scholarly journals Convergence of Fourier-based time methods for turbomachinery wake passing problems

2014 ◽  
Vol 278 ◽  
pp. 229-256 ◽  
Author(s):  
Adrien Gomar ◽  
Quentin Bouvy ◽  
Frédéric Sicot ◽  
Guillaume Dufour ◽  
Paola Cinnella ◽  
...  
Keyword(s):  
Wake Passing

Effects of Rotation on Blade Surface Heat Transfer: An Experimental Investigation

1997 ◽  
Author(s):  
Roger W. Moss ◽  
Roger W. Ainsworth ◽  
Tom Garside
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Experimental Investigation ◽  
Turbine Blade ◽  
Time History ◽  
Surface Heat ◽  
Blade Surface ◽  
Surface Heat Transfer ◽  
Effects Of Rotation ◽  
Wake Passing

Measurements of turbine blade surface heat transfer in a transient rotor facility are compared with predictions and equivalent cascade data. The rotating measurements involved both forwards and reverse rotation (wake free) experiments. The use of thin-film gauges in the Oxford Rotor Facility provides both time-mean heat transfer levels and the unsteady time history. The time-mean level is not significantly affected by turbulence in the wake; this contrasts with the cascade response to freestream turbulence and simulated wake passing. Heat transfer predictions show the extent to which such phenomena are successfully modelled by a time-steady code. The accurate prediction of transition is seen to be crucial if useful predictions are to be obtained.

scholarly journals Effects of Periodic Wake Passing Upon Aerodynamic Loss of a Turbine Cascade: Part I — Measurements of Wake-Affected Cascade Loss by Use of a Pneumatic Probe

1999 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Nobuaki Tetsuka ◽  
Tadashi Tanuma
Keyword(s):  
Turbine Cascade ◽  
Flow Angle ◽  
Linear Cascade ◽  
Local Loss ◽  
Aerodynamic Loss ◽  
Free Stream Turbulence ◽  
Pressure Distributions ◽  
Wake Turbulence ◽  
Wake Passing ◽  
Profile Loss

This paper reports on an experimental investigation of aerodynamic loss of a low-speed linear turbine cascade which is subjected to periodic wakes shed from moving bars of the wake generator. In this case, parameters related to the wake, such as wake passing frequency (wake Strouhal number) or wake turbulence characteristics, are varied to see how these wake-related parameters affect the local loss distribution or mass-averaged loss coefficient of the turbine cascade. Free-stream turbulence intensity is changed by use of a turbulence grid. In Part I of this paper a focus is placed on the measurements by use of a pneumatic five-hole yawmeter, which provides time-averaged stagnation pressure distributions downstream of the moving bars as well as of the turbine cascade. Spanwise distributions of wake-affected exit flow angle are also measured. From this study it is found that the wake passing greatly affects not only the profile loss but secondary loss of the linear cascade. Noticeable change in exit flow angle is also identified.

Influence of Wake Passing Frequency and Elevated Turbulence Intensity on Transition.

2005 ◽  
Vol 19 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Richard W. Kaszeta ◽  
Terrence W. Simon ◽  
Nan Jiang ◽  
Federico Ottaviani
Keyword(s):  
Turbulence Intensity ◽  
Wake Passing

Effect of Periodic Wake Passing on Film Effectiveness of Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1997 ◽  
Vol 119 (2) ◽  
pp. 292-301 ◽  
Author(s):  
K. Funazaki ◽  
M. Yokota ◽  
S. Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Aero Engine ◽  
Secondary Air ◽  
Wake Passing

Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the mainstream and secondary air is about 20 K. In this case, the air density ratio of the mainstream and secondary air becomes less than unity, therefore the flow condition encountered in an actual aero-engine cannot be simulated in terms of the density ratio. A spoke-wheel type wake generator is used in this study. In addition, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. For each of the blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals in order to obtain qualitative information of film effectiveness distribution.

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.

The Effect of Periodic Wake Passing on Film Effectiveness of Discrete Cooling Holes Around the Leading Edge of a Blunt Body

1995 ◽  
Author(s):  
K. Funazaki ◽  
M. Yokota ◽  
S. Yamawaki
Keyword(s):  
Blunt Body ◽  
Free Stream ◽  
Turbine Blades ◽  
Density Ratio ◽  
Leading Edge ◽  
Test Model ◽  
Free Stream Turbulence ◽  
Aero Engine ◽  
Secondary Air ◽  
Wake Passing

Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the mainstream and secondary air is about 20K. In this case, air density ratio of the mainstream and secondary air becomes less than unity, therefore the flow condition encountered in an actual aero-engine can not be simulated in terms of the density ratio. A spoke-wheel type wake generator is used in this study. In addition, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. For each of the blowing ratios, wall temperature around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals in order to obtain qualitative information of film effectiveness distribution.

The Effect of Wake Passing on a Flow Separation in a Low-Pressure Turbine Cascade

2004 ◽  
Vol 126 (2) ◽  
pp. 250-256 ◽  
Author(s):  
Michael J. Brear ◽  
Howard P. Hodson
Keyword(s):  
Separation Bubble ◽  
Phase Locking ◽  
Experimental Studies ◽  
Leading Edge ◽  
Low Pressure ◽  
Pressure Surface ◽  
Low Pressure Turbine ◽  
Numerical Predictions ◽  
Unsteady Interaction ◽  
Wake Passing

This paper describes an investigation into the effect that passing wakes have on a separation bubble that exists on the pressure surface and near the leading edge of a low-pressure turbine blade. Previous experimental studies have shown that the behavior of this separation is strongly incidence dependent and that it responds to its disturbance environment. The results presented in this paper examine the effect of wake passing in greater detail. Two-dimensional, Reynolds averaged, numerical predictions are first used to examine qualitatively the unsteady interaction between the wakes and the separation bubble. The separation is predicted to consist of spanwise vortices whose development is in phase with the wake passing. However, comparison with experiments shows that the numerical predictions exaggerate the coherence of these vortices and also overpredict the time-averaged length of the separation. Nonetheless, experiments strongly suggest that the predicted phase locking of the vortices in the separation onto the wake passing is physical.

Recognition of Structures Leading to Transition in a Low Pressure Turbine Cascade: Effect of Reduced Frequency

2019 ◽  
Author(s):  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino ◽  
F. Bertini
Keyword(s):  
Boundary Layer ◽  
Suction Side ◽  
Low Pressure ◽  
Turbine Cascade ◽  
Turbulent Structures ◽  
Time Resolved ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Displacement Thickness ◽  
Wake Passing

Abstract The boundary layer developing over the suction side of a low pressure turbine cascade operating under unsteady inflow conditions has been experimentally investigated. Time-resolved Particle Image Velocimetry (PIV) measurements have been performed in two orthogonal planes, the blade to blade and a wall parallel plane embedded within the boundary layer, for two different wake reduced frequencies. Proper Orthogonal Decomposition (POD) has been used to analyze the data and to provide an interpretation of the most significant flow structures for each phase of the wake passing cycle. To this purpose, a POD based procedure that sorts the data synchronizing the measurements of the two planes has been developed. Phase averaged data are then obtained for both cases. Moreover, once properly sorted, POD has been applied to sub-ensembles of data at the same relative phase within the wake passing cycle. Detailed information on the most energetic turbulent structures at a particular phase are obtained with this procedure (called phased POD), overcoming the limit of classical phase average that just provides a statistical representation of the turbulence field. Furthermore, the synchronization of the measurements in the two planes allows the computation of the characteristic dimension of boundary layer structures that are responsible for transition. These structures are often identified as vortical filaments parallel to the wall, typically referred to as boundary layer streaks. The largest and most energetic structures are observed when the wake centerline passes over the rear part of the suction side, and they appear practically the same for both reduced frequencies. The passing wake forces transition leading to the breakdown of the boundary layer streaks. Otherwise, the largest differences between the low and high reduced frequency are observed in the calmed region. The post-processing of these two planes further allowed us to compute the spacing of the streaks and make it non-dimensional by the boundary layer displacement thickness observed for each phase. The non-dimensional value of the streaks spacing is about constant, irrespective of the reduced frequency.

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