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Bifacial photovoltaic (PV) modules have greater energy yield than traditional monofacial modules because they convert front and rear incident irradiance to electrical energy. Single-axis tracking systems can further increase energy yield and reduce the levelized cost of energy by rotating the modules throughout the day. However, racking elements in tracking systems introduce both shade and reflections on the rear face, increasing irradiance nonuniformity and fostering further electrical mismatch that reduces module power. The impact of racking, particularly that of the torque tube which spans the middle of the rear collector surface, must be accurately quantified in energy yield predictions to increase stakeholder confidence, and hasten the adoption of tracked bifacial modules. Isolating the torque-tube-reflected irradiance incident on the modules is crucial for this work. This is achieved by implementing arbitrary two-dimensional (2D) irradiance sampling on a module under test in bifacial_radiance, a ray tracing bifacial PV model, and taking the difference in rear irradiance profiles for simulations with a reflective and an absorptive torque tube at each timestamp. We calculate the TT reflection for the central one-in-portrait (1P) and two-in-portrait (2P) modules on horizontal single-axis trackers over hourly timestamps in a typical meteorological year in Livermore, California, USA. We introduce the TT reflection 2D irradiance profiles as additional light sources in DUET to quantify the TT reflection's impact on irradiance, electrical mismatch, and energy yield, as well as an incidence angle modifier's impact on TT reflection. We analyze the TT reflection based on sun zenith and diffuse fraction to group consistent illumination conditions across the year. We identify that TT reflection reduces electrical mismatch by partially offsetting TT shading, and increases annual energy yield by 0.11% and 0.18% in our particular 1P and 2P systems. While the overall impact of TT reflection is greater in the 2P system due to direct beam light incident on the TT, the TT reflection's greatest instantaneous relative contribution to total energy yield is larger for the 1P system, at high diffuse fractions and sun zeniths. For future work, we recommend validating simulation results with and without TT reflection against experimental data. The simulation method used for isolating the TT reflection may also be repurposed to help inform new TT designs that minimize electrical mismatch. Finally, instead of relying on bifacial_radiance to isolate the TT reflection, we recommend incorporating the TT as a Lambertian reflective surface in 3D view factor models with detailed shading for further TT reflection simulations.

This paper investigated the influence of the turbulent wind fluctuations in the lowest 10 m of the atmospheric boundary layer (ABL), depending on the surface roughness of the terrain surrounding a heliostat field, on the required dimensions and material cost of the structural heliostat components to resist the combined bending and torsional stresses due to the design wind loads. Turbulence data in the lowest 10 m of the full-scale ABL from ESDU 85020 were correlated with peak wind load coefficients on model-scale heliostats in wind tunnel experiments to determine the design wind loads as a function of heliostat size and terrain roughness. The results highlight the large dependence of wind loads and cost on terrain roughness with increasing heliostat size. The increasing mass of steel per unit area in the pedestal, torque tube and support mass led to their relative contribution increasing from 18% of the total specific cost of a 25 m2 heliostat to 34% of the total cost of a 150 m2 heliostat. The effect of the increasing turbulence characteristics in a high-roughness terrain resulted in a 10% increase in the total cost of a 25 m2 heliostat and a 13% increase in the total cost of a 150 m2 heliostat. An improved understanding of the influence of ABL turbulence on the design wind loads on full-scale heliostats can therefore allow the dimensions of structural components and the respective material cost of manufacturing to be optimised for the local wind conditions and terrain at different sites.

This paper proposes a high temperature superconducting (HTS) double stator machine (HTS-DSM), based on the magnetic field modulation principle. In the proposed HTS-DSM, the HTS field winding and the copper armature winding are separately located on the two stators, so that it overcomes the drawbacks caused by the coupling device for cryogenic transfer, the torque tube, the carbon brushes, and slip rings in the conventional HTS synchronous machines with the rotating field winding, bringing the merits of high reliability and low maintenance cost. Moreover, a method of amounting a ferromagnetic ring outside the HTS field winding is also proposed to reduce the negative effects of the armature reaction field on the HTS field winding, since the alternating current (AC) losses induced by the armature reaction field easily cause the quench of the HTS field winding. Totally four different topologies are proposed, and the operation principle of the HTS-DSMs is analyzed based on the magnetic field modulation principle. Then the design and optimization of the HTS-DSM is discussed in detail to present the main design parameters of the four topologies. Finally, the performance of the four different topologies are compared by the finite element analysis, the results reveal that the HTS-DSM with modular dewar and iron-teeth inner stator exhibits the merits of higher power density.

We apply ray tracing to compute the light-generated current IL within each solar cell of a bifacial tracking module, and circuit modeling to quantify how the spatial variability in $I_{L}$ (i.e., current mismatch) reduces the module's output power P MP. We find that 10 million rays are required to accurately map $I_{L}$ for a central module in a photovoltaic (PV) system at a given insolation condition. The relative reduction in P MP is found to be 1) greatest in the middle of the day for sunny conditions, 2) independent of time for very cloudy conditions, 3) higher for edge modules than central modules, 4) higher for one-high portrait configurations than for two-high, and 5) higher when the ground albedo is higher. We trace 2 billion rays on 2000 parallel cores to solve a module's annual energy yield for a system located at Golden CO with a sandy soil. The yield reduction in a one-high configuration due to nonuniform illumination is 0.23% for a central module and 0.35% for an edge module. Thus, in this example, mismatch loss due to nonuniform illumination within an individual tracking module is relatively low, despite the rear of the module being shaded by a torque tube.

Electric motors tend to be large in size because they have low speed and high torque characteristics. A superconducting motor (SCM) can be a key technology used to solve these problems. Using the characteristics of a superconductor, the SCM can reduce the volume and weight. This paper deals with the design and characteristic analysis of a 1 MW SCM for ship propulsion. An effective design of the SCM was suggested considering the electromagnetic, thermal, and mechanical properties of the motor. The SCM was designed using Y-Ba-Cu-O (YBCO) wires focusing on size, operating filed current, magnetic flux density, heat load, and mechanical stress. The current leads were also designed to minimize the heat loss in the motor, and the thermal contraction and mechanical force were calculated to design the torque tube. Electromagnetic, mechanical, and thermal characteristics were analyzed using a 3D finite element method program. As a result, the size of SCM was minimized, and the heat loss was also reduced by an effective current lead design. The designed torque tube was structurally stable with a 70% stress margin. These results will help to expand the electric propulsion motor capacity and improve the efficiency of the ship propulsion system.

The use of high temperature superconducting (HTS) generators in a large-scale wind power generation systems has drawn much attention as a contemporary research topic. In this paper, a prototype 10 kW HTS generator was designed based on the suggested design process considering electromagnetic, thermal and mechanical characteristics of the generator. We estimated the output power of the generator and operating current of the HTS field coils was decided considering the critical current and perpendicular magnetic field of the HTS wire. The thermal characteristics of the HTS generator was analysed to confirm that it was cooled to the operating temperature of 30 K. The torque tube and sticks of the HTS rotor part in the generator were designed and analysed to withstand mechanical stress considering the torque and thermal contraction. Based on these results, the HTS generator was built, and tested to prove the adequacy of the established design process of the generator. The measured cooling temperature of the fabricated generator was cooled to the target temperature of 30 K, and the magnetic field values of the HTS field coils and armature were the same as the simulation values. Finally, the output power of the generator was reached to the target output power of 10 kW. In this paper, the detailed results of the operating performance of the 10 kW HTS generator are discussed in detail.

A heliostat is a structure whose function is to reflect sunlight to a target receiver. It represents an important element in solar tower power plant (STPP). Heliostat deformations, due to stochastic wind loads and geometrical properties, can degrade optical pointing accuracy and fatigue the structural components. This paper reports on an analytical and numerical program with a goal to improve understanding of the response to wind loading on heliostats reliability. To this end, the main heliostat components, such as pedestal, torque tube and frame, have been modeled for different azimuth and elevation angles. The obtained mathematical models have been used as performance functions in order to evaluate the structural reliability of heliostat. Subset simulation method has been considered to assess this reliability. The uncertainties in wind speed, heliostat dimensions (diameter, thickness, section…) and heliostat physical properties (yield stress and Young’s modulus), have also been taken into account in this study. The results show that the external loads (wind speed) and geometrical properties, such as pedestal and torque tube diameters and truss member sections, have represented an important effect on the heliostat reliability. Therefore, for small heliostats sited in higher wind speed, it is more reliable to use thin torque tube with large diameters. However, a thick torque tube with small diameters are suitable for heliostat placed in lower wind speed.

Solar energy is a renewable form of energy. Sustainable development requires the promotion of renewable sources of energy as much as possible. Solar energy can be used to generate the electric energy by using a photovoltaic system, which could convert sunlight into electricity. Solar panels are arranged in a solar module mounting structure made of steel. The tracking of the solar panel is facilitated by the linear actuators. The solar module mounting structure is subjected to various different types of loading. Wind loading is a major concern for the structural integrity and stability of the module mounting structure. The solar module mounting structure is analyzed for various loads using the STAAD PRO structural analysis software, and then the results are used by ABAQUS finite element software to compare the behavior of hollow steel torque tube and concrete filled steel torque tubes under flexural and torsional stresses.

A new method is presented to improve cooling of the turbine blades by using active extraction from the compressor outlet to supply more cooling air with more energy. The cool air is extracted from the end of compressor through a set of peripheral holes to the air transferring channels on the disc edge or torque tube using the tangential velocity vector of the rotating shaft which results in increasing the amount and energy of the cooling air. In fact a forward angle of inlet holes for the channels is used to help the pressurized air overcome the air centrifugal force and to accelerate the flow going into the torque tube. To investigate the effect of new idea, both the original and proposed models are analyzed using 3D CFD simulation on a selected physical domain of a gas turbine. The compressible rotating Navier-Stokes equations are used for numerical simulation of two geometries. The governing equations, mesh treatment, boundary conditions and numerical setup are described. The calculation results are compared to those of the original turbine shaft to show the heat transfer improvement by enhancing the cooling flow rate and fluid energy., ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition, September 21-25, 2020, Virtual, Online

GL-1 is a single-seat mid-performance sailplane, designed to be Indonesian National Glider. As GL-1 full-scale prototype is planned to be finished in 2019, a detailed construction for control mechanism must be designed. This study will delve deeper onto the consideration due to airworthiness regulation and benchmark study from reference and other sailplane, as the general process and results have already been discussed on another publication. Study on sailplane control mechanism requirements using EASA CS-22 may reveal three main concepts on control mechanism design: proper mechanical function, pilot stick force, and protection from mechanical failure. Structural and manufacture aspect is also observed. 14 maintenance manual and 1 aircraft assembly plan were studied. There is a trend towards the usage of push-pull and torque tube mechanism for aileron, airbrake, and flap mechanism. Pull-pull configuration is widely used for rudder, tow release, and brake mechanism. Hybrid mechanism is also found for rudder mechanism. Segmentation of sub-system for each control mechanism is also have been defined. Thus, alternative designs will not only include full control mechanism, but also for each sub-system. The result of this study will be used as design basis for GL-1 internal configuration and control mechanism.

In this paper, the 3DN C/SiC torque tubes were fabricated by chemical vapor infiltration (CVI) combined with silicon melt infiltration (SMI) method with different fiber orientations (0°/90° and ± 45°) which leads to different density, torsional behaviors and failure behaviors. CT test was implemented to characterize the density heterogeneity. Using the density measured from Archimedes drainage method, FEM software was implemented to simulate the stress distribution of the tubes and calculate the failure stress. A good agreement with analytical model was obtained which helps a lot to failure analysis. Torsional tests were conducted using special attachments to a universal material test machine, the shear strain was calculated from the strain gauge, the shear strength was calculated by simplified formula, different torsional behaviors of two different fiber orientations were represented in the stress-strain curves. The fracture morphologies were observed by SEM, and the predominant factors of failure were analyzed. Torque tubes with fiber orientations of ± 45° have a higher torque capacity, modulus, and reasonable fracture morphologies, which is in good agreement with simulation results.

The effective cost reduction of solar photovoltaic (PV) power generation systems is supported by the widespread use of bifacial modules. To this end, the multiple bifacial modellings are expected to measure the energy yield excluding the mismatch power loss induced by self-shading. But, given the magnitude of non-uniform irradiance may differ between the monofacial and bifacial modules, the conventional full cell-level electrical model is no longer suitable for fast-estimation of bifacial ones. Hence, a fundamentally new equation is reformulated by parameterizing rear-shading mismatch losses (ML) optimally as a function of irradiance variability (standard deviation σ), whereby implicitly taking the effect of rear-shading into account. In Taizhou, the annual ML is found to be as high as 0.8% for close mounts (0.2 m) with a 0.2 albedo and a 22° tilt angle. Panels fixed with or without torque tube have been compared numerically. After the hourly rear-inhomogeneity and configuration dependence on cumulative annual ML of several global-mounted bifacial modules were analyzed. The authors improved the fit with an R2 better than 0.9 for generalization to any worldwide scenarios. Both experimental results and inter comparison with prior empirical equations indicate a better goodness of fits, especially in high-mismatch conditions. In this paper, the presented mismatch model will guide the deployment of revised bifacial gain (BGr)-maximized bifacial systems around the world.

Different failure behaviors were observed in the 2D C/SiC torque tubes which were fabricated by chemical vapor infiltration (CVI) with different fiber orientations (0°/90° and ±45°). CT test was implemented to characterize the density heterogeneity of the ceramic matrix composite (CMC) torque tubes. With the density value measured by Archimedes drainage method, FEM software was implemented to simulate the stress distribution of the ceramic matrix composite torque tubes and calculate the failure stress. Torsional tests were conducted using special attachments to a universal material test machine. Different torsional behaviors of CMC torque tubes with two different fiber orientations were presented in the stress-strain curves. The fracture morphologies were observed by SEM, and the predominant factors of failure were analyzed. CMC torque tubes with fiber orientation of ±45° have a higher torque capacity and modulus. In failure analysis, we found that ±45° fiber orientation CMC torque tubes have reasonable fracture morphologies.

The parabolic trough collector (PTC) technology is the most mature and cost-effective of solar thermal technologies. Given its importance in the use of solar power for electricity and industrial heating, this review presents a chruonological review of important innovations and improvements in reflector structure design and tracking system over a century of development. The fastest evolution is in the support structure of the PTC which has evolved from the old torque tube to the modern space tube. The space tube design is considered better for cost effective performance. The tracking systems have evolved from the conventional light-and-shadow sensing feedback loops to modern image-processing artificial-intelligence based systems with tremendous increases in tracking accuracy. This work also touches on reflective and structural materials. There has not yet been found a material to beat glass reflectors for specular reflectivity and durability. Considerable effort has gone into developing metal/polymer sheet reflectors, but their durability under cyclic weathering conditions is an open question. Similarly, there have been very few alternatives tried for steel as a support structure and most of these have experimented with aluminum. Only two types of actuators have been investigated: the geared motor and the hydraulic so far, and the geared motor has been the most favored. The optimization of all the components namely the reflector structure, tracking system, and reflector can lead to a design of PTC at a cost of 75–100$/m2 of aperture.

The cracking of torque tube bolts of a 130 MW gas turbine is investigated in the current work. Visual inspections along with microstructural and finite element analyses were performed for determining the cracking mechanisms. It was observed that the fracture surface was intergranular in appearance indicating crack growth along the grain boundaries. Furthermore, finite element results indicated that crack growth direction was relatively in accordance to the simulated stress distribution in the bolt. Microstructural analysis was performed and a continuous M23C6 carbide layer was observed along the grain boundaries. Although it was not clear what mechanism was responsible for the cracking, one potential mechanism of the cracking could be stress corrosion cracking (SCC). Remedial actions are proposed to minimize future occurrences of cracking.

This paper presents a bifacial PV energy yield simulation tool with highly-parameterized optical and electrical models. The resulting detailed irradiance profiles provide insight into the effects of rack shading. Horizontal parallel wiring architecture of cells in the module is found to mitigate nonuniform rear irradiance caused by torque tube shading in a single-axis tracked system for representative cloudy and clear days. Low cell shunt resistance is shown to amplify bifacial gain during low irradiance hours. Annual energy yield predictions for fixed and tracked bifacial PV systems for Ottawa, ON are also presented.

The emergence of cost-competitive bifacial PV modules has raised the question of the additional value of bifacial 1-axis tracking arrays, in particular when considering rear-irradiance losses from the tracker system itself. In this work, the effect of different geometries and materials of torque tubes is evaluated through ray-trace simulations and found to cause rear irradiance shading factors between 2% to 8% for systems without gap between the modules in 2-UP configuration. Inclusion of a gap between the modules can offset the shading factor. Electrical mismatch is also evaluated for the various configurations, and a methodology to apply shading factor and electrical mismatch loss to rear irradiance from the calculated loss in DC power, which averages 1% for the systems explored here, is proposed.

Hourly and daily bifacial photovoltaic energy yields are calculated for a single-axis tracking system in Ottawa, ON. The proposed highly-parameterized, computationally-efficient model calculates detailed front and rear irradiance profiles allowing for the analysis of real-world shading losses due to PV panel racking. Annual energy yield calculations are also supported. Cloudy and clear day shading losses are found to increase linearly with torque tube radius for a single-tier (“1-up”) portrait configuration.

We have developed models using Rhino (3D modeler) and DIVA (Ray-tracing modeler), allowing system-level raytracing simulations which include nearby shade obstructions from the photovoltaic racking structures. The ray-tracing simulated irradiance profiles are coupled with cell-level IV curve modeling to provide insight into the shading factor and mismatch loss for different racking configurations. The paper focuses on reporting results for horizontal single axis tracker (HSAT) and fixed racking bifacial system, included common module portrait and landscape configurations, as well as demonstrating the distance effect of the module above the torque tube, providing important guidance for further optimizing such mounting systems and accurate parameters required in PVsyst modeling.

Solar-tracking photovoltaic arrays are susceptible to aeroelastic fluttering during high-wind events. This dynamic fluttering behavior can grow in amplitude until the panels enter an unstable mode known as torsional galloping which can lead to panel failure or total array destruction. To better understand the physics of the torsional galloping phenomenon and to inform the discussion around panel design and recommended panel stow positions during high wind events, a fluid-structure interaction solver composed of a simulated atmospheric boundary layer with simplified panel structural responses was designed. The simulation choices and features of this solver were informed by the geometry and physical properties of an experimental panel array known to exhibit torsional galloping behavior during hind-wind events. These simulations revealed that the torsional galloping instability is driven by a combination of cyclic vortex shedding from the sun-facing side of the panel and the elastic properties of the torque tube linking the panel assemblies. Testing different stow angles across a range of wind speeds indicates that panels are generally more stable when stowed at negative angles where the leading edge is closer to the ground, hypothesized to be due to ground-blocking effects. These results are supplemented by a discussion of stability trends noted during testing and possible implications when considering multi-row array interactions.

We present the design of a noncontact high-torque magnetic coupler in the context of a high-speed (> 3600 r/min) fully superconducting rotating electric machine. The magnetic coupler is an essential component for machines where both stator and rotor are enclosed within a common cryostat. The magnetic coupler eliminates the need for rotating shaft vacuum seals, which would otherwise be needed if a conventional torque tube were used. The rotor is cooled by natural convection from the stator, similarly eliminating the need for the rotating cryogen transfer coupling used for conventional superconducting rotors. The magnetic coupler satisfies the need to transmit torque from the prime mover to the generator across a stationary cryostat boundary. We rely to an array of multiple radially spaced stages to limit axial extent and improve the torque rating of the design. We demonstrate that, while it is feasible to transmit several kilonewton meter of torque through a magnetic coupler for medium-size machines (> 10 MW), the magnetic coupler is nearly as complex as the rest of the machine. This option should be considered if known reliability issues with high-speed rotating vacuum seals and cryogen transfer couplings cannot be resolved.

Long-distance crewed space exploration will require advanced thermal control systems (TCS) with the ability to handle a wide range of thermal loads. The ability of a TCS to adapt to the thermal environment is described by the turndown ratio. Developing radiators with high turndown ratios is critical for improving TCS technology. This paper describes a novel morphing radiator designed to achieve a high turndown ratio by varying its own radiative view factor and effective emissivity through the use of shape memory alloys (SMAs). This radiator features two SMA torque tubes cantilevered to a rigid fixture. The working fluid is transported within the SMA tubes through an annular flow system. In a cold environment, radiator panels fixed to the free ends of the tubes are oriented vertically in a parallel-plate fashion, where the high-emissivity interior faces have restricted views to the environment and heat rejection is minimized. When the system heats up, the tubes actuate by twisting in opposing directions, bringing the panels to a horizontal position with the interior faces exposed to maximize heat rejection. When the system cools down, the tubes twist in reverse, restoring the panels to the vertical orientation where heat rejection is again minimized. This variable heat rejection system has the potential for achieving higher turndown ratios than those of current state-of-the-art systems. A benchtop prototype has been designed and tested to demonstrate actuation and to explore internal heat transfer effects. Prototype design, testing, and results are herein described.

Direct-drive superconducting (DDSC) generators are promising in wind power due to their light weight, compact size, and high efficiency. Torque tube is one of the most important part in a DDSC generator. It should be capable of maintaining the airgap length of the generator and transferring the extremely large electromagnetic (EM) torque from low rotating speed. Furthermore, the torque tube should have a low conduction heat leakage to decrease the heat load on the cryogenic system. The cooling cost, which accounts for a large proportion of the maintenance cost, would then be reduced. This paper proposes a new torque tube structure for a 12 MW low temperature superconducting direct-drive wind generator. Thermal analysis is done to estimate the heat leakage of the torque tube. Thermal-structural coupling analysis is then carried out to evaluate the mechanical performance of the torque tube. The three-dimensional (3-D) finite-element method is used in the analysis. Reliability of the bolts in the torque tube is also verified.

The asymmetry limitation between left and right wing flap surfaces is one of the most severe requirements for the design of the actuation and control system. When the position asymmetry exceeds a defined value, it must be detected and limited by appropriate monitoring devices equipped with a suitable software. In the design of a new flap control system the development of the asymmetry monitoring subsystem plays a very important role and, together with the flap system layout selection, it was and still is a debated matter in the industry. The currently used monitoring technique is based on differential position detection between left and right surfaces. Their use generally slightly reduces the asymmetry, but in some cases it may have an unreliable behavior. To overcome the shortcomings of the previous models, we propose new and different monitoring strategies and assess their positive effects on the maximum asymmetry following a torque tube failure; in particular, the asymmetry reduction coming from the employment of the proposed techniques in the considered operative conditions (typical deployment / retraction flap actuations), with respect to a previous type of technique, can be evaluated in the order of 30%.

Torque tube is widely used on the offshore platform, and its quality plays an important role on the security of offshore platform. The cold bending forming process for torque tube production is nonlinear and dynamic seriously, with the fault types varied and complex, so the traditional PCA cannot get a good effect in the fault detection of cold bending forming. In this paper, a fault detection method based on dynamic kernel principal component analysis (DKPCA) algorithm is introduced to detect the faults of the cold bending forming. Eleven process variables were sampled from the actual manufacture process and used for fault diagnosis. PCA and DKPCA are used to carry out fault detection on the cold bending forming process, and the results show that the effect of DKPCA for fault detection is better than that of PCA. DKPCA can improve the detection effect greatly due to its advantage in nonlinear and dynamic characteristics, which can be applied widely in actual process.

In order to improve the overall performance of high temperature superconducting (HTS) motor, a radial connection torque tube with high strength and low thermal leakage has been designed. Firstly, fiberglass epoxy composite is chosen as construction material. The structural size of the torque tube is obtained by means of load analysis and theoretical calculation. Secondly, thermal leakage of the torque tube is calculated with both theoretical method and 3D finite-element analysis (FEA). According to the result of the thermal analysis and mechanical loads, the structural stresses of the torque tube are also obtained by FEA method. Lastly, a low temperature test platform is developed to verify the strength and the thermal leakage of the torque tube. The results show that the maximal shear stress of the torque tube is 24.3 MPa and thermal leakage of torque tube is 10.5 W, which satisfy the design requirements of the HTS motor. The torque tube also works in good condition at full-power and full-torque testing of the motor. The design method is also applicable for other similar design of torque tube in other applications.

A direct drive 12-MW superconducting wind turbine generator has been designed. The rotor of the generator is made of low temperature superconductor (LTS) coils, which are wound from NbTi/Cu cable-in-conduit conductors (CICC) cooled with forced flow supercritical helium at 4 K. To ensure the stability of the generator rotor, it is necessary to design a reliable cryogenic system. With consideration of the radiation heat loads, ac loss, conduction heat leak by residual gas, current leads and torque tube, the heat load of the cryogenic system is analyzed. Aiming at decreasing the heat load of the cryogenic system and enhancing the overall efficiency of the generator, new structures of torque tube and thermal shields are proposed, and the main parameters of the cryogenic system are determined.

를 통해 복합재료로 제작된 플렉스빔과 토크튜브가 구조적인 강성 요구도를 만족함을 확인할 수 있었다. Abstract: This paper describes the manufacturing processes for a flexbeam and torque tube made of composite materials, along with the procedures for testing their basic properties. A flexbeam and torque tube can be considered to be key structural components of a bearingless rotor hub system. A hinge offset effect can be realized by a large elastic deformation and twist of the flexbeam, and the blade pitch control forces are transferred by the rotation of the torque tube. The basic property tests included bending and twist tests to determine the flap stiffness, lag stiffness, and torsion stiffness of the flexbeam, torque tube, and blade, and these tests were performed prior to starting the whirl tower test. In addition, the estimated results were compared with experimental data, and the calculations were found to be a good match for the analysis results and had a similar tendency. Through these results, we could confirm that a flexbeam and torque tube made of composite materials satisfied the structural stiffness requirements.

In this study, a three-dimensional thermomechanical constitutive model based on the microplane theory is proposed to simulate the behavior of shape memory alloy tubes. The three-dimensional model is implemented in ABAQUS by employing a user material subroutine. In order to validate the model, the numerical results of this approach are compared with new experimental findings for a NiTi superelastic torque tube under tension, pure torsion, and proportional tension–torsion performed in stress- and strain-controlled manners. The numerical and experimental results are in agreement indicating the capability of the proposed microplane model in capturing the behavior of shape memory alloy tubes. This model is capable of predicting both superelasticity and shape memory effect by providing closed-form relationships for calculating the strain components in terms of the stress components.

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.

This paper presents an improved structural analysis for a bearingless helicopter rotor. The bearingless rotor usually features a significantly large elastic twist in the flexbeam and additional unique structural characteristics. Thus, it will require sophisticated structural analysis and relevant numerical validation procedures due to its multiple load paths, as induced by the single or multiple flexbeams and the torque tube. In this paper, an extended finite element formulation was derived to consider the multiple components as individual beam elements. A geometrically exact beam formulation was adopted to describe the nonlinear behavior of these major components in the rotor precisely. To implement the interconnecting kinematic relationship with the major components, Lagrange multipliers were used. The present static analysis was validated through comparisons with the existing multi-body dynamics analysis DYMORE. Additional results were obtained for rotating conditions in both a vacuum and a set atmosph...

Rotor system is a very important part which produce lift, thrust and control force in helicopter. Component of rotor system must have structural integrity for applied load. The estimation of structural integrity is regarded greatly as important in aerospace field. In this study, the process of structural analysis performed for bearingless main rotor system of helicopter. The composite flexbeam and torque tube of bearingless main rotor are very thick, so 3D layered soild elements of MSC.PATRAN were used to get the finite element analysis results. To estimate structural integrity, non-linear static analysis considering geometric non-linearity is performed. In addition, detailed finete element analysis and non-linear static analysis are performed to consider the stress concentration for fitting effect and contact surface. The estimation process of structural integrity for bearingless main rotor system of helicopter may help the design.

This paper develops a novel mechanism of direct drive tails for miniature helicopters. The developed tail employs a brushless motor mode and outperforms the traditional torque tube tails with less vibration and prompter responses. Mechanism design and implementation of the direct drive tail is presented at first. A nonlinear model is adopted into analyzing the direct drive tail's influence on kinematics and dynamics of miniature helicopters. Control parameters are optimized by online testing and experience as well. Experiments with an Align T-REX 450L helicopter and a Pixhawk autopilot are conducted to validate the effectiveness of the developed new-type direct drive tail mechanism.

The critical hydraulic configuration for a set of torque-tube gates controlling the flow through the navigable portion of a spillway was experimentally identified. In this paper, an analytical model for the upstream pressure field on a typical gate within the set is constructed. The gate rotation from the maximum elevation (gate in closed position) and the hydraulic torque transmitted by the pressure field to the gate tube are formulated. Mean values of parameters of response are often sufficient for the preliminary design of a gate. The dispersions of these parameters of response, which are necessary for the final design of a gate, may be computed using the corresponding mean-square values. These were obtained empirically in a flume from experiments on a 1/15-scale physical model of a set of three prototype gates for the Montgomery Point Lock and Dam project. Theoretical predictions of parameter mean and mean-square values compare well with the average corresponding statistics obtained experimentally.

형상기억합금(shape memory alloy: SMA)은 낮은 온도에서 변형이 용이하며 열을 가하면 저온의 형상으로 복원하는 형상기억효과와 상변태 이상의 온도에서 변형과 복원이 동시에 일어나는 초탄성 효과를 가진다. 이중에서도 Ni-Ti 합금은 Nitinol 이라고도 불리며 약 8∼10% 의 큰 변형률, 높은 복원력, 뛰어난 피로수명 등의 성질을 가지고 있기 때문에 많은 연구가 진행되었다. 형상기억효과는 형상을 원자 배열로서 기억하기 때문에 발생한다. 이러한 효과는 확산에 의하지 않고 변태하는 합금에서 나타나는데 고온의 모상원자배열이 저온에서의 변형 후에 기억되고 있다가 고온이 되면 원래의 원자 배열로 돌아가는 것이다. 이 경우 형상 회복과 동시에 큰 힘이 발생하기 때문에 SMA 는 센서로서의 용도만 아니라 기계부품을 작동시키는 액추에이터와 열 엔진으로서 열 에너지를 위치 에너지나 운동 에너지로 변환시키는 곳에도 사용된다. 1 차원 형상의 SMA 도 3 차원적으로 거동하기 때문에 3 차원 구성방적식을 고려하는 것은 해석의 정확도에 큰 영향을 미치며 3 차원 형상일 경우 반드시 3 차원 거동을 고려해야 한다. 3 차원 거동을 (나타내기 위해 Reiner등1)은 구성방정식의 전 방향 오일러 시간 이산화에 근거한 수치해석을 하였고, Boyd and Lagoudas

An aeroelastic analysis of bearingless rotors is investigated using large deflection beam theory in hover and forward flight. The bearingless configuration consists of a single flexbeam with a wrap-around torque tube and pitch links located at the leading edge and trailing edge of the torque tube. The outboard main blade, flexbeam, and torque tube are all assumed as an elastic beam undergoing arbitrary large displacements and rotations, that are discretized into beam finite elements. In the bearingless rotors, a flexbeam has various sections made of laminate. The sectional elastic constants of a composite flexbeam, including the warping deformations, are determined from a refined cross-sectional finite element method. Numerical results of the static deflections and the aeroelastic modal damping are presented for various configurations of a composite flexbeam and are compared with previously published experimental results and theoretical values obtained from a modal analysis using a moderate deflection-type beam theory.

High-temperature superconductor (HTS) synchronous machines are expected to have higher efficiency and smaller size than normal conductor synchronous machines, and are being developed mainly in the USA and Germany. This paper describes a computation method of heat loads in cryogenic parts of HTS synchronous machines, and the evaluation study results of heat loads in HTS synchronous motors for blowers, in which Bi-2223 is used at 30 K, using the computation method. From the evaluated heat loads, the required capacity of the refrigerator for HTS synchronous machines may be determined. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 62–68, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20338