The Flow Field in the Tip Clearance Region of an Axial Compressor Rotor

1999 ◽  
Author(s):  
Toshiyuki Arima ◽  
Masatoshi Shirotori ◽  
Yoshihiro Yamaguchi
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Grid Topology ◽  
Clearance Flow ◽  
Inflow Condition ◽  
Blade Tip ◽  
Single Block

A three-dimensional, Reynolds-averaged, compressible Navier-Stokes analysis (using a multi-block grid with the grid embedded in the tip-clearance space) has been developed to study the tip-clearance flow of an axial compressor rotor. A low-Reynolds number k-ε model have been used to reproduce the effects of turbulence. In order to assess the effect of the tip-clearance-grid treatment on prediction for the tip-clearance flow, calculations using a single-block grid (pinched grid topology) and multi-block grid (embedded grid topology) have been performed to calculate the flow field of NASA Rotor 37. The results are compared with experimental data. It has been found that both the single-block and multi-block approaches give a good agreement with the experimental data regarding the overall performance map of the rotor. For the prediction of the spanwise distributions of averaged aerodynamic properties downstream of the rotor, however, the orderly grid over the blade tip associated with the embedded grid has produced accurate predictions particularly from 40% to 80% span. In order to investigate the tip-clearance flow for different operating conditions, calculations have been performed for conditions at 100% (transonic inflow condition) and 60% (subsonic inflow condition) of the design point speed. Computed limiting streamlines at the blade tip surface and particle traces released from the tip-clearance have been used to study the tip-clearance flow. At the 100% speed, both separation and reattachment lines have been observed and a separation bubble occurs. At the 60% speed, the separation line shifts to the blade pressure side and the reattachment line can be partly observed near the leading edge of the blade tip surface. In order to investigate the interaction of the leakage vortex from the tip clearance with the main flow, the computed secondary flows on the cross-flow sections have been analyzed at the 100% and the 60% speeds. At the 100% speed, the vortex core apparently increases in size, as it moves downstream. At 60% speed, the second vortex, first reported by Suder and Celestina in 1994, is barely observable. Furthermore, the trajectory of vortex core identified using a semi-analytical method has also been used to study the vortex motion in the flow field near the blade tip.

Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 127-142
Author(s):  
Wei Zhu ◽  
Songtao Wang ◽  
Longxin Zhang ◽  
Jun Ding ◽  
Zhongqi Wang
Keyword(s):  
Numerical Simulations ◽  
Dynamic Balance ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Phenomena

This study aimed to enhance the understanding of flow phenomena in low-reaction aspirated compressors. Three-dimensional, multi-passage steady and unsteady numerical simulations are performed to investigate the performance sensitivity to tip clearance variation on the first-stage rotor of a multistage low-reaction aspirated compressor. Three kinds of tip clearance sizes including 1.0τ, 2.0τ and 3.0τ are modeled, in which 1.0τ corresponds to the designed tip clearance size of 0.2 mm. The steady numerical simulations show that the overall performance of the rotor moves toward lower mass flow rate when the tip clearance size is increased. Moreover, energy losses, efficiency reduction and stall margin decrease are also observed with increasing tip clearance size. This can be mostly attributed to the damaging impact of intense tip clearance flow. For unsteady simulation, the result shows periodical oscillation of the tip leakage vortex and a “two-passage periodic structure” in the tip region at the near-stall point. The occurrence of the periodical oscillation is due to the severe interaction between the tip clearance flow and the shock wave. However, the rotor operating state is still stable at this working point because a dynamic balance is established between the tip clearance flow and incoming flow.

Numerical Investigation of Relation Between Unsteady Behavior of Tip Leakage Vortex and Rotating Disturbance in a Transonic Axial Compressor Rotor

2008 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
H. Sasaki
Keyword(s):  
Vortex Breakdown ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Rotating Instability

The purpose of this study is to have a better understanding of the unsteady behavior of tip clearance flow at near-stall condition from a multi-passage simulation and to clarify the relation between such unsteadiness and rotating disturbance. This study is motivated by the following concern. A single passage simulation has revealed the occurrence of the tip leakage vortex breakdown at near-stall condition in a transonic axial compressor rotor, leading to the unsteadiness of the tip clearance flow field in the rotor passage. These unsteady flow phenomena were similar to those in the rotating instability, which is classified in one of the rotating disturbances. In other words it is possible that the tip leakage vortex breakdown produces a rotating disturbance such as the rotating instability. Three-dimensional unsteady RANS calculation was conducted to simulate the rotating disturbance in a transonic axial compressor rotor (NASA Rotor 37). The four-passage simulation was performed so as to capture a short length scale disturbance like the rotating instability and the spike-type stall inception. The simulation demonstrated that the unsteadiness of tip leakage vortex, which was derived from the vortex breakdown at near-stall condition, invoked the rotating disturbance in the rotor, which is similar to the rotating instability.

Unsteady tip clearance flow pattern in an isolated axial compressor rotor with micro tip injection

2007 ◽  
Vol 16 (4) ◽  
pp. 309-320 ◽  
Author(s):  
Shaojuan Geng ◽  
Hongwu Zhang ◽  
Jingyi Chen ◽  
Weiguang Huang
Keyword(s):  
Flow Pattern ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Injection

Characteristics of Tip Clearance Flow Instability in a Transonic Compressor

2010 ◽  
Author(s):  
Chunill Hah ◽  
Melanie Voges ◽  
Martin Mueller ◽  
Heinz-Peter Schiffer
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Instability ◽  
Tip Clearance ◽  
Piv Measurements ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Clearance Vortex

In the present study, unsteady flow phenomena due to tip clearance flow instability in a modern transonic axial compressor rotor are studied in detail. First, unsteady flow characteristics due the oscillating tip clearance vortex measured with the particle image velocimetry (PIV) and casing-mounted unsteady pressure transducers are analyzed and compared to numerical results with a large eddy simulation (LES). Then, measured characteristic frequencies of the unsteady flow near stall operation are investigated. The overall purpose of the study is to advance the current understanding of the unsteady flow field near the blade tip in an axial transonic compressor rotor near the stall operating condition. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. The currently applied PIV measurements indicate that the flow near the tip region is unsteady even at the design condition. This self-induced unsteadiness increases significantly as the compressor operates toward the stall condition. PIV data show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The spectral analysis of measured end wall and blade surface pressure shows that there are two dominant frequencies near stall. One frequency is about 40–60% of the rotor rotation and the other dominant frequency is about 40–60% of the blade passing frequency (BPF). The first frequency represents the movement of a large blockage over several consecutive blade passages against the rotor rotation. The second frequency represents traditional tip flow instability, which has been widely observed in subsonic compressors. The LES simulations show that the second frequency is due to movement of the instability vortex.

Experimental Investigation on Tip Clearance Flow of Compressor Cascade With Blade Tip Winglet

2012 ◽  
Author(s):  
Shaobing Han ◽  
Jingjun Zhong ◽  
Huawei Lu ◽  
Xiaoxu Kan ◽  
Haiyang Gao
Keyword(s):  
Flow Field ◽  
Passive Control ◽  
Control Strategies ◽  
Suction Side ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip

This paper presents the results of experimental research of flow in an axial compressor cascade with different types of winglet on the blade tip, which consists of a suction-side winglet, pressure-side winglet and the combined winglet. The detailed tip leakage flow field with different winglet was described with total pressure loss coefficient, secondary streamline and axial vorticity on the cascade exit flow field. The mechanisms of the three passive control methods were illuminated. The result indicated that the tip clearance flow strengths could be reduced in all the three control strategies. The compressor aerodynamic performance could be improved via the addition of tip winglets. The suction-side winglet had the best effect on the cascade flow field, and the strength of leakage vortex and the associated mixture losses were reduced.

scholarly journals Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor

1996 ◽  
Vol 118 (2) ◽  
pp. 218-229 ◽  
Author(s):  
K. L. Suder ◽  
M. L. Celestina
Keyword(s):  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Peak Efficiency ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor ◽  
Design Speed

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part-speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100 percent design speed and at near peak efficiency at 60 percent design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only five times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the end-wall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part-speed conditions is also discussed.

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.

3D Laser Transit Measurements of the Tip Clearance Vortex in a Compressor Rotor Blade Row

1996 ◽  
Author(s):  
Andrew C. Foley ◽  
Paul C. Ivey
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Tip Clearance ◽  
Measured Velocity ◽  
Tip Clearance Flow ◽  
Pressure Losses ◽  
Compressor Rotor ◽  
Blade Row ◽  
Clearance Flow ◽  
Tip Clearance Vortex

This paper describes the structure of the tip clearance flow in a low speed isolated compressor rotor. Pneumatic cobra probes are radially traversed upstream and downstream of the blade row and the time averaged total pressure losses across the blade row calculated. The increase in pressure losses due to the tip clearance flow is clearly seen. The nature of the tip losses is investigated further using a unique 3D laser transit anemometer to measure velocities and turbulence levels. A 3D representation of the resulting flow field is then constructed using the experimentally measured velocity vectors. With the aid of ‘stream particles’ released into this flow field a vortex structure is then visualised. A section through the path of this vortex assists in showing its development through the blade row. Due to the co-location of this vortex and the total pressure losses in the passage, it is this vortex which is believed to be responsible for the excess total pressure losses in the tip region.

On Improving the Surge Margin of a Tip-Critical Axial Compressor Rotor

2017 ◽  
Author(s):  
Marcus Lejon ◽  
Tomas Grönstedt ◽  
Niklas Andersson ◽  
Lars Ellbrant ◽  
Hans Mårtensson
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Incoming Flow ◽  
Objective Functions ◽  
Blade Loading ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Surge Margin ◽  
Clearance Flow

Delaying breakdown of the flow in the tip region of a tip-critical compressor rotor as long as possible, i.e. improving the surge margin, is of great interest to the turbomachinery community and is the focus of this study. The surge margin of ten compressor rotors is evaluated numerically, each with different blade loading and geometry at the tip. Previous work in the field has shown the dependence of an interface in the tip region of a compressor rotor between the incoming flow and the tip clearance flow with the passage flow coefficient ϕ. Previous work in the field has also shown that a higher incoming meridional momentum in the tip region can be beneficial to the surge margin of a tip-critical rotor. The present study generalizes these findings by taking into account the local blade loading of the rotor tip section and the level of loss in the tip region. The surge margin is found to improve if the blade loading of the rotor tip section is increased, which acts to increase the incoming mass flow rate and improve the surge margin provided that an increase in loss, mainly related to the strength and direction of the tip clearance flow, does not negate the effect as the compressor is throttled. Two quantities are proposed as objective functions to be used for optimization to achieve a compressor rotor with high surge margin based on the flow field at the design point. Finally, an optimization and analysis of the results is made to demonstrate the proposed objective functions in practise.

3-D Digital PIV Measurements of the Tip Clearance Flow in an Axial Compressor

2002 ◽  
Author(s):  
Mark P. Wernet ◽  
Dale Van Zante ◽  
Tony J. Strazisar ◽  
W. Trevor John ◽  
P. Susan Prahst
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Image Velocimetry ◽  
Clearance Flow ◽  
Compressor Performance ◽  
Tip Clearance Vortex

The accurate characterization and simulation of rotor tip clearance flows has received much attention in recent years due to their impact on compressor-performance and stability. At NASA Glenn the first known three dimensional Digital Particle Image Velocimetry (DPIV) measurements of the tip region of a low speed compressor rotor have been acquired to characterize the behavior of the rotor tip clearance flow. The measurements were acquired phase-locked to the rotor position so that changes in the tip clearance vortex position relative to the rotor blade can be seen. The DPIV technique allows the magnitude and relative contributions of both the asynchronous motions of a coherent structure and the temporal unsteadiness to be evaluated. Comparison of measurements taken at the peak efficiency and at near stall operating conditions characterizes the mean position of the clearance vortex and the changes in the unsteady behavior of the vortex with blade loading. Comparisons of the 3-D DPIV measurements at the compressor design point to a 3D steady N-S solution are also done to assess the fidelity of steady, single-passage simulations to model an unsteady flow field.

Sign in / Sign up

Export Citation Format

Share Document