Self-ignition temperatures and flash points of some high-energy fuels
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Pusanski, Barbara↗
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Taguchi Experimental Design for Cleaning PWAs with Ball Grid Arrays
Ball grid arrays (BGAs), and other area array packages, are becoming more prominent as a way to increase component pin count while avoiding the manufacturing difficulties inherent in processing quad flat packs (QFPs)...Cleaning printed wiring assemblies (PWAs) with BGA components mounted on the surface is problematic...Currently, a low flash point semi-aqueous material, in conjunction with a batch cleaning unit, is being used to clean PWAs. The approach taken at JPL was to investigate the use of (1) semi-aqueous materials having a high flash point and (2) aqueous cleaning involving a saponifier.
ball grid array area array package semi-aqueous cl↗
Tribological Properties of a Pennzane(Registered Trademark)-Based Liquid Lubricant (Disubstituted Alkylated Cyclopentane) for Low Temperature Space Applications
The tribological properties of a disubstituted alkylated cyclopentane, Pennzane (registered) Synthesized Hydrocarbon Fluid X-1000, are presented. This compound is a lower molecular weight version of the commonly used multiply alkylated cyclopentane, Pennzane X-2000, currently used in many space mechanisms. New, lower temperature applications will require liquid lubricants with lower viscosities and pour points and acceptable vapor pressures. Properties reported include: friction and wear studies and lubricated lifetime in vacuum; additionally, typical physical properties (i.e., viscosity-temperature, pour point, flash and fire point, specific gravity, refractive index, thermal properties, volatility and vapor pressure) are reported.
Venier, Clifford↗
An Investigation of Flame Spread over Shallow Liquid Pools in Microgravity and Nonair Environments
Experiments of interest to combustion fundamentals and spacecraft fire safety investigated flame spread of alcohol fuels over shallow, 15 cm diameter pools in a 5.2 sec free-fall, microgravity facility. Results showed that, independent O2 concentration, alcohol fuel, and diluent types, microgravity flame spread rates were nearly identical to those corresponding normal-gravity flames for conditions where the normal gravity flames spread uniformly. This similarity indicated buoyancy-related convection in either phase does not affect flame spread, at least for the physical scale of the experiments. However, microgravity extinction coincided with the onset conditions for pulsating spread in normal gravity, implicating gas phase, buoyant flow as a requirement for pulsating spread. When the atmospheric nitrogen was replaced with argon, the conditions for the onset of normal-gravity pulsating flame spread and microgravity flame extinction were changed, in agreement with the expected lowering of the flash point through the thermal properties of the diluent. Helium-diluted flames, however, showed unexpected results with a shift to apparently higher flash-point temperatures and high normal gravity pulsation amplitudes.
Ross, Howard D.↗
An investigation of flame spread over shallow liquid pools in microgravity and nonair environments
Experiments of interest to combustion fundamentals and spacecraft fire safety investigated flame spread of alcohol fuels over shallow, 15 cm diameter pools in a 5.2 sec free-fall, microgravity facility. Results showed that, independent O2 concentrations, alcohol fuel, and diluent types, microgravity flame spread rates were nearly identical to those corresponding normal-gravity flames for conditions where the normal gravity flames spread uniformly. This similarity indicated buoyancy-related convection in either phase does not affect flame spread, at least for the physical scale of the experiments. However, microgravity extinction coincided with the onset conditions for pulsating spread in normal gravity, implicating gas phase, buoyant flow as a requirement for pulsating spread. When the atmospheric nitrogen was replaced with argon, the conditions for the onset of normal-gravity pulsating flame spread and microgravity flame extinction were changed, in agreement with the expected lowering of the flash point through the thermal properties of the diluent. Helium-diluted flames, however, showed unexpected results with a shift to apparently higher flash-point temperatures and high normal gravity pulsation amplitudes.
Ross, Howard D.↗
Techniques for determination of flash and fire points and impact sensitivity of materials in a gaseous oxygen environment
Flash points, fire points and impact sensitivity of materials under gaseous oxygen pneumatic and mechanical impact
Pippen, D. L.↗
Chemical and Physical Properties of Hi-Cal-2
As part of the Navy Project Zip to consider various boron-containing materials as possible high-energy fuels, the chemical and physical properties of Hi-Cal-2 prepared by the Callery Chemical Company were evaluated at the NACA Lewis laboratory. Elemental chemical analysis, heat of combustion, vapor pressure and decomposition, freezing point, density, self ignition temperature, flash point, and blow-out velocity were determined for the fuel. Although the precision of measurement of these properties was not equal to that obtained for hydrocarbons, this special release research memorandum was prepared to make the data available as soon as possible.
Spakowski, A. E.↗
Global Light System for JEM-EUSO
The Global Light System (GLS) is a network of ground-based Xenon flash lamps and steered UV lasers to validate the key functions of the JEM-EUSO instrument. These functions include triggering efficiency, the accuracy of intrinsic luminosity measurements, and the reconstructed pointing direction accuracy. GLS units will generate benchmark optical signatures in the atmosphere with similar characteristics to the optical signals of cosmic ray EASs. The lasers will generate tracks and the flashers will generate point flashes. But unlike air showers, the number, energy, precise time, direction (lasers) can be specified. JEM-EUSO will reconstruct the pointing directions of the lasers and the energy of the lasers and flash lamps to monitor the detector's triggers, and accuracy of energy and direction reconstruction. 12 GLS units will be deployed at selected sites around the globe. The JEM-EUSO footprint will pass over a GLS unit on average once per (near) moonless night under clear conditions for appropriately selected sites. The 12 units will be supplemented by campaign style measurements with an airborne unit that will be flown over the open ocean at selected altitudes under JEM-EUSO. A GLS prototype in an airplane will support a high-altitude balloon flight in 2014 of a proto-type JEM-EUSO telescope. We will describe the concept and system design and report on the status of prototyping and the selection process for candidates sites.
Christl, Mark↗
Visual phenomena induced by relativistic carbon ions with and without Cerenkov radiation
Exposing the human eye to individual carbon ions moving at relativistic speeds results in visual phenomena that include point flashes, streaks, and larger diffuse flashes. The diffuse flashes have previously been observed by astronauts in space but not in laboratory experiments with particles of high atomic number and energy. They are observed only when the nucleus moves fast enough to generate Cerenkov radiation.
Mcnulty, P. J.↗
Feasibility study of liquid pool burning in reduced gravity
The feasibility of conducting experiments in the Spacelab on ignition and flame spread with liquid fuel pools which are initially at a temperature lower than the fuel's flash point temperature was studied. Theories were developed for the ignition and flame spread processes, and experiments were conducted to understand the factors influencing the ignition process and the spread rate. The results were employed to devise a conceptual Spacelab experiment which is expected to be feasible for a safe conduct and to be suitable for obtaining crucial data on the concerned processes.
Kanury, A. M.↗
Fuels characterization studies
Current analytical techniques used in the characterization of broadened properties fuels are briefly described. Included are liquid chromatography, gas chromatography, and nuclear magnetic resonance spectroscopy. High performance liquid chromatographic ground-type methods development is being approached from several directions, including aromatic fraction standards development and the elimination of standards through removal or partial removal of the alkene and aromatic fractions or through the use of whole fuel refractive index values. More sensitive methods for alkene determinations using an ultraviolet-visible detector are also being pursued. Some of the more successful gas chromatographic physical property determinations for petroleum derived fuels are the distillation curve (simulated distillation), heat of combustion, hydrogen content, API gravity, viscosity, flash point, and (to a lesser extent) freezing point.
Seng, G. T.↗
Flame spread across liquid pools
For flame spread over liquid fuel pools, the existing literature suggests three gravitational influences: (1) liquid phase buoyant convection, delaying ignition and assisting flame spread; (2) hydrostatic pressure variation, due to variation in the liquid pool height caused by thermocapillary-induced convection; and (3) gas-phase buoyant convection in the opposite direction to the liquid phase motion. No current model accounts for all three influences. In fact, prior to this work, there was no ability to determine whether ignition delay times and flame spread rates would be greater or lesser in low gravity. Flame spread over liquid fuel pools is most commonly characterized by the relationship of the initial pool temperature to the fuel's idealized flash point temperature, with four or five separate characteristic regimes having been identified. In the uniform spread regime, control has been attributed to: (1) gas-phase conduction and radiation; (2) gas-phase conduction only; (3) gas-phase convection and liquid conduction, and most recently (4) liquid convection ahead of the flame. Suggestions were made that the liquid convection was owed to both vuoyancy and thermocapillarity. Of special interest to this work is the determination of whether, and under what conditions, pulsating spread can and will occur in microgravity in the absence of buoyant flows in both phases. The approach we have taken to resolving the importance of buoyancy for these flames is: (1) normal gravity experiments and advanced diagnostics; (2) microgravity experiments; and (3) numerical modelling at arbitrary gravitational level.
Ross, Howard↗
Performance of a Fuel-Injection Spark-Ignition Engine Using a Hydrogenated Safety Fuel
This report presents the performance of a single-cylinder test engine using a hydrogenated safety fuel. The safety fuel has a flash point of 125 degrees f. (Cleveland open-dup method), which is high enough to remove most of the fire hazard, and an octane number of 95, which permits higher compression ratios to be used than are permissible with most undoped gasolines.
Schey, Oscar W↗
Flame Spread Across Liquids
The principal goal of our recent research on flame spread across liquid pools is the detailed identification of the mechanisms that control the rate and nature of flame spread when the liquid pool is initially at an isothermal bulk temperature that is below the fuel's flash point temperature. In our project, we specialize the subject to highlight the roles of buoyancy-related processes regarding the mechanisms of flame spread, an area of research cited recently by Linan and Williams as one that needs further attention and which microgravity (micro-g) experiments could help to resolve. Toward resolving the effects of buoyancy on this flame spread problem, comparisons - between 1-g and micro-g experimental observations, and between model predictions and experimental data at each of these gravitational levels - are extensively utilized. The present experimental and computational foundation is presented to support identification of the mechanisms that control flame spread in the pulsating flame spread regime for which long-duration, micro-g flame spread experiments have been conducted aboard a sounding rocket.
Ross, Howard D.↗
Flame Spread Across Liquids: Experimental Results
The goal of our research on flame spread across a pool of liquid fuel is the quantitative identification of the mechanisms that control the rate and nature of flame spread when the initial temperature of the liquid pool is below the fuel's flash point temperature. Besides numerous experiments in drop towers and 1 g laboratories, we have flown five microgravity (mu-g) experiments on sounding rockets. As described in earlier papers, the first three flights examined the effect of forced opposed airflow over a 2.5 cm deep x 2 cm wide x 30 cm long pool of 1-butanol in mu-g. It was found that the flame spread is much slower and steadier than in 1 g where flame spread has a pulsating character. It was speculated that the flame spread in mu-g resembled the character of pseudo-uniform spread in 1 g; Ito et al later confirmed this conclusively in 1 g experiments. Much of the mu-g flame is also farther from the surface, dimmer, and with less soot, when compared to the 1 g flame. Three-dimensional liquid-phase flow patterns that control the liquid preheating were discovered in both 1 g and mu-g. Our numerical model, restricted to two dimensions, had predicted faster, pulsating flame spread in mu-g for opposed airflow. In examining the differences in the dimensionality of the model and experiment, it was noted that the experiment allowed gas expansion in the lateral direction (across the width of the pool), for which the model could not account. Such lateral expansion could reduce the expansion in the forward and upward directions. Because only these latter directions could be modeled, it was decided to artificially reduce the gas thermal expansion in the predictions. When this was done, satisfactory agreement could be obtained between the predicted and observed spread rates and the steadiness of the spread in microgravity. In 1 g, however, the predicted flame spread character also changed to pseudo-uniform, which disagreed with our 1 g experiments where the spread is pulsating. It was then speculated that gas-phase buoyant flow might oppose the lateral gas expansion, so that the 1 g experiments retained their pulsating flame spread character. If this speculation was valid, a difference in lateral gas expansion should be observable when comparing 1 g and mu-g experiments. Specifically, it was anticipated that greater flow divergence caused by lateral expansion would be measured in mu-g in the absence of a buoyant flow directed towards the flame.
Ross, H. D.↗
Opposed-Flow Flame Spread Across Propanol Pools: Effect of Liquid Fuel Depth
This computational study examines the effect of liquid fuel depth on flame spread across propanol pools with and without forced, opposed air flow. The initial pool temperature is below its closed- cup flash point temperature T(sub cc); so the liquid fuel must be heated sufficiently to create a combustible mixture of fuel vapor before ignition and flame spread can occur. Furthermore, in order for the flame to spread, an approximate rule is that the liquid fuel surface temperature ahead of the flame must be heated above T(sub cc) so that a flammable mixture just above the lean limit exists ahead of the flame. The depth of a liquid fuel pool would affect the heating of the liquid fuel pool and thus the liquid fuel surface temperature ahead of the flame. It has been observed experimentally and numerically that, at normal gravity without forced gas-phase flow and with the initial pool temperature T(sub 0) in a range well below T(sub cc), the flame periodically accelerates and decelerates (pulsates) as it propagates. The depth of a liquid fuel pool would change this range of T(sub 0) since it would affect the heating of the pool.
Kim, Inchul↗
Fluid Management of and Flame Spread Across Liquid Pools
The goal of our research on flame spread across pools of liquid fuel remains the quantitative identification of the mechanisms that control the rate and nature of flame spread when the initial temperature of the liquid pool is below the fuel's flash point temperature. As described in, four microgravity (mu-g) sounding rocket flights examined the effect of forced opposed airflow over a 2.5 cm deep x 2 cm wide x 30 cm long pool of 1-butanol. Among many unexpected findings, it was observed that the flame spread is much slower and steadier than in 1g where flame spread has a pulsating character. Our numerical model, restricted to two dimensions, had predicted faster, pulsating flame spread in mu-g. In a test designed to achieve a more 2-D experiment, our investigation of a shallow, wide pool (2 mm deep x 78 mm wide x 30 cm long) was unsuccessful in mu-g, due to an unexpectedly long time required to fill the tray. As such, the most recent Spread Across Liquids (SAL) sounding rocket experiment had two principal objectives: 1) determine if pulsating flame spread in deep fuel trays would occur under the conditions that a state-of-the-art computational combustion code and short-duration drop tower tests predict; and 2) determine if a long, rectangular, shallow fuel tray could achieve a visibly flat liquid surface across the whole tray without spillage in the mu-g time allotted. If the second objective was met, the shallow tray was to be ignited to determine the nature of flame spread in mu-g for this geometry. For the first time in the experiment series, two fuel trays - one deep (30 cm long x 2 cm wide x 25 mm deep) and one shallow (same length and width, but 2 mm deep)-- were flown. By doing two independent experiments in a single flight, a significant cost savings was realized. In parallel, the computational objective was to modify the code to improve agreement with earlier results. This last objective was achieved by modifying the fuel mass diffusivity and adding a parameter to correct for radiative and lateral heat loss.
Ross, H. D.↗
Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems
Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.
Miller, Fletcher J.↗