Investigation of the Tip Clearance Flow Inside and at the Exit of a Compressor Rotor Passage—Part I: Mean Velocity Field

1983 ◽  
Vol 105 (1) ◽  
pp. 1-12 ◽  
Author(s):  
A. Pandya ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Tip Clearance ◽  
Mean Flow ◽  
Ensemble Averaging ◽  
Mean Velocity ◽  
Tip Clearance Flow ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Wall Boundary ◽  
Clearance Flow

This paper reports on an experimental study of the nature of the tip clearance flow in a moderately loaded compressor rotor. The measurements reported were obtained using a stationary two-sensor, hot-wire probe in combination with an ensemble averaging technique. The flow field was surveyed at various radial locations and at ten axial locations, four of which were inside the blade passage in the clearance region and the remaining six outside the passage. Variations of the mean flow properties in the tangential and the radial directions at various axial locations were derived from the data. Variation of leakage velocity at different axial stations and the annulus-wall boundary layer profiles from passage-averaged mean velocities were also estimated. The results indicate that there exists a region of strong interaction of the leakage flow with the annulus-wall boundary layer at half-chord. The profiles are well-behaved beyond this point. The rotor exit flow is found to be uniform beyond 3/4 blade chord downstream of the rotor trailing edge.

Investigation of the Tip Clearance Flow Inside and at the Exit of a Compressor Rotor Passage—Part II: Turbulence Properties

1983 ◽  
Vol 105 (1) ◽  
pp. 13-17 ◽  
Author(s):  
A. Pandya ◽  
B. Lakshminarayana
Keyword(s):  
Tip Clearance ◽  
Leakage Flow ◽  
Ensemble Averaging ◽  
Tip Clearance Flow ◽  
Wire Probe ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
High Turbulence ◽  
Very High

The flow in the tip clearance region of a compressor rotor is highly turbulent due to the strong interaction of the leakage flow with the annulus wall boundary layer. This paper deals with the turbulence properties of the flow in the tip clearance region of a moderately loaded compressor rotor. The experimental results reported in this paper were obtained using a two-sensor hot-wire probe in combination with an ensemble averaging technique. Blade-to-blade distribution of the axial and tangential turbulence intensities at various radial locations and ten axial locations (four inside the blade passage and the remaining six outside the passage) were derived from this data. Isointensity contours in the clearance region at various radial locations were also obtained from the experimental data. A region of very high turbulence intensities was indicated at the half-chord location from these results. The turbulence intensity profiles also indicated that the leakage flow travels toward the midpassage before rolling up. The turbulence is almost isotropic beyond three-quarter chord downstream of the trailing edge.

Vortex Dynamics and Mechanisms for Viscous Losses in the Tip-Clearance Flow

2005 ◽  
Author(s):  
Donghyun You ◽  
Meng Wang ◽  
Parviz Moin ◽  
Rajat Mittal
Keyword(s):  
Tip Clearance ◽  
Wall Region ◽  
Mean Flow ◽  
Mean Velocity ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Viscous Losses ◽  
Clearance Flow ◽  
End Wall

The tip-clearance flow in axial turbomachines is studied using large-eddy simulation with particular emphasis on understanding the underlying mechanisms for viscous losses in the end-wall region and the unsteady characteristics of the tip-leakage vortical structures. Systematic and detailed analysis of the mean flow field and turbulence statistics has been made in a linear cascade with a moving end-wall. The tip-leakage jet and tip-leakage vortex are found to produce significant mean velocity gradients, leading to the production of vorticity and turbulent kinetic energy. These are the major causes for viscous losses in the cascade end-wall region. An analysis of the energy spectra and space-time correlations of the velocity fluctuations suggests that the tip-leakage vortex is subject to a pitchwise low frequency wandering motion.

Casing Wall Boundary-Layer Development Through an Isolated Compressor Rotor

1982 ◽  
Vol 104 (4) ◽  
pp. 805-817 ◽  
Author(s):  
I. H. Hunter ◽  
N. A. Cumpsty
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Outer Wall ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Wall Boundary ◽  
Boundary Layer Development ◽  
Layer Development

Detailed measurements were made of the casing wall boundary layer development across a large-scale, low-speed axial compressor rotor blade row. An important feature of the work was the use of blading which allowed the tip clearance to be varied. A conventional pressure probe was used to obtain time-averaged measurements of the outer-wall boundary layer downstream of the rotor whilst a hot-wire anenometry technique yielded the three-dimensional, blade to blade structure of the flow. The downstream boundary layer was found to thicken as the rotor loading and blade-end clearance were increased, with fluid tending to accumulate towards the pressure side of the passage. By its pronounced effects upon wall boundary layer development, tip clearance had a deleterious effect upon the performance of the compressor.

The Behavior of Tip Clearance Flow at Near-Stall Condition in a Transonic Axial Compressor Rotor

2007 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
M. Furukawa
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Compressor ◽  
Boundary Layer Separation ◽  
Tip Clearance ◽  
Suction Surface ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Transonic Axial Compressor

It is known that the tip clearance flow is dominant and very important flow phenomena in axial compressor aerodynamics because the tip clearance flow has a great influence on the stability as well as aerodynamic loss of compressors. Our goal is to clarify the behavior of tip clearance flow at near-stall condition in a transonic axial compressor rotor (NASA Rotor 37). In the present work, steady and unsteady RANS simulations were performed to investigate vortical flow structures and separated flow field near the tip for several different clearance cases. Boundary layer separation on the casing wall and blade suction surface was investigated in detail for near-stall and stall condition. In order to understand such complicated flow field, vortex cores were identified using the critical point theory and a topology of the three-dimensional separated and vortical flows was analyzed. In the nominal clearance case, the breakdown of tip leakage vortex has occurred at a near-stall operating condition because of the interaction of the vortex with the shock wave, leading to a large blockage and unsteadiness in the rotor tip. On the other hand, the calculation with no clearance suggested that the separation on the suction surface was different from that with the nominal clearance. Since the shock wave induced the boundary layer separation on the blade suction surface in the transonic axial compressor rotor, focal-type critical points appeared on the suction surface near the tip at near-stall condition.

Three-Dimensional Flow Field in the Tip Region of a Compressor Rotor Passage—Part I: Mean Velocity Profiles and Annulus Wall Boundary Layer

1982 ◽  
Vol 104 (4) ◽  
pp. 760-771 ◽  
Author(s):  
B. Lakshminarayana ◽  
M. Pouagare ◽  
R. Davino
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Three Dimensional ◽  
Leading Edge ◽  
Leakage Flow ◽  
Suction Surface ◽  
Mean Velocity ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Wall Boundary

The flow field in the annulus wall and tip region of a compressor rotor was measured using a triaxial, hot-wire probe rotating with the rotor. The flow was surveyed across the entire passage at five axial locations (leading edge, 1/4 chord, 1/2 chord, 3/4 chord, and trailing edge locations) and at six radial locations inside the passage. The data derived include all three components of mean velocity. Blade-to-blade variations of the velocity components, pitch and yaw angles, as well as the passage-averaged mean properties of the annulus wall boundary layer, are derived from this data. The measurements indicate that the leakage flow starts beyond a quarter-chord and tends to roll up farther away from the suction surface than that observed in cascades. Substantial velocity deficiencies and radial inward velocities are observed in this region. The annulus wall boundary layer is well behaved up to half a chord, beyond which interactions with the leakage flow produce complex profiles.

Role of Tip-Leakage Vortices and Passage Shock in Stall Inception in a Swept Transonic Compressor Rotor

2004 ◽  
Author(s):  
Chunill Hah ◽  
Douglas C. Rabe ◽  
Aspi R. Wadia
Keyword(s):  
Boundary Layer ◽  
Flow Fields ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Clearance Vortex

The current paper reports on investigations aimed at advancing the understanding of the flow field near the casing of a forward-swept transonic compressor rotor. The role of tip clearance flow and its interaction with the passage shock on stall inception are analyzed in detail. Steady and unsteady three-dimensional viscous flow calculations are applied to obtain flow fields at various operating conditions. The numerical results are first compared with available measured data. Then, the numerically obtained flow fields are interrogated to identify the roles of flow interactions between the tip clearance flow, the passage shock, and the blade/endwall boundary layers. In addition to the flow field with nominal tip clearance, two more flow fields are analyzed in order to identify the mechanisms of blockage generation: one with zero tip clearance, and one with nominal tip clearance on the forward portion of the blade and zero clearance on the aft portion. The current study shows that the tip clearance vortex does not break down, even when the rotor operates in a stalled condition. Interaction between the shock and the suction surface boundary layer causes the shock, and therefore the tip clearance vortex, to oscillate. However, for the currently investigated transonic compressor rotor, so-called breakdown of the tip clearance vortex does not occur during stall inception. The tip clearance vortex originates near the leading edge tip, but moves downward in the spanwise direction inside the blade passage. A low momentum region develops above the tip clearance vortex from flow originating from the casing boundary layer. The low momentum area builds up immediately downstream of the passage shock and above the core vortex. This area migrates toward the pressure side of the blade passage as the flow rate is decreased. The low momentum area prevents incoming flow from passing through the pressure side of the passage and initiates stall inception. It is well known that inviscid effects dominate tip clearance flow. However, complex viscous flow structures develop inside the casing boundary layer at operating conditions near stall.

Tip Clearance Flow in a Compressor Rotor Passage at Design and Off-Design Conditions

1984 ◽  
Vol 106 (3) ◽  
pp. 570-577 ◽  
Author(s):  
B. Lakshminarayana ◽  
A. Pandya
Keyword(s):  
Tip Clearance ◽  
Velocity Data ◽  
Hot Wire ◽  
Pressure Data ◽  
Ensemble Averaging ◽  
Blade Loading ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Flow Parameters ◽  
Clearance Flow

The flow field in the tip clearance region of a compressor rotor at an off-design condition is reported in this paper. The earlier data at the design condition have also been reinterpreted and correlated with the blade and the flow parameters. The measurements inside the rotor tip region are acquired using a miniature hot-wire sensor of “V” configuration. The instantaneous velocity data are analyzed by the ensemble-averaging technique to derive the blade-to-blade velocity field at various axial and radial locations between the rotor tip and the casing. The flow and the blade pressure data at the design condition are compared with the data at the off-design condition (lower blade loading). In addition to a reduction in the leakage velocities, its chordwise variation is also altered substantially at the lower blade loading.

Effects of the Inlet Flow Conditions on the Tip Clearance Flow of an Isolated Compressor Rotor

2002 ◽  
Author(s):  
Holger Brandt ◽  
Leonhard Fottner ◽  
Horst Saathoff ◽  
Udo Stark
Keyword(s):  
Boundary Layer ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Inlet Flow ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Numerical Predictions ◽  
Clearance Flow ◽  
Inflow Conditions

Numerical investigations on the effects of varying inflow conditions on the tip leakage flow field of an isolated low–speed compressor rotor and the respective rotor tip section cascade were performed at corresponding operation points. Inlet flow variations at each flow rate were obtained by means of varying the boundary layer thickness in such a manner that the non-dimensional integral parameters of the simulated inflow boundary layers were identical for the rotor and cascade. In order to describe the flowfield through the tip gap and its interactions with the incoming flow accurately, a fully–gridded tip gap region was employed. The numerical predictions for comparable inflow conditions agree well with experimental results from previous investigations on the endwall boundary layer separation due to tip clearance flow. It is demonstrated by the simulations that thickening the inflow boundary layer forces the roll-up point of the clearance vortex to move towards the leading edge. By its effects upon leakage flow, varying the incoming boundary layer has a deleterious effect on stall mass flow similar to increasing the tip clearance height. The investigations further reveal a great deal of similarity between the steady state clearance flow in the cascade and the rotor overtip leakage flow.

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.

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