Endwall Effusion Cooling System Behaviour Within a High-Pressure Turbine Cascade: Part 1—Aerodynamic Measurements

2010 ◽  
Author(s):  
Marco Sacchi ◽  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Stefano Zecchi
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Measurement Techniques ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
High Pressure Turbine ◽  
Tangential Plane ◽  
Cooling Effects ◽  
Secondary Flow Field

The secondary flow field in a large-scale high-pressure turbine cascade with micro-holed endwall cooling has been investigated at the Genova Laboratory of Aerodynamics and Turbomachinery in cooperation with Avio S.p.A in the framework of the European Project AITEB-2. The experimental investigation has been performed for the baseline configuration, with a smooth solid endwall installed, and for the cooled configuration with a micro-holed endwall providing micro-jets ejection from the wall. Two different cooling flow rates were investigated and the experimental results are reported in the paper. Different measurement techniques have been employed to analyze the secondary flow field along the channel and in a downstream tangential plane. Particle Image Velocimetry has been utilized to quantify the blade-to-blade velocity components in a plane located close to the endwall and in the midspan plane. Hot-wire measurements have been performed in a tangential plane downstream of the blade trailing edges in order to survey the micro-jets effects on the secondary flows behavior. The total pressure distributions, for the different blowing conditions, have been measured in the downstream tangential plane by means of a Kiel pneumatic probe. The results, represented in color plots of velocity, pressure loss coefficient and turbulent kinetic energy distributions, allow the identification of the endwall effusion cooling effects on location and strength of the secondary vortical structures. The thermal investigation of the effusion system is discussed in Part 2 of the paper.

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.

Design Optimization of Profiled Endwall With Consideration of Cooling and Rim Seal Flow Effects

2016 ◽  
Author(s):  
Huimin Tang ◽  
Shuaiqiang Liu ◽  
Hualing Luo
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Great Influence ◽  
Optimization Procedure ◽  
Secondary Flows ◽  
High Pressure Turbine ◽  
Operation Condition ◽  
Turbine Performance

Profiled endwall is an effective method to improve aerodynamic performance of turbine. This approach has been widely studied in the past decade on many engines. When automatic design optimisation is considered, most of the researches are usually based on the assumption of a simplified simulation model without considering cooling and rim seal flows. However, many researchers find out that some of the benefits achieved by optimization procedure are lost when applying the high-fidelity geometry configuration. Previously, an optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM. This optimization procedure has been executed [12] to design profiled endwalls for a turbine cascade and a one-and-half stage axial turbine. Improvements of the turbine performance have been achieved. As the profiled endwall is applied to a high pressure turbine, the problems of cooling and rim seal flows should be addressed. In this work, the effects of rim seal flow and cooling on the flow field of two-stage high pressure turbine have been presented. Three optimization runs are performed to design the profiled endwall of Rotor-One with different optimization model to consider the effects of rim flow and cooling separately. It is found that the rim seal flow has a significant impact on the flow field. The cooling is able to change the operation condition greatly, but barely affects the secondary flow in the turbine. The influences of the profiled endwalls on the flow field in turbine and cavities have been analyzed in detail. A significant reduction of secondary flows and corresponding increase of performance are achieved when taking account of the rim flows into the optimization. The traditional optimization mechanism of profiled endwall is to reduce the cross passage gradient, which has great influence on the strength of the secondary flow. However, with considering the rim seal flows, the profiled endwall improves the turbine performance mainly by controlling the path of rim seal flow. Then the optimization procedure with consideration of rim seal flow has also been applied to the design of the profiled endwall for Stator Two.

Incidence Angle and Pitch–Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1993 ◽  
Vol 115 (3) ◽  
pp. 383-391 ◽  
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 deg, 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 percent 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 by 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.

Aerodynamics Performance of Endwall Film Cooling under the Influence of Purge Flow in High Pressure Turbine Cascade

2014 ◽  
Vol 629 ◽  
pp. 119-124
Author(s):  
W. Ghopa Wan Aizon ◽  
Kenichi Funazaki ◽  
Mohd Radzi Abu Mansor
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Film Cooling ◽  
Field Experiments ◽  
Cross Flow ◽  
High Pressure Turbine ◽  
Cooling Air ◽  
Secondary Flow Field

Modern gas turbine requires sophisticated cooling technologies to avoid thermal failure due to the extreme operating environment. Film cooling is one of the most important cooling technologies used for gas turbine hot-section components, particularly for blade aerofoil surfaces and endwall. Previous research has shown that the endwall region is considerably more difficult to cool than the blade aerofoil surfaces because of the existence of complex secondary flow structures such as horse-shoe vortex, cross flow and passage vortex in the blade passage. Therefore, this study focuses on aerodynamics interaction of the cooling air through the upstream slot with the secondary flow field. Experiments carried out using 5-holes Pitot tube have revealed the secondary flow field at blade downstream of linear cascade of high pressure turbine. A baseline condition without any leakage flows was compared with the leakage ejection case. Finally, both cases were validated by simulations from commercial software, ANSYS CFX.

scholarly journals The Secondary Flow Field of a Turbine Cascade With 3D Airfoil Design and Endwall Contouring at Off-Design Incidence

1999 ◽  
Author(s):  
Arno Duden ◽  
Leonhard Fottner
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
High Speed ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
Flow Angle ◽  
Radial Extent ◽  
Endwall Contouring ◽  
End Wall ◽  
Secondary Flow Field

A highly loaded turbine cascade with prismatic airfoils and straight endwalls was redesigned with the objective of reducing the secondary flow by applying end wall contouring and 3D airfoil design in the endwall regions. When tested at design conditions the flow field showed distinct improvements. The radial extent of the secondary flows was reduced and a decrease in secondary losses was observed (Duden et al., 1998). As an extension of this investigation, the effects of positive and negative incidence on the performance of the redesigned cascade have been evaluated and compared to the original cascade. The investigations were carried out in a high speed cascade wind tunnel. At negative incidence the redesigned cascade was observed to reduce the radial variation of the circumferential exit flow angle but to increase the magnitude of the secondary losses. At positive incidence, in comparison to the flowfield in the reference cascade, the radial extent of the secondary flows and the magnitude of the secondary losses were greatly reduced. The benefits provided by the 3D airfoil design and endwall contouring were even more obvious at positive incidence than at the design conditions.

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.

scholarly journals Experimental Research of the Secondary Flow in Rectilinear Turbine Cascades

1985 ◽  
Author(s):  
Ye Da-Jun ◽  
Zhou Li-Wei
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Experimental Research ◽  
Turbine Cascade ◽  
Experiment Data ◽  
Loss Model ◽  
Turbine Cascades ◽  
Secondary Flow Field

For studying the secondary flow in a turbine cascade, the flow field is measured in detail. The measurements of pressure and velocity are taken at various axial planes upstream of, within, and downstream of the cascade by a 4-hole probe. The static pressures are taken on the endwall, suction and pressure surfaces. By treating the experiment data the mechanism of the secondary flow field and the loss model are proposed in this paper.

Numerical Investigations on Effect of Inflow Parameters on Development of Secondary Flow Field for Linear LP Turbine Cascade

2021 ◽  
Author(s):  
Anand P. Darji ◽  
Beena D. Baloni ◽  
Chetan S. Mistry
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Turbulence Model ◽  
Turbulence Intensity ◽  
Numerical Study ◽  
Turbine Cascade ◽  
Wall Flow ◽  
End Wall ◽  
Inflow Conditions ◽  
Secondary Flow Field

Abstract End wall flows contribute the most crucial role in loss generation for axial flow turbine and compressor blades. These losses lead to modify the blade loading and overall performance in terms of stable operating range. Present study aimed to determine the end wall flow streams in a low speed low pressure linear turbine cascade vane using numerical approach. The study includes two sections. The first section includes an attempt to understand different secondary flow streams available at end wall. Location of generation of horseshoe vortex streams and subsequent vortex patterns are identified in the section. The selection of suitable turbulence model among SST (Shear Stress Transport) k–ω and SST γ–θ to identify end wall flow streams is studied in prior in the section. The steady state numerical study is performed using Reynolds Averaged Navier-Stoke’s Equations closed by SST γ–θ turbulence model. The computational results are validated with experimental results available in the literature and are found to be in good agreement. The study is extended for different inflow conditions in later section. The second section includes effect of flow incidence and turbulence intensity on the end wall secondary flow field. Inflow incidences considered for the study are −20°, −10°, 0° (design incidence), +10° and +20°. The inlet turbulence intensities are varied by 1% and 10% for each case. The results revealed different secondary flow patterns at an end wall and found the change in behavior with an inflow conditions. SST γ–θ turbulence model with lower turbulence intensity is more suitable to identify such flow behavior.

Effects of Suction and Injection Purge-Flow on the Secondary Flow Structures of a High-Work Turbine

2008 ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Flow Structures ◽  
Turbine Efficiency ◽  
Flow Mechanisms ◽  
Purge Flow ◽  
High Work ◽  
Secondary Flow Field

In high-pressure turbines, a small amount of air is ejected at the hub rim seal, to cool and prevent the ingestion of hot gases into the cavity between the stator and the disk. This paper presents an experimental study of the flow mechanisms that are associated with injection through the hub rim seal at the rotor inlet. Two different injection rates are investigated: nominal sucking of −0.1% of the main massflow and nominal blowing of 0.9%. This investigation is executed on a one-and-1/2-stage axial turbine. The results shown here come from unsteady and steady measurements, which have been acquired upstream and downstream of the rotor. The paper gives a detailed analysis of the changing secondary flow field as well as unsteady interactions associated with the injection. The injection of fluid causes a very different and generally more unsteady flow field at the rotor exit near the hub. The injection causes the turbine efficiency to deteriorate by about 0.6%.

Migration of Combustor Exit Profiles Through High Pressure Turbine Vanes

2007 ◽  
Author(s):  
M. D. Barringer ◽  
M. D. Polanka ◽  
J. P. Clark ◽  
P. J. Koch ◽  
K. A. Thole
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Total Pressure ◽  
Secondary Flows ◽  
Working Fluid ◽  
Outer Diameter ◽  
High Pressure Turbine ◽  
Flow Angle ◽  
Radial Temperature ◽  
Turbine Vane

The high pressure turbine stage within gas turbine engines is exposed to combustor exit flows that are nonuniform in both stagnation pressure and temperature. These highly turbulent flows typically enter the first stage vanes with significant spatial gradients near the inner and outer diameter endwalls. These gradients can result in secondary flow development within the vane passage that is different than what classical secondary flow models predict. The heat transfer between the working fluid and the turbine vane surface and endwalls is directly related to the secondary flows. The goal of the current study was to examine the migration of different inlet radial temperature and pressure profiles through the high turbine vane of a modern turbine engine. The tests were performed using an inlet profile generator located in the Turbine Research Facility (TRF) at the Air Force Research Laboratory (AFRL). Comparisons of area-averaged radial exit profiles are reported as well as profiles at three vane pitch locations to document the circumferential variation in the profiles. The results show that the shape of the total pressure profile near the endwalls at the inlet of the vane can alter the redistribution of stagnation enthalpy through the airfoil passage significantly. Total pressure loss and exit flow angle variations are also examined for the different inlet profiles.

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