Investigations on the interaction between the front and aft purge flow and the downstream vane of 1.5-stage turbine

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
He Zhenpeng ◽  
Zhou Jiaxing ◽  
Xin Jia ◽  
Yang Chengquan ◽  
Li Baichun
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Suction Side ◽  
Secondary Flows ◽  
Wall Structure ◽  
Pressure Side ◽  
Turbine Efficiency ◽  
Passage Vortex ◽  
Purge Flow ◽  
End Wall

Abstract The present work reports the influence of the 1.5-stage turbine flow field by the front and aft rim seal flow. The interaction between the front and aft purge flow and the mainstream of a 1.5-stage turbine was numerically simulated, and the influence of the front and aft purge flow on the downstream vane was analyzed separately. The results show that the front purge flow is distributed at the higher radius of second vane inlet, which changes the position of the blade hub secondary flows, and the aft purge flow is distributed at the low radius. The purge flow at different locations in the aft cavity exit forms shear induced vortex, pressure and suction side legs of the egress, which converges with the suction and pressure side legs of the horse vortex to form vane hub passage vortex. The increased purge flow rate in both the front and aft cavities significantly increases the sealing effectiveness of the rim seal, but also causes a reduction in turbine efficiency. The combined effect of the front and aft purge flow reduces the turbine efficiency of the end-wall structure by 0.3619, 0.9062, 1.5004, 2.0188 and 2.509% at IR = 0, IR = 0.5%, IR = 0.9%, IR = 1.3% and IR = 1.7%.

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.

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.

Effect of Purge on the Secondary Flow-Field of a Gas Turbine Blade-Row

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
B. D. J Schreiner ◽  
M. Wilson ◽  
Y. S. Li ◽  
C. M. Sangan
Keyword(s):  
Computational Study ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Pressure Side ◽  
Suction Surface ◽  
Blade Row ◽  
Purge Flow ◽  
Rotational Direction ◽  
Secondary Flow Field

Abstract Turbine disc cooling is required to protect vulnerable components from exposure to the high temperatures found in the mainstream gas path. Purge air, bled from the latter stages of the compressor, is introduced to the turbine wheelspace at low radius before exiting through the rim-seal at the periphery of the discs. The unsteady, complex flowfield that arises from the interaction between the purge and mainstream gases modifies the structure of secondary flows within the blade passage. A computational study was conducted using an unsteady Reynolds-averaged Navir–Stokes (RANS) solver, modeling an engine-representative turbine stage. Preliminary results were validated using experimental data from a test rig. The baseline secondary flowfield was described, in the absence of purge flow, demonstrating the classical rollup of the horseshoe vortex and subsequent convection of the two legs downstream. The unsteady behavior of the model was investigated and addressed, resulting in recommendations for modeling interaction phenomena in turbines. A superposed purge flow, resulting in egress through the upstream rim-seal, was shown to modify the secondary flowfield in the turbine annulus. The most notable effect of egress was the formation of a large plume forming near the pressure minima associated with the blade suction surface. The egress was turned by the mainstream flow, creating a vortical structure consistent in rotational direction to the pressure-side leg of the horseshoe vortex; the pressure-side leg was subsequently strengthened and showed an increased radial migration relative to the unpurged case. The egress plume was also shown to overwhelm the suction-side leg of the horseshoe vortex, reducing its strength.

Formation and Transport of Secondary Flows Caused by Vortex-Blade Interaction in a High Pressure Turbine

2015 ◽  
Author(s):  
Zuo-Jun Wei ◽  
Wei-Yang Qiao ◽  
Ping-Ping Chen ◽  
Jian Liu
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Pressure Gradient ◽  
Suction Side ◽  
Secondary Flows ◽  
Pressure Side ◽  
High Pressure Turbine ◽  
Suction Surface ◽  
Blade Loading ◽  
Passage Vortex

As modern turbines are designed with low aspect ratio and high blade loading, secondary flow interactions become more important. In the present work, numerical simulation is performed in a two-stage high-pressure turbine with divergent meridional passage to investigate the transport and interaction of secondary vortex from the first stage rotor within the second stage’s stator. Scale-Adaptive Simulation model coupled with Shear Stress Transport model (SAS-SST turbulence model) is used to capture the flow structures caused by the interaction in the second stator. Coupled with the passage vortex of the first rotor, the shed vortex rotates opposite in the direction and has comparable strength. As both of these vortices convect downstream to the stator bladerow, each deforms into two legs on the pressure and suction sides in the passage. In the passage due to the cross pressure gradient by blade loading, all the low-momentum fluid contained in these vortices moves towards the suction side. Besides, with the existing static pressure gradient in radial direction and vortex dynamics, the suction-side leg and the pressure-side leg move in different radial directions. The suction side leg of incoming passage vortex moves towards the endwall along the suction surface and interacts with the developing passage vortex of the second stator. The incoming shed vortex moves towards the midspan and rolls up the boundary layer fluid from suction surface. Due to the interactions between the incoming shed vortices from the hub and casing and the boundary layer of second stator, two counter-rotating vortices are formed near the midspan. Additional high loss is found there at the outlet plane, which has a comparable magnitude to the endwall secondary loss. The pressure side leg of the incoming passage vortex remains in a certain span with that of the incoming shed vortex and is not engulfed by the developing passage vortex.

Numerical Investigation of the Interaction Between Upstream Purge Flow and Mainstream in a Highly-Loaded Turbine

2014 ◽  
Author(s):  
Wei Jia ◽  
Huoxing Liu
Keyword(s):  
Computational Study ◽  
Secondary Flows ◽  
Axial Position ◽  
Design Parameters ◽  
Aerodynamic Design ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Purge Flow ◽  
Wall Profile ◽  
End Wall

In modern high pressure turbine, a certain amount of cooling air is bled off from compressor and then directly injected into the inter-stage gap between the stationary and rotating components. This paper presents a computational study of the interaction between mainstream flow and purge flow, with the objectives of evaluating the impacts of purge flow on turbine aerodynamic design parameters, tracing the loss sources involved with the injection of purge flow and describing the secondary flows near the hub region. The purge flow through the rim seal has been varied between 0–2% of the main flow and the axial position of rim seal has been also changed. Steady-state simulation using a 3D RANS solver is presented with particular emphasis on the mechanisms of loss production. It is found that purge flow has a primary effect on the spanwise distribution of turbine aerodynamic design parameters, especially near the hub region. The losses brought about by the injection of purge flow can be divided into four parts: reaction redistribution between vane and blade in one stage, a shear layer between purge flow and mainstream flow due to different circumferential momentum, hub passage vortex interaction and decrease of output work near the end wall. However these four loss sources are not independent of each other. Shear induced vortex (SIV) and slot leakage vortex (SLV) appear near the hub region after purge flow is introduced. The shear induced vortex is formed due to the shear interaction between mainstream flow and purge flow which develop into hub passage vortex. The slot leakage vortex is formed due to the relative motion of the cavity disks and its strength is relatively weak compared with the shear induce vortex. The results gained from this paper may give some useful guidelines for turbine aerodynamic design and end wall profile optimization.

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.

Effects of Cavity Purge Flow on Intermediate Turbine Duct Flowfield

2018 ◽  
Author(s):  
Jun Liu ◽  
Qiang Du ◽  
Guang Liu ◽  
Pei Wang ◽  
Hongrui Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Design Criterion ◽  
Operating Conditions ◽  
Duct Flow ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Cavity Structure ◽  
Flow Mechanisms ◽  
Purge Flow

To increase the power output without adding additional stages, ultra-high bypass ratio engine, which has larger diameter low pressure turbine, attracts more and more attention because of its huge advantage. This tendency will lead to aggressive (high diffusion) intermediate turbine duct design. Much work has been done to investigate flow mechanisms in this kind of duct as well as its design criterion with numerical and experimental methods. Usually intermediate turbine duct simplified from real engine structure was adopted with upstream and downstream blades. However, cavity purge mass flow exists to disturb the duct flow field in real engine to change its performance. Naturally, the wall vortex pairs would develop in different ways. In addition to that, purge flow rate changes at different engine representative operating conditions. This paper deals with the influence of turbine purge flow on the aerodynamic performance of an aggressive intermediate turbine duct. The objective is to reveal the physical mechanism of purge flow ejected from the wheel-space and its effects on the duct flow field. Ten cases with and without cavity are simulated simultaneously. On one hand, the influence of cavity structure without purge flow on the flow field inside duct could be discussed. On the other hand, the effect of purge flow rate on flow field could be analyzed to investigate the mechanisms at different engine operating conditions. According to this paper, cavity structure is beneficial for pressure loss. And the influence concentrates near hub and duct inlet.

The Effect of Stator-Rotor Hub Sealing Flow on the Mainstream Aerodynamics of a Turbine

2006 ◽  
Author(s):  
Kevin Reid ◽  
John Denton ◽  
Graham Pullan ◽  
Eric Curtis ◽  
John Longley
Keyword(s):  
Steady State ◽  
Entropy Generation ◽  
Flow Rate ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Flow Conditions ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Mainstream Flow ◽  
Flow Interactions

An investigation into the effect of stator-rotor hub gap sealing flow on turbine performance is presented. Efficiency measurements and rotor exit area traverse data from a low speed research turbine are reported. Tests carried out over a range of sealing flow conditions show that the turbine efficiency decreases with increasing sealant flow rate but that this penalty is reduced by swirling the sealant flow. Results from time-accurate and steady-state simulations using a three-dimensional multi-block RANS solver are presented with particular emphasis paid to the mechanisms of loss production. The contributions toward entropy generation of the mixing of the sealant fluid with the mainstream flow and of the perturbed rotor secondary flows are assessed. The importance of unsteady stator wake/sealant flow interactions is also highlighted.

Numerical Predictions of Turbine Cascade Secondary Flows and Heat Transfer With Inflow Turbulence

2020 ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Leading Edge ◽  
Suction Side ◽  
Lateral Spreading ◽  
Secondary Flows ◽  
Pressure Side ◽  
Initial Flow ◽  
Numerical Predictions ◽  
Inflow Turbulence

Abstract Turbine passage secondary flows are studied for a large rounded leading edge airfoil geometry considered in the experimental investigation of Varty et al. (J. Turbomach. 140(2):021010) using high resolution Large Eddy Simulation (LES). The complex nature of secondary flow formation and evolution are affected by the approach boundary layer characteristics, components of pressure gradients tangent and normal to the passage flow, surface curvature, and inflow turbulence. This paper presents a detailed description of the secondary flows and heat transfer in a linear vane cascade at exit chord Reynolds number of 5 × 105 at low and high inflow turbulence. Initial flow turning at the leading edge of the inlet boundary layer leads to a pair of counter-rotating flow circulation in each half of the cross-plane that drive the evolution of the pressure-side and suction side of the near-wall vortices such as the horseshoe and leading edge corner vortex. The passage vortex for the current large leading-edge vane is formed by the amplification of the initially formed circulation closer to the pressure side (PPC) which strengthens and merges with other vortex systems while moving toward the suction side. The predicted suction surface heat transfer shows good agreement with the measurements and properly captures the augmented heat transfer due to the formation and lateral spreading of the secondary flows towards the vane midspan downstream of the vane passage. Effects of various components of the secondary flows on the endwall and vane heat transfer are discussed in detail.

A Low Pressure Turbine With Profiled End Walls and Purge Flow Operating With a Pressure Side Bubble

2011 ◽  
Author(s):  
P. Jenny ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
M. Brettschneider ◽  
J. Gier
Keyword(s):  
Computational Study ◽  
Leading Edge ◽  
Low Pressure ◽  
Fast Response ◽  
Turbine Rotor ◽  
Operating Point ◽  
Pressure Side ◽  
Low Pressure Turbine ◽  
Purge Flow ◽  
End Wall

This paper presents an experimental and computational study of non-axisymmetric rotor end wall profiling in a low pressure turbine. End wall profiling has been proven to be an effective technique to reduce both turbine blade row losses and the required purge flow. For this work a rotor with profiled end walls on both hub and shroud is considered. The rotor tip and hub end walls have been designed using an automatic numerical optimisation that is implemented in an in-house MTU code. The end wall shape is modified up to the platform leading edge. Several levels of purge flow are considered in order to analyze the combined effects of end wall profiling and purge flow. The non-dimensional parameters match real engine conditions. The 2-sensor Fast Response Aerodynamic Probe (FRAP) technique system developed at ETH Zurich is used in this experimental campaign. Time-resolved measurements of the unsteady pressure, temperature and entropy fields between the rotor and stator blade rows are made. For the operating point under investigation the turbine rotor blades have pressure side separations. The unsteady behavior of the pressure side bubble is studied. Furthermore, the results of unsteady RANS simulations are compared to the measurements and the computations are also used to detail the flow field with particular emphasis on the unsteady purge flow migration and transport mechanisms in the turbine main flow containing a rotor pressure side separation. The profiled end walls show the beneficial effects of improved measured efficiency at this operating point, together with a reduced sensitivity to purge flow.

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