scholarly journals The Effect of a Transversely Injected Stream on the Flow Through Turbine Cascades: Part I — Flow Effects

1977 ◽  
Author(s):  
K. D. Shrivastava ◽  
N. R. L. MacCallum
Keyword(s):  
Separation Bubble ◽  
Transverse Flow ◽  
Main Flow ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Total Head ◽  
Flow Through ◽  
Turbine Cascades ◽  
Flow Effects ◽  
End Wall

A study has been made of the flow-through turbine cascade when a transverse flow is injected into the main flow immediately in front of the cascade. A separation bubble was observed on the end-wall immediately behind the injection slot. At the suction surface end of this bubble a vortex moved into the main flow and continued downstream through, and beyond, the cascade. The effects of the separation bubble and of the vortex were observed in measurements of pressure around the blade surfaces, in boundary layer transverses on the end-wall, and in total head and directional transverses across the cascade exit.

The Effect of a Transversely Injected Stream on the Flow Through Turbine Cascades: Part II — Performance Changes

1977 ◽  
Author(s):  
K. D. Shrivastava ◽  
N. R. L. MacCallum
Keyword(s):  
Flow Injection ◽  
Transverse Flow ◽  
Stagnation Pressure ◽  
Main Flow ◽  
Secondary Flows ◽  
Pressure Losses ◽  
Flow Through ◽  
Turbine Cascades ◽  
Inlet Angle ◽  
End Wall

This paper reports the changes in the performance of three turbine cascades when a transverse flow is injected from an end-wall into the main flow immediately in front of the cascade The cascades used the same blade profiles, but set at stagger angles of 35, 40 and 45 deg. The effects of the following other variables were also investigated — main flow inlet angle, injection jet inclination to main flow, injection jet velocity, and jet width. The performance changes were assessed by measurements of averaged stagnation pressure losses, reductions in flow capacities, measurements of secondary flows within the channel, and measurements of the exit vortex.

Numerical Investigation of the Wake-Boundary Layer Interaction on a Highly Loaded LP Turbine Cascade Blade

2002 ◽  
Author(s):  
Pasquale Cardamone ◽  
Peter Stadtmu¨ller ◽  
Leonhard Fottner
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Transition Process ◽  
Reynolds Numbers ◽  
Numerical Approach ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Time Resolved ◽  
Highly Loaded

The effects of wake passing on the development of the profile boundary layer of a highly loaded low-pressure turbine cascade are studied using the RANS code TRACE-U. The numerical results are compared with available experimental data to verify the accuracy of the code in predicting the periodic-unsteady transition and separation mechanisms at low Reynolds number conditions. The experimental investigations have been carried out on a turbine cascade called T106D-EIZ subjected to wakes generated by an up-stream moving bar-type generator. The cascade pitch was increased by about 30% with respect to design conditions without modifying the blade geometry in order to obtain a large separation bubble on the suction surface. The extensive database containing time-averaged as well as time-resolved results was presented in a separate paper by Stadtmu¨ller and Fottner (2001) and is discussed only briefly. The time-accurate multistage Navier-Stokes solver TRACE-U developed by the DLR Cologne used for the numerical simulations employs a modified version of the one-equation Spalart-Allmaras turbulence model coupled with a transition correlation based on the work of Abu-Ghannam and Shaw in the formulation of Drela. The objective of this paper is to provide further insight into the aerodynamics of the wake-induced transition process and to rate the application limits of the numerical approach for exit Reynolds numbers as low as 60.000. The CFD predictions for two different flow conditions are compared with the measurements. Plots of wall-shear stress, blade loading, shape factor and loss behaviour are used to verify the reliability of the code. The periodic-unsteady development of the boundary layer as well as the loss behaviour is well reproduced for higher Reynolds numbers. For the case with massive separation, large discrepancies between numerical and experimental results are observed.

The Effect of a Transversely Injected Stream on the Flow through Turbine Cascades—Part III: Influence of Aspect Ratio

1979 ◽  
Vol 101 (1) ◽  
pp. 61-67
Author(s):  
B. A. Aburwin ◽  
N. R. L. Maccallum
Keyword(s):  
Aspect Ratio ◽  
Stagnation Pressure ◽  
Dimensional Theory ◽  
One Dimensional ◽  
Flow Capacity ◽  
Aspect Ratios ◽  
New Instrumentation ◽  
Flow Through ◽  
Turbine Cascades ◽  
End Wall

An experimental investigation has been made of the effect of a transversely injected stream on the flow through turbine cascades similar to those in which previous studies [1, 2] had been made, but having aspect ratios of 1.5 and 1.0 compared to the previous value of 3.0. New instrumentation includes a five-hole probe. The average losses in stagnation pressure and the changes in flow capacity remain in agreement with one-dimensional theory. The exit vortex is moved towards the end-wall as aspect ratio is reduced. The strength of the vortex is diminished when the aspect ratio is reduced from 3.0 to 1.5, but there is little change for the further reduction of aspect ratio.

Numerical Prediction of Profile and Endwall Losses for Multi-Splitter Turbine Cascades

1993 ◽  
Author(s):  
D. M. Zhou ◽  
Z. G. Zhang ◽  
Y. S. Li
Keyword(s):  
Surface Friction ◽  
Turbine Cascade ◽  
Integral Boundary ◽  
Flow Solver ◽  
Secondary Loss ◽  
Boundary Layer Method ◽  
Flow Through ◽  
Turbine Cascades ◽  
Semi Empirical ◽  
Profile Loss

A simple numerical method for predicting the profile loss and the endwall secondary loss of multi-splitter turbine cascade in subsonic flow is presented. A variational finite element potential flow solver is used to obtain the main flow through the blade passages, the loss due to the surface friction is calculated using an integral boundary layer method, the trailing-edge loss is calculated directly from the empirical correlation, and a semi-empirical model for estimating the endwall secondary loss is also provided. The rationality of the approach is justified by the agreement of the prediction with a range of experimental measurement.

Comparison of Transverse Injection Effects in Annular and in Straight Turbine Cascades

1979 ◽  
Author(s):  
J. P. Bindon ◽  
B. A. Aburwin ◽  
N. R. L. Maccallum
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Separation Bubble ◽  
Wall Boundary Layer ◽  
Passage Vortex ◽  
Nose Cone ◽  
Transverse Injection ◽  
Turbine Cascades ◽  
Annular Cascade ◽  
End Wall

An experimental investigation has been made of the effects of transverse injection from the hub in front of the blades of an annular cascade. The hub end-wall boundary layer could be skewed, by rotating the nose cone. The data on transverse injection effects in straight cascades was extended to provide comparisons with the annular cascade results. Similar effects were observed in the two types of cascades, the principal effects being the creation of a separation bubble on the hub end-wall behind the injection slot, and the strengthening of the passage vortex, which is lifted away from the hub end-wall.

Forcing of Separation Bubbles by Main Flow Unsteadiness or Pulsed Vortex Generating Jets—A Comparison

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Christoph Lyko ◽  
Jerrit Dähnert ◽  
Dieter Peitsch
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Separation Bubble ◽  
Active Flow Control ◽  
Transition Process ◽  
Low Pressure ◽  
Main Flow ◽  
Suction Surface ◽  
Forcing Mechanisms ◽  
The One

Low pressure turbines typically operate in the low Reynolds number regime. Depending on the loading of the blade, they may exhibit detached flow with associated reattachment in the rear part of the suction surface. Additionally, the flow is highly time-dependent due to the sequence of rotating and stationary blade rows. The work presented in this paper covers experimental efforts taken to investigate this type of flow in detail. Typical low pressure turbine flow conditions have been chosen as baseline for the experimental work. A pressure distribution has been created on a flat plate by means of a contoured upper wall in a low speed wind tunnel. The distribution matches the one of the Pak-B airfoil. Unsteadiness is then superimposed in two ways: A specific unsteadiness was created by using a rotating flap (RF) downstream of the test section. This results in almost sinusoidal periodic unsteady flow across the plate, simulating the interaction between stator and rotor of a turbine stage. Furthermore, pulsed blowing by vortex generating jets (VGJ) upstream of the suction peak was used to influence the transition process and development of the separation bubble. Measurements have been performed with hot-wire anemometry. Experimental results are presented to compare both forcing mechanisms. In sinusoidal unsteady main flow, the transition occurs naturally by the breakdown of the shear layer instability, which is affected by periodic changes in the overall Reynolds number and thus pressure gradient. In opposition, active flow control (AFC) by VGJ triggers the transition process by impulse and vorticity injection into the boundary layer, while maintaining a constant Reynolds number. The flow fields are compared using phase averaged data of velocity und turbulence intensity as well as boundary layer parameters, namely shape factor and momentum thickness Reynolds number. Finally, a model to describe the time mean intermittency distribution is refined to fit the data.

Forcing of Separation Bubbles by Main Flow Unsteadiness or Pulsed Vortex Generating Jets: A Comparison

2013 ◽  
Author(s):  
Christoph Lyko ◽  
Jerrit Dähnert ◽  
Dieter Peitsch
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Separation Bubble ◽  
Active Flow Control ◽  
Transition Process ◽  
Low Pressure ◽  
Main Flow ◽  
Suction Surface ◽  
Forcing Mechanisms ◽  
The One

Low pressure turbines typically operate in the low Reynolds number regime. Depending on the loading of the blade, they may exhibit detached flow with associated re-attachment in the rear part of the suction surface. Additionally the flow is highly time-dependent due to the sequence of rotating and stationary blade rows. The work presented in this paper covers experimental efforts taken to investigate this type of flow in detail. Typical low pressure turbine flow conditions have been chosen as baseline for the experimental work. A pressure distribution has been created on a flat plate by means of a contoured upper wall in a low speed wind tunnel. The distribution matches the one of the Pak-B airfoil. Unsteadiness is then super-imposed in two ways: A specific unsteadiness was created by using a Rotating Flap (RF) downstream of the test section. This results in almost sinusoidal periodic unsteady flow across the plate, simulating the interaction between stator and rotor of a turbine stage. Furthermore pulsed blowing by Vortex Generating Jets (VGJ) upstream of the suction peak was used to influence the transition process and development of the separation bubble. Measurements have been performed with hot-wire anemometry. Experimental results are presented to compare both forcing mechanisms. In sinusoidal unsteady main flow the transition occurs naturally by the breakdown of the shear layer instability, which is affected by periodic changes in the overall Reynolds number and thus pressure gradient. In opposition, Active Flow Control (AFC) by VGJ triggers the transition process by impuls and vorticity injection into the boundary layer, while maintaining a constant Reynolds number. The flow fields are compared using phase averaged data of velocity und turbulence intensity as well as boundary layer parameters, namely shape factor and momentum thickness Reynolds number. Finally a model to describe the time mean intermittency distribution is refined to fit the data.

Unsteady Flow in Oscillating Turbine Cascade: Part 2 — Computational Study

1996 ◽  
Author(s):  
L. He
Keyword(s):  
Unsteady Flow ◽  
Flow Separation ◽  
Computational Study ◽  
Separation Bubble ◽  
Computational Method ◽  
Influence Coefficient ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Influence Coefficient Method ◽  
Coefficient Method

Unsteady flow around a linear oscillating turbine cascade has been experimentally and computationally studied, aimed at understanding the bubble type of flow separation and examining the predictive ability of a computational method. It was also intended to check the validity of the linear assumption under an unsteady viscous flow condition. Part 2 of the paper presents a computational study of the experimental turbine cascade as discussed in Part 1. Numerical calculations were carried out for this case using an unsteady Navier-Stokes solver. The Baldwin-Lomax mixing length model was adopted for turbulence closure. The boundary layers on blade surfaces were either assumed to be fully turbulent or transitional with the unsteady transition subject to a quasi-steady laminar separation bubble model. The comparison between the computations and the experiment were generally quite satisfactory, except in the regions with the flow separation. It was shown that the behaviour of the short-bubble on the suction surface could be reasonably accounted for by using the quasi-steady bubble transition model. The calculation also showed that there was a more apparent mesh dependence of the results in the regions of flow separation. Two different kinds of numerical tests were carried out to check the linearity of the unsteady flow and therefore the validity of the Influence Coefficient method. Firstly calculations using the same configurations as in the experiment were performed with different oscillating amplitudes. Secondly calculations were performed with a tuned cascade model and the results were compared with those using the Influence Coefficient method. The present work showed that nonlinear effect was quite small, even though for the most severe case in which the separated flow region covered about 60% of blade pressure surface with a large movement of the reattachment point. It seemed to suggest that the linear assumption about the unsteady flow behaviour should be adequately acceptable for situations with bubble type flow separation similar to the present case.

scholarly journals Experimental and Numerical Investigations of Wake Passing Effects Upon Aerodynamic Performance of a LP Turbine Linear Cascade With Variable Solidity

2006 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Kazutoyo Yamada ◽  
Takahiro Ono ◽  
Ken-ichi Segawa ◽  
Hiroshi Hamazaki ◽  
...  
Keyword(s):  
Separation Bubble ◽  
Probe Measurement ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Linear Cascade ◽  
Aerodynamic Loss ◽  
Wire Probe ◽  
Numerical Studies ◽  
Lp Turbine ◽  
Wake Passing

This paper deals with experimental and numerical studies on the flow field around a low-pressure linear turbine cascade whose solidity is changeable. The purpose of them is to clarify the effect of incoming wakes upon the aerodynamic loss of the cascade that is accompanied with separation on the airfoil suction surface, in particular for low Reynolds number conditions and/or low solidity conditions. Cylindrical bars on the timing belts work as wake generator to emulate wakes that impact the cascade. Pneumatic probe measurement is made to obtain total pressure loss distributions downstream of the cascade. Hot-wire probe measurement is also conducted over the airfoil suction surface. Besides, LES-based numerical simulation is executed to deepen the understanding of the interaction of the incoming wakes with the boundary layer containing separation bubble.

Influence of Tip Clearance on the Inter Blade and Exit Flow Field of a Turbine Rotor Cascade

1994 ◽  
Author(s):  
M. Govardhan ◽  
N. Venkatrayulu ◽  
V. S. Vishnubhotla
Keyword(s):  
Static Pressure ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Static Pressure Distribution ◽  
Blade Tip ◽  
Flow Through ◽  
Downstream Flow

A detailed study of flow through the blade passage and downstream of a linear turbine cascade was carried out for four cases of tip clearance including zero clearance. Apart from inlet traverse, a total of eight stations were chosen for inter-blade flow traversing between 5% and 95% of axial chord from leading edge. Downstream flow surveys were made at distances of 106% of axial chord from the blade leading edge. Pitchwise and spanwise traverses were conducted for each tip clearance at these stations using a small five hole probe. Provision was also made for the measurement of static pressure distribution on the suction and pressure surfaces and also on the blade tip surface when clearance is present. At about 40% of axial chord from the leading edge, the presence of clearance vortex is identified inside the passage. The growth of the clearance vortex in size, its movement towards the suction surface and its increase in strength with the gap size were observed beyond 55% of axial chord till the trailing edge region. The rate of growth of the losses in the endwall region increased with clearance. Horse shoe vortex was not observed for the highest clearance. The overall losses increase rapidly with clearance in the rear half of the blade.

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