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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

International audience; Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of High Temperature Superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.

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.

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.

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.

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 cooling systems used for rotating High-Temperature Superconducting (HTS) machines need a cooling power high enough to ensure a low temperature during various utilization states. Radiation, torque tube or current leads represent hundreds of watts of invasive heat. The architecture also has to allow the rotation of the refrigerant. In this paper, a free-convection thermosyphon using two Gifford-McMahon (GM) cryocoolers is presented. The cryogen is mainly neon but helium can be added for an increase of the heat transfer coefficient. The design of the heat exchangers was first optimized with FEM thermal analysis. After manufacture, they were assembled for preliminary experiments and the necessity of annealing was studied for the copper parts. A single evaporator was installed to evaluate the thermal properties of such a heat syphon. The maximum bearable static heat load was also investigated, but was not reached even at 150 W of load. Finally, this cooling system was tested in the cooling down of a 100-kW range HTS rotating machine containing 12 Bi-2223 double-pancake coils (DPC).

A vibration absorbing steering device for an outboard motor having a swivel bracket constructed and arranged for mounting to a transom bracket of a boat and defining a vertical passageway includes a tubular pivot shaft being pivotally engaged in the passageway, an engine mount bracket designed to mount the engine for rotation with the pivot shaft, and a vibration absorbing torque tube for absorbing vibration generated by the engine. The torque tube is vertically disposed within the tubular pivot shaft and is secured at one end to the pivot shaft. A tiller arm has a pivot end attached to the upper end of the torque tube so that the tiller arm is connected to the engine mount bracket through the torque tube, and the torque tube absorbs vibration from the engine which would normally be transmitted through the tiller arm to the operator. In addition to absorbing engine vibration, the present device also permits positive steering control of the motor by manipulation of the tiller arm.

of the Disclosure Flexbeam Helicopter Rotor With Improved Snubber-Vibration Damper Between the Torque Tube and the Flexible Spar Member A flexbeam helicopter rotor having an improved snubber-vibration damper for positioning the flexbeam spar relative to the torque tube, wherein the snubber-damper is an elastomeric bearing having a spherical and a flat portion, and whose laminates are continuous, selectively preloaded and of selected material to provide increased fatigue life, size reduction, reduced laminate stress concentration, and reduced critical design stress in the snubber-vibration damper.

The aeroelastic stability of flap bending, lead-lag bending and torsion of a bearingless circulation control rotor blade in hover is investigated using a finite element formulation based on Hamilton's principle. The flexbeam, the torque tube and the outboard blade are discretized into beam elements, each with fifteen nodal degrees of freedom. Quasisteady strip theory is used to evaluate the aerodynamic forces and the airfoil characteristics are represented either in the form of simple analytical expressions or in the form of data tables. A correlation study of analytical results with the experimental data is attempted for selected bearingless blade configurations with conventional airfoil characteristics.

A superconducting synchronous generator consists of superconducting field winding, nonmagnetic multi-tubular rotor and airgap armature winding. The superconducting generator has the benefits of 1/2-2/3 weight reduction and 0.5-0.8% efficiency improvement compared with the conventional generator, and the economic crossover between them appears to be 0.5-1.5 GVA.The problems discussed are (1) property, cooling and support of superconducting field winding, (2) thermal contraction of cryogenic torque tube, (3) tubular damper configuration, (4) seal of helium transfer coupling, (5) transposition, cooling and support of airgap armature winding, (6) vibration of the rotor.

A 50 MVA superconducting synchronous generator with a superconducting field winding was developed. This paper describes its features and test results. The saddle-shaped field winding, impregnated with epoxy resin, was mounted on a torque tube and fastened with prestressed non-magnetic stainless steel wires. A free convection cooling system, which uses the thermosiphon effect, was adopted for the field winding. Cooldown of the rotor was carried out with a constant liquid helium feed rate of 50 l/h and it was completed smoothly within about 40 hours. After that, the rotor could rotate stably at 3600 rpm. Electrical tests of no-load, short-circuit and sudden short-circuit characteristics were also carried out. Finally, the 50 MVA generator was connected to a power network and confirmed to operate successfully for 80 minutes as a syncronous condenser with a small capacity.

This report documents the results of the July 1985 and July 1986 surveys of mirror module corrosion and torque tube damage at the 10 MW/sub e/ Solar Thermal Central Receiver Pilot Plant. It also assesses the effect of vent tubes on the corrosion growth rate. Results show that 0.052% and 0.061% of the total reflective area of the heliostat field was corroded in 1985 and 1986, respectively. However, the corrosion growth rate is much less than in previous years, primarily because of the effect of mirror module vent tubes. In the July 1984 survey, 35 torque tubes were damaged due to impact with the gear box. The 1985 survey showed that 14 of those same torque tubes were re-damaged. In addition, 9 newly dented ones were found. In the July 1986 survey, 39 torque tubes were dented, of which 4 were redented from 1985. The denting is caused when the gear-drive travels past the limit switch due to a shorted diode in parallel with the limit switch.

This report documents the results of the 1984 survey of mirror module corrosion, mirror reflective area, and torque tube damage at the 10 MWe Solar Thermal Central Receiver Pilot Plant. As of July 1984, 0.029% of the total reflective area of the heliostat field was corroded. However, the 1984 growth rate of the corrosion is much less than the 1983 rate: 92% for 1984 compared with 1000% for 1983. In the 1984 survey, the average reflective area for a heliostat was 420.94 square feet compared to the design value of 430.00 square feet. In addition, we determined that the reflective area must be measured after the edge seals are installed, and that ten data points on each module are sufficient to measure the reflectivity. Also, in the survey, we found thirty-five damaged torque tubes; these damages were due to gear box travel beyond the limit switches.

The principal conclusion of the project is that large aperture linear parabolic troughs are not cost-effective for PV applications. Ground mount installations should be given consideration over roof mount systems if land space permits. The higher design costs and installation costs associated with roof installation make it less desirable. Roof structures should be carefully evaluated. In this case, the structure was not as strong as early estimates indicated, particularly in torsion. High thermal conductivity and electrical resistivity design parameters make PV module design very complex. Conductivity and resistivity are not the only material design constraints. Material selection analysis must also account for ultraviolet stability, resistance to other than ultraviolet weathering, and compatibility of thermal expansion properties between materials. The intercept factor as well as the collector design ability to maintain the intercept factor must be carefully examined during the selection process. Non-uniformity of illumination may severely effect power output due to diode by-passing of poorly illuminated cells. The linearity of the focal beam and the collector structural integrity to maintain a linear focus are extremely important selection considerations. In the case of the CAPVC system, wind-up in the torque tube has produced a non-linear focal beam making accurate focus andmore » total illumination of the receiver tube impossible.« less

A study was carried out to develop a lightweight machinery baseplate for offshore applications. To prevent platform movement from affecting the machinery alignment, the baseplate was mounted on three bearings. Inherent stiffness, with significant weight saving over a conventional baseplate, was achieved by the use of a torque tube as the primary structural component.Copyright © 1983 by ASME

Tests were conducted to evaluate the performance of a 10-in. flow controller in sodium at temperatures up to 1200 deg F. Torque tube reliability was determined by extensive mechanical cycling tests and further checking with a helium mass-spectrometer leak detector. Flow control performance and valve vibration characteristics were tested and evaluated and flow rate limits were established. The valve assembly was subjected to a thermal shock test program simulated to represent the most severe conditions likely to be encountered during a minimum l0-yr lifetime. (auth)

STRAIN-GAGE balance is a standard device for measurement of aerodynamic loads acting on models in a wind tunnel. The most common type—the six component internal balance—is employed for general, routine testing while special-purpose balances designed to meet exclusive requirements are used for specialized tests. Design of balances meant for use in supersonic blowdown tunnels can often be complicated on account of the need to withstand large transient loads that occur on the models during tunnel starting and stopping and yet have adequate sensitivity. These problems become particularly severe when the loads to be measured are of low magnitude, such as in some special tests. Successful solutions to these problems are often obtained by adoption of some unconventional design concepts and schemes. A recent example of a novel scheme for measurement of low rolling moments in low speed wind tunnels is found in Ref. 1. A special-purpose internal strain-gage balance was developed to measure low rolling moments in a trisonic blowdown tunnel. The capability of the balance to withstand large magnitudes of all the six components of load while retaining a high sensitivity to rolling moment is an important and special feature. The balance was required to measure maximum rolling moments varying between 0.2 and 10 kg-cm with a resolution of 0.002 kg-cm on wing-body models of 36 mm diameter and 380 mm length. The tunnel starting/stopping loads that the balance had to withstand were large owing not only to the relatively large size of models but also to the high pressure ratios required for starting the tunnel (starting pressures at Mach 2.5 and 3 were 5 and 6.5 atm, respectively). The above combined requirements could not be met by the usual balance arrangements employing cruciform or torque tube element and a balance incorporating some unusual design features, described below, was developed. Description The balance is of floating-frame type and the sensing element is essentially a crossed-flexur e pivot formed by four strips connecting the outer sleeve to the inner rod (Fig. 1). The strips are arranged in pairs in two transverse planes and the distance between the strips in each plane is kept as large as possible to resist high pitching and yawing moments. The strips, made of heat treated high strength alloy steel, are 1 mm thick by 9 mm wide and provide adequate sensitivity to low rolling moments. In order to increase the capability of the balance to withstand large rolling moment, an overload safeguard that automatically limits the rolling moment in the strips is provided. The safeguard, Fig. 2, is formed by a stop connected to the outer sleeve and passing through slots in the inner rod. When the balance is subjected to a rolling moment