scholarly journals Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure

2021 ◽  
Vol 11 (20) ◽  
pp. 9545
Author(s):  
Friederike Jensen ◽  
Marina Terlau ◽  
Michael Sorg ◽  
Andreas Fischer
Keyword(s):  
Rotor Blade ◽  
Test Specimen ◽  
Surface Defects ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Contactless Measurement ◽  
Viewing Angle ◽  
Pulse Thermography ◽  
Long Pulse

Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive and contactless measurement technique is applied to a strongly curved and coated test specimen for the first time. This specimen is similar in structural size and design to a rotor blade leading edge and introduced with sub-surface defects whose diameters range between 2mm and 3.5mm at depths between 1.5mm and 2.5mm below the surface. On the curved and coated test specimen, sub-surface defects with a depth-to-diameter ratio of up to 1.04 are successfully detected. In particular, defects are also detectable when being observed from a non-perpendicular viewing angle, where the intensity of the defects decreases with increasing viewing angle due to the strong surface curvature. In conclusion, long-pulse thermography is suitable for the detection of sub-surface defects on coated and curved components and is therefore a promising technique for the on-site application during inspection of rotor blade leading edges.

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.

A Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Tip-Shroud Labyrinth Seal Effect on the Flutter Stability of Turbine Rotor Blades

2019 ◽  
Author(s):  
Roque Corral ◽  
Michele Greco ◽  
Almudena Vega
Keyword(s):  
Rotor Blade ◽  
Labyrinth Seal ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Stability Prediction ◽  
Labyrinth Seals ◽  
Turbine Rotor Blade ◽  
The Stability ◽  
Shrouded Rotor ◽  
Tip Shroud

Abstract The effect of the tip-shroud seal on the flutter onset of a shrouded turbine rotor blade, representative of a modern gas turbine, is numerically tested and the contribution to the work-per-cycle of the aerofoil and the tip-shroud are clearly identified. The numerical simulations are conducted using a linearised frequency domain solver. The flutter stability of the shrouded rotor blade is evaluated for an edgewise mode and compared with the standard industrial approach of not including the tip-shroud cavity. It turns out that including the tip shroud significantly changes the stability prediction of the rotor blade. This is due to the fact that the amplitude of the unsteady pressure created in the inter-fin cavity, due to the motion of the airfoil, is much greater than that of the airfoil. It is concluded that the combined effect of the seal and its platform tends to stabilise the rotor blade for all the examined nodal diameters and reduced frequencies. Finally, the numerical results are shown to be consistent with those obtained using an analytical simplified model to account for the effect of the labyrinth seals.

scholarly journals Flutter Behavior of Highly Flexible Two- and Three-bladed Wind Turbine Rotors

2021 ◽  
Author(s):  
Mayank Chetan ◽  
Shulong Yao ◽  
D. Todd Griffith
Keyword(s):  
Wind Turbine ◽  
Structural Design ◽  
Comprehensive Evaluation ◽  
Turbine Blades ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flutter Speed ◽  
Cost Of Energy ◽  
Manufacturing Technologies

Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the Levelized Cost of Energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aero-elastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, new rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.

scholarly journals A Numerical Method for the Analysis of 3D Viscous Compressible Flow in Turbine Cascades: Application to Secondary Flow Development in a Cascade With and Without Dihedral

1986 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Compressible Flow ◽  
Three Dimensional ◽  
Leading Edge ◽  
Computer Code ◽  
Horseshoe Vortex ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Flow Development ◽  
Viscous Compressible Flow

The present paper describes a computer code, currently under development, aimed at solving the equations of three-dimensional viscous compressible flow in turbomachinery goemetries. The code uses a simple, novel pre-processed implicit algorithm. An outline of the method is given and the current capabilities of the code are assessed. The code is applied to the study of the flowfield in a cascade of transonic gas turbine rotor blades. The geometry and the presence of inlet end-wall boundary layers lead to significant three-dimensional effects. The pattern of secondary flow development, including the details of the leading edge horseshoe vortex and associated saddle point, are clearly resolved and correspond to experimental experience. A computation is also presented to show the influence of dihedral (non-linear stacking) on the secondary flow development.

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.

Experimental Heat Transfer Investigation Around the Film-Cooled Leading Edge of a High-Pressure Gas Turbine Rotor Blade

1985 ◽  
Vol 107 (4) ◽  
pp. 1016-1021 ◽  
Author(s):  
C. Camci ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Rotor Blade ◽  
Free Stream ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Temperature Ratio ◽  
Turbine Rotor Blade ◽  
Experimental Heat ◽  
Experimental Heat Transfer

This paper describes an experimental heat transfer investigation around the leading edge of a high-pressure film-cooled gas turbine rotor blade. The measurements were performed in the VKI isentropic compression tube facility using platinum thin film gauges painted on a blade made of machinable glass ceramic. Free-stream to wall temperature ratio, Reynolds, and Mach numbers were selected from actual aeroengines conditions. Heat transfer data obtained without and with film cooling in a stationary frame are presented. The effects of coolant to free-stream mass weight ratio and temperature ratio were successively investigated. Heat transfer modifications due to incidence angle variations were interpreted with the aid of inviscid flow calculation methods.

scholarly journals Design and analysis of displacement models for modular horizontal wind turbine blade structure

2020 ◽  
Vol 39 (1) ◽  
pp. 121-130
Author(s):  
E.M. Etuk ◽  
A.E. Ikpe ◽  
U.A. Adoh
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Structural Damage ◽  
Axial Loading ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Horizontal Wind ◽  
Normal Loading ◽  
Loading Cycle ◽  
Wind Turbine Rotor

This study examined the normal, radial, axial and tangential loading cycles undergone by wind turbine rotor blades and their effects on the  displacement of the blade structure. The rotor blade was modelled using Q Blade finite element sub module, which evaluated the loading cycles in  terms of the forces induced on the blade at various frequencies through several complete revolution cycles (360o each cycle). At frequencies of 5 HZ, 23 Hz, 60 Hz, 124 Hz and 200 Hz, maximum strain deformation of 0.004, 0.04, 0.08, 0.14 and 0.24 were obtained, and geometry of the deformed blades were characterized by twisting and bending configuration. Maximum deflections from tangential loading increased from -0.55-1.2 mm,  -0.39-1.6 mm from axial loading, -0.28-1.8 mmfrom radial loading and -0.01-2.3 mm from normal loading. From these deflection values, normal loading cycle would cause the highest level of structural damage on the rotor blade followed by radial, axial and tangential loading. Moreover, the  strain deformations and deflections of the blade structure increased as the cycles of frequency increased. Keywords: Loading cycle, Wind turbine, Rotor blade, Frequency, Strain deformations, Deflections.

scholarly journals Full scale deformation measurements of a wind turbine rotor in comparison with aeroelastic simulations

2020 ◽  
Author(s):  
Stephanie Lehnhoff ◽  
Alejandro Gómez González ◽  
Jörg R. Seume
Keyword(s):  
Wind Turbine ◽  
Rotor Blade ◽  
Plane Deformation ◽  
Field Measurements ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Strain Gauges ◽  
Aeroelastic Simulations ◽  
Good Agreement ◽  
Wind Turbine Rotor

Abstract. The measurement of deformation and vibration of wind turbine rotor blades becomes highly important as the length of rotor blades increases with the growth in demand for wind power. The requirement for field validation of the aeroelastic behaviour of wind turbines increases with the scale of the deformation, in particular for modern blades with very high flexibility and coupling between different vibration modes. However, performing full-scale field measurements for rotor blade deformation is not trivial and requires high temporal and spatial resolution. A promising deformation measurement technique is based on an optical method called Digital Image Correlation (DIC). A system for the application of DIC for full field measurements of wind turbine rotors has been developed and validated in the past years by ForWind, Institute of Turbomachinery and Fluid Dynamics, Leibniz Universität Hannover. The whole rotor of the wind turbine is monitored with a stereo camera system from the ground during measurement. Recently, DIC measurements on a Siemens Gamesa SWT-4.0-130 test turbine were performed on the tip of all blades with synchronized measurement of the inflow conditions by a ground-based LiDAR. As the turbine was additionally equipped with strain gauges in the blade root of all blades, the DIC results can be directly compared to the actual prevailing loads. In the end, the measured deformations are compared to aeroelastic simulations. The deformation measured with DIC on the rotor blade tips shows the same qualitative behaviour when compared to loads measured with strain gauges in the blade root. This confirms that the DIC measurements correlate with the prevailing loads in reality. The comparison with aeroelastic simulations shows that the amplitude and trend of the in-plane deformation is in very good agreement with the DIC measurements. The out-of-plane deformation shows slight differences, which could be caused by the difference between real wind conditions and the wind statistics on which the simulations are based. The combined rotor blade pitch and torsion angle measured with DIC is in good agreement with the actual pitch value of the turbine. A detailed comparison with aeroelastic simulations shows that the amplitude of torsion measured with DIC is higher which might be caused by an inaccuracy of the experimental setup. This will be focus of future work. All in all, DIC shows very good agreement with comparative measurements and simulations which shows that it is a suitable method for measurements of deformation and torsion of multi-megawatt wind turbine rotor blades.

scholarly journals Numerical and Experimental Vibration Analysis of a Steam Turbine Rotor Blade

2021 ◽  
Vol 15 (4) ◽  
pp. 462-466
Author(s):  
Marko Katinić ◽  
Marko Ljubičić
Keyword(s):  
Numerical Model ◽  
Modal Analysis ◽  
Steam Turbine ◽  
Vibration Analysis ◽  
Rotor Blade ◽  
High Reliability ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Turbine Rotor Blade ◽  
Computer Environment

Damage to the rotor blade of a steam turbine is a relatively common problem and is one of the leading causes of sudden and unplanned shutdowns of a steam turbine. Therefore, the high reliability of the rotor blades is very important for the safe and economical operation of the steam turbine. To ensure high reliability, it is necessary to perform a vibration analysis of the rotor blades experimentally and in a computer environment. In this paper, a modal analysis was performed on the twisted blade of the last stage of the turbine in the Ansys software. The results of the modal analysis of the stationary rotor blade were compared with the results obtained by the bump test, which confirmed the numerical model of the blade. A modal analysis of a rotating rotor blade was performed on the same numerical model, and Campbell diagrams were plotted to determine the critical speed

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