The Effects of Secondary Flow and Passive Injection on the Motion of Solid Particles Entrained in Flow Through a Curved Converging Channel

1999 ◽  
Vol 121 (2) ◽  
pp. 359-364
Author(s):  
James J. Ventresca ◽  
Wilfred T. Rouleau
Keyword(s):  
Secondary Flow ◽  
Boundary Layers ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Solid Particles ◽  
Surface Boundary ◽  
Suction Surface ◽  
Particle Trajectories ◽  
Flow Through

The three-dimensional effects of secondary flow, passive injection, and particle size on the motion of solid particles entrained in a laminar, incompressible flow through a curved, converging, rectangular passage were numerically investigated. Emphasis was placed on observing the physical mechanisms that cause particles 5 μm and smaller in diameter to deposit on passage surfaces and to concentrate near the endwalls and mid-span at the passage exit. Particle trajectories were calculated for 5, 30, and 300 μm diameter solid particles. It was observed that the paths of 5 μm particles were similar to the streamlines of the three-dimensional flow in the channel until the particles encountered the boundary layers on the blade surfaces and endwalls, where they would graze the surfaces (contributing to particle deposition) and concentrate at the exit of the channel. Particles of 30 μm diameter, however, were only slightly affected by secondary flows, but were affected enough to be made to concentrate at the exit near the endwall and mid-span surfaces. Particles of 300 μm diameter were not affected by secondary flows at all. The particle trajectories showed that the passage secondary flow convected particles across endwalls toward the pressure and suction surface boundary layers of the blades. It was observed that small particles were made to decelerate and/or concentrate in the boundary layers near the passage exit. It was found that this concentration of particles along the suction surface and endwalls could be significantly reduced by means of passive injection. (Passive injection is a method of inducing the flow of jets in the curved portion of an airfoil shaped surface due to the pressure difference on opposing sides. This is accomplished by means of holes or slots that have been drilled through the surface at strategic locations.)

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.

New Methods for Secondary Flow Phenomena Visualization and Analysis

2019 ◽  
Author(s):  
Mattia Straccia ◽  
Rodolfo Hofmann ◽  
Volker Gümmer
Keyword(s):  
Secondary Flow ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Secondary Flows ◽  
Tip Leakage ◽  
Ansys Cfx ◽  
Flow Phenomena ◽  
Visualization Techniques ◽  
Operating Points

Abstract This work focuses on presenting new techniques for the visualization of Secondary Flow Phenomena (SFP) in transonic turbomachinery. Here, Rotor 37 has been used to develop and apply these techniques in order to study vortices, shocks and secondary flows. They are also used to provide a comparison between turbulence models in Ansys CFX environment, here the Spalart-Allmaras (SA) and Shear Stress Tensor (SST) turbulence models. The scope of this paper is to give an improved understanding of SFP and how their onset and evolution are influenced from the turbulence model. The analysis is based on results of three-dimensional steady-state RANS simulations, for operating points between design point and near-stall condition, achieved by varying the outlet static pressure radial equilibrium distribution at the rotor exit. The new visualization techniques highlight important flow field features less investigated in previous research works, in particular secondary weak strength vortices. They will give a better visualization of and insight to the interaction of the passage shock and the tip leakage vortex, the interaction between vortices and boundary layers and the interaction of the shock wave and endwall boundary layers.

Visualization Study of Flow in Axial Flow Inducer

1972 ◽  
Vol 94 (4) ◽  
pp. 777-787 ◽  
Author(s):  
B. Lakshminarayana
Keyword(s):  
Radial Velocity ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Theory ◽  
Secondary Flows ◽  
Flow Coefficient ◽  
Flow Through

A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory. Based on these investigations, methods of modeling the flow are discussed.

Three-Dimensional Blade Boundary Layer and Endwall Flow Development in the Nozzle Passage of a Single Stage Turbine

1998 ◽  
Vol 120 (3) ◽  
pp. 570-578 ◽  
Author(s):  
D. Ristic ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Region ◽  
Radial Pressure ◽  
Suction Surface ◽  
Field Development ◽  
Dimensional Boundary

The three-dimensional viscous flow field development in the nozzle passage of an axial flow turbine stage was measured using a “x” hot-wire probe. The measurements were carried out at two axial stations on the endwall and vane surfaces and at several spanwise and pitchwise locations. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. The boundary layers on the vane surface were found to be very thin and mostly laminar, except on the suction surface downstream of 70 percent axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong radial flow velocities in the trailing edge regions of the blade. On the endwalls, the boundary layers were much thicker, especially near the suction corner of the casing surface, caused by the secondary flow. The secondary flow region near the suction surface-casing corner indicated the presence of the passage vortex detached from the vane surface. The boundary layer code accurately predicts the three-dimensional boundary layers on both vane surfaces and endwall in the regions where the influence of the secondary flow is small.

Three-Dimensional Blade Boundary Layer and Endwall Flow Development in the Nozzle Passage of a Single Stage Turbine

1996 ◽  
Author(s):  
D. Ristic ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Region ◽  
Radial Pressure ◽  
Blade Surface ◽  
Suction Surface ◽  
Field Development

The three-dimensional viscous flow field development in the nozzle passage of an axial flow turbine stage was measured using a “x” hot-wire probe. The measurements were carried out at one axial station on the endwall and blade surfaces and at several spanwise and pitchwise locations. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. The boundary layers on the blade surface were found to be very thin and laminar, except on the suction surface downstream of 70% axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong radial flow velocities in the trailing edge regions of the blade. On the endwalls, the boundary layers were turbulent and much thicker, especially near the suction corner of the casing surface, caused by the secondary flow. The secondary flow region near the suction casing surface corner indicated the presence of the passage vortex detached from the blade surface. The boundary layer code accurately predicts the three-dimensional boundary layers on both vane surfaces in regions where the influence of secondary flow is small.

scholarly journals The Calculation of the Three-Dimensional Flow Through a Transonic Fan Including the Effects of Blade Surface Boundary Layers, Part-Span Shroud, Engine Splitter and Adjacent Blade Rows

1989 ◽  
Author(s):  
R. D. Cedar ◽  
D. G. Holmes
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Surface Boundary ◽  
Blade Surface ◽  
Three Dimensional Flow ◽  
Blade Passage ◽  
Flow Through ◽  
Euler Solver ◽  
Transonic Fan

In the past, predictions of the three-dimensional flow through turbomachinery blades have often assumed that:- a) The blade passage forms a single channel. b) The effects of adjacent blade rows and engine structures are negligible. c) The flow is inviscid. Unfortunately, for a transonic fan in a high bypass ratio aero-engine, these assumptions are poor because:- a) The blade passage is split into a number of channels by the part-span shroud and the engine splitter. b) The fan aerodynamics may be influenced by the presence of the engine splitter and downstream blade rows. c) The blockage due to the blade surface boundary layers can have a significant effect on the shock structure. This paper describes the extensions that have been made to the three-dimensional Euler solver developed by Holmes and Tong (1985) in order to remove the assumptions listed above. The problem of modeling the part-span shroud and the engine splitter has been generalized to that of solving a flow containing any number of internal solid bodies. This has been achieved in a novel manner that allows the finite volume scheme to be fully vectorized and the multigrid acceleration technique to be implemented efficiently. The effect of adjacent blade rows has been modeled using passage averaged mass, momentum and energy source terms to represent the neighboring blades in a similar manner to that described by Adamczyk, Mulac and Celestina (1986). The blade surface boundary layers have been modeled using a series of two-dimensional boundary layer calculations coupled to the Euler solver using a transpiration model to account for the boundary layer displacement thickness. To demonstrate the capabilities of this program, results from the analysis of a General Electric advanced fan blade design, with a part-span shroud, engine splitter and down-stream stator and rotor blade are presented. This is followed by an investigation and discussion of the individual effect of not modeling the viscous blockage, the part-span shroud engine, splitter and down-stream blade rows. It is concluded that if an accurate prediction of the fan aerodynamics is to be obtained all these features must be modeled.

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.

A Three-Dimensional Analysis of Particle Deposition for the Modified Chemical Vapor Deposition (MCVD) Process

1992 ◽  
Vol 114 (3) ◽  
pp. 735-742 ◽  
Author(s):  
Y. T. Lin ◽  
M. Choi ◽  
R. Greif
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Particle Deposition ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Secondary Flows ◽  
Circumferential Direction ◽  
Forced Flow ◽  
Flow Rates ◽  
Entry Length

A study has been made of the deposition of particles that occurs during the modified chemical vapor deposition (MCVD) process. The three-dimensional conservation equations of mass, momentum, and energy have been solved numerically for forced flow, including the effects of buoyancy and variable properties in a heated, rotating tube. The motion of the particles that are formed is determined from the combined effects resulting from thermophoresis and the forced and secondary flows. The effects of torch speed, rotational speed, inlet flow rate, tube radius, and maximum surface temperature on deposition are studied. In a horizontal tube, buoyancy results in circumferentially nonuniform temperature and velocity fields and particle deposition. The effect of tube rotation greatly reduces the nonuniformity of particle deposition in the circumferential direction. The process is chemical-reaction limited at larger flow rates and particle-transport limited at smaller flow rates. The vertical tube geometry has also been studied because its symmetric configuration results in uniform particle deposition in the circumferential direction. The “upward” flow condition results in a large overall deposition efficiency, but this is also accompanied by a large “tapered entry length.”

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.

scholarly journals The Design and Evaluation of a 14 Stage, 16:1 Pressure Ratio Compressor for an Industrial Gas Turbine

1996 ◽  
Author(s):  
Mohammad R. Saadatmand
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Suction Surface ◽  
Design Intent ◽  
Flow Through ◽  
Industrial Gas Turbine

The aerodynamic design process leading to the production configuration of a 14 stage, 16:1 pressure ratio compressor for the Taurus 70 gas turbine is described. The performance of the compressor is measured and compared to the design intent. Overall compressor performance at the design condition was found to be close to design intent. Flow profiles measured by vane mounted instrumentation are presented and discussed. The flow through the first rotor blade has been modeled at different operating conditions using the Dawes (1987) three-dimensional viscous code and the results are compared to the experimental data. The CFD prediction agreed well with the experimental data across the blade span, including the pile up of the boundary layer on the corner of the hub and the suction surface. The rotor blade was also analyzed with different grid refinement and the results were compared with the test data.

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