Variable Blade Research Articles

Contributions to the synthesis of the windshield wiper mechanism with one rocker-slider blade

The paper deals with synthesis of the windshield wiper mechanism with one rocker-slider blade. Starting from the kinematic scheme of the constructive model designed by Mercedes-Benz motor vehicle company, a structure analysis on this complex mechanism consisting of three kinematic chains, of which two are articulated bar mechanisms and one is planetary mechanism, has been accomplished. The novelty of this paper consists in the presentation of an optimum synthesis method of the planar bar mechanism in two variants for the wiper blade driving. The first variant is a planar 4-bar mechanism type crank-rocker where the cosines theorem has been applied in order to obtain the lengths of the coupler and the crank. The second analyzed variant is a bi-contour linkage consisting of two 4-bar mechanisms linked in series. Further, the calculation of the planetary gear angular velocity on the complex mechanism with dyadic kinematic chains has been achieved. In order to do this, the immobilization of the planetary carrier method has been applied. Finally, the geometry of the driven linkage of the wiper mechanism type crank-slider which has two mobilities has been studied. A vector equation has been written in order to obtain the length of the variable blade.

Flow analysis and sensitivity study of vertical-axis wind turbine under variable pitching

The general frame of the present study falls under the umbrella of ongoing research and innovation in wind energy technology to improve the efficiency and reliability of vertical-axis wind turbines (VAWTs) in terms of design and control. While blade pitching is foreseen as a solution to minimize boundary layer separation and maximize the lift force during the entire cyclic blade operation (effectively enhancing the performances of VAWTs), conclusive research on active blade pitching mechanisms in low wind speed regions is limited because of the 3D complex aerodynamic around VAWT blades. The paper reports a holistic study on active blade pitching solutions to enhance the performance of H-rotor Darrieus VAWTs for different turbine design parameters, i.e., geometrical (different number and airfoil thickness, and solidity) under several operational conditions (Reynolds number (Re), and tip speed ratio (TSR)). In this study, a variable blade pitching technique, adapted for periodic variation of the angle of attack, is incorporated in a high-fidelity two-dimensional VAWTs transient Computational Fluid Dynamics (CFD) model to eliminate the dead band of small-scale wind turbines operating at low wind speed regions and increase the performance coefficient Cp at different TSRs. Sliding mesh and remeshing to capture the blade pitching are used to manage the rotor rotation. The CFD model is validated against experimental data from the literature. The results indicate that the local widening of the angle of attack (AoA) for each NACA0015 airfoil produces a Cp of 0.44, which represents 81% enhancement in the Cp at TSR of 1.5. Moreover, the study shows that increasing the number of blades or extending the blade chord length can eliminate the dead band of wind turbines. Furthermore, the maximum possible torque for 3- and 4-bladed rotor designs is achieved using the variable pitching mechanism.

Vibration characteristics and strength analysis of two-stage variable-pitch axial-flow fan based on fluid-solid coupling method

The adjustment of the rotor blade installation angle of the two-stage variable-pitch axial-flow fan affects the surface pressure characteristics, which in turn affects the vibration characteristics of the rotor blade. In this paper, the finite element model of two-stage variable-pitch axial-flow fan is first established, and then the modal analysis of blades with aerodynamic and centrifugal loads is presented. The resonance of the blade is analyzed based on the pressure pulsation frequency domain characteristics. Finally, the equivalent stress distribution under variable blade installation angles is explored. Simulation results regarding the natural frequency show that the installation angle of the moving blade has a minimal impact on the natural frequency. In contrast, the centrifugal force load significantly affects the natural frequency of the moving blade. To ensure safety, we maintain a frequency margin of over 24 % to avoid the risk of resonance. Strength analysis results indicate that the maximum equivalent stress on the first-stage and second-stage rotor blades decreases by 43.14 MPa and 45.28 MPa, respectively. This reduction is attributed to a certain centrifugal load and a slight offset in aerodynamic loading. This research can provide guidance for the vibration control and safety research of two-stage variable-pitch axial-flow fan.

Variable Blade Inertia in State-of-the-Art Wind Turbine Structural-Dynamics Models

This paper presents a comparison of two methods to represent variable blade inertia in two codes for aero-servo-elastic simulations of wind turbines: the nonlinear aeroelastic multi-body model HAWC2 and the nonlinear geometrically exact beam model BeamDyn for OpenFAST. The main goal is to enable these tools to simulate the dynamic behavior of a wind turbine with variable blade inertia. However, current state-of-the-art load simulation tools for wind turbines cannot simulate variable blade inertia, so the source code of these tools must be modified. The validity of the modified codes is proven based on a simple beam model. The validation shows very good agreement between the modified codes of HAWC2, BeamDyn and an analytical calculation. The add-on of variable blade inertias is applied to reduce the mechanical loads of a 5-megawatt reference wind turbine with an integrated hydraulic-pneumatic flywheel in its rotor blades.

A Modular Modeling Method of Mistuned Blisk Based on State-Space Theory with Fitting Aerodynamic Excitation

In order to improve the solution efficiency of vibration characteristics for the mistuned blisk, a modular method combined with state-space method based on lumped-parametric model is developed for the first attempt, which provides a general modeling framework which can be employed to conveniently construct the lumped-parametric models of bladed disk systems with multiple mistuning and variable blade number. It is noteworthy that a pressure fit in the axial-span-pressure space is performed to obtain the continuous equations of aerodynamic forces according to the aerodynamic loads acting on the blade surface. The function of traveling wake excitation is established by considering the rotational velocity. Subsequently, 1N-degree-of-freedom (1N-DOF) and 2N-DOF lumped-parametirc models are respectively used to construct the mistuned blisk. A modular solution method of multiple mistuned lumped-parametirc model is derived from the controllable canonical form and minimum realisation, which reveals that the minimum dimension of the state space is two times of its DOF. The correctness of the present method is varified by several comparisions. Vibration localization is found in the transient response and steady-state response of the blisk. The effects of the mistuning on the blades and the disk are discussed, respectively.

The Role of Endwall Shape Optimization in the Design of Supersonic Turbines for Rotating Detonation Engines

Abstract Rotating detonation engines (RDEs) are characterized by a thermodynamic cycle with an efficiency gain up to 15% at medium pressure ratios with respect to systems based on the conventional Joule–Bryton cycle. Multiple turbine designs can be considered, and this article deals with the supersonic inlet configuration. After having reviewed the main design steps of an exemplary RDE supersonic turbine, the article focuses on the considerable effects that endwall losses have on the performance of supersonic-inlet turbines and on the reasons why endwall contouring is strongly recommended for an efficient design. Parametric analyses, carried out by a novel in-house mean-line code validated against computational fluid dynamics (CFD), reveal that endwall friction losses contribute significantly to the overall stage loss. Endwall boundary layers also reduce the effective area, which can be critical for the self-starting capability of the supersonic channel. Therefore, a variable blade height geometry is necessary to extend the design space and guarantee a higher efficiency with respect to a constant-span configuration. The in-house CFD-based evolutionary shape optimization code was adapted to search for the optimal endwall shape for these unconventional machines. The optimal shape reduces shock losses and deviation angles and provides a significant gain in efficiency and work extraction. Finally, a novel technique is proposed to design the three-dimensional shape of the rotor based on the method of characteristics and tailored on the flow delivered by the stator.

Learning radar cross section of an intermeshing-rotor helicopter with blade pitch

PurposeThis study aims to study the radar cross-section (RCS) of an intermeshing rotor with blade pitch.Design/methodology/approachThe variation of rotor blade pitch is designed into three modes: fixed mode, linear mode and smooth mode. The dynamic process of two crossed rotors is simulated, where the instantaneous RCS is calculated by physical optics and physical theory of diffraction.FindingsIncreasing the pitch angle in the fixed mode can reduce the average RCS of rotor at the given head azimuth. The RCS curve of helicopter in linear mode and smooth mode will have a large peak in the side direction at the given moment. Although the blade pitch in smooth mode is generally larger than that in fixed mode, the smooth mode is conducive to reducing the peak and mean value of helicopter RCS at the given heading azimuth.Originality/valueThe calculation method for analyzing RCS of intermeshing rotor with variable blade pitch is established.

Flow-Field Prediction in Periodic Domains Using a Convolution Neural Network with Hypernetwork Parametrization

This paper deals with flow field prediction in a blade cascade using the convolution neural network. The convolutional neural network (CNN) predicts density, pressure and velocity fields based on the given geometry. The blade cascade is modeled as a single interblade channel with periodic boundary conditions. In this paper, an algorithm that enforces periodic boundary conditions onto the CNN is presented. The main target of this study is to parametrize the CNN model depending on the Reynolds number. A new parametrization approach based on a so-called hypernetwork is employed for this purpose. The idea of this approach is that when the Reynolds number is modified, the hypernetwork modifies the weights of the CNN in such a way that it produces flow fields corresponding to that particular Reynolds number. The concept of the hypernetwork-based parametrization is tested on the problem of a compressible fluid flow through a blade cascade with variable blade profiles and Reynolds numbers.

Energy efficiency analysis of double suction centrifugal pumps with new impeller geometry

The development of energy saving determines the importance of improving the efficiency of equipment that uses most of the energy consumed. Pumping equipment is one of the most significant consumers of electrical energy. Thus, the drive of pumps (mainly centrifugal pumps) at some CHPPs consumes up to 10 % of the total energy produced at the plant [1]. In general, the total share of consumption of pumping equipment operated in industry, according to various estimates, is from 15 to 25 % of all generated electricity. In this paper, a new impeller configuration (with variable blade curvature) for double suction centrifugal pumps with higher efficiency was proposed. The head and efficiency of centrifugal pump with different vane grids were compared. The main conclusions are that the static pressure and relative velocity have increased in the modernised impeller, leading to an increase in hydraulic and overall efficiency, the kinetic energy of turbulence has less pulsation. the operating point of the pump has shifted. In spite of the fact that the average integral efficiency has increased in the modified pump, the operating point of the pump is shifted to the side of decreasing flow by 1.5%. The theory of the variable curvature vane system was verified by computational methods.

Development of a Distributor Disc for Mineral Fertilizers With Variable Application Rate

Most of the cultivated fields in Russia are acknowledged to have irregular contours, therefore mineral fertilizers are applied irrationally at the field boundaries. To eliminate this problem, the manufacturers of solid mineral fertilizer spreaders offer several technological solutions: in most cases, the application area is limited by changing the granule flight path. (Research purpose) To develop a distributor disc for a variable application area to use in mineral fertilizer spreaders equipped with variable rate application systems. (Materials and methods) The trajectory for applying mineral fertilizer granules was estimated depending on the bend angle of the distributor disk blade. We designed 3D disk models with a variable blade bend angle from 0 to 25 degrees, which were uploaded into the RealFlow program for the subsequent simulation of solid mineral fertilizer distribution. (Results and discussion) The coordinates were obtained for mineral fertilizer granules that dropped from the disk and landed on the surface. We built graphs of the mineral fertilizer distribution on the field surface. It was found out that changing the bend angle of the distributor disc blade within a 20-degree range makes it possible to vary the granule flight path within 10 meters of width and 8 meters of length, respectively. We developed a design of a mineral fertilizer distributor disk with an adjustable application rate. (Conclusions) A disk design was proposed for a smooth change in the blade bend angle within up to 25 degrees, which will allow the use of this system in conjunction with automated rate application systems, improve the distribution accuracy of solid mineral fertilizers and ameliorants in the boundary, edge and wedge-shaped sections of fields.

Experimental characterization of a small wind turbine with variable blades angle

Small wind turbines with fixed blades present a significant disadvantage when operating at low wind speeds. Wind speed increase proportionally with the height to the ground and such wind turbines are installed at most on rooftops, so they face low wind speeds < 10 m/s. This work shows the experimental characterization of a wind turbine prototype with three flat blades and variable orientation angle, to measure the least wind velocity that drives the turbine from the rest. Experimental tests were carried out in a wind tunnel defining two essential points of interest: first, the angle at which it is possible to start the movement of the turbine with the minimum energy; second, the angle that captures the most power from the wind, based on a constant energy input (wind velocity constant).

Numerical simulation of aerodynamic noise for the two-stage adjustable-blade axial-flow fan

In this paper, a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy. The pressure distribution and sound power-level distribution characteristics of the blade surface are explored with variable blade installation angles. Based on the Q-criterion, the study reveals the spatial distribution of the channel and trailing-edge shedding and channel vortexes in the flow field. Then, the evolution laws of the fan's aerodynamic noise sound pressure level are also investigated, and its frequency domain characteristics with variable blade installation angles are obtained. The results show that when the rotor blade installation angle is −5°, the front-guide vane matches the installation angle of the first-stage impeller. The upper limit of sound power level is the smallest with variable blade installation angles, which is 123.56 dB. Meanwhile, the number and size of vortex structures in the front-guide vane area are the smallest, and the turbulent flow in the flow field is moderate. As the moving blade installation angle is deflected from −10° to 10°, the total sound pressure level of aerodynamic noise at each component of the fan first decreases and then increases. The minimum value is 121.40 and 128.40 dB at the inlet and outlet when the blade installation angle is −5°. In addition, the number of eddies periodically shed in the fan flow field is the least. This research can supply technical support for the noise reduction of the two-stage adjustable blade axial fan.

매개변수를 도입한 축류형 송풍기 최적설계 및 데이터 분석 프로세스 구축

Axial fans are important rotating machines in various fluid mechanical systems. Recently, the requirements of axial fans have become more stringent due to the sophisticated demands of fluid mechanical systems. If the boundary dimensions of an axial fan were changed to satisfy a set of requirements, the entire fluid mechanical system would be redesigned and would likely be costly. Accordingly, the development of axial fans that fulfill requirements without any change to their boundary dimensions has increased. However, depending on the expertise of the engineer and through the process of trial and error, adequate designs were made that met target requirements. Therefore, in this study, an optimal design was performed for an axial fan with variable blades. To shorten the design time, the analysis software FanDAS and PIDO software PIAnO were connected to automate the analysis procedure, and the optimization technique was used to perform the optimal design and analyze the design problem. Total Efficiency was selected as the objective function, and 11 constraints related to total pressure, number of rotor/stator blades, variable blades, and solidity were applied. hub to tip ratio, rotor chord length, number of rotor blades, rotor setting angle, rotor camber angle, stator chord length, and number of stator blades were selected as design variables. In particular, in the case of setting angle and camber angle, parameters were introduced so that the value decreases from the Hub position to the Tip position. Optimization results revealed that the objective function was improved while satisfying all design constraints.

Mathematical Modeling of Transient Processes in the Susceptible Motion Transmission in a Ship Propulsion System Containing a Shaft Synchronous Generator

Within the scope of the presented work, a mathematical model of a prototype of a complex motion transmission on a ship was developed. The abovementioned motion transmission includes long elastic elements with distributed mechanical parameters. The system, containing the motion transmission under consideration, is driven by an engine via epicyclic gearing. The torque is transmitted via a long drive shaft to a propeller working with a variable blade geometry. The rotor of a synchronous generator is mounted on the ship’s long drive shaft. This shaft generator produces electricity that is fed to the ship’s electrical network. With the use of the developed mathematical model, electromechanical transients occurring during the transmission of mechanical power are analyzed. This paper analyzes the motion transmission with the use of computer simulation and presents the results of research.

Flutter Suppression of Wind Turbine Blade Based on RBF Neural Network Compensation Backstepping Control

Aiming at the critical flutter problem of wind turbine blades, which is between classical flutter and stall flutter, a flutter suppression scheme based on radial basis function (RBF) neural network friction compensation backstepping is presented. The structure model is based on the typical 2D section of bending and twist model of spring-mass-damper, and the rotor variable exciter second-order model with friction disturbance is incorporated to control the rotor variable blade. A modified quasi - steady - state aerodynamic model was used for aerodynamics actuation. RBF compensation backstepping control scheme is a block-controlled backstepping controller designed based on the stability theorem of Lyapunov function, which approximates the frictional interference with nonlinear characteristics through RBF network, and cancels the friction existing in the actuator of variable rotor. Four wind speed environments were selected to analyze the response of blades under different wind speeds, and the flutter suppression effects under two wind speeds were selected to verify the ability of RBF network to approach the nonlinear function. The results show that the RBF backstepping control scheme can improve the robustness to suppress the critical flutter problem of wind turbine blades.

Способ расчета динамических напряжений в лопатке переменного сечения турбомашины

The problem of assessing the dynamic stresses arising from vibrations of the blades of turbo machines is an urgent and significant problem affecting the overall reliability of the turbo machine. Its solution requires a mathematical study and a physical experiment to determine the intensity of the gas flow impact and the blade reaction.However, there is relatively little information in the scientific publications on this issue. The article considers a semi-empirical method for calculating dynamic stresses at the base of a variable cross-section blade at the first tone resonant vibrations. These vibrations can be considered as the most dangerous because of the maximum amplitude. To perform the calculation a real blade was replaced with a calculated one, composed of separate portions with a constant profile, and the contribution of each part to the stress in the base section was determined. An example of calculating the dynamic stress by the proposed method with a resonant vibration of the first tone of a constant-section blade is given. The calculation showed that the solution to a complex problem can be represented as a sum of solutions to simpler problems. The calculation method can be used in the design of turbine and compressor blades.

Fracture Analysis of high strength bolt in wind turbine

During the operation of a wind turbine in a wind power generation limited liability company, the bolt connecting the blade and the paddle bearing broke. In order to find out the cause of fracture, a comprehensive test analysis was carried out on the connection bolt between the blade and the variable blade bearing by means of macro morphology analysis, chemical composition analysis, mechanical property testing, microstructure testing and fracture micro-area analysis. Experiments show that: the blade and blade bearing joint bolt fracture: was the main cause of the bolt in the operation process of changing, repeated impact of wind load and the effects of the alternating load blade rotation, along the severe stress concentration of thread form ascend a crack source and extension in fatigue, until the whole fracture failure.

Control of a Variable Blade Pitch Wind Turbine Subject to Gust Wind and Actuators Saturation

This paper examines the dynamics and control of a variable blade pitch wind turbine during extreme gust wind and subject to actuators saturation. The mathematical model of the wind turbine is derived using the Lagrange dynamics. The controller is formulated using the Takagi–Sugeno fuzzy model and utilizes the parallel distributor compensator to obtain the feedback control gain. The controller’s objective is to obtain the generator electromagnetic torque and the blade pitch angle to attenuate the external disturbances. The (T–S) fuzzy controller with disturbances rejection properties is developed using the linear matrix inequalities technic and solved as an optimization problem. The efficacy of the proposed (T–S) fuzzy controller is illustrated via numerical simulations.

Implementation of Variable Blade Inertia in OpenFAST to Integrate a Flywheel System in the Rotor of a Wind Turbine

In this paper, the integration of the dynamic behavior of the flywheel system into the load simulation tool OpenFAST is presented. The flywheel system enables a wind turbine to vary the inertia of its rotor blades to control the power production and, most importantly, to affect the vibratory behavior of wind turbine components. Consequently, in order to simulate the behavior of a wind turbine with a flywheel system in its rotor, the variable blade characteristics need to be considered in the load simulation tool. Currently, computer-aided engineering tools for simulating the mechanical loads of wind turbines are not designed to simulate variable blade inertia. Hence, the goal of this paper is to explain how variable inertias of rotor blades are implanted in such load simulation tools as OpenFAST. OpenFAST is used because of it is free, publicly available, and well documentation. Moreover, OpenFAST is open source, which allows modifications in its source code. This add-on in the load simulation is applied to correct rotor mass imbalance. It can also be applied in many cases related to the change in the inertia of wind turbine rotor blades during its operation as, for example, atmospheric ice accretion on the blades, smart blades, etc.

Dynamic responses of a 10 MW semi-submersible wind turbine at an intermediate water depth: A comprehensive numerical and experimental comparison

A series of experiments and numerical simulations were conducted to investigate the dynamic responses of a 10 MW floating wind turbine concept named SPIC, at an intermediate water depth of approximately 60 m. A fully coupled numerical model was established using the aero-hydro-servo-elastic-moor method. The experimental and numerical dynamic responses under operational conditions, including irregular waves, steady and turbulent winds, and combined wind–wave conditions, generally agree well. The mean values are well predicted, and the powers at motion resonant frequencies, wave frequency and tower vibration frequency are captured. Discrepancies between the numerical and experimental results are further addressed by in-depth numerical analyses. Under turbulent winds, the discrepancies of dynamic responses at 1P and 2P frequencies are induced mainly by individual blade installation error, while the discrepancies at 3P components are caused mainly by the nonuniformity of the wind field. In addition, in the turbulent wind case with variable blade pitch angles and rotor speed control system, the mean tower-base bending moment is smaller, and the low-frequency responses are larger than those in the case with fixed blade pitch angles and a constant rotor speed. The reveal of uncertainties is helpful for further guiding the model test of floating wind turbines.