Blade Deformation Research Articles

РАСЧЕТНОЕ ПРОГНОЗИРОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ОСТАТОЧНЫХ ДЕФОРМАЦИЙ ЛОПАТОК ГТД НА ЭТАПЕ КОНЦЕВОГО ФРЕЗЕРОВАНИЯ

The article presents a technique that makes it possible to predict the technological residual deformations of GTE blades obtained at the stages of end milling as a result of the effect of residual stresses. The first part of the technique makes it possible to determine the magnitude, bijugat and character of the residual stresses distribution formed in the surface layer of the workpieces in the operations of end milling. The adequacy of the technique was verified by investigating the convergence of the numerical computation results with the results of field experiments. As a result of the research, a power-law dependence was obtained, which makes it possible to determine the value of the maximum circumferential residual stresses depending on the parameters of the end milling processing mode. The second part of the technique makes it possible to determine the residual deformations of the GTE blade based on the residual stress distribution diagrams obtained when using of the first part of the technique or obtained on the basis of field experimental investigations. Also, power-law dependences are obtained in this work, which make it possible to determine the value of the maximum deviations of the control sections of the investigated GTE blade, depending on the parameters of the end milling mode.

Measuring deformations of the fan blade by optical methods

Across industries, the demand for the ability to analyze components in operation and make decisions on repair based on the data obtained is growing rapidly. There is the potential to ensure safer operations while saving the cost of unnecessary new parts. A quick and relatively inexpensive method is a 3D scanner - the device that can scan a real component and create an accurate 3D model. For stationary cases - inspecting parts or assemblies - these are already established methods. In contrast, measurement of vibrations and deformations in operation is still not widespread and for turbomachinery, it can be a new direction of development.

Aerodynamic and dynamic loading in a blade cascade designed for flutter research

Flow-induced vibration of turbine and compressor blades, so called blade flutter, represents a serious problem for designers and operators of large turbomachines. The research of mechanisms leading to this dangerous aeroelastic instability, which can occur especially in modern long and slender blades, is hindered by lack of experimental data. A new experimental setup for controlled flutter testing has been designed in cooperation of the Institute of Thermomechanics of the Czech Academy of Sciences and Faculty of Mechatronics of the Technical University of Liberec. The test section consists of five planar blades placed in a transonic wind tunnel, with high-frequency torsional oscillation of the middle blade driven by an electric motor. The contribution presents the results of first measurements, namely the static pressure distribution for various inlet Mach numbers, aerodynamic moments and deformation of the middle blade due to inertial loads during high-frequency oscillation.

Effect of Impact and Bearing Parameters on Bird Strike with Aero-Engine Fan Blades

Bird strikes are one of the most dangerous incidents occurring to aircraft engines and can inflict heavy casualties and economic losses. In this study, a smoothed particle hydrodynamics (SPH) mallard bird model has been used to simulate bird impact to rotary aero-engine fan blades. The simulations were performed using the finite element method (FEM) by means of LS-DYNA. The reliability of the material model and numerical method was verified by comparing the numerical results with Wilbeck’s experimental results. The effects of impact and bearing parameters, including bird impact location, bird impact orientation, initial bird velocity, fan rotational speed, stiffness of the bearing, and the damping of the bearing on the bird impact to aero-engine fan blade are studied and discussed. The results show that both the impact location and bird orientation have significant effects on the bird strike results. Bird impact to blade roots is the most dangerous scenario causing the impact force to reach 390 kN. The most dangerous orientation is the case where the bird’s head is tilted 45° horizontally, which leads to huge fan kinetic energy loss as high as 64.73 kJ. The bird’s initial velocity affects blade deformations. The von Mises stress during the bird strike process can reach 1238 MPa for an initial bird velocity of 225 m/s. The fan’s rotational speed and the bearing stiffness affect the rotor stability significantly. The value of bearing damping has little effect on the bird strike process. This paper presents a procedure for evaluating the strength of fan blades against bird strike in the design stage.

Main rotor blade modeling approaches comparison. Finite element and Craig-Bampton methods

The paper focuses on the helicopter main rotor blade FE model. And the main goal is to prove the feasibility of the helicopter main rotor MBD model in calculations of blade deformation as a result of applied aerodynamic forces. FE model is used as a basis for two different computational methods. A mathematical approach in the MBD based on the Craig-Bampton method on the one hand. And finite element model on the other hand. The results of high-frequency blade rotations are obtained. Calculations of these models are compared in order to determine the best method for modeling a linear-elastic blade. By the results, it is necessary to consider the preloaded state of the blade when using the Craig-Bampton method approach. The comparison of blade nodes displacements at various external conditions for both models are given. The influence of rotor MBS model damping parameters on the amplitude of blade oscillations under sinusoidal action is considered.

Creep behavior of nickel-based single crystal superalloy under gradient loading

Nickel-based single crystal creep’s properties are commonly calculated according to the rupture strength under constant load. The creep deformation of turbine blades is not only occurred under constant loading but also the variable loading. The influence of variable load on creep deformation should also be considered. Based on this background, in the present study, gradient loading creep tests of DD6 nickel-based single crystal are carried out under two modes. Take load and holding times into account, the creep characteristics and microstructure evolution is studied. The results show that the load and holding time have significant effects on the creep properties of nickel-based single crystals. The change of load induces an instantaneous jump on the creep deformation and strain rate. The holding time of each loading stage mainly affects the evolution of the internal microstructure of nickel-based single crystal. The research on creep behavior of nickel-based single crystal under gradient load in this paper not only enriches the service performance evaluation of nickel-based single crystal under complex environment but also provides a reference for material design and performance optimization.

Structure and modal analysis of the last stage blade in steam turbine under low volume flow conditions

To explore the prestressed modal characteristics of the last stage blade in steam turbine under low volume flow conditions, the fluid–structure interaction (FSI) method of ANSYS mechanical + CFX is adopted to consider the effect of flow field on the strength performance of the rotor blade. The cyclic symmetry analysis is adopted to calculate the strength performance and modal characteristics of the rotor blade. The results show that the flow field of the last stage is composed of backflow vortex, separation vortex and tip clearance vortex under low volume flow conditions. The tip clearance vortex has high circumferential velocity and temperature. The maximum deformation of the rotor blade is on the leading edge of the blade at 80% span, and the maximum equivalent stress is on the suction surface at 90% span. With the decrease of the steam flow, the temperature at the blade tip increases significantly, which increases the maximum deformation and the equivalent stress of the rotor blade. The plastic deformation occurs when the steam flow is reduced to 15% turbine heat acceptance (THA). In addition, the elastic modulus of blade material decreases with the increase of temperature, which leads to the decrease of natural frequencies. From 35 %THA to 5% THA condition, the natural frequencies of the blade decrease by 34-136 Hz. This study provides a theoretical reference for the identification, diagnosis and prediction of the vibration of the last stage blade under low volume flow conditions.

Design and Manufacturing Method of GFRP Blades for Vertical Axis Wind Turbine

Today, environmental protection and the rational use of natural resources have become growing challenges. One of these aspects is energy producing with less impact on the environment. For some applications the small wind turbines can be a solution. In this paper are presented some aspects regarding the design and manufacturing technology of 500 W vertical axis wind turbine blades. The turbine will be installed in the urban environment so that requirements regarding rotor aesthetics and noise level will be considered. The optimal geometric parameters of the turbine rotor were determined by specialized MathCAD and elaborated in 3D modelling software. For the blades the NACA 0018 airfoil was used with the chord length of 110 mm and is constant throughout the length of the blade. The blades are helical and are 1800 mm long. To estimate the aerodynamic performance of the turbine rotor, a computational fluid dynamics model was developed using ANSYS CFX finite element analysis software. The authors proposed a new method for rapid prototyping of blades using fused deposition modelling procedure. In order to increase the mechanical properties, the blades were covered with several layers of glass-fibres reinforced polymer. Estimation the blade strength to operating loads was performed using Ansys Workbench software. The modelling of the composite material architecture on the blade surface was performed using the special ANSYS Composite PrepPost module. Several simulations were performed with different number of layers and stacking sequences. In order to prevent rotor over engineering the maximum rotation speed of 400 min−1 was accepted (equivalent to ≍12 m/s wind speed). Simulation of the blade strength to operating loads indicate values of around 40 MPa for shear stress (50% less than failure shear stress) and around 80 MPa principal stress (60% less than failure tensile stress). The maximum blade deformations of 3 – 4 mm shows that the blade is stiff enough at imposed operation conditions. For the blade manufacturing, based on the numerical analysis results, the configuration of the strength structure composed of 5 layers of GFRP was selected, which forms a total blade weight of 1895g.

A variable twist blade for horizontal axis wind turbines: Modeling and analysis

A method for analyzing the performance of a wind turbine blade design with an adaptive variable twist is presented. The possibility of implementing morphing features is becoming increasingly possible with innovative materials and manufacturing techniques. This motivates a blade concept consisting of multiple shell sections mounted on a rigid spar and covered by non-structural skin. The design allows the blade shells to adapt the twist angle distribution (TAD). The study is conducted using data acquired from the National Renewable Energy Laboratory (NREL) 20 kW wind turbine. A design problem is formulated to find the TAD that maximizes the aerodynamic efficiency for a discrete set of points that represent the Region 2 wind speed. The TAD is found for each point using a heuristic search algorithm. This algorithm searches through performance data that is acquired using the AeroDyn open source simulation software. Results from the model are validated with computational fluid dynamics (CFD) simulations using the Reynolds-averaged Navier-Stokes equations with the k-ω shear stress transport turbulence model. Through this first part of the analysis, it becomes possible to understand the required amount of blade deformation by the TAD function. Given this understanding, a stress analysis can be performed on the blade structure. The scenario considers the combined effect of twisting with aerodynamic loading. The blade load is determined by combining CFD with finite element analysis to facilitate the one-way fluid-structural interaction. The outcome of this work demonstrates how the proposed method can be used to determine the gain in efficiency, required range of motion, and structural performance of the blade shells for a given wind turbine blade design.

Species of sucking pests of ornamental crops in the conditions of the Southern Coast of the Crimea

The results of the analysis of the species composition of sucking pests species during the period from 2009 to 2019 are presented. Based on long-term phytosanitary monitoring, 37 species belonging to 12 families were identified, of which the most numerous are the families Diaspididae and Aphididae of the order Hemiptera. According to the nature of trophic connections, 59.9% are monophages, 32.4% are polyphages and 8.1% are oligophages. According to the nature of the damage caused, sucking species differ from each other. Some species lead to a change in the color of leaves and flowers (thrips, mites, coccids), others cause deformation of the leaf blade and inflorescences (coccids, worms, false coccids, herbivorous mites) and the third group includes species that form galls on the leaves (laurel psyllid, pistachio marginal gall aphid). According to ecological features, sucking pest species are divided into three main groups: open-living species, which include aphids, cicadae, psyllas, white flies, the second group includes species that have covers of various nature on the body, such as coccids, worms and false coccids, and the third group consists of gall makers. The dominant species, the degree of harmfulness, the frequency of occurrence and the range of forage plants were determined.

Noise Cancellation of Helicopter Blade Deformations Measurement by Fiber Bragg Gratings.

The work presents data treatment methods aimed at eliminating the noise in the strain sensor data induced by vibrations of the helicopter blade in flight conditions. The methods can be applied in order to enhance the metrological performance of the helicopter weight estimation system based on the deformation measurement of the main rotor blades. The experimental setup included a composite plate fixed to the vibrating stand on the one end, with six fiber-optic strain sensors attached to its surface. In this work, the procedure of the optimal linear smoothing (POLS) and 3D-invariant methods were used to obtain monotone calibration curves for each detector, thereby making it possible to distinguish the increase of load applied to the free end of the plate with an increment of 10 g. The second method associated with 3D invariants took into account 13 quantitative parameters defined as the combination of different moments and their intercorrelations up to the fourth-order inclusive. These 13 parameters allowed the calculation of the 3D surface that can serve as a specific fingerprint, differentiating one set of initial data from another one. The combination of the two data treatment methods used in this work can be applied successfully in a wide variety of applications.

Scheme optimization for a turbine blade under multiple working conditions based on the entropy weight vague set

Abstract. The deformation of blades under complex loads of multiple working conditions will reduce the energy conversion efficiency. To reduce the deviation of the blade shape in practical working conditions, a combination and optimization method of blade design schemes under multiple working conditions, based on the entropy weight vague sets, is proposed. The sensitivity of each working condition index is analyzed based on the information entropy, and the satisfaction degree of the design scheme based on the design requirements and experiences is described with the vague set. The matching degree of different design schemes for multiple working conditions is quantified according to the scoring function. The combination and optimization of the design scheme are verified by numerical simulation analysis. The results show that the proposed design scheme has a smaller blade shape deviation than the traditional design scheme under multiple working conditions.

Study on the dynamic fatigue performance of shot blasting machine’s blades based on modal analysis

Shot blasting is an important means of metal surface treatment, and the fracture of rotating blade is the main reason for the abnormal operation of shot blasting machine. In order to prolong the service life of the equipment, the dynamic fatigue characteristics of the blade are studied in this paper. A three-dimensional model of the blade is established and its constraint modal are analyzed by both simulation and experiment. The results show that the deformation of blade is proportional with the increase of natural frequency, and the stress concentration is easy to occur at the root of blade. Meanwhile, the dynamic fatigue test of the blade is carried out, and it can be found that the root of the blade breaks at the rotational speed of 750r/min, which verifies the correctness of simulation results. Therefore, it is necessary to effectively adjust the control speed to ensure the normal rotation of the blades and reliable operation of the machine.

End-to-end efficiency quantification of an autonomous underwater vehicle propulsion system

Increasing demand for versatile and long-endurance autonomous underwater vehicles puts significant design pressure on all aspects of AUV design and operation, including that of the propulsive system. The present study discusses testing of a thruster unit and several propellers developed to propel a hybrid glider/flight-style underwater vehicle. Due to the AUV being required to operate at largely different speeds and thrust levels between the two configurations, the propulsive subsystem needs to be capable of remaining efficient and effective across a wide range of operating conditions. Thus, the current results focus on quantifying all of the factors affecting the drive train, ranging from open-water performance of the propeller up to electro-mechanical efficiency of the magnetic coupling and geared electric motor. It is shown that, depending on the required operating point, total efficiency of the vehicle is primarily affected by non-linear low Reynolds number effects, sudden drop of gearbox efficiency at low revolutions and applied torques, as well as blade deformation, aside of the baseline propeller efficiency.

Operational Modal Analysis of Francis Turbine Runner Blades Using Transient Measurements

To prevent dynamic amplification or resonance during normal operation, which could result in large blade deformations and premature fatigue failure, structural mode frequencies are predicted using numerical models during design. However, such numerical models could benefit from validation using data obtained during commissioning. Here, we propose the use of asynchronous transient experimental measurements to identify regions where interaction between structural modes and Rotor-Stator Interaction (RSI) harmonics can be detected. From these regions, modal parameters can be estimated and compared with numerical predictions. This paper presents the methodology used to extract these modal parameters and estimate their uncertainties using data from a Francis runner recently commissioned by Hydro-Québec.

Characterizing dynamic deformation of marine propeller blades with stroboscopic stereo digital image correlation

Stereo digital image correlation (stereo-DIC) technique shows a powerful capacity on full-field three-dimensional (3D) deformation measurement of rotary machine structures. However, it remains a challenge for underwater applications due to difficulties in imaging, stereo calibration, light refraction, and so on. In this paper, its potential in characterizing 3D dynamic deformation of the underwater rotor blades is shown by solving these problems. A stroboscopic stereo-DIC system is established to capture clear speckle images of a blade that rotates in the windowed cavitation tunnel under different flow speeds. To calibrate the stereo camera for underwater object measurement, an improved planar pattern-based calibration method and a globally optimal relative pose estimation algorithm are proposed to calibrate the intrinsic and extrinsic parameters of the stereo-DIC system separately. In particular, a novel refractive 3D reconstruction method for underwater objects is presented to recover the true 3D shape according to flat refraction geometry, ensuring the correctness and reliability of the measured 3D displacement fields. Several experiments demonstrated that the proposed stereo-DIC system and methods are feasible and accurate. Based on this, the measured dynamic displacement fields of a propeller blade are presented and discussed. Results herald a possibility for monitoring the full-field 3D dynamic response and structural health of underwater rotating structures by the proposed technique.

Effect of span range of variable-camber inlet guide vane in an axial compressor

Inlet guide vanes (IGVs) affect compressor performance by characterizing the upstream flow of the rotor blade row. After operating a long period, the IGV may suffer from blade deformation and consequently influence the downstream flow fields. The deformation of IGV always occurs locally, and the deformed structure can be regarded as a partially-flapped variable-camber IGV. In the current study, six typical configurations, with different span ranges of variable-camber IGVs, were selected. The impact on the compressor performance was discussed through numerical simulations. The dynamic mode decomposition (DMD) approach was applied over the computational domain for investigating the dynamic features. Results show that the stall margin and the total pressure rise of the compressor rotor are sensitive to the span range of the variable-camber IGV. For the unsteady feature in the flow field, the variation of IGV has a limited effect on the IGV itself while significantly changes the dynamic characteristics over the rotor domain. Compared to the case with conservative non-variable IGV, the extension in the flapped span yields a stall margin ranging from −4.1% to 8.1% as well as a monotone drop in the total pressure ratio. The mechanism behind the effect of IGV on the stall margin and the total pressure rise is dependent on the particular range of the modified IGV span.

Deformation and wake of a flexible rotor in water

In this paper, we study experimentally the fluid-structure interaction of a simplified small-scale rotor operating in a water channel. The rotor consists of a single untwisted rectangular blade and is tested with various pitch angles at different rotation speeds and free stream velocities. Flapwise blade deformations are measured using image processing, and flow fields are obtained by Particle Image Velocimetry. The blade exhibits extreme downstream and upstream bending at high negative and positive pitch angles, respectively. In addition, for negative pitch angles, unsteady flapwise fluctuations are observed, accompanied by large-scale recirculation zones. These zones are formed and shed periodically behind the rotor, resembling the dynamics of the Vortex Ring State known for helicopters in steep descent. The induced axial velocity near the blade tip changes direction from upstream to downstream, in accordance with the bending direction, reaching values that exceed twice the free-stream velocity in extreme bending conditions. The blade deformation has a strong dependence on the tip speed ratio for low pitch angles, and a more pronounced dependence on the tip Reynolds number for high pitch angles. Results for a two-bladed rotor are also shown and compared to the behaviour observed for a single blade.

Research on Multiobjective Optimization of Bulb Tubular Turbine Based on Orthogonal Test

The bulb tubular unit has advantages over other units in the low head, large discharge, and tidal energy. The development and utilization of low head and ultralow head hydraulic resources can increase the runner’s energy parameters, make up for the defects of large size and low speed of the unit, and reduce the construction investment. The bulb tubular turbine’s operation stability and structural strength are compared and analyzed by the orthogonal test method to improve the perfomance of bulb tubular turbine. The results show that the optimal design scheme can be obtained when the number of guide vane is 16, the distance between the guide vane and the blade is 1995 mm, the hub ratio is 0.31, the relative twist angle of the blade is 27°, and the cascade density is 0.72. After optimization, the bulb tubular turbine’s efficiency and output are increased by 5.72% and 2.86% at a low flow rate, respectively. The vortex at the tailpipe is reduced, and the blade work effect and the cavitation performance are well. The maximum pressure pulsation amplitude in the flow passage is reduced by 73.15%, the maximum blade deformation is reduced by 39.59%, and the maximum blade static stress is reduced by 13.16%. Finally, the reliability of numerical simulation results is verified by the model test.

Dynamic analysis of a helicopter blade subjected to the aerodynamic loads based on Euler-Bernoulli beam theory

ABSTRACT In this paper, based on Euler-Bernoulli beam theory, the vibration of a helicopter blade is studied. In this regard, the partial differential equation of motion is obtained and solved for a clamped beam numerically. The aerodynamic forces are introduced in terms of the pilot parameters included the collective pitch, lateral cyclic, longitudinal cyclic, and built-in twist on the blade deformation. Moreover, the effects of the blade rotational angular velocity, flight altitude, the blade length, and induce velocity on the blade deflection are studied. The results show that the blade deformation will be oscillating in terms of time and it is very sensitive to the control parameters, its geometry, and the environmental conditions. Moreover, it is observed that the pilot coefficients have more effect on the blade deformation in comparison with other parameters.