Search

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.

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

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.

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.

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 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.

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.

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.

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.

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%.

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.

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.

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

A variably twisting wing has many beneficial qualities that can improve aircraft performance for a variety of flight conditions. Beneficial variable wing twist features include a means to reduce induced drag in cruise conditions, to increase lift performance, and to increase roll control. However, the actuation hardware usually required to twist large scale wings, especially given their structural stiffness, presents a substantial limitation. Through the use of shape memory alloy (SMA) torque tubes and other associated active spars, such structural deformations can be enabled. In this work, we consider the development of a benchtop and wind tunnel testing platform for potentially assessing the response of a variety of SMA-based wing twisting concepts. Using additive manufacturing (3D printing), we have designed, built, and tested a small scale prototype. The SMA actuated twisting wing developed herein consists of a rapid prototype shell that was specifically designed using a finite element approach to maintain stiffness in bending while reducing torsional rigidity. Using LabView and a simple PID controller, we have shown that an SMA torque tube was able to drive and steadily maintain the spanwise linear twist in the wing under both benchtop and wind tunnel conditions. This prototype will allow future assessment of new control schemes, new SMA actuator materials, and new structural configurations toward the development of flight-capable self-twisting wings.

Microforceps that can be used with the hyper utility mechatronic assistant system (HUMAN) for bipolar coagulation in minimally invasive neurosurgery were developed. A method of using two sets of those forceps for bipolar coagulation was developed, in which electrical current is passed through the drive wires to the forceps tips to form an electrical circuit. A prototype mechanism that employs a torque tube to achieve an opening and closing speed of 138/spl deg//s was fabricated. A forceps drive system that has a delay time of 0.06 s was constructed by using a fast control algorithm. In vivo experiments on rat abdomen and rat brain blood vessels confirmed that the bipolar coagulation function is of a practical level. Three neurosurgical clinicians confirmed the good operability and practicality of the gripping function in experiments on a human cadaveric brain. Furthermore, both doctors and engineers confirmed that the microforceps described here can be used in their present form in tumor removal and other such procedures. Following these basic engineering experiments, basic medical experiments (including experiments on the optimum distance between the lens of the endoscope and, the object of manipulation), various surgical procedures performed on living rat brain, surgical simulations performed on a human cadaver, and experiments on safety in ethylene oxide gas sterilization were performed. They lead to the conclusion that clinical use of the HUMAN system is feasible.

This paper presents a study on the effect of nonlinearities of an elastomeric bearing on isolated lag dynamics and coupled rotor/fuselage ground resonance stability of an idealized bearingless rotor blade. The rotor blade is modeled as an elastic beam with a nonlinear elastomer and a rigid torque tube. First, amplitudedependent natural frequency of the blade in lag mode is analyzed using numerical perturbation technique. Then the problem of amplitudedependent stability of the coupled rotor/fuselage system under ground resonance condition is investigated. The stability of the system is analyzed by two approaches, namely, 1) by eigenanalysis of the linearized equations and 2) by response of the nonlinear system to an initial disturbance by time integration. The results of the eigenanalysis indicate that the effect of amplitude seems to be more dominant on the progressive lag mode damping than on regressive lag mode damping. It is also observed that so far as the stability in ground resonance is concerned there exist optimum locations for the attachment of both the elastomer and torque tube. Results of the time-domain analysis of the nonlinear equations indicate clearly that the stability of the system is dependent on the magnitude of initial disturbance.

This paper presents and discusses the wind tunnel results obtained during Phase 1 and Phase 2 of the Smart Wing program. A series of four tests was conducted, two in each phase. The purpose of the tests was to evaluate the performance of smart material based control effectors in representative aerodynamic environments. In Phase 1, wing twist using a Shape Memory Alloy (SMA) torque tube and smoothly contoured trailing edge surfaces enabled by SMA wires were evaluated on a semi-span, 16% scale model of a typical fighter wing. The focus of Phase 2 was to address the design and demonstration of a high-frequency, large-deflection, and smoothly contoured trailing edge control surface capable of a spanwise variation in deflection. The actuation system for this control surface was based on piezoelectric (PZT) ultrasonic motors. A smoothly contoured leading edge control surface was also built and tested using SMA wires. These designs were evaluated on a 30%, full-span model of a representative Unmanned Combat Air Vehicle (UCAV). In each wind tunnel entry comparisons were made to the performance of conventional control surfaces. Successful results included: improved aileron effectiveness at high dynamic pressures; demonstrated improvements in lateral and longitudinal control effectiveness with smoothly contoured control surfaces over conventional hinged control surfaces; continuous spanwise shape control; and, large deflections at rates over 80°/s, which is well within the desired deflection aileron rates for control of fighter aircraft.

Despite the importance of designing support structures for solar collectors, very little reliable work has been done to investigate the forces of the wind on heliostats of solar tower at real scale. Wind loads on heliostats are usually determined at low-speed wind tunnels scale, where the design full-scale Reynolds number cannot be reached. In the present study, measured data are used to validate the simulations at wind tunnel scale. Thereafter, by using the same method, three-dimensional numerical simulations of turbulent wind flow around a big heliostat of solar tower are performed. The obtained numerical results are presented for several elevation angles at normal operation and stow position. The results revealed that the known stow position (when the backside of the heliostat is facing the ground) is not the optimum position (other optimum elevation angles are discovered) especially with high wind speed, and the effect of torque tube is significant on heliostat mean wind loads.

Shape memory alloy (SMA) actuators have recently been developed in the form of torsional tubes that can undergo large twisting deformations. Wing twisting has been investigated as a means to reduce induced drag in cruise conditions in small aircraft, but the actuation hardware required to generate wing twist at larger scales is prohibitively cumbersome. Replacing conventional actuators with SMA torque tubes provides a way to minimize weight of the twisting system but wing structural design then becomes more challenging. This analysis-driven design study examines an SMA torque tube as applied to the twisting wing design problem. A composite skin is considered to maximize wing performance under combined twist and aerodynamic loads. The SMA has been analyzed using a 3-D thermo-mechanical constitutive model while a preliminary study was performed to determine a composite lamina with appropriate unidirectional properties. An optimization was then completed to find an ideal composite layup. This optimization also included the design of a passive torque tube used to properly balance the twist generated by the SMA against that required in the wing. Localized buckling in the twisted wing was also considered and avoided. The product of this optimization was a composite wing that twisted while considering constraints of stress on the SMA. To validate the controllable use of SMA actuators, testing was completed on a scaled wing model fitted with a rapid prototype shell.

A bearingless rotor has been used to take advantage of the reduced number of helicopter hub components and maintenance expense. It comprises of three primary components: a main rotor blade, torque tube, and flexbeams. It has another advantage that its structure is simple. But large nonlinear bending-torsion is induced because the flexbeams have low torsional stiffness. Furthemore, since it has multiple load path, its structural modeling and structure-aerodynamics coupled analysis will be complicated. In this paper, a geometrically exact beam formulation was used to describe nonlinear behavior of the rotating beam elements. To conduct the multi-body analysis, multiple beam elements were assembled. The present structural model was coupled with the finite-state dynamic inflow aerodynamics. Finally, trim analysis was carried out, and the blade deformation/internal load was predicted. Its results were compared with those obtained by the rotorcraft comprehensive analysis, CAMRAD II. The blade deformation discrepancies were less than 5% and internal loads average difference was smaller than 10%.

A parametric study was performed on NiTiCu shape memory alloy torque tubes. Four samples with varying wall thickness values were evaluated for their thermo-mechanical response. The torque against the angular displacement was measured for each sample when purely martensitic and purely austenitic. The recovery torque was measured as a function of the pretwist applied during loading in the martensite phase. The trends observed were compared to three models with relatively good agreement. The recovery torque for biaxial tension/compression-torsion tests were measured with values comparable to pure torsional loadings. During the biaxial loading, a time-dependent phenomenon was observed. To evaluate the time dependence, standard creep tests were performed to elucidate the influence of the load on the temporal response of the material.

A model is presented for the analysis of primary squeal-mode vibration in aircraft braking systems. The destabilizing mechanism in the model utilizes nonlinear mechanical and material surface properties of the brake heat stack to couple lateral translation and yaw of the rotors and stators. Geometric and stiffness properties of the brake and landing-gear structure couple piston-housing torsional rotation and axle fore-aft bending with lateral translation and yaw of the heat stack. The model does not use brake negative damping and it predicts that system instability can occur with a constant brake-friction coefficient as has been observed on both dynamometer and flight tests. System stability can be altered by changes in the brake-friction coefficient, pressure, stiffness, geometry, and various brake-design parameters. Enhanced versions of the model are presented that include a more detailed structural representation of the piston-housing torque tube and the hydraulic flow equations for each piston. The model is extended to a fore-aft wheel pair on a two-axle, main-landing gear truck. Stability is investigated by determining eigenvalues of the linearized perturbation equations about each steady-state operating point of the nonlinear system. The nonlinear dynamic equations are integrated numerically to obtain time-history responses. Results from stability analyses and parametric studies using this model are presented in a companion paper.

Shape memory alloy (SMA) actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. One disadvantage of these thermally driven actuators is their slow cyclic time response compared to conventional actuators. Induction heating has recently been proposed to quickly heat SMA components. However efforts to date have been purely empirical. The present work approachs this problem in a computational manner by developing a finite element model of induction heating in which the time-harmonic electromagnetic equations are solved for the Joule heat power field, the energy equation is solved for the temperature field, and the linear momentum equations are solved to find the stress, displacement, and internal state variable fields. The combined model was implemented in Abaqus using a Python script approach and applied to SMA torque tube and beam actuators. The model has also been used to examine magnetic flux concentrators to improve the induction systems performance. Induction heating experiments were performed using the SMA torque tube, and the model agreed well with the experiments.

A slotless-armature DC motor with multiplex winding can be designed for higher power rating compared to one with a conventional slotted armature. Conventional field systems would be very heavy and a superconducting field winding is considered in order to create an iron-free stator and lightweight machine. The superconducting field winding is relieved of reaction torque by means of a special winding attached to a separate torque tube. The reaction winding is also designed to establish the necessary commutation flux in the interpole region. Test results from a small laboratory machine demonstrate the principle of the proposed torque reaction winding. A design for a 20 MW ship propulsion motor is presented.

The GT rotor is composed of a plurality of discs and two shafts. The GT gas turbine rotor may be bent after assembled because of each part has its geometric tolerance.The scheme must be carry out to straight the bend rotor. In oder to get well high speed balance, the surface of each disc excircle, torque tube and disc adaptor can’t be remachine on lath after assemble. We can machine the journal of the shaft on horizontal lathe to straight the slightly bended rotor. For the serious bended rotor, we must disassemble the rotor and change the parallelism of two side of the disc flange on vertical lathe to get a straight rotor. This attic detailed analysis these two schemes and proposed specific actions measures, then the problem of how to straight a bent GT rotor get well solution.Copyright © 2011 by ASME

A dynamometer was designed to measure the forces and moments acting on a tillage implement for use both in a soil bin and in the field. The instrument is able to measure the three orthogonal forces acting on the implement and the three moments acting about the orthogonal axes, up to a maximum force of 100 kN and a maximum moment of 100 kN m. The dynamometer employs two extended orthogonal rings mounted with their axes at right angles and a torque tube. The device was machined from the solid using a high tensile steel. The forces and moments acting on the dynamometer were measured by the use of strain gauge bridges using foil-type gauges. The design criteria of the rings and the torque tube and the arrangement and function of the strain gauge bridges are described in the paper. The dynamometer was calibrated by the application of known forces and moments and the voltage output of the strain gauge bridges was measured. The calibrations showed a high degree of linearity between the applied forces and moments and the bridge outputs. The hysteresis effect between loading and unloading was small, as was the effect of the position of the applied forces from the longitudinal axis of the dynamometer (

This paper presents an investigation into the dynamic and aeroservoelastic behavior of a seamless aeroelastic wing (SAW) structure for a small air vehicle. Attention was initially given to the design of an internal actuation system and its integration with a hingeless flexible trailing edge (TE) control surface. The SAW control section design has two innovative features, a torque tube actuation mechanism (TTAM) and a sliding TE of the wing skins. These design features allow for the SAW to have a local camber variation and wing twist in a favorable shape to meet the flight performance requirement. Based on the design features and previous optimal design of the wing box structure, the current investigation has been focused on the study of the dynamic and aeroservoelastic behavior of the SAW by using FWM. An experimental model was built to demonstrate and test the TTAM system. Some key parameters such as the stiffness of the actuation system were identified from vibration test data of the TTAM. They were used to update the FE model and analyze the dynamic response of the SAW. The results show that the SAW satisfies the design requirements from a structural point of view.

Shape memory alloys have been implemented in various applications throughout aerospace, biomedical, and various other fields. Some currently investigated applications of shape memory alloys include biomedical stents, rotary blade actuators, and pedicle screws for securing osteoporotic vertebrae. There have been many models developed by previous authors that discuss the reactions of this alloy in tension, compression, and one dimensional bending. It was the goal of this investigation to expand upon previous works to model the behavior of a shape memory alloy tube in pure torsion. The motivation for this investigation was the biomedical applications of this alloy. Because of its distinct properties of superelasticity and shape memory effect, the alloy is ideal for the design and implementation of medical devices that are smaller and more efficient than previous methods. The goal of this investigation was to model the properties of an SMA tube in torsion for use in an active orthoses for the treatment neuromuscular disorders and various other biomedical devices which involve the implementation of nitinol tubes in torsion. To this end, a model using COMSOL Multiphysics was developed which, in turn, will aid in predicting the behavior of an SMA tube under a torsional load and allow for calculation of an optimal torque tube for our applications. The outputs gained from this model were the angle of deformation under an applied torque, the resultant torque upon unloading of the tube, and the stress-strain relationships. From this information, different tube geometries will be experimentally tested to determine the best design for implementation. Once the analytical forces were determined from the SMA tubes using the COMSOL model, these results were then compared to experimental values from previous works to evaluate the accuracy of the model for the desired conditions.Copyright © 2010 by ASME

As the use of active structures continues to become more commercially viable, the need for accurate numerical modeling has gained importance. A current example of such a smart structure includes the variable geometry chevron. Future applications are also being designed, including a variable area jet engine nozzles and a torque tube actuators for rotor blades. This work concentrates on the FEA modeling of the Ni60Ti40 (wt %) SMA used in these applications and subsequent experimental validation. The constitutive model employed for the SMA material accounts for the full thermomechanical response and also accounts for such aspects as variable maximum transformation strain and smooth material hardening during transition. Model calibration is performed via uniaxial material testing. An overview of the model and material properties is presented followed by a discussion of the analysis results for the complex aerospace actuation applications. Comparisons to experimental validation of the overall system response are made.

In standard heliostat design the usual strategy of cost reduction is to increase the mirror area of the heliostats. This leads to a reduction of specific drive cost, but also to an increase of the torques caused by the wind loads, resulting in higher specific weight and higher specific drive power. The opposite strategy focuses on the reduction of the specific weight and driving power. Therefore the mirror area is decreased. In total the drive power is much lower then, but it has to be divided into more units which means a drawback for cost reduction. A combination of both strategies is to couple small heliostats so that they can be tracked by the same drive. At the Torque Tube Heliostat (TTH) the mirrors are mounted on torque tubes to simplify the coupling mechanism for the elevation angle. The optimal tracking speed of heliostats depends on the position in the field. In a heliostat with ganged facets all facets are tracked with the same speed. This leads to higher astigmatism losses compared to independently tracked mirrors. To reduce shading a certain space is foreseen between the facets of the TTH. To achieve a high mirror density and to avoid too long and therefore too flexible torque tubes this distance is limited. Thus the shading is higher than usually. Ray tracing calculations were done to obtain optimized heliostat configurations and to estimate the energy yield of a heliostat field built of 288 m² TTHs. The results are compared to a conventional heliostat field. To get an idea of the weight reduction potential of the TTH the dimensions of the torque tube, the secondary axis tube and the mirror support structure were weight optimized via FEM. The layout criterion was a mean mirror error of 5 mrad under a wind load and gravity, which was calculated from the deviations of the FE model.

The goal of this research is to use a hydrostatic transient dynamometer combined with new control techniques to replicate multi-cylinder engine dynamics which occur while the engine is started by an electric starting system. The transient engine dynamometer test system in the Powertrain Control Research Laboratory (PCRL) uses a torque tube and extremely stiff driveline in order to provide a very high bandwidth of torque actuation. The design and nature of this low inertia, stiff system requires that a standard electrical starting system be omitted. One of the objectives of this research was to assemble a new engine on the hydrostatic dynamometer and model the starting dynamics which occur during an engine cold start. The other objective was to verify and compare data collected by the PCRL and Ford to validate testing. This information will then be used in support of development of a cold start testing procedure on the single-cylinder engine transient test system in the PCRL.Copyright © 2007 by ASME

Multilevel optimization methodology is implied on Elastic Articulation (EA) rotor system to find the global and local configuration to ensure the dynamic stability with Autorotation Index (AI) consideration. EA rotor is the rotor system of generic Georgia Tech Helicopter (GTH) and it is soft-in-plane with 10% effective flapping hinge offset and forward sweep angle. Also, EA rotor has the beneficial features such as flexure beams and torque tube that eliminate dampers and hinges that lead to the its simplicity, structural safety, and reduced weight. To ensure the dynamic stability of such superior system, the methodology utilizes the high-fidelity structural beam analysis tools, DYMORE and VABS that reduce the computation time by allowing a hierarchical decomposition of the problem that separates the local (cross-sectional) sub-problem from the global optimization. The procedure is implemented using MATLAB as the overall optimizer. The results showed that the system achieved optimum values through iteration, however, sensitivity analysis is needed.Copyright © 2006 by ASME

Electromagnetic forming (EMF) technology has been used lately for the joining and assembly of axisymmetric parts in the aerospace and automotive industries. A few case studies of compressive-type joining processes applied on both aluminum and titanium or stainless tubes for aerospace applications are presented. In the first case study, tests were conducted using 2024-T3 drawn tubes joined with a steel end fitting to form a torque tube using different forming variables including: the fitting geometry, material formability and forming power (KJ). The power setting and the fitting geometry were optimized to improve the fatigue life, torque off, and the axial load capability of the torque tube joints to drive the leading and trailing edge high-lift devices. In another case study, a new process was conceived and developed for producing a high-operating-pressure (34 MPa) hydraulic system that requires the use of thick-walled titanium or stainless steel tubing with the subsequent attachment of titanium or stainless steel end fittings. The first development feature is the design of the end fitting that not only provides adequate contact surface area at the union's conical surface-fitting interface, but maximizes front sealing integrity and the strength of the joint. Second, the developed groove geometry on the tube outside diameter and its placement enhances the strength of the EMF joint between the tube and the end fitting. This was later optimized to satisfy the burst pressure test which is conducted at four times the system operating pressure. The newly designed fittings provided leak-free connections between two joints using the standard nut, coupling and unions. The technical benefits of this new method should include reducing: the manufacturing process steps (compared to orbital welding / roller swaged / elastomeric processes), inspection process steps, and cost of production; and will also provide a highly reproducible manufacturing process to maintain the highest quality possible.

The successful and practical application of shape memory alloy (SMA) torque tube actuators has frequently been hindered by an incomplete understanding of the effects of manufacturing and processing variables, particularly when working with large-scale systems producing high force and large displacements. Recently the authors have developed data for NiTinol SMA torque tubes subjected to a variety of processes routinely encountered in everyday industrial practice, with the objective of developing a robust and reliable high-energy actuator. Data are presented for more than 25 NiTinol torque tubes 5.5" long by 0.4" in diameter. The tubes were tested over a range of steady and variable loads exceeding 150 in-lbs of torque, with angular displacements of more than 60 degrees, and for durations exceeding 10,000 thermal cycles. Each tube's performance is characterized as a function of material source, level of cold work, heat treatment, tube fabrication technique, and training regime, and the results are shown. Changes in mechanical and shape memory property were also tracked, and they are reported. Application of NiTinol characteristics to practical design and fabrication of SMA actuators meeting a wide range of angular displacement and torque requirements will also be discussed.

Our primary objective is to augment the aeromechanical stability of bearingless and articulated rotor systems. We will focus on two damping strategies: (1) dampers based on magnetorheological fluids, (2) Hybrid elastomeric-magnetorheological fluid-based dampers. The flexbeam and torque tube substructure of the model-scale rotor will incorporate adaptive dampers based on MRF technology. Key aspects of the damper design will be undertaken utilizing quasi-steady constitutive models. MR fluids exhibit a reversible change in yield stress as magnetic field is applied. This change in yield stress can be exploited in the design of a damper with an electromagnet. The key performance criterion will be the damping coefficient, or the field dependent damping over the damping in the absence of applied field. The test data will be used to validate analysis, and demonstrate utility of smart active/passive damping control concepts.

This paper presents research aimed at actively altering the twist distribution of a tiltrotor blade between hover and forward flight. Three different concepts-extension-twist coupled composites, bimoment actuation and discrete SMA torque tube actuation - are considered, and the torque tube appears the most feasible. Parametric design of the torque tube and attachment technique is presented with actuation torque, heat transfer and bandwidth issues being considered to arrive at the configuration of the tube. The effect of heat treatment of the SMA in tuning the actuation characteristics is discussed. A dramatic improvement in the actuation cooling time is demonstrated through the use of active cooling using thermodelectric modules. An extension of the one-dimensional formulation of Brinson's model to the torsional case is presented. The model is shown to have good correlation with room temperature characteristics. The criterion for impedance matching between the actuator and the host structure is derived. The torsional actuator is tested both under no load and acting against a restoring spring and shows repeatable actuation characteristics.

The world largest manufacturers of commercial airplanes are currently focussing on research of advanced composite materials, which offer attractive potential for reducing the structural weight of the aircraft. The main challenge for the composite application is to make the lightweight concept work without any concern about the highly required reliability for commercial airplanes. It is achievable partly by leaning on promising future technologies and partly by using even more lightweight composite materials. Therefore, a great deal of interest for the utilization of laminated composite structural systems in the aeronautical and aerospace industries has emerged in recent years. Since the structural properties can be varied in different applications, it is very important to determine the optimized composite and component designs for specific operations in a well defined environment. Because of the complexity of fiber orientation patterns and fiber length distribution, the structural analyses of the composites are usually appropriate only for certain loading conditions. The derivation and validation of mechanical behavior of composite torque tube in a particular application, for instance, driving the components in a high lift system of a commercial airplane will be discussed in this paper.