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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Charging Infrastructure Technologies: Development of a Multiport, >1 MW Charging System for Medium- and Heavy-Duty Electric Vehicles

Development of a Multiport, >1 MW Charging System for Medium- and Heavy-Duty Electric Vehicles project will develop research tools for a framework to design, optimize, and demonstrate key components of a multi-port 1+ MW medium-voltage connected charging system. The objectives of this effort are to develop strategies and technologies for multi-port 1+ MW grid-connected stations to recharge MD/HD electric vehicles at fast-charging travel plazas or at fleet depots; through industry engagement, charging station utilization and load analysis, grid impacts and interconnection analysis, detailed power electronics component design and controller demonstration, site and battery charge control design and controller demonstration; and charging connector design.

1+MW charging↗
DOE OSTI2022

Study of Inverter Control Strategies on the Stability of Microgrids Toward 100% Renewable Penetration: Preprint

This paper investigates microgrid transient stability with mixed generation - synchronous generator (SG), grid-forming (GFM) and grid-following (GFL) inverters - under increasing penetration levels toward a 100% renewable generation microgrid. Specifically, the dynamics of a microgrid with an SG and GFL inverter(s), an SG with GFM inverter(s), and an SG with GFM and GFL inverters under each penetration are evaluated with an electromagnetic transient study with two critical dynamic events: unplanned islanding and switching in a pumped induction motor load. Analysis and simulation results indicate that the microgrid with GFL inverters running in parallel with the SG can provide a faster power response than the GFM inverters to compensate for the deviations of the frequency and voltage. The scenario with the mixed SG, GFM, and GFL inverter has the best transient and steady-state stability toward 100% inverter-based resource (IBR) penetration. This comprehensive study provides helpful references for microgrid engineers to understand the microgrid stability when facing various choice of installing IBRs (GFL, GFM, or mixed).

droop control↗
DOE OSTI2022

Study of Inverter Control Strategies on the Stability of Microgrids Toward 100% Renewable Penetration

This paper investigates microgrid transient stability with mixed generation - synchronous generator (SG), grid-forming (GFM) and grid-following (GFL) inverters - under increasing penetration levels toward a 100% renewable generation microgrid. Specifically, the dynamics of a microgrid with an SG and GFL inverter(s), an SG with GFM inverter(s), and an SG with GFM and GFL inverters under each penetration are evaluated with an electromagnetic transient study with two critical dynamic events: unplanned islanding and switching in a pumped induction motor load. Analysis and simulation results indicate that the microgrid with GFL inverters running in parallel with the SG can provide a faster power response than the GFM inverters to compensate for the deviations of the frequency and voltage. The scenario with the mixed SG, GFM, and GFL inverter has the best transient and steady-state stability toward 100% inverter-based resource (IBR) penetration. This comprehensive study provides helpful references for microgrid engineers to understand the microgrid stability when facing various choice of installing IBRs (GFL, GFM, or mixed).

droop control↗
DOE OSTI2022

Artificial intelligence based analysis of nanoindentation load–displacement data using a genetic algorithm

In this work, we developed an automated tool, Nanoindentation Neo package for the analysis of nanoindentation load–displacement curves using a Genetic Algorithm (GA) applied to the Oliver-Pharr method (Oliver et al.,1992). For some materials, such as polycrystalline isotropic graphites, Least Squares Fitting (LSF) of the unload curve can produce unrealistic fit parameters. These graphites exhibit sharply peaked unloading curves not easily fit using the LSF, which tends to overestimate the indenter tip geometry parameter. To tackle this problem, we extended our general materials characterization tool Neo for EXAFS analysis (Terry et al., 2021) to fit nanoindentation data. Nanoindentation Neo automatically processes and analyzes nanoindentation data with minimal user input while producing meaningful fit parameters. GA, a robust metaheuristic method, begins with a population of temporary solutions using model parameters called chromosomes; from these we evaluate a fitness value for each solution, and select the best solutions to mix with random solutions producing the next generation. A mutation operator then modifies existing solutions by random perturbations, and the optimal solution is selected. We tested the GA method using Silica and Al reference standards. We fit samples of graphite and a high entropy alloy (HEA) consisting of BCC and FCC phases.

42 ENGINEERING↗
NASA NTRS2013

Alternate Methods in Refining the SLS Nozzle Plug Loads

Numerical analysis has shown that the SLS nozzle environmental barrier (nozzle plug) design is inadequate for the prelaunch condition, which consists of two dominant loads: 1) the main engines startup pressure and 2) an environmentally induced pressure. Efforts to reduce load conservatisms included a dynamic analysis which showed a 31% higher safety factor compared to the standard static analysis. The environmental load is typically approached with a deterministic method using the worst possible combinations of pressures and temperatures. An alternate probabilistic approach, utilizing the distributions of pressures and temperatures, resulted in a 54% reduction in the environmental pressure load. A Monte Carlo simulation of environmental load that used five years of historical pressure and temperature data supported the results of the probabilistic analysis, indicating the probabilistic load is reflective of a 3-sigma condition (1 in 370 probability). Utilizing the probabilistic load analysis eliminated excessive conservatisms and will prevent a future overdesign of the nozzle plug. Employing a similar probabilistic approach to other design and analysis activities can result in realistic yet adequately conservative solutions.

Burbank, Scott↗
NASA NTRS1987

Efficient 3-D finite element failure analysis of compression loaded angle-ply plates with holes

Finite element stress analysis and the tensor polynomial failure criterion predict that failure always initiates at the interface between layers on the hole edge for notched angle-ply laminates loaded in compression. The angular location of initial failure is a function of the fiber orientation in the laminate. The dominant stress components initiating failure are shear. It is shown that approximate symmetry can be used to reduce the computer resources required for the case of unaxial loading.

Burns, S. W.↗
DOE OSTI2023

Cost-Benefit Analysis of Grid-Supportive Loads for Fast Frequency Response

Flexibility in inverter-based loads could be used to support the converter-dominated power grid by offering a rapid, autonomous, and adjustable power reserve during system transients to help maintain system stability. Based on technical potential, ancillary service (AS) value, and implementation costs, this study illustrates the cost-benefit analysis of grid-supportive loads (GSLs) for the supply of fast frequency response (FFR). The net benefit for each GSL is demonstrated using a case study and relevant data sources. The findings suggest that implementation costs for enabling GSL features are low compared to the value that grid operators get from the acquisition of responsive reserve services. The authors believe that, given the rising popularity of renewable energy sources, GSLs can be a useful tool for grid stability in low-inertia systems.

cost-benefit analysis↗
NASA NTRS1991

A method for the geometrically nonlinear analysis of compressively loaded prismatic composite structures

A method was developed for the geometrically nonlinear analysis of the static response of thin-walled stiffened composite structures loaded in uniaxial or biaxial compression. The method is applicable to arbitrary prismatic configurations composed of linked plate strips, such as stiffened panels and thin-walled columns. The longitudinal ends of the structure are assumed to be simply supported, and geometric shape imperfections can be modeled. The method can predict the nonlinear phenomena of postbuckling strength and imperfection sensitivity which are exhibited by some buckling-dominated structures. The method is computer-based and is semi-analytic in nature, making it computationally economical in comparison to finite element methods. The method uses a perturbation approach based on the use of a series of buckling mode shapes to represent displacement contributions associated with nonlinear response. Displacement contributions which are of second order in the model amplitudes are incorported in addition to the buckling mode shapes. The principle of virtual work is applied using a finite basis of buckling modes, and terms through the third order in the model amplitudes are retained. A set of cubic nonlinear algebraic equations are obtained, from which approximate equilibrium solutions are determined. Buckling mode shapes for the general class of structure are obtained using the VIPASA analysis code within the PASCO stiffened-panel design code. Thus, subject to some additional restrictions in loading and plate anisotropy, structures which can be modeled with respect to buckling behavior by VIPASA can be analyzed with respect to nonlinear response using the new method. Results obtained using the method are compared with both experimental and analytical results in the literature. The configurations investigated include several different unstiffened and blade-stiffening panel configurations, featuring both homogeneous, isotropic materials, and laminated composite material.

Stoll, Frederick↗
NASA NTRSDate not supplied

Structural Analysis of Load-Bearing Components in Mars Science Helicopter

The successful demonstration of powered flight on Mars by Ingenuity has led to the development of next generation Martian rotorcraft. As technology advances from a technology demonstrator to possible expanded planetary science investigations, the potential to fly a high payload carrying rotorcraft relies on the capability to analyze and validate the structural integrity of the vehicle in addition to the rotor aerodynamic performance. The Mars Science Helicopter (MSH), a next generation hexacopter concept, is one example of a proposed vehicle that would perform science independently of a land-based vehicle. To ensure the feasibility and viability of MSH mission performance, it is critical to mature the structural design for these vehicle concepts to bridge the gap between the best practices of the spacecraft and aircraft communities. MSH was analyzed under operational and 26G quasi-static launch loads with different rotor arm and fuselage designs. Structural analysis results showed that rotor arms could be stiffened for significantly improved structural performance with minimal mass penalty, while the rotorcraft frame exhibited a more complex relationship between mass and launch load stresses due to the mass-dependent launch loads.

Load-Bearing↗
NASA NTRS1990

Nonlinear analysis of compressively loaded linked-plate structures

A method is presented for the geometrically nonlinear analysis of the equilibrium behavior of a general class of compressively loaded, prismatic, linked-plate structures. The semi-analytical method accounts for geometric shape imperfections, and allows the use of laminated composite plate properties. Buckling eigenfunctions are used as displacement shape functions, and the associated second-order displacement fields are incorporated. The nonlinear plate equilibrium equations are expressed in terms of the assumed displacement form, and the Galerkin method is used to obtain a set of algebraic equations which are nonlinear in the modal amplitudes and the load parameter. Buckling eigensolutions for the class of structures under consideration can be obtained from the VIPASA computer code; thus, subject to some additional restrictions in loading and plate anisotropy, structural configurations which can be analyzed with regard to buckling response by VIPASA can be analyzed with regard to geometrically nonlinear response using the new method.

Stoll, Frederick↗
NASA NTRS2009

Nozzle Side Load Testing and Analysis at Marshall Space Flight Center

Realistic estimates of nozzle side loads, the off-axis forces that develop during engine start and shutdown, are important in the design cycle of a rocket engine. The estimated magnitude of the nozzle side loads has a large impact on the design of the nozzle shell and the engine s thrust vector control system. In 2004 Marshall Space Flight Center (MSFC) began developing a capability to quantify the relative magnitude of side loads caused by different types of nozzle contours. The MSFC Nozzle Test Facility was modified to measure nozzle side loads during simulated nozzle start. Side load results from cold flow tests on two nozzle test articles, one with a truncated ideal contour and one with a parabolic contour are provided. The experimental approach, nozzle contour designs and wall static pressures are also discussed

Ruf, Joseph H.↗
DOE OSTI2020

Probabilistic analysis of masked loads with aggregated photovoltaic production

In this paper we present a probabilistic analysis framework to estimate behind-the-meter photovoltaic generation in real time. We develop a forward model consisting of a spatiotemporal stochastic process that represents the photovoltaic generation and a stochastic differential equation with jumps that represents the demand. Here, we employ this model to disaggregate the behind-the-meter photovoltaic generation using net load and irradiance measurements.

14 SOLAR ENERGY↗
NASA NTRS2025

Structural Analysis of Load-Bearing Components in Mars Science Helicopter

The successful demonstration of powered flight on Mars by Ingenuity has led to the development of next generation Martian rotorcraft. As technology advances from a technology demonstrator to possible expanded planetary science investigations, the potential to fly a high payload carrying rotorcraft relies on the capability to analyze and validate the structural integrity of the vehicle in addition to the rotor aerodynamic performance. The Mars Science Helicopter (MSH), a next generation hexacopter concept, is an example of a proposed vehicle that would perform science investigations independent of a land-based vehicle. To ensure the feasibility and viability of MSH mission performance, it is critical to mature the structural design of vehicle concepts to bridge the gap between the best practices of the spacecraft and aircraft communities. MSH was analyzed under operational and 26G quasi-static launch loads with different rotor arm and frame designs. Structural analysis results showed that rotor arms could be stiffened for significantly improved structural performance with minimal mass penalty, while the rotorcraft frame exhibited a more complex relationship between mass and launch load stresses due to the mass-dependent launch loads.

Vehicle↗
NASA NTRS1993

Improvements to a method for the geometrically nonlinear analysis of compressively loaded stiffened composite panels

The NLPAN computer code uses a finite-strip approach to the analysis of thin-walled prismatic composite structures such as stiffened panels. The code can model in-plane axial loading, transverse pressure loading, and constant through-the-thickness thermal loading, and can account for shape imperfections. The NLPAN code represents an attempt to extend the buckling analysis of the VIPASA computer code into the geometrically nonlinear regime. Buckling mode shapes generated using VIPASA are used in NLPAN as global functions for representing displacements in the nonlinear regime. While the NLPAN analysis is approximate in nature, it is computationally economical in comparison with finite-element analysis, and is thus suitable for use in preliminary design and design optimization. A comprehensive description of the theoretical approach of NLPAN is provided. A discussion of some operational considerations for the NLPAN code is included. NLPAN is applied to several test problems in order to demonstrate new program capabilities, and to assess the accuracy of the code in modeling various types of loading and response. User instructions for the NLPAN computer program are provided, including a detailed description of the input requirements and example input files for two stiffened-panel configurations.

Stoll, Frederick↗