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The present work was based on an experimental study on the aerodynamic performance of a flapping wing rotor (FWR) and enhancement by passive pitching angle variation (PPAV) associated with powered flapping motion. The PPAV (in this study 10o~50o) was realized by a specially designed sleeve-pin unit as part of a U-shape flapping mechanism. Through experiment and analysis, it was found that the average lift produced by an FWR of PPAV was >100% higher than the baseline model, the same FWR of a constant pitching angle 30o under the same input power. It was also noted that the lift-voltage relationship for the FWR of PPAV was almost linear and the aerodynamic efficiency was also over 100% higher than the baseline FWR when the input voltage was under 6V. The aerodynamic lift or efficiency of the FWR of PPAV can be also increased significantly by reducing the weight of the wings. An FWR model was fabricated and achieved vertical take-off and free flight powered by 9V input voltage. The mechanism of PPAV function provides a feasible solution for aerodynamic improvement of a bio-inspired FWR and potential application to micro-air-vehicles (MAVs).

This study systematically investigates the aerodynamic interactions of a two-rotor system with a front rotor and an aft rotor aligned with the direction of flow. The rotors are 5.5 ftdiameter fixed-pitch rotors operating at approximately 12 lb/ft2 disk loading, representative of large eVTOL aircraft. Fluid flow is simulated using the commercial Navier–Stokes solver, AcuSolve, with a detached eddy simulation (DES) model. Simulations were performed nominally at 40 kt edgewise flight for nine cases corresponding to three values of longitudinal hub–hub separation (2.5R, 3R, 3.5R) and three values of vertical offset (0, 0.25 R, 0.5 R ). Aft rotor performance was compared to an isolated rotor operating in the same conditions in order to quantify the effects of rotor–rotor interaction. For the cases where the aft rotor is closest to the front rotor (2.5R longitudinal offset, zero vertical offset), the aft rotor produced 8.4% less thrust and required 13.4% higher torque than a rotor in isolation. When vertical rotor separation was increased, interactional aerodynamic effects decreased. For a 2.5R longitudinal offset, increasing the vertical offset to 0.5 R decreased the lift deficit to 4.6% and the torque penalty to 6.8%. Increasing the longitudinal offset to 3.5R (while keeping the vertical offset at zero) also reduced interactional aerodynamic effects, but reductions in lift deficit and torque penalty were smaller than those observed with 0.5R vertical offset. Reducing disk loading was found to strengthen interactional aerodynamic effects, with an 11.5% thrust deficit at 6 lb/ft2 compared to 9.0% at 12 lb/ft2. An increase in flight speed also increased interactional aerodynamic penalties from 5.4% thrust deficit at 20 kt to 12.2% at 60 kt. The increased interactional aerodynamic penalties with the reduction in disk loading and increase in flight speed were both attributed to an increase in wake skew angle and the resulting decrease in separation between the aft rotor disk and front rotor wake.

A wave rotor is suitable for compact and efficient pressure-exchange between gas flows. This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves. The experimental and CFD results showed some slopes in the circumferential pressure distributions, and the slopes indicated the traces of specific unsteady pressure waves. Such traces varied regularly if the rotational speed varied within a range from −11% to +11% off the baseline value, but they were seriously disturbed if the rotational speed varied by −45% from the baseline value. It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent, and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent. Because of the pressure wave behaviors, the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.

Rotor-step straight skewing is a common method to reduce electromagnetic vibration of permanent magnet synchronous motors (PMSMs). However, the difference of the radial electromagnetic forces received by different axial positions of the stator caused by the elastic-plastic material is generally ignored in the theoretical analysis to determine the skewing structure, which makes the vibration suppression effect of the structure far less than expected in practical applications. Take a 48-slot 8-pole interior PMSM as an example, this paper compares the suppression effects of rotor-step straight skewing and rotor-step zigzag skewing when the elastoplasticity of the stator material is considered. It is pointed out that the rotor-step zigzag skewing can overcome the limitation of the straight skewing in restraining electromagnetic vibration in practical application. Based on the theoretical formula and multi-physical field simulation, the selection rules of the rotor-step zigzag skewing angle and segment number are summarized. Finally, the rationality and effectiveness of the simulation method are verified by experiments on the prototype.

Aeroelastic simulations of a 2.3 MW wind turbine rotor operating in different complex atmospheric flows are conducted using high fidelity fluid–structure interaction (FSI) simulations. Simpler blade element momentum (BEM) theory based simulations are likewise conducted for comparison, and measurements from field experiments are used for validation of the simulations. Good agreement is seen between simulated and measured forces. It is found that for complex flows, BEM‐based simulations predict similar forces as computational fluid dynamics (CFD)‐based FSI, however with some distinct discrepancies. Firstly, stall is predicted for a large part of the blade using BEM‐based aerodynamics, which are not seen in either FSI simulations or measurements in the case of a high shear. This leads to a more dynamic structural response for BEM‐based simulations than for FSI. For a highly yawed and sheared flow case, the BEM‐based simulations overpredict outboard forces for a significant part of the rotation. This emphasizes the need of validation of BEM‐based simulations through higher fidelity methods, when considering complex flows. Including flexibility in simulations shows only little impact on the considered rotor for both FSI‐ and BEM‐based simulations. In general, the loading of the blades increases slightly, and the rotor wake is almost identical for stiff and flexible FSI simulations.

Multidisciplinary design optimization (MDO) was performed on a helicopter rotor blade. The blade was modeled as a rigid flapping blade for dynamics; Blade Element Theory (BET) was the analysis approach to model the aerodynamic loading, and a simple linearly elastic hollowed rectangular section was the main structural component. MATLAB was used to solve the flapping differential equations and its Sequential Quadratic Programming (SQP) and Genetic Algorithm (GA) were used for the optimization. A Particle Swarm Optimization (PSO) routine was also tested. The optimization process consisted of three cases. The first case was a simple cantilever beam under centrifugal and an assumed bending loads. The optimization was performed using the SQP, GA, and PSO algorithms. The SQP resulted in the superior design with 75.45 compared to the GA's 87.1 and the PSO's 79.2, but a local minimum was present. The second case was an expansion of the first case by turning it into multidisciplinary problem. Aerodynamics was included in the design variables and objective function. Only the SQP algorithm was used and there was a reduction in hub vertical shear by 33.6%. The blade mass increased by 36.84%. The last case was an improvement to the second by creating a multiobjective problem by including the hub radial shear and the results were improved significantly by reducing the hub vertical shear by 34.06% and radial shear by 17.87% with a reduction of blade mass by 23.86%.

In the context of the development of high-speed compound helicopters, the main rotor may not be an efficient propulsive device at high speeds and adding a propulsive propeller is a means to enable higher speed. On such configuration, at low speed, the propellers are in strong interactions with the main rotor wake which affects their performance and aircraft maneuverability. The present work numerically investigates the aerodynamics of the rotor/propeller interaction on rotorcraft similar to the Racer from Airbus Helicopters. Through the comparison of two different levels of fidelity for three different advance ratios, it is shown that at high advance ratio, a simple free wake model is suitable to give most of the interaction effects, while in hover, a full computational fluid dynamics (CFD) unsteady computation is necessary to better capture all the unsteadiness of the interaction. The detailed analysis of CFD results also outlines the different behaviors of the propeller when it is fully inside the rotor wake or out of it, and therefore the need for a precise control of the rotorcraft in the transition between hover to fast forward flight.

Rotorcraft brownout is an in-flight visibility restriction caused by clouds of sand and dust particles during landing, takeoff, and near-ground flight operations in arid desert terrain. This complex phenomenon is caused by the entrainment of dust, sand, and ground particles by rotor downwash and is compounded by fuselage geometry and its orientation with respect to the ground. Highly unsteady wind velocities are common in near-ground operations and play a significant role in the particulate cloud's behavior that creates the brownout condition. Experiments and flight tests to understand brownout are challenging, expensive, and risky. Alternatively, computational fluid dynamics (CFD) has been used extensively over the past few decades to study rotorcraft aerodynamics. However, there are additional computational challenges associated with modeling the dust particle transport in a brownout. In this work, a computationally efficient Eulerian-based framework has been developed to model rotorcraft brownout. The flowfield is modeled by Reynolds averaged Navier–Stokes (RANS) equation and is solved using the SIMPLER algorithm. Turbulence properties are modeled using Realizable κ – ε equations, while the rotor is modeled as a momentum source to focus on the global flowfield rather than the flow near the rotors. The Eulerian approach for both the flowfield and the dust transport allows computationally efficient and rapid analysis, taking an order of few hours in a single CPU to a fraction of an hour using GPU-based computation. In this work, results from two sets of experiments are presented. At first, a study on the fuselage's effect on brownout with respect to height for a single-rotor configuration in hover is demonstrated. Next, a study on the brownout characteristics of three rotor–fuselage configurations in hover, namely single-rotor, tandem-rotor, and quad-rotor, is presented. It has been observed that the ground friction velocity profile and flowfield vorticity around the rotorcraft play a significant role in dust cloud behavior. Additionally, the body forces and interference due to the fuselage plays a vital role in the formation of brownout dust clouds. The experiments showed that the quad-rotor is worst affected in terms of size and height of the dust clouds. However, the tandem-rotor has been found to be worst in the terms of average dust density.

This article presents the optimal design from the electromagnetic and structural point of view of a fault-tolerant modular outer rotor synchronous reluctance machine, a not previously constructed topology. Two new topologies with the rotor in modular construction, one with each pole of the rotor considered as a separate module and a segmented one where each rib of a module can be considered as independent, are compared with a classic structure. The electromagnetic analysis is carried out using FLUX 2D software. The main studied parameters are electromagnetic torque, torque ripple content, saliency ratio, and power factor. In order to optimize the power factor of the machine, a cosimulation procedure is carried out for each structure, by employing a MATLAB and FLUX 2D coupling. Based on the obtained performances, the best topology is selected. Furthermore, a mechanical analysis is performed to determine if the new proposed rotor meets the structural integrity at rated speed and to establish the maximum speed value that can be attained such that the structural failure of the rotor is prevented. A modular outer rotor synchronous reluctance machine is designed and built. Experimental results of testing the prototype are given to confirm the validity of the proposed machine.

Multi wind tUrbine Simulation Tool (MUST) is a new CENER's in-house code, based on NREL's OpenFAST code, designed to allow the aero-hydro-servo-elastic modelling of novel multi-rotor wind turbine concepts. MUST also includes a new aerodynamic module, called AeroVIEW (Aerodynamic Vortex fIlamEnt Wake) based on an implementation of the Free Vortex filament Method (FVM) combined with an unsteady Lifting Line (LL). This model allows to represent the influence existing between all the rotors, in each one of them. In this article, a validation of AeroVIEW performance for single and multi-rotor configurations is presented. First, a study of the wake properties (wake geometry, core radius and circulation of tip vortex filament) obtained with AeroVIEW has been successfully compared with several MexNext III cases. Then, an analysis of the rotor wakes interaction, in different arrays of wind turbines, has been made, obtaining power and thrust increases, due to this rotor-wake interaction, for different conditions. The increases obtained in power are very similar to results of high fidelity tools found in the literature. Moreover, this beneficial effect on the power generated, has a counterpart in the average thrust, whose increase is around half of the power production increase.

In this article, a hybrid analytical model combining the subdomain method and the lumped-parameter magnetic circuit method (LMCM) is presented for the analysis of a high-torque-density spoke-type permanent magnet in-wheel motor considering rotor slot and eccentric magnetic pole. In the proposed model, the air-gap field distribution is derived using the subdomain method, while the saturation and the axial flux leakage of the iron core are considered by LMCM. The rectangular-shaped spoke magnets, eccentric magnetic poles, and rotor slots are approximated by multiple layers of arc-shaped subdomains. The magnetic equivalent circuit (MEC) of the stator and rotor is established, and the nonlinearity of the iron core is taken into account. Based on the developed hybrid analytical model, electromagnetic performance, such as cogging torque, electromagnetic torque, flux linkage, and back electromotive force, are obtained. The analytical results are verified by the finite-element method, and its application in the optimization process is investigated. Finally, a 1800-Nm high-torque prototype machine is manufactured and tested, and the results validate the accuracy and efficiency of the analytical method.

Additional guide vane (GV) to the Savonius rotor is used to overcome the low rotor efficiency. This study is experimentally carried out to know the influence of guide vane in improving two blades Savonius rotor performance. There were four designs of guide vane which are 4, 5, 6 blades and installed at different tilt angles, which were 0°, 20°, 40°, and 60°. The experiment was done under wind speed of 5.9 m/s, 7.0 m/s, 8.1 m/s, 9.3 m/s and 10.4 m/s. The results show that the 6 blades of GV at a 60° tilt angle attained the best Cp, which was 0.0279 at the tip speed ratio of 0.53. The Cp increased up to 40% with six blades of GV. Wind direction identified significantly affected the rotor performance. The rotor performed best on the wind direction of 0° attained Cp of 0.079, but when the wind direction was modified on 30°, the rotor with 6 GV attained Cp of 0.0153 did not perform better than without GV that produced Cp of 0.0166. The guide vanes improve the Savonius rotor performance compared to the rotor without a guide vane. However, the wind direction also needs to be considered no less important factor affecting the Savonius rotor performance.

The ring-speed ratio is a comprehensive dynamic index of floating ring bearing structure and operating parameters, which directly affects the dynamic behavior of the turbocharger rotor system. The cross stiffness of ring-speed ratio and floating ring bearing and the work of oil film force are analyzed. The influence of dynamic ring-speed ratio change on the vibration response of floating ring bearing was studied. The finite element model of the rotor-floating ring bearing system is constructed; its model parameters are verified through the measured critical rotor speed. Newmark integral method is used to analyze the nonlinear transient response. The results show that when the ring-speed ratio is between 0.18 and 0.24, the rotor is in a good operating state; when it increases from 0.24 to 0.36, the rotor vibration is dominated by frequency division, and the system will be less stable. The square of the ring-speed ratio is inversely proportional to the rotational speed of the journal where the subfrequency vibration occurs. It helps to know the nonlinear vibration by judging the journal speed when the rotor vibration occurs in subfrequency. The conclusion provides a reference for the mechanical dynamics design and intelligent management and maintenance of this kind of turbine rotors.

Purpose The purpose of this paper is to study the influence of pivot stiffness on the dynamic characteristics of tilting-pad journal bearings (TPJBs) and the stability of the bearing-rotor system. Design/methodology/approach A theoretical numerical model is established, and the influences of pivot stiffness on TPJBs and a bearing-rotor system are analyzed. Then, two kinds of pivot structures with different stiffness are designed and the vibration characteristics are tested on the vertical rotor bearing test bench. Findings The pivot stiffness has an obvious effect on the dynamic characteristics of the TPJBs and the stability of the bearing-rotor system. As a result of appropriate pivot stiffness, the critical speed and the vibration amplification factor can be reduced, the logarithmic decay rate and the stability of the rotor system can be effectively increased. While the journal whirl orbit is smoother and the rubbing is obviously reduced when the bearings have flexible pivots. Originality/value The influence of pivot stiffness on TPJBs and a vertical rotor-bearing system is studied by theoretical and experimental methods.

Outer-rotor PM synchronous motor (OR-PMSM) with PM flux has shown to generate high torque and power densities. However, the round rotor used provides high iron loss and weight that affect their speed. This paper, addresses the problem using 24-stator and 14-segments flux switching machine (FSM) whose rotor is passive. Initially, performances of the designed motor such as cogging torque, harmonic distortion, average torque and power are analyzed. The initial design is optimized and the performances between initial and optimized OR-PMFSM designs are compared. The result shows OR-PMFSM has provided low cogging torque and low odd harmonic distortion to operate safely. The torque has increased to 48.81% from initial to optimize design of 240.5Nm and 469.8Nm. A comparative analysis of other motors for high torque such as OR-PMSM, OR-HEFSM and OR-FEFSM are presented. The proposed motor is capable to perform in high torque and high power conditions for automotive applications.

Wind is a renewable form of energy that holds vital solutions to energy crisis that will be faced in the possible future. Apart from the viable lift based turbines that we have been working on, research can be done on drag based turbines that can be installed in urban areas for short power requirements. The research aims at developing a novel design for Savonius type rotor which will help to improve the power producing characteristics of the turbine. CFD fluent analysis will help in analysis of the proposed blade shape. The results explain how the combination of elliptical profiled blade improves coefficient of power for Savonius type rotor. Keywords: Aerodynamics, Wind Energy, Savonius, VAWT, Wind Turbine

Purpose The reliability of various mechanisms and machines is determined by the durability of tribo-units, which must ensure operation at high temperatures and an extended range of rotor shaft speeds. The best performance of the bearing assembly is achieved with hydrodynamic lubrication, which depends on optimal operating conditions and temperature conditions. The purpose of this paper is determining the thermal state of the turbocharger (TCR) bearings. Design/methodology/approach The simulation was carried out in the ANSYS Fluent software package. The boundary conditions for the calculation were obtained from experimental data. The experiments were carried out at a specialized stand created at the scientific and production association “Turbotekhnika”. Findings The result of the simulation was the determination of temperatures and thermal fields in the TCR housing. The data obtained testify to the uneven thermal loading of the bearings. When calculating the dynamics of the rotor, transient modes are considered. The results are the trajectories of the rotor in the space of the bearing clearance. The thickness of the lubricating layer was calculated as a parameter that determines the hydrodynamic friction regime. The thermal state of the TCR elements was evaluated at all the considered rotor speeds. The flexible axis of the rotor was obtained at different speeds. Originality/value The paper presents a model of heat transfer in a TCR housing and rotor dynamics, based on numerical methods, which will help in the design of TCRs and journal bearings.

In the present paper, the damage and life cycle of the last-stage blades (LSB) of a 250-MW low-pressure steam turbine are predicted under low-cycle fatigue conditions. A finite element-based analysis is carried out to compute fatigue life and damage for a blade with a fir-tree root region under the loading condition of centrifugal stresses and using eight possible cases of contact between blade fir-tree root region flank and rotor flank. An experimental modal analysis (EMA) is performed for the identical modeled blade with a fir-tree root in a stationary test rig to find resonant frequencies and mode shapes, and these mode shapes show agreement with the experimental data. Dynamic response analysis of cracked and healthy blades for a case is also done. Further, the minimum number of life cycles, fatigue damage, and safety factor are computed employing mean stress correction approaches such as strain-based life, Morrow and Smith Watson Topper (SWT) to initiate a crack in blades for the same. The results for the lowest minimum life and serious damage among all eight blade–rotor fixity conditions are identified at the leading edge of lower serration when the pressure side lower flank is in contact with the rotor.

A small collapsible common-axis dual-rotor drone has been designed independently by performance indicators. The model was computed through three-dimensional modeling and meshing. Using Fluent software, the wind tunnel test simulation of the blades was obtained, and the results of the blade model test were compared with the results of the blade model. The lift data of CFD at different speeds were consistent with the results of the paddle model test, with a maximum error of only 12.46%. Using the mesh Boltzmann method (LBM) based on smooth particle theory, the non-normal aerodynamic strain of the most severe conditions in the flat flight is selected for modeling analysis. The aerodynamic layout design of a type of coaxial twin-rotor aircraft and its nonlinear six-degree-of-freedom flight simulation modeling and control system were verified. The results show that the design of the common-axis twin-rotor aircraft can meet the higher aerodynamic index requirements. The control performance and wind disturbance resistance of the designed aircraft are tested and verified by the flight simulation of Matlab/Simulink, and the simulation results show that the system can achieve the desired control goal by adding the closed-loop altitude controller and speed controller. It also provide a basis for further study of its aerodynamic properties.

This paper focuses on the rotor thermal design of the axial flux permanent magnet synchronous machine (AFPMSM) with housing water-cooling. By adapting the effect of disc rotor self-ventilation, an enhanced cooling method has been innovated to optimize the temperature distribution of the rotor in AFPMSM. Two scenarios will be created to compare their influence on cooling enhancement of rotor with the diverse types of fins, the annular fin and the rectangular fin, each will be installed separately to the internal surface of housing. There is a significant effect by using this method in all types of AFPMSM with housing cooling, especially for multi-rotor ones. The results of CFD show that the effectiveness of annular fins is essentially enhanced, with 25% more heat dissipation achieved.

Purpose This study aims to study the dynamic characteristics of a helical geared rotor-bearing system with composite material rotating shafts. Design/methodology/approach A finite element model of a helical geared rotor-bearing system with composite material rotating shafts is developed, in which the rotating shafts of the system are composed of composite material and modeled as Timoshenko beam; a rigid mass is used to represent the gear and their gyroscopic effect is taken into account; bearings are modeled as linear spring-damper; and the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, mode description, lateral responses, axial responses, lamination angles, lamination numbers, gear mesh stiffness and bearing damping coefficients are investigated. Findings The desired mechanical properties could be constructed using different lamination numbers and fiber included angles by composite rotating shafts. The frequency of the lateral module decreases as the included angle of the fibers and the principal shaft of the composite material rotating shaft increase. Because of the gear mesh stiffness increase, the resonance frequency of the coupling module of the system decreases, the lateral module is not influenced and the steady-state response decreases. The amplitude of the steady-state lateral and axial responses gradually decreases as the bearing damping coefficient increases. Practical implications The model of a helical geared rotor-bearing system with composite material rotating shafts is established in this paper. The dynamic characteristics of a helical geared rotor-bearing system with composite rotating shafts are investigated. The numerical results of this study can be used as a reference for subsequent personnel research. Originality/value The dynamic characteristics of the geared rotor-bearing system had been reported in some literature. However, the dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts is still rarely investigated. This paper shows some novel results of lateral and axial response results obtained by different lamination angles and different lamination numbers. In the future, it makes valuable contributions for further development of dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts.

In the present study, numerical simulations of the pressure-sensitive paint (PSP) rotor in hover were conducted using a Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) flow solver based on unstructured mixed meshes. In the simulations, an improved laminar-turbulent transition model $$\gamma - {\text{Re}}_{{\vartheta t}} - {\text{CF}}^{ + }$$ was adopted for the prediction of laminar-turbulent onset phenomena involving crossflow-induced transition and flow separation. To capture vortices with high resolution, an improved scheme ESWENO-P was utilized for computing inviscid fluxes on Cartesian meshes. The predicted results such as transition onset locations and rotor aerodynamic performances in terms of thrust coefficient, torque coefficient, and figure of merit were compared with the experimental data. The effects of the fuselage and facility wall on PSP rotor performance in hover were also investigated.

Floating ring bearings have been widely used, over the last decades, in rotors of automotive turbochargers because of their improved damping behavior and their good emergency-operating capabilities. They also offer a cost-effective design and have good assembly properties. Nevertheless, rotors with floating ring bearings show vibration effects of nonlinear nature induced by self-excited oscillations originating from the bearing oil films (oil whirl/whip phenomena) and may exhibit various nonlinear vibration effects which may cause damage to the rotor. In order to investigate these dynamic phenomena, this paper has developed a nonlinear model of a perfectly balanced rigid rotor supported by two identical floating ring bearings with consideration of their vibration behavior mainly governed by fluid dynamics. The dimensionless hydrodynamic forces of floating ring bearings have been derived based on the short bearing theory and the half Sommerfeld solution. Using the numerical continuation approach, different bifurcations are detected when a control parameter, the journal speed, is varied. Depending on the system’s physical parameters, the rotor can show stable or unstable limit cycles which themselves may collapse beyond a certain rotor speed to exhibit a fold bifurcation. Bifurcation analysis is performed to investigate the occurring instabilities and nonlinear phenomena. Such results explain the instabilities characteristics of the floating ring bearing in high-speed applications. It has also been found that the selection of the bearing modulus plays an important role in the characterization of the rotor stability threshold speed and bifurcation sequences. An understanding of the system’s nonlinear behavior serves as the basis for new and rational criteria for the design and the safe operation of rotating machines.

Brush cutters are used in forestry for the care of forest plantations in operations for cutting unwanted tree and shrub vegetation (TSV). Rotors can be used as working bodies. The rotor we are considering is a flywheel, on the outer sides of which the blades are hinged. When cutting DKR with blades, a cutting moment arises, which is transmitted through the knife to the axis of its rotation and then to the shaft driving the flywheel. When designing a brush cutter structure, the impact from the cutting forces of the DKR is decisive for the choice of drive power and rotor parameters. We designed the brush cutter rotor in CAD Solidworks to study the cutting process of the DKR. Its geometric and mass parameters were set; the kinematic links of the links were established. The input motion characteristics were set in the Motion Solidworks module and the cutting moment was applied to the knives. Virtual sensors were installed on the model to record movement characteristics. As a result of a computer experiment for three options, which differ in cutting force and the presence of a damper, the trajectories of the knives and the power consumption of the drive were established

This article focuses on the study and analysis of the importance of interconnections between electricity systems, which increases with greater probability due to the dependence of all countries and States on electricity and the ease of its transfer between countries in order to supplement their economic and technical benefits. THE PURPOSE. This study analyzes the dynamic impact of interconnection on circuit stability for synchronous generators in Syrian power grids. In addition, the authors of the article analyzed the dynamic effect of interaction on the stability of the angle of rotation of the rotor of synchronous generators operated in the Syrian power system through the use of dynamic modeling of the country's power system. METHODS. In the course of the study, the authors used a technique based on the dynamic representation of the power system and the construction of its nonlinear equations, followed by the use of the PSS ® E program. 230-400 kV.RESULTS. The authors of the article obtained a solution and determination of the system parameters and the separation time of the boundaries of three-phase short circuits in a 400 kV network in addition to determining the angular position of the generator circuits, and thus, its stability was checked, regardless of whether it works independently in the electric power system of Syria or is part of a network. CONCLUSION. In the course of the study, the authors obtained the following conclusions, such as: an increase in CFCT was found for generating units in the power system of Syria due to connection activation, an increase in transmitted power, which leads to an increase in the stabilization zone after a failure and before the start of connecting electrical systems to the country's power system, as well as it is necessary to conduct in-depth dynamic studies of the entire system in order to represent the effect of the connection on the parameters of the system, taking into account the increase in power.

Optimization methods in conjunction with computational fluid dynamics are a key tool in advancing current rotor design. High-fidelity optimization of unsteady rotor flows in forward flight, however...

Optical trap, a circularly polarized laser beam can levitate and control the rotation of microspheres in liquid medium with high stiffness. Trapping force performs as confinement while the trapped particle can be analog to a liquid floated gyroscope with three degree-of-freedom. In this work, we analyzed the feasibility of applying optically levitated rotor in the system. We presented the dynamic analysis and simulation of an ellipsoid micron particle. The precession motion and nutation motion of a rotating ellipsoid probe particle in optical tweezers were performed. We also analyzed the attitude changes of an optically levitated ellipsoid when there was variation of the external torque caused by deviation of the incident light that was provided. Furthermore, the trail path of the rotational axis vertex and the stabilization process of a particle of different ellipticities were simulated. We compared the movement tendencies of particles of different shapes and analyzed the selection criteria of ellipsoid rotor. These analytical formulae and simulation results are applicable to the analysis of the rotational motion of particles in optical tweezers, especially to the future research of the gyroscope effect.

The objective of this article is to propose the concept of and evaluate the potential performance of an integrated flux-switching permanent magnet (FSPM) motor–compressor that has rotor poles designed as airfoils to perform compression functions. The airfoil-shaped rotor functions as the rotor of both an electric motor and an axial-flow compressor. As a result, the integrated motor–compressor increases the compressor system compactness by eliminating the separation between the motor and compressor. In this article, the electromagnetic and thermodynamic designs are developed using sizing equations and mean line analysis. Four design configurations of the integrated motor–compressor are carried out and evaluated, including the continuous-skewed versus step-skewed structure and laminated steels versus soft magnetic composite (SMC) materials. The thermodynamic performance is calculated by mean line analysis and computational fluid dynamics (CFD). The electromagnetic performance and structural analysis are evaluated by finite element analysis (FEA). The comparisons of the integrated motor–compressor with conventional motor-driven compressors are conducted. Results from FEA and CFD verify the integrated motor–compressor.

With the present advancement, a wind turbine needs a wind rotor with high torque and power. The present study aims to enhance the torque and power of wind turbine by employing the ducted dual rotor. In this regard, CFD analysis is performed to analyze the torque and power produced for horizontal axis single rotor bare wind turbine, dual rotor wind turbine, and convergent-divergent ducted type dual rotor wind turbine. The comparative study is conducted to enhance the power and torque for the aforementioned rotor type. The results highlight the maximum value of torque for a dual ducted wind turbine is 36.9% more than a dual rotor at 16 m/s of wind velocity and 92.2 % more than a single rotor at 16 m/s of wind velocity, and the maximum value of the power produced for a dual ducted wind turbine is 40.48% more than a dual rotor at 16 m/s of wind velocity and 139.66% more than a single rotor at 16 m/s of wind velocity. Therefore result suggested that a dual ducted wind turbine is better than a single rotor wind turbine.

Numerical and experimental analyses regarding the dynamic behavior of an onboard rotor are presented in this work. Aircraft engines, rotating machines placed in offshore petroleum boards, automotive engines, helicopter rotors, and offshore wind turbines are typical examples of onboard rotating machines. Therefore, in the present contribution, a finite element method is used to formulate the differential equations of motion associated with the considered onboard rotor system. The model is based on the kinetic and strain energies of the shaft, kinetic energy of the discs and mass unbalance, and the virtual work associated with the external forces, as well as the stiffness and damping coefficients of the bearings. A rotating machine composed of a flexible horizontal shaft, one rigid disc, and supported by two self-alignment ball bearings is studied. The numerical and experimental vibration responses of the rotor subjected to impulse and sinusoidal base excitations are compared. Different analyses are performed both in the time and frequency domains. The obtained results demonstrated that the model is capable of capturing the dynamic behavior of the onboard rotor satisfactorily.

This paper focuses on aeroelastic prediction and analysis for a transonic fan rotor with only its “hot” (running) blade shape available, which is often the case in practical engineering such as in the design stage. Based on an in-house and well-validated CFD solver and a hybrid structural finite element modeling/modal approach, three main aspects are considered with special emphasis on dealing with the “hot” blade shape. First, static aeroelastic analysis is presented for shape transformation between “cold” (manufacturing) and “hot” blades, and influence of the dynamic variation of “hot” shape on evaluated aerodynamic performance is investigated. Second, implementation of the energy method for flutter prediction is given and both a regularly used fixed “hot” shape and a variable “hot” shape are considered. Through comparison, influence of the dynamic variation of “hot” shape on evaluated aeroelastic stability is also investigated. Third, another common way to predict flutter, time-domain method, is used for the same concerned case, from which the predicted flutter characteristics are compared with those from the energy method. A well-publicized axial-flow transonic fan rotor, Rotor 67, is selected as a typical example, and the corresponding numerical results and discussions are presented in detail.

The deep-bar rotor induction motor is one of the most popular motors in the high starting-torque group of three-phase squirrel-cage induction motors. This motor is commonly fitted with deep-bars, of the wedge-form, on the rotor-side. Optimising the dimensions of these bars is a tedious work, especially when the motor is required to exert a strting-torque which exceeds the normal range. This paper presents a computer aided design of the wedge-type rotor-bar to fulfill this requirement. The design concept, relating the bar-dimensions to the basic group of the motor specifications, is given by taking into consideration the skin -effect just at starting. The iterative method employed to obtain the proper cross-section area of the conductor , as well as the method of checking the preliminary dimensions, are also explained in this paper. The design process is written in form of a digital program which gives for a given output power, the proper bar-dimensions for an extended range of starting-torque ratios. The results show that for a given output power, a starting-torque ratio higher than usual can be obtained on the expense of a little increase in the starting-current ratio.

The bolted flange joints with spigot (short for bolted joints) are widely used in the rotor system of aero-engine. The current models of the bolted joint usually ignore the spigot, therefore cannot account for the effect of spigot on joint's mechanical characteristics. In this paper, a new analytical model of bolted joint is proposed to describe its nonlinearity under bending moment. The model takes into account the sticking and sliding statuses of spigot by introducing a Jenkins element, therefore is able to describe the joint's damping effectively. By performing a comparison study with the finite contact element model, the accuracy of the proposed model is validated. Meantime, the comparison study highlights the important role of spigot on the hysteresis nonlinearity of the bolted joint. After that, a dynamical model of the bolted rotor is developed, in which the proposed bolted joint model is introduced by considering the influence of rotor's whirl motion. Based on the dynamical model, the dynamic characteristics of the bolted rotor are investigated in detail. The results show that the bolted joint mainly produces stiffness loss and damping nonlinearity into the rotor system. The stiffness loss occurs in any loading conditions and leads to a decrease of the rotor's critical speed. While the damping nonlinearity is mainly excited under large unbalance, it may induce a self-excited components in rotor's response at super-critical speed. The influence of the bolted joint on rotor dynamics can be reduced by decreasing flange length, friction coefficient and interference fit of the spigot.

The use of finite-state methods is critical to the development of accurate and efficient inflow models used in rotorcraft flight dynamics simulation and control. Recent work in the finite-state fie...

Harvesting the pervasive ultralow-frequency (

This work aims to study the nonlinear dynamic analysis response of the external excitation forces of an on-board rotor with a mobile non-deformable supports, mounted on hydrodynamic bearings. The m...

A mathematical model for predicting the performance of solar energy assisted hybrid air conditioning system (SEAHACS) is presented. The honeycombed silica gel desiccant wheel was used in this study, one-rotor six-stage rotary desiccant cooling system, in which two-stage dehumidification process, two –stage pre-cooling process and two-stage regeneration process are realized by only one wheel. Three air streams are involved in the present system. The mathematical model has been validated with the experimental data. As the key operating and design parameters, the range of regeneration air inlet temperature from 65-140 oC, area ratio of process air to generation air change from 1-3.57, regeneration air inlet velocity from 1.5-5.5 m/s have been examined for a range of rotation speed from 6-20 rev/h. the optimization of this parameters is conducted based on the moisture removal capacity D, relative moisture removal capacity, dehumidification coefficient of performance and thermal coefficient of performance. At last, the influences of these main parameters on optimal rotation speed are discussed

Rotating machinery (RM) fault diagnosis based on artificial intelligence (AI) is an esteemed industrial IoT application and an inevitable constituent of the Industry 4.0 revolution. Notably, the existing research in this area exhibits the following limitations: i) the time-series characterization or system dynamics considerations of vibration input are not strictly followed in the diagnostic procedure, ii) fault-specific component usage is not encouraged in existing decision-making strategies, and iii) single classifier based decision-making commonly compromises in utilizing all features of input data. Structural rotor fault (SRF) is the most vital but least attended defect, which is the root cause of most RM issues. We develop a framework that uses two parallel decision-making strategies, i.e., the convolutional neural network (CNN) with fuzzy recurrence plot (FRP) as input and a long short-term memory (LSTM) network taking distinctive frequency components (DFC) stream as input. Moreover, a DFC-based ranking and image combining scheme is proposed to select the most informative sensor signals from the segmented raw vibration signals and generate a 3D-FRP, and 2D flattened FRP (F-FRP). These multi-sensor FRPs characterize the system dynamics and preserve the time-series properties of the vibration input. The DFC stream simultaneously catered to LSTM facilitates symptom parameters-based decision-making. The parallel decision scores are fused by fuzzy integral (FI) based fusion depending on the confidence of the sources. The model performs exceptionally well over the state-of-the-art methods and achieves around 99.0% accuracy with the Meggitt testbed dataset and the MaFaulDa dataset.

Deep learning attracts researchers due to its exceptional function approximation capability. In this article, an artificial neural network (ANN) is used to approximate the vibration, power and aeroelastic damping of a helicopter rotor in forward flight to predict the optimum design parameters, which are the blade bending and torsional stiffnesses. The rotor blade is modeled as elastic blades connected to a rigid fuselage. The governing partial differential equations of the rotor system are derived using Hamilton’s principle and then solved for the blade response using finite element method in space and time. The blade aeroelastic stability analysis is performed using Floquet theory for periodic differential equations. The comprehensive aeroelastic analysis software containing this formulation is expressed as neural network surrogates and then optimization is performed with these surrogates. Neural networks have universal approximation potential and are found to be an accurate method to predict the relation between the rotor vibration, power and aeroelastic stability, and the blade stiffnesses. The blade design variables for minimum vibration and power, and maximum damping, are then determined from the neural network and then the improvements are confirmed through the original aeroelastic analysis code. Results show about 66% reduction in helicopter vibration and about 100% increase in blade stability for blade designs predicted by the neural surrogates.

The adaptive dynamic mesh, user-defined functions, and six degrees of freedom (6DOF) solver provided in ANSYS FLUENT 14 are engaged to simulate the activating processes of the rotor of the Grumman WS33 wind system. The rotor is activated from stationary to steady operation driven by a steady or periodic wind flow and its kinematic properties and power generation during the activating processes. The angular velocity and angular acceleration are calculated directly by the post-processed real-time 6DOF solver without presuming a known rotating speed to the computational grid frame. The maximum angular velocity of the rotor is approximately proportional to the driving wind speed, and its maximal angular acceleration is also closely proportional to the square of the driving wind speed. The evolution curves of the normalized rotor angular velocities and accelerations are almost identical due to the self-similarity properties of the rotor angular velocities and accelerations. The angular velocity of the rotor will reach its steady value. One can use these steady angular velocities to predict the mechanical power generations of the rotor. The momentum analysis theory and the blade element momentum method are applied to predicted power generations and reveal good agreements with experimental data in the low wind speed range.

In the present study, a three-dimensional finite element framework has been developed to model a full-scale multilaminate composite helicopter rotor blade. Tip deformation and stress behavior have been analyzed for external aerodynamic loading conditions and compared with the Abaqus FEA model. Furthermore, different parametric studies of geometric design parameters of composite laminates are studied in order to minimize tip deformation and maximize the overall efficiency of the helicopter blade. It is found that these parameters significantly influence the tip deformation characteristic and can be judiciously chosen for the efficient design of the rotor blade system.

The rotor blade double-swept-tip geometry can effectively improve the aerodynamic and aeroacoustic behaviors of a rotor. However, the aeroelastic or aeromechanical behaviors of a double-swept rotor...

The aim of this paper is to represents a dynamic behavior of rotor bearing system wirth simply supported beam for three different position disc. rotating machinery such as compressors, turbines, pumps, jet engines, turtobo chargers, etc. are subject to vibrations. rotating machines are operated in very high speed and they are subjected to some unbalance force due to vibration from that machine pass to the foundation of machine.so the analysis of the dynamics parameter of rotor it is important to determine force transmissibility, natural frequency, critical speed and amplitudes of rotor system. Keywords: force transmissibility, vibration, critical speed, rotor bearing system etc.

In considering that variational modal decomposition (VMD) can fulfill the self-adaptive separation of complex signals, the paper has applied VMD to the identification of rotor–stator rubbing fault and position in aero-engine. The paper has proposed a method combing autocorrelation function (AF), variational modal decomposition (VMD) and k-nearest neighbor (KNN) classification algorithm. To reduce noise and reinforce the characteristics of faults, the method firstly calculates the autocorrelation function of vibration acceleration signals from casing. Secondly, the autocorrelation function is decomposed by VMD algorithm to obtain the intrinsic modal functions of different frequency bands. Thirdly, calculates the normalized energy of intrinsic modal components and carry out cluster analysis on the normalized energy set by k-means clustering. Finally, the normalized energy obtained are inputted into KNN classifier as characteristic vectors to identify rotor–stator rubbing fault and rubbing positions. The result indicates that the proposed AF-VMD-KNN method has the recognition rate of rubbing faults as high as over 94% in terms of different dates, rotation speeds and rubbing severity with training and testing samples randomly divided.

This work aims to investigate computationally the performance of Savonius vertical axis wind turbine having a new design feature for its blade geometry. The proposed design is based on a universal consideration of blade shape factor concept for the Savonius rotor blade. A blade shape factor ranges from zero to infinity, or vice versa, is considered in a single blade of the modified Savonius rotor. This means that each point in the two-dimensional blade profile of the suggested blade design has a single value of blade shape factor that is defined based on the dimensions of conventional semi-circular blade. The computational results of the proposed blade shape design, having blade shape factor varying from infinity to zero, showed an improvement in turbine performance as compared to conventional blade shape design. Moreover, increasing the operating range of Savonius wind turbine is expected.

This work proposes a comprehensive numerical dynamic model of a flexible-rotor bearing system based on the Hertzian and cubic polynomial nonlinear contact force methods. The model can consider the influences of the nonlinear bearing contact forces and unbalanced force caused by the rotor offset. The displacements and spectrums of the flexible-rotor bearing system from the Hertzian and cubic polynomial nonlinear contact force methods are discussed. The influences of the radial clearance, eccentricity, mass, and deformation of the rotor on the frequency–amplitude characteristics of the flexible-rotor bearing system considering a large speed range are analyzed. The results show that the dynamic and vibration characteristics of the flexible-rotor bearing system from the Hertzian and cubic polynomial nonlinear contact force methods are different. The differences of the frequency–amplitude characteristics between the flexible- and rigid-rotor bearing system are small in a lower speed stage; however, their differences are very large in a higher speed stage. This method can be applied to the nonlinear dynamic modeling and simulation of the flexible-rotor bearing system, which can predict the dynamics and prevent the system failures during the design processing of rotor system.

The emphasis on increased turbofan fuel efficiency requires advanced turbofan designs that will integrate higher engine bypass ratios and shorter nacelles. The resulting acoustic signature of these designs will have a more broadband character as well as a smaller available area for liner installation. This two-fold impact compels a need for an improvement in the state of the art in liner technology. Increasing the acoustic absorption efficacy over a broader frequency range is a means to address this need. NASA investigated over-the-rotor acoustic liners for turbofan applications as a potential solution. This type of liner represents a significant advance over traditional liners due to placement in close proximity to the rotor. An advantage of placing treatment in this region is a modification of the acoustic near field, thereby inhibiting noise generation mechanisms. This can result in higher attenuation levels than could be achieved by the conventional sound absorption means. In addition, there is potential to integrate the liner with fan rub-strip and containment components, reducing engine components and thus weight, enabling a systematic enhancement in noise reduction and engine performance. This article reviews the development and evaluation process of three unique over-the-rotor concepts focusing on the discrete tests conducted across the Technology Readiness Level span.

In this study, transient thermal analyses for a new integrated rotor and wheel hub concept are performed by consideration of convection, conduction and radiation effects. Test methods used for the characterization and certification purposes are constructed in a simulation environment and the effect of different ventilation vanes and rotor-hub arrangements on heat transfer mechanism is examined and the details are summarized for a reliable simulation process. Validated procedures are used to report a series of characterization and certification analyses, namely; CFD analyses including wheel assembly, cooldown analyses, R13 repeated stop fade and alpine hot descent analyses for current design and new integrated rotor and hub pair for alternative ventilation vane designs. The analyses are especially focused on predicting the cooling period and predicting maximum bearing temperatures for normal and excessive loading scenarios. To provide benchmark a commercial integrated rotor and hub pair used in heavy duty vehicles is also analysed. The average convective heat transfer coefficient and cooldown period of proposed integrated brake rotor are improved by 117.3% and 30.5% compared to the base design. The maximum wheel bearing temperature is decreased by 27.0% and by 27.1% for the proposed integrated brake rotor and wheel hub compared to the benchmark model, in accordance with the repeated stop and alpine hot descent analyses. In addition, the total weight reduction of 10 kg (15%) according to the base design is achieved.