Experimental Investigation of a Single Stage Axial Flow Compressor With Controlled Diffusion Airfoils

1996 ◽  
Author(s):  
S. Pieper ◽  
J. Schulte ◽  
A. Hoynacki ◽  
H. E. Gallus
Keyword(s):  
Pressure Field ◽  
Flow Behavior ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Time Dependent ◽  
Suction Surface ◽  
Average Technique ◽  
Unsteady Pressure ◽  
Controlled Diffusion

In order to verify an inverse design concept for modern compressor bladings, a subsonic compressor front stage with IGV was investigated. One objective of the design was to survey the flow field in detail, with emphasis on 3D viscous and unsteady aspects of the flow. Therefore, the compressor was equipped with various steady and unsteady measurement techniques. Additionally, a compressor design was chosen that allows an extension up to three stages with regard to the investigation of multistage axial compressor flow behavior. Test results of the steady measurements are discussed for IGV, rotor, and stator flow at design conditions as well as the overall stage performance. The measurements of the steady flow behavior confirm the expected design performance and show the high potential of the controlled diffusion airfoil concept. Only at the side walls near hub and casing there are some differences between design and measurement due to the complex three dimensional flow. For the study of unsteady effects, detailed measurements using hot-wire probes, glue-on hot-films, and semiconductor pressure transducers were performed. All measurements are evaluated using the ensemble-average technique. The results show how the boundary layers of the inlet guide vanes and stator blades develop in a flow that is periodically disturbed by the rotor. Time-dependent pressure distributions at midspan of both stators are described. In addition, the unsteady pressure field at the casing above the rotor was investigated. The minimum wall pressure is located away from the blade suction surface. The effects of tip clearance flow on the performance are presented. The radial extent covers 15% span from the tip. At rotor exit, the unsteady pressure field and the time-dependent three-dimensional velocity vectors illustrate the salient features of the viscous flow associated with the rotor.

An Experimental Investigation Into Turbine Flutter Characteristic at Different Tip-Clearances

2006 ◽  
Author(s):  
X. Q. Huang ◽  
L. He ◽  
D. L. Bell
Keyword(s):  
Turbine Blades ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Pressure Measurements ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Local Pressure ◽  
Unsteady Pressure ◽  
Pressure Suction ◽  
Unsteady Pressure Measurements

This paper documents an investigation into unsteady flow in a three-dimensional oscillating turbine cascade with emphasis on the influence of tip clearance. Systematic experimental measurements were performed on a low-speed turbine cascade rig. The cascade consists of seven prismatic turbine blades, with the middle blade being driven to oscillate in a three-dimensional bending/flapping mode. Blades were instrumented with pressure tappings at six span-wise sections to facilitate three dimensional steady and unsteady pressure measurements on the blade surface. The steady pressure measurements are complemented by CFD simulations. Both are in a good agreement and indicate a marked local pressure suction peak at 70–90% chord on the suction surface resulting from the tip-clearance vortex. The measured unsteady pressure shows that this tip-clearance induced suction peak has a significant destabilising influence on the aerodynamic damping at a large tip-clearance (5% chord). Whilst at a small tip clearance (1.25–2.5% chord), the tip-clearance actually has a stabilising effect. The behaviour is in line with a quasi-steady analysis.

scholarly journals Computation of Flow Past a Turbine Blade With and Without Tip Clearance

1991 ◽  
Author(s):  
W. R. Briley ◽  
D. V. Roscoe ◽  
H. J. Gibeling ◽  
R. C. Buggeln ◽  
J. S. Sabnis ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Main Stream ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Gas Generator

Three-dimensional solutions of the ensemble-averaged Navier-Stokes equations have been computed for a high-turning turbine rotor passage, both with and without tip clearance effects. The geometry is Pratt & Whitney’s preliminary design for the Generic Gas Generator Turbine (GGGT), having an axial chord of 0.5 inch and turning angle of about 160 degrees. The solutions match the design Reynolds number of 3x 106/inch and design inflow/outflow distributions of flow quantities. The grid contains 627,000 points, including 20 radial points in the clearance gap of 0.015 inch, and has a minimum spacing of 10−4 inch adjacent to all surfaces. The solutions account for relative motion of the blade and shroud surfaces and include a backstep on the shroud. Computed results are presented which show the general flow behavior, especially near the tip clearance and backstep regions. The results are generally consistent with experimental observations for other geometries having thinner blades and smaller turning angles. The leakage flow includes some fluid originally in the freestream at 91 percent span. Downstream, the leakage flow behaves as a wall jet directed at 100 degrees to the main stream, with total pressure and temperature higher than the freestream. Radial distributions of circumferentially-averaged flow quantities are compared for solutions with and without tip leakage flow. Two-dimensional solutions are also presented for the mid-span blade geometry for design and off-design inflow angles.

Hydrodynamic Design of Pump Diffuser Using Inverse Design Method and CFD

2002 ◽  
Vol 124 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Akira Goto ◽  
Mehrdad Zangeneh
Keyword(s):  
Design Method ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Inverse Design ◽  
Navier Stokes ◽  
Outer Diameter ◽  
Large Area ◽  
Suction Surface ◽  
Pump Stage ◽  
Inverse Design Method

A new approach to optimizing a pump diffuser is presented, based on a three-dimensional inverse design method and a Computational Fluid Dynamics (CFD) technique. The blade shape of the diffuser was designed for a specified distribution of circulation and a given meridional geometry at a low specific speed of 0.109 (non-dimensional) or 280 (m3/min, m, rpm). To optimize the three-dimensional pressure fields and the secondary flow behavior inside the flow passage, the diffuser blade was more fore-loaded at the hub side as compared with the casing side. Numerical calculations, using a stage version of Dawes three-dimensional Navier-Stokes code, showed that such a loading distribution can suppress flow separation at the corner region between the hub and the blade suction surface, which was commonly observed with conventional designs having a compact bowl size (small outer diameter). The improvements in stage efficiency were confirmed experimentally over the corresponding conventional pump stage. The application of multi-color oil-film flow visualization confirmed that the large area of the corner separation was completely eliminated in the inverse design diffuser.

scholarly journals Effects of Stator Pressure Field on Upstream Rotor Performance

1999 ◽  
Author(s):  
M. B. Graf ◽  
E. M. Greitzer ◽  
F. E. Marble ◽  
O. P. Sharma
Keyword(s):  
Steady Flow ◽  
Pressure Field ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Flow Models ◽  
High Pressure Compressor ◽  
Rotor Stator Interaction ◽  
Rotor Loss

Effects of stator pressure field on upstream rotor performance in a high pressure compressor stage have been assessed using three-dimensional steady and time-accurate Reynolds-averaged Navier-Stokes computations. Emphasis was placed on: (1) determining the dominant features of the flow arising from interaction of the rotor with the stator pressure field, and (2) quantifying the overall effects on time averaged loss, blockage, and pressure rise. The time averaged results showed a 20 to 40% increase in overall rotor loss and a 10 to 50% decrease in tip clearance loss compared to an isolated rotor. The differences were dependent on the operating point and increased as the stage pressure rise, and amplitude of the unsteady back pressure variations, was increased. Motions of the tip leakage vortex on the order of the blade pitch were observed at the rotor exit in all the unsteady flow simulations; these were associated with enhanced mixing in the region. The period of the motion scaled with rotor flow-through time rather than stator passing. Three steady flow approximations for the rotor-stator interaction were assessed with reference to the unsteady computations: an axisymmetric representation of the stator pressure field, an inter-blade row averaging plane method, and a technique incorporating deterministic stresses and bodyforces associated with stator flow field. Differences between steady and unsteady predictions of overall rotor loss, tip region loss, and endwall blockage ranged from 5 to 50% of the time average, but the steady flow models gave overall rotor pressure rise and flow capacity within 5% of the time averaged values.

Vortex Tracking of Purge-Mainstream Interactions in a Rotating Turbine Stage

2021 ◽  
Author(s):  
Alex W. Mesny ◽  
Mark A. Glozier ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
Yan Sheng Li ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Suction Surface ◽  
Vortex Filaments ◽  
Passage Vortex ◽  
Purge Flow

Abstract The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egress-mainstream interaction using optical measurement techniques. Volumetric Velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localised vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary-flow vortices was determined by using a circulation criterion on rotated planes aligned to the vortex filaments. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow the two vortices merged, forming the passage vortex. With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the passage vortex. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.

The unsteady pressure field of a ducted impeller

1979 ◽  
Vol 90 (2) ◽  
pp. 209-226 ◽  
Author(s):  
Dac Q. Dang ◽  
D. H. Norrie
Keyword(s):  
Pressure Field ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Governing Equations ◽  
General Constraint ◽  
Unsteady Pressure ◽  
Ducted Propeller ◽  
Harmonic Components ◽  
Phase Angles ◽  
Good Agreement

Analyses based on a three-dimensional vortex-filament model are presented for the unsteady pressure field generated by a ducted propeller. An oscillating part is identified in the kernels and absolute terms of the governing equations for the harmonic components, allowing two methods to be developed for the solution of the higher harmonics. The first method is exact and is applicable to ducted propellers with practical configurations (small chord-to-diameter ratio) while the second is approximate but more suitable for ducted systems with large chord-to-diameter ratios. The second method was applied to a configuration for which experimental data were available and good agreement was obtained for pressure harmonic amplitudes downstream of the propeller and for phase angles upstream of the propeller.Special consideration was given to the Kutta-Joukowski condition at the duct trailing edge and a general constraint developed for the doubly coupled governing integral equations.

Three-Dimensional Unsteady Flow for an Oscillating Turbine Blade and the Influence of Tip Leakage

1998 ◽  
Vol 122 (1) ◽  
pp. 93-101 ◽  
Author(s):  
D. L. Bell ◽  
L. He
Keyword(s):  
Unsteady Flow ◽  
Turbine Blade ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Tip Clearance ◽  
Computational Results ◽  
Blade Loading ◽  
Tip Leakage ◽  
Unsteady Pressure ◽  
Reduced Frequency

The results of two investigations, concerning the aerodynamic response of a turbine blade oscillating in a three-dimensional bending mode, are presented in this paper. The first is an experimental and computational study, designed to produce detailed three-dimensional test cases for aeroelastic applications and examine the ability of a three-dimensional time-marching Euler method to predict the relevant unsteady aerodynamics. Extensive blade surface unsteady pressure measurements were obtained over a range of reduced frequency from a test facility with clearly defined boundary conditions (Bell and He, 1997, ASME Paper No. 97-GT-105). The test data indicate a significant three-dimensional effect, whereby the amplitude of the unsteady pressure response at different spanwise locations is largely insensitive to the local bending amplitude. The computational results, which are the first to be supported by detailed three-dimensional test data, demonstrate the ability of the inviscid method to capture the three-dimensional behavior exhibited by the experimental measurements and a good level of quantitative agreement is achieved throughout the range of reduced frequency. Additional computational solutions, obtained through application of the strip methodology, reveal inadequacies in the conventional quasi-three-dimensional approach to the prediction of oscillating blade flows. The issue of linearity is also considered, and both experimental and computational results indicate a linear behavior of the unsteady aerodynamics. The second, an experimental investigation, addresses the influence of tip leakage upon the unsteady aerodynamic response of an oscillating turbine blade. Results are provided for three settings of tip clearance. The steady flow measurements show marked increases in the size and strength of the tip leakage vortex for the larger settings of tip clearance and deviations are present in the blade loading toward the tip section. The changes in tip clearance also caused distinct trends in the amplitude of the unsteady pressure at 90 percent span, which are observed to correspond with localized regions where the tip leakage flow had a discernible impact on the steady flow blade loading characteristic. The existence of these trends in the unsteady pressure response warrants further investigation into the influence of tip leakage on the local unsteady flow and aerodynamic damping. [S0889-504X(00)01101-6]

Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part II—The Tip Leakage Vortex

1993 ◽  
Vol 115 (3) ◽  
pp. 444-450 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Vortex Center ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage

An analysis of the experimental data of a linear compressor cascade with tip clearance is presented with special attention to the development of the tip leakage vortex. A method for determining the tip vortex core size, center position, and vorticity or circulation from the measured data is proposed, based on the assumption of a circular tip vortex core. It is observed that the axial velocity profile passing through the tip vortex center is wavelike. The vorticity of the tip vortex increases rapidly near the leading edge and reaches its highest values at a short distance downstream, from which it gradually decreases. In the whole evolution, its size is growing and its center is moving away from both the suction surface and the endwall, approximately in a linear way.

Effect of tip clearance dimension on unsteadiness in a low-reaction aspirated transonic compressor rotor

2020 ◽  
Vol 234 (6) ◽  
pp. 1181-1194 ◽  
Author(s):  
Wei Zhu ◽  
Le Cai ◽  
Songtao Wang ◽  
Zhongqi Wang
Keyword(s):  
Unsteady Flow ◽  
Vortex Breakdown ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Axial Acceleration ◽  
The Difference

A three-dimensional, multi-passage unsteady numerical study was conducted to enhance the understanding of unsteady flow phenomena in the tip region of highly loaded compressors. The first-stage rotor of a three-stage transonic low-reaction compressor was chosen as the computational model. Three different tip clearance sizes were calculated to demonstrate the effect of the tip clearance dimension on the unsteadiness in the rotor tip region. It was found that the unsteadiness existed at the vicinity of the stall point when the tip clearance size was larger than the design value. The unsteadiness in the tip region appeared as a “multi-passage structure” in the nine-passage unsteady simulation and it propagated along the circumferential direction. Tip leakage vortex breakdown was the source of unsteady flow behavior. Besides, special attention was paid to the difference between the conventional transonic rotor and the low-reaction rotor. The scale of the flow separation downstream of the shock wave was controllable for the low-reaction rotor even at near-stall conditions. The boundary layer would reattach to the blade surface due to local axial acceleration. Finally, attempts were made to study the stall mechanism of the low-reaction rotor.

Interaction of Tip Clearance Flow and Three-Dimensional Separations in Axial Compressors

2006 ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Nicholas A. Cumpsty ◽  
Tom P. Hynes
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Tip Clearance Flow ◽  
Separation Line ◽  
Numerical Predictions ◽  
Clearance Flow

This paper considers the interaction of tip clearance flow with three-dimensional (3D) separations in the corner region of a compressor cascade. Three-dimensional numerical computations were carried out using ten levels of tip clearance, ranging from zero to 2.18% of blade chord. The 3D separations on the blade suction surface were largely removed by the clearance flow for clearance about 0.58% of chord. For this cascade, experimental results at zero and 1.7% chord tip clearance were used to assess the validity of the numerical predictions. The removal mechanism was associated with the suppression of the leading edge horseshoe vortex and the interaction of tip clearance flow with the endwall boundary layer, which develops into a secondary flow as it is drifted towards the blade suction surface. Such interaction leads to the formation of a new 3D separation line on the endwall. The separation line forms the base of a separated stream surface which rolls up into the clearance vortex.

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