scholarly journals Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

1999 ◽  
Author(s):  
Dieter E. Bohn ◽  
Karsten A. Kusterer
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Fluid ◽  
Flow Phenomena ◽  
Vortex Systems

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.

Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

1999 ◽  
Vol 122 (2) ◽  
pp. 334-339 ◽  
Author(s):  
Dieter E. Bohn ◽  
Karsten A. Kusterer
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Back Side ◽  
Stagnation Line ◽  
Flow Phenomena ◽  
The Impact

A leading edge cooling configuration is investigated numerically by application of a three-dimensional conjugate fluid flow and heat transfer solver, CHT-flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multiblock technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45 deg. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three-dimensional and asymmetric jet flow field. Within a secondary flow analysis, the cooling fluid jets are investigated in detail. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a respectable agreement concerning the vortex development. [S0889-504X(00)00102-1]

Flow Field Measurements on a Large Scale Turbine Cascade With Leading Edge Film Cooling by Two Rows of Holes

1997 ◽  
Author(s):  
Sabine Ardey ◽  
Leonhard Fottner
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Vortex Pair ◽  
Leading Edge ◽  
Field Measurements ◽  
Suction Side ◽  
Pressure Side ◽  
Turbine Cascade

To increase the understanding of the aerodynamic processes dominating the flow field of turbine bladings with leading edge film cooling, isothermal investigations were carried out on a large scale high pressure turbine cascade. Near the stagnation point the blades are equipped with one row of film cooling holes on the suction side and one on the pressure side. Blowing ratio, turbulence intensity, Mach number, and Reynolds number are set to values typically found in modern gas turbines. Experimental data of the cascade flow were obtained by pneumatic probes and static pressure tappings. The flow field was visualized by Schlieren and oil flow techniques. For detailed investigations near the blowing holes the Laser Transit Velocimetry and the three dimensional Hot Wire Anemometry were used. The flow field measurements in the near hole region of the suction side show the typical kidney shaped vortex pair. A local suction peak on the pressure side causes a large recirculation area behind the holes on the pressure side and induces separation bubbles in between the pressure side holes. This leads to the generation of two pairs of vortices: The kidney-vortex is located on top of a second vortex pair and a trough flow that fills up the deficit of the recirculation. Thus the film cooling air is detached from the pressure side surface. In addition to the mean flow vectors Reynolds stress components are a good means to judge the propagation of the jet. In spite of the complex flow pattern occurring on each single jet, the surveyed loss-increase due to the leading edge blowing can be predicted by the mixing layer model.

Volumetric Velocimetry Measurements of Purge–Mainstream Interaction in a One-Stage Turbine

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Blade Passage ◽  
One Stage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Cooling of Turbine Blades With Expanded Exit Holes: Computational Analyses of Leading Edge and Pressure-Side of a Turbine Blade

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Fariborz Forghan ◽  
Omid Askari ◽  
Uichiro Narusawa ◽  
Hameed Metghalchi
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Leading Edge ◽  
Weak Shock ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Hot Gas ◽  
Computational Analyses

Turbine blades are cooled by a jet flow from expanded exit holes (EEH) forming a low-temperature film over the blade surface. Subsequent to our report on the suction-side (low-pressure, high-speed region), computational analyses are performed to examine the cooling effectiveness of the flow from EEH located at the leading edge as well as at the pressure-side (high-pressure, low-speed region). Unlike the case of the suction-side, the flow through EEH on the pressure-side is either subsonic or transonic with a weak shock front. The cooling effectiveness, η (defined as the temperature difference between the hot gas and the blade surface as a fraction of that between the hot gas and the cooling jet), is higher than the suction-side along the surface near the exit of EEH. However, its magnitude declines sharply with an increase in the distance from EEH. Significant effects on the magnitude of η are observed and discussed in detail of (1) the coolant mass flow rate (0.001, 0.002, and 0.004 (kg/s)), (2) EEH configurations at the leading edge (vertical EEH at the stagnation point, 50 deg into the leading-edge suction-side, and 50 deg into the leading-edge pressure-side), (3) EEH configurations in the midregion of the pressure-side (90 deg (perpendicular to the mainstream flow), 30 deg EEH tilt toward upstream, and 30 deg tilt toward downstream), and (4) the inclination angle of EEH.

Numerical Simulation of Cavitating Flow in Mixed Flow Pump With Closed Type Impeller

2009 ◽  
Author(s):  
Katsutoshi Kobayashi ◽  
Yoshimasa Chiba
Keyword(s):  
Leading Edge ◽  
Suction Side ◽  
Experimental Results ◽  
Absolute Pressure ◽  
Pressure Side ◽  
Blade Surface ◽  
Mixed Flow ◽  
Closed Type ◽  
The Absolute ◽  
Flow Pump

LES (Large Eddy Simulation) with a cavitation model was performed to calculate an unsteady flow for a mixed flow pump with a closed type impeller. First, the comparison between the numerical and experimental results was done to evaluate a computational accuracy. Second, the torque acting on the blade was calculated by simulation to investigate how the cavitation caused the fluctuation of torque. The absolute pressure around the leading edge on the suction side of blade surface had positive impulsive peaks in both the numerical and experimental results. The simulation showed that those peaks were caused by the cavitaion which contracted and vanished around the leading edge. The absolute pressure was predicted by simulation with −10% error. The absolute pressure around the trailing edge on the suction side of blade surface had no impulsive peaks in both the numerical and experimental results, because the absolute pressure was 100 times higher than the saturated vapor pressure. The simulation results showed that the cavitation was generated around the throat, then contracted and finally vanished. The simulated pump had five throats and cavitation behaviors such as contraction and vanishing around five throats were different from each other. For instance, the cavitations around those five throats were not vanished at the same time. When the cavitation was contracted and finally vanished, the absolute pressure on the blade surface was increased. When the cavitation was contracted around the throat located on the pressure side of blade surface, the pressure became high on the pressure side of blade surface. It caused the 1.4 times higher impulsive peak in the torque than the averaged value. On the other hand, when the cavitation was contracted around the throat located on the suction side of blade surface, the pressure became high on the suction side of blade surface. It caused the 0.4 times lower impulsive peak in the torque than the averaged value. The cavitation around the throat caused the large fluctuation in torque acting on the blade.

Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade

2012 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Ranjan Saha ◽  
Jens Fridh ◽  
Torsten Fransson
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Guide Vane ◽  
Leading Edge ◽  
Field Measurements ◽  
Co2 Concentration ◽  
Pressure Side ◽  
Trailing Edge ◽  
Nozzle Guide

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream. Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.

A New Test Facility to Investigate Film Cooling on a Non-Axisymmetric Contoured Turbine Endwall: Part I — Introduction and Aerodynamic Measurements

2015 ◽  
Author(s):  
Franz Puetz ◽  
Johannes Kneer ◽  
Achmed Schulz ◽  
Hans-Joerg Bauer
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Distribution ◽  
Film Cooling ◽  
Gas Turbines ◽  
Guide Vane ◽  
Leading Edge ◽  
Suction Side ◽  
Test Facility ◽  
Endwall Contouring

An increased demand for lower emission of stationary gas turbines as well as civil aircraft engines has led to new, low emission combustor designs with less liner cooling and a flattened temperature profile at the outlet. As a consequence, the heat load on the endwall of the first nozzle guide vane is increased. The secondary flow field dominates the endwall heat transfer, which also contributes to aerodynamic losses. A promising approach to reduce these losses is non-axisymmetric endwall contouring. The effects of non-axisymmetric endwall contouring on heat transfer and film cooling are yet to be investigated. Therefore, a new cascade test rig has been set up in order to investigate endwall heat transfer and film cooling on both a flat and a non-axisymmetric contoured endwall. Aerodynamic measurements that have been made prior to the upcoming heat transfer investigation are shown. Periodicity and detailed vane Mach number distributions ranging from 0 to 50% span together with the static pressure distribution on the endwall give detailed information about the aerodynamic behavior and influence of the endwall contouring. The aerodynamic study is backed by an oil paint study, which reveals qualitative information on the effect of the contouring on the endwall flow field. Results show that the contouring has a pronounced effect on vane and endwall pressure distribution and on the endwall flow field. The local increase and decrease of velocity and the reduced blade loading towards the endwall is the expected behavior of the 3d contouring. So are the results of the oil paint visualization, which show a strong change of flow field in the leading edge region as well as that the contouring delays the horse shoe vortex hitting the suction side.

Volumetric Velocimetry Measurements of Purge-Mainstream Interaction in a 1-Stage Turbine

2020 ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Complex Flow ◽  
Blade Passage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flow-field. Of particular interest to the designer is the effect of purge on the secondary flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and Computational Fluid Dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically-accessible 1-stage turbine rig. The experimental campaign was conducted using Volumetric Velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using URANS computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the roll-up of a horseshoe-vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flow-rate, was shown to modify the secondary flow field by enhancing the passage vortex, both in strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

An Experimental Investigation on the Influence of Periodic Unsteady Inflow Conditions on Leading Edge Film Cooling

2002 ◽  
Author(s):  
Stefan Wolff ◽  
Leonhard Fottner ◽  
Sabine Ardey
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Flow Behavior ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Injection Zone ◽  
Unsteady Inflow ◽  
Inflow Conditions

In order to close the gap in knowledge concerning the influence of periodic unsteady inflow conditions on the mixing process of film cooling jets, time resolved flow velocities and turbulent fluctuations in the injection zone of a linear large scale high pressure turbine cascade with leading edge film cooling were measured by means of the 3D hot-wire anemometry. The periodic impinging wakes are generated by a wake generator consisting of moving bars upstream of the cascade inlet plane. Near the stagnation point the blades are equipped with one row of film cooling holes on the suction side and one row on the pressure side. Mach number and Reynolds number are set to values typically found in modern gas turbines. At a density ratio of unity the blowing ratio is set to M = 0.7 and the Strouhal number is set to Sr = 0.31. The general flow structures which were determined by the steady state measurements — i.e. normal jet in cross flow behavior with the kidney shape vortex on the suction side and a second counter rotating pair of vortices underneath the kidney vortex on the pressure side — have been detected by the unsteady measurements as well. The large recirculation zone behind the pressure side injection hole, caused by the strong adverse pressure gradient and the lift off of the coolant jet, is not suppressed by the passing wakes but rather reinforced promoting potential hot spots in this area. The suction side coolant jet has almost disappeared when the wake leaves the suction side region. It undergoes a recovery process until the next wake hits again on the suction side.

Effects of Solid Particle Ingestion Through an HP Turbine

2012 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Gas Turbines ◽  
Rotor Blade ◽  
Leading Edge ◽  
Suction Side ◽  
Operating Conditions ◽  
Pressure Side ◽  
Trailing Edge ◽  
Premature Failure ◽  
Narrow Strip ◽  
Tracking Model

Modern gas turbines operate in severe dusty environments, and because of such harsh operating conditions, their blades experience significant degradation in service. This paper presents a numerical study of particle dynamics and erosion in an hp axial turbine stage. The flow field is solved separately from the solid phase and constitutes the necessary data in the particle trajectories simulations using a Lagrangian tracking model based on the finite element method. Several parameters consider a statistical description such as particle size, shape and rebound, in addition to the turbulence effect. A semi empirical erosion correlation is used to estimate erosion contours and blades deteriorations, knowing the locations and conditions of impacts. The trajectory and erosion results show high erosion rates over the pressure side of NGV near trailing edge, in addition to extreme erosion observed toward the root corner, due to high number of particles impacting with high velocities. On the suction side, erosion is mainly over a narrow strip from leading edge. Erosion in the rotor blade is shown along the leading edge and spreading over the fore of the blade suction side, owing to a flux of particles entering at high velocities and incidence. On the pressure side, regions of dense erosion are observed near the leading edge and trailing edge as well as the tip corner. Critical erosion spots seen over NGV and rotor blade are signs of a premature failure.

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