Quasi-Static Moment Measurements for Airfoils in an Annular Cascade

1972 ◽  
Vol 9 (4) ◽  
pp. 298-305
Author(s):  
F. SlSTO ◽  
R. H. Nl
Keyword(s):  
Static Moment ◽  
Annular Cascade

Interaction of acoustic-vorticity waves with an annular cascade in a swirling flow

1997 ◽  
Author(s):  
Vladimir Golubev ◽  
Hafiz Atassi ◽  
Vladimir Golubev ◽  
Hafiz Atassi
Keyword(s):  
Swirling Flow ◽  
Annular Cascade

Unsteady Lifting Surface Theory for a Rotating Cascade of Swept Blades

1989 ◽  
Author(s):  
Hidekazu Kodama ◽  
Masanobu Namba
Keyword(s):  
Three Dimensional ◽  
Acoustic Power ◽  
Aerodynamic Characteristics ◽  
Blade Loading ◽  
Surface Theory ◽  
Numerical Examples ◽  
Lifting Surface ◽  
Blade Flutter ◽  
Annular Cascade ◽  
Remarkable Reduction

A lifting surface theory is developed to predict the unsteady three-dimensional aerodynamic characteristics for a rotating subsonic annular cascade of swept blades. A discrete element method is used to solve the integral equation for the unsteady blade loading. Numerical examples are presented to demonstrate effects of the sweep on the blade flutter and on the acoustic field generated by interaction of rotating blades with a convected sinusoidal gust. It is found that increasing the sweep results in decrease of the aerodynamic work on vibrating blades and also remarkable reduction of the modal acoustic power of lower radial orders for both forward and backward sweeps.

Upstream Film Cooling on the Contoured Endwall of a Transonic Turbine Vane in an Annular Cascade

2020 ◽  
Author(s):  
Daniel A. Salinas ◽  
Izhar Ullah ◽  
Lesley M. Wright ◽  
Je-Chin Han ◽  
John W. McClintic ◽  
...  
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Lateral Spread ◽  
Pressure Sensitive Paint ◽  
Blow Down ◽  
Film Cooling Effectiveness ◽  
Pressure Sensitive ◽  
Mainstream Flow ◽  
Additional Protection ◽  
Annular Cascade

Abstract The effects of mainstream flow velocity, density ratio (DR), and coolant-to-mainstream mass flow ratio (MFR) were investigated on a vane endwall in a transonic, annular cascade. A blow down facility consisting of five vanes was used. The film cooling effectiveness was measured using binary pressure sensitive paint (BPSP). The mainstream flow was set using isentropic exit Mach numbers of 0.7 and 0.9. The coolant-to-mainstream density ratio varied from 1.0 to 2.0. The coolant to mainstream MFR varied from 0.75% to 1.25%. The endwall was cooled by eighteen discrete holes located upstream of the vane passage to provide cooling to the upstream half of the endwall. Due to the curvature of the vane endwall, the upstream holes provided uniform coverage entering the endwall passage. The coverage was effective leading to the throat of the passage, where the downstream holes could provide additional protection. Increasing the coolant flowrate increased the effectiveness provided by the film cooling holes. Increasing the density of the coolant increases the effectiveness on the endwall while enhancing the lateral spread of the coolant. Finally, increasing the velocity of the mainstream while holding the MFR constant also yields increased protection on the endwall. Over the range of flow conditions considered in this study, the binary pressure sensitive paint proved to be a valuable tool for obtaining detailed pressure and film effectiveness distributions.

Effect of an Axially Tilted Variable Stator Vane Platform on Penny Cavity and Main Flow

2021 ◽  
Author(s):  
Johannes Janssen ◽  
Daniel Pohl ◽  
Peter Jeschke ◽  
Alexander Halcoussis ◽  
Rainer Hain ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Region ◽  
Cavity Flow ◽  
Main Flow ◽  
Pressure Probe ◽  
Stator Vane ◽  
Cfd Analyses ◽  
Annular Cascade ◽  
The Impact ◽  
Variable Stator

Abstract This paper presents the impact of an axially tilted variable stator vane platform on penny cavity flow and passage flow, with the aid of both optical and pneumatic measurements in an annular cascade wind tunnel as well as steady CFD analyses. Variable stator vanes (VSVs) in axial compressors require a clearance from the endwalls. This means that penny cavities around the vane platform are inevitable. Production and assembly deviations can result in a vane platform which is tilted about the circumferential axis. Due to this deformation, backward facing steps occur on the platform edge. Penny cavity and main flow in geometries with and without platform tilting were compared in an annular cascade wind tunnel, which comprises a single row of 30 VSVs. Detailed particle image velocimetry (PIV) measurements were conducted inside the penny cavity and in the vane passage. Steady pressure and velocity data was obtained by two-dimensional multi-hole pressure probe traverses in the inflow and the outflow. Furthermore, pneumatic measurements were carried out using pressure taps inside the penny cavity. Additionally, oil flow visualization was conducted on the airfoil, hub, and penny cavity surfaces. Steady CFD simulations with boundary conditions, according to the measurements, have been benchmarked against experimental data. The results show that tilting the VSV platform reduces the mass flow into and out of the penny cavity. By decreasing penny cavity leakage, platform tilting also affects the passage flow where it leads to a reduced turbulence level and total pressure loss in the leakage flow region. In summary, the paper demonstrates the influence of penny platform tilting on cavity flow and passage flow and provides new insights into the mechanisms of penny cavity-associated losses.

Experiments on an Axial Fan Stage: Time-Resolved Analysis of Rotating Instability Modes

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Benjamin Pardowitz ◽  
Ulf Tapken ◽  
Lars Neuhaus ◽  
Lars Enghardt
Keyword(s):  
Leading Edge ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Fan ◽  
Time Resolved ◽  
Instability Waves ◽  
Instability Modes ◽  
Mode Decomposition ◽  
Rotating Instability ◽  
Annular Cascade

Rotating instability (RI) occurs at off-design conditions in axial compressors, predominantly in rotor configurations with large tip clearances. Characteristic spectral signatures with side-by-side peaks below the blade passing frequency (BPF) are typically referred to RI located in the clearance region next to the leading edge (LE). Each peak can be assigned to a dominant circumferential mode. RI is the source of the clearance noise (CN) and an indicator for critical operating conditions. Earlier studies at an annular cascade pointed out that RI modes of different circumferential orders occur stochastically distributed in time and independently from each other, which is contradictory to existing explanations of RI. Purpose of the present study is to verify this generally with regard to axial rotor configurations. Experiments were conducted on a laboratory axial fan stage mainly using unsteady pressure measurements in a sensor ring near the rotor LE. A mode decomposition based on cross spectral matrices was used to analyze the spectral and modal RI patterns upstream of the rotor. Additionally, a time-resolved analysis based on a spatial discrete-Fourier-transform (DFT) was applied to clarify the temporal characteristics of the RI modes and their potential interrelations. The results and a comparison with the previous findings on the annular cascade corroborate a new hypothesis about the basic RI mechanism. This hypothesis implies that instability waves of different wavelengths are generated stochastically in a shear layer resulting from a backflow in the tip clearance region.

scholarly journals Investigation of Tip Leakage Effects in Transonic Flow Using a Parallel Unstructured Navier-Stokes Code

1997 ◽  
Author(s):  
C-W. Hustad ◽  
A. Bölcs ◽  
M. Wehner
Keyword(s):  
Boundary Layer ◽  
Adaptive Mesh Refinement ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Tip Leakage Flow ◽  
Experimental Conditions ◽  
Tip Leakage ◽  
Annular Cascade ◽  
Case Number

Calculated results for tip flow around two different blade configurations are presented and compared with experimental data. The first configuration (case number 1) is a flat-plate profile tested in a linear transonic tunnel — the profile is an idealized representation of the aft-section of some highly curved turbine blades. The second configuration (case number 2) originates from the outer profile on the last-stage-blade of a steam turbine, however it is also reminiscient of a section from a turbine blade with supersonic exit flow. This configuration was tested in an annular cascade at Mach numbers representative of engine operating conditions. The computed results were obtained using a parallel 3D unstructured Navier-Stokes code. The code runs on a work-station cluster, as well as being optimized for the 256 processor Cray T3D at EPFL: the code is capable of gigaflop performance using more than 3 million cells — adaptive mesh refinement thus allows enhanced resolution within the tip gap region. For each configuration we have calculated two Runs. In both cases, Run-1 is similar to the experimental conditions, so that direct comparison between measured and calculated results is possible. With case number 1/Run-2 we re-calculated the flow without imposing a prescribed inflow boundary-layer along the sidewall. Comparison between the two runs helped reveal how free-stream total pressure can establish itself within the tip gap region. For the second configuration — in the annular cascade — we were interested in observing the influence of relative movement between the blade tip and adjacent sidewall. Hence for case number 2/Run-2 we imposed a circumferential velocity on the adjacent sidewall. This modified the effective sidewall boundary-layer and had a noticeable influence on the development of the tip-leakage flow.

scholarly journals Navier-Stokes Analysis of Unsteady Transonic Flows Through Gas Turbine Cascades With and Without Coolant Ejection

1997 ◽  
Author(s):  
T. Tanuma ◽  
N. Shibukawa ◽  
S. Yamamoto
Keyword(s):  
Gas Turbine ◽  
Stokes Equations ◽  
Viscous Flows ◽  
Navier Stokes ◽  
Implicit Time ◽  
Trailing Edge ◽  
Navier Stokes Equations ◽  
Time Marching ◽  
Turbine Cascades ◽  
Annular Cascade

An implicit time-marching higher-order accurate finite-difference method for solving the two-dimensional compressible Navier-Stokes equations was applied to the numerical analyses of steady and unsteady, subsonic and transonic viscous flows through gas turbine cascades with trailing edge coolant ejection. Annular cascade tests were carried out to verify the accuracy of the present analysis. The unsteady aerodynamic mechanisms associated with the interaction between the trailing edge vortices and shock waves and the effect of coolant ejection were evaluated with the present analysis.

Research on the Periodicity of Flow Field in a Compressor Sector Cascade

2020 ◽  
Author(s):  
Wenfeng Xu ◽  
Peng Sun ◽  
Guogang Yang
Keyword(s):  
Flow Field ◽  
Design Method ◽  
Flow Characteristics ◽  
Suction Side ◽  
Low Energy ◽  
Experimental Conditions ◽  
Flow Passage ◽  
Aerodynamic Parameters ◽  
Real Flow ◽  
Annular Cascade

Abstract Sector cascade experiments can not only be convenient to measure various aerodynamic parameters but also reveal the real flow characteristics in turbomachinery. However, the sector cascade is only a part of the whole annular cascade. The circumferential angle, the structure of the side guide plate (SGP) and the suction mode on the SGP have a great effect on the periodicity of the flow field. Therefore, the effect of structure on periodicity must be taken into consideration in order to obtain accurate data of the sector cascade experiment. In this paper, a compressor sector cascade composed of a row of adjustable guide vanes (AGVs) and a row of stators is designed. The effect of the circumferential angle, SGP structure and suction position on the periodicity is studied by numerical simulation. An optimal cascade scheme is selected for experimental research. The results show that a larger circumferential angle can weaken the effect of low-energy fluid near the SGP on the middle passages. However, given the limited experimental conditions, the circumferential angle is set at 110° which consists of 15 AGVs and 14 stators. What’s more, the SGP with the same bowed angle of AGV on both sides of the cascade can reduce the influence of the SGP on the adjacent passages and obtain a regular periodicity. The low-energy fluids still accumulate near the SGP. The suction near the stator suction side of the SGP can alleviate the blockage in the flow passage and further improve the periodicity of the cascade. Serious analysis of the experiment results have further identified that the suction near the stator suction side of SGP can make the aerodynamic parameters of the flow field uniform and lead to a good periodicity. At the same time, the feasibility of this design method is verified.

A Cold Heat Transfer Tunnel for Gas Turbine Research on an Annular Cascade

1993 ◽  
Author(s):  
R. F. Martinez-Botas ◽  
A. J. Main ◽  
G. D. Lock ◽  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Region Of Interest ◽  
Secondary Flows ◽  
Test Duration ◽  
Pressure Distributions ◽  
Exit Mach Number ◽  
Nozzle Guide ◽  
Turbine Design ◽  
Annular Cascade

The Oxford University Blowdown Tunnel has been substantially modified to test a large annular cascade of high pressure nozzle guide vanes (mean blade diameter of 1.11 m and axial chord of 0.0673 m). The new transonic facility has been constructed to obtain complete contours of heat transfer coefficient for both the end walls and blade surfaces using the transient liquid crystal technique, to measure pressure distributions and losses, and to study fundamental aspects of boundary layers and secondary flows. The facility allows an independent variation of Reynolds and Mach numbers, providing aerodynamic and heat transfer measurements in the region of interest for gas turbine design. The mass flow rate through the cascade at NGV design conditions (exit Mach number 0.96 and Reynolds number 2.0 × 106) is 38 kg/s and the pressure-regulated test duration exceeds 7 seconds.

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