Secondary Flow Structures and Losses in a Radial Turbine Nozzle

2011 ◽  
Author(s):  
Christoph K. Natkaniec ◽  
Jasper Kammeyer ◽  
Joerg R. Seume
Keyword(s):  
Secondary Flow ◽  
Commercial Vehicle ◽  
Flow Structures ◽  
Stage Model ◽  
Turbine Stage ◽  
Radial Turbine ◽  
Cylindrical Shaft ◽  
Stator Vane ◽  
Shaft Seals ◽  
Secondary Vortices

An analysis of secondary flow structures and losses in a variable-vane radial turbine geometry is provided based on CFD. A complete turbine stage of a commercial vehicle turbocharger is modeled, including the entire 360° rotor and stator, in order to account for the circumferential non-uniformity of the flow. The full-stage model consists of approximately 12,500,000 nodes. The stator domain accounts for the endwall clearance on the hub side of the nozzle vanes. As an additional feature typical for variable turbine geometries, cylindrical shaft seals at the stator vane axis at hub and shroud as well as four circumferentially equidistant spacers are modeled. These geometrical details allow a more realistic simulation of the stator domain. In an analysis using fields of helicity and Q-Criterion, the present features are found to induce additional secondary vortices in the stator, in addition to the inflow and horse shoe vortices found by previous investigators. A detailed analysis of the secondary flow structures in this realistic stator shows that the spacers contribute 33% to the overall stator losses.

Investigation of Secondary Flow Behavior in a Radial Turbine Nozzle

2006 ◽  
Author(s):  
Mohammed Alexin Putra ◽  
Franz Joos
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Single Vortex ◽  
Flow Angle ◽  
Radial Turbine ◽  
Passage Vortex ◽  
Flow Phenomena ◽  
Contour Plots ◽  
Axial Turbines ◽  
Secondary Vortices

Fundamental investigation of secondary flow phenomena in a radial turbine nozzle are presented. L2F measurements have been used for validation of numerical CFD calculations. Having a good agreement by using the Reynolds stress turbulence model (RSM) the numerical results have been used further to analyse the structure of secondary vortices. Contour plots of the flow angle with typical isoline pattern as well as the vorticity have been evaluated. It is shown that the channel of the radial nozzle similar secondary vorticity systems generates as known from the axial turbine nozzles. The formation and the development of the horse-shoe vortex and the corner vortex are discussed. The well known passage vortex of the axial turbines could not been found because of the small curvature of the streamlines. Instead of these an additional single vortex can be observed, called the “inflow” vortex caused by the unsymmetrical flow into the radial cascade from the upstream scroll.

Investigation of Secondary Flow Behavior in a Radial Turbine Nozzle

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Mohammad Alexin Putra ◽  
Franz Joos
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Horseshoe Vortex ◽  
Single Vortex ◽  
Flow Angle ◽  
Radial Turbine ◽  
Flow Phenomena ◽  
Contour Plots ◽  
Axial Turbines ◽  
Secondary Vortices

Fundamental investigation of secondary flow phenomena in a radial turbine nozzle are presented. Laser two focus (L2F) measurements have been used for validation of numerical computational fluid dynamics (CFD) calculations. Having a good agreement by using the Reynolds stress turbulence model (RSM), the numerical results have been further used to analyze the structure of secondary vortices. Contour plots of the flow angle with typical isoline pattern, as well as the vorticity, have been evaluated. It is shown that the channel of the radial nozzle similar secondary vorticity systems generates as known from the axial turbine nozzles. The formation and the development of the horseshoe vortex and the corner vortex are discussed. The well known passage vortex of the axial turbines could not been found because of the small curvature of the streamlines. Instead of these, an additional single vortex can be observed, called the “inflow” vortex caused by the unsymmetrical flow into the radial cascade from the upstream scroll.

A Numerical Study of the Flow Fields in a Highly Off-Design Variable Geometry Turbine

2010 ◽  
Author(s):  
Jason Walkingshaw ◽  
Stephen Spence ◽  
Jan Ehrhard ◽  
David Thornhill
Keyword(s):  
Secondary Flow ◽  
Numerical Study ◽  
Internal Flow ◽  
Flow Fields ◽  
Flow Structures ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Blade Loading ◽  
Tip Leakage ◽  
Stator Vane

Conventionally, radial turbines have almost exclusively used radially fibred blades. While issues of mechanical integrity are paramount, there may be opportunities for improving turbine efficiency through a 3D blade design without exceeding mechanical limits. Off-design performance and understanding of the secondary flow structures now plays a vital role in the design decisions made for automotive turbocharger turbines. Of particular interest is extracting more energy at high pressure ratios and lower rotational speeds. Operating in this region means the rotor will experience high values of positive incidence at the inlet. A CFD analysis has been carried out on a scaled automotive turbine utilizing a swing vane stator system. To date no open literature exists on the flow structures present in a standard VGT system. Investigations were carried out on a 90 mm diameter rotor with the stator vane at the maximum, minimum and 25% mass flow rate positions. In addition stator vane endwall clearance existed at the hub side. From investigation of the internal flow fields of the baseline rotor, a number of areas that could be optimized in the future with three dimensional blading were identified. The blade loading and tip leakage flow near inlet play a significant role in the flow development further downstream at all stator vane positions. It was found that tip leakage flow and flow separation at off-design conditions could be reduced by employing back swept blading and redistributing the blade loading. This could potentially reduce the extent of the secondary flow structures found in the present study.

Impact of Varying High- and Low-Pressure Turbine Purge Flows on a Turbine Center Frame and Low-Pressure Turbine System

2019 ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
A. Peters ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Flow Structures ◽  
Turbine Stage ◽  
Flow Conditions ◽  
Flow Rates ◽  
Low Pressure Turbine ◽  
Purge Flow ◽  
Inflow Conditions

Abstract This paper presents the experimental and numerical evaluation and comparison of the different flow fields downstream of a turbine center frame duct and a low-pressure turbine stage, generated by varying the inlet flow conditions to the turbine center frame duct. The measurements were carried out in an engine-representative two-stage two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The rig consists of a high-pressure (HPT) and a low-pressure (LPT) turbine stage, connected via a turbine center frame (TCF) with non-turning struts. Four individual high-pressure turbine purge flow rates and two low-pressure turbine purge flow rates were varied to achieve different engine-relevant TCF and LPT inlet flow conditions. The experimental data was acquired by means of five-hole-probe area traverses upstream and downstream of the TCF, and downstream of the LPT. A steady RANS simulation taking all purge flows in account was used for comparison and additional insight are gained from a numerical variation of the HPT and LPT purge flow rates. The focus of this study is on the impact of the variations in TCF inlet conditions on the secondary flow generation through the TCF duct and the carry-over effects on the exit flow field and performance of the LPT stage. Existing work is limited by either investigating multi-stage LPT configurations with generally very few measurements behind the first stage or by not including relevant HPT secondary flow structures in setting up the LPT inflow conditions. This work addresses both of these shortcomings and presents new insight into the TCF and LPT aerodynamic behavior at varying the HPT and LPT purge flows. The results demonstrate the importance of the HPT flow structures and their evolution through the TCF duct for setting up the LPT inflow conditions, and ultimately for assessing the performance of the first LPT stage.

The Role of Density Gradient in Species Migration and Secondary Flow Structures in Axial Flow Turbines

2013 ◽  
Author(s):  
Xin Zou ◽  
Xin Yuan ◽  
W. N. Dawes
Keyword(s):  
Heat Transfer ◽  
Unsteady Flow ◽  
Secondary Flow ◽  
Axial Flow ◽  
Flow Structures ◽  
Turbine Stage ◽  
Flow And Heat Transfer ◽  
Baroclinic Torque ◽  
Hot Streak ◽  
Spatially Varying

Physical quantities at combustor exit, hence turbine inlet, are highly non-uniform not just due to spatially varying combustion but also due to the dilution air and film-cooling air used in the combustor design. The effects of inlet total pressure and temperature (“hot streak”) non-uniformity on the unsteady flow and heat transfer of turbine stages have been widely studied. However, few studies have considered the effects of inlet density non-uniformity derived from spatially varying species concentration (“species streak”). This “species streak” results in density gradients which, if not aligned with pressure gradients, will lead to the generation of baroclinic torque which will influence the generation, migration and evolution of vorticity within the turbine passages and hence the secondary flow structure and mixing within the blade row. This paper examines the “species streak” effects on the unsteady flow and heat transfer within a high-pressure axial flow turbine stage focusing on the flow through the rotor. First, a validation study was carried out to check the capability of the selected CFD in modeling unsteady turbine stage flows. Time-accurate solutions were achieved and the results agreed well with the available experimental measurements. Based on the validation, two expanded case studies were carried out to investigate the “species streak” effects on the secondary flow and heat transfer in turbine rotor passages. It was found that the “species streak” could generate “hot streak enhancement structure” as well as “baroclinic torque structure” in rotor passages, which would work with the inherent secondary flow structures in rotor to determine its heat transfer. It was also found that the contributions of the baroclinic torque source term could have magnitudes comparable to other effects, such as vortex stretching, in creating secondary flows. In some circumstances, however, the overall effects of the baroclinic torque could be partially reduced by opposite vortex stretching effects generated by the same density gradients.

A metastable wet steam turbine stage model

2002 ◽  
Vol 216 (1-3) ◽  
pp. 113-119 ◽  
Author(s):  
Wageeh Sidrak Bassel ◽  
Arivaldo Vicente Gomes
Keyword(s):  
Steam Turbine ◽  
Stage Model ◽  
Wet Steam ◽  
Turbine Stage

Effect of Wake Passing on Unsteady Aerodynamic Performance in a Turbine Stage

2006 ◽  
Author(s):  
K. Yamada ◽  
K. Funazaki ◽  
K. Hiroma ◽  
M. Tsutsumi ◽  
Y. Hirano ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Suction Side ◽  
Turbine Stage ◽  
Three Dimensional Flow ◽  
Unsteady Aerodynamic ◽  
Unsteady Effect ◽  
Unsteady Rans ◽  
Wake Passing ◽  
Stage Efficiency

In the present work, unsteady RANS simulations were performed to clarify several interesting features of the unsteady three-dimensional flow field in a turbine stage. The unsteady effect was investigated for two cases of axial spacing between stator and rotor, i.e. large and small axial spacing. Simulation results showed that the stator wake was convected from pressure side to suction side in the rotor. As a result, another secondary flow, which counter-rotated against the passage vortices, was periodically generated by the stator wake passing through the rotor passage. It was found that turbine stage efficiency with the small axial spacing was higher than that with the large axial spacing. This was because the stator wake in the small axial spacing case entered the rotor before mixing and induced the stronger counter-rotating vortices to suppress the passage vortices more effectively, while the wake in the large axial spacing case eventually promoted the growth of the secondary flow near the hub due to the migration of the wake towards the hub.

Integrated Large Eddy Simulation of Combustor and Turbine Interactions: Effect of Turbine Stage Inlet Condition

2017 ◽  
Author(s):  
Florent Duchaine ◽  
Jérôme Dombard ◽  
Laurent Gicquel ◽  
Charlie Koupper
Keyword(s):  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Rotor Blade ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Stator Vane ◽  
Specific Configuration ◽  
Inlet Conditions

To study the effects of combustion chamber dynamics on a turbine stage aerodynamics and thermal loads, an integrated Large-Eddy Simulation of the FACTOR combustion chamber simulator along with its high pressure turbine stage is performed and compared to a standalone turbine stage computation operated under the same mean conditions. For this specific configuration, results illustrate that the aerodynamic expansion of the turbine stage is almost insensitive to the inlet turbulent conditions. However, the temperature distribution in the turbine passages as well as on the stator vane and rotor blade walls are highly impacted by these inlet conditions: underlying the importance of inlet conditions in turbine stage computations and the potential of integrated combustion chamber / turbine simulations in such a context.

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