scholarly journals Secondary Flow Effects and Mixing of the Wake Behind a Turbine Stator

1982 ◽  
Author(s):  
A. Binder ◽  
R. Romey
Keyword(s):  
Secondary Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Detailed Knowledge ◽  
Pressure Loss Coefficient ◽  
Turbine Stator ◽  
Dimensional Measurements ◽  
Order Of Magnitude ◽  
Flow Effects ◽  
Secondary Vortices

In highly loaded turbines with large hub/tip ratios there is a marked increase in secondary flow effects. The optimization of the turbine flow requires detailed knowledge both of three-dimensional cascade flow and of the wake impinging on the downstream rows of airfoils. Therefore, in the DFVLR, thorough investigations of a single-stage turbine with cold air flow were performed. The stator of this turbine was designed for transonic flow and has a hub/tip ratio of 0.756 and an aspect ratio of 0.56. First, measurements were taken without the rotor in several sections behind the turbine stator with special regard to the mixing of the wakes and secondary vortices. Distributions of total pressure loss coefficient and flow direction give the order of magnitude of the mixing losses. Also, position, intensity, structure, and development of secondary vortices are shown. Some complementary measurements were carried out using five-hole probes. They confirm the above described results from two-dimensional measurements.

Secondary Flow Effects and Mixing of the Wake Behind a Turbine Stator

1983 ◽  
Vol 105 (1) ◽  
pp. 40-46 ◽  
Author(s):  
A. Binder ◽  
R. Romey
Keyword(s):  
Secondary Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Detailed Knowledge ◽  
Pressure Loss Coefficient ◽  
Turbine Stator ◽  
Dimensional Measurements ◽  
Order Of Magnitude ◽  
Flow Effects ◽  
Secondary Vortices

In highly loaded turbines with large hub/tip ratios there is a marked increase in secondary flow effects. The optimization of the turbine flow requires detailed knowledge both of three-dimensional cascade flow and of the wake impinging on the downstream rows of airfoils. Therefore, in the DFVLR, thorough investigations of a single-stage turbine with cold air flow were performed. The stator of this turbine was designed for transonic flow and has a hub/tip ratio of 0.756 and an aspect ratio of 0.56. First, measurements were taken without the rotor in several sections behind the turbine stator with special regard to the mixing of the wakes and secondary vortices. Distributions of total pressure loss coefficient and flow direction give the order of magnitude of the mixing losses. Also, position, intensity, structure, and development of secondary vortices are shown. Some complementary measurements were carried out using five-hole probes. They confirm the above described results from two-dimensional measurements.

End-Wall Film Cooling Through Fan-Shaped Holes With Different Area Ratios

2006 ◽  
Vol 129 (2) ◽  
pp. 212-220 ◽  
Author(s):  
Giovanna Barigozzi ◽  
Giuseppe Franchini ◽  
Antonio Perdichizzi
Keyword(s):  
Secondary Flow ◽  
Mass Flow ◽  
Film Cooling ◽  
Three Dimensional ◽  
Wide Band ◽  
Lateral Spreading ◽  
Area Ratio ◽  
Adiabatic Effectiveness ◽  
Flow Effects ◽  
End Wall

The present paper reports on the aerothermal performance of a nozzle vane cascade, with film-cooled end walls. The coolant is injected through four rows of cylindrical holes with conical expanded exits. Two end-wall geometries with different area ratios have been compared. Tests have been carried out at low speed (M=0.2), with coolant to mainstream mass flow ratio varied in the range 0.5–2.5%. Secondary flow assessment has been performed through three-dimensional (3D) aerodynamic measurements, by means of a miniaturized five-hole probe. Adiabatic effectiveness distributions have been determined by using the wide-band thermochromic liquid crystals technique. For both configurations and for all the blowing conditions, the coolant share among the four rows has been determined. The aerothermal performances of the cooled vane have been analyzed on the basis of secondary flow effects and laterally averaged effectiveness distributions; this analysis was carried out for different coolant mass flow ratios. It was found that the smaller area ratio provides better results in terms of 3D losses and secondary flow effects; the reason is that the higher momentum of the coolant flow is going to better reduce the secondary flow development. The increase of the fan-shaped hole area ratio gives rise to a better coolant lateral spreading, but appreciable improvements of the adiabatic effectiveness were detected only in some regions and for large injection rates.

A Geometry Generation Framework for Contoured Endwalls

2019 ◽  
Author(s):  
L. E. Wood ◽  
R. R. Jones ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
D. A. S. Rees ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Aerodynamic Loss ◽  
Construction Methods ◽  
Novel Approach ◽  
Wide Range ◽  
Blade Row ◽  
Flow Features ◽  
Flow Effects ◽  
Geometric Variation

Abstract The mainstream, or primary, flow in a gas turbine annulus is characteristically two-dimensional over the mid-span region of the blading, where the radial flow is almost negligible. Contrastingly, the flow in the endwall and tip regions of the blading is highly three-dimensional, characterised by boundary layer effects, secondary flow features and interaction with cooling flows. Engine designers employ geometric contouring of the endwall region in order to reduce secondary flow effects and subsequently minimise their contribution to aerodynamic loss. Such is the geometric variation of vane and blade profiles — which has become a proprietary art form — the specification of an effective endwall geometry is equally unique to each blade-row. Endwall design methods, which are often directly coupled to aerodynamic optimisers, are widely developed to assist with the generation of contoured surfaces. Most of these construction methods are limited to the blade-row under investigation, while few demonstrate the controllability required to offer a universal platform for endwall design. This paper presents a Geometry Generation Framework (GGF) for the generation of contoured endwalls. The framework employs an adaptable meshing strategy, capable of being applied to any vane or blade, and a versatile function-based approach to defining the endwall shape. The flexibility of this novel approach is demonstrated by recreating a selection of endwalls from the literature, which were selected for their wide-range of contouring approaches.

Ponded infiltration into soil with biopores — field experiment and modeling

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Michal Dohnal ◽  
Jaromír Dušek ◽  
Tomáš Vogel ◽  
Milena Císlerová ◽  
Ľubomír Lichner ◽  
...  
Keyword(s):  
Water Flow ◽  
Preferential Flow ◽  
Water Pressure ◽  
Three Dimensional ◽  
Detailed Knowledge ◽  
Dye Tracer ◽  
Simulation Based ◽  
Flow Through ◽  
Flow Effects ◽  
Infiltration Experiment

AbstractPreferential movement of water in macropores plays an important role when the process of ponded infiltration in natural porous systems is studied. For example, the detailed knowledge of water flow through macropores is of a major importance when predicting runoff responses to rainfall events. The main objectives of this study are to detect preferential movement of water in Chernozem soil and to employ numerical modeling to describe the variably saturated flow during a field ponded infiltration experiment. The infiltration experiment was performed at the Macov experimental station (Calcari-Haplic Chernozem in Danubian Lowland, Slovakia). The experiment involved single ring ponded infiltration. At the quasi steady state phase of the experiment dye tracer was added to the infiltrating water. Then the soil profile was excavated and the penetration pattern of the applied tracer was recorded. The abundance of biopores as a product of fauna and flora was found. To quantify the preferential flow effects during the infiltration experiment, three-dimensional axisymmetric simulations were carried out by a two-dimensional dual-continuum numerical model. The water flow simulations based on measured hydraulic characteristics without consideration of preferential flow effects failed to describe the infiltration experiment adequately. The 3D axisymmetric simulation based on dual-permeability approach provided relatively realistic space-time distribution of soil water pressure below the infiltration ring.

Comparison of Sweep and Dihedral Effects on Compressor Cascade Performance

1998 ◽  
Vol 120 (3) ◽  
pp. 454-463 ◽  
Author(s):  
T. Sasaki ◽  
F. Breugelmans
Keyword(s):  
Secondary Flow ◽  
Parametric Study ◽  
Three Dimensional ◽  
High Energy ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Upstream Direction ◽  
Dimensional Measurements ◽  
Linear Compressor Cascade

The influence of two stacking lines, namely sweep and dihedral, has been investigated in a linear compressor cascade. Both types of blade considered are symmetric about midspan and consist of a straight central section with either swept or dihedral sections toward the endwalls. Two types of experiment have been carried out. First, a parametric study was performed by changing both the magnitude and the extent of the sweep or dihedral. In the case of swept blades, those with forward sweep (SWF), for which the stacking line is swept in the upstream direction toward the endwall, were found to have better performance than backward-swept blades. Subsequently, four sets of SWFs were compared. In the case of dihedral blades, it is well known that the dihedral is advantageous when the angle between the suction surface and the endwall is obtuse, i.e., positive dihedral. Thus, four sets of positive dihedral blades (DHP) were compared. In both SWF and DHP blades, those configurations that have better efficiency than straight blades were determined. Second, detailed three-dimensional measurements inside the blade passage were performed in the cases that showed the best performance in the parametric study. Both SWF and DHP showed significant effects on the flowfield. In the SWF case, a vortex, which has the opposite sense to the passage vortex, was observed in the forward portion inside the blade passage. This vortex supplies high-energy fluid to the endwall region and reduces the corner stall. The secondary flow is greatly reduced. In the DHP, the blade loading was reduced at the endwall and increased at the midspan. Reduction of the corner stall and the secondary flow was also observed.

scholarly journals An Investigation of Spanwise Mixing in Multistage Axial Flow Compressors

1992 ◽  
Author(s):  
S.-M. Li ◽  
M.-Z. Chen
Keyword(s):  
Secondary Flow ◽  
Turbulent Diffusion ◽  
Flow Model ◽  
Three Dimensional ◽  
Axial Flow ◽  
Equation System ◽  
Meridional Flow ◽  
Flow Effects ◽  
Annular Cascade ◽  
Axial Flow Compressors

An equation system has been deduced for meridional throughflow fields of multistage axial flow compressors, presenting different kinds of spanwise mixing effects of the fields in a unified form. The spanwise mixing in compressors is caused by three kinds of effects, molecular motion, turbulent diffusion, and circumferential non–uniformities, the last of which includes secondary flow effects and others. This equation system thus unifies the two models for spanwise mixing analyses by Adkins & Smith (1981) and Gallimore & Cumpsty (1986). The turbulent diffusion in the two–dimensional (2–D) meridional fields is determined by complex three–dimensional (3–D) shear flows in compressors, rather than the 2–D shearing alone, so a turbulence model for 2–D meridional flow calculations is proposed on the basis of a simplified 3–D shearing structure in compressors. The circumferentially non–uniform correlation terms in the equation system have been modeled on the basis of Adkins and Smith (1981) secondary flow model and the experimental data for annular cascade wakes. The results obtained agree well with the experiments for five compressors. The results also show some improvement over the previous theories.

Measuring Particle Positions in Micro Channel with Multifiber Array

2013 ◽  
Vol 25 (6) ◽  
pp. 1105-1113
Author(s):  
Ichiro Okuda ◽  
◽  
Yasushi Mae ◽  
Kenichi Ohara ◽  
Tomohito Takubo ◽  
...  
Keyword(s):  
Laser Light ◽  
Flow Direction ◽  
Three Dimensional ◽  
Micro Channel ◽  
Position Measurement ◽  
Micro Channels ◽  
Dimensional Measurements ◽  
Vertically Aligned ◽  
Pdms Chip ◽  
Different Diameters

This paper proposes position measurement of particles in micro channels fabricated on a polydimethylsiloxane (PDMS) chip using a two-layer plastic optical fiber (POF) array. Particle positions are measured by irradiating the POF array with laser light and measuring the decrease in POF output power posed by the presence of the particle. Our proposed sensor provides three dimensional measurements in the micro channel along the directions of the length, depth and the width. We demonstrate that plural particles of different diameters can be measured with our proposed sensor in which two layers of POF are vertically aligned or shifted along the flow direction. The effects of optical misalignment of POF array with respect to the measurement are theoretically and experimentally evaluated.

Computational Analysis of Pitch-Width Effects on the Secondary Flows of Turbine Blades

2002 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano ◽  
B. Marini
Keyword(s):  
Secondary Flow ◽  
Turbine Blade ◽  
Compressible Flows ◽  
Turbine Blades ◽  
Time Derivative ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Width Ratio ◽  
Blade Row ◽  
Flow Effects

A three-dimensional computational code was developed for solving time-averaged flows within a turbine blade row using a novel time-marching method. A concept of incorporating dissipation terms into the time derivative terms was proposed to allow the code to have the capability of handling both incompressible and compressible flows. The code was validated by comparing the computational results with experiments in a turbine stator blade passage. The code was further used to investigate the influence of secondary flow in a turbine blade row due to different pitch-width ratios. Detailed secondary flows as well as loss profiles in different sizes of root pitch-width ratio are presented and discussed. The results of this study provide useful information for evaluation of the secondary flow effects due to the pitch-width ratio influence for the future new turbine blade designs.

Numerical Study of the Flow Past an Axial Turbine Stator Casing and Perspectives for its Management

2017 ◽  
Author(s):  
Hakim T. K. Kadhim ◽  
Aldo Rona ◽  
Hayder M. B. Obaida ◽  
J. Paul Gostelow
Keyword(s):  
Secondary Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Design Tool ◽  
Flow Strength ◽  
Ansys Fluent ◽  
Axial Turbine ◽  
Pressure Loss Coefficient ◽  
Flow Losses ◽  
End Wall

The interaction of secondary flow with the main passage flow results in entropy generation; this accounts for considerable losses in turbomachines. Low aspect ratio blades in an axial turbine lead to a high degree of secondary flow losses. A particular interest is the reduction in secondary flow strength at the turbine casing, which adversely affects the turbine performance. This paper presents a selective review of effective techniques for improving the performance of axial turbines by turbine end wall modifications. This encompasses the use of axisymmetric and non-axisymmetric end wall contouring and the use of fences. Specific attention is given to non-axisymmetric end walls and to their effect on secondary flow losses. A baseline three-dimensional steady RANS k-ω SST model, with axisymmetric walls, is validated against experimental measurements from the Institute of Jet Propulsion and Turbomachinery at the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, Germany, with comparative solutions generated by ANSYS Fluent and OpenFOAM. The predicted performance of the stator passage with an axisymmetric casing is compared with that from using a contoured casing with a groove designed using the Beta distribution function for guiding the groove shape. The prediction of a reduced total pressure loss coefficient with the application of the contoured casing supports the groove design approach based on the natural path of the secondary flow features. This work also provided an automated workflow process, linking surface definition in MATLAB, meshing in ICEM CFD, and flow solving and post-processing OpenFOAM. This has generated a casing contouring design tool with a good portability to industry, to design and optimize new turbine blade passages.

Secondary Flow Effects in a Bounded Rectangular Jet

1968 ◽  
Vol 90 (2) ◽  
pp. 241-248 ◽  
Author(s):  
J. F. Foss ◽  
J. B. Jones
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Flow Structure ◽  
Flow Model ◽  
Three Dimensional ◽  
Dimensional Effects ◽  
Rectangular Jet ◽  
Secondary Flow Structure ◽  
Flow Effects

The isotach pattern in a bounded jet with an aspect ratio of 6 suggests the presence of a secondary flow structure. A physical flow model is presented, and further measurements substantiate the model and support the conclusion that three-dimensional effects are highly significant in bounded jets of modest aspect ratio, even in the mid plane between the bounding walls.

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