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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A Voltage Injection-Based Current Harmonics Suppression Strategy for Six-Phase PMSM With Nonsinusoidal Back EMF

This article presents a voltage injection-based current harmonic minimization method for wide bandgap device-based six-phase permanent magnet synchronous machine (PMSM) drives. The presence of low-order harmonics is common in the back EMF of PMSMs with low slot and high pole numbers. The back EMF harmonics generate low-order harmonic currents that increase torque ripples. Furthermore, zero-sequence current (ZSC) is also observed if all six phases are connected to a common neutral point. ZSC does not affect the torque ripple but reduces the system efficiency. A special technique is required to reduce ZSC for variable speed drives as direct ac component to synchronous reference frame (SRF) dc transformation is not possible for ZSC. In this article, a voltage injection-based current harmonics reduction method is proposed. The injected harmonic voltage coefficients are calculated from the harmonic estimations of back EMF and updated using closed-loop harmonic compensators to improve steady-state performance. For ZSC reduction, third harmonics power controller, and for 6n ± 1 (n = 1, 2,...) order harmonic current reduction, SRF current controllers are presented in this article. Furthermore, the current harmonics minimization method is experimentally verified using a GaN-based three-level active neutral point clamped inverter-driven six-phase PMSM.

42 ENGINEERING↗
DOE OSTI2025

Reconfigurable structural color by reversible switching of colloidal discoid liquid crystal alignment

Combining the effects of alternating-current (AC) electric fields and sedimentation reconfigures colloidal discoids between planar and homeotropic orientational alignments, thereby controlling the material’s structural color. Here, we self-assemble micrometer-size polystyrene discoids in an isopropanol-water mixture. After sedimentation, the discoids adopt a homeotropic alignment, with the minor axis perpendicular to the substrate. Adding an AC electric field (1 kHz) of ≥0.50 V switches the discoids to planar alignment—with the minor axis parallel to the substrate—within ∼100 s. Removing the field switches them back to homeotropic alignment within ∼300 s. Kinetic modeling of the field-induced torques yields good agreement with these measurements. The peak wavelength and intensity of the crystal’s diffraction response shift significantly upon reconfiguration; scattering simulation predicts these shifts. The reconfiguration is maintained for at least 10 cycles. This method is a simple, scalable avenue to reconfigure the optical properties of colloidal crystals produced from simple dielectric spheroids.

colloidal crystals↗
DOE OSTI2020

Toroidal Field Reversing Switch

A motor-driven, high-current switch is being designed by Stäubli Electrical Connectors in collaboration with Princeton Plasma Physics Laboratory to reverse the DIII-D Toroidal field coil current. The existing field reversing procedure requires approximately 4 h of labor performed between run days to reconfigure the bus work, thus requiring a separate run day to complete experimental scans with both field directions. This typically results in different wall conditions which complicate the results or make them invalid. The proposed switch will complete the reversal process in approximately 4-5 min, between shots, so that wall conditions are not a factor, and easily fits within the 10-12 min DIII-D shot cycle. The switch is a compact design fitting into a 157.5 × 41 cm envelope. The switch uses two copper pins that slide between Stäubli MULTILAM contacts. The switch is rated for total current of 180-kA dc for 10 s with a 12-min repetition rate; the maximum operating coil current is 124-kA dc. The switch diagnostics include: voltage drop, current monitor, thermal monitors, position sensors, and motor torque. Here, the switch is rated for 300 cycles per year, and 3000 cycles overall before contact replacement, with contact inspection yearly. The design details and operation of the switch are covered in this article.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Improving Efficiency of Off-Road Vehicles by Novel Integration of Electric Machines and Advanced Combustion Engines

Modern off-road equipment will increasingly rely on electrified implements that will deliver precision control with a smaller footprint than hydraulics. The primary energy converter, however, will be an onboard reciprocating internal combustion engine because of the power density of hydrocarbon fuels in comparison to electrical energy storage and the remote locations where much of this equipment is deployed. Adding energy storage and electric machines creates opportunities to improve efficiency while reducing emissions. This program investigated approaches to take advantage of the extra flexibility that an enhanced electrical system to enable high-efficiency, low-emissions combustion technologies. The current program evaluated hybridization of both the torque application and air-handling systems to maximize efficiency while minimizing cost. This program designed, analyzed and tested a hybrid off-road vehicle consisting of a series electric powertrain with energy storage, an electrified air system, and a 33% downsized diesel engine. Detailed comparisons were made between the base powertrain and the developed powertrain using powertrain simulations, engine testing, and vehicle testing. The key results of the study are: • The resulting vehicle reduces fuel consumption by 5% to 15% at equal productivity. The primary improvements were due to recovery of regenerative braking losses for cycles where large transients are encountered. • The electrified air system was an enabler to allow engine downsizing. This was most important for duty-cycles where the engine primarily operated at moderate loads and had few low speed high torque conditions. • Engine level improvements showed re-optimization of the powertrain is possible when electrified air handing is available. Increased exhaust gas recirculation and advanced injection timing allowed up to a 15% reduction in brake specific fuel consumption at equal NOx and transient response. Compared to the larger engine, the downsized engine achieves up to an 18% reduction in brake specific fuel consumption over the non-road transient cycle. • The life cycle analysis and total cost of ownership study showed that the hybrid powertrain has the potential to reduce 5-year CO2 and total cost of ownership by ~6% over the baseline vehicle. The results also indicated that a pure battery electric vehicle is not feasible in this application and is likely to increase the CO2 emissions due to the CO2 from battery production. A hybrid powertrain with low carbon fuels shows the potential to substantially reduce CO2 and total cost of ownership.

02 PETROLEUM↗
DOE OSTI2022

Hip Abductor Strength Asymmetry: Relationship to Upper Extremity Injury in Professional Baseball Players

Background: Hip strength is an important factor for control of the lumbo-pelvic-hip complex. Deficits in hip strength may affect throwing performance and contribute to upper extremity injuries. Hypothesis: Deficits in hip abduction isometric strength would be greater in those who sustained an upper extremity injury and hip strength would predict injury incidence. Study Design: Prospective cohort study. Level of Evidence: Level 3. Methods: Minor League baseball players (n = 188, age = 21.5 ± 2.2 years; n = 98 pitchers; n = 90 position players) volunteered. Hip abduction isometric strength was assessed bilaterally with a handheld dynamometer in side-lying position, expressed as torque using leg length (N·m). Hip abduction strength asymmetry was represented by [(trail leg/lead leg) × 100]. Overuse or nontraumatic throwing arm injuries were prospectively tracked. Poisson regression models were used to estimate relative risk ratios associated with hip asymmetry; confounders, including history of prior overuse injury in the past year, were included. Results: Hip abduction asymmetry ranged from 0.05% to 57.5%. During the first 2 months of the season, 18 players (n = 12 pitchers) sustained an upper extremity injury. In pitchers, for every 5% increase in hip abduction asymmetry, there was a 1.24 increased risk of sustaining a shoulder or elbow injury. No relationship between hip abduction strength and injury was observed for position players. Conclusion: Hip abduction asymmetry in pitchers was related to subsequent upper extremity injuries. The observed risk ratio indicates that hip abduction asymmetry may contribute a significant but small increased risk of injury. Clinical Relevance: Hip abduction muscle deficits may affect pitching mechanics and increase arm stress. Addressing hip asymmetry deficits that exceed 5% may be beneficial in reducing upper extremity injury rates in pitchers.

Sport Sciences↗
DOE OSTI2024

Performance characterization and modeling of an oscillating surge wave energy converter

Abstract Testing wave energy converters in the ocean could be expensive and complex, which necessitates the use of numerical modeling. However, accurately modeling the response of wave energy converters with high-fidelity simulations can be computationally intensive in the design stage where different configurations must be considered. Reduced-order models based on simplified equations of motion can be very useful in the design, optimization, or control of wave energy converters. Given the complex dynamics of wave energy converters, accurate representation, and evaluation of relative contributions by different forces are required. This effort is concerned with a performance characterization of the hydrodynamic response of an oscillating surge wave energy converter that is based on a reduced-order model. A state-space model is used to represent the radiation damping term. Morison’s representation of unsteady forces is used to account for the nonlinear damping. Wave tank tests are performed to validate simulations. A free response simulation is used to determine the coefficients of the state-space model. Torque-forced simulations are used to identify the coefficients of the nonlinear damping term for different amplitudes and wave frequencies. The impact of varying these coefficients on the response is investigated. An assessment of the capability of the model in predicting the hydrodynamic response under irregular forcing is performed. The results show that the maximum error is 3% when compared with high-fidelity simulations. It is determined that the nonlinear damping is proportional to the torque amplitude and its effects are more pronounced as the amplitude of the flap oscillations increases.

16 TIDAL AND WAVE POWER↗
DOE OSTI2023

Observation of the Fluctuation Spin Hall Effect in a Low-Resistivity Antiferromagnet

The spin Hall effect (SHE) can generate a pure spin current by an electric current, which is promisingly used to electrically control magnetization. To reduce the power consumption of this control, a giant spin Hall angle (SHA) in the SHE is desired in low-resistivity systems for practical applications. Here, critical spin fluctuation near the antiferromagnetic (AFM) phase transition in chromium (Cr) is proven to be an effective mechanism for creating an additional part of the SHE, named the fluctuation spin Hall effect. Further, the SHA is significantly enhanced when the temperature approaches the Néel temperature (T N ) of Cr and has a peak value of -0.36 near T N . This value is higher than the room-temperature value by 153% and leads to a low normalized power consumption among known spin–orbit torque materials. This study demonstrates the critical spin fluctuation as a prospective way to increase the SHA and enriches the AFM material candidates for spin–orbitronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Nonlinear coupling of tearing modes in reversed field pinch plasmas with stepped pressure profiles

A theory of the three-wave coupling of triplets of tearing modes in toroidal pinches [i.e., either reversed field pinches (RFPs) or tokamaks] was proposed by R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)]. However, this theory only applies to toroidal pinches with negligible equilibrium plasma pressure gradients. Such a limitation is particularly inappropriate to RFPs. This paper generalizes the analysis of R. Fitzpatrick [Phys. Plasmas 6, 1168 (1999)] in order to take the equilibrium pressure gradient into account. However, for the sake of simplicity, a stepped pressure profile, rather than a continuous profile, is employed. In the limit in which the number of steps becomes very large, the results obtained from the generalized theory are presumably equivalent to those that would have been achieved using a continuous pressure profile. The generalized theory is used to investigate the formation of the characteristic toroidally localized pattern of phase-locked m = 1 and m = 0 tearing modes in RFP plasmas that is known as the “slinky” pattern. The incorporation of the equilibrium plasma pressure into the analysis is found to be of crucial importance when determining the properties of the pattern. This is the case because the plasma pressure controls the number of unstable m = 1 and m = 0 tearing modes, and also significantly affects the strength of three-wave coupling, as well as the phase relation between the phase-locked m = 1 and m = 0 modes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Efficient, Compact, and Smooth Variable Propulsion Motor (Final Report)

In this project, a new architecture of highly efficient hydraulic motor was developed for the propulsion of off-highway vehicles. The motor uses an adjustable linkage driving a cam to vary the displacement of the piston, resulting in a Variable Displacement Linkage Motor (VDLM). The motor uses low friction rolling element bearings to significantly reduce mechanical friction, especially in the demanding low-speed high-torque conditions experienced by off-highway vehicles. The VDLM has high torque capabilities for its size due to the radial piston packaging and use of a multi-lobe cam. A VDLM is very smooth due to the ability to tune the torque ripple through the design of the cam profile. The project was divided into three periods. During the first period, a dynamic model was constructed of the motor to predict the performance of the motor and the vehicle. During the second period, a single-cylinder learning prototype was designed, built, and tested to validate the models constructed in the first period. In the third period, a multi-cylinder prototype motor was optimized, designed, fabricated, and tested. The motor demonstrated excellent mechanical efficiency (above 92.5% across the range of displacements), but the experimentally measure volumetric efficiency was lower than expected due to higher leakage rates created by the poor tolerance control on the prototype. To validate the dynamic models developed in the first period and better understand design trade-offs. In the third period a multi-cylinder concept demonstration prototype will be designed, fabricated, and tested. The final prototype will be tested on a motor dynamometer and will be utilized in hardware-in-the-loop testing to demonstrate its efficiency and performance impacts on the overall drive train. The experimental results were used in a drive train simulation of a compact track loader operating through a drive cycle. Using the VDLM in a hydrostatic circuit yielded 17.1% reduction in fuel consumption and 36.5% reduction in a series hybrid transmission.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2025

Thermal and electric multidomain dynamic model for integration of power grid distribution with behind-the-meter devices

As renewable energy sources like solar and wind power become more integrated into the grid, coordinated control of behind-the-meter devices is crucial for enhancing grid flexibility and reliability and for meeting cost targets, with standardized models being developed to support this transition. The increasing flexibility and uncertainty of integrated renewable energy grids, along with interactions between various subsystems, make traditional steady-state modeling insufficient to capture transient and dynamic behaviors. Current models (e.g., composite load and battery equivalent models) focus on thermodynamic or electrical characteristics but overlook critical electromechanical interactions. This limits the ability to share performance information for grid services and hampers fast dynamic simulations. In addition, motor stalling is usually triggered by a fault event and attributed to the characteristics of the mechanical torque of the motor, resulting in absorption of a large amount of reactive power during the stalling period. Further, this significant withdrawal of reactive power will deteriorate the dynamic voltage stability of power grids and cause delayed voltage recovery. Therefore, an in-depth modeling of the thermodynamics or mechanical torque is essential to study the impacts of the realistic torque characteristics of those behind-the-meter devices on power system voltage stability. This study developed a dynamic multidomain model for building HVAC systems, such as air-source heat pumps, to simulate their thermal and electrical responses to grid transients. The model can accurately predict power metrics with a mean absolute percentage error of 10%, by validating against with power system computer-aided design performance data. Case studies demonstrate the model capability of capturing the transient response to sudden voltage changes, rapid load fluctuations, and system shutdowns respectively. During a sudden voltage drop (30% for 0.1s), a fully loaded heat pump’s motor speed dropped, continued declining, and shut down after 3.6s, with severe power oscillations and a torque spike. A partially loaded unit experienced temporary oscillations but stabilized. Under higher building loads, compressor speed increased from 64% to 100%, with power and torque rising before stabilizing. In safety-triggered shutdowns, power decreased after minor fluctuations, and torque briefly spiked before dropping to zero.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Magnetic droplet soliton pairs

We demonstrate magnetic droplet soliton pairs in all-perpendicular spin-torque nano-oscillators (STNOs), where one droplet resides in the STNO free layer (FL) and the other in the reference layer (RL). Typically, theoretical, numerical, and experimental droplet studies have focused on the FL, with any additional dynamics in the RL entirely ignored. Here we show that there is not only significant magnetodynamics in the RL, but the RL itself can host a droplet driven by, and coexisting with, the FL droplet. Both single droplets and pairs are observed experimentally as stepwise changes and sharp peaks in the dc and differential resistance, respectively. While the single FL droplet is highly stable, the coexistence state exhibits high-power broadband microwave noise. Furthermore, micromagnetic simulations reveal that the pair dynamics display periodic, quasi-periodic, and chaotic signatures controlled by applied field and current. The strongly interacting and closely spaced droplet pair offers a unique platform for fundamental studies of highly non-linear soliton pair dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Wound Field and Hybrid Synchronous Machines for EV Traction with Brushless Capacitive Rotor Field Excitation (Final Report)

This project focused on the development of wound field synchronous machines (WFSMs) and hybrid excitation synchronous machines (HESMs) with brushless capacitive power transfer for the field excitation. The target application for the machines developed is the main traction motor in electric vehicles. The magnetization in these types of machines is provided by a field winding on the rotor which is excited with DC current. The magnetization level in the machine can be varied by changing the magnitude of the field current. The variable magnetization or field is one of the key features of WFSMs. WFSMs are commonly used as generators however they have several attractive features for automotive traction applications. 1) No use of permanent magnet: Rare earth permanent magnets are primarily mined and processed in China. They have been subject to large price and supply variations and their export may be restricted during times of geopolitical tension. 2) Easy field weakening: Wound field synchronous machines have complete control of their field excitation. With proper design, this type of machine can electromagnetically have an infinite constant power speed range. 3) High power factor: With proper choice of the field excitation, WFSMs may be operated with high or even unity power factor. This potentially allows for the inverter connected to the stator winding to be downsized. In comparison induction machines and interior permanent magnet synchronous machines must supply reactive power to the stator increasing the kVA rating and cost of the inverter. 4) Reduced iron losses at high speed: By reducing the field excitation, the iron loss in the stator can be reduced. This is in comparison to interior permanent magnet synchronous machines which must use stator current to buck or reduce the flux produced by the permanent magnets. Generally, WFSMs have their highest efficiency at high speed. 5) Torque output at high temperatures: The magnetization provided by the field winding only depends on the field current and not on the field winding temperature. This is in contrast to permanent magnet machines where the permanent magnet flux decreases as the magnet temperature increases. Historically a number of approaches have been developed to provide DC current to the rotating field winding in WFSM’s including brushes and slip rings, low frequency brushless exciters, and high frequency rotary transformers and rectifiers. In this project, a different approach was used: brushless capacitive power transfer. Brushless capacitive power transfer uses two sets of rotating capacitors or electrodes in which an AC electric field is established by a high frequency inverter. A displacement current can flow through the airgap in the rotating capacitors which is rectified on the rotor using a diode bridge. The potential advantage of capacitive power transfer is that there is no need for heavy iron to guide magnetic flux. The electric flux lines terminate on the charges on the rotary capacitor surfaces. This should also limit the electric field outside the rotary capacitor airgaps. The main challenge with capacitive power transfer is that the capacitance and surface area of the rotating capacitors is small. Because capacitive power transfer systems are essentially a dual of a magnetic system, an Ampere per Hertz relationship is characteristic versus a Volts per Hertz relationship. A very high frequency power inverter must be used to provide sufficient excitation to the field winding. The concept of using capacitive power transfer to excite a high performance WFSM was initially developed in a previous U.S.A. Dept. of Energy project, DE-EE0006829. This project focused on increasing the power density of the WFSMs and reducing the cost and manufacturing complexity of the capacitive power transfer system. This project has demonstrated that WFSMs with brushless capacitive field power transfer can provide a high-power density and low-cost automotive powertrain technology.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

wtDigiTwin (Wind Turbine Digital Twin) [SWR-21-15]

This wind turbine digital twin software (wtDigiTwin) provides a digital twin solution for wind turbine applications. The focus of wtDigiTwin is to estimate loads, motions and environmental conditions for an operating wind turbine. The program uses supervisory control and data acquisition (SCADA) measurements as inputs, together with a wind turbine model. The wind industry is currently challenged by the high cost of operation and maintenance. These costs could be mitigated if component failures are predicted, but such predictions are difficult unless the turbines are equipped with expensive measuring devices. The alternative is to use a digital twin such as wtDigiTwin to estimate the necessary signals. wtDigiTwin can perform online prediction of signals that are otherwise not measured, using a limited set of reliable measurements and a physics-based model. The predicted signals can be used in applications that have direct cost benefits: 1) real-time estimation of the fatigue consumption of key components of the wind turbine; 2) root cause analyses and failure detections ; 3) lifetime reassessments ; 4) improvements to follow-on designs. The current version provides examples to estimate wind speed, thrust, torque, tower-top position, and tower loads on an onshore wind turbine using the following measurements tower top acceleration, generator torque, pitch, and rotational speed. The model combines a linear state-space model, a wind speed estimator, and a Kalman filter algorithm that integrates measurements with the state model to perform state estimations. The state space model is obtained either using OpenFAST linearizations, or using the yams package provided with the software.

Branlard, Emmanuel↗
DOE OSTI2023

Electrification: 2023 Final Progress Report

This project proposes to develop a high-power density, high speed traction motor architecture called QMag, driven by a high-power density motor drive inverter using silicon carbide semiconductor devices. This new architecture will achieve the efficiency and power density targets by means of innovative winding and rotor structures, high bandwidth controls, and advanced thermal management solutions. The project team will pursue the goals of the project systematically, through Finite Element Analysis for machine design, through simulation and co-simulation techniques for power electronics and controls evaluation, and finally system design, fabrication, testing and evaluation. If this project successfully achieves and demonstrates the DOE targets for power density, cost, and reliability, the technology has the potential to become a core enabler of the flagship higher power product portfolio in commercial traction businesses, which has so far been confined to DC, induction, Brush Less DC (BLDC), Permanent Magnet AC (PMAC), and reluctance machines.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Snapshots of Ce 70 Toroid Assembly from Solids and Solution

Crystallization at the solid–liquid interface is difficult to spectroscopically observe and therefore challenging to understand and ultimately control at the molecular level. The Ce70-torroid formulated [Ce IV 70 (OH) 36 (O) 64 (SO 4 ) 60 (H 2 O) 10 ] 4– , part of a larger emerging family of M IV 70 -materials (M = Zr, U, Ce), presents such an opportunity. We elucidated assembly mechanisms by the X-ray scattering (small-angle scattering and total scattering) of solutions and solids as well as crystallizing and identifying fragments of Ce 70 by single-crystal X-ray diffraction. Fragments show evidence for templated growth (Ce 5 , [Ce 5 (O) 3 (SO 4 ) 12 ] 10- ) and modular assembly from hexamer (Ce 6 ) building units (Ce 13 , [Ce 13 (OH) 6 (O) 12 (SO 4 ) 14 (H 2 O) 14 ] 6– and Ce 62 , [Ce 62 (OH) 30 (O) 58 (SO 4 ) 58 ] 14- ). Ce 62 , an almost complete ring, precipitates instantaneously in the presence of ammonium cations as two torqued arcs that interlock by hydrogen boding through NH 4 + , a structural motif not observed before in inorganic systems. The room temperature rapid assemblies of both Ce 70 and Ce 62 , respectively, by the addition of Li + and NH 4 + , along with ion-exchange and redox behavior, invite exploitation of this emerging material family in environmental and energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Neural network model of neutral beam injection in the EAST tokamak to enable fast transport simulations

The neutral beam injection (NBI) system in EAST produces energetic neutral particles, which collide with electrons and ions in tokamak plasmas and heat the plasmas through Coulomb collisions. Moreover, it drives a non-inductive source of current, due to the charge-exchange collision between neutral particles and ions, and injects toroidal torque, which generates a toroidal rotation of the plasma. The effect caused by the NBI system, such as plasma heating, current drive, total neutron rate, momentum transfer, and shine-through, are modeled by a comprehensive module called NUBEAM. However, NUBEAM is computationally intensive since it relies on Monte Carlo methods. In this work, a neural network model has been developed as a surrogate model for NUBEAM in EAST. The database for neural-network model training, validation and testing is generated by running TRANSP for experimental discharges from recent EAST campaigns (after the latest NBI upgrade) while using the NUBEAM module. Simulation results illustrate that the trained neural network has the capability of replicating the predictions made by NUBEAM while demanding a significantly shorter execution time. Finally, these results indicate that surrogate models like the one proposed in this work could enable fast transport simulations for EAST after integrating them into a control-oriented predictive code such as COTSIM.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗