Flash Flame Research Articles

Operating Room Fires and Surgical Skin Preparation

Operating room fires are "never events" that remain an under-reported source of devastating complications. One common set-up that promotes fires is the use of surgical skin preparations combined with electrosurgery and oxygen. Limited data exist examining the incidence of fires and surgical skin preparations. A standardized, ex vivo model was created with a 15× 15 cm section of clipped porcine skin. An electrosurgical "Bovie" pencil was activated for 2 seconds on 30 Watts coagulation mode in 21% oxygen (room air), both immediately and 3 minutes after skin preparation application. Skin preparations with and without alcohol were tested, and were applied with and without pooling. Alcohol-based skin preparations included 70% isopropyl alcohol (IPA) with 2% chlorhexidine gluconate, 74% IPA with 0.7% iodine povacrylex, and plain 70% IPA. No fires occurred with nonalcohol-based preparations (p < 0.001 vs alcohol-based preparations). Alcohol-based preparations caused flash flames at 0 minutes in 22% (13 of 60) and at 3 minutes in 10% (6 of 60) of tests. When examining pooling of alcohol-based preparations, fires occurred in 38% (23 of 60) at 0 minutes and 27% (16 of 60) at 3 minutes. Alcohol-based skin preparations fuel operating room fires in common clinical scenarios. Following manufacturer guidelines and allowing 3 minutes for drying, surgical fires were still created in 1 in 10 cases without pooling and more than one-quarter of cases with pooling. Surgeons can decrease the risk of an operating room fire by using nonalcohol-based skin preparations or avoiding pooling of the preparation solution.

Modeling of Low-temperature oxidation and combustion of droplets

Key features of radiation extinguishing of spherical hot flame around a single droplet with its subsequent low-temperature oxidation and combustion under microgravity conditions—a phenomenon discovered in experiments onboard the International Space Station—have been reproduced using the mathematical model of droplet combustion and detailed kinetic mechanism of n-heptane oxidation and combustion. It has been demonstrated that experimentally observed repeated temperature flashes were blue flame flashes, and their duration was determined by the hydrogen peroxide decomposition time. In addition to this phenomenon, calculations predict the existence of new modes of low-temperature oxidation and combustion of droplets without the hot flame stage. In such modes, the basic reaction is concentrated very close to the droplet surface, and fuel vapor reacts in it only partially.

CO2 diluted propane/oxygen combustion in a rapidly mixed tubular flame burner

Propane/oxygen combustion diluted by CO2 was attempted in a rapidly mixed tubular flame burner to eliminate hazards of flame flash back. The flame structure and stability were systematically examined with oxygen mole fraction varying from ultralow to ultrahigh in the oxidizer. To enhance mixing, a tubular flame burner with a thin inlet was utilized, and in addition, CO2 was added also to the fuel slit as well as the oxidizer slit. The results show that a steady and uniform tubular flame can be obtained from lean to rich when the oxygen mole fraction was no more than 0.50, in which the tubular flame was established at ultralow oxygen mole fraction of 0.18, and the steady flame range in equivalence ratio gradually expanded with increasing oxygen mole fraction. By increasing oxygen mole fraction to 0.60, the tubular flame became non-uniform in structure; above 0.70, the tubular flame at the stoichiometry was not obtained. To obtain stoichiometric combustion at a higher oxygen mole fraction, the width of fuel slit was halved while that of the oxidizer slit was doubled to make the width ratio approach the stoichiometry of propane/oxygen (1/5). However, a tubular flame failed to be established above the oxygen mole fraction of 0.70 owing to flame anchoring at the exit of oxidizer slit. To increase both the fuel and oxidizer injection velocities, the width of oxidizer slit was also reduced, and steady tubular combustion at the stoichiometry was achieved up to oxygen mole fraction of 0.80. In the case of stoichiometric propane/oxygen combustion, a flame was anchored at each exit of slit, resulting in turbulent combustion. For combustion under ultrahigh oxygen mole fractions, a tubular flame was established at the very lean condition, and evolved into turbulent combustion through an oscillation region with increasing the equivalence ratio.

Flash flaming effectively removes appendages and improves the seed coating potential of grass florets

Ecological restoration of grasslands using wild‐collected seeds is a major undertaking in many parts of the world. Impediments to effective seed use such as low seed quality, difficult‐to‐handle and bulky collections of seeds, and seed dormancy and germination constraints contribute to restoration failure. Native grass florets are typically irregular in shape, with appendages that impede efficient mechanized sowing and render agricultural technologies, such as the application of polymer seed coatings, impractical. Our goal was to investigate the application of a novel flaming device to remove floret appendages and improve geometry using Triodia wiseana (C.A. Gardner [Poaceae]), a key framework grass of arid ecosystems in north‐western Australia, as a test species. Through the modification of a rotary seed coater with an engineered flaming apparatus, a flash flaming technique was developed. We demonstrate that flash flaming is a highly effective and efficient means of removing floret appendages and subsequently improving geometry. Once flamed, the bulk density of florets was significantly increased, the application of polymer coatings was more effective, and germination was enhanced. The improved floret geometry through flaming therefore shows promise for enhancing the mechanization of direct seeding of grasses.

Experimental study on initial temperature influence on flame spread characteristics of diesel and gasoline–diesel blends

A set of experiments were conducted to investigate the initial temperature effect on the flame spread characteristics of diesel and gasoline–diesel blend (dieseline), including the flame shapes, main flame spread velocity, subsurface flow velocity, surface temperature, flash flame velocity, pulsation frequency and pulsation amplitude. The flame spread process was recorded visually while the fuel temperatures were measured during the experiments. The results showed that the mean spread velocity of main flame of both fuels increased with initial fuel temperature while the dieseline main flame spreads almost twice that of diesel. During flame spread, the front temperature and velocity of subsurface flow increased with initial fuel temperature and the velocity of dieseline increased faster due to longer subsurface flow. Furthermore, it was found that the pulsation amplitude of diesel flash flame increased with initial fuel temperature while the one of dieseline decreased initially and then increased with increasing initial fuel temperature. The pulsation frequency and velocity of flash flame were found to be independent to the initial fuel temperature.

Experimental study on the interaction between fire and water mist in long and narrow spaces

A series of water mist fire suppression tests were conducted with the rubber ignition as the sign of flashover. An open type nozzle was mounted 1100 mm from the ethanol pan center and activated 8 minutes after the ethanol being ignited. The water mist average velocity and drop size, the fire temperature profiles, the radiant heat flux and the hydrogen, oxygen concentrations were measured. Much hydrogen was detected and its concentration increased with the increase of water mist pressure and flow rate. The 20 bar and 30 bar water mist intensified the flashover and the fire, hydrogen and the sharp increase of the radiant heat flux are the key factors to the intensification. With the 40 bar, K = 1 and 50 bar, K = 0.5 water mist, the rubber still ignited with only a flash flame. The flashover and fire restraining effects are improved with the increase of water mist pressure and flow rate. The 60 bar water mist effectively suppressed the flashover and restrained the fire some extent, and the 70 bar and K = 1 water mist successfully suppressed the fire in 110 s. The radiant heat flux attenuation and the fuel surface cooling effect are the key fire and flashover suppression mechanisms.

돌발화염으로 인한 화상예측에 관한 수치해석적 연구

매년 많은 소방공무원들이 화재나 고온 조건 등에 노출되어 화상으로 고통 받고 있어, 화상 예측에 대한 연구를 통해 화상을 방지할 수 있는 방법의 개발이 매우 중요하다. 그러나 피부조직의 비선형성, 혈류에 의한 열전달 분석의 불확실성 등 인체 내부의 복잡한 물리현상으로 인해 화상에 대한 연구는 매우 부족한 것이 실정이며, 특히 국내의 경우는 이에 대한 연구가 전무한 실정이다. 본 연구에서는 특히 심각한 화상을 유발할 수 있는 돌발화염(80 kW/<TEX>$m^2$</TEX> 이상의 고열 유속 조건)하에서의 2도 화상 발생에 대한 예측을 수행하였다. 생체 열전달 방정식(Bio-heat transfer)을 이용하여 지배방정식을 유도하였으며, 유한차분법(Finite Difference Method)을 활용하여 화상에 대한 예측을 수행하는 수치해석 접근법을 사용하였다. 기존의 여러 연구결과로부터 인체 피부의 열물성치를 정리하였고, 그것을 바탕으로 계산을 수행하였다. 기존의 낮은 열유속에 대한 화상 실험 결과와 예측 결과를 비교하여 가장 오차가 적은 열물성치 모델을 파악하였고, 그 결과를 바탕으로 고열유속의 돌발화염에서의 2도 화상발생 노출시간을 예측하여 제시하였다. Many fire-fighters suffer from the burn injuries, and the severe burns are the most catastrophic injury a person can survive, resulting in pain, emotional stress, and tremendous economic costs. It is important to understand the physiology of burns for prevention from skin burns and a successful treatment of a burn patient. But a few researches have been presented because the complex physical phenomena of our inside body like non-linearity characteristics of human skin make them difficult. Thus in this study, thermal analyses of biological tissues exposed to a flash fire causing severe tissue damage were studied by using a finite difference method based on the Pennes bio-heat equation. The several previous models for skin thermo-physical properties were summarized, and the calculated values with those models of tissue injury were compared with the results obtained by the previous experiment for low heat flux conditions. The skin models with good agreement could be found. Also, the skin burn injury prediction results with the best model for high heat flux conditions by flash flame were suggested.

A novel structure design towards extremely low thermal conductivity for thermal barrier coatings – Experimental and mathematical study

In this paper, a novel structure design towards extremely low thermal conductivity for thermal barrier coatings (TBCs) has been proposed. The structure design includes layer structure design and the defects configuration design. Firstly, an experimental investigation has been performed. The La2Zr2O7 (LZ) which is one of the zirconate-based TBCs materials was chosen as the investigated material in the layer structure design. Nanostructured ZrO2–8wt%Y2O3 (8YSZ), conventional 8YSZ TBCs and double-ceramic-layer (DCL) La2Zr2O7/nanostructured 8YSZ (LZ/n-8YSZ) were prepared by atmospheric plasma spraying (APS) on 45#steel substrates with the NiCrAlY as the bond-coat, respectively. The insulation temperatures of the three coatings were measured by oxyacetylene flame flash method and the effective thermal conductivities of the as-sprayed coatings have been obtained. Secondly, the effect of defects configuration on the effective thermal conductivity has been discussed systematically based on the strict mathematical calculation combined with finite element simulation. Based on the experimental and mathematical studies, an ideal coating structure was proposed for further decreasing the effective thermal conductivity of the TBCs. The effective thermal conductivity of the DCL LZ/n-8YSZ TBCs based on the actual morphology was calculated using computational micro-mechanics (CMM) method.

Flexible CO2Laser Fiber in the Pediatric Airway

Objective. Our institution has been using a novel flexible laser fiber in pediatric surgical airway procedures, which has been quite successful. The purpose of this paper is to present our preliminary experience in the treatment of pediatric airway lesions using this laser technique.Methods.A case series reviewing 40 patients undergoing 95 laser procedures is reported. Indications included removal of suprastomal granulation tissue, removal of granulation after laryngotracheal reconstruction, subglottic and supraglottic stenoses, recurrent respiratory papillomas, subglottic hemangioma, laryngeal cleft, and left main stem bronchus stenosis. Procedures were performed via microdirect laryngoscopy and bronchoscopy.Results. No complications including postoperative glottic webs, concentric scar formation, or airway fires occurred in any of the patients (after the series was completed, we did experience an airway fire. It was a flash flame that was self-limited and caused no long-term tissue injury).Conclusions. The endoscopic application of a new flexible carbon dioxide laser fiber for management of pediatric airways lesions provides good outcomes in selected patients. Distal respiratory papillomas, subglottic stenosis, and granulation tissue are, in our experience, appropriate indications.

Lean-limit combustion instabilities of a lean premixed prevaporized gas turbine combustor

One type of low-frequency combustion instability was studied in a lean premixed prevaporized (LPP) gas turbine combustor experiment that was operated at elevated pressures using liquid Jet-A fuel. This intense low-frequency (15 Hz) instability is called a “lean-limit” instability, while in other papers it has been called a “cold tone”, an “incipient blowout” instability or an “entropy wave”. High-speed movies identified the physical mechanism. At first the flame enters the shear layer, is locally extinguished and lifts off. The extinguished region fills with unburned reactants. Finally the premixed flame flashes back into the region of unburned reactants, leading to a large pressure rise which triggers the next cycle. The observations are in general agreement with LES computations published by Huang and Yang. Measurements quantify the time lag between the flame luminosity buildup and subsequent pressure rise as well as the correlation between these two quantities and their spectra. The frequency of this “lean-limit” instability is found to be related to the flow velocity, flame velocity, and the combustor length, as is predicted for an entropy wave. A discussion is presented to qualitatively explain the measured frequencies, which increase as the fuel equivalence ratio is raised. The experiment includes the following realistic conditions: Jet-A liquid fuel, preheated air, elevated pressure and realistic sources of instabilities, including a commercial fuel injector/mixer that creates flame–flame interactions between a non-premixed Pilot and premixed Main flame that are necessary for aircraft applications.

In vitro testing of current spread during ventricular catheter coagulation using diathermy

The authors report on the development of an anterior cerebral artery pseudoaneurysm that hemorrhaged after monopolar coagulation for a ventricular catheter lodged in the interhemispheric fissure. After observing this complication, the authors developed a simple bench test that can be performed by any neurosurgeon to determine the safest coagulation parameters for any given diathermy unit. A modified grounding pad was placed in a beaker of a protein solution consisting of egg whites. Ventricular catheters were then placed in the solution, and a monopolar diathermy current was applied to a metal stylet at various wattages and for different durations of time. Inducing coagulation at 40 W with a diathermy unit produced flames emanating from around the pores of the catheter tip. Flash flames were also observed at 35 W, forming a coagulum of egg white for a distance of up to 1 cm from the catheter tip. All heat was dissipated through the holes of the first 16 mm of the catheter. At 20 W the flame was minimal and coagulation appeared adequate, whereas at 15 W only bubbles were seen around the tip together with suboptimal coagulum formation. This technique is a simple and effective means of determining the optimal setting for monopolar diathermy and can be used to figure the optimal catheter coagulation wattage for a given diathermy unit. Considering the results of this study, the authors have lowered the current for coagulation in ventricular catheters to 20 W.

REDUCTION OF NICKEL-COPPER MATTE/OXYSULFIDE/SLAG

To improve the value of recovered metals, a new operating concept for the Inco flash furnace was investigated in which the flash furnace coke addition practice aimed to establish a reducing barrier on the surface of the molten bath. The descending partially oxidized sulfide mineral particles would reach the supernatant coke layer prior to the formation of slag. The key for success depends on the effectiveness of the coke layer to produce a sulfur deficient matte while maintaining the furnace production capacity.The mechanism and rate of carbon reduction of the phases formed in the flash flame (i.e., sulfide (matte) and oxysulfide) were investigated by means of crucible graphite reduction tests. The objective of these tests was to measure the rate of solid graphite reduction of matte, oxysulfide, slag and matte+slag mixture at different temperatures. These tests were expected to permit understanding and explain the reduction mechanism of each material by comparing the respective reaction rates, product reaction gas compositions, reduced material assays and other relevant parameters. Direct visual inspection of the test crucibles would provide additional information.Afin d’améliorer la valeur des métaux récupérés, on a étudié un nouveau concept d’opération du four éclair d’Inco, dans lequel la pratique d’addition de coke du four éclair visait à établir une barrière de réduction à la surface du bain fondu. Les particules minérales descendantes de sulfure, partiellement oxydées, attendraient la couche de coke surnageante avant la formation de scorie. La clé du succès dépend de l’efficacité de la couche de coke à produire une matte déficiente en souffre tout en maintenant la capacité de production du four.On a étudié le mécanisme et le taux de réduction du carbone des phases formées dans la flamme éclair (i.e. sulfure (matte) et oxysulfure) au moyen d’essais de réduction de creuset en graphite. L’objectif de ces essais était de mesurer le taux de réduction du graphite solide de la matte, de l’oxysulfure, de la scorie et du mélange matte+scorie, à différentes températures. On s’attendait à ce que ces essais permettent de comprendre et d’expliquer le mécanisme de réduction de chaque matériau en comparant les taux respectifs de réaction, la composition des gaz de réaction produits, les balances du matériau réduit et autres paramètres pertinents. L’inspection visuelle directe des creusets d’essai fournirait de l’information additionnelle.

Heat Transfer Mechanism of a Flash Flame Spread Along a Vertical or Inclined Napped Fabric

A napped fabric is known to catch fire easily, and the flame spreads along the napped surface very fast; i.e., a flash flame spread occurs. It may cause a person wearing the napped fabric to be burned alive. To avoid such a fire accident, flame spread phenomena along a napped fabric must be clarified for suppressing the flash flame spread along its surface. For this purpose, the flash flame spread along a napped fabric has been investigated experimentally. The absorbent cotton sheet napped mechanically was used as a sample of a napped fabric. Dependence of the flash flame spread rate on depth or density of a napped layer was studied experimentally. It was ascertained that the flame spread rate depended on both the depth and the density of the napped layer. Considering the experimentally obtained dependency, a heat transfer model of the flame spread along a napped layer was developed. From the model that considered the experimental results, it was revealed that a convective heat transfer governed the flame spread rate strongly in the case of upward flame spread along a napped fabric. Language: en

Flame flashes when bubbles explode during the combustion of gaseous mixtures in a bubbling fluidized bed

The combustion of fuel-lean mixtures of methane + air in a strongly bubbling fluidized bed of quartz sand has been studied in the laboratory. Video color images of the burning bed, at 25 frames/s, were examined and used to obtain images in three color bands, red, green, and blue. A mathematical procedure was then employed to analyze the color images further, to discriminate between continuous radiation from the hot sand and discrete emission, mostly in the blue wavelength region, from bubbles exploding inside the bubbling bed or at its surface. The results obtained show that transient flames occur in the bubbles, confirming that the combustion process in fluidized bed is basically similar to that in flames, with the involvement of free radical species.

Behavior of flames spreading downward over napped fabrics

The behavior of flames spreading downward over napped cotton/polyester (75/25) fabrics has been experimentally investigated. The degree of napping, represented by nap thickness, was determined using an image processing technique. The dependence of the behavior of flame spread on nap thickness was examined. Flame spread over fabrics without surface flash, with intermittent surface flash, and with surface flash was observed, recorded and analyzed. The critical nap thickness (2 mm) for surface flash occurrence was found. The rate of surface flash flame spreads is more than 100 times faster than that of flame spread without surface flash. A part of nap remains unburned after surface flash. It was found that the thickness of the remaining nap region (unburned nap thickness) is almost constant around 1.3 mm. The difference between this unburned nap thickness (1.3 mm) and the critical nap thickness (2.0 mm) might correspond to the minimum burned nap thickness, which is needed to sustain surface flash.

Management of partial thickness facial burns (comparison of topical antibiotics and bio-engineered skin substitutes)

This study compared the effect of standard topical antibiotic management versus a biological skin substitute wound closure for mid-partial thickness burns of the face. Adult patients with mid-dermal facial burns produced by flash flames or flame exposure were studied using a randomized prospective study design. Total daily burn care time, pain (0–10 scale) and healing time were monitored. Immediately after partial thickness debridement, the entire face burn, including ears, was closed with a bioengineered skin substitute coated with fibronectin (TransCyte) or treated by the open technique using bacitracin ointment applied 2–3 times daily. 21 patients were studied, with 10 patients in the skin substitute group. We found a significant decrease in wound care time 0.35±0.1 versus 1.9±0.5 h, decrease in pain of 2±1 versus 4±2 and re-epithelialization time 7±2 versus 13±4 days in the skin substitute group compared to topical antibiotics. We can conclude that a bioengineered skin substitute significantly improves the management and healing rate of partial thickness facial burns, compared to the standard open topical ointment technique.

External Cluster Combustion of Binary-Fuel Drops

A model describing external sheet combustion of a cluster of drops has been developed for clusters of binary-fuel drops. The binary-fuel is assumed to be a solvent-solute combination in which the solute is much more volatile than the solvent whose initial mass fraction within the mixture is larger than that of the solute. Both the ignition timing and location are calculated using criteria previously derived; for the range of air/fuel mass ratios considered, ignition always occurs around the cluster. Following ignition, an internal flash flame burns all the oxygen within the cluster. An external sheet flame ensues fueled by vapor released from the cluster. Results show that drop interactions are important in modifying the amount of fuel burnt. It is only for small initial cluster velocities and for large air/fuel mass ratios that the external flame behaves approximately like a classical diffusion flame in that it almost burns all the fuel released from the cluster. For all other conditions, the amount of fuel burnt is smaller than that released from the cluster. These conclusions are independent of the initial solute mass fraction and of the Arrhenius ignition parameters having assumed them identical for solvent and solute.

Effect of rotation on Bunsen flame

The influence of centrifugal acceleration on the form and stability of the Bunsen burner stabilized flame is studied. It is shown that as the angular velocity of rotation increases, the classical Bunsen cone first slightly buckles at the tip. Buckling then becomes more prominent, and eventually the flame enters the burner. At sufficiently rapid rotation, flame stabilization by the burner rim becomes impossible and the flame flashes back. The theoretical findings are in favorable agreement with the experimental observations made on a rotating Bunsen burner.

CARE OF THE CRITICALLY ILL CHILD: MAJOR BURNS

Burns are the third most important cause of accidental death in childhood, outranked only by automobile casualties and drownings1. In the United States 12,000 deaths occur annually, but over the same period 2,000,000 patients are hospitalized for burns2. Among these, a very large numher of children must undergo prolonged, painful, and restrictive hospitalization from which they emerge with scars to both body and personality profoundly affecting their social and emotional development. The tragedy is that the great majority of burn injuries are preventable. In the toddler stage the most common accident occurs when the youngster reaches up and pulls on a pot handle at the front of the stove, resulting in a scald of the extended arm, shoulder, and chest. With the advent of summer, burns from the outdoor barbecue become epidemic. These are flash flame burns of face, hands, arms, and chest, usually in boys, that follow explosive ignition of the outdoor fire on which the victim has poured gasoline, kerosene, or other highly flammable starter fluid. The pant-leg burn is prevalent during the autumn when the burning of leaves is common. At all seasons one encounters burns, principally of the chest when the loose, frilly nightdresses of young girls ignite from too close proximity with the open fire, gas range, or candelabrum. Mandatory treatment of cloth with fire retardants could greatly reduce the incidence of these injuries at a negligible cost. As early as possible children should be taught never to run should their clothing ignite but rather to fall to the ground and smother the fire by rolling.

Semitheoretical consideration on scaling laws in flame stabilization

With good approximation to reality the stability of flames on flameholders may be described with simple equations for heat and mass transfer. As a result of considerations with regard to a simple model a dimensionless number Nx is obtained, which is constant in the limiting case of large Reynolds numbers and small blockage ratios for all flameholders and gaseous fuels with a sufficiently high laminar flame speed. It combines the two stabilization laws found by Zukoski and Marble and by Putnam and Jensen, which were discussed further by Spalding. Regarding several deviations from the limit case we succeeded in finding adaptation functions from theoretical considerations or on an empirical basis. These were introduced into the stability equation, and permit comparison of seemingly very dissimilar systems. A relationship between flame stability and flame flash back is pointed out as affected by transport mechanism and flame speed. In addition the combustion of heterogenous mixtures is treated.