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Results for “Performance optimization”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Comparison of Candidate Designs and Performance Optimization for an Electric Traction Motor Targeting 50 kW/L Power Density

The continued expansion of the global electric vehicle fleet is accompanied by an unprecedented demand for high power density electric traction motors. With the ambitious U.S. DRIVE 2025 target of 50 kW/L power density and an equally aggressive cost reduction goal, innovative approaches have to be utilized in terms of both the design and manufacturing of electric traction motors. In this paper, six motor options are compared and the best design is picked for each option to investigate the drive and excitation requirements and the weighted power efficiency over multiple load points, with necessary mechanical stress and demagnetization checks. State-of-the-art winding technologies, including high slot fill die compressed windings and hairpin windings, and rotors both with permanent magnet (PM) and PM-free are incorporated. The design of high flux density and low harmonic content magnetic field is also demonstrated.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Loss Analysis and Performance Optimization Pathways of 729-mV Voc Si Solar Cells with Poly-Si on Locally-Etched Dielectric Passivating Contacts

In this article, the loss analysis of silicon solar cells with polysilicon on locally-etched dielectric passivating contacts with Voc=729.0 mV and efficiency=22.6% has been presented. Experimentally, nano-pinholes were introduced in SiO x (2.2 nm) and SiO x /SiN y (2.2 nm/8nm) stack using metal-assisted chemical etching (MACE). SunSolve and Quokka3 were used to simulate the experimental solar cell and investigate the optical and electrical power losses. Simulations suggest maximum power loss occurs due to recombination and resistive losses in the bulk (~0.76 mW/cm2) followed by power loss due to rear contact recombination (~0.35 mW/cm2). Recombination at the front surface also contributes to 0.24 mW/cm2. The effect of improving the bulk lifetime and lowering the recombination current density at the rear side on Voc, FF and hence, efficiency has been investigated. Further, advanced structures have been proposed to minimize recombination and parasitic absorption to achieve higher Voc and Jsc of the solar cells with locally-etched dielectric passivating contacts.

contacts↗
DOE OSTI2018

Effect of Dimensional Changes on Plasma Characteristics in Electrothermal Capillary Discharges for Optimized Performance in Fusion Pellet Injection

Geometrical changes in capillary discharges influence the plasma properties and can control exit parameters to certain desired values. For a fixed capillary radius of 2 mm and a 72-μs 43.9-kA peak discharge current, the plasma temperature is about 2.7 eV for different capillary lengths due to the constant input energy, while the number densities tend to saturate for capillary lengths greater than 12 cm. The electrical conductivity reaches 4.02 × 104 Ω{sup −1} m{sup −1} and then tends to saturate for 9-cm capillary length. The maximum bulk velocity at the capillary exit slightly increases with the increase in the capillary length from 6.15 to 6.26 km/s for lengths below 18 cm and decreases to 5.88 km/s for longer capillaries due to the higher amount of ablated mass and increased drag forces. For a 9-cm length with the same 72-μs 43.9-kA peak discharge current, the increase in the capillary radius reduces the energy density, which in turn reduces the total ablate mass, plasma density, electrical conductivity, and exit pressure. It is shown that the plasma temperature decreases from 4.6 to 2.1 eV by increasing the capillary radius and radiant heat flux also drops from 463 to 18.1 GW/m{sup 2}. The exit bulk velocity drops from 8.7 to 5.3 km/s as the radius increases from 0.5 to 3.6 mm, respectively. The design features of a capillary discharge can be adjusted for the radius and length, to produce specific plasma parameters for desired applications. Scaling laws relating exit peak plasma parameters to radius and length are obtained to facilitate quick estimate of plasma parameters. The validation of this model has been confirmed by confronting with experimental measurements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

High-performance optimization solver

HIOP is a HPC solver for solving certain optimization problems arising in mathematical optimization of systems described by partial-differential equations (POEs).

Cosmin, Petra↗
DOE OSTI2018

Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures

The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.

Liu, Zhicong↗
DOE OSTI2023

Optimizing Performance on Trinity Utilizing Machine Learning, Proxy Applications and Scheduling Priorities

The sheer number of nodes continues to increase in today’s supercomputers, the first half of Trinity alone contains more than 9400 compute nodes. Since the speed of today’s clusters are limited by the slowest nodes, it more important than ever to identify slow nodes, improve their performance if it can be done, and assure minimal usage of slower nodes during performance critical runs. This is an ongoing maintenance task that occurs on a regular basis and, therefore, it is important to minimize the impact upon its users by assessing and addressing slow performing nodes and mitigating their consequences while minimizing down time. These issues can be solved, in large part, through a systematic application of fast running hardware assessment tests, the application of Machine Learning, and making use of performance data to increase efficiency of large clusters. Proxy applications utilizing both MPI and OpenMP were developed to produce data as a substitute for long runtime applications to evaluate node performance. Machine learning is applied to identify underperforming nodes, and policies are being discussed to both minimize the impact of underperforming nodes and increase the efficiency of the system. In this paper, I will describe the process used to produce quickly performing proxy tests, consider various methods to isolate the outliers, and produce ordered lists for use in scheduling to accomplish this task.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Performant Optimization Strategies for Multifidelity Stochastic Power Grid Models

This talk goes into the algorithmic work done under the Forest project in order to solve expensive power grid models. We explore multiple fidelities of models that balance accuracy and computational expense. We use bundling strategies and progressive hedging in order to parallelize large stochastic programs.

Alfant, Rachael May [Sandia National Laboratories ↗
NASA NTRS1975

System analysis of a piston steam engine employing the uniflow principle, a study in optimized performance

Results are reported which were obtained from a mathematical model of a generalized piston steam engine configuration employing the uniflow principal. The model accounted for the effects of clearance volume, compression work, and release volume. A simple solution is presented which characterizes optimum performance of the steam engine, based on miles per gallon. Development of the mathematical model is presented. The relationship between efficiency and miles per gallon is developed. An approach to steam car analysis and design is presented which has purpose rather than lucky hopefulness. A practical engine design is proposed which correlates to the definition of the type engine used. This engine integrates several system components into the engine structure. All conclusions relate to the classical Rankine Cycle.

Peoples, J. A.↗