Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low-Speed Turbine Cascade

1990 ◽  
Vol 112 (3) ◽  
pp. 539-546 ◽  
Author(s):  
F. Bario ◽  
F. Leboeuf ◽  
A. Onvani ◽  
A. Seddini
Keyword(s):  
Secondary Flow ◽  
Side Wall ◽  
Velocity Fields ◽  
Measuring Apparatus ◽  
Flow Ratio ◽  
Turbine Cascade ◽  
Hot Wire ◽  
Local Pressure ◽  
Low Speed ◽  
Jet Behavior

The aerodynamic behavior of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low-speed nozzle turbine cascade. The experimental setup and the jet behavior are fully described. The effects of location with respect to the blades, mass flow ratio, yaw, and incidence angles on the aerodynamics of single jets are investigated. The influence of neighboring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories, and visualizations are discussed. The measuring apparatus includes a five-hole probe and a hot wire for intermittency measurements.

Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low Speed Turbine Cascade

1989 ◽  
Author(s):  
F. Bario ◽  
F. Leboeuf ◽  
A. Onvani ◽  
A. Seddini
Keyword(s):  
Secondary Flow ◽  
Side Wall ◽  
Velocity Fields ◽  
Measuring Apparatus ◽  
Flow Ratio ◽  
Turbine Cascade ◽  
Hot Wire ◽  
Local Pressure ◽  
Low Speed ◽  
Set Up

The aerodynamic behaviour of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low speed nozzle turbine cascade. The experimental set up and the jet behaviour are fully described. The effects of location with respect to the blades, mass flow ratio, yaw and incidence angles on the aerodynamics of single jets are investigated. The influence of neighbouring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories and visualizations are discussed. The measuring apparatus includes a five hole probe and an hot wire for intermittency measurements.

Anisotropic Eddy Viscosity in the Secondary Flow of a Low-Speed Linear Turbine Cascade

2011 ◽  
Author(s):  
G. D. MacIsaac ◽  
S. A. Sjolander
Keyword(s):  
Turbulent Flow ◽  
Secondary Flow ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Leading Edge ◽  
Boussinesq Approximation ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Low Speed ◽  
Sst Turbulence Model

The final losses within a turbulent flow are realized when eddies completely dissipate to internal energy through viscous interactions. The accurate prediction of the turbulence dissipation, and therefore the losses, requires turbulence models which represent, as accurately as possible, the true flow physics. Eddy viscosity turbulence models, commonly used for design level computations, are based on the Boussinesq approximation and inherently assume the eddy viscosity field is isotropic. The current paper compares the computational predictions of the flow downstream of a low-speed linear turbine cascade to the experimentally measured results. Steady-state computational simulations were performed using ANSYS CFX v12.0 and employed the shear stress transport (SST) turbulence model with the γ-Reθ transition model. The experimental data includes measurements of the mean and turbulent flow quantities. Steady pressure measurements were collected using a seven-hole pressure probe and the turbulent flow quantities were measured using a rotatable x-type hotwire probe. Data is presented for two axial locations: 120% and 140% of the axial chord (Cx) downstream of the leading edge. The computed loss distribution and total bladerow losses are compared to the experimental measurements. Differences are noted and a discussion of the flow structures provides insights into the origin of the differences. Contours of the shear eddy viscosity are presented for each axial plane. The secondary flow appears highly anisotropic, demonstrating a fundamental difference between the computed and measured results. This raises questions as to the validity of using two-equation turbulence models, which are based on the Boussinesq approximation, for secondary flow predictions.

scholarly journals Secondary Flow Control and Streamwise Vortices Formation

1994 ◽  
Author(s):  
Piotr P. Doerffer ◽  
Jochen Amecke
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Secondary Flow ◽  
Side Wall ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
Streamwise Vortices ◽  
Wall Boundary Layer ◽  
Passage Vortex ◽  
Horse Shoe Vortex

The structure of a secondary flow in a linear turbine cascade has been investigated. In order to analyse streamwise vortices configuration and to control their formation two types of side wall boundary layer fences have been applied. Results obtained proved that the streamwise fence reduces significantly spanwise extent of secondary flows. Transverse fence has no such effect but causes very significant change of location and the losses level in a passage vortex. Presented results cast some new light on the contribution of passage vortex, horse shoe vortex and a shear plain in between, to the losses maximum where these flow elements are in direct neighbourhood.

A Turbine Cascade Facility for Secondary Flow Research

2006 ◽  
Author(s):  
D. A. Bagshaw ◽  
D. G. Gregory-Smith ◽  
G. L. Ingram ◽  
M. R. Stokes
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Experimental Results ◽  
Test Case ◽  
Turbine Cascade ◽  
Inlet Flow ◽  
Low Speed ◽  
To Come

This paper outlines some recent major changes to the so-called Durham Cascade that will be of interest to other experimenters working on low speed linear cascades. The Durham Cascade is a popular CFD test case and has also been used extensively for profiled endwall research (Hartland et al. [1]) and more recently for the study of reverse compound lean (Bagshaw et al. [2]). The cascade has recently undergone a complete rebuild, which enables it to provide experimental results of lasting significance for a number of years to come. The improvements described in this paper include, good quality symmetrical inlet flow, a new three-dimensional traverse system and an improved blade cartridge system allowing arbitrary three-dimensional geometries to be tested.

Hot-wire probes in low speed flow

1979 ◽  
Vol 18 ◽  
pp. 271-323 ◽  
Author(s):  
J.-D. Vagt
Keyword(s):  
Hot Wire ◽  
Low Speed ◽  
Speed Flow

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.

The Aerothermal Performance of a Cooled Winglet Tip in a High Pressure Turbine Cascade

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Chao Zhou ◽  
Howard Hodson ◽  
Ian Tibbott ◽  
Mark Stokes
Keyword(s):  
Mass Flow ◽  
Heat Load ◽  
Blade Surface ◽  
Flow Ratio ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
High Pressure Turbine ◽  
Cooling Effectiveness ◽  
Tip Leakage ◽  
Coolant Injection

The aerothermal performance of a winglet tip with cooling holes on the tip and on the blade surface near the tip is reported in this paper. The investigation was based on a high pressure turbine cascade. Experimental and numerical methods were used. The effects of the coolant mass flow rate are also studied. Because the coolant injection partially blocks the tip leakage flow, more passage flow is turned by the blade. As a result, the coolant injection on the winglet tip reduces the deviation of the flow downstream of the cascade due to the tip leakage flow. However, the tip leakage loss increases slightly with the coolant mass flow ratio. Both the computational fluid dynamics tools and experiments using the Amonia–Diazo technique were used to determine the cooling effectiveness. On the blade pressure side surface, low cooling effectiveness appears around the holes due to the lack of the coolant from the cooling hole or the lift-off of the coolant from the blade surface when the coolant mass flow is high. The cooling effectiveness on the winglet tip is a combined effect of the coolant ejected from all the holes. On the top of the winglet tip, the average cooling effectiveness increases and the heat load decreases with increasing coolant mass flow. Due to its large area, the cooled winglet tip has a higher heat load than an uncooled flat tip at engine representative coolant mass flow ratio. Nevertheless, the heat flux rate per unit area of the winglet is much lower than that of an uncooled flat tip. The cycle analysis is carried out and the effects of relative tip-to-casing endwall motion are address.

Non-Axisymmetric Turbine Endwall Aerodynamic Optimization Design: Part I — Turbine Cascade Design and Experimental Validations

2014 ◽  
Author(s):  
Hao Sun ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Secondary Flow ◽  
Evaluation Method ◽  
Pressure Coefficient ◽  
Optimization Method ◽  
Experimental Measurements ◽  
Turbine Cascade ◽  
Aerodynamic Optimization ◽  
Flow Losses ◽  
Flow Intensity ◽  
Performance Evaluation Method

The non-axisymmetric endwall profiling has been proven to be an effective tool to reduce the secondary flow loss in turbomachinery. In this work, the aerodynamic optimization for the non-axisymmetric endwall profile of the turbine cascade and stage was presented and the design results were validated by annular cascade experimental measurements and numerical simulations. The parametric method of the non-axisymmetric endwall profile was proposed based on the relation between the pressure field variation and the secondary flow intensity. The optimization system combines with the non-axisymmetric endwall parameterization method, global optimization method of the adaptive range differential evolution algorithm and the aerodynamic performance evaluation method using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and k–ω SST turbulent with transition model solutions. In the part I, the optimization method is used to design the optimum non-axisymmetric endwall profile of the typical high loaded turbine stator. The design objective was selected for the maximum total pressure coefficient with constrains on the mass flow rate and outlet flow angle. Only five design variables are needed for one endwall to search the optimum non-axisymmetric endwall profile. The optimized non-axisymmetric endwall profile of turbine cascade demonstrated an improvement of total pressure coefficient of 0.21% absolutely, comparing with the referenced axisymmetric endwall design case. The reliability of the numerical calculation used in the aerodynamic performance evaluation method and the optimization result were validated by the annular vane experimental measurements. The static pressure distribution at midspan was measured while the cascade flow field was measured with the five-hole probe for both the referenced axisymmetric and optimized non-axisymmetric endwall profile cascades. Both the experimental measurements and numerical simulations demonstrated that both the secondary flow losses and the profile loss of the optimized non-axisymmetric endwall profile cascade were significantly reduced by comparison of the referenced axisymmetric case. The weakening of the secondary flow of the optimized non-axisymmetric endwall profile design was also proven by the secondary flow vector results in the experiment. The detailed flow mechanism of the secondary flow losses reduction in the non-axisymmetric endwall profile cascade was analyzed by investigating the relation between the change of the pressure gradient and the variation of the secondary flow intensity.

Numerical Investigation of Secondary Flow Vortex Core Structure in the Two-Pass Rectangular Channel With 45° Ribs

2015 ◽  
Author(s):  
Jiangnan Zhu ◽  
Tieyu Gao ◽  
Jun Li ◽  
Guojun Li ◽  
Jianying Gong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Vortex Core ◽  
Side Wall ◽  
Main Flow ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Flow Vortex

The secondary flow which is generated by the angled rib is one of the key factors of heat transfer enhancement in gas turbine blade cooling channels. However, the current studies are all based on the velocity vector and streamline, which limit the research on the detailed micro-structure of secondary flow. In order to make further targeted optimization on the flow and heat transfer in the cooling channels of gas turbine blade, it is necessary to firstly investigate the generation, interaction, dissipation and the influence on heat transfer of secondary flow with the help of new topological method. This paper reports the numerical study of the secondary flow and the effect of secondary flow on heat transfer enhancement in rectangular two-pass channel with 45° ribs. Based on the vortex core technology, the structure of secondary flow can be clearly shown and studied. The results showed that the main flow secondary flow is thrown to the outer side wall after the corner due to the centrifugal force. Then it is weakened in the second pass and a new main flow secondary flow is generated at the same time near the opposite side wall in the second pass. The Nusselt number distribution has also been compared with the secondary flow vortex core distribution. The results shows that the heat transfer strength is weakened in the second pass due to the interaction between the old main flow secondary flow and the new one. These two secondary flows are in opposite rotation direction, which reduces the disturbance and mass transfer strength in the channel.

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