scholarly journals Experimental Study of a 3D Wake Decay and Secondary Flows Behind a Rotor Blade Row of a Low Speed Compressor Stage

1996 ◽  
Author(s):  
A. S. Witkowski ◽  
T. J. Chmielniak ◽  
M. D. Strozik
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Compressor Stage ◽  
Blade Row

Detailed measurements have been performed in a low pressure axial flow compressor stage to investigate the structure of the secondary flow field and the three-dimensional wake decay at different axial locations before and behind the rotor. The three dimensional flow field upstream and downstream of the rotor and on the centerline of the stator blade passage have been sampled periodically using a straight and a 90 degree triple-split fiber probe. Radial measurements at 39 radial stations were carried out at chosen axial positions in order to get the span-wise characteristics of the unsteady flow. Taking the experimental values of the unsteady flow velocities and turbulence properties, the effects of the rotor blade wake decay and secondary flow on the blade row spacing and stator passage flow at different operating conditions are discussed. For the normal operating point, the component of radial turbulent intensities in the leakage-flow mixing region is found to be much higher than the corresponding axial and tangential components. But for a higher value of the flow coefficient the relations are different.The results of the experiments show that triple-split fiber probes, straight and 90 degree measurements, combined with the ensemble average technique are a very useful method for the analysis of rotor flow in turbomachinery. Tip clearance vortex, secondary flow near the hub and radial flow in the wake, turbulent intensity and Reynolds stresses and also the decay of the rotor wakes can be obtained by this method.

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.

Three-Dimensional-Flow Theories for Axial Compressors and Turbines

1948 ◽  
Vol 159 (1) ◽  
pp. 255-268 ◽  
Author(s):  
A. D. S. Carter
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Physical Nature ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Three Dimensional Flow ◽  
Axial Compressors ◽  
Dimensional Flow ◽  
Blade Row

It has long been known that the energy losses occurring in an axial compressor or turbine cannot be fully accounted for by the skin-friction losses on the blades and annulus walls. The difference, usually termed secondary loss, is attributed to miscellaneous secondary flows which take place in the blade row. These flows both cause losses in themselves and modify the operating conditions of the individual blade sections, to the detriment of the overall performance. This lecture analyses the three-dimensional flow in axial compressors and turbines, so that, by appreciation of the factors involved, possible methods of improving the performance can readily be investigated. The origin of secondary flow is first examined for the simple case of a straight cascade. The physical nature of the flow, and theories which enable quantitative estimates to be made, are discussed at some length. Following this, the three-dimensional flow in an annulus with a stationary blade row is examined, and, among other things, the influence of radial equilibrium on the flow pattern is noted. All physical restrictions are then removed, and the major factors governing the three-dimensional flow in an actual machine are investigated as far as is possible with existing information, particular attention being paid to the influence of a non-uniform velocity profile, tip clearance, shrouding, and boundary layer displacement. Finally the various empirical factors used in design are discussed, and the relationships between them established.

Time Accurate Euler Simulation of Interaction of Nozzle Wake and Secondary Flow With Rotor Blade in an Axial Turbine Stage Using Nonreflecting Boundary Conditions

1995 ◽  
Author(s):  
S. Fan ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Computational Domain ◽  
Turbine Stage ◽  
Axial Turbine ◽  
Unsteady Pressure

The objective of this paper is to investigate the three dimensional unsteady flow interactions in a turbomachine stage. A three-dimensional time accurate Euler code has been developed using an explicit four-stage Runge-Kutta scheme. Three-dimensional unsteady non-reflecting boundary conditions are formulated at the inlet and at the outlet of the computational domain to remove the spurious numerical reflections. The three-dimensional code is first validated for 2-D and 3-D cascades with harmonic vortical inlet distortions. The effectiveness of non reflecting boundary conditions is demonstrated. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through rotor and the resulting unsteady pressure field in an axial turbine stage. The three dimensional and time dependent propagation of nozzle wakes in the rotor blade row and the effects of nozzle secondary flow on the rotor unsteady surface pressure and passage flow field are studied. It was found that the unsteady flow field in the rotor is highly three-dimensional and the nozzle secondary flow has significant contribution to the unsteady pressure on the blade surfaces. Even though the steady flow at the midspan is nearly two-dimensional, the unsteady flow is 3-D and the unsteady pressure distribution can not by predicted by a 2-D analysis.

scholarly journals Endwall and Unsteady Flow Phenomena in an Axial Turbine Stage

1994 ◽  
Author(s):  
H. E. Gallus ◽  
J. Zeschky ◽  
C. Hah
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Radial Distribution ◽  
Three Dimensional ◽  
Hot Wire ◽  
Turbine Stage ◽  
Flow Properties ◽  
Blade Row ◽  
Secondary Flow Field

Detailed experimental and numerical studies have been performed in a subsonic, axial-flow turbine stage to investigate the secondary flow field, the aerodynamic loss generation, and the spanwise mixing under a stage environment. The experimental study includes measurements of the static pressure distribution on the rotor blade surface and the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The rotor exit flow field was measured with an unsteady hot-wire probe which has high temporal and spatial resolution. Both steady and unsteady numerical analyses were performed with a three-dimensional Navier-Stokes code for the multiple blade rows. Special attention was focused on how well the steady multiple-blade-row calculation predicts the rotor exit flow field and how much the blade interaction affects the radial distribution of flow properties at the stage exit. Detailed comparisons between the measurement and the steady calculation indicate that the steady multiple-blade-row calculation predicts the overall time-averaged flow field very well. However, the steady calculation does not predict the secondary flow at the stage exit accurately. The current study indicates that the passage vortex near the hub of the rotor is transported toward the mid-span due to the blade interaction effects. And, the structure of the secondary flow field at the exit of the rotor is significantly modified by the unsteady effects. The time-averaged secondary flow field and the radial distribution of the flow properties, which are uses for the design of the following stage, can be predicted more accurately with the unsteady flow calculation.

Endwall and Unsteady Flow Phenomena in an Axial Turbine Stage

1995 ◽  
Vol 117 (4) ◽  
pp. 562-570 ◽  
Author(s):  
H. E. Gallus ◽  
J. Zeschky ◽  
C. Hah
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Radial Distribution ◽  
Three Dimensional ◽  
Hot Wire ◽  
Turbine Stage ◽  
Flow Properties ◽  
Blade Row ◽  
Secondary Flow Field

Detailed experimental and numerical studies have been performed in a subsonic, axial-flow turbine stage to investigate the secondary flow field, the aerodynamic loss generation, and the spanwise mixing under a stage environment. The experimental study includes measurements of the static pressure distribution on the rotor blade surface and the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The rotor exit flow field was measured with an unsteady hot-wire probe, which has high temporal and spatial resolution. Both steady and unsteady numerical analyses were performed with a three-dimensional Navier–Stokes code for the multiple blade rows. Special attention was focused on how well the steady multiple-blade-row calculation predicts the rotor exit flow field and how much the blade interaction affects the radial distribution of flow properties at the stage exit. Detailed comparisons between the measurement and the steady calculation indicate that the steady multiple-blade-row calculation predicts the overall time-averaged flow field very well. However, the steady calculation does not predict the secondary flow at the stage exit accurately. The current study indicates that the passage vortex near the hub of the rotor is transported toward the midspan due to the blade interaction effects. Also, the structure of the secondary flow field at the exit of the rotor is significantly modified by the unsteady effects. The time-averaged secondary flow field and the radial distribution of the flow properties, which are used for the design of the following stage, can be predicted more accurately with the unsteady flow calculation.

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

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Ronald Mailach ◽  
Ingolf Lehmann ◽  
Konrad Vogeler
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Laser Doppler Anemometry ◽  
Pressure Sensors ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
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 characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating 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.

Time-Accurate Euler Simulation of Interaction of Nozzle Wake and Secondary Flow With Rotor Blade in an Axial Turbine Stage Using Nonreflecting Boundary Conditions

1996 ◽  
Vol 118 (4) ◽  
pp. 663-678 ◽  
Author(s):  
S. Fan ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Turbine Stage ◽  
Unsteady Pressure ◽  
Nonreflecting Boundary Conditions

The objective of this paper is to investigate the three-dimensional unsteady flow interactions in a turbomachine stage. A three-dimensional time-accurate Euler code has been developed using an explicit four-stage Runge–Kutta scheme. Three-dimensional unsteady nonreflecting boundary conditions are formulated at the inlet and the outlet of the computational domain to remove the spurious numerical reflections. The three-dimensional code is first validated for two-dimensional and three-dimensional cascades with harmonic vortical inlet distortions. The effectiveness of the nonreflecting boundary conditions is demonstrated. The unsteady Euler solver is then used to simulate the propagation of nozzle wake and secondary flow through the rotor and the resulting unsteady pressure field in an axial turbine stage. The three-dimensional and time-dependent propagation of nozzle wakes in the rotor blade row and the effects of nozzle secondary flow on the rotor unsteady surface pressure and passage flow field are studied. It was found that the unsteady flow field in the rotor is highly three dimensional and the nozzle secondary flow has significant contribution to the unsteady pressure on the blade surfaces. Even though the steady flow at the midspan is nearly two dimensional, the unsteady flow is three dimensional and the unsteady pressure distribution cannot be predicted by a two-dimensional analysis.

scholarly journals Incidence Angle and Pitch-Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1992 ◽  
Author(s):  
A. Perdichizzi ◽  
V. Dossena
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Oil Flow ◽  
Secondary Velocity ◽  
Secondary Flow Field

This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 degrees, and for three pitch-chord ratios: s/c = 0.58,0.73,0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five hole probe in a plane located at 50% of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots show in detail how much the secondary flow field is modified both by incidence and cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch averaged loss and of the deviation angle, when incidence or pitch-chord ratio is varied.

Design Optimization of Profiled Endwall With Consideration of Cooling and Rim Seal Flow Effects

2016 ◽  
Author(s):  
Huimin Tang ◽  
Shuaiqiang Liu ◽  
Hualing Luo
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Great Influence ◽  
Optimization Procedure ◽  
Secondary Flows ◽  
High Pressure Turbine ◽  
Operation Condition ◽  
Turbine Performance

Profiled endwall is an effective method to improve aerodynamic performance of turbine. This approach has been widely studied in the past decade on many engines. When automatic design optimisation is considered, most of the researches are usually based on the assumption of a simplified simulation model without considering cooling and rim seal flows. However, many researchers find out that some of the benefits achieved by optimization procedure are lost when applying the high-fidelity geometry configuration. Previously, an optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM. This optimization procedure has been executed [12] to design profiled endwalls for a turbine cascade and a one-and-half stage axial turbine. Improvements of the turbine performance have been achieved. As the profiled endwall is applied to a high pressure turbine, the problems of cooling and rim seal flows should be addressed. In this work, the effects of rim seal flow and cooling on the flow field of two-stage high pressure turbine have been presented. Three optimization runs are performed to design the profiled endwall of Rotor-One with different optimization model to consider the effects of rim flow and cooling separately. It is found that the rim seal flow has a significant impact on the flow field. The cooling is able to change the operation condition greatly, but barely affects the secondary flow in the turbine. The influences of the profiled endwalls on the flow field in turbine and cavities have been analyzed in detail. A significant reduction of secondary flows and corresponding increase of performance are achieved when taking account of the rim flows into the optimization. The traditional optimization mechanism of profiled endwall is to reduce the cross passage gradient, which has great influence on the strength of the secondary flow. However, with considering the rim seal flows, the profiled endwall improves the turbine performance mainly by controlling the path of rim seal flow. Then the optimization procedure with consideration of rim seal flow has also been applied to the design of the profiled endwall for Stator Two.

Effects of Off-Design Operating Conditions on the Blade Row Interaction in a HP Turbine Stage

2007 ◽  
Author(s):  
G. Persico ◽  
P. Gaetani ◽  
C. Osnaghi
Keyword(s):  
Flow Field ◽  
Strong Dependence ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Turbine Stage ◽  
Mixing Rate ◽  
Aerodynamic Pressure ◽  
Blade Row ◽  
Blade Row Interaction

An extensive experimental analysis on the subject of the unsteady periodic flow in a highly subsonic HP turbine stage has been carried out at the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano (Italy). In this paper the blade row interaction is progressively enforced by increasing the stator and rotor blade loading and by reducing the stator-rotor axial gap from 100% (very large to smooth the rotor inlet unsteadiness) to 35% (design configuration) of the stator axial chord. The time-averaged three-dimensional flow field in the stator-rotor gap was investigated by means of a conventional five-hole probe for the nominal (0°) and an highly positive (+22°) stator incidences. The evolution of the viscous flow structures downstream of the stator is presented to characterize the rotor incoming flow. The blade row interaction was evaluated on the basis of unsteady aerodynamic measurements at the rotor exit, performed with a fast-response aerodynamic pressure probe. Results show a strong dependence of the time-averaged and phase-resolved flow field and of the stage performance on the stator incidence. The structure of the vortex-blade interaction changes significantly as the magnitude of the rotor inlet vortices increases, and very different residual traces of the stator secondary flows are found downstream of the rotor. On the contrary, the increase of rotor loading enhances the unsteadiness in the rotor secondary flows but has a little effect on the vortex-vortex interaction. For the large axial gap, a reduction of stator-related effects at the rotor exit is encountered when the stator incidence is increased as a result of the different mixing rate within the cascade gap.

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