Effect Of Oxygen Fraction Research Articles

On the effects of oxygen fraction on stability and combustion characteristics of dual-swirl oxy-methane flames: An experimental and numerical study

On the effects of oxygen fraction on stability and combustion characteristics of dual-swirl oxy-methane flames: An experimental and numerical study

Effect of oxygen fraction in nitrogen/oxygen mixtures on primary and secondary streamers in atmospheric-pressure barrier discharge

Two-dimensional simulation of an atmospheric-pressure dielectric barrier discharge (DBD) was performed with different oxygen fractions, [O2]f, of 20%, 40%, 60%, 80%, and 99% in N2/O2 gas to investigate their effects on the primary and secondary streamers. We simulated the optical emission intensity at different [O2]f and compared them with the experimental values. The simulation results indicate that [O2]f affects the ratio of the amount of the electron production from electron impact ionizations and a photoionization, resulting in the changes in the electric field at the tip of the streamer and that in the streamer channel.

Effect of oxygen fraction on airway rescue: a computational modelling study

BackgroundDuring induction of general anaesthesia, patients frequently experience apnoea, which can lead to dangerous hypoxaemia. An obstructed upper airway can impede attempts to provide ventilation. Although unrelieved apnoea is rare, it continues to cause deaths. Clinical investigation of management strategies for such scenarios is effectively impossible because of ethical and practical considerations. MethodsA population-representative cohort of 100 virtual (in silico) subjects was configured using a high-fidelity computational model of the pulmonary and cardiovascular systems. Each subject breathed 100% oxygen for 3 min and then became apnoeic, with an obstructed upper airway, during induction of general anaesthesia. Apnoea continued throughout the protocol. When arterial oxygen saturation (Sao2) reached 20%, 40%, or 60%, airway obstruction was relieved. We examined the effect of varying supraglottic oxygen fraction (Fo2) on the degree of passive re-oxygenation occurring without tidal ventilation. ResultsRelief of airway obstruction during apnoea produced a single, passive inhalation (caused by intrathoracic hypobaric pressure) in all cases. The degree of re-oxygenation after airway opening was markedly influenced by the supraglottic Fo2, with a supraglottic Fo2 of 100% providing significant and sustained re-oxygenation (post-rescue Pao2 42.3 [4.4] kPa, when the airway rescue occurred after desaturation to Sao2 60%). ConclusionsSupraglottic oxygen supplementation before relieving upper airway obstruction improves the effectiveness of simulated airway rescue. Management strategies should be implemented to assure a substantially increased pharyngeal Fo2 during difficult airway management.

Visible photoluminescence from plasma-polymerized-organosilicone thin films deposited from HMDSO/O2 induced remote plasma: effect of oxygen fraction

Visible photoluminescence (PL) from thin films deposited on silicon wafers by remote plasma polymerization of the hexamethyledisiloxane (HMDSO)/O2 mixture in a radio-frequency hollow cathode discharge reactor has been investigated as a function of different oxygen fractions (, 0.38, 0.61, 0.76 and 0.9). At room temperature, the film deposited at exhibits a strong, broad PL band peak centred at around 537.6 nm. A blue shift and a considerable decrease (∼one order) in the intensity of the PL peak are observed after the addition of oxygen. Furthermore, in contrast to the film deposited from pure HMDSO, the low temperature (15 K) PL spectra of the film deposited from different HMDSO/O2 mixtures exhibit two separated ‘green–blue’ and ‘yellow–green’ PL peaks. The PL behaviour of the deposited films is correlated with their structural and morphological properties, investigated by using Fourier transform infrared, atomic force microscope and contact angle techniques. In addition, it is found from spectrophotometry measurements that the deposited films have relatively low absorption coefficients (in the range 100–500 cm−1) in the spectral range of their PL emission, attractive for possible integrated optics devices.

Properties of thin films deposited from HMDSO/O 2 induced remote plasma: Effect of oxygen fraction

Thin films deposited from Hexamethyledisiloxane (HMDSO)/O 2 mixture excited in a radio-frequency hollow cathode discharge system have been investigated for their structural, optical and corrosive properties as a function of oxygen fraction χ O 2 ( χ O 2 = 0 , 0.38 , 0.61 , 0.76 and 0.90 ). It is found that the effect of oxygen fraction on films properties is related to O 2 dissociation degree ( α d) behavior in pure oxygen plasma. α d has been investigated by actinometry optical emission spectroscopy (AOES) combined with double Langmuir probe measurements, a maximum of O 2 dissociation degree of 15% has been obtained for 50 sccm flow rate of O 2 ( χ O 2 = 0.61 in HMDSO/O 2 plasma). Fourier transform infrared spectroscopy (FTIR) and optical measurements showed that the behavior of both identified IR group densities and deposition rate as a function of oxygen fraction is similar to that of O 2 dissociation degree. The inorganic nature of the films depends significantly on oxygen fraction, the best inorganic structure of deposited films has been obtained for 62% HMDSO content in the mixture HMDSO/O 2 ( χ O 2 = 0.38 ). The refractive index for deposited films from pure HMDSO ( χ O 2 = 0 ) has been found to be higher than that of films deposited from HMDSO/O 2 mixture. In HMDSO/O 2 plasma, it has a behavior similar to that of deposition rate, and it is comparable to that of quartz. The effect of oxygen fraction on the corrosive properties of thin films deposited on steel has been investigated. It is found that the measured corrosion current density in 0.1 M KCl solution decreases with the addition of O 2 to HMDSO plasma, and it is minimum for χ O 2 = 0.38 .

Effect of oxygen fraction on local entropy generation in a hydrogen–air burner

This study considers numerical simulation of the combustion of hydrogen with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to the high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio (ϕ) and oxygen percentage (γ) on the combustion and entropy generation rate are investigated for different ϕs (from 0.5 to 1.0) and γs (from 10 to 30%). The combustion is simulated for the fuel mass flow rate providing the same heat transfer rate \((\dot{Q})\) to the combustion chamber in the each case. The numerical calculation of combustion is performed individually for all cases with the help of the Fluent CFD code. Furthermore, a computer program has been developed to calculate numerically the volumetric entropy generation rate distributions and the other thermodynamic parameters by using the results of the calculations performed with the FLUENT code. The calculations bring out that the increase of ϕ (or the decrease of λ) reduces significantly the reaction rate levels. The average temperatures in the combustion chamber increase about 70 and 23% with the increases of γ (from 10 to 30%) and ϕ (from 0.5 to 1.0), respectively. With the increase of γ from 10 to 30%, the volumetric local entropy generation rates decrease about 9 and 4% in the cases of ϕ=0.5 and 1.0, respectively, and while the total entropy generation rates decrease exponentially, the merit numbers increase. The useful energy transfer rate to irreversibility rate therefore improves as the oxygen percentage increases.

The Effects of Oxygen on Coal Gasification Characteristics.

The effects of oxygen on coal gasification characteristics have been investigated by using Drop Tube Furnace. In the pyrolysis tests the influences of oxygen in the oxidizer have been examined, and results show that the reactions in which oxygen don't take part isn't influenced by pressure. The gasification tests with changing oxygen fraction in oxidizer have been done, and results show that, for the high volatile matter coal gasification efficiency isn't influenced by oxygen fraction, but for the low volatile matter coal, it is improved by increasing the oxygen fraction. Moreover, the reactivity of the low volatile matter coal has been investigated, and the effects of oxygen fraction are clarified by comparing the effects of the temperature and the residence time of coal particle.

Effects of oxygen fraction in inspired air on rowing performance

The present study examined the effect of oxygen fraction in inspired air (FIO2) on exercise performance and maximum oxygen consumption (VO2max). Six national level male rowers exercised three 2500-m all-out tests on a Concept II rowing ergometer. Each subject performed one test in normoxia (FIO2 20.9%), one in simulated hyperoxia (FIO2 62.2%) and one in simulated hypoxia (FIO2 15.8%) in a randomized single-blind fashion. The mean final rowing time was 2.3 +/- 0.9% (P < 0.01; 95% CI 1.4-3.2) shorter in hyperoxia and 5.3 +/- 1.8% (P < 0.01; 95% CI 3.1-7.5) longer in hypoxia when compared with normoxia. The effect of FIO2 on VO2max exceeded its effect on exercise performance as VO2max was 11.1 +/- 5.7% greater (P < 0.01; 95% CI 5.1-17.1) in hyperoxia and 15.5 +/- 3.2% smaller in hypoxia (P < 0.01; 95% CI 12.2-19.0) than in normoxia. Blood lactate concentration and O2 consumption per power unit (ml O2.W-1) failed to indicate statistically significant differences in anaerobic metabolism between normoxia and the other two conditions. These data suggest that there are other parameters besides those of energy metabolism that affect exercise performance as FIO2 is modified. These possible mechanisms are discussed in this paper.