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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Impact of Control on Availability and Cycling of Residential HVAC in a Real-World Experiment

Demand response is an important emerging part of smart grids and there is a large stream of research from theoretical and modeling perspectives. However, there is relatively little experimental evidence that could help researchers and building operators make informed decisions on best practices for modeling, developing, and deployment of control mechanisms. We contribute to the body of experimental research by providing numerical insights into the role and availability of residential HVAC systems for control. We share the findings on the duration of the cooling cycle, off cycle, and temperature settling time of HVAC systems from data collected from a smart neighborhood located in Atlanta, GA.

cycling↗
DOE OSTI2021

Describing the Mechanism of Instability Suppression Using a Central Pilot Flame With Coupled Experiments and Simulations

Pilot flames are commonly used to extend combustor operability limits and suppress combustion oscillations in low-emissions gas turbines. Combustion oscillations, a coupling between heat release rate oscillations and combustor acoustics, can arise at the operability limits of low-emissions combustors where the flame is more susceptible to perturbations. While the use of pilot flames is common in land-based gas turbine combustors, the mechanism by which they suppress instability is still unclear. In this study, we consider the impact of a central jet pilot on the stability of a swirl-stabilized flame in a variable-length, single-nozzle combustor. Previously, the pilot flame was found to suppress the instability for a range of equivalence ratios and combustor lengths. We hypothesize that combustion oscillation suppression by the pilot occurs because the pilot provides hot gases to the vortex breakdown region of the flow that recirculate and improve the static, and hence dynamic, stability of the main flame. This hypothesis is based on a series of experimental results that show that pilot efficacy is a strong function of pilot equivalence ratio but not pilot flow rate, which would indicate that the temperature of the pilot products as well as the combustion intensity of the pilot flame play more of a role in oscillation stabilization than the length of the pilot flame relative to the main flame. Further, the pilot-flame efficacy increases with pilot-flame equivalence ratio until it matches the main-flame equivalence ratio; at pilot equivalence ratios greater than the main equivalence ratio, the pilot-flame efficacy does not change significantly with pilot equivalence ratio. To understand these results, we use large-eddy simulation (LES) to provide a detailed analysis of the flow in the region of the pilot flame and the transport of radical species in the region between the main flame and pilot flame. Furthermore, the simulation, using a flamelet/progress variable-based chemistry tabulation approach and standard eddy viscosity/diffusivity turbulence closure models, provides detailed information that is inaccessible through experimental measurements.

42 ENGINEERING↗
DOE OSTI2024

The EGS Collab Project – Summaries of Experiments 2 and 3: Experiments at 1.25 km depth at the Sanford Underground Research Facility

The EGS Collab project performed well-monitored rock stimulation and flow tests at the 10-m scale in an underground research laboratory to inform challenges in implementing enhanced geothermal system (EGS) technology. This project, supported by the US Department of Energy, gathered data and observations from the field tests and compared these to simulation results to understand processes and to build confidence in numerical modeling of the processes.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

The pNab experiment and the quest for ever better neutron beam polarization

The Nab and pNAB collaborations are conducting a program of studies of free neutron beta decay, with the primary goal of testing the unitarity of the Cabbibo-Kobayashi-Maskawa matrix that describes quark mixing due to the weak interaction. For this purpose, a large, novel electromagnetic spectrometer, the Nab spectrometer, has been designed, built, and placed in use to determine the correlation coefficients in unpolarized neutron beta decay: "a", the neutrino-electron correlation coefficient; and "b", the Fierz term. The subject of this paper is pNAB, the second phase of the program, that will deploy the same spectrometer with a polarized neutron beam to determine "A", the beta asymmetry; and "B", the neutrino asymmetry coefficients. A focus of this paper will be on the strategies to provide a high and precisely known neutron beam polarization.

Baessler, Stefan↗