Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part I — Experimental Investigations

2014 ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analysed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. Part I of this two-part paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-PIV measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andreas Krug ◽  
Peter Busse ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Experimental Studies ◽  
Axial Compressor ◽  
Field Measurements ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Unsteady Interaction ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part II — Numerical Investigations

2014 ◽  
Author(s):  
Peter Busse ◽  
Andreas Krug ◽  
Konrad Vogeler
Keyword(s):  
Steady State ◽  
Flow Field ◽  
Initial Conditions ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Vortex Interaction ◽  
Compressor Cascade ◽  
Flow Phenomena ◽  
Tip Clearance Vortex ◽  
The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. Part II of this two-part paper focuses on the numerical studies conducted with the scientific flow solver TRACE. Selected measurements, which are discussed in detail in the first part of this paper, are compared with steady state RANS simulation data to determine the validity of the computational model. For this purpose, the flow field obtained in the passage (PIV), at the cascade exit (five-hole probes) and the endwall pressure distributions were used. The presented numerical results show potentials and limitations of the steady state CFD for the prediction of the investigated flow phenomena. The computations provide the initial conditions for future unsteady calculations, and enable a separate depiction of potential effects of steady and unsteady wake-tip clearance vortex interaction.

Investigation of Tip Clearance Phenomena in an Axial Compressor Cascade Using Euler and Navier–Stokes Procedures

1993 ◽  
Vol 115 (3) ◽  
pp. 453-467 ◽  
Author(s):  
R. F. Kunz ◽  
B. Lakshminarayana ◽  
A. H. Basson
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Numerical Procedure ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Flow Angle ◽  
Physical Phenomena

Three-dimensional Euler and full Navier–Stokes computational procedures have been utilized to simulate the flow field in an axial compressor cascade with tip clearance. An embedded H-grid topology was utilized to resolve the flow physics in the tip gap region. The numerical procedure employed is a finite difference Runge-Kutta scheme. Available measurements of blade static pressure distributions along the blade span, dynamic pressure and flow angle in the cascade outlet region, and spanwise distributions of blade normal force coefficient and circumferentially averaged flow angle are used for comparison. Several parameters that were varied in the experimental investigations were also varied in the computational studies. Specifically, measurements were taken and computations were performed on the configuration with and without: tip clearance, the presence of an endwall, inlet endwall total pressure profiles and simulated relative casing rotation. Additionally, both Euler and Navier–Stokes computations were performed to investigate the relative performance of these approaches in reconciling the physical phenomena considered. Results indicate that the Navier–Stokes procedure, which utilizes a low Reynolds number k–ε model, captures a variety of important physical phenomena associated with tip clearance flows with good accuracy. These include tip vortex strength and trajectory, blade loading near the tip, the interaction of the tip clearance flow with passage secondary flow, and the effects of relative endwall motion. The Euler computation provides good but somewhat diminished accuracy in resolution of some of these clearance phenomena. It is concluded that the level of modeling embodied in the present approach is sufficient to extract much of the tip region flow field information useful to designers of turbomachinery.

scholarly journals Investigation of Tip Clearance Phenomena in an Axial Compressor Cascade Using Euler and Navier-Stokes Procedures

1992 ◽  
Author(s):  
R. F. Kunz ◽  
B. Lakshminarayana ◽  
A. H. Basson
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Numerical Procedure ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Flow Angle ◽  
Physical Phenomena

Three-dimensional Euler and Full Navier-Stokes computational procedures have been utilized to simulate the flow field in an axial compressor cascade with tip clearance. An embedded H-grid topology was utilized to resolve the flow physics in the tip gap region. The numerical procedure employed is a finite difference Runge-Kutta scheme. Available measurements of blade static pressure distributions along the blade span, dynamic pressure and flow angle in the cascade outlet region, and spanwise distributions of blade normal force coefficient and circumferentially averaged flow angle are used for comparison. Several parameters which were varied in the experimental investigations were also varied in the computational studies. Specifically, measurements were taken and computations were performed on the configuration with and without: tip clearance, the presence of an endwall, inlet endwall total pressure profiles and simulated relative casing rotation. Additionally, both Euler and Navier-Stokes computations were performed to investigate the relative performance of these approaches in reconciling the physical phenomena considered. Results indicate that the Navier-Stokes procedure, which utilizes a low Reynolds number k-ε model, captures a variety of important physical phenomena associated with tip clearance flows with good accuracy. These include tip vortex strength and trajectory, blade loading near the tip, the interaction of the tip clearance flow with passage secondary flow and the effects of relative endwall motion. The Euler computation provides good but somewhat diminished accuracy in resolution of some of these clearance phenomena. It is concluded that the level of modelling embodied in the present approach is sufficient to extract much of the tip region flow field information useful to designers of turbomachinery.

Experimental Investigations on the Efficiency of Active Flow Control in a Compressor Cascade With Periodic Non-Steady Outflow Conditions

2017 ◽  
Author(s):  
Marcel Staats ◽  
Wolfgang Nitsche
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Flow Separation ◽  
Active Flow Control ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Steady Regime ◽  
Stator Blade ◽  
Active Flow ◽  
The Impact

We present results of experiments on a periodically unsteady compressor stator flow of the type which would be expected in consequence of pulsed combustion. A Reynolds number of Re = 600000 was used for the investigations. The experiments were conducted on the two-dimensional low-speed compressor testing facility in Berlin. A choking device downstream the trailing edges induced a periodic non-steady outflow condition to each stator vane which simulated the impact of a pressure gaining combuster downstream from the last stator. The Strouhal number of the periodic disturbance was Sr = 0.03 w.r.t. the stator chord length. Due to the periodic non-steady outflow condition, the flow-field suffers from periodic flow separation phenomena, which were managed by means of active flow control. In our case, active control of the corner separation was applied using fluidic actuators based on the principle of fluidic amplification. The flow separation on the centre region of the stator blade was suppressed by means of a fluidic blade actuator leading to an overall time-averaged loss reduction of 11.5%, increasing the static pressure recovery by 6.8% while operating in the non-steady regime. Pressure measurements on the stator blade and the wake as well as PIV data proved the beneficial effect of the active flow control application to the flow field and the improvement of the compressor characteristics. The actuation efficiency was evaluated by two figures of merit introduced in this contribution.

Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part II — Wake–Tip Clearance Vortex Interaction

2007 ◽  
Author(s):  
Ronald Mailach ◽  
Ingolf Lehmann ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Pressure Sensors ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Lower Velocity ◽  
Blade Row ◽  
Blade Tip ◽  
Tip Clearance Vortex

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part II of the paper the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes the tip clearance vortices are separated into different segments. Along the mean vortex trajectory these parts can be characterised by alternating patches of higher and lower velocity and flow turning or subsequent counterrotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

Unsteady behaviour of the tip clearance vortex in a rotor equivalent compressor cascade

2009 ◽  
Vol 223 (6) ◽  
pp. 635-643 ◽  
Author(s):  
H Schrapp ◽  
U Stark ◽  
H Saathoff
Keyword(s):  
Vortex Breakdown ◽  
Axial Flow ◽  
Stability Limit ◽  
Single Stage ◽  
Tip Clearance ◽  
Measuring System ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Experimental Proof ◽  
Tip Clearance Vortex

From earlier experimental investigations in a single-stage axial-flow pump and different numerical calculations of the flow in single-stage axial-flow compressors, it is known that vortex breakdown of the tip clearance vortex can take place in turbomachines, although an experimental proof for subsonic compressors is lacking. Vortex breakdown, if existent, is a source of high instability in the sensitive tip region of axial-flow pumps and compressors and will also play an important role in the stall inception process. Therefore, the flow in a linear compressor cascade with a 3 per cent tip clearance to one side has been investigated at different flow angles from the design point up to the stability limit of the cascade. The cascade resembles the tip section of a single-stage, axial-flow, low-speed compressor that is also in use at the Technical University of Braunschweig. The measuring techniques used were (a) a commercial particle image velocimetry (PIV) system and (b) a pressure measuring system with several flush mounted high-response pressure transducers at selected locations where the vortex was expected. As the cascade approaches its stall limit, the analysis of the pressure signals in the frequency domain revealed a bump of increased amplitude at a certain non-dimensional frequency for some of the measuring positions. The measuring positions that exhibited the bump correlated very well with a paraboloid-shaped region of high standard deviation enveloping an area of very low momentum fluid. It is shown that the frequency of the striking bump corresponds to the rotational frequency of the vortex calculated from the PIV measurements.

Periodic Unsteadiness of Compressor Tip Clearance Vortex

2004 ◽  
Author(s):  
Jinwoo Bae ◽  
Kenneth S. Breuer ◽  
Choon S. Tan
Keyword(s):  
Tip Clearance ◽  
Mixing Enhancement ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Reduced Frequency ◽  
Instability Theory ◽  
Forced Responses ◽  
Linear Compressor Cascade ◽  
Tip Clearance Vortex ◽  
Flow Blockage

Natural and forced responses of the tip clearance vortex are measured in a linear compressor cascade to characterize periodic unsteadiness of the tip clearance vortex. There exists a natural frequency at which the tip clearance vortex is the most receptive to external forcing, thus resulting in mixing enhancement and flow blockage reduction. A physical explanation of the source of the observed periodic unsteadiness is suggested based on the trailing vortex instability theory. Observations of the time scale for the unsteadiness from different compressor geometries and flow conditions are shown to scale with a reduced frequency based on convective time through the blade passage.

An Analysis of the Secondary Flow Around a Tandem Blade Under the Presence of a Tip Gap in a High-Speed Linear Compressor Cascade

2021 ◽  
pp. 1-20
Author(s):  
Liesbeth Konrath ◽  
Dieter Peitsch ◽  
Alexander Heinrich
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Complex Flow ◽  
Flow Topology ◽  
Linear Compressor ◽  
Near Surface ◽  
Oil Flow ◽  
Linear Compressor Cascade

Abstract Tandem blades have often been under investigation, experimentally as well as numerically, but most studies have been about tandem blade stators without tip gap. This work analyzes the influence of a tip gap on the flow field of a tandem blade for engine core compressors. Experiments have been conducted in a high-speed linear compressor cascade on a tandem and a reference geometry. The flow is analyzed using five-hole probe measurements in the wake of the blades and oil flow visualization to show the near surface stream lines. First, the results for design conditions (tandem and conventional blade) are compared to measurements on corresponding blades without tip gap. Similarities and differences in the flow topology due to the tip clearance are analyzed, showing that the introduction of the tip clearance has a similar influence on the loss and turning development for the tandem and the conventional blade. The tandem blade features two tip clearance vortices with a complex flow interaction and the possible formation of a third counter-rotating vortex between them. An incidence variation from 0deg to 5deg for both blades indicates at first a similar behavior. After a separation of the flow field into gap and non-gap half it becomes apparent that the tandem blade shows higher losses on the gap side, while featuring a close-to-constant behavior on the non-gap side. Further investigation of the flow on the gap side shows indicators of the front blade exhibiting tip clearance vortex break down.

Measurements of the 3D Flow Field Downstream of an Aircraft Engine Fan

2014 ◽  
Author(s):  
Herwart T. Hönen ◽  
Christian Werner-Spatz ◽  
Angela Giebmanns ◽  
Guido Döbbener ◽  
Peter Jeschke
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Aircraft Engine ◽  
Sensitivity Study ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Jet Engine ◽  
3D Information ◽  
Operating Points

Flow field measurements have been performed in a jet engine fan. As a part of a sensitivity study on the influence of geometry changes on the performance of the compressor the experiments provide a data base for the verification of extensive numerical simulations covering the fan blades. These investigations help to improve the understanding of how changes in component geometry due to wear affect the engine. The experimental investigations were carried out down-stream of the fan of a jet engine on the test cell at Lufthansa Technik AG. The main focus of the measurements was to provide highly resolved flow field data downstream of the OGV. A pneumatic five-hole probe was applied in order to obtain 3D information of the flow properties. In order to detect and to resolve the wakes of the OGVs and of the midspan shrouds of the rotor blades the measurements had to be performed along the blade height and had to cover more than one OGV spacing. Therefore, it was necessary to position the probe at various radial and circumferential locations. The radial positioning of the probe was performed by a standard traversing unit. The different circumferential locations were achieved by a specially developed traversing mechanism on a modified engine fan case, which allowed a continuous positioning in the range of two OGV spacings. The experiments were carried out for two different operating points of the jet engine. For each of these operating points, the engine was operated with nominal and with increased tip clearance above the fan rotor in order to simulate different wear conditions. The paper explains the necessary modifications to the jet engine and the set up for the experiments. Furthermore, measured results are shown and compared to the results derived from the CFD simulations which were performed prior to the experimental investigations.

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