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Abstract Burning characteristics (mass burning rate, natural convection boundary layer thickness, flame height and dark zone height) of laminar diffusion flames produced by a candle at sub-atmospheric pressures in the range of P ∞ = 50–100 kPa were experimentally studied in a reduced-pressure chamber; such data are not reported to date. Scaling analysis was performed to interpret the pressure dependence. The new experimental findings for candle flames in the sub-atmospheric pressures were well interpreted by the proposed scaling laws: (1) the mass burning rate was higher for a candle with larger wick length, and it increased with increasing ambient pressure, a stagnant layer B -number model based on natural convection boundary (flame boundary layer thickness) was developed to scale the mass burning rate of candle flames at various pressures; (2) the flame boundary layer thickness was wider in lower pressure and can be well represented by a natural convection boundary layer solution; (3) flame height was higher for a candle with larger wick length, meanwhile the ratio of flame height to burning rate was independent of pressure; (4) the flame dark zone height representing a soot formation length scale changes little with pressure, meanwhile its ratio to the total flame height is scaled with pressure by P ∞ − 1 / 2 / L w , e 3 / 4 (L w,e is effective wick length inside flame). This work provided new experimental data and scaling laws of candle flame behaviors in sub-atmospheric pressures, which provided information for future characterization and soot modeling for diffusion flames associated with melting and evaporation processes of solid fuels. [ABSTRACT FROM AUTHOR]

This paper investigates the flame height and the fraction of stoichiometric air entrained ( n, the basic parameter in flame heights correlation) for rectangular turbulent jet fires at sub-atmospheric pressure, for which no data are available in the literature. Comprehensive experiments are carried out in a naturally sub-atmospheric pressure (Lhasa city, 64 kPa) by rectangular nozzles whose aspect ratio varied from 1:1 to 1:71. The flame heights are measured and correlated by the unified formula suggested by Quintiere and Grove which was obtained at standard atmospheric pressure, meanwhile the change of the important parameter, n or C f (reflecting air entrainment into flame and thus being basic in flame height correlation) in the sub-atmospheric pressure is addressed. It is found that: (a) the flame height in the sub-atmospheric pressure can be well approached by the unified formula suggested by Quintiere and Grove; however (b) the correlation parameter C f is larger (1.6 times that in standard pressure) or the value of n is smaller (73% of that in standard pressure) in the sub-atmospheric pressure than that in the standard pressure. The relative change of n at the sub-atmospheric pressure is then theoretically deduced from the change of entrainment strength ( C 1 ) and flame envelope along with pressure drop. The theoretically deduced ratio of n (or C f ) between these two pressures agrees with the experimentally correlated results. Then, by accounting for the changes of the correlation parameters, a proposed explicit model can generally predict the flame heights in both pressures. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of cross flow of air on flame base drag in pool fires in sub-atmospheric pressure, where no data is available, by combining the effects of these two factors: sub-atmospheric pressure and cross flow. Experiments were carried out using heptane and acetone as fuels for 10–25 cm square pool fires where the cross flow was provided by a wind tunnel built in Lhasa city-Tibet (64 kPa) as well as correspondingly by a wind tunnel in Hefei city (100 kPa). Additional larger scale experiments were also conducted with 45 cm, 60 cm and 70 cm square pool fires in Hefei city. The evolution of flame base drag length as a function of cross flow air speed was quantified. The flame base drag length was found to be larger in the sub-atmospheric pressure than that in normal pressure, indicating higher risk of causing fire spread to nearby fuel at the ground level. Previous correlations based on a wind Froude number are not in agreement with each other. In addition, they do not include all the physics and they do not account for the effect of the pressure change on flame base drag length. A new theoretical approach is proposed accounting for the relation of wind force with the buoyancy of the flame and the interaction of wind with the total heat release rate from the fire. It follows that three independent dimensionless quantities are introduced: the (inverse) fire source Froude number owing to flame buoyancy, the total buoyancy–wind interaction number and the ratio of fuel vapor density near the fuel surface to the air density. This theory allows us to develop and validate a correlation for flame base drag length to account for pressure effect and for generalizing the existing relations for flame base drag. [ABSTRACT FROM AUTHOR]

Abstract: The influence of pressure and flow rate on momentum-dominated methane laminar flames’ flickering and radiation characteristics were experimental studied to provide a focused description of diffusion flame behavior at sub-atmospheric pressure of 50-100kPa. Measurement system consisted of CCD camera, high speed camera and schlieren system, radiation flux meter. Parameters including flame length, liftoff height, flickering frequency, and radiation intensity were compared and analyzed over the pressure range of 50-100kPa in a low pressure combustion cabin. The controlled fuel mass flow rates provided diffusion flames of 5.95-23.81mg/s stable at all ambient pressures considered. Experiment results indicated that for momentum-dominated jet flame, flame lengths were not dependent on pressure but linearly dependent on mass flow rate. As soot volume fraction was strongly influenced by pressure, when pressure descended, the radiation intensity declined resulted from reduction of soot formation. Lift off phenomenon of diffusion flames was not significant, however, liftoff heights also increased with increasing pressure and mass flow rate gradually. A semi-quantitative explanation on combined effect of pressure and velocity on flickering frequency was given as f = 0.227u0.18P∞1/3. All experiment data was in good agreement with theoretical analysis. [Copyright &y& Elsevier]

Abstract: Background: External small bowel fistulae (ESBF) are serious complications that represent a major challenge for general surgeons. They are still associated with significant morbidity and mortality. This article reviews the management of ESBF with emphasis on the treatment using sub-atmospheric pressure as well a timing, strategies and techniques of reconstructive surgery. Methods: Relevant articles from 1960 to 2010 were identified using various electronic databases to review randomized controlled trials, prospective observational studies, retrospective studies and case reports and highlight key references. Conclusions: External small bowel fistulae require multidisciplinary management and multimodal approaches with a primary essential focus on early recognition and diminishment of mortality factors such as sepsis and malnutrition. In most cases, the initial treatment is conservative, including clinical and nutritional recovery, output control and extensive local wound care. At this stage, the application of local negative pressure is highly effective. This procedure also allows for a spontaneous closure in many patients. Other cases require careful consideration of surgical reconstruction, knowing that success rates are variable and largely dependent on the patient’s condition as well as on local aspects of the lesion. Best surgical results are obtained via intra-peritoneal access with extensive enterolysis, resection of the bowel segment from which the fistulae originate and direct abdominal wall closure. [Copyright &y& Elsevier]

Abstract: Flame spread along the single wire harness (thin-metal wire with coating of polyethylene film) in sub-atmospheric pressure has been examined experimentally to gain better understandings of the electric fire in the aircraft and space habitats. Two kinds of sample wires, made by nickel-chrome (NiCr) and iron (Fe) as core metal, are used in this study. Ambient gas is fixed as air and total pressure is varied from atmospheric to sub-atmospheric (100–20kPa). As the pressure decreases, flame shape changes from typical “teardrop” to “oval” and flame becomes less-luminous irrespective of the materials of the wire. It turns out that the dependence of the spread rate on pressure varies with the materials of the wire; when the pressure decreases, the spread rate of NiCr-harness monotonically increases, whereas that of Fe-harness mostly remains as constant. From the simple thermal-length analysis, it is proposed that there are two modes in the spread depending on the controlling factor; one is “wire-driven mode” (the spread is mainly governed by the thermal input through the wire) and the other is “flame-driven mode” (the spread is mainly governed by the thermal input from the flame). Observed two cases (NiCr- and Fe-harness) would be categorized to the latter and former modes, respectively. [Copyright &y& Elsevier]

Abstract: Vacuum assisted closure is being increasingly used for wound management. This review examines the history of its development and appraises the current evidence on its use so far. [Copyright &y& Elsevier]