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.

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.

Secondary Flows in a Transonic Cascade: Comparison Between Experimental and Numerical Results

1989 ◽  
Vol 111 (4) ◽  
pp. 369-377 ◽  
Author(s):  
F. Bassi ◽  
C. Osnaghi ◽  
A. Perdichizzi ◽  
M. Savini
Keyword(s):  
Experimental Data ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Numerical Results ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Flow Angle ◽  
Flow Phenomena ◽  
Contour Plots ◽  
Flow Vortex

The paper presents a comparison between numerical results and experimental data about the secondary flow development in a linear transonic turbine cascade. Computations are carried out by using a three-dimensional inviscid Euler code, based on a Runge-Kutta explicit finite volume method. The experimental inlet total pressure distribution is imposed as inlet boundary condition to simulate the incoming endwall boundary layer. The comparison is made in four planes downstream of the cascade where detailed experimental data obtained in a transonic wind tunnel are available. For each of these planes secondary velocities and streamwise vorticity contour plots are presented and discussed. Moreover pitchwise mass averaged flow angle distributions showing overturning and underturning regions are shown. The comparison shows that an Euler code can predict the essential features of secondary flow phenomena like passage vortex location and intensity but a certain disagreement is found in the overturning and underturning angles evaluation. Numerical results also allow for the investigation of the development of secondary flows inside the blade channel. The investigation is carried out for three different Mach numbers: M2is = 0.5, 1.02, 1.38, in order to show the influence of compressibility on the flow vortex structure.

A Numerical Study of Secondary Flow in Axial Turbines With Application to Radial Transport of Hot Streaks

2000 ◽  
Author(s):  
Dilip Prasad ◽  
Gavin J. Hendricks
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Study ◽  
Angle Distribution ◽  
Turbine Stage ◽  
Radial Transport ◽  
Numerical Work ◽  
Flow Angle ◽  
Axial Turbines ◽  
Hot Streak

The flow field in a low-speed turbine stage with a uniform inlet total pressure is studied numerically. A circular hot streak is superposed on the vane inlet flow. In agreement with previous experimental and numerical work, it is observed that while the streak passes through the vane unaltered, significant radial transport occurs in the rotor. Furthermore, despite the unsteady nature of the flow field, the steady theory of Hawthorne (1974) is found to predict the radial transport velocity well. Making use of this theory, it is shown that the secondary vorticity in the rotor may be attributed to the effects of density stratification, the spatial variation of the vane exit flow angle and the relative eddy. It then follows that the extent of radial transport in the rotor may be influenced by altering the vane exit flow angle distribution. The present study examines one means by which this may be effected, viz., varying the vane twist across the span. It is shown that a “reverse” twist, wherein the flow angle at the vane exit is larger near the tip than it is at mid-span reduces the secondary flow (and consequently, radial transport) in the blade passage. On the other hand, “positive” twist, in which the vane exit flow angle decreases with span is found to markedly worsen the radial transport in the blade. It is to be noted that varying the vane twist is but one method to obtain the desired exit flow angle; possibilities for altering other aspects of the vane geometry also exist.

A Numerical Study of Secondary Flow in Axial Turbines With Application to Radial Transport of Hot Streaks

2000 ◽  
Vol 122 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Dilip Prasad ◽  
Gavin J. Hendricks
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Study ◽  
Angle Distribution ◽  
Turbine Stage ◽  
Radial Transport ◽  
Numerical Work ◽  
Flow Angle ◽  
Axial Turbines ◽  
Hot Streak

The flow field in a low-speed turbine stage with a uniform inlet total pressure is studied numerically. A circular hot streak is superposed on the vane inlet flow. In agreement with previous experimental and numerical work, it is observed that while the streak passes through the vane unaltered, significant radial transport occurs in the rotor. Furthermore, despite the unsteady nature of the flow field, the steady theory of Hawthorne (1974) is found to predict the radial transport velocity well. Making use of this theory, it is shown that the secondary vorticity in the rotor may be attributed to the effects of density stratification, the spatial variation of the vane exit flow angle, and the relative eddy. It then follows that the extent of radial transport in the rotor may be influenced by altering the vane exit flow angle distribution. The present study examines one means by which this may be effected, viz., varying the vane twist across the span. It is shown that a “reverse” twist, wherein the flow angle at the vane exit is larger near the tip than it is at midspan, reduces the secondary flow (and consequently, radial transport) in the blade passage. On the other hand, “positive” twist, in which the vane exit flow angle decreases with span, is found to worsen the radial transport in the blade markedly. It is to be noted that varying the vane twist is but one method to obtain the desired exit flow angle; possibilities for altering other aspects of the vane geometry also exist. [S0889-504X(00)00104-5]

Numerical Investigations of Forced Convection From Rectangular Coiled Pipes

2007 ◽  
Author(s):  
Ibrahima Conte´ ◽  
Xiao-Feng Peng ◽  
Zhen Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Secondary Flow ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Heat Transfer Process ◽  
Single Vortex ◽  
Staggered Arrangement ◽  
Inclination Angles ◽  
Turbulent Air Flow

Investigations are done to numerically study forced convective heat transfer from the flow inside a rectangular coiled pipe, as micro-scale heat exchange device with staggered arrangement, to the external flow around the pipe. The commercial CFD software Fluent 6.0 is used as the solver. The problems considered were three-dimensional laminar flow of the refrigerant R141B through the tube and turbulent air flow exterior to the tube. The studied coiled pipe was composed of four rows among which two rows were encompassed in a large rectangular coil and the other two were in an inner smaller rectangular coil. The results showed remarkable differences in the flow behavior and heat transfer for different rows of tubes. The secondary flow in the tubes bends of the larger rectangular coil is very weak compared to that of the inner rectangular coil. Better heat transfer process occurred through the tubes of the second row where the higher values of the fluid temperatures were observed in the pipe. The results showed the effects of the straight tubes inclination angle on the flow behavior in rectangular coiled pipes. The shape of the secondary flow is changed from a couple of vortices in the case of smaller angle (α = 9°) to a single vortex in the case of larger angle (α = 45°). The results also showed the rotation of the maximum axial velocity due to the increase in the straight tubes inclination angles. The results are in good agreement with previous numerical and experimental works on laminar flow in helical coil pipe.

The effect of endwall boundary layer and incoming wakes on secondary flow in a high-lift low-pressure turbine cascade at low Reynolds number

2019 ◽  
Vol 233 (15) ◽  
pp. 5637-5649 ◽  
Author(s):  
Xiao Qu ◽  
Yanfeng Zhang ◽  
Xingen Lu ◽  
Zhijun Lei ◽  
Junqiang Zhu
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Passage Vortex ◽  
Secondary Vortices

The endwall flow features are heavily dependent on the incoming boundary layer. It was particularly important to increase understanding the effect of inlet boundary layer thickness on endwall secondary flow under unsteady conditions. In present study, the influences of incoming wakes and various boundary layer thickness on endwall secondary flow were studied in a typical high-lift low-pressure turbine cascade, numerical calculation and experiment measurement of seven-hole probe were adopted at Re = 25,000 (based on the inlet velocity and the axial chord). Upstream wakes were simulated through moving rods upstream of the cascade. Detailed analysis was focused on the mechanisms of periodic wake influencing on the endwall vortex structures under thick endwall boundary layer condition. Influences of two different endwall boundary layer thickness on endwall secondary vortices structures were also comparatively analyzed. Under steady condition without wake, although thick incoming boundary layer reduces the cross-passage pressure gradient near endwall, more low momentum fluid inside thick endwall boundary layer is drawn into secondary vortices, finally resulting in stronger the pressure side leg of the leading edge horseshoe vortex and passage vortex, compared to the results of thin boundary layer condition. Under unsteady condition with thick inlet boundary layer, the “negative jet” effect of incoming wakes delays intersection of pressure side leg and suction side leg of leading edge horseshoe vortex on blade suction surface. The time-averaged strength of passage vortex and counter vortex core decreases by about 32%, and the underturning and overturning of endwall secondary flow is suppressed. The instantaneous results also indicate the endwall secondary vortices are reduced periodically at the position of wakes passing.

Numerical investigation of vortex generators to reduce cross-passage flow phenomena in compressor stator end-walls

2011 ◽  
Vol 225 (7) ◽  
pp. 877-885 ◽  
Author(s):  
J Ortmanns ◽  
C Pixberg ◽  
V Gümmer
Keyword(s):  
Secondary Flow ◽  
Vortex Flow ◽  
Vortex Generator ◽  
Initial Study ◽  
Vortex Generators ◽  
Geometrical Parameters ◽  
Single Vortex ◽  
Stator Vane ◽  
Flow Phenomena ◽  
Generator Design

The numerical results presented in this article demonstrate the ability of single-vortex generators to reduce the cross-passage secondary flow in a high-turning stator vane passage. The sensitivities of the induced vortex flow are determined in an initial study by varying the geometrical parameters. The visualization of the flow patterns and the determination of the stator vane performance show that the efficiency and the working range can be increased by applying single-vortex generators. The vortex generator design has to achieve a balance between the magnitude of vorticity induced to reduce the secondary flow phenomena and the additional losses associated with the produced vortex flow.

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.

Thermodynamics of Flowing Systems: with Internal Microstructure

1994 ◽  
Author(s):  
Antony N. Beris ◽  
Brian J. Edwards
Keyword(s):  
Free Energy ◽  
Theoretical Study ◽  
Flow Behavior ◽  
Irreversible Thermodynamics ◽  
Hamiltonian Mechanics ◽  
Complex Interplay ◽  
Microscopic Models ◽  
Flow Phenomena ◽  
The Subject ◽  
The Continuum

This much-needed monograph presents a systematic, step-by-step approach to the continuum modeling of flow phenomena exhibited within materials endowed with a complex internal microstructure, such as polymers and liquid crystals. By combining the principles of Hamiltonian mechanics with those of irreversible thermodynamics, Antony N. Beris and Brian J. Edwards, renowned authorities on the subject, expertly describe the complex interplay between conservative and dissipative processes. Throughout the book, the authors emphasize the evaluation of the free energy--largely based on ideas from statistical mechanics--and how to fit the values of the phenomenological parameters against those of microscopic models. With Thermodynamics of Flowing Systems in hand, mathematicians, engineers, and physicists involved with the theoretical study of flow behavior in structurally complex media now have a superb, self-contained theoretical framework on which to base their modeling efforts.

Unsteady Flow Phenomena in Rotating Centrifugal Impeller Passages

1970 ◽  
Vol 92 (1) ◽  
pp. 65-71 ◽  
Author(s):  
E. Lennemann ◽  
J. H. G. Howard
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Centrifugal Impeller ◽  
Bubble Flow ◽  
Hydrogen Bubble ◽  
Visualization Technique ◽  
Rotating Systems ◽  
Flow Phenomena ◽  
Relative Flow ◽  
Zero Flow

The phenomena of unsteady relative flow observed in a centrifugal impeller passage running at part capacity and zero flow are discussed. The mechanisms of passage stall for a shrouded and unshrouded impeller are investigated and a qualitative correlation is developed for the influence of secondary flow and inducer flow on the passage stall. The hydrogen bubble flow visualization technique is extended to higher velocities and rotating systems and provides the method for obtaining the experimental results.

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