scholarly journals Calculation of Turbulent Flows Through Linear Turbine Cascades With and Without Tip Clearance

1995 ◽  
Author(s):  
Hun G. Lee ◽  
Jung Y. Yoo ◽  
Jun W. Yun
Keyword(s):  
Turbulent Flows ◽  
Incompressible Flows ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Group Method ◽  
Tip Clearance Flow ◽  
Vena Contracta

Three dimensional turbulent incompressible flows through linear cascades of turbine rotor blades with high turning angles have been analyzed numerically by using a generalized k-ε model which is a high Reynolds number form and derived by RNG (renormalized group) method to account for the variation of the rate of strain. A second order upwind scheme is used to suppress numerical diffusion in approximating the convective terms. Boundary-fitted coordinates are adopted to represent the complex blade geometry accurately. For the case without tip clearance, secondary flows and flow losses are shown to be in good agreement with previous experimental results. For the case with tip clearance, the effects of the passage vortex and tip clearance flow on the total pressure loss as well as their interactions are discussed. The flow within the tip clearance has been analyzed to illustrate the existences of the tip clearance vortex and vena contracta.

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 Tip Leakage Flow in a Linear Turbine Cascade

1988 ◽  
Vol 110 (1) ◽  
pp. 18-26 ◽  
Author(s):  
J. Moore ◽  
J. S. Tilton
Keyword(s):  
Heat Transfer ◽  
Potential Flow ◽  
Pressure Rise ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Vena Contracta

An experimental and analytical study of flow in the tip clearance gap of a linear turbine rotor blade cascade has been performed. Measurements of wall static pressures and flow velocities are used to verify a flow model involving a vena contracta, near the tip gap entrance, followed by flow mixing to fill the gap. A frequently referenced potential flow theory for flow into a tip gap is found to be in error and the correct theory is shown to model the unloading along the pressure surface of the blade and the endwall static pressure distribution up to the vena contracta accurately. A combined potential flow and mixing model accounts for the pressure rise in the tip gap due to mixing. Turbine tip heat transfer is also discussed and a correlation of local heat transfer rates for essentially incompressible flow over unshrouded turbine rotor blades is presented.

Three-Dimensional Flowfields Inside a Transonic Compressor With Swept Blades

1991 ◽  
Vol 113 (2) ◽  
pp. 241-250 ◽  
Author(s):  
C. Hah ◽  
A. J. Wennerstrom
Keyword(s):  
Turbulence Modeling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Improved Performance

The concept of swept blades for a transonic or supersonic compressor was reconsidered by Wennerstrom in the early 1980s. Several transonic rotors designed with swept blades have shown very good aerodynamic efficiency. The improved performance of the rotor is believed to be due to reduced shock strength near the shroud and better distribution of secondary flows. A three-dimensional flowfield inside a transonic rotor with swept blades is analyzed in detail experimentally and numerically. A Reynolds-averaged Navier–Stokes equation is solved for the flow inside the rotor. The numerical solution is based on a high-order upwinding relaxation scheme, and a two-equation turbulence model with a low Reynolds number modification is used for the turbulence modeling. To predict flows near the shroud properly, the tip-clearance flow also must be properly calculated. The numerical results at three different operating conditions agree well with the available experimental data and reveal various interesting aspects of shock structure inside the rotor.

scholarly journals Three-Dimensional Flowfields Inside a Transonic Compressor With Swept Blades

1990 ◽  
Author(s):  
C. Hah ◽  
A. J. Wennerstrom
Keyword(s):  
Turbulence Modeling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Tip Clearance Flow ◽  
Transonic Compressor ◽  
Improved Performance

The concept of swept blades for a transonic or supersonic compressor was reconsidered by Wennerstrom in the early 1980s. Several transonic rotors designed with swept blades have shown very good aerodynamic efficiency. The improved performance of the rotor is believed to be due to reduced shock strength near the shroud and better distribution of secondary flows. A three-dimensional flowfield inside a transonic rotor with swept blades is analyzed in detail experimentally and numerically. A Reynolds-averaged Navier-Stokes equation is solved for the flow inside the rotor. The numerical solution is based on a high-order upwinding relaxation scheme, and a two-equation turbulence model with a low Reynolds number modification is used for the turbulence modeling. To properly predict flows near the shroud, the tip-clearance flow also must be properly calculated. The numerical results at three different operating conditions agree well with the available experimental data and reveal various interesting aspects of shock structure inside the rotor.

Tip Leakage Flow in Radial Inflow Rotor of a Microturbine With Varying Blade-Shroud Clearance

2007 ◽  
Author(s):  
Qinghua Deng ◽  
Jiufang Niu ◽  
Zhenping Feng
Keyword(s):  
Three Dimensional ◽  
Flow Simulation ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Transverse Mass ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Clearance Flow

In this paper, tip clearance flow in a radial inflow turbine rotor under the stage environment is investigated using a three-dimensional viscous flow simulation with three different blade-shroud gap heights of 1%, 2% and 3% of the local span. The results indicate that more relative casing motion increases the scraping effect on tip leakage flow at the rotor entrance. Also, the scraping flow can dominate the whole tip clearance at the rotor entrance when the velocity is high enough at the rotor tip diameter. Regardless of the transverse mass flow rates of the three tip clearances, the results strongly exhibit the characteristics of linearity when the relative meridional length S is greater than 40%. According to the analysis of leakage flow fields in the tip clearance, measures such as a circumference slot, axial slot, or honeycomb are proposed to be applied and placed at the shroud surface over the exducer of the rotor for effectively reducing the transverse flow.

Interaction Mechanisms Between Tip Leakage Flow and the Passage Vortex in a Linear Turbine Rotor Cascade

1988 ◽  
Vol 110 (3) ◽  
pp. 329-338 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Generation Mechanisms ◽  
Downstream Flow

In order to study the loss generation mechanisms due to the tip-leakage flow in turbine rotor passages, extensive traverse measurements were made of the three-dimensional flows in a low-speed linear cascade for various tip-clearance sizes and for various cascade inlet flow angles (or incidences). Effects of the leakage flow on the cascade downstream flow fields and interactions between the leakage flow and the passage vortices are discussed in detail based on the traverse measurements and flow-visualization tests in terms of secondary flows and the associated losses. Other traverses were also performed of the tip-casing endwall flows both inside and outside the tip-clearance gap using a micro five-hole pitot tube to reveal the axial development of the interaction throughout the cascade passage. Overall loss characteristics of the present high-turning cascade with blunt leading and trailing edges are obtained and compared with those predicted by the Ainley–Mathieson method.

Investigation of Compressor Tip Clearance Flow Structure

2010 ◽  
Author(s):  
Roland Matzgeller ◽  
Yves Burgold
Keyword(s):  
Boundary Conditions ◽  
Flow Structure ◽  
Three Dimensional ◽  
Measurement Data ◽  
Cross Flow ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage

By the use of decomposition for the three-dimensional flow field in compressors into independent through flow and cross flow as first proposed by Chen et al., the tip gap flow structure for different tip gap heights and boundary conditions is examined. Tracing the roll up of a shear layer in planes normal to the blade camber line the position of the tip leakage vortex is presented in a non-dimensional formulation. Tests for different boundary conditions, i.e. the distinction between a stationary and a rotating end-wall as well as the use of different fluid models are made to quantify their influence on the tip leakage vortex position. By comparing the analytical result to data extracted from three-dimensional RANS computations and to measurement data the validity of the model is presented. Finally, an attempt is made to find a criterion for the occurrence of tip leakage vortex induced stall of tip critical rotor blades. This is done by a correlation based on the previously derived non-dimensional vortex trajectory and the stagger angle. This criterion is again tested on results of a three dimensional RANS computation proving its validity.

Redistribution of Total Temperature Through an Annular Turbine Nozzle Cascade

2018 ◽  
Author(s):  
Joshua Szczudlak ◽  
Sara Rostami ◽  
Arman Mirhashemi ◽  
Scott Morris ◽  
Greg Sluyter ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Transition Model ◽  
High Pressure Turbine ◽  
Spatial Gradients ◽  
Total Temperature ◽  
Inlet Conditions ◽  
Rans Analysis

Flow exiting the combustor is highly turbulent and contains significant spatial gradients of pressure and temperature. The high pressure turbine nozzle vanes operating in this environment redistribute these spatial gradients and impact the inflow characteristics of the turbine rotor blades. The present study investigates the redistribution of total temperature through a turbine nozzle vane. Numerical investigation was performed using three-dimensional RANS analysis. Simulations were conducted using the Wilcox k–ω turbulence model and Shear Stress Transport (SST) with and without γ–Reθ transition model. Experimental measurements were obtained in an annular nozzle cascade facility. Two sets of inlet conditions were considered. The first was a nominally uniform total temperature. The second had a span-wise variation of total temperature. Both sets of inlet conditions had nominally the same inlet total pressure and inlet Mach number. Span-wise redistribution was evaluated using the circum-ferentially averaged total temperature profile at a plane downstream of the nozzle. Physical arguments about the influence of nozzle secondary flows on this redistribution are presented.

A Rotating Facility to Study Heat Transfer in the Cooling Passages of Turbine Rotor Blades

1996 ◽  
Vol 210 (1) ◽  
pp. 55-63 ◽  
Author(s):  
W D Morris
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Research Facility ◽  
Cooling Channels ◽  
Study Heat Transfer ◽  
New Research ◽  
Selection Of

This paper describes a new research facility designed to study the effect of rotation on heat transfer in the cooling channels of gas turbine rotor blades. Rotation influences cooling performance via secondary flows generated because of Coriolis forces and centripetal buoyancy. The resulting complex three-dimensional flow creates asymmetric heat transfer over the channel surface. The research facility has been designed to permit experiments to be undertaken that are near to actual engine conditions. The paper includes details of the design philosophy, construction and commissioning of the facility, together with a selection of experimental data.

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