Numerical Investigation on the Effects of Self-Excited Tip Flow Unsteadiness and Blade Row Interactions on the Performance of a Low Speed Compressor Rotor

2008 ◽  
Author(s):  
Daniel Lee ◽  
Paul D. Orkwis ◽  
Fu-Lin Tsung ◽  
William Magnuszewski ◽  
Christopher Noll ◽  
...  
Keyword(s):  
Steady State ◽  
Numerical Investigation ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Tip Leakage Flow ◽  
Low Speed ◽  
Flow Unsteadiness ◽  
Compressor Rotor ◽  
Blade Row

A numerical investigation has been conducted to determine the effects of self-excited tip-leakage flow unsteadiness, upstream stator wakes, and downstream blade row interactions on the performance prediction of a low speed research compressor rotor. Calculations included a single blade-row rotor configuration as well as two multi-blade row configurations: one where the rotor was modeled with an upstream stator and a second where the rotor was modeled with a downstream stator. Steady-state and time accurate calculations were performed using a RANS solver and the results were compared with detailed experimental data at operating conditions corresponding to the compressor design point, near stall and a mid-point between the two. Differences in the performance predictions between the three configurations were then used to determine the effect of the upstream stator wakes and the downstream blade row interactions. Results obtained show that for this compressor with rather large tip clearance, time-accurate calculations are a vast improvement over steady-state calculations, but the upstream stator wakes and the downstream blade row interactions have only a small effect on the numerical solution. In this paper, changes in the rotor flow field due to the upstream and downstream stators are investigated and discussed to explain the limited impact of the stator wakes and downstream blade row interactions on this tip dominated flow. In addition, the unsteady nature of the rotor tip vortex at near stall conditions is discussed to explain the improvement of time accurate analysis over steady state computations.

Characteristics of the Tip Leakage Vortex in a Low-Speed Axial Compressor With Different Rotor Tip Gaps

2012 ◽  
Author(s):  
Zhibo Zhang ◽  
Xianjun Yu ◽  
Baojie Liu
Keyword(s):  
Axial Compressor ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Tip Clearance ◽  
Test Facility ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Low Speed ◽  
Tip Leakage

The detailed evolutionary processes of the tip leakage flow/vortex inside the rotor passage are still not very clear for the difficulties of investigating of them by both experimental and numerical methods. In this paper, the flow fields near the rotor tip region inside the blade passage with two tip gaps, 0.5% and 1.5% blade height respectively, were measured by using stereoscopic particle image velocimetry (SPIV) in a large-scale low speed axial compressor test facility. The measurements are conducted at four different operating conditions, including the design, middle, maximum static pressure rise and near stall conditions. In order to analyze the variations of the characteristics of the tip leakage vortex (TLV), the trajectory, concentration, size, streamwise velocity, and the blockage parameters are extracted from the ensemble-averaged results and compared at different compressor operating conditions and tip gaps. The results show that the formation of the TLV is delayed with large tip clearance, however, its trajectory moves much faster in an approximately linear way from the blade suction side to pressure side. In the tested compressor, the size of the tip gap has little effects on the scale of the TLV in the spanwise direction, on the contrary, its effects on the pitch-wise direction is very prominent. Breakdown of the TLV were both found at the near-stall condition with different tip gaps. The location of the initiation of the TLV breakdown moves downstream from the 60% chord to 70% chord as the tip gap increases. After the TLV breakdown occurs, the flow blockage near the rotor tip region increases abruptly. The peak value of the blockage effects caused by the TLV breakdown is doubled with the tip gap size increasing from 0.5% to 1.5% blade span.

Numerical Study on the Response of Tip Leakage Flow Unsteadiness to Micro Tip Injection in a Low-Speed Isolated Compressor Rotor

2007 ◽  
Author(s):  
Shaojuan Geng ◽  
Hongwu Zhang ◽  
Jingyi Chen ◽  
Weiguang Huang
Keyword(s):  
Numerical Study ◽  
The Self ◽  
Axial Position ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Low Speed ◽  
Tip Leakage ◽  
Flow Unsteadiness ◽  
Compressor Rotor ◽  
Tip Injection

A numerical study on the unsteady tip leakage flow with discrete micro tip injection from casing shroud in a low-speed isolated axial compressor rotor is presented. The main target is to clarify the flow mechanism of how the stall control measures act on the tip leakage flow typified by its self-induced unsteady flow characteristics. At operating condition near stall point, a series of calculations have been carried out for different axial position of injector and different injected mass flow rate. The computation results of flow field near rotor tip region show that under the influence of injected flow, the transient pressure distribution fluctuates along blade chord on both pressure and suction sides with respect to the relative position of injector and rotor. The pressure difference across the pressure and suction sides of compressor blade changes correspondingly, thus introduces a forced flow unsteadiness interacting with the unsteady tip leakage flow. When the injection is relatively strong and able to meet the tip leakage flow at its origination, the self-induced unsteadiness of tip leakage flow can be suppressed completely. In most cases, both frequency components of the self-induced unsteadiness and forced-induced unsteadiness are co-existing. The corresponding transient flow contours show that a local high pressure spot appears near blade pressure side, which moves downstream and shifts the tip leakage flow trajectory with less or without touching the neighboring pressure surface of the blade. Based on this understanding of discrete tip injection as force-induced flow unsteadiness, the numerical results are also analyzed to optimize the effect of injection in changing the route of tip leakage flow trajectories and therefore the chance of stability improvement of the compressor rotor.

Tip Flow Unsteadiness and Blade Row Interactions for a Low-Speed Compressor Rotor

2013 ◽  
Vol 29 (6) ◽  
pp. 1346-1356 ◽  
Author(s):  
Daniel Lee ◽  
Paul D. Orkwis ◽  
Fu-Lin Tsung ◽  
William Magnuszewski ◽  
Christopher Noll ◽  
...  
Keyword(s):  
Low Speed ◽  
Flow Unsteadiness ◽  
Compressor Rotor ◽  
Blade Row

scholarly journals Commencement and Development Processes of Flow Unsteadiness at Tip Clearance Region of a Low Speed Axial Compressor Rotor Blade Row

2017 ◽  
Vol 61 (4) ◽  
pp. 288
Author(s):  
Marhamat Zeinali ◽  
Sarallah Abbasi ◽  
Abolfazl Hajizadeh Aghdam
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Low Speed ◽  
Tip Leakage ◽  
Blade Row ◽  
Development Processes ◽  
Flow Frequency

Commencement and development processes of unsteadiness, caused by blade row tip leakage flow in a low speed axial compressor, are investigated and results are presented in this paper. Analyses are based on results obtained through numerical simulation of unsteady three dimensional viscous flows. Discretization of the Navier-Stokes’s equations has been carried out based on upwind second-order scheme and k-ω-SST turbulence modeling was used for estimation of eddy viscosity.Three different circumstances, including design point and two near stall conditions are considered for investigation and discussion. Tip leakage flow frequency spectrums were examined through surveying instantaneous static pressure signals imposed on the blades surfaces. Focusing on time dependent flow structure results signified existence of some pressure peaks at near stall conditions. These regions, which are created as a result of interaction between main inflow and tip leakage flow, lead to occurrence of self-induced unsteadiness. However, at design condition, flow is more affected by the main inflow instead of the tip leakage flow. By occurrence of self-induced unsteadiness, which occurs at near stall condition, tip leakage vortex flow starts to fluctuate at a frequency about the blade passing frequency. Further decrease in the flow rate up to a specified value showed no significant variations in the leakage flow frequency, but, on the other hand, magnified amplitudes of this unsteadiness.

Numerical Investigation of the Aerodynamic Performance of Hybrid Aerofoils in a 1.5-Stage Low-Speed Compressor

2021 ◽  
Author(s):  
Jannik Eckel ◽  
Volker Gümmer
Keyword(s):  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Limiting Factors ◽  
Stall Inception ◽  
Low Speed ◽  
Flow Phenomena

Abstract This paper describes the numerical investigation of hybrid aerofoils in a 1.5-stage low-speed compressor, which in its baseline configuration features a conventional rotor and a tandem stator. Both of these are eventually replaced by hybrid aerofoils, using the initial tandem blade profile geometry around mid-span. In this course of design investigations a pure tandem rotor was also generated and analysed as the initial geometry of the hybrid rotor. The aerodynamic design and performance of the tandem rotor and the hybrid aerofoils will be discussed in this paper. The numerical analysis is aimed at understanding the secondary flow phenomena and limiting factors of the working range of the reference stage. Based on this knowledge, the advantages of the hybrid aerofoil design will be discussed. On one hand, the origin and development of three-dimensional flow structures near the endwall regions of the rear vane of the tandem stator are investigated in detail, as they appear to play a major role at de-throttled operating conditions. On the other hand, the tip vortex leakage of the single rotor and the pure tandem rotor are considered, showing the tip vortex taking a major role in loss generation and stall inception at throttled operating conditions, and interacting with the tandem stator secondary flow phenomena at the casing. Both these performance-limiting factors can be addressed by implementing hybrid aerofoils. The paper presents and discusses the improvement of secondary flow loses and aerodynamic performance based on steady-state RANS simulations.

Unsteady 3D Simulation of a Jet Fan With Symmetric Blades

2006 ◽  
Author(s):  
J. M. Ferna´ndez Oro ◽  
K. M. Argu¨elles Di´az ◽  
C. Santolaria Morros
Keyword(s):  
Tangential Velocity ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Wake Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Jet Fan ◽  
The Impact

This work develops the numerical modeling of a monoplane axial jet fan with symmetric blades. The goal of the study is the simulation of the flow inside a rotor with elliptic airfoils, where the Kutta condition cannot be satisfied. The unsteady 3D model includes tip clearance gridding and a sliding mesh technique to simulate transient effects. The flow patterns inside the blade passage and the wake-core structure will be studied at design operating conditions. Also, the interaction of the tip leakage flow with time-averaged structures will be analyzed in detail. Therefore, the impact of the tip vortex in the mean time performance of the jet fan will be introduced. The investigation shows how the tip leakage vortex modifies the blade loading on the suction surface. The leakage flow rolls-up in a vortical structure at the suction side, establishing a mixing mechanism that produces a low axial velocity region. As a result, the adverse pressure gradient is enhanced and a major flow separation overcomes. This feature is especially critical in case of a rotor with symmetric blades, where the flow is always detached at the trailing edge. The simulation is carried out using a commercial code, FLUENT, which resolves the Navier-Stokes set of equations. An extremely high dense mesh is introduced in the model, so tip leakage is expected to be well-captured. In addition, fully-developed detachment of the boundary layer requires superior discretizations and high quality meshes, so restrictive y+ criteria have been employed for both endwall boundaries and blade surfaces. Turbulence modeling is closed using URANS models. The Reynolds Stress Model (RSM) has been employed because of its suitable predictions for rotating flow passages. In addition, this model considers anisotropic turbulence, and effects of curvature and rotation are directly addressed in the transport equations. Therefore, swirl effects of the tip vortex are expected to be well-captured. The numerical results are compared with previous experimental data of velocity fields to validate the simulation. Axial and tangential velocity profiles were obtained using a five-hole probe. Complementary, the instantaneous wake flow structure was measured with a dual hot wire anemometer.

Unsteady Modelling of the Tip Clearance Flow in an Inlet Vaned, Low-Speed Axial Fan: Deterministic Interactions of Stator Wakes and Tip Vortex Structures

2009 ◽  
Author(s):  
Jesu´s Manuel Ferna´ndez Oro ◽  
Katia Mari´a Argu¨elles Di´az ◽  
Carlos Santolaria Morros ◽  
Mo´nica Galdo Vega
Keyword(s):  
Three Dimensional ◽  
Vortex Structures ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Fan ◽  
Low Speed ◽  
Tip Leakage ◽  
The Impact

In last years, numerical modelling has reached a significant level of maturity in the analysis of axial turbomachinery flows. Full-unsteady, three-dimensional computations have been demonstrated as a powerful tool to characterize viscous phenomena on blade row interactions and blade passage structures. In particular, major effects have been focused on the study of deterministic fluctuations in order to quantify the impact of periodic unsteadiness on the time-averaged flow. An additional complexity concerns to the influence of the tip vortex structures on the deterministic patterns. Hence, some researchers have advanced experimental evidences on the contribution of tip leakage flow to the time-resolved distributions. Tip vortex, shedding energy at a wide range of scales, has been shown to be significant in the description of the spanwise momentum transfer and the appearance of mixing losses. Recently, the authors have investigated the impact of the tip vortex on the passage flow structures of a jet fan with symmetric blades. This work revealed valuable information about tip vortex transport in low-speed axial turbomachinery and demonstrated the ability of commercial codes to simulate three-dimensional, vortical structures with high accuracy. The present paper takes advantage of the same numerical methodology to highlight the influence of the deterministic correlations that describe the stator-rotor interaction on the tip vortex in a single-stage axial fan. Up to now, few works addressing deterministic contributions over the tip leakage flow are available in the literature, so more investigation is needed to understand the complexity of these physical mechanisms. Our contribution to the topic is based on a 3D, unsteady numerical simulation of the flow within a reduced periodic domain of the full-annulus axial stage, composed by only 3-vane and 2-blade passages. This simplification allows an enhancement of the grid density when massive parallel computations are employed. Also, comparison with experimental data measured using hot-wire anemometry is provided to validate the numerical model. The results show how the non-uniformities of the stator wake-core structure in the relative frame of reference are conditioning the tip leakage flow, addressing the influence of the operating conditions or the interrow spacing. The final objective is to provide levels of instabilities in the tip vortex derived from deterministic non-uniformities associated to vane-to-vane flow patterns, applicable in further modelling of deterministic stresses.

Numerical Investigation of the Solidity Effect on Linear Compressor Cascades

2014 ◽  
Author(s):  
J. Sans ◽  
M. Resmini ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Numerical Investigation ◽  
State Of The Art ◽  
Leading Edge ◽  
Operating Conditions ◽  
Compressor Cascade ◽  
Minimum Loss ◽  
Low Speed ◽  
High Mach ◽  
The Stability ◽  
The Impact

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on low-speed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-of-the-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and compared with existing correlations for both configurations and various Mach numbers that have been selected in order to match typical booster stall and choke operating conditions. The emphasis is set on the minimum loss performance at mid-span. The impact of the solidity on the operating range and the stability of the cascade are also studied.

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.

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.

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