In March 2005, the United States Coast Guard requested that Sandia National Laboratories provide a technical review and evaluation of the appropriateness and completeness of models, assumptions, analyses, and risk management options presented in the Cabrillo Port LNG Deepwater Port Independent Risk Assessment-Revision 1 (Cabrillo Port IRA). The goal of Sandia's technical evaluation of the Cabrillo Port IRA was to assist the Coast Guard in ensuring that the hazards to the public and property from a potential LNG spill during transfer, storage, and regasification operations were appropriately evaluated and estimated. Sandia was asked to review and evaluate the Cabrillo Port IRA results relative to the risk and safety analysis framework developed in the recent Sandia report, ''Guidance on Risk Analysis and Safety Implications of a Large Liquefied Natural Gas (LNG) Spill over Water''. That report provides a framework for assessing hazards and identifying approaches to minimize the consequences to people and property from an LNG spill over water. This report summarizes the results of the Sandia review of the Cabrillo Port IRA and supporting analyses. Based on our initial review, additional threat and hazard analyses, consequence modeling, and process safety considerations were suggested. The additional analyses recommended were conducted by the Cabrillo Port IRA authors in cooperation with Sandia and a technical review panel composed of representatives from the Coast Guard and the California State Lands Commission. The results from the additional analyses improved the understanding and confidence in the potential hazards and consequences to people and property from the proposed Cabrillo Port LNG Deepwater Port Project. The results of the Sandia review, the additional analyses and evaluations conducted, and the resolutions of suggested changes for inclusion in a final Cabrillo Port IRA are summarized in this report.
While recognized standards exist for the systematic safety analysis of potential spills or releases from LNG (Liquefied Natural Gas) storage terminals and facilities on land, no equivalent set of standards or guidance exists for the evaluation of the safety or consequences from LNG spills over water. Heightened security awareness and energy surety issues have increased industry's and the public's attention to these activities. The report reviews several existing studies of LNG spills with respect to their assumptions, inputs, models, and experimental data. Based on this review and further analysis, the report provides guidance on the appropriateness of models, assumptions, and risk management to address public safety and property relative to a potential LNG spill over water.
Fires in aircraft engine nacelles must be rapidly suppressed to avoid loss of life and property. The design of new and retrofit suppression systems has become significantly more challenging due to the ban on production of Halon 1301 for environmental concerns. Since fire dynamics and the transport of suppressants within the nacelle are both largely determined by the available air flow, efforts to define systems using less effective suppressants greatly benefit from characterization of nacelle air flow fields. A combined experimental and computational study of nacelle air flow therefore has been initiated. Calculations have been performed using both CFD-ACE (a Computational Fluid Dynamics (CFD) model with a body-fitted coordinate grid) and VULCAN (a CFD-based fire field model with a Cartesian "brick" shaped grid). A quarter-scale test fixture was designed and fabricated for the purpose of obtaining spatially-resolved measurements of velocity and turbulence intensity in a smooth nacelle. Numerical calculations have been performed for the conditions of the experiment and comparisons with experimental results obtained from the quarter-scale test fixture are discussed. In addition, numerical simulations were performed to assess the sensitivity of the predictions to the grid size and to the turbulence models with and without wall functions. In general, the velocity predictions show very good agreement with the data in the center of the channel but deviate near the walls. The turbulence intensity results tend to amplify the differences in velocity, although most of the trends are in agreement. In addition, there were some differences between VULCAN and CFD-ACE results in the angled wall regions due to the Cartesian grid structure used by the VULCAN code. Also, the experimental data tended to show poorer resolution near the walls of the transition ducts. The increased uncertainty in the data highlights some of the challenges in getting data near the walls due to the low signal to noise ratio. Overall, this effort provided a benchmark case for both the VULCAN and CFD-ACE codes for the application of interest.
As part of the full scale fuel fire experimental program, a series of JP-8 pool fire experiments with a large cylindrical calorimeter (3.66 m diameter), representing a C-141 aircraft fuselage, at the lee end of the fuel pool were performed at Naval Air Warfare Center, Weapons Division (NAWCWPNS). The series was designed to support Weapon System Safety Assessment (WSSA) needs by addressing the case of a transport aircraft subjected to a large fuel fire. The data collected from this mock series will allow for characterization of the fire environment via a survivable test fixture. This characterization will provide important background information for a future test series utilizing the same fuel pool with an actual C-141 aircraft in place of the cylindrical calorimeter.
A gridless technique for the solution of the integral form of the radiative heat flux equation for emitting and absorbing media is presented. Treatment of non-uniform absorptivity and gray boundaries is included. As part of this work, the authors have developed fast multipole techniques for extracting radiative heat flux quantities from the temperature fields of one-dimensional and three-dimensional geometries. Example calculations include those for one-dimensional radiative heat transfer through multiple flame sheets, a three-dimensional enclosure with black walls, and an axisymmetric enclosure with black walls.
Smoke is known to cause electrical equipment failure, but the likelihood of immediate failure during a fire is unknown. Traditional failure assessment techniques measure the density of ionic contaminants deposited on surfaces to determine the need for cleaning or replacement of electronic equipment exposed to smoke. Such techniques focus on long-term effects, such as corrosion, but do not address the immediate effects of the fire. This document reports the results of tests on the immediate effects of smoke on electronic equipment. Various circuits and components were exposed to smoke from different fields in a static smoke exposure chamber and were monitored throughout the exposure. Electrically, the loss of insulation resistance was the most important change caused by smoke. For direct current circuits, soot collected on high-voltage surfaces sometimes formed semi-conductive soot bridges that shorted the circuit. For high voltage alternating current circuits, the smoke also tended to increase the likelihood of arcing, but did not accumulate on the surfaces. Static random access memory chips failed for high levels of smoke, but hard disk drives did not. High humidity increased the conductive properties of the smoke. The conductivity does not increase linearly with smoke density as first proposed; however, it does increase with quantity. The data can be used to give a rough estimate of the amount of smoke that will cause failures in CMOS memory chips, dc and ac circuits. Comparisons of this data to other fire tests can be made through the optical and mass density measurements of the smoke.
A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.
Scattering to extinction cross-section ratios, {rho}{sub se} were measured using the NIST Large Agglomerate Optics Facility for soot produced from ethene and acetylene laminar diffusion flames. Measurements were performed using light sources at 543.5 nm, 632.8 nm and 856 nm. The average scattering to extinction cross-section ratios for these wavelengths are equal to 0.246, 0.196, and 0.196 for ethene and 0.316, 0.230, and 0.239 for acetylene. The 856 nm measurements represent the longest wavelength for which accurate scattering measurements have been performed for soot. The size distribution and fractal properties of the two soots were determined to assess the effects of limited acceptance angle range, finite size of the sensor, and departure from cosine response on the uncertainty in the measurement of {rho}{sub se} The expanded relative uncertainty (95% confidence level) was found to be {+-}6% at the two visible wavelengths and {+-}8% at 856 nm. Both the magnitude and wavelength dependence of {rho}{sub se} for the present experiments are significantly different from those reported by Krishnan et al. for overfire soot produced using a turbulent flame. The results are compared with the predictions of fractal optics.
A series of three 18.9 m diameter JP-4 pool fire experiments with a large (2.1 m X 4.6 m), flat plate calorimeter adjacent to the fuel pool were recently performed. The objectives of these experiments were to: (1) gain a better understanding of fire phenomenology, (2) provide empirical input parameter estimates for simplified, deterministic Risk Assessment Compatible Fire Models (RACFMs), (3) assist in continuing fire field model code validation and development, and (4) enhance the data base of fire temperature and heat flux to object distributions. Due to different wind conditions during each experiment, data were obtained for conditions where the plate was not engulfed, fully-engulfed and partially engulfed by the continuous flame zone. Results include the heat flux distribution to the plate and flame thermocouple temperatures in the vicinity of the plate and at two cross sections within the lower region of the continuous flame zone. The results emphasize the importance of radiative coupling (i.e. the cooling of the flames by a thermally massive object) and convective coupling (including object-induced turbulence and object/wind/flame interactions) in determining the heat flux from a fire to an object. The formation of a secondary flame zone on an object adjacent to a fire via convective coupling (which increases the heat flux by a factor of two) is shown to be possible when the object is located within a distance equal to the object width from the fire.
As part of a research program in fire science and technology at Sandia National Laboratories (SNL), an experimental and computational investigation of the fire phenomenology associated with the presence of a large (3.66 m diameter), fuselage-sized cylindrical calorimeter engulfed in a large (18.9 m diameter) JP-8 pool fire subjected to high (10.2 m/s) winds were performed. The conditions investigated here resulted in a twofold increase in the incident heat flux to the surface of the object relative to heat fluxes typical of large hydrocarbon fires without engulfed objects. Due to the enhanced fuel/air mixing, enhanced turbulence, and larger flame volume, the highest heat fluxes are observed on the leeward side of the calorimeter. Radiative heat fluxes of 150--250 kW/m{sup 2} on this side, with the maximum heat flux occurring near the top of the calorimeter, were measured. Radiative heat fluxes of 60--200 kW/m{sup 2} were measured on the windward side, with the highest heat flux near the bottom of the calorimeter. Measured and predicted heat fluxes to the pool surface of 25--90 kW/m{sup 2} were observed. The presence of the calorimeter tends to decrease the overall fuel consumption rate primarily due to redirection of the flame zone away from the pool surface. Overall, the numerical models does a reasonable job of representing the essential features of the fire environment but under predicts the heat flux to the calorimeter. These results emphasize the importance of considering the wind-induced interaction of fires and large objects when estimating the incident heat fluxes on a engulfed object. The measurements and analyses are of particular interest since few studies to date have addressed cases where the fire and object are of comparable size.
Full-scale fire characterization tests are becoming less frequent due to cost restrictions and environmental concerns. This trend, combined with significant advances in fire field modeling, has resulted in an increased effort to perform well-designed experiments which support the development and validation of numerical tools. In pursuit of improved fire characterization, large-fire measurement techniques in large-scale (D > 2m) fires are reviewed in this work. Primary attention is focused on the measurement of temperature and heat flux. Additional measurements of quantities such as soot volume fraction, soot emission temperature, and gas species are also addressed. Issues relating to the use of existing techniques, and methods for improving and interpreting the results from existing measurement techniques are presented. Alternate techniques for fire characterization and needs for development of advanced measurement technology are also briefly discussed.
Radiation in participating media is an important transport mechanism in many physical systems. The simulation of complex radiative transfer has not effectively exploited high-performance computing capabilities. In response to this need, a workshop attended by members active in the high-performance computing community, members active in the radiative transfer community, and members from closely related fields was held to identify how high-performance computing can be used effectively to solve the transport equation and advance the state-of-the-art in simulating radiative heat transfer. This workshop was held on March 29-30, 1994 in Albuquerque, New Mexico and was conducted by Sandia National Laboratories. The objectives of this workshop were to provide a vehicle to stimulate interest and new research directions within the two communities to exploit the advantages of high-performance computing for solving complex radiative heat transfer problems that are otherwise intractable.
When an object is subjected to the flow of combustion gas at a different temperature, the thermal responses of the object and the surrounding gas become coupled. The ability to model this interaction is of primary interest in the design of components which must withstand fire environments. One approach has been to decouple the problem and treat the incident flux on the surface of the object as being emitted from a blackbody at an approximate gas temperature. By neglecting the presence of the participating media, this technique overpredicts the heat fluxes initially acting on the object surface. The main goal of this work is to quantify the differences inherent in treating the combustion media as a blackbody as opposed to a gray gas. This objective is accomplished by solving the coupled participating media radiation and conduction heat transfer problem. A transient conduction analysis of a vertical flat plate was performed using a gray gas model to provide a radiation boundary condition. A 1-D finite difference algorithm was used to solve the conduction problem at locations along the plate. The results are presented in terms of nondimensional parameters and include both average and local heat fluxes as a function of time. Early in the transient, a reduction in net heat fluxes of up to 65% was observed for the gray gas results as compared to the blackbody cases. This reduction in the initial net heat flux results in lower surface temperatures for the gray gas case. Due to the initially reduced surface temperatures, the gray gas net heat flux exceeds the net blackbody heat flux with increasing time. For radiation Biot numbers greater than 5, or values of the radiation parameter less than 10-2, the differences inherent in treating the media as a gray gas are negligible and the blackbody assumption is valid. Overall, the results clearly indicate the importance of participating media treatment in the modeling of the thermal response of objects in fires and large combustion systems.