Study of Losses in a Leakage Flow Through the Passage of Shrouded Turbine Blades With Swirl Velocity

2001 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Major Effect ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Local Pressure ◽  
Leakage Flow Rate ◽  
Calculation Results

In this paper the study of the flows over shrouded turbine blades with staggered-seals is presented by computing the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations along with a compressible non-linear k-ε turbulence model. The swirl of the blade is coupled into the calculation. A multi-zone technique is used to generate the grids in the complex flow channel. The calculation results show that the leakage flow rate in the seal-channel is dominated by the pressure difference. It was also observed that the circumferential momentum transfer in the channel is very slow in the region in front of the seal tooth. The major effect of the rotating blade is the increase of local pressure distribution along the shrouded tip clearance path. However, the swirl motion of the blade tip does not significantly change the flow pattern in the axial-radial plane.

Leakage Flow Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Navier Stokes Equations ◽  
Leakage Flow Rate

In this paper the flows over shrouded turbine blades with single, double, and triple tip seals were simulated by using the two-dimensional Reynolds-averaged Navier-Stokes equations and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the flow in the seal channel is very complicated and the leakage flow rate is dominated by the minimum flow area and the pressure difference. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, it appears there is not a simple function between the leakage flow and the pressure difference.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

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.

scholarly journals Computation of Flow Past a Turbine Blade With and Without Tip Clearance

1991 ◽  
Author(s):  
W. R. Briley ◽  
D. V. Roscoe ◽  
H. J. Gibeling ◽  
R. C. Buggeln ◽  
J. S. Sabnis ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Main Stream ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Gas Generator

Three-dimensional solutions of the ensemble-averaged Navier-Stokes equations have been computed for a high-turning turbine rotor passage, both with and without tip clearance effects. The geometry is Pratt & Whitney’s preliminary design for the Generic Gas Generator Turbine (GGGT), having an axial chord of 0.5 inch and turning angle of about 160 degrees. The solutions match the design Reynolds number of 3x 106/inch and design inflow/outflow distributions of flow quantities. The grid contains 627,000 points, including 20 radial points in the clearance gap of 0.015 inch, and has a minimum spacing of 10−4 inch adjacent to all surfaces. The solutions account for relative motion of the blade and shroud surfaces and include a backstep on the shroud. Computed results are presented which show the general flow behavior, especially near the tip clearance and backstep regions. The results are generally consistent with experimental observations for other geometries having thinner blades and smaller turning angles. The leakage flow includes some fluid originally in the freestream at 91 percent span. Downstream, the leakage flow behaves as a wall jet directed at 100 degrees to the main stream, with total pressure and temperature higher than the freestream. Radial distributions of circumferentially-averaged flow quantities are compared for solutions with and without tip leakage flow. Two-dimensional solutions are also presented for the mid-span blade geometry for design and off-design inflow angles.

Three-Dimensional Analysis of Turbine Rotor Flow Including Tip Clearance

1993 ◽  
Author(s):  
R. Heider ◽  
J. M. Duboue ◽  
B. Petot ◽  
G. Billonnet ◽  
V. Couaillier ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbine Rotor Blade ◽  
Calculation Results ◽  
Rotor Flow

A 3D Navier-Stokes investigation of a high pressure turbine rotor blade including tip clearance effects is presented. The 3D Navier-Stokes code developed at ONERA solves the three-dimensional unsteady set of mass-averaged Navier-Stokes equations by the finite volume technique. A one step Lax-Wendroff type scheme is used in a rotating frame of reference. An implicit residual smoothing technique has been implemented, which accelerates the convergence towards the steady state. A mixing length model adapted to 3D configurations is used. The turbine rotor flow is calculated at transonic operating conditions. The tip clearance effect is taken into account. The gap region is discretized using more than 55,000 points within a multi-domain approach. The solution accounts for the relative motion of the blade and casing surfaces. The total mesh is composed of five sub-domains and counts 710,000 discretization points. The effect of the tip clearance on the main flow is demonstrated. The calculation results are compared to a 3D inviscid calculation, without tip clearance.

An Experimental Investigation Into Turbine Flutter Characteristic at Different Tip-Clearances

2006 ◽  
Author(s):  
X. Q. Huang ◽  
L. He ◽  
D. L. Bell
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Pressure Measurements ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Local Pressure ◽  
Unsteady Pressure ◽  
Pressure Suction ◽  
Unsteady Pressure Measurements

This paper documents an investigation into unsteady flow in a three-dimensional oscillating turbine cascade with emphasis on the influence of tip clearance. Systematic experimental measurements were performed on a low-speed turbine cascade rig. The cascade consists of seven prismatic turbine blades, with the middle blade being driven to oscillate in a three-dimensional bending/flapping mode. Blades were instrumented with pressure tappings at six span-wise sections to facilitate three dimensional steady and unsteady pressure measurements on the blade surface. The steady pressure measurements are complemented by CFD simulations. Both are in a good agreement and indicate a marked local pressure suction peak at 70–90% chord on the suction surface resulting from the tip-clearance vortex. The measured unsteady pressure shows that this tip-clearance induced suction peak has a significant destabilising influence on the aerodynamic damping at a large tip-clearance (5% chord). Whilst at a small tip clearance (1.25–2.5% chord), the tip-clearance actually has a stabilising effect. The behaviour is in line with a quasi-steady analysis.

The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow

2005 ◽  
Vol 129 (2) ◽  
pp. 303-310 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Turbine Performance ◽  
Leakage Flow Rate ◽  
Single Piece ◽  
Flow Through ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Leakage Fraction

Individual nozzle guide vanes (NGV’s) in modern aeroengines are often cast as a single piece with integral hub and casing endwalls. When in operation, there is a leakage flow through the chord-wise interplatform gaps. An investigation into the effect of this leakage flow on turbine performance is presented. Efficiency measurements and NGV exit area traverse data from a low-speed research turbine are reported. Tests show that this leakage flow can have a significant impact on turbine performance, but that below a threshold leakage fraction this penalty does not rise with increasing leakage flow rate. The effect of various seal clearances are also investigated. Results from steady-state simulations using a three-dimensional multiblock Reynolds-averaged Navier-Stokes solver are presented with particular emphasis paid to the physics of the mainstream/leakage interaction and the loss generation.

Prediction of Low Speed Compressor Rotor Flowfields With Large Tip Clearances

2003 ◽  
Author(s):  
Anurag Gupta ◽  
S. Arif Khalid ◽  
G. Scott McNulty ◽  
Lyle Dailey
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Low Speed ◽  
Compressor Rotor ◽  
Wide Range ◽  
Measured Pressure

Rotor tip modeling fidelity, grid resolution, and near wall modeling have been examined to determine the requirements for an accurate prediction of the effects of large tip clearance in a low-speed axial compressor rotor. The effort, using a Reynolds-Averaged Navier-Stokes (RANS) solver, aimed to obtain the most accurate predictions from a three-dimensional, steady, single blade row simulation. A recently tested, modern low speed rotor, was used as the test geometry; the measured pressure rise characteristic as well as detailed data near stall was used to evaluate the ability of different modeling strategies to capture the correct flow structure. The leakage flow was quantified to show that a wide range of tip blockage could be obtained for different simulations of the same geometry and conditions. The results show that using a square tip and gridding to fully resolve the real tip gap was better able to capture the effects of loading on the leakage flow than either of the approximate models studied. Sufficient clustering near the casing to capture the shear layers was also found to be critical. While wall integration provided the best results in simultaneously improving the prediction of pressure rise characteristics and flow range, higher fidelity wall modeling and a casing y+ of approximately 3 were found to provide similar benefits.

Validation of a Navier-Stokes Solver for CFD Computations of Transonic Compressors

2006 ◽  
Author(s):  
Roberto Biollo ◽  
Ernesto Benini
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Test Case ◽  
Complex Flow

The progress of numerical methods and computing facilities has led to using Computational Fluid Dynamics (CFD) as a current tool for designing components of gas turbine engines. It is known, however, that a sophisticated numerical model is required to well reproduce the many complex flow phenomena which characterize compression systems, such as shock waves and their interactions with boundary layers and tip clearance flows. In this work, the flow field inside the NASA Rotor 37, a well known test case representative of complex three-dimensional viscous flow structures in transonic bladings, was simulated using a commercial CFD code based on the 3-D Reynolds-averaged Navier-Stokes equations. In order to improve the accuracy of predictions, different aspects of the numerical model were analyzed; in particular, an attempt was made to understand the influence of grid topology, number of nodes and their distribution, turbulence model, and discretization scheme of numerical solution on the accuracy of computed results. Existing experimental data were used to assess the quality of the solutions. The obtainment of a good agreement between computed and measured performance maps and downstream profiles was clearly shown. Also, detailed comparisons with experimental results indicated that the overall features of the three-dimensional shock structure, the shock-boundary layer interaction, and the wake development can be calculated very well in the numerical approach for all the operating conditions. The possibility for a numerical model to better understand the aerodynamic behaviour of existing transonic compressors and to help the design of new configurations was demonstrated. It was also pointed out that the development of an accurate model requires the knowledge of both the physical phenomena place within the flow field and the features of the code which model them.

Leakage Flow and Heat Transfer Over Shrouded Turbine Blades

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Complex Flow ◽  
Flow Area ◽  
Sharp Drop ◽  
Leakage Flow Rate

Abstract In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.

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