Aerodynamic Tip Desensitization of an Axial Turbine Rotor Using Tip Platform Extensions

2001 ◽  
Author(s):  
Debashis Dey ◽  
Cengiz Camci
Keyword(s):  
Total Pressure ◽  
Axial Flow ◽  
Suction Side ◽  
Tangential Direction ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Pressure Probe ◽  
Total Efficiency ◽  
Efficiency Gain ◽  
Pressure Side

Aerodynamic losses due to the formation of a leakage vortex near the tip section of rotor blades form a significant part of viscous losses in axial flow turbines. The leakage flow, mainly induced by the pressure differential between the pressure side and suction side of a rotor tip section, usually rolls into a streamwise vortical structure near the suction side part of the blade tip. The current study uses the concept of a tip platform extension that is a very short “winglet” obtained by slightly extending the tip platform in the tangential direction. The use of a pressure side tip extension can significantly affect the local aerodynamic field by weakening the leakage vortex structure. Phase averaged, time accurate total pressure measurements downstream of a single stage turbine facility are provided from a total pressure probe that has a time response of 150 kHz. Complete total pressure maps in all of the 29 rotor exit planes are measured accurately. Various pressure and suction side extension configurations are compared against a baseline case. The current investigation performed in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University shows that significant total to total efficiency gain is possible by the use of tip platform extensions.

Influence of Leading Edge Fillet and Nonaxisymmetric Contoured Endwall on Turbine NGV Exit Flow Structure and Interactions With the Rim Seal Flow

2013 ◽  
Author(s):  
Özhan H. Turgut ◽  
Cengiz Camcı
Keyword(s):  
Flow Structure ◽  
Total Pressure ◽  
Guide Vane ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Constant Thickness ◽  
Computational Evaluation ◽  
Nozzle Guide

Three different ways are employed in the present paper to reduce the secondary flow related total pressure loss. These are nonaxisymmetric endwall contouring, leading edge (LE) fillet, and the combination of these two approaches. Experimental investigation and computational simulations are applied for the performance assessments. The experiments are carried out in the Axial Flow Turbine Research Facility (AFTRF) having a diameter of 91.66cm. The NGV exit flow structure was examined under the influence of a 29 bladed high pressure turbine rotor assembly operating at 1300 rpm. For the experimental measurement comparison, a reference Flat Insert endwall is installed in the nozzle guide vane (NGV) passage. It has a constant thickness with a cylindrical surface and is manufactured by a stereolithography (SLA) method. Four different LE fillets are designed, and they are attached to both cylindrical Flat Insert and the contoured endwall. Total pressure measurements are taken at rotor inlet plane with Kiel probe. The probe traversing is completed with one vane pitch and from 8% to 38% span. For one of the designs, area averaged loss is reduced by 15.06%. The simulation estimated this reduction as 7.11%. Computational evaluation is performed with the rotating domain and the rim seal flow between the NGV and the rotor blades. The most effective design reduced the mass averaged loss by 1.28% over the whole passage at the NGV exit.

Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage

2003 ◽  
Author(s):  
Cengiz Camci ◽  
Debashis Dey ◽  
Levent Kavurmacioglu
Keyword(s):  
Total Pressure ◽  
Axial Flow ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Edge Zone ◽  
Tip Leakage ◽  
Partial Length

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage

2005 ◽  
Vol 127 (1) ◽  
pp. 14-24 ◽  
Author(s):  
Cengiz Camci ◽  
Debashis Dey ◽  
Levent Kavurmacioglu
Keyword(s):  
Total Pressure ◽  
Axial Flow ◽  
Suction Side ◽  
Leakage Flow ◽  
Pressure Side ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Edge Zone ◽  
Tip Leakage ◽  
Partial Length

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

Part-Span Application of Sweep and Lean at Turbine Blade Tips: A Low Speed Experimental Cascade Study

2010 ◽  
Author(s):  
Bhaskar Roy ◽  
Anoop Prajapati
Keyword(s):  
Performance Improvement ◽  
Turbine Blade ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Pressure Surface ◽  
Wall Boundary Layer ◽  
Performance Reduction ◽  
Application Potential ◽  
End Wall

This study is aimed at exploring the possibility of aerodynamic performance improvement by providing part-span forward sweep and lean near the tip regions of axial flow turbine rotor blades. Such aerodynamic benefits may have application potential in the uncooled LPT blades. The curved forward sweep and curved lean have been provided to 25% of the blade span near the tip in cascade, Three sets of cascades of the same turbine airfoil have been studied — (i) straight blades, (ii) part span swept blades and (iii) part span leaned blades. The cascade results show that swept blade gives a recovery of 20–25% loss in blade performance near the tip region at 0° and 10° incidences. The swept and leaned blades suppress the Cp perturbations (as seen in straight blades) at 0° and at 10° incidences, on the suction surfaces of turbine blade cascades. Comparatively the leaned blades show blade unloading, largely on the pressure surface, which leads to some performance reduction. The wake loss study shows reduction in wake losses for swept turbine blade at near tip region. The end-wall boundary layer measurements across the open tips demonstrate some aerodynamic improvement, near the tip regions, for parts-span swept and leaned blades.

Aerodynamic optimisation of a winglet-cavity tip in a high-pressure axial turbine cascade

2016 ◽  
Vol 232 (4) ◽  
pp. 649-663 ◽  
Author(s):  
Zhihua Zhou ◽  
Shaowen Chen ◽  
Songtao Wang
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Suction Side ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Pressure Side ◽  
Tip Clearance Flow ◽  
Clearance Flow

Tip clearance flow between rotating blades and the stationary casing in high-pressure turbines is very complex and is one of the most important factors influencing turbine performance. The rotor with a winglet-cavity tip is often used as an effective method to improve the loss resulting from the tip clearance flow. In this study, an aerodynamic geometric optimisation of a winglet-cavity tip was carried out in a linear unshrouded high-pressure axial turbine cascade. For the purpose of shaping the efficient winglet geometry of the rotor tip, a novel parameterisation method has been introduced in the optimisation procedure based on the computational fluid dynamics simulation and analysis. The reliability of a commercial computational fluid dynamics code with different turbulence models was first validated by contrasting with the experimental results, and the numerical total pressure loss and flow angle using the Baseline k-omega Model (BSL κ-ω model) shows a better agreement with the test data. Geometric parameterisation of blade tips along the pressure side and suction side was adopted to optimise the tip clearance flow, and an optimal winglet-cavity tip was proven to achieve lower tip leakage mass flow rate and total pressure loss than the flat tip and cavity tip. Compared to the numerical results of flat tip and cavity tip, the optimised winglet-cavity design, with the winglet along the pressure side and suction side, had lower tip leakage mass flow rate and total pressure loss. It offered a 35.7% reduction in the change ratio [Formula: see text]. In addition, the optimised winglet along pressure side and suction side, respectively, by using the parameterisation method was studied for investigating the individual effect of the pressure-side winglet and suction-side winglet on the tip clearance flow. It was found that the suction-side extension of the optimal winglet resulted in a greater reduction of aerodynamic loss and leakage mass flow than the pressure-side extension of the optimal winglet. Moreover, with the analysis based on the tip flow pattern, the numerical results show that the pressure-side winglet reduced the contraction coefficient, and the suction-side winglet reduced the aerodynamic loss effectively by decreasing the driving pressure difference near the blade tips, the leakage flow velocity, and the interaction between the leakage flow and the main flow. Overall, a better aerodynamic performance can be obtained by adopting the pressure-side and suction-side winglet-cavity simultaneously.

Measurements of Secondary Flows and Turbulence in a Turbine Cascade Passage

1987 ◽  
Author(s):  
Pietro Zunino ◽  
Marina Ubaldi ◽  
Antonio Satta
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Turbulent Shear ◽  
Pressure Probe ◽  
Shear Stresses ◽  
Passage Vortex ◽  
High Level

The results of an experimental investigation on secondary flows in a linear cascade of turbine rotor blades are presented. To gain information on the turbulence related to the secondary flow development in turbine cascades, measurements have been carried out at eight normal sections in the passage and at a plane downstream of the trailing edge, using a constant temperature hot wire anemometer and a total pressure probe. A high level of turbulent kinetic energy and turbulent shear stresses has been found to be associated with the passage vortex. This result confirms that secondary loss generation in cascades is related to the production of turbulent kinetic energy in the vortex flow and to its viscous dissipation.

A Comparative Analysis of Pressure Side Extensions for Tip Leakage Control in Axial Turbines

2008 ◽  
Author(s):  
Akamol Shavalikul ◽  
Cengiz Camci
Keyword(s):  
Axial Flow ◽  
Turbine Rotor ◽  
Pressure Side ◽  
Flow Measurements ◽  
Inlet Flow ◽  
Aerodynamic Loss ◽  
Tip Leakage ◽  
Leakage Control ◽  
Penn State ◽  
Axial Turbines

Pressure side extensions are effective tip leakage control devices in axial flow turbines. RANS based viscous flow simulations are used to compare a number of potential aerodynamic de-sensitization devices for blade tips. The present study benefits from the past aerodynamic experiments performed in the rotating turbine rig at Penn State by Dey and Camci [14]. After a brief discussion of the computational details, a grid independency study is presented. The current study shows that a significant tip leakage mass flow rate and aerodynamic loss reduction is possible by using proper tip platform extensions located near the pressure side corner of the blade tip. A set of computations with realistic turbine rotor inlet flow conditions are performed in a linear cascade arrangement in the relative frame of reference. The boundary conditions for the computations are obtained from inlet flow measurements performed in Penn State Axial Flow Turbine Research Facility AFTRF.

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

2012 ◽  
Vol 134 (6) ◽  
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 ◽  
Rotor Blades ◽  
Operating Point ◽  
Pressure Side ◽  
Low Pressure Turbine ◽  
Purge Flow

This paper presents an experimental and computational study of non-axisymmetric rotor endwall profiling in a low pressure turbine. Endwall 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 endwalls on both hub and shroud is considered. The rotor tip and hub endwalls have been designed using an automatic numerical optimization that is implemented in an in-house MTU code. The endwall shape is modified up to the platform leading edge. Several levels of purge flow are considered in order to analyze the combined effects of endwall 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 endwalls show the beneficial effects of improved measured efficiency at this operating point, together with a reduced sensitivity to purge flow.

Computation and Measurement of the Flow in Axial Flow Fans With Skewed Blades

1999 ◽  
Vol 121 (1) ◽  
pp. 59-66 ◽  
Author(s):  
M. G. Beiler ◽  
T. H. Carolus
Keyword(s):  
Total Pressure ◽  
Design Method ◽  
Power Level ◽  
Three Dimensional ◽  
Axial Flow ◽  
Pressure Rise ◽  
Fast Response ◽  
Test Facility ◽  
Navier Stokes ◽  
Pressure Probe

A numerical analysis of the flow in axial flow fans with skewed blades has been conducted to study the three-dimensional flow phenomena pertaining to this type of blade shape. The particular fans have a low pressure rise and are designed without stator. Initial studies focused on blades skewed in the circumferential direction, followed by investigations of blades swept in the direction of the blade chord. A Navier–Stokes code was used to investigate the flow. The simulation results of several fans were validated experimentally. The three-dimensional velocity field was measured in the fixed frame of reference with a triple sensor hot-film probe. Total pressure distribution measurements were performed with a fast response total pressure probe. The results were analyzed, leading to a design method for fans with swept blades. Forward swept fans designed accordingly exhibited good aerodynamic performance. The sound power level, measured on an acoustic fan test facility, improved.

Performance of the Wells Turbine With Variable Pitch Rotor Blades

1991 ◽  
Vol 113 (3) ◽  
pp. 141-146 ◽  
Author(s):  
L. M. C. Gato ◽  
L. R. C. Ec¸a ◽  
A. F. de O. Falca˜o
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Axial Flow ◽  
Ocean Waves ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Computational Method ◽  
Wells Turbine ◽  
Predicted Values ◽  
Energy Absorbing

The Wells turbine is an axial-flow air-turbine designed to extract energy from the ocean waves. The turbine is self-rectifying, i.e., produces an unidirectional time-averaged torque from a reciprocating flow. The paper describes an experimental investigation on the aerodynamic performance of a modified version of the Wells turbine, whose rotor blades can be set at varying angle (as in a Kaplan turbine) while the turbine is in motion. The purpose of the work is to investigate whether, and to what extent, the modification to the turbine can enable it to achieve phase control—a method of tuning the energy-absorbing device to the incident waves—and avoid aerodynamic stall on the turbine rotor blades at peaks of air flow rate under conditions of real irregular ocean waves. Experimental results obtained with a model turbine are compared with predicted values from a quasi-three-dimensional computational method of flow analysis.

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