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.

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%.

The Highly Loaded Aerodynamic Design and Performance Enhancement of a Helium Compressor

2010 ◽  
Author(s):  
Tingfeng Ke ◽  
Qun Zheng
Keyword(s):  
Boundary Layers ◽  
Pressure Ratio ◽  
Secondary Flows ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Radial Compression ◽  
Aerodynamic Design ◽  
Wall Boundary ◽  
End Wall ◽  
Highly Loaded

A design study of the multistage axial helium compressor of a 300MWe nuclear gas turbine is presented in this paper. Helium compressor is characterized by shorter blades, narrow flow channels, numerous stages and longer slim rotor, which result in losses due to blade surface and end wall boundary layers growths, secondary flows and clearance leakage flows, any occurrence of flow separation and stage mismatch. Therefore, the purpose of this paper is to improve and optimize the aerodynamic design of the helium compressor. The property of helium is different from that of air, so how to choose the design parameters of a helium compressor is discussed first. And then how to shorten the length of the helium compressor or how to decrease the number of stages for a certain pressure ratio by increasing the stage loading are investigated. The new highly loaded helium compressor of larger flow coefficient and high reaction is designed and optimized. The three-dimensional flow patterns in a helium stage are simulated with CFD software (NUMECA). Adjusting the position of blade maximum camber deflection position; redistributing radial compression work; modifying the configuration of blade at inlet and outlet; using CDA technique to optimize blade profile; 3D blading techniques to mitigate end wall boundary layers and corner separation have improved the performance of the first stage of the helium compressor cascades.

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.

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.

Effect of Upstream Wake With Vortex on Turbine Blade Platform Film Cooling With Simulated Stator-Rotor Purge Flow

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Dong-Ho Rhee ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Labyrinth Seal ◽  
Delta Wings ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Linear Cascade ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Purge Flow

Detailed film cooling effectiveness distributions were experimentally obtained on a turbine blade platform within a linear cascade. The film cooling effectiveness distributions were obtained on the platform with upstream disturbances used to simulate the passing vanes. Cylindrical rods, placed upstream of the blades, simulated the wake created by the trailing edge of the stator vanes. The rods were placed at four locations to show how the film cooling effectiveness was affected relative to the vane location. In addition, delta wings were placed upstream of the blades to model the effect of the passage vortex (generated in the vane passage) on the platform film cooling effectiveness. The delta wings create a vortex similar to the passage vortex as it exits the upstream vane passage. The film cooling effectiveness was measured with the delta wings placed at four location, to investigate the effect of the passing vanes. Finally, the delta wings were coupled with the cylindrical rods to examine the combined effect of the upstream wake and passage vortex on the platform film cooling effectiveness. The detailed film cooling effectiveness distributions were obtained using pressure sensitive paint in the five blade linear cascade. An advanced labyrinth seal was placed upstream of the blades to simulate purge flow from a stator-rotor seal. The coolant flow rate varied from 0.5% to 2.0% of the mainstream flow, while the Reynolds number of the mainstream flow remained constant at 3.1×105 (based on the inlet velocity and chord length of the blade). The film cooling effectiveness was not significantly affected with the upstream rod. However, the vortex generated by the delta wings had a profound impact on the film cooling effectiveness. The vortex created more turbulent mixing within the blade passage, and the result is reduced film cooling effectiveness through the entire passage. When the vane induced secondary flow is included, the need for additional platform cooling becomes very obvious.

Investigation of a Novel Secondary Flow Feature in a Turbine Cascade With End Wall Profiling

2005 ◽  
Vol 127 (1) ◽  
pp. 209-214 ◽  
Author(s):  
Grant Ingram ◽  
David Gregory-Smith ◽  
Neil Harvey
Keyword(s):  
Secondary Flow ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Unexpected Result ◽  
Full Potential ◽  
Flow Angle ◽  
Passage Vortex ◽  
Flow Feature ◽  
New Feature ◽  
End Wall

A novel secondary flow feature, previously unreported for turbine blading as far as the authors are aware, has been discovered. It has been found that it is possible to separate part of the inlet boundary layer on the blade row end wall as it is being over-turned and rolled up into the passage vortex. This flow feature has been discovered during a continuing investigation into the aerodynamic effects of non-axisymmetric end wall profiling. Previous work, using the low speed linear cascade at Durham University, has shown the potential of end wall profiling for reducing secondary losses. The latest study, the results of which are described here, was undertaken to determine the limits of what end wall profiling can achieve. The flow has been investigated in detail with pressure probe traversing and surface flow visualization. This has found that the inlet boundary locally separates, on the early suction side of the passage, generating significant extra loss which feeds directly into the core of the passage vortex. The presence of this new feature gives rise to the unexpected result that the secondary flow, as determined by the exit flow angle deviations and levels of secondary kinetic energy, can be reduced while at the same time the loss is increased. CFD was found to calculate the secondary flows moderately well compared with measurements. However, CFD did not predict this new feature, nor the increase in loss it caused. It is concluded that the application of non-axisymmetric end wall profiling, although it has been shown to be highly beneficial, can give rise to adverse features that current CFD tools are unable to predict. Improvements to CFD capability are required in order to be able to avoid such features, and obtain the full potential of end wall profiling.

Reduction in Secondary Flows and Losses in a Turbine Cascade by Upstream Boundary Layer Blowing

1993 ◽  
Author(s):  
Thomas E. Biesinger ◽  
David G. Gregory-Smith
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Turbine Cascade ◽  
Streamwise Vorticity ◽  
Passage Vortex ◽  
End Wall ◽  
Tangential Blowing ◽  
Accounting Procedure

The effect of upstream tangential blowing on the secondary flows has been studied in a turbine cascade of rotor blades. The aim is to reduce the secondary flows and losses, but in the evaluation an accounting procedure for the energy for blowing is required. The experimental results show that the effect of the increasing blowing is first to thicken the inlet boundary layer, giving greater secondary flow and more loss, and then as re-energisation of the inlet boundary layer takes place together with increasing counter streamwise vorticity, the passage vortex is progressively weakened, with a corresponding reduction in loss. Low rather than high angle blowing is shown to be more effective as the jet is kept closer to the end wall, and strong similarities could be obtained with the flow patterns from previous work with a skewed inlet boundary layer. However when the energy for inlet blowing is included, no net gain is achieved due mainly to the mixing loss of the injected air. Overall gains may be achievable, if combined with such features as injection for film cooling.

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.

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