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.

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.

Effects of Tip Clearance on Unsteady Flow Characteristics in an Axial Turbine Stage

2009 ◽  
Author(s):  
Hao Sun ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Suction Side ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The clearance between the rotor blade tip and casing wall in turbomachinery passages induces leakage flow loss and thus degrades aerodynamic performance of the machine. The flow field in turbomachinery is significantly influenced by the rotor blade tip clearance size. To investigate the effects of tip clearance size on the rotor-stator interaction, the turbine stage profile from Matsunuma’s experimental tests was adopted, and the unsteady flow fields with two tip clearance sizes of 0.67% and 2.00% of blade span was numerical simulated based on Harmonic method using NUMECA software. By comparing with the domain scaling method, the accuracy of the harmonic method was verified. The interaction mechanism between the stator wake and the leakage flow was investigated. It is found that the recirculation induced by the stator wake is separated by a significant “interaction line” from the flow field close to the suction side in the clearance region. The trend of the pressure fluctuation is contrary on both sides of the line. When the stator wakes pass by the suction side, the pressure field fluctuates and the intensity of the tip leakage flow varies. With the clearance size increasing, the “interaction line” is more far away from the suction side and the intensity of tip leakage flow also fluctuates more strongly.

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.

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.

Numerical Simulation of Tip Clearance Control in Axial Turbine Rotor: Part 2—Passive Control of Five Different Tip Platforms

2008 ◽  
Author(s):  
Wei Li ◽  
Wei-Yang Qiao ◽  
Kai-Fu Xu ◽  
Hua-Ling Luo
Keyword(s):  
Flow Control ◽  
Passive Control ◽  
Suction Side ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow

The tip leakage flow has significant effects on turbine in loss production, aerodynamic efficiency, etc. Then it’s important to minimize these effects for a better performance by adopting corresponding flow control. The active turbine tip clearance flow control with injection from the tip platform is given in Part-1 of this paper. This paper is Part-2 of the two-part papers focusing on the effect of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip (Partial SS Squealer), a double squealer tip (Double Side Squealer), a pressure side tip shelf with inclined squealer tip on a double squealer tip (Improved PS Squealer), a tip platform extension edge in pressure side (PS Extension) and in suction side (SS Extension) respectively. Combined with the turbine rotor and the numerical method mentioned in Part 1, the effects of passive turbine tip clearance flow controls on the tip clearance flow were sequentially simulated. The detailed tip clearance flow fields with different squealer rims were described with the streamline and the velocity vector in various planes parallel to the tip platform or normal to the tip leakage vortex core. Accordingly, the mechanisms of five passive controls were put in evidence; the effects of the passive controls on the turbine efficiency and the tip clearance flow field were highlighted. The results show that the secondary flow loss near the outer casing including the tip leakage flow and the casing boundary layer can be reduced in all the five passive control methods. Comparing the active control with the passive control, the effect brought by the active injection control on the tip leakage flow is evident. The turbine rotor efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine rotor efficiency, and it increased by 0.215%.

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.

Squealer Tip Leakage Flow Characteristics in Transonic Condition

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Wei Li ◽  
Hongmei Jiang ◽  
Qiang Zhang ◽  
Sang Woo Lee
Keyword(s):  
Flow Characteristics ◽  
Leading Edge ◽  
Flow Region ◽  
Suction Side ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Cavity Depth ◽  
Tip Leakage ◽  
Flow Flux ◽  
Subsonic Region

The over-tip-leakage (OTL) flow characteristics for a typical squealer tip of a high-pressure turbine blade, which consists of subsonic and transonic flow, have been numerically investigated in the present study, in comparison with the corresponding flat tip results. For the squealer tip employed, flow choking behavior still exists above the tip surface, even though the Mach number is lower and the transonic region is smaller than that for the flat tip. Detailed flow structure analysis shows that most of the fluid entering the squealer cavity is from the frontal leading edge region. The fluid migrates along the cavity and is ejected at various locations near the suction side rim. These fluids form a large subsonic flow zone under the supersonic flow passing over the tip gap which reduces the OTL flow flux. The squealer design works even in the presence of choked OTL flow. Comparisons between results from three different cavity depths with and without relative casing motion suggest that the over-tip-leakage flow flux has much dependence upon the cavity depth for the subsonic region, but is less sensitive to the depth for the transonic tip flow region. Such behavior has been confirmed with and without the existence of relative casing motion.

Unsteady Simulation of an Axial Compressor Stage With Casing and Blade Passive Treatments

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Nicolas Gourdain ◽  
Francis Leboeuf
Keyword(s):  
Boundary Layer ◽  
Passive Control ◽  
Axial Compressor ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Leakage Flow ◽  
Compressor Stage ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Good Ability

This paper deals with the numerical simulation of technologies to increase the compressor performances. The objective is to extend the stable operating range of an axial compressor stage using passive control devices located in the tip region. First, the behavior of the tip leakage flow is investigated in the compressor without control. The simulation shows an increase in the interaction between the tip leakage flow and the main flow when the mass flow is reduced, a phenomenon responsible for the development of a large flow blockage region at the rotor leading edge. A separation of the rotor suction side boundary layer is also observed at near stall conditions. Then, two approaches are tested in order to control these flows in the tip region. The first one is a casing treatment with nonaxisymmetric slots. The method showed a good ability to control the tip leakage flow but failed to reduce the boundary layer separation on the suction side. However, an increase in the operability was observed but with a penalty for the efficiency. The second approach is a blade treatment that consists of a longitudinal groove built in the tip of each rotor blade. The simulation pointed out that the device is able to control partially all the critical flows with no penalty for the efficiency. Finally, some recommendations for the design of passive treatments are presented.

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