OXIDIZER AND GAS-ENVIRONMENT EFFECTS ON AFTERBURNING REACTIONS AND EXPLOSION PERFORMANCES OF HMX-BASED THERMOBARIC EXPLOSIVES

In this paper, confined explosions of HMX-based thermobaric explosives containing oxidizers in a spherical chamber were studied by changing the type of the oxidizer and the oxygen concentration in the environment. Based on an in-house developed optical-electrical system, the optical radiation signals of Al2O3 during the afterburning reaction were recorded. The results show that aluminum particles (5.4 µm) were strongly dependent on the oxygen concentration in the environment. Increasing the oxygen concentration can prolong the oxidation duration of Al and enhance the optical radiation intensity of Al2O3. The optical radiation result for Al2O3 in O2 and air showed that aluminum particles (the mass fraction was 33 %) were not completely oxidized in the air, and the oxidation duration was 500–700 µs. Moreover, the pressure data of the blast waves was obtained using a pressure-measurement system. The results showed that an increase in the oxygen concentration of the explosive could further enhance the total impulse, especially an addition of KP (its mass fraction was 10 %) could increase the total impulse by about 9 %.

Download Full-text

Clearing of Blast Waves on Finite-Sized Targets – an Overlooked Approach

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.82.669 ◽

2011 ◽

Vol 82 ◽

pp. 669-674 ◽

Cited By ~ 5

Author(s):

Andrew Tyas ◽

Terry Bennett ◽

James A. Warren ◽

Stephen D. Fay ◽

Sam E. Rigby

Keyword(s):

Blast Wave ◽

Experimental Testing ◽

Experimental Studies ◽

Blast Loading ◽

Blast Waves ◽

Total Impulse ◽

Cast Doubt ◽

The Face ◽

Loading Parameter ◽

Semi Empirical

The total impulse imparted to a target by an impinging blast wave is a key loading parameter for the design of blast-resistant structures and façades. Simple, semi-empirical approaches for the prediction of blast impulse on a structure are well established and are accurate in cases where the lateral dimensions of the structure are sufficiently large. However, if the lateral dimensions of the target are relatively small in comparison to the length of the incoming blast wave, air flow around the edges of the structure will lead to the propagation of rarefaction or clearing waves across the face of the target, resulting in a premature reduction of load and hence, a reduction in the total impulse imparted to the structure. This effect is well-known; semi-empirical models for the prediction of clearing exist, but several recent numerical and experimental studies have cast doubt on their accuracy and physical basis. In fact, this issue was addressed over half a century ago in a little known technical report at the Sandia Laboratory, USA. This paper presents the basis of this overlooked method along with predictions of the clearing effect. These predictions, which are very simple to incorporate in predictions of blast loading, have been carefully validated by the current authors, by experimental testing and numerical modelling. The paper presents a discussion of the limits of the method, concluding that it is accurate for relatively long stand-off blast loading events, and giving some indication of improvements that are necessary if the method is to be applicable to shorter stand-off cases.

Download Full-text

Numerical Investigation of the Required Quantity of Inert Gas Agents in Fire Suppression Systems

Energies ◽

10.3390/en13102536 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2536 ◽

Cited By ~ 1

Author(s):

Xiaoqin Hu ◽

Arjen Kraaijeveld ◽

Torgrim Log

Keyword(s):

Oxygen Concentration ◽

Mass Fraction ◽

Fire Suppression ◽

Discharge Rate ◽

Combustion Process ◽

Threshold Level ◽

Ventilation Rate ◽

Inert Gas ◽

In Fire ◽

Suppression Systems

Inert gas agents have the potential to be widely used in fire suppression systems due to health and safety concerns associated with active chemicals. To suppress fire while minimizing hypoxic effects in an occupied area, the discharge quantity of inert gas agents should be carefully designed to dilute the oxygen concentration to a specific threshold level. In this study, the general expressions between oxygen concentration, the discharge rate of inert gas agents, and the ventilation rate of the air-agent mixture are derived first. Then, explicit formulas to calculate the discharge/ventilation rate and the required quantity of inert gas agents are given if the discharge rate and ventilation rate both are constants. To investigate the dilution and fire extinguishing efficiencies of inert gas agents, two scenarios with a discharge of inert gas agents into an enclosure are modeled using the Fire Dynamic Simulator (FDS). The simulation results show that the average oxygen mass fraction approximately reaches the design level at the end of the discharge period. Variation in oxygen concentration along the enclosure height is analyzed. For the scenario with a fire source, oxygen mass fraction decreases fast as oxygen is consumed by the combustion process. Thus, the fire is extinguished a little earlier than the end of the discharge period.

Download Full-text

Effect of Nitrogen and Oxygen Concentration on NOx Emissions in an Aluminum Furnace

Energy Conversion and Resources ◽

10.1115/imece2006-15693 ◽

2006 ◽

Cited By ~ 2

Author(s):

Brian Golchert ◽

Paul Ridenour ◽

William Walker ◽

Naresh K. Selvarasu ◽

Mingyan Gu ◽

...

Keyword(s):

Natural Gas ◽

Oxygen Concentration ◽

Mass Fraction ◽

Molecular Nitrogen ◽

Nitrogen Concentration ◽

Pure Oxygen ◽

Partial Replacement ◽

Nox Emissions ◽

Pollutant Formation ◽

The Aluminum Industry

For many aluminum melting furnaces, natural gas is mixed with air. The ensuing heat from combustion is then used to melt the solid aluminum and heat the liquid metal. Of increasing concern to the industry are the more stringent regulations in regard to NOx emissions from these plants. The formation of NOx mainly depends on the concentration of nitrogen and the temperature of the gas. One problem that affects this formation that has not been adequately addressed is the variability of the local natural gas supply. Natural gas has molecular nitrogen as a portion of its composition. This percentage ranges from approximately one to seven percent of the total mass fraction. In addition, the aluminum industry is investigating methods to reduce NOx emissions. One method is to replace some of the combustion air with pure oxygen. This reduces the amount of nitrogen coming into the furnace, but also raises the combustion temperature which could promote NOx production. This paper details a systematic computational fluid dynamics study on how the variability of the nitrogen concentration coupled with the partial replacement of air with pure oxygen affects heat transfer and pollutant formation in an aluminum furnace. Trends will be discussed as will the ideal oxygen concentration for a given nitrogen mass fraction.

Download Full-text

An Insole Pressure Measurement System: Repeatability of Postural Data

Foot & Ankle International ◽

10.1177/107110070002100307 ◽

2000 ◽

Vol 21 (3) ◽

pp. 221-226 ◽

Cited By ~ 9

Author(s):

Jeffrey A. Bauer ◽

James H. Cauraugh ◽

Mark D. Tillman

Keyword(s):

Measurement System ◽

Pressure Measurement ◽

Postural Stability ◽

Postural Sway ◽

Test Session ◽

Quiet Stance ◽

Healthy Individuals ◽

Pressure Data ◽

Plantar Pressure Measurement ◽

Pressure Measurement System

This study analyzed the ability of an in-shoe plantar pressure measurement system to provide repeatable measurements of postural sway data for both healthy and clinical patients. Each participant's in-shoe pressure data were recorded for three trials during each test session during quiet stance. Healthy individuals (n=9) participated on three consecutive days while clinical participants (n=5) were tested on one day. Nine response variables were measured to assess their postural stability. Intra-subject measures were evaluated using the Kerlinger reliability procedure. Values provided directly by the Parotec System® for a single day of testing yielded the following average coefficients: r = 0.95 (left), r = 0.97 (right) with mean coefficient values from the three day tests of: r = 0.98 (left), r = 0.98 (right). Variables calculated from raw data on a single day produced mean coefficients of: r = 0.77 (left), r = 0.76 (right) and over three days of: r = 0.65 (left), r =0.66 (right). The ability to record highly reproducible data of postural sway parameters should assist clinicians to treat patients more confidently for balance deficiencies.

Download Full-text

Rendez vous with Saturn's rings

International Astronomical Union Colloquium ◽

10.1017/s0252921100101885 ◽

1984 ◽

Vol 75 ◽

pp. 743-759 ◽

Cited By ~ 2

Author(s):

Kerry T. Nock

Keyword(s):

Solar Energy ◽

Electric Propulsion ◽

Power Source ◽

Propulsion System ◽

Low Thrust ◽

Ring Plane ◽

The Earth ◽

Total Impulse ◽

Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

Download Full-text

High-resolution transmission electron microscopic study of highly oxygen doped silicon layer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155438 ◽

1989 ◽

Vol 47 ◽

pp. 692-693

Author(s):

H. Takaoka ◽

M. Tomita ◽

T. Hayashi

Keyword(s):

High Resolution ◽

Oxygen Concentration ◽

Silicon Layer ◽

Detailed Structure ◽

Electron Microscopic ◽

Cross Sectional ◽

Transmission Electron ◽

Doped Silicon ◽

Argon Ion

High resolution transmission electron microscopy (HRTEM) is the effective technique for characterization of detailed structure of semiconductor materials. Oxygen is one of the important impurities in semiconductors. Detailed structure of highly oxygen doped silicon has not clearly investigated yet. This report describes detailed structure of highly oxygen doped silicon observed by HRTEM. Both samples prepared by Molecular beam epitaxy (MBE) and ion implantation were observed to investigate effects of oxygen concentration and doping methods to the crystal structure.The observed oxygen doped samples were prepared by MBE method in oxygen environment on (111) substrates. Oxygen concentration was about 1021 atoms/cm3. Another sample was silicon of (100) orientation implanted with oxygen ions at an energy of 180 keV. Oxygen concentration of this sample was about 1020 atoms/cm3 Cross-sectional specimens of (011) orientation were prepared by argon ion thinning and were observed by TEM at an accelerating voltage of 400 kV.

Download Full-text