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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Historical (1700–2012) Global Multi-Model Estimates of the Fire Emissions from the Fire Modeling Intercomparison Project (FireMIP)

Fire emissions are critical for carbon and nutrient cycles, climate, and air quality. Dynamic Global Vegetation Models (DGVMs) with interactive fire modeling provide important estimates for long-term and large-scale changes of fire emissions. Here we present the first multi-model estimates of global gridded historical fire emissions for 1700-2012, including carbon and 33 species of trace gases and aerosols. The dataset is based on simulations of nine DGVMs with different state-of-the-art global fire models that participated in the Fire Modeling Intercomparison Project (FireMIP), using the same and standardized protocols and forcing data, and the most up-to-date fire emission factor table from field and laboratory studies over various land cover types. We evaluate the simulations of present-day fire emissions by comparing them with satellite-based products. Evaluation results show that most DGVMs simulate present-day global fire emission totals within the range of satellite-based products, and can capture the high emissions over the tropical savannas, low emissions over the arid and sparsely vegetated regions, and the main features of seasonality. However, most of the models fail to simulate the interannual variability, partly due to a lack of modeling peat fires and tropical deforestation fires. Historically, all models show only a weak trend in global fire emissions before ~1850s, consistent with multi-source merged historical reconstructions. The long-term trends among DGVMs are quite different for the 20th century, with some models showing an increase and others a decrease in fire emissions, mainly as a result of the discrepancy in their simulated responses to human population density change and land-use and land-cover change (LULCC). Our study provides a basic dataset for developing regional and global multi-source merged historical reconstructions and merging methods, and analyzing historical changes of fire emissions and their uncertainties as well as their role in the Earth system. It also highlights the importance of accurately modeling the responses of fire emissions to LULCC and population density change in reducing uncertainties in historical reconstructions of fire emissions and providing more reliable future projections.

Li, Fang↗
NASA NTRS2017

Historic Global Biomass Burning Emissions for CMIP6 (BB4CMIP) Based on Merging Satellite Observations with Proxies and Fire Models (1750-2015)

Fires have influenced atmospheric composition and climate since the rise of vascular plants, and satellite data has shown the overall global extent of fires. Our knowledge of historic fire emissions has progressively improved over the past decades due mostly to the development of new proxies and the improvement of fire models. Currently there is a suite of proxies including sedimentary charcoal records, measurements of fire-emitted trace gases and black carbon stored in ice and firn, and visibility observations. These proxies provide opportunities to extrapolate emissions estimates based on satellite data starting in 1997, but each proxy has strengths and weaknesses regarding, for example, the spatial and temporal extents over which they are representative. We developed a new historic biomass burning emissions dataset starting in 1750 that merges the satellite record with several existing proxies, and uses the average of six models from the Fire Model Intercomparison Project (FireMIP) protocol to estimate emissions when the available proxies had limited coverage. According to our approach, global biomass burning emissions were relatively constant with 10-year averages varying between 1.8 and 2.3 petagrams of carbon per year. Carbon emissions increased only slightly over the full time period and peaked during the 1990's after which they decreased gradually. There is substantial uncertainty in these estimates and patterns varied depending on choices regarding data representation, especially on regional scales. The observed pattern in fire carbon emissions is for a large part driven by African fires, which accounted for 58 percent of global fire carbon emissions. African fire emissions declined since about 1950 due to conversion of savanna to cropland, and this decrease is partially compensated for by increasing emissions in deforestation zones of South America and Asia. These global fire emissions estimates are mostly suited for global analyses and will be used in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations.

Biomass burning; Satellite observations; computer ↗
NASA NTRS1978

Enclosure fire modeling

A fire characterization methodology is presented, which for the first time provides a unified analysis framework for the integration of all fire tests data on a common basis. Fire temperatures, smoke densities, toxic gas concentrations and heat fluxes to material properties, enclosure geometry, and ventilation factors are provided in this fire characterization approach. The fire characterization methodology was used to develop an enclosure fire hazards analysis procedure capable of predicting the probable course in fire prevention.

Coulbert, C. D.↗
NASA NTRS1996

Comparison of Fire Model Predictions with Experiments Conducted in a Hangar With a 15 Meter Ceiling

The purpose of this study is to examine the predictive capabilities of fire models using the results of a series of fire experiments conducted in an aircraft hangar with a ceiling height of about 15 m. This study is designed to investigate model applicability at a ceiling height where only a limited amount of experimental data is available. This analysis deals primarily with temperature comparisons as a function of distance from the fire center and depth beneath the ceiling. Only limited velocity measurements in the ceiling jet were available but these are also compared with those models with a velocity predictive capability.

MATHEMATICAL MODELS↗
NASA NTRS1981

Analysis of JP-4 fire test data and development of a simple fire model

A series of field experiments involving JP-4 fires of 7.6m dia and 15.2m dia was conducted under the sponsorship of NASA. The temperature inside the fire, the specie composition and vertical axial velocity were measured at several height locations and radial positions. The peak temperature recorded is 1400-1500 K; the velocities at 6m height are 11-12 m/s. The oxygen-to-nitrogen mass ratio along the vertical axis was found to be nearly a constant at 0.05. Significant necking of the fire was observed. A simple theoretical model was developed that predicts the experimental data on the velocity and vertical temperature distribution well. The model is based on the partial combustion of entrained air and assumed top-hat distributions for various property and flow parameters inside the fire. Quantitative agreement is obtained by using a value of 0.15 for the entrainment coefficient and 0.45 for the mixing efficiency factor. The model also predicts the fire necking.

Raj, P. K.↗
NASA NTRS1977

Mathematical model of fires

Model allows predictions of future development of fire and can be used to evaluate different control methods at particular stages of fire. Five constraints considered are flame-spread rate, fuel-surface limit, airflow limit, quantity of fuel, original quantity of air.

Coulbert, C. D.↗
NASA NTRS1978

Model fire tests on polyphosphazene rubber and polyvinyl chloride (PVC)/nitrile rubber foams

A video tape record of model room fire tests was shown, comparing polyphosphazene (P-N) rubber and polyvinyl chloride (PVC)/nitrile rubber closed-cell foams as interior finish thermal insulation under conditions directly translatable to an actual fire situation. Flashover did not occur with the P-N foam and only moderate amounts of low density smoke were formed, whereas with the PVC/nitrile foam, flashover occurred quickly and large volumes of high density smoke were emitted. The P-N foam was produced in a pilot plant under carefully controlled conditions. The PVC/nitrile foam was a commercial product. A major phase of the overall program involved fire tests on P-N open-cell foam cushioning.

Widenor, W. M.↗
NASA NTRS1980

Analysis of NASA JP-4 fire tests data and development of a simple fire model

The temperature, velocity and species concentration data obtained during the NASA fire tests (3m, 7.5m and 15m diameter JP-4 fires) were analyzed. Utilizing the data analysis, a sample theoretical model was formulated to predict the temperature and velocity profiles in JP-4 fires. The theoretical model, which does not take into account the detailed chemistry of combustion, is capable of predicting the extent of necking of the fire near its base.

Raj, P.↗
NASA NTRSDate not supplied

Compartment Fire Modeling of a Crew Cabin in 1-g and Lunar-g

A fire inside a spacecraft poses one of the greatest dangers to the crew and mission success. As missions become more complex and longer in duration, the risk of a fire becomes more probable and catastrophic. A greater understanding of the effects of a fire inside a crewed vehicle at potential exploration atmospheres is needed. These exploration atmospheres, such as those being proposed for upcoming Lunar missions, include higher oxygen concentrations and lower pressures, also known as Normoxic conditions. Full scale fire testing, such as those performed during previous space programs, is the most straightforward way to obtain this understanding. These tests are difficult to implement in 1-g and even more challenging to attempt in Lunar-g. Modeling can help inform experiments aimed at determining flammability properties of common materials at exploration atmospheres, as well as determine the effect a fire has inside a spacecraft. A model can also be easily simulated in Lunar-g to predict the effect of gravity on fire propagation. This work focuses on a model of a theoretical partial crew cabin, with potential fire sources being a laptop and a Nomex sleeping bag. A simulation of the crew cabin during a high Heat Release Rate (HRR) fire and low HRR fire at 1-g was compared to simulations at Lunar-g. It was found that in both the low and high HRR cases, the temperature in the cabin was higher in the Lunar-g case than in the 1-g case. This is likely due to the hot products moving out the door of the crew cabin faster in the 1-g case. Modeling case studies like these will help guide future full-scale flammability experiments on Earth and allow for the prediction of fire spread in a Lunar gravity environment in order to design a safer crew cabin.

Fire Safety↗
NASA NTRS2010

Modeling Fire Severity in Black Spruce Stands in the Alaskan Boreal Forest Using Spectral and Non-Spectral Geospatial Data

Biomass burning in the Alaskan interior is already a major disturbance and source of carbon emissions, and is likely to increase in response to the warming and drying predicted for the future climate. In addition to quantifying changes to the spatial and temporal patterns of burned areas, observing variations in severity is the key to studying the impact of changes to the fire regime on carbon cycling, energy budgets, and post-fire succession. Remote sensing indices of fire severity have not consistently been well-correlated with in situ observations of important severity characteristics in Alaskan black spruce stands, including depth of burning of the surface organic layer. The incorporation of ancillary data such as in situ observations and GIS layers with spectral data from Landsat TM/ETM+ greatly improved efforts to map the reduction of the organic layer in burned black spruce stands. Using a regression tree approach, the R2 of the organic layer depth reduction models was 0.60 and 0.55 (pb0.01) for relative and absolute depth reduction, respectively. All of the independent variables used by the regression tree to estimate burn depth can be obtained independently of field observations. Implementation of a gradient boosting algorithm improved the R2 to 0.80 and 0.79 (pb0.01) for absolute and relative organic layer depth reduction, respectively. Independent variables used in the regression tree model of burn depth included topographic position, remote sensing indices related to soil and vegetation characteristics, timing of the fire event, and meteorological data. Post-fire organic layer depth characteristics are determined for a large (N200,000 ha) fire to identify areas that are potentially vulnerable to a shift in post-fire succession. This application showed that 12% of this fire event experienced fire severe enough to support a change in post-fire succession. We conclude that non-parametric models and ancillary data are useful in the modeling of the surface organic layer fire depth. Because quantitative differences in post-fire surface characteristics do not directly influence spectral properties, these modeling techniques provide better information than the use of remote sensing data alone.

Barrett, K.↗
NASA NTRS1979

Global enclosure fire modeling with applications

A brief review of LERC (Limiting Energy Release Criteria) is presented. Application of LERC to JSC/Boeing ignition source full-scale tests and to JSC/Dacfir math-model validation tests is outlined. It is concluded that: (1) a complete LERC application to the JSC/Boeing tests verifies the fuel load criterion as the limiting constraint; (2) the variability of magnitude and form of the results of repeated tests with and without small variations in parameters emphasizes the significance of the local flow, species concentration, and heat transfer distribution; and (3) weight loss measurements of recent JSC tests show consistent results with prior methods, fuel load constrained.

Stuart, J. W.↗
NASA NTRS2023

Marin County Wildfires Ii: Improving Fire Suppression Modeling to Inform Fire Prevention and Suppression Decisions in Marin County, Ca

A future of increased wildfires requires greater integration of spatial analysis and local knowledge of emergency responders. We examine the application of a Potential Operational Delineations (PODs) framework for strategic pre-fire planning in Marin County. PODs are spatial units for wildfire management that combine predictive modeling and local firefighter expertise to identify potential control locations as unit boundaries and assess the difficulty of suppression within units. Additionally, this project explores the integration of road networks and social vulnerability to assess environmental justice in evacuation safety. This project constitutes a novel application of the PODs framework as it integrates expertise from Marin County senior firefighters with a Fireline Location Model (FLM) to achieve POD definition and uses a Suppression Difficulty Score (SDS) to rank each POD. The FLM uses network analysis and hydrologic modeling to identify key roads and ridgelines as boundaries and combines them with expert knowledge, in the form of workshops, to construct PODs. Once identified, PODs are classified using SDS, which includes processed inputs such as LiDAR-derived aboveground biomass, ECOSTRESS Evaporative Stress Index, land use cover type from Sentinel-2 Imagery, and a digital elevation model. Environmental justice for evacuation safety incorporated three key road metrics such as connectivity, travel area, and exit capacity, the Social Vulnerability Index from the Center for Disease Control, and cell coverage to determine a final Evacuation Difficulty Score. Results indicate a strong link between road networks as primary POD boundaries, with ridgelines and waterways as secondary and tertiary locations. Specifically, we find 78.5% of expertise-identified POD boundaries align with FLM-determined boundaries. More validation is needed to support this process; however, initial results signal a feasible framework to integrate expertise and spatial analysis in local level strategic fire planning

Wildfire modeling↗
NASA NTRS1979

Enclosure fire dynamics model

A practical situation of an enclosure fire is presented and why the need for a fire dynamic model is addressed. The difficulties in establishing a model are discussed, along with a brief review of enclosure fire models available. The approximation of the practical situation and the model developed are presented.

Bellan, J.↗
NASA NTRS2014

Quantitative Risk Modeling of Fire on the International Space Station

The International Space Station (ISS) Program has worked to prevent fire events and to mitigate their impacts should they occur. Hardware is designed to reduce sources of ignition, oxygen systems are designed to control leaking, flammable materials are prevented from flying to ISS whenever possible, the crew is trained in fire response, and fire response equipment improvements are sought out and funded. Fire prevention and mitigation are a top ISS Program priority - however, programmatic resources are limited; thus, risk trades are made to ensure an adequate level of safety is maintained onboard the ISS. In support of these risk trades, the ISS Probabilistic Risk Assessment (PRA) team has modeled the likelihood of fire occurring in the ISS pressurized cabin, a phenomenological event that has never before been probabilistically modeled in a microgravity environment. This paper will discuss the genesis of the ISS PRA fire model, its enhancement in collaboration with fire experts, and the results which have informed ISS programmatic decisions and will continue to be used throughout the life of the program.

Castillo, Theresa↗
NASA NTRS1990

Verification of the naval oceanic vertical aerosol model during FIRE

The value of Naval Oceanic Vertical Aerosol Model (NOVAM) is illustrated for estimating the non-uniform and non-logarithmic extinction profiles, based on a severe test involving conditions close to and beyond the limits of applicability of NOVAM. A more comprehensive evaluation of NOVAM from the FIRE data is presented, which includes a clear-air case. For further evaluation more data are required on the vertical structure of the extinction in the marine atmospheric boundary layer (MABL), preferably for different meteorological conditions and in different geographic areas (e.g., ASTEX).

Davidson, K. L.↗