Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favourably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analysed for several points of operation and a very detailed quantitative loss breakdown is presented.

Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Vol 127 (4) ◽  
pp. 649-658 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favorably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analyzed for several points of operation and a very detailed quantitative loss breakdown is presented.

Simulation of the Interaction of Labyrinth Seal Leakage Flow and Main Flow in an Axial Turbine

2002 ◽  
Author(s):  
Jan E. Anker ◽  
Ju¨rgen F. Mayer
Keyword(s):  
Experimental Data ◽  
Labyrinth Seal ◽  
Main Flow ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Test Case ◽  
Leakage Flow ◽  
Computational Results ◽  
Axial Turbine ◽  
The Impact

This paper presents the simulation of the flow in a 1.5 stage low-speed axial turbine with shrouded rotor blades and focuses on the interaction of the labyrinth seal leakage flow with the main flow. The presented results were obtained using the Navier-Stokes code ITSM3D developed at University of Stuttgart. A comparison of the computational results with experimental data of this test case gained at Ruhr-Universita¨t Bochum verifies that the flow solver is capable of reproducing the leakage flow effects to a sufficient extent. The computational results are used to examine the influence of the leakage flow on the flow field of the turbine. By varying the clearance height of the labyrinth in the simulations, the impact of the re-entering leakage flow on the main flow is studied. As demonstrated in this paper, leakage flow not only introduces mixing losses but can also dominate the secondary flow and induce severe losses. In agreement with the experimental data the computational results show that at realistic clearance heights the leakage flow gives rise to negative incidence over a considerable part of the downstream stator which causes the flow to separate.

Modeling and Analysis of Main Flow–Shroud Leakage Flow Interaction in LP Turbines

2006 ◽  
Author(s):  
Jochen Gier ◽  
Karl Engel ◽  
Bertram Stubert ◽  
Ralf Wittmaack
Keyword(s):  
Main Flow ◽  
Navier Stokes ◽  
Aerodynamic Load ◽  
Leakage Flow ◽  
Modeling And Analysis ◽  
Simplified Approach ◽  
Leakage Flows ◽  
Flow Phenomena ◽  
Flow Effects ◽  
The Impact

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. For the design of modern jet engine turbines it becomes increasingly important to include the impact of shroud leakage flows in the aerodynamic design. There are two main aspects connected to this issue. The first aspect is to optimize the cavity flow and its interaction with the main flow. The second aspect is to perform the airfoil design with boundary conditions, which include the shroud leakage flow effects. In comparison to the simplified approach of neglecting the real endwall geometry and leakage flow this should enable the designer to produce improved airfoils for the entire span. In order to address the second aspect of supporting the airfoil design with improved shroud leakage consideration within the airfoil design process, an efficient procedure for modeling the shroud leakage flow has been implemented into the design Navier-Stokes code. The intention is to model the major leakage flow phenomena without the necessity of pre-defining all details of the shroud geometry. In the paper the results of this model are compared to conventional computations, computations with mesh-resolved cavities and experimental data. The differences are discussed and the impact of certain configuration aspects are analyzed.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

Numerical analysis of the effects of circumferential groove casing suction in a counter-rotating axial flow compressor

2020 ◽  
pp. 095765092095169
Author(s):  
Tian Liang ◽  
Bo Liu ◽  
Stephen Spence ◽  
Liying Jiao
Keyword(s):  
Axial Flow ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Tip Leakage ◽  
Axial Flow Compressor ◽  
Circumferential Groove ◽  
Flow Compressor ◽  
The Impact

To extend the current understanding of the circumferential groove casing suction applied to a counter-rotating axial flow compressor, the impact of different axial locations of the circumferential suction groove on the characteristics of the tip leakage flow (TLF) and the corresponding physical mechanisms producing the stability enhancement have been studied based on validated numerical simulations. The results show that the optimal location for the suction groove is at around 20% axial chord, which demonstrated a high potential for reducing additional stall mass flow coefficient with about 8.4% increment in the stall margin. After the casing suction groove was applied, the interface between the incoming main flow and TLF was pushed significantly downstream in the second rotor. The blade loading in the region below the groove, the tip leakage flow angle and the reversed axial momentum flux injected into main flow passage through the tip gap were all reduced, which contributed to the stall margin improvement. Detailed analysis of the tip leakage flow structures showed that the TLF originating from different chord locations played different roles in the stall inception process. It was found to be more effective to improve stall margin and adiabatic efficiency by controlling the front part of the TLF, which was most sensitive.

Experimental and Numerical Investigation Into the Unsteady Interaction of Labyrinth Seal Leakage Flow and Main Flow in a 1.5-Stage Axial Turbine

2004 ◽  
Author(s):  
A. Giboni ◽  
K. Wolter ◽  
J. R. Menter ◽  
H. Pfost
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Main Flow ◽  
Navier Stokes ◽  
Experimental Program ◽  
Leakage Flow ◽  
Axial Turbine ◽  
Flow Phenomena ◽  
Grid Points

This paper presents the results of experimental and numerical investigations into the flow in a 1.5-stage low-speed axial turbine with a straight labyrinth seal on the rotor shroud. The paper focuses on the time dependent interaction between the leakage flow and the main flow. The experimental program consists of time accurate measurements of the three-dimensional properties of the main flow. The region of the entering leakage flow downstream of the rotor trailing edge was of special interest. The measurements were carried out using pneumatic five-hole probes and three dimensional hot-wire probes at the design operating point of the turbine. The measurement planes behind the three blade rows extend over one pitch from the shroud to the casing. The complex three-dimensional flow field is mapped in great detail by 1,008 points per measurement plane. The time-accurate experimental data of the three measurement planes was compared with the results of unsteady, numerical simulations of the turbine flow. The 3D-Navier-Stokes Solver CFX-TASCflow was used. The experimental and numerical results correspond well and allow detailed analysis of the mixing process. As demonstrated in this paper, the leakage flow causes strong fluctuations of the secondary flow behind the rotor and the second stator. Above all, the high number of numerical grid points reveals both the secondary flow phenomena and the vortex structures of the mixing zone. The time-dependence of both position and intensity of the vortices is shown. The development of the important leakage vortex is illustrated and explained. The paper shows that even at realistic clearance heights the leakage flow gives rise to negative incidence of considerable parts of the downstream stator which causes the flow to separate. Thus, labyrinth seal leakage flow should be taken properly into account in the design or optimization process of turbomachinery.

Inverse Design and Optimization of a Return Channel for a Multistage Centrifugal Compressor

2004 ◽  
Vol 126 (5) ◽  
pp. 799-806 ◽  
Author(s):  
A´rpa´d Veress ◽  
Rene´ Van den Braembussche
Keyword(s):  
Design Method ◽  
Design Procedure ◽  
Leading Edge ◽  
Secondary Flows ◽  
Inverse Design ◽  
Navier Stokes ◽  
Design And Optimization ◽  
The Cross ◽  
Return Channel ◽  
The Impact

The design and optimization of a multistage radial compressor vaneless diffuser, cross-over and return channel is presented. An analytical design procedure for 3D blades with prescribed load distribution is first described and illustrated by the design of a 3D return channel vane with leading edge upstream of the cross-over. The analysis by means of a 3D Navier–Stokes solver shows a substantial improvement of the return channel performance in comparison with a classical 2D channel. Most of the flow separation inside and downstream of the cross-over could be avoided in this new design. The geometry is further improved by means of a 3D inverse design method to smooth the Mach number distribution along the vanes at hub and shroud. The Navier–Stokes analysis shows a rather modest impact on performance but the calculated velocity distribution indicates a more uniform flow and hence a larger operating range can be expected. The impact of vane lean on secondary flows is investigated and further performance improvements have been obtained with negative lean.

Time-Resolved Numerical Investigation of the Interaction of Labyrinth Seal Leakage and Main-Flow in a 1.5-Stage LP Turbine

2011 ◽  
Author(s):  
Marc H.-O. Biester ◽  
Lasse Mueller ◽  
Joerg R. Seume ◽  
Yavuz Guendogdu
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Labyrinth Seal ◽  
Main Flow ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Time Resolved ◽  
Lp Turbine ◽  
German Aerospace

In axial turbomachinery such as low pressure turbines, shrouded airfoils with labyrinth seals are commonly used. Among different sealing options, labyrinth seals in particular are characterized by long term durability and high sealing efficiency. Since a leakage flow is inevitable, a thorough understanding of how the leakage flow exits the cavities, its interaction with the main flow, and the induction of losses is necessary. In order to take into account unsteady effects, three-dimensional time resolved RANS computations of a 1.5 stage LPT rig in its design operating point are conducted. To capture effects in the boundary layer, a low Reynolds approach is used at the blade surface as well as on the hub and tip surfaces. To match the real geometry of the turbine blades, fillets have been modeled. Simulations were performed using the TRACE solver developed by the German Aerospace Center (DLR). The investigation shows how cavity flows have a significant influence on the main-flow aerodynamics and the loss generation. Steady and unsteady results with full spatially discretized cavities show a significant decrease of isentropic efficiency compared to simulations without cavities. The efficiency drop for the steady and time-averaged cavity computations can be explained with intensified secondary flow. The time resolved calculation shows a strong non-uniformity of the leakage flux depending on the instantaneous circumferential position of the up- and downstream blades. The time dependent ingress of cavity leakage results in the formation of a counter-rotating vortex pair. In terms of the influence on the main flow, it is shown that the interaction is limited to the end walls with almost no influence on the midspan flow.

Separation Bubbles Under Steady and Periodic-Unsteady Main Flow Conditions

2000 ◽  
Author(s):  
Weiliang Lou ◽  
Jean Hourmouziadis
Keyword(s):  
Pressure Distribution ◽  
Velocity Profiles ◽  
Main Flow ◽  
Test Facility ◽  
Free Shear Layer ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Time Space ◽  
Separation Bubbles ◽  
The Impact

Based on an experimental investigation carried out in a low speed test facility at the Berlin University of Technology, this paper describes the formation of separation bubbles under steady and periodic-unsteady main flow conditions. The aim of the investigation was to understand the mechanism of separation, transition and reattachment and the effect of main flow unsteadiness on it. Separation bubbles for various main flow conditions were generated over a large flat plate, which experienced a similar pressure distribution to that on the suction surface of blades in turbomachines. The pressure distribution was generated by a contoured wall opposite the plate. Aimed at separating the effect of the velocity and the turbulence wake, this paper considers only the influence of the velocity wake. To this effect, a rotating flap was mounted downstream of the test section to produce periodic oscillations of the main flow. The overall flow field under steady main flow conditions was obtained by hot-wire measurements. Pressure taps were used to measure the pressure distribution over the plate. The Reynolds number effects were determined and compared to the measurement results in the literature. Results for periodic-unsteady separation bubbles are shown using different Strouhal numbers, oscillation amplitudes and Reynolds numbers. Ensemble averaged mean velocity profiles and the Ensemble averaged rms velocity profiles are used to demonstrate the development of the periodic boundary layer. Time-space diagrams are plotted to show the development of the periodic-unsteady boundary layers. The characteristic instability frequencies in the free shear layer are identified. The impact of the major parameters, Strouhal number and amplitude, on the bubble formation are discussed.

The structure and stabilization by boundary conditions of an annular flow of Kolmogorov type

2017 ◽  
Vol 32 (4) ◽  
Author(s):  
Andrei A. Kornev
Keyword(s):  
Boundary Conditions ◽  
Annular Flow ◽  
Stokes Equations ◽  
Numerical Algorithms ◽  
Main Flow ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Internal Boundary ◽  
Navier Stokes Equations ◽  
Quasistationary Solutions

AbstractA system of Navier-Stokes equations with a right-hand side is considered in the case when the system approximately describes the motion of a thin layer of a viscous incompressible fluid in an annular domain under the action of external electromagnetic force. The problem possesses an unstable two-stream nonstationary main flow and a set of quasistationary solutions of vortex type for the tested range of parameters. A method of study of the general dynamic pattern is proposed in the paper. The method is based on the construction of control boundary conditions specified on the internal boundary of the annulus and providing the stabilization of considered unstable modes. The problem of boundary stabilization of the main and secondary flows is also solved numerically and we obtained that it is sufficient to take into account only a part of unstable modes in the construction of stabilizing conditions for the main flow. The method based on the partial stabilization of the main flow is first proposed for stabilization of secondary flows, which essentially simplifies the implementation of the algorithm. Formulations of the problems and numerical algorithms are presented.

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