Impact of Individual High-Pressure Turbine Rotor Purge Flows on Turbine Center Frame Aerodynamics

2017 ◽  
Author(s):  
S. Zerobin ◽  
C. Aldrian ◽  
A. Peters ◽  
F. Heitmeir ◽  
E. Göttlich
Keyword(s):  
High Pressure ◽  
Pressure Loss ◽  
Turbine Rotor ◽  
Flow Conditions ◽  
High Pressure Turbine ◽  
Reference Case ◽  
University Of Technology ◽  
Purge Flow ◽  
Generation Mechanisms ◽  
The Impact

This paper presents an experimental study of the impact of individual high-pressure turbine purge flows on the main flow in a downstream turbine center frame duct. Measurements were carried out in a product-representative one and a half stage turbine test setup, installed in the Transonic Test Turbine Facility at Graz University of Technology. The rig allows testing at engine-relevant flow conditions, matching Mach, Reynolds, and Strouhal number at the inlet of the turbine center frame. The reference case features four purge flows differing in flow rate, pressure, and temperature, injected through the hub and tip, forward and aft cavities of the high-pressure turbine rotor. To investigate the impact of each individual cooling flow on the flow evolution in the turbine center frame, the different purge flows were switched off one-by-one while holding the other three purge flow conditions. In total, this approach led to six different test conditions when including the reference case and the case without any purge flow ejection. Detailed measurements were carried out at the turbine center frame duct inlet and outlet for all six conditions and the post-processed results show that switching off one of the rotor case purge flows leads to an improved duct performance. In contrast, the duct exit flow is dominated by high pressure loss regions if the forward rotor hub purge flow is turned off. Without the aft rotor hub purge flow, a reduction in duct pressure loss is determined. The purge flows from the rotor aft cavities are demonstrated to play a particularly important role for the turbine center frame aerodynamic performance. In summary, this paper provides a first-time assessment of the impact of four different purge flows on the flow field and loss generation mechanisms in a state-of-the-art turbine center frame configuration. The outcomes of this work indicate that a high-pressure turbine purge flow reduction generally benefits turbine center frame performance. However, the forward rotor hub purge flow actually stabilizes the flow in the turbine center frame duct and reducing this purge flow can penalize turbine center frame performance. These particular high-pressure turbine/turbine center frame interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

The Behavior of Turbine Center Frames Under the Presence of Purge Flows

2017 ◽  
Author(s):  
S. Zerobin ◽  
A. Peters ◽  
S. Bauinger ◽  
A. Ramesh ◽  
M. Steiner ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Pressure Loss ◽  
Measurement Data ◽  
Leading Edge ◽  
Turbine Rotor ◽  
High Pressure Turbine ◽  
Oil Flow ◽  
Purge Flow ◽  
Cooling Air

This paper deals with the influence of high-pressure turbine purge flows on the aerodynamic performance of turbine center frames. Measurements were carried out in a product-representative one and a half stage turbine test setup, installed in the Transonic Test Turbine Facility at Graz University of Technology. The rig allows testing at engine-relevant flow conditions, matching Mach, Reynolds, and Strouhal number at the inlet of the turbine center frame. Four individual purge mass flows differing in flow rate, pressure, and temperature were injected through the hub and tip, forward and aft cavities of the unshrouded high-pressure turbine rotor. Two turbine center frame designs (differing in area distribution and inlet-to-exit radial offset), equipped with non-turning struts, were tested and compared. For both configurations, aerodynamic measurements at the duct inlet and outlet as well as oil flow visualizations through the turbine center frame were performed. The acquired measurement data illustrate that the interaction of the ejected purge flow with the main flow enhances the secondary flow structures through the turbine center frame duct. Depending on the purge flow rates, the radial migration of purge air onto the strut surfaces directly impacts the loss behavior of the duct. While the duct loss is demonstrated to be primarily driven by the core flow between two duct struts, the losses associated with the flow close to the struts and in the strut wakes are highly dependent on the relative position between the high-pressure turbine vane and the strut leading edge, as well as the interaction between vane wake and ejected purge flow. Hence, while the turbine center frame duct pressure loss depends on the duct geometric characteristics it is also influenced by the presence and rate of the high-pressure turbine purge flows. This first-time experimental assessment demonstrates that a reduction in the high-pressure turbine purge and cooling air requirement not only benefits the engine system performance by decreasing the secondary flow taken from the high-pressure compressor but also by lowering the turbine center frame total pressure loss.

Aerodynamic Performance of Turbine Center Frames With Purge Flows—Part II: The Influence of Individual Hub and Tip Purge Flows

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Stefan Zerobin ◽  
Christian Aldrian ◽  
Andreas Peters ◽  
Franz Heitmeir ◽  
Emil Göttlich
Keyword(s):  
High Pressure ◽  
Operating Conditions ◽  
High Pressure Turbine ◽  
Flow Rates ◽  
Purge Flow ◽  
Flow Evolution ◽  
Generation Mechanisms ◽  
The Impact ◽  
First Time ◽  
Time Assessment

The aerodynamic behavior of turbine center frame (TCF) ducts under the presence of high-pressure turbine (HPT) purge flows was experimentally investigated in this two-part paper. While the first part of the paper demonstrated the impact of varying the purge flow rates (PFR) on the loss behavior of two different TCF designs, the second part concentrates on the influence of individual hub and tip purge flows on the main flow evolution and loss generation mechanisms through the TCF ducts. Therefore, measurements were conducted at six different operating conditions in a one and a half stage turbine test setup, featuring four individual purge flows injected through the hub and tip, forward and aft cavities of the HPT rotor. The outcomes of this first-time assessment indicate that a HPT purge flow reduction generally benefits TCF performance. Decreasing one of the rotor case PFRs leads to an improved duct pressure loss. The purge flows from the rotor aft hub and tip cavities are demonstrated to play a particularly important role for improving the duct aerodynamic behavior. In contrast, the forward rotor hub purge flow actually stabilizes the flow in the TCF duct and reducing this purge flow can penalize TCF performance. These particular HPT/TCF interactions should be taken into account whenever high-pressure turbine purge flow reductions are pursued.

Steady CFD Simulation of a High Pressure Turbine Rotor With Hub and Shroud Purge Flow

2018 ◽  
Author(s):  
Wolfgang Sanz ◽  
Stefan Zerobin ◽  
Manfred Egger ◽  
Pascal Bader ◽  
Paul Pieringer ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Cfd Simulation ◽  
Turbine Rotor ◽  
High Pressure Turbine ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Contour Plots ◽  
Purge Flow ◽  
Layer Flow

Purge air is injected at the hub and shroud of axial turbines in order to avoid hot gas entering the gaps between stationary and rotating blade rows. The purge flows considerably interact with the main flow and influence the secondary flow like the tip leakage vortex. Therefore, at Graz University of Technology the flow in a product-representative one-and-a-half stage test turbine under the influence of purge flows was investigated. Four individual purge mass flows differing in flow rate, pressure, and temperature were injected through hub and tip cavities before and after the unshrouded high-pressure turbine rotor. In order to get more insight into the cavity flows and the flow evolution in the rotor this configuration is studied with a steady CFD simulation with and without purge flows. It was found that the secondary flow and especially the tip leakage vortex is significantly influenced by the purge flow which varies in circumferential direction. The differences between purge and zero-purge flow conditions are discussed with the help of radial distributions and contour plots of stream-wise vorticity. Streamlines allow to follow the path of the purge flows in the rotor and show the radial displacement of the secondary flow vortices. Wall streamlines describe the changes in the boundary layer flow and their effect on the vorticity after the trailing edge.

Flow Topology Optimization of a Cooling Passage for a High Pressure Turbine Blade

2017 ◽  
Author(s):  
J. Iseler ◽  
T. J. Martin
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Topology Optimization ◽  
Pressure Loss ◽  
High Pressure Turbine ◽  
Flow Topology ◽  
Local Flow ◽  
Design Modification ◽  
Cooling Passage ◽  
The Impact

This paper deals with a topology optimization of internal cooling passages within high pressure turbine blades in order to deliver fully three dimensional designs that optimize the local flow physics. By applying the implemented optimality criteria, a new individual passage design with minimized amount of recirculation is achieved, leading to a reduced total pressure loss. In contrary to traditional parametric approaches, where a CFD run is needed after each design modification, the applied topology optimization acts as a co-simulation and is finished after a single run where the initial geometry represents the available design space. The CFD runs for optimization and the subsequent verification of the flow passages assume steady state take-off conditions. The verification includes a flow simulation to check the pressure loss of the optimized passage design. In a second step, a loosely coupled conjugate heat transfer procedure including external turbine flow, coolant flow and heat conduction of the solid (blade, platform and attachment) is applied to predict the impact on the heat transfer. By running a FEM simulation afterwards, the stresses are computed and compared with those from the reference design.

Impact of Varying High- and Low-Pressure Turbine Purge Flows on a Turbine Center Frame and Low-Pressure Turbine System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
A. Peters ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Flow Structures ◽  
Flow Conditions ◽  
High Pressure Turbine ◽  
Inlet Flow ◽  
Low Pressure Turbine ◽  
The Impact ◽  
Inflow Conditions

Abstract This paper presents the experimental and numerical evaluation and comparison of the different flow fields downstream of a turbine center frame duct and a low-pressure turbine (LPT) stage, generated by varying the inlet flow conditions to the turbine center frame (TCF) duct. The measurements were carried out in an engine-representative two-stage two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. The rig consists of a high-pressure turbine (HPT) and a LPT turbine stage, connected via a TCF with non-turning struts. Four individual high-pressure turbine purge flowrates and two low-pressure turbine purge flowrates were varied to achieve different engine-relevant TCF and LPT inlet flow conditions. The experimental data were acquired by means of five-hole-probe (5HP) area traverses upstream and downstream of the TCF and downstream of the LPT. A steady Reynolds-averaged Navier–Stokes (RANS) simulation taking all purge flows in account was used for comparison, and additional insights are gained from a numerical variation of the HPT and LPT purge flowrates. The focus of this study is on the impact of the variations in TCF inlet conditions on the secondary flow generation through the TCF duct and the carryover effects on the exit flow field and performance of the LPT stage. Existing work is limited by either investigating multistage LPT configurations with generally very few measurements behind the first stage or by not including relevant HPT secondary flow structures in setting up the LPT inflow conditions. This work addresses both of these shortcomings and presents new insight into the TCF and LPT aerodynamic behavior at varying the HPT and LPT purge flows. The results demonstrate the importance of the HPT flow structures and their evolution through the TCF duct for setting up the LPT inflow conditions and ultimately for assessing the performance of the first LPT stage.

scholarly journals Novel high-pressure turbine purge control features for increased stage efficiency

2017 ◽  
Vol 1 ◽  
pp. 68MK5V ◽  
Author(s):  
Rainer Schädler ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Gregor Schmid ◽  
Tilmann auf dem Kampe ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Gas Turbines ◽  
High Pressure Turbine ◽  
Axial Turbine ◽  
Seal Design ◽  
Geometrical Features ◽  
Purge Flow ◽  
The Impact ◽  
Stage Efficiency

AbstractRim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.

3D CFD Ingestion Evaluation of a High Pressure Turbine Rim Seal Disk Cavity

2008 ◽  
Author(s):  
A. V. Mirzamoghadam ◽  
G. Heitland ◽  
M. C. Morris ◽  
J. Smoke ◽  
M. Malak ◽  
...  
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Steady Solution ◽  
Mixing Efficiency ◽  
Cfd Model ◽  
High Pressure Turbine ◽  
Stator Vane ◽  
Purge Flow ◽  
Model Setup ◽  
The Impact

The amount of cooling air assigned to seal high pressure turbine rim cavities is critical for performance as well as component life. Less air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk life. Excessive purge air adversely affects performance. The minimum purge (i.e. sealing) air requirement to control ingestion is also influenced by annulus circumferential pressure fluctuation present over the rim seal cavity. Its interaction with the platform gap resistance and the amount of purge air needs to be understood in order to reliably predict performance and component life. Work has commenced to investigate opportunities in reducing disk cavity purge flow requirements by studying ways to control ingestion. The study has been initiated with 3D CFD model setup/run mode options to benchmark main/cavity flow field interactions. The selection of the appropriate CFD model fidelity, however, is one of the main goals of this work. The CFD model phase has 3 options to be evaluated; 1) steady solution with mixing plane aft of the cavity, 2) steady solution with mixing plane forward of the cavity, 3) unsteady solution. Option 1 has been completed and is the subject of this paper. A reference HP turbine stage and disk cavity from an engine design was selected for the CFD study. The steady flow solution model captured the oscillatory movement and penetration depth of ingestion by varying purge flow rate and observing the impact on the mixing plane forward and aft of the disk cavity. Moreover, the influence of upstream stator vane airfoil fillet shape was also investigated. The entrained flow was established by starving the cavity and integrating the outflow along the disk. This value along with the nominal and intermediate cavity purge flows were validated against relevant sealing flow design correlations. At a radial location near the rim, an ingestion mixing efficiency value versus purge flow rate was obtained which correlates well with recent unsteady flow results from the literature.

Influence of Hot Streak Temperature Ratio on Low Pressure Stage of a Vaneless Counter-Rotating Turbine

2007 ◽  
Author(s):  
Qingjun Zhao ◽  
Fei Tang ◽  
Huishe Wang ◽  
Jianyi Du ◽  
Xiaolu Zhao ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
High Pressure Turbine ◽  
Pressure Stage ◽  
Low Pressure Turbine ◽  
Hot Streak

In order to explore the influence of hot streak temperature ratio on low pressure stage of a Vaneless Counter-Rotating Turbine, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed. The predicted results show that hot streaks are not mixed out by the time they reach the exit of the high pressure turbine rotor. The separation of colder and hotter fluids is observed at the inlet of the low pressure turbine rotor. After making interactions with the inner-extending shock wave and outer-extending shock wave in the high pressure turbine rotor, the hotter fluid migrates towards the pressure surface of the low pressure turbine rotor, and the most of colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are predominated by the secondary flow in the low pressure turbine rotor. The effect of buoyancy on the hotter fluid is very weak in the low pressure turbine rotor. The results also indicate that the secondary flow intensifies in the low pressure turbine rotor when the hot streak temperature ratio is increased. The effects of the hot streak temperature ratio on the relative Mach number and the relative flow angle at the inlet of the low pressure turbine rotor are very remarkable. The isentropic efficiency of the Vaneless Counter-Rotating Turbine decreases as the hot streak temperature ratio is increased.

Time-Averaged and Time-Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High-Pressure Turbine: Part I—Analytical and Experimental Comparisons

2012 ◽  
Author(s):  
Brian R. Green ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
High Pressure ◽  
Flow Field ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Flow Path ◽  
Field Analysis ◽  
High Pressure Turbine ◽  
Purge Flow

The effect of rotor purge flow on the unsteady aerodynamics of a high-pressure turbine stage operating at design corrected conditions has been investigated both experimentally and computationally. The experimental configuration consisted of a single-stage high-pressure turbine with a modern film-cooling configuration on the vane airfoil as well as the inner and outer end-wall surfaces. Purge flow was introduced into the cavity located between the high-pressure vane and the high-pressure disk. The high-pressure blades and the downstream low-pressure turbine nozzle row were not cooled. All hardware featured an aerodynamic design typical of a commercial high-pressure ratio turbine, and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response, flush-mounted pressure transducers and miniature thermocouples to measure flow field parameters above and below the angel wing. Predictions of the time-dependent flow field in the turbine flow path were obtained using FINE/Turbo, a three-dimensional, Reynolds-Averaged Navier-Stokes CFD code that had the capability to perform both steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three blade-row computational model that incorporated the purge flow cavity between the high-pressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The time-accurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the time-averaged and time-accurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for flow field analysis that will be provided in Part II.

Aerodynamic Performance of an Unlocated High Pressure Turbine Rotor With Worn Tip Seal Fins

2017 ◽  
Author(s):  
Lucas Pawsey ◽  
David John Rajendran ◽  
Vassilios Pachidis
Keyword(s):  
High Pressure ◽  
Rotor Blade ◽  
Turbine Rotor ◽  
Aerodynamic Performance ◽  
Axial Displacement ◽  
High Pressure Turbine ◽  
Design Modification ◽  
Turbine Casing ◽  
Secondary Air ◽  
Shaft Failure

An unlocated shaft failure in the high pressure turbine spool of an engine may result in a complex orbiting motion along with rearward axial displacement of the high pressure turbine rotor sub-assembly. This is due to the action of resultant forces and limitations imposed by constraints such as the bearings and turbine casing. Such motion of the rotor following an unlocated shaft failure, results in the development of multiple contacts between the components of the rotor sub-assembly, the turbine casing, and the downstream stator casing. Typically, in the case of shrouded rotor blades, the tip region is in the form of a seal with radial protrusions called ‘fins’ between the rotor blade and the turbine casing. The contact between the rotor blade and the turbine casing will therefore result in excessive wear of the tip seal fins, resulting in changes in the geometry of the tip seal domain that affects the characteristics of the tip leakage vortex. The rotor sub-assembly with worn seals may also be axially displaced rearwards, and consequent to this displacement, changes in the geometry of the rotor blade may occur because of the contact between the rotor sub-assembly and the downstream stator casing. An integrated approach of structural analyses, secondary air system dynamics, and 3D CFD is adopted in the present study to quantify the effect of the tip seal damage and axial displacement on the aerodynamic performance of the turbine stage. The resultant geometry after wearing down of the fins in the tip seal, and rearward axial displacement of the rotor sub-assembly is obtained from LS-DYNA simulations. 3D RANS analyses are carried out to quantify the aerodynamic performance of the turbine with worn fins in the tip seal at three different axial displacement locations i.e. 0 mm, 10 mm and 15 mm. The turbine performance parameters are then compared with equivalent cases in which the fins in the tip seal are intact for the same turbine axial displacement locations. From this study it is noted that the wearing of tip seal fins results in reduced turbine torque, power output and efficiency, consequent to changes in the flow behaviour in the turbine passages. The reduction in turbine torque will result in the reduction of the terminal speed of the rotor during an unlocated shaft failure. Therefore, a design modification that can lead to rapid wearing of the fins in the tip seal after an unlocated shaft failure holds promise for the management of a potential over-speed event.

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