Three-Dimensional Internal Flows in Turbomachinery. Task 1. Secondary Flow in Diffusing Cascades.

1979 ◽  
Author(s):  
Awatef A. Hamed
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Internal Flows

scholarly journals Incidence Angle and Pitch-Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1992 ◽  
Author(s):  
A. Perdichizzi ◽  
V. Dossena
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Oil Flow ◽  
Secondary Velocity ◽  
Secondary Flow Field

This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 degrees, and for three pitch-chord ratios: s/c = 0.58,0.73,0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five hole probe in a plane located at 50% of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots show in detail how much the secondary flow field is modified both by incidence and cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch averaged loss and of the deviation angle, when incidence or pitch-chord ratio is varied.

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.

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.

scholarly journals The Design of an Improved Endwall Film-Cooling Configuration

1998 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Aerodynamic Loss ◽  
Cooling Flow ◽  
High Static Pressure ◽  
Endwall Film Cooling ◽  
Aerodynamic Losses

The endwall film-cooling cooling configuration investigated by Friedrichs et al. (1996, 1997) had in principle sufficient cooling flow for the endwall, but in practice, the redistribution of this coolant by secondary flows left large endwall areas uncooled. This paper describes the attempt to improve upon this datum cooling configuration by redistributing the available coolant to provide a better coolant coverage on the endwall surface, whilst keeping the associated aerodynamic losses small. The design of the new, improved cooling configuration was based on the understanding of endwall film-cooling described by Friedrichs et al. (1996, 1997). Computational fluid dynamics were used to predict the basic flow and pressure field without coolant ejection. Using this as a basis, the above described understanding was used to place cooling holes so that they would provide the necessary cooling coverage at minimal aerodynamic penalty. The simple analytical modelling developed in Friedrichs et al. (1997) was then used to check that the coolant consumption and the increase in aerodynamic loss lay within the limits of the design goal. The improved cooling configuration was tested experimentally in a large scale, low speed linear cascade. An analysis of the results shows that the redesign of the cooling configuration has been successful in achieving an improved coolant coverage with lower aerodynamic losses, whilst using the same amount of coolant as in the datum cooling configuration. The improved cooling configuration has reconfirmed conclusions from Friedrichs et al. (1996, 1997); firstly, coolant ejection downstream of the three-dimensional separation lines on the endwall does not change the secondary flow structures; secondly, placement of holes in regions of high static pressure helps reduce the aerodynamic penalties of platform coolant ejection; finally, taking account of secondary flow can improve the design of endwall film-cooling configurations.

The Elliptic Solution of the Secondary Flow Problem

1983 ◽  
Vol 105 (3) ◽  
pp. 530-535 ◽  
Author(s):  
S. Abdallah ◽  
A. Hamed
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Elliptic Solution ◽  
Dimensional Flow ◽  
Flow Vorticity ◽  
Dependent Variables ◽  
Two Dimensional Flow ◽  
Uniqueness Of The Solution

This paper presents the elliptic solution of the inviscid incompressible secondary flow in curved passages. The three-dimensional flow field is synthesized between 3 sets of orthogonal nonstream surfaces. The two-dimensional flow field on each set of surfaces is considered to be resulting from a source/sink distribution. The distribution and strength of these sources are dependent on the variation in the flow properties normal to the surfaces. The dependent variables in this formulation are the velocity components, the total pressure, and the main flow vorticity component. The governing equations in terms of these dependent variables are solved on each family of surfaces using the streamlike function formulation. A new mechanism is implemented to exchange information between the solutions on the three family surfaces, resulting into a unique solution. In addition, the boundary conditions for the resulting systems of equations are carefully chosen to insure the existence and uniqueness of the solution. The numerical results obtained for the rotational inviscid flow in a curved duct are discussed and compared with the available experimental data.

Analysis of the effect of the size of three-dimensional micro-geometric structures on physical adhesion phenomena using microprint technique

2018 ◽  
Vol 41 (5) ◽  
pp. 277-283 ◽  
Author(s):  
Akiko Oota-Ishigaki ◽  
Toru Masuzawa ◽  
Kazuaki Nagayama
Keyword(s):  
Shear Rate ◽  
Secondary Flow ◽  
Thrombus Formation ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Quantitative Relationship ◽  
Bottom Surface ◽  
Material Surface ◽  
Computational Fluid Dynamics Analysis ◽  
Biomaterial Surfaces

Thrombus formation on biomaterial surfaces with microstructures is complex and not fully understood. We have studied the micro-secondary flow around microstructures that causes components of blood to adhere physically in a low Reynolds number region. The purpose of this study was to investigate the effect of micro-column size on the adhesion phenomena and show a quantitative relationship between the micro-secondary flow and physical adhesion phenomena, considering microstructures of various sizes. The flow simulation and quantitative assessment of adhesion rates around micro-columns was conducted using four sizes of micro-columns. This study also calculated the vectors of micro-secondary flow and average shear rate around a micro-column using a computational fluid dynamics analysis. The simulation showed the micro-secondary flow toward the bottom surface at upstream side and low shear rate distribution generated around a micro-column. Furthermore, physical adhesion tests were conducted using microbeads and a perfusion circuit to examine the size effect of the micro-columns on the physical adhesion. The results showed that the average adhesion rate around the micro-column increases with the associated size increase of the micro-column. Our results indicate that quantification of micro-secondary flow on a material surface with microstructures of several sizes and shapes (such as in a rough surface) is important for the evaluation of the adhesion phenomenon even though the surface roughness value on the material surface is small.

scholarly journals Numerical simulation of complex 3D compressible viscous flows through rotating blade passage

2003 ◽  
pp. 55-82
Author(s):  
M. Despotovic ◽  
Milun Babic ◽  
D. Milovanovic ◽  
Vanja Sustersic
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Convergence Acceleration ◽  
Design Tool ◽  
Navier Stokes ◽  
Internal Flows ◽  
Navier Stokes Equations ◽  
Rotating Blade ◽  
Compressible Viscous Flows

This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech?nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design tool. The mathematical model is based on System of Favre averaged Navier-Stokes equations that are written in relative frame of reference, which rotates with constant angular velocity around axis of rotation. The governing equations are solved using finite vol?ume method applied on structured grids. The numerical procedure is based on the explicit multistage Runge-Kutta scheme that is coupled with modem numerical procedures for convergence acceleration. To demonstrate the accuracy of the described numer?ical method developed software is applied to numerical analysis of flow through impeller of axial turbocompressor, and obtained results are compared with available experimental data.

Design Optimization of Profiled Endwall With Consideration of Cooling and Rim Seal Flow Effects

2016 ◽  
Author(s):  
Huimin Tang ◽  
Shuaiqiang Liu ◽  
Hualing Luo
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Great Influence ◽  
Optimization Procedure ◽  
Secondary Flows ◽  
High Pressure Turbine ◽  
Operation Condition ◽  
Turbine Performance

Profiled endwall is an effective method to improve aerodynamic performance of turbine. This approach has been widely studied in the past decade on many engines. When automatic design optimisation is considered, most of the researches are usually based on the assumption of a simplified simulation model without considering cooling and rim seal flows. However, many researchers find out that some of the benefits achieved by optimization procedure are lost when applying the high-fidelity geometry configuration. Previously, an optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM. This optimization procedure has been executed [12] to design profiled endwalls for a turbine cascade and a one-and-half stage axial turbine. Improvements of the turbine performance have been achieved. As the profiled endwall is applied to a high pressure turbine, the problems of cooling and rim seal flows should be addressed. In this work, the effects of rim seal flow and cooling on the flow field of two-stage high pressure turbine have been presented. Three optimization runs are performed to design the profiled endwall of Rotor-One with different optimization model to consider the effects of rim flow and cooling separately. It is found that the rim seal flow has a significant impact on the flow field. The cooling is able to change the operation condition greatly, but barely affects the secondary flow in the turbine. The influences of the profiled endwalls on the flow field in turbine and cavities have been analyzed in detail. A significant reduction of secondary flows and corresponding increase of performance are achieved when taking account of the rim flows into the optimization. The traditional optimization mechanism of profiled endwall is to reduce the cross passage gradient, which has great influence on the strength of the secondary flow. However, with considering the rim seal flows, the profiled endwall improves the turbine performance mainly by controlling the path of rim seal flow. Then the optimization procedure with consideration of rim seal flow has also been applied to the design of the profiled endwall for Stator Two.

Analysis of Buoyancy and Tube Rotation Relative to the Modified Chemical Vapor Deposition Process

1990 ◽  
Vol 112 (4) ◽  
pp. 1063-1069 ◽  
Author(s):  
M. Choi ◽  
Y. T. Lin ◽  
R. Greif
Keyword(s):  
Secondary Flow ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Horizontal Tube ◽  
Deposition Process ◽  
Secondary Flows ◽  
Secondary Motion

The secondary flows resulting from buoyancy effects in respect to the MCVD process have been studied in a rotating horizontal tube using a perturbation analysis. The three-dimensional secondary flow fields have been determined at several axial locations in a tube whose temperature varies in both the axial and circumferential directions for different rotational speeds. For small rotational speeds, buoyancy and axial convection are dominant and the secondary flow patterns are different in the regions near and far from the torch. For moderate rotational speeds, the effects of buoyancy, axial and angular convection are all important in the region far from the torch where there is a spiraling secondary flow. For large rotational speeds, only buoyancy and angular convection effects are important and no spiraling secondary motion occurs far downstream. Compared with thermophoresis, the important role of buoyancy in determining particle trajectories in MCVD is presented. As the rotational speed increases, the importance of the secondary flow decreases and the thermophoretic contribution becomes more important. It is noted that thermophoresis is considered to be the main cause of particle deposition in the MCVD process.

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