Flow Structure on a Retreating Rotor Blade at High Advance Ratios

2014 ◽  
Author(s):  
Michael Mayo ◽  
Vrishank Raghav ◽  
Natasha Barbely ◽  
Brandon Liberi ◽  
Narayanan Komerath
Keyword(s):  
Rotor Blade ◽  
Reverse Flow ◽  
Rotor Blades ◽  
Static Case ◽  
Rotating Blade ◽  
Image Velocimetry ◽  
Order Of Magnitude ◽  
Stereo Particle Image Velocimetry ◽  
Edge Vortex ◽  
Attached Vortex

This paper provides unambiguous velocity-field proof that a strong edge vortex occurs on a rotating blade in reverse flow. The rotor blades of a helicopter encounter reverse flow during flight at high advance ratio. Reverse flow is a limiter in rotorcraft design with excursions in pitch link loads and bending moments. Stereo particle-image velocimetry is used on the flow under the retreating blade of a two-bladed teetering rotor system in a low speed wind tunnel. The results are correlated with earlier aerodynamic loads and flow visualization data using the same rotor blade planform placed in a yawed, fixed-wing position. Results obtained with the blade held fixed at several rotor azimuths and angles of attack are used to ascertain the rotation effects on the flowfield by comparison with rotating blade results. Initial results suggest that radial velocity due to rotation hinders separation and delays the formation of an attached vortex, compared to the static case. The circulation of the reverse flow attached vortex is of the same order of magnitude as the bound circulation of the airfoil section, proving that the vortex contributes significantly to the lift force in addition to the pitching moment.

Dynamic Effects in the Reverse Flow Velocity Field

2015 ◽  
Author(s):  
Dhwanil Shukla ◽  
Nandeesh Hiremath ◽  
Vrishank Raghav ◽  
Narayanan Komerath
Keyword(s):  
Rotor Blade ◽  
Static Pressure ◽  
Reverse Flow ◽  
Radial Pressure ◽  
Rotor Blades ◽  
Sharp Edge ◽  
Minor Effect ◽  
Reversed Flow ◽  
Flow Speeds ◽  
Edge Vortex

At high edgewise flow speeds, reversed flow causes excursions in pitching moment and blade torsion on the rotor blades of helicopters and wind turbines. Our prior work has shown that a yawed fixed wing at angle of attack in reversed flow generates a sharp-edge vortex. The sharp-edge vortex is a primary feature of the flow under the rotor blade. During operation as a rotor blade at high advance ratio in a wind tunnel, stereo PIV results show that the well-formed sharp-edge vortex at 240 degrees azimuth resembles that on a forward-swept wing. This vortex stops growing before 270 degrees and convects with the blade by 300 degrees. Static pressure computed from interpolated velocity data show the effects of vortex-induced radial pressure gradient. This explains the finding of inboard-directed radial flow at 300 degrees azimuth, overcoming centrifugal effects. Viscous stress is shown to have only a minor effect on the static pressure field computation.

Pressure Fields Around a Rotor Blade in Reverse Flow

2016 ◽  
Author(s):  
Nandeesh Hiremath ◽  
Dhwanil Shukla ◽  
Zujia Huang ◽  
Narayanan Komerath
Keyword(s):  
Velocity Field ◽  
Rotor Blade ◽  
Reverse Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Test Case ◽  
Cylinder Test ◽  
Component Velocity ◽  
Blade Section ◽  
Pressure Extraction ◽  
Edge Vortex

The flowfield and pressure distribution of a rotor blade in reverse flow is studied using stereoscopic particle image velocimetry. The 2-bladed teetering rotor with rigid NACA0013 untwisted untapered blades, with manually set collective and cyclic pitch, is operated at advance ratios from 0.7 to 1.0. Results are presented from azimuths 240 and 270 degrees, where the velocity field in chordwise sectional planes at two radial stations are analyzed, at two advance ratios. The paper is focused on two aspects. First is calculation of the total circulation around each blade section, and around the strong sharp-edge vortex seen below the blade in these sections. The second is the surface and flowfield pressures derived from the 3-component velocity field obtained from closely-spaced planes, after interpolation to satisfy the mass continuity equation. The pressure extraction technique is being developed using a yawed-cylinder test case, and shows good success in satisfying continuity between data planes.

Vortex Flow Hypothesis for Rotor Blades in Reverse Flow

2013 ◽  
Author(s):  
Michael Mayo ◽  
Nicholas Motahari ◽  
Vrishank Raghav ◽  
Narayanan Komerath
Keyword(s):  
Vortex Flow ◽  
Delta Wing ◽  
Reverse Flow ◽  
Leading Edge ◽  
Flow Region ◽  
Rotor Blades ◽  
Bending Moments ◽  
High Speeds ◽  
Edge Vortex ◽  
Pressure Perturbations

Slowed rotors are used to increase the cruise efficiency and maneuverability of rotorcraft at high speeds. Operation at high rotor advance ratios implies that the blades encounter reverse flow on the retreating side of the rotor disc. The resulting increased pitch link loads and bending moments could shorten component life. Previous studies have shown significant rotor blade pressure perturbations in the reverse flow region, which are not fully accounted for using current prediction methodologies. The hypothesis explored here is that the blade trailing edge in reverse flow produces a vortex similar to the leading edge vortex on a sharp-edged delta wing. The Polhamus model for delta wing lift is modified for use on yawed rotor blades. Lift, drag and pitching moment data acquired on a static yawed blade in reverse flow supports analytical results. Surface tuft flow visualization confirms the existence of an attached, span-wise vortex.

Vorticity transport in the leading-edge vortex on a rotating blade

2014 ◽  
Vol 743 ◽  
pp. 249-261 ◽  
Author(s):  
Craig J. Wojcik ◽  
James H. J. Buchholz
Keyword(s):  
Leading Edge ◽  
Quasi Equilibrium ◽  
Transport Mechanisms ◽  
Leading Edge Vortex ◽  
Rotating Blade ◽  
Edge Vortex ◽  
Rotation Motion ◽  
Vorticity Transport ◽  
Control Volumes ◽  
Quiescent Fluid

AbstractVorticity transport is analysed within the leading-edge vortex generated on a rectangular flat plate of aspect ratio 4 undergoing a starting rotation motion in a quiescent fluid. Two analyses are conducted on the inboard half of the blade to better understand the vorticity transport mechanisms responsible for maintaining the quasi-equilibrium state of the leading-edge vortex. An initial global analysis between the $25$ and $50\, \%$ spanwise positions suggests that, although spanwise velocity is significant, spanwise convection of vorticity is insufficient to balance the flux of vorticity from the leading-edge shear layer. Subsequent detailed analyses of vorticity transport in planar control volumes at the $25$ and $50\, \%$ spanwise positions verify this conclusion and demonstrate that vorticity annihilation due to interaction between the leading-edge vortex and the opposite-sign layer on the plate surface is an important, often dominant, mechanism for regulation of leading-edge-vortex circulation. Thus, it provides an important condition for maintenance of an attached leading-edge vortex on the inboard portion of the blade.

Analysis of the Stress Intensity of Rotor Blade in Hydraulic Retarder

2011 ◽  
Vol 179-180 ◽  
pp. 1453-1458
Author(s):  
Jun Yan
Keyword(s):  
Stress Intensity ◽  
Coordinate Transformation ◽  
Rotor Blade ◽  
Distribution Functions ◽  
Rotor Blades ◽  
Fea Model ◽  
Numeric Simulation ◽  
Braking Torque ◽  
Flow Pressure ◽  
Hydraulic Retarder

Based on CFD numeric simulation for hydraulic retarder under full-filled condition, the pressure distribution functions of the rotor blades surfaces are approached by coordinate transformation and surface fitting. Through the APDL program, loads which involved not only centrifugal force but also flow pressure are loaded on the FEA model according to the approximating pressure functions. The FEA model is solved and the blades strength is analyzed more accurately. Noted moment and speed, that is respectively 4000 N • m and 1343rpm, is determined under the promise of blade strength, and controlling strategy is made that constant braking torque shoud be carried out when speed is higher than noted value .

Degradation of Aerodynamic Performance of an Intermediate-Pressure Steam Turbine Due to Erosion of Nozzle Guide Vanes and Rotor Blades

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Koichi Yonezawa ◽  
Tomoki Kagayama ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Steam Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Flow Angle ◽  
Guide Vanes ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Deteriorations of nozzle guide vanes (NGVs) and rotor blades of a steam turbine through a long-time operation usually decrease a thermal efficiency and a power output of the turbine. In this study, influences of blade deformations due to erosion are discussed. Experiments were carried out in order to validate numerical simulations using a commercial software ANSYS-cfx. The numerical results showed acceptable agreements with experimental results. Variation of flow characteristics in the first stage of the intermediate pressure steam turbine is examined using numerical simulations. Geometries of the NGVs and the rotor blades are measured using a 3D scanner during an overhaul. The old NGVs and the rotor blades, which were used in operation, were eroded through the operation. The erosion of the NGVs leaded to increase of the throat area of the nozzle. The numerical results showed that rotor inlet velocity through the old NGVs became smaller and the flow angle of attack to the rotor blade leading edge became smaller. Consequently, the rotor power decreased significantly. Influences of the flow angle of at the rotor inlet were examined by parametric calculations and results showed that the angle of attack was an important parameter to determine the rotor performance. In addition, the influence of the deformation of the rotor blade was examined. The results showed that the degradation of the rotor performance decreased in accordance with the decrease of blade surface area.

scholarly journals A Robot-Assisted Large-Scale Inspection of Wind Turbine Blades in Manufacturing Using an Autonomous Mobile Manipulator

2021 ◽  
Vol 11 (19) ◽  
pp. 9271
Author(s):  
Heiko Engemann ◽  
Patrick Cönen ◽  
Harshal Dawar ◽  
Shengzhi Du ◽  
Stephan Kallweit
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Large Scale ◽  
Turbine Blades ◽  
Rotor Blades ◽  
Mobile Manipulator ◽  
Wind Turbine Blades ◽  
Left Hand ◽  
Planning Strategy ◽  
Execution Strategy

Wind energy represents the dominant share of renewable energies. The rotor blades of a wind turbine are typically made from composite material, which withstands high forces during rotation. The huge dimensions of the rotor blades complicate the inspection processes in manufacturing. The automation of inspection processes has a great potential to increase the overall productivity and to create a consistent reliable database for each individual rotor blade. The focus of this paper is set on the process of rotor blade inspection automation by utilizing an autonomous mobile manipulator. The main innovations include a novel path planning strategy for zone-based navigation, which enables an intuitive right-hand or left-hand driving behavior in a shared human–robot workspace. In addition, we introduce a new method for surface orthogonal motion planning in connection with large-scale structures. An overall execution strategy controls the navigation and manipulation processes of the long-running inspection task. The implemented concepts are evaluated in simulation and applied in a real-use case including the tip of a rotor blade form.

scholarly journals Failure Analysis of Gas Turbine Rotary Blade

2017 ◽  
pp. 1-6
Keyword(s):  
Finite Element ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Centrifugal Forces ◽  
Analysis Software ◽  
Two Stage ◽  
Element Analysis ◽  
Finite Element Software ◽  
Super Alloy

In the present work the first stage rotor blade of a two- stage gas turbine has been analyzed for structural, thermal using ANSYS 9.0, which is a powerful Finite Element Software. In the present work, the first stage rotor blade of the gas turbine has been analyzed for the mechanical and radial elongations resulting from the tangential, axial and centrifugal forces. The gas forces namely tangential, axial were determined by constructing velocity triangles at inlet and exist of rotor blades. The rotor blade was then analyzed using ANSYS 9.0 for the temperature distribution. The material of the blade was specified as N155 but its properties were not given. This material is an iron based super alloy and structural and thermal properties at gas room and room temperatures. The turbine blade along with the groove is considered for the static, thermal, modal analysis. The first stage rotor blade of a two-stage gas turbine has been analyzed for structural, thermal using ANSYS 9.0 Finite Element Analysis software.

scholarly journals ACTIVE TWIST OF MODEL ROTOR BLADES WITH D-SPAR DESIGN

Transport ◽  
2007 ◽  
Vol 22 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Andrejs Kovalovs ◽  
Evgeny Barkanov ◽  
Sergejs Gluhihs
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Rotor Blade ◽  
Element Model ◽  
Rotor Blades ◽  
Helicopter Rotor ◽  
3D Finite Element ◽  
3D Finite Element Model ◽  
Helicopter Rotor Blade ◽  
Active Twist

The design methodology based on the planning of experiments and response surface technique has been developed for an optimum placement of Macro Fiber Composite (MFC) actuators in the helicopter rotor blades. The baseline helicopter rotor blade consists of D‐spar made of UD GFRP, skin made of +450/‐450 GFRP, foam core, MFC actuators placement on the skin and balance weight. 3D finite element model of the rotor blade has been built by ANSYS, where the rotor blade skin and spar “moustaches” are modeled by the linear layered structural shell elements SHELL99, and the spar and foam ‐ by 3D 20‐node structural solid elements SOLID 186. The thermal analyses of 3D finite element model have been developed to investigate an active twist of the helicopter rotor blade. Strain analogy between piezoelectric strains and thermally induced strains is used to model piezoelectric effects. The optimisation results have been obtained for design solutions, connected with the application of active materials, and checked by the finite element calculations.

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