Behavior of Tip Leakage Flow Behind an Axial Compressor Rotor

1986 ◽  
Vol 108 (1) ◽  
pp. 7-14 ◽  
Author(s):  
M. Inoue ◽  
M. Kuroumaru ◽  
M. Fukuhara
Keyword(s):  
Incidence Angle ◽  
Axial Compressor ◽  
Performance Testing ◽  
Tip Clearance ◽  
Vortex Center ◽  
Tip Leakage Flow ◽  
Flow Measurements ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Work Done

Performance testing and detailed flow measurements were made in an axial compressor rotor with various tip clearances. The experiments were conducted on the condition of the same incidence angle at midspan. Thus, the effect of tip clearance distinguished from that of incidence angle was investigated on the overall performance, work-done factor, blockage factor, and increases in displacement, momentum, and blade-force-deficit thicknesses of the casing wall boundary layer, The phase-locked flow patterns obtained by the multisampling technique show clear evidence of a leakage vortex core behind the rotor. Behavior of the leakage vortex was clarified for various tip clearances by examining loci of the vortex center, decay characteristics of the vorticity at the center, and the total amount of vorticity shed from the blade tip. These results were compared with the leakage vortex model presented by Lakshminarayana.

scholarly journals Effect of Circumferential Single Casing Groove Location on the Flow Stability under Tip-Clearance Effect in a Transonic Axial Flow Compressor Rotor

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6143
Author(s):  
Xiaoxiong Wu ◽  
Bo Liu ◽  
Botao Zhang ◽  
Xiaochen Mao
Keyword(s):  
Control Mechanism ◽  
Incidence Angle ◽  
Axial Flow ◽  
Flow Stability ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Flow Angle ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor

Numerical simulations have been performed to study the effect of the circumferential single-grooved casing treatment (CT) at multiple locations on the tip-flow stability and the corresponding control mechanism at three tip-clearance-size (TCS) schemes in a transonic axial flow compressor rotor. The results show that the CT is more efficient when its groove is located from 10% to 40% tip axial chord, and G2 (located at near 20% tip axial chord) is the best CT scheme in terms of stall-margin improvement for the three TCS schemes. For effective CTs, the tip-leakage-flow (TLF) intensity, entropy generation and tip-flow blockage are reduced, which makes the interface between TLF and mainstream move downstream. A quantitative analysis of the relative inlet flow angle indicates that the reduction of flow incidence angle is not necessary to improve the flow stability for this transonic rotor. The control mechanism may be different for different TCS schemes due to the distinction of the stall inception process. For a better application of CT, the blade tip profile should be further modified by using an optimization method to adjust the shock position and strength during the design of a more efficient CT.

Performance and Stability Enhancement of NASA Rotor 37 Applying Abradable Coating

2005 ◽  
Author(s):  
Behnam H. Beheshti ◽  
Bijan Farhanieh ◽  
Kaveh Ghorbanian ◽  
Joao A. Teixeira ◽  
Paul C. Ivey
Keyword(s):  
Flow Characteristics ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Compressors ◽  
Compressor Rotor ◽  
Abradable Coating ◽  
Blade Tip ◽  
Stability Enhancement

Improvements in sealing mechanism between the rotating and the stationary parts of a turbomachine can extensively reduce the endwall leakage flow. In this regard, abradable seals are incorporated into compressor and turbine blade-tip region. In a gas turbine, equipped with abradable seals, tip of the rotor blade is designed to cut into the material coating of the casing and to form a close fitted circumferential groove for the movement of the blade tip. As a result, the resistance to the leakage flow in the tip gap region increases due to smaller tip clearances (available without any rub-induced damages). Minimizing the tip clearance size can lead to an increase in performance and stability. This paper presents a numerical investigation of abradable coating as a means to seal the tip leakage flow in NASA Rotor 37, a transonic axial compressor rotor. In order to validate the multi block model used in the tip gap region, various flow characteristics are verified with the experimental data for smooth casing at a design clearance of 0.5% span. To have a better understanding of how an abradable seal affects the passage flow field, smooth casing and abradable coating are studied and results are compared for various models including two different incursion depth and width. Results indicate that the application of abradable coating in transonic axial compressors can efficiently improve the performance and stability.

scholarly journals Study of Sweep and Induced Dihedral Effects in Subsonic Axial Flow Compressor Passages—Part I: Design Considerations—Changes in Incidence, Deflection, and Streamline Curvature

2009 ◽  
Vol 2009 ◽  
pp. 1-11 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Design Parameters ◽  
Tip Leakage Flow ◽  
Efficient Energy Transfer ◽  
Compressor Rotor ◽  
Mass Flow Rates ◽  
Flow Compressor

This article presents the study of Tip Chordline Sweeping (TCS) and Axial Sweeping (AXS) of low-speed axial compressor rotor blades against the performance of baseline unswept rotor (UNS) for different tip clearance levels. The first part of the paper discusses the changes in design parameters when the blades are swept, while the second part throws light on the effect of sweep on tip leakage flow-related phenomena. 15 domains are studied with 5 sweep configurations (, TCS, TCS, AXS, and AXS) and for 3 tip clearances (0.0%, 0.7%, and 2.7% of the blade chord). A commercial CFD package is employed for the flow simulations and analysis. Results are well validated with experimental data. Forward sweep reduced the flow incidences. This is true all over the span with axial sweeping while little higher incidences below the mid span are observed with tip chordline sweeping. Sweeping is observed to lessen the flow turning. AXS rotors demonstrated more efficient energy transfer among the rotors. Tip chordline sweep deflected the flow towards the hub while effective positive dihedral induced with axial sweeping resulted in outward deflection of flow streamlines. These deflections are more at lower mass flow rates.

Numerical Study on the Effects of Casing Treatment on Unsteadiness of Tip Leakage Flow in an Axial Compressor

2012 ◽  
Author(s):  
Yoojun Hwang ◽  
Shin-Hyoung Kang
Keyword(s):  
Numerical Study ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Operating Range ◽  
Compressor Rotor ◽  
Flow Through

A low speed axial compressor with casing treatment of axial slots was numerically investigated. Time-accurate numerical calculations were performed to simulate unsteady flow in the rotor tip region and the effects of casing treatment on the flow. Since the compressor rotor had a large tip clearance, it was found that the tip leakage flow had an inherent unsteady feature that was not associated with rotor rotation. The unsteadiness of the tip leakage flow was induced by changes in the blade loading due to the pressure distribution formed by the tip leakage flow. This characteristic is called rotating instability or self-induced unsteadiness. The frequency of the flow oscillation was found to decrease as the flow rate was reduced. On the other hand, as expected, the operating range was improved by casing treatment, as shown by calculations in good agreement with the experimentally measured data. The unsteadiness of the tip leakage flow was alleviated by the casing treatment. The interaction between the flow in the tip region and the re-circulated flow through the axial slots was observed in detail. The removal and injection of flow through the axial slots were responsible not only for the extension of the operating range but also for the alleviation of the unsteadiness. Analyses of instantaneous flow fields explained the mechanism of the interaction between the casing treatment and the unsteady oscillation of the tip leakage flow. Furthermore, the effects of changes in the amount of re-circulation and the location of the removal and injection flow on the unsteadiness of the tip leakage flow were examined.

Numerical simulation of unsteady tip clearance flow in an isolated axial compressor rotor blades row

2011 ◽  
Vol 226 (1) ◽  
pp. 82-93 ◽  
Author(s):  
R Taghavi-Zenouz ◽  
S Eslami
Keyword(s):  
Experimental Data ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Clearance Flow

Three-dimensional unsteady numerical simulations were carried out to analyse tip clearance flow in a low-speed isolated axial compressor rotor blades row. A flow solver has been used for the current study utilizing the large eddy simulation (LES) technique. Periodic tip leakage flow and its propagation trajectories were simulated in detail. A number of pseudo pressure transducers were imposed on the pressure side of the blade for detection of unsteady surface pressures to provide a calculation of tip leakage flow frequencies. Two different sizes of tip clearance were considered for simulations and analyses. Non-dimensional frequencies of the tip leakage flow were calculated and final results were compared to those of existing numerical and experimental data. Final results demonstrated that in contrast to the Reynolds averaged Navier–Stokes (RANS) model, the LES method shows considerable dependency of frequency characteristics of the tip leakage flow to the gap size and can detect different frequency spectrums along the blade surface. All the results obtained through the current numerical approach were in close agreement with those of existing experimental data.

Performance Desensitization for a High-Speed Axial Compressor

2018 ◽  
Author(s):  
Yassine Souleimani ◽  
Huu Duc Vo ◽  
Hong Yu
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Lower Sensitivity ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
Compressor Rotor

The increase in compressor tip clearance over the lifespan of an aero-engine leads to a long-term degradation in its fuel consumption and operating envelope. A highly promising recent numerical study on a theoretical high-speed axial compressor rotor proposed a novel casing treatment to decrease performance and stall margin sensitivity to tip clearance increase. This paper aims to apply and analyze, through CFD simulations, this casing treatment concept to a representative production axial compressor rotor with inherently lower sensitivity to tip clearance increase and complement the explanation on the mechanism behind the reduction in sensitivity. Simulations of the baseline rotor showed that the lower span region contribute as much to the pressure ratio sensitivity as the tip region which is dominated by tip leakage flow. In contrast, the efficiency sensitivity is mainly driven by losses occurring in the tip region. The novel casing treatment was successfully applied to the baseline rotor through a design refinement. Although the casing treatment causes some penalty in nominal performance, it completely reversed the pressure ratio sensitivity (i.e. pressure ratio increases with tip clearance) and reduced the efficiency sensitivity. The reversed pressure ratio sensitivity is explained by a rotation in the core flow in the lower span region indirectly induced by the flow injection from the casing treatment. The lower efficiency sensitivity comes from a reduction in the amount of fluid that crosses the tip clearance of two adjacent blades, known as double leakage. The casing treatment’s beneficial effect on stall margin sensitivity is less obvious because of the stall inception type of the baseline rotor and its change in the presence of the casing treatment.

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 Effect of a Recirculating Type Casing Treatment on a Highly Loaded Axial Compressor Rotor

2019 ◽  
Vol 4 (1) ◽  
pp. 5
Author(s):  
Motoyuki Kawase ◽  
Aldo Rona
Keyword(s):  
High Performance ◽  
Incidence Angle ◽  
Axial Compressor ◽  
Weight Ratio ◽  
Surface Flow ◽  
Test Case ◽  
Tip Leakage Flow ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Compressor Rotor

The tip leakage flow over the blades of an axial compressor rotor adversely affects the axial rotor efficiency and can determine the onset of tip leakage stall. The performance of a new casing treatment concept in the shape of an axisymmetric recirculation channel is explored by steady Reynolds-Averaged Navier–Stokes (RANS) realizable k-ε modelling on the NASA Rotor 37 test case. The modelling exposed a number of attractive features. The casing treatment increased the stall margin at no penalty to the rotor isentropic efficiency over the rotor operating line. A recirculation in the casing channel self-activated and self-adjusted with the rotor loading to provide more passive flow control at higher rotor loading conditions. The nozzle-shaped recirculation channel outflow opposed the tip leakage jet, re-located the casing surface flow interface further downstream, and reduced the rotor blade tip incidence angle. This combination of features makes the new casing treatment particularly attractive for applications to high thrust-to-weight ratio engines, typical of high-performance jet aircraft.

The Structure of Tip Clearance Flow in Axial Flow Compressors

1995 ◽  
Vol 117 (3) ◽  
pp. 336-347 ◽  
Author(s):  
B. Lakshminarayana ◽  
M. Zaccaria ◽  
B. Marathe
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Complex Nature ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Blade Tip ◽  
Flow Compressor

Detailed measurements of the flow field in the tip region of an axial flow compressor rotor were carried out using a rotating five-hole probe. The axial, tangential, and radial components of relative velocity, as well as the static and stagnation pressures, were obtained at two axial locations, one at the rotor trailing edge, the other downstream of the rotor. The measurements were taken up to about 26 percent of the blade span from the blade tip. The data are interpreted to understand the complex nature of the flow in the tip region, which involves the interaction of the tip leakage flow, the annulus wall boundary layer and the blade wake. The experimental data show that the leakage jet does not roll up into a vortex. The leakage jet exiting from the tip gap is of high velocity and mixes quickly with the mainstream, producing intense shearing and flow separation. There are substantial differences in the structure of tip clearance observed in cascades and rotors.

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.

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