SKE, although certain differences can be observed. This finding indicates that the non-equilibrium turbulence transport nature plays an important role in predicting the TLF, as well as the turbulence anisotropy.

A Proposal for Passive Wall Treatment Applied in High Performance Axial Flow Compressors

2020 ◽  
Author(s):  
Rubén Bruno Díaz ◽  
Jesuino Takachi Tomita ◽  
Cleverson Bringhenti ◽  
Francisco Carlos Elizio de Paula ◽  
Luiz Henrique Lindquist Whitacker
Keyword(s):  
Stokes Equations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Smooth Wall ◽  
Tip Leakage Flow ◽  
Viscous Effects ◽  
Stall Margin ◽  
Tip Leakage

Abstract Numerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

Influence of tip leakage flow and inlet distortion flow on a mixed-flow pump with different tip clearances within the stall condition

2019 ◽  
Vol 234 (4) ◽  
pp. 433-453 ◽  
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi
Keyword(s):  
Internal Flow ◽  
Energy Performance ◽  
Rotating Stall ◽  
Design Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Tip Leakage ◽  
Flow Pump

In order to investigate the effect of impeller tip clearance on internal flow fields and the rotating stall inception impacted by tip leakage vortex and inlet unsteady flow in a mixed-flow pump, mixed-flow pump models with tip clearances of 0.5 mm, 0.8 mm, and 1.1 mm were numerically calculated, and then the energy performance curves and internal flow structures were obtained and compared. The results show that the pump efficiency and the internal flow fields of numerical calculation are in good agreement with experimental results at design flow rate and near-stall condition. A portion of the positive slope segment appears in the energy performance curves under different tip clearances. The lowest head of the mixed-flow pump in the positive slope region decreases with the increase of the tip clearance while the highest head shows an opposite situation indicating that mixed-flow pumps are easier to stall under small tip clearance. At the design flow rate condition, the tip leakage vortex is relatively stable under different tip clearances and appears as a “snail shell” shape, whereas in rotating stall conditions, the “snail shell” shape disappear and the tip leakage flow on blade front forms a “flat” vortex structure. The inlet swirl flow not only affects the tip leakage flow in rotating stall conditions under different tip clearances, but also blocks the fluid from the inlet pipe. Under the circumstance of the same tip clearance, the main frequency amplitude of pressure pulsation coefficient gradually shifts away from blade passing frequency (96.67 Hz) to the axial frequency (24.17 Hz) when the pump operates in the stall condition.

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