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.

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.

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.

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.

Unsteady Flow Physics and Performance of a One-and-1/2-Stage Unshrouded High Work Turbine

2006 ◽  
Author(s):  
T. Behr ◽  
A. I. Kalfas ◽  
R. A. Abhari
Keyword(s):  
Secondary Flow ◽  
Leading Edge ◽  
Fast Response ◽  
Turbine Rotor ◽  
Test Case ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Flow Mechanisms ◽  
The One ◽  
High Work

This paper presents an experimental study of the flow mechanisms of tip leakage across a blade of an unshrouded turbine rotor. It shows the design of a new one-and-1/2-stage, unshrouded turbine configuration, which has been developed within the Turbomachinery Laboratory of ETH Zurich. This test case is a model of a high work (Δh/u2 = 2.36) axial turbine. The experimental investigation comprises data from unsteady and steady probe measurements, which has been acquired around all the bladerows of the one-and-1/2-stage, unshrouded turbine. A newly developed 2-sensor Fast Response Aerodynamic Probe (FRAP) technique has been used in the current measurement campaign. The paper contains a detailed analysis of the unsteady interaction between rotor and stator blade rows, with particular attention paid on the flow in the blade tip region. It has been found that the pressure field of the second stator row has a influence on the development of the tip leakage vortex downstream of the rotor. The vortex is modulated by the stator profiles and shows variation in size and relative position to the rotor trailing edge when it stretches around the stator leading edge. Thereby a deflection of the tip leakage vortex has been observed, which expresses in a varying circumferential distance between two neighboring vortices of ±20% of a rotor pitch. Furthermore, a significant influence of quasi-stationary secondary flow features of the upstream stator row on the secondary flow of the rotor has been detected. The geometry data of the one-and-1/2-stage turbine will be available to the public domain for validation and improvement of numerical tools.

Unsteady Flow Physics and Performance of a One-and-1∕2-Stage Unshrouded High Work Turbine

2006 ◽  
Vol 129 (2) ◽  
pp. 348-359 ◽  
Author(s):  
T. Behr ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Secondary Flow ◽  
Leading Edge ◽  
Fast Response ◽  
Turbine Rotor ◽  
Test Case ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Flow Mechanisms ◽  
The One ◽  
High Work

This paper presents an experimental study of the flow mechanisms of tip leakage across a blade of an unshrouded turbine rotor. It shows the design of a new one-and-1∕2-stage, unshrouded turbine configuration, which has been developed within the Turbomachinery Laboratory of ETH Zurich. This test case is a model of a high work (Δh∕u2=2.36) axial turbine. The experimental investigation comprises data from unsteady and steady probe measurements, which has been acquired around all the bladerows of the one-and-1∕2-stage, unshrouded turbine. A newly developed 2-sensor Fast Response Aerodynamic Probe (FRAP) technique has been used in the current measurement campaign. The paper contains a detailed analysis of the unsteady interaction between rotor and stator blade rows, with particular attention paid on the flow in the blade tip region. It has been found that the interaction of the rotor and the downstream stator has an influence on the development of the tip leakage vortex of the rotor. The vortex is modulated by the stator profiles and shows variation in size and relative position to the rotor trailing edge when it stretches around the stator leading edge. Thereby a deflection of the tip leakage vortex has been observed, which expresses in a varying circumferential distance between two neighboring vortices of ±20% of a rotor pitch. Furthermore, a significant influence of quasi-stationary secondary flow features of the upstream stator row on the secondary flow of the rotor has been detected. The geometry and flow field data of the one-and-1∕2-stage turbine will be available to the turbomachinery community for validation and improvement of numerical tools.

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

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Zhao Qingjun ◽  
Tang Fei ◽  
Wang Huishe ◽  
Du Jianyi ◽  
Zhao Xiaolu ◽  
...  
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
High Pressure Turbine ◽  
Flow Angle ◽  
Pressure Stage ◽  
Low Pressure Turbine ◽  
Hot Streak

In order to explore the influence of hot streak temperature ratio on the 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 and outer-extending shock waves in the high pressure turbine rotor, the hotter fluid migrates toward the pressure surface of the low pressure turbine rotor, and most of the colder fluid migrates to the suction surface of the low pressure turbine rotor. The migrating characteristics of the hot streaks are dominated by the secondary flow 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 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.

PIV Maps of Tip Leakage and Secondary Flow Fields on a Low Speed Turbine Blade Cascade With Moving Endwall

2005 ◽  
Author(s):  
P. Palafox ◽  
M. L. G. Oldfield ◽  
J. E. LaGraff ◽  
T. V. Jones
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Field Measurements ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Low Speed ◽  
Tip Leakage

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110 degrees and blade chord of 1.0 m. Data was obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0 × 105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle Image Velocimetry (PIV) was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip endwall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the under-tip flow near the endwall due to the moving wall is observed and the effect on the tip leakage vortex examined.

Effects of Unsteady Wakes on Flow Through High Pressure Turbine Passages With and Without Tip Gaps

2014 ◽  
Author(s):  
Ralph J. Volino ◽  
Christopher D. Galvin ◽  
Cody J. Brownell
Keyword(s):  
High Pressure ◽  
Pressure Loss ◽  
Total Pressure ◽  
Flow Direction ◽  
Velocity Fields ◽  
Total Pressure Loss ◽  
High Pressure Turbine ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Wake Passing

Experiments were conducted in a linear high pressure turbine cascade with wakes generated by moving upstream rods. The cascade included an adjustable top endwall that could be raised and lowered above the airfoils to change the tip gap. Conditions were considered with no tip gap, and gaps of 1.5% and 3.8% of axial chord. For each of these, cases were documented both with and without upstream wakes. The pressure distributions on the airfoils were acquired at the midspan and near the tip for each case. The total pressure loss was measured in the endwall region. Velocity fields were acquired in two planes normal to the flow direction using particle image velocimetry (PIV). For the case with no tip gap, the passage vortex and other vortices were clearly visible in the velocity fields. For the cases with a tip gap, the tip leakage vortex was the dominant flow feature, and it became stronger as the gap size increased. The other vortices were still present, but were moved by the tip leakage vortex. For the cases with unsteady wakes, the PIV data were ensemble-averaged based on phase within the wake passing cycle, to show the motion and change in strength of the vortices in response to the wake passing. The regions of high total pressure loss can be explained in terms of the secondary velocity field.

Experimental and Computational Study of Novel Tip Leakage Mitigation Methods for High Pressure Turbine Blades

2015 ◽  
Author(s):  
Mounir B. Ibrahim ◽  
Ralph J. Volino
Keyword(s):  
High Pressure ◽  
Computational Study ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
High Pressure Turbine ◽  
Ansys Fluent ◽  
Tip Leakage ◽  
Blowing Ratio ◽  
Numerical Solver ◽  
Mitigation Methods

This paper presents computational and experimental study of a possible approach to reduce tip leakage losses. The study was conducted on the EEE (Energy Efficient Engine) HPT (High Pressure Turbine) rotor tip geometry. The CFD was done utilizing the commercial numerical solver ANSYS FLUENT. The experimental work was conducted in a low speed wind tunnel with linear cascade at the USNA (for Re = 30,000) and the NASA Transonic Turbine Blade Cascade facility at the NASA John H. Glenn Research Center for Re of 85,000 to 683,000 at two isentropic exit Mach numbers of 0.74 and 0.34 were reported. The overall scope of this study is to investigate how the tip leakage and overall blade losses are affected by injection from the tip surface at the camber line, and the jet blowing ratio. The results identify areas where future investigation can be explored in order to achieve higher performance of the high pressure turbines.

Unsteady Aerodynamics of a Flat Tip and a Winglet Tip in a High-Pressure Turbine

2016 ◽  
Author(s):  
Kai Zhou ◽  
Chao Zhou
Keyword(s):  
High Pressure ◽  
Unsteady Aerodynamics ◽  
Suction Side ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
High Pressure Turbine ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Passage Vortex

In an unshrouded high-pressure turbine, tip leakage flow results in a loss of efficiency. In this paper, the aerodynamic performance of the tip leakage flow is investigated in a turbine stage by numerical methods. A flat tip and a closed squealer tip combined with a suction side winglet are used for the rotor tips, and the two turbines are named as ‘Flat Configuration’ and ‘Winglet Configuration’. The ability of the CFD methods in predicting the unsteady flow and the tip leakage flow is validated. The steady calculations using a mixing plane between the stator and the rotor are presented first. Then, the unsteady flows of the turbine stage with a flat rotor tip and a winglet rotor tip are simulated by solving Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. Compared with the ‘Flat Configuration’, the ‘Winglet Configuration’ reduces the size of the passage vortex and the tip leakage vortex. A surprising observation is that although the ‘Winglet Configuration’ reduces the size of the tip leakage vortex, its maximum swirl strength of the tip leakage vortex is about 40% higher than that for the ‘Flat Configuration’. The steady calculation shows that the entropy generation for the turbine stage is 12.1% lower with the ‘Winglet Configuration’ than that with the ‘Flat Configuration’. The mixed-out entropy predicted in the unsteady calculation is higher than that of the steady calculation for both tips. The stator casing passage vortex has a periodic effect on the vortex near the tip gap of the rotor. The unsteady interaction of the vortices seems to be beneficial in terms of the loss. As a result, the ‘Winglet Configuration’ produces 9.4% less entropy than the ‘Flat Configuration’, which is lower than that in the case of the steady calculation.

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