Oxygen Jet Research Articles

Experimental and Numerical Investigation on Flow Condensation Process of Oxygen Jet in Crossflow of Liquid Oxygen

Experimental and Numerical Investigation on Flow Condensation Process of Oxygen Jet in Crossflow of Liquid Oxygen

Effect of Lance Design on Jet Characteristics in 250 t Converter

The supersonic jet characteristics of the oxygen lance nozzle play an important role in converter melting. However, limited studies have investigated the different nozzle arrangements to improve the jet characteristics. This study uses FLUENT to establish a compressible nonisothermal computational fluid model with a 250 t converter as the object, and the model first validates and then discusses the effects of the center hole and postcombustion (PC) oxygen lance secondary hole on the aggregation behavior and impact area of the oxygen jet based on the conventional five‐hole oxygen lance. The study shows that, at the same distance, the influence of the peripheral jet offset degree from small to large is secondary hole–center hole–secondary hole with center hole. At the lance height of 1900 mm, compared to the traditional five‐hole oxygen lance offset theoretical axial centerline distance is 1.98, 2.31, and 3.20 times. The larger the jet migration degree of the peripheral hole, the smaller is the velocity of the peripheral jet. The presence of center hole, secondary hole, and center hole with secondary hole encloses 1.04, 1.09, and 1.47 times the area enclosed by the conventional five‐hole oxygen lance at 150 m s−1 isovelocity line, respectively.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 3. The picture of bath blowing at application two-level oxygen lances

Further increase of resources- and energy-saving efficiency of BOF processes is unthinkable without development of new methods of blowing and designs of blowing devices. It requires information on the real physicochemical phenomena in the converter cavity accompanying the blowing of the converter bath using new designs of oxygen lances in order to assess the possible risks in the mastering of the proposed developments in industrial conditions. The paper presents the results of video filming of the top blowing of a 80-kg converter bath by groups of multi-pulse supersonic and sonic oxygen jets formed, respectively, by Laval and cylindrical two-level nozzles of two designs equipped with double-row tips with a circular arrangement of Laval nozzles and cylindrical ones and upper block with cylindrical nozzles. Previously unknown information was obtained on the picture of the bath blowing with the formation of a reaction zone of interaction of supersonic and sonic oxygen jets with a metal melt with a flow of carbon monoxide going out the bath and afterburning of CO to CO2 under conditions of a counter-directed double curtain of sonic oxygen jets at different levels of location of the foamed slag-metal emulsions. It was established that in the initial period of blowing during slag formation most of the thermal energy of CO to CO2 combustion flares is transferred to the surface of the bath with lumps of added lime, and the rest is transferred by forced convection to the converter walls and gases escaping from the bath to the neck. In the case of the location of the foamed slag level at the upper tier of the cylindrical nozzles of the lance, heat transfer from high-temperature flares of localized afterburning of CO to CO2 within a limited in size near-lance flow of exhaust gases from the reaction zone is carried out according to the laws of submerged combustion and is completed completely in foamed slag-metal emulsion with the prevention of aggressive action of afterburning flares and volumes of overheated slag on the converter lining. Revealed and recorded by video recording modes of blowing the converter bath, contributing to the development of such undesirable phenomena during smelting as the appearance of intense emissions of slag-metal suspension from the facility, coagulation of the slag with the cessation of dephosphorization of the metal melt, the development of intense dust formation and the removal of small metal particles and slag with the formation of crust on the lance barrel. A variant of the final stage of blowing with a transition to supplying nitrogen instead of oxygen through cylindrical nozzles of two-level lances was experimentally tested, which provides an effective reduction in the level of foamed slag-metal emulsion before the converter turning down. The data obtained were used in the development of an industrial design of a two-level lance with a double-row tip, blowing and slag modes of blowing a converter bath with its use.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 1. Facility and methodology of the study

Interaction of the upper oxygen jets with the BOF bath considerably effects the hot metal refining flow. To optimize the lances designs and methods of BOF bath blowing, information is needed on the actual physical and technical phenomena taking place during top blowing of BOF bath by groups of ultrasonic and sonic oxygen jets. It was shown that obtaining the information is possible at high temperature simulation of the BOF bath blowing by application oxygen lances of various designs and video registration. Results of previous studies by filming of the blowing in a BOF and OHF presented. Description of modern facilities of high temperature simulation within a multi-purpose 160 and 60‒80 kg BOFs, equipped by special manholes for observation and registration by video camera the physicochemical processes taking place on the surface of the bath presented. In particular the manholes made it possible to observe the processes taking place at various methods of top and combined blowing of the BOF bath by application regular, two-circuit and double-flow oxygen lances. A methodology of test heats carrying out presented, which ensured obtaining important practical information on forming and variation of dimensions of the reaction zone. In particular, information was obtained about the interaction of ultrasonic and sonic oxygen jets with the metal melt, development of afterburning, emission out of reaction zone C to CO2 in the subsonic and sonic oxygen jets with forming high temperature flares directed on the BOF bath surface or penetrated in the foamed slag, emissions of slag-metal suspension out the BOF, forming of metal-slag sculls on the lance tube during the blowing with various level of foamed slag-metal emulsion.

Magnetospheric Multiscale Observations of an Expanding Oxygen Wave in Magnetic Reconnection

AbstractHeavier plasma species such as oxygen ions can have a large impact on the magnetic reconnection process. It has been hypothesized that the acceleration of demagnetized oxygen ions by the Hall electric field will lead to the formation of an oxygen wave that expands into the exhaust. By comparing data from NASA's Magnetospheric Multiscale mission to a fully kinetic particle‐in‐cell simulation, we can for the first time provide observational evidence of such an expanding oxygen wave. The wave is characterized by an oxygen jet consisting of cold ions directed toward the neutral sheet associated with a density cavity. This density cavity forms as the are subject to collective acceleration by the Hall electric field leaving behind a region of low‐density oxygen ions. Our results are important for the understanding of the role and effect of oxygen ions in magnetic reconnection.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 2. The picture of bath blowing at application two-circuit lances

To elaborate blowing and slag modes, a clear picture of BOF bath blowing in various periods of heat is needed. It can be obtained by video registration of physicochemical processes in a BOF cavity. Results of video filming of BOF bath blowing with application two-circuit oxygen lances of five designs presented. Reliable information was obtained on rational form of organization of reaction zone of interaction of ultrasonic and sonic oxygen jets with BOF bath. The picture of physicochemical processes within the reaction zone of interaction of oxygen jets with metal, slag and gas phases of the cavity, preceded to a stable “ignition” of a heat and in the process of the whole heat. A possibility was revealed to accelerate the processes of lime dissolving and slag formation and phosphor removal intensification. The intensification can be accomplished by increase of the number of reaction zones of interaction of ultrasonic and sonic oxygen jets on bath surface and forming of foamed slag-metal emulsion, being stable within the basic part of blowing time. It was shown that at initial period of a heat, it is necessary to ensure consolidation of supersonic oxygen jets, coming out of different reaction zones of interaction. It will enable to oncoming jets to create a curtain on the way of metal and slag drops taking away, to form a flare of CO afterburning to CO2 and ensure heat energy transfer from them to mainly the bath surface. It was established that at the location of the foamed slag-metal emulsion level higher the head end of the lance, the high-temperature products of CO to CO2 afterburning reaction transfer the heat of CO surrounding macro bubble to the shell of slag-metal emulsion. An additional control effect of “hard” supersonic oxygen jets on the bath was also established when replacing the subsonic and sonic oxygen jets by nitrogen ones. At that the flow rate of nitrogen should be big enough to prevent the sealing of cylinder nozzles of the lance head by metal and slag drops during final stage of blowing. The variant of the final stage of blowing was checked experimentally by transfer to the “hard” supersonic oxygen blow, contributing to final metal and slag oxidation decrease.

Numerical investigation on the direct contact condensation of oxygen jets in a cryogenic pipe

In the present study, the direct contact condensation (DCC) performance of the superheat GOX in subcooling LOX is explored by numerical simulations based on the VOF two-phase model. The flow condensation characteristics are analyzed in a practical condenser of a cryogenic liquid rocket. The coalescence phenomenon of the GOX streams is examined. The possible regimes of the coalescence are summarized and their effects on the condensation performance are explored. Besides, an improved GOX entrance layout is proposed to avoid the coalescence phenomenon and improve condensation performance. The main conclusions are concluded as follows: The gas condensation is the main heat transfer form in most of the pipe region. The bending section of the condenser pipe that connects the vertical section and horizontal section is the most active region for DCC. It is found that there can be two types of coalescences namely, transverse coalescence and longitudinal coalescence. Both coalescence regimes have strong negative effects on the heat transfer ability and condensation performance of the condenser pipe. The improved entrance layout can successfully avoid the coalescence of the GOX streams and reduce the flow distance of the GOX by about 93%. It is also concluded that an improvement of the condenser pipe should be effectively accomplished by controlling the coalescence of the GOX streams after injection.

Effect of Impact Cavity Shape Induced by Supersonic Oxygen Jet on the Dynamic Characteristics of Molten Bath in Converter

The cover image illustrates the numerical simulation of a four-hole supersonic jet impinging on the molten steel bath during the top-blown converter steelmaking process. The modified cavity shape index is put forward to quantitatively describe the scattered cavities profile. Furthermore, the relationship between the cavity shape and dynamic characteristics of the molten bath is also analyzed. Further details can be found in the article, number 2100179, by Qing Liu, and co-workers.

Effect of Impact Cavity Shape Induced by Supersonic Oxygen Jet on the Dynamic Characteristics of Molten Bath in Converter

The cavity shape formed by the impinging of the supersonic oxygen jet on liquid metal surface is of importance to the converter steelmaking process. This work adopts the volume of fluid (VOF) model to numerically study the behavior of four‐nozzle supersonic jet impinging on molten steel bath in a 100 ton converter. First, the model is validated by comparing the jet velocity with that obtained from the literature. After validation, the dynamic interaction between supersonic jet and molten bath is studied. Moreover, the effects of lance height and operating pressure on the impact cavity depth and diameter are investigated. Compared with operating pressure, lance height shows a larger influence on altering the cavity dimensions. To quantitatively describe the profile of the scattered cavities, a dimensionless number called the modified cavity shape index (I cm) is put forward, which has a significant influence on the velocity distribution and specific kinetic energy of molten bath. The modified cavity shape index is found to be a function of the specific kinetic energy. With the modified cavity shape index ranging from 1.47 to 1.72, the dynamic flow of the molten bath becomes beneficial to the stirring and mixing of the molten bath.

Mathematical modelling and numerical optimization of particle heating process in copper flash furnace

A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed. The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft, whilst the convection is dominant in the area below 0.6 m for the particle heating. In order to accelerate the particle ignition, it is necessary to enhance the convection, thus to speed up the particle heating. A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace, aiming to create a lateral disturbance in the gaseous phase around the particles, so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient. Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners. The results show that with the high-speed jet technology, particles are heated up more rapidly and ignited much earlier, especially within the area of the radial range of R=0.3–0.6 m. As a result, a more efficient smelting process can be achieved under the same operational condition.

Effects of ambient temperature and powder gas ratio on jet characteristics of O2 + CO2 and CaO particles injected by a swirl-type oxygen lance nozzle

The dephosphorization of converters is greatly influenced by the amount of lime added and method used. At present, the oxygen jet mixing of a certain proportion of CO2 to participate in converter smelting has been successfully applied; however, there is little research on the jet characteristics and the relationship between gas and solid particles in the process of oxygen jet mixing injection with a swirl oxygen lance.In this study, the effects of ambient temperature and powder gas ratio on the jet characteristics and particle distribution of four hole swirl oxygen lance nozzle were simulated.The results show that with an increase in the ambient temperature, the velocities of the carrier gas jet and CaO particles increase, and the distribution of CaO particles is more concentrated.

Topical Oxygen Jet Therapy (TOJT) for treating infected chronic surgical wounds

ObjectivesTo evaluate the effectiveness of Topical Oxygen Jet Therapy (TOJT) in the treatment of surgical wounds in adult patients who has clinical signs of infection for over 30 days; and to identify the pathogens causing complicated skin and soft tissue infections. MethodParallel, randomized clinical trials randomly divided into “Control Group” (CG) and “Treatment Group” (TG), which were followed up for 10 consecutive days. Venous antibiotics and dressings were used in both groups. In addition, TOJT were used on the wounds in the TG. The outcome criteria were based on clinical indicators: Pressure Ulcer Scale for Healing (PUSH) and Visual Analog Scale Pain (VAS). The paired t-test or Wilcoxon, chi-squared or Fisher’s exact test, and Student’s t-test or Mann–Whitney tests were used with a significance level of 5%. Results73 inpatients were included and followed up: 39 in TG and 34, CG. There were no significant differences in socio-demographic variables or of initial laboratory tests, except for blood glucose that was higher in TG than in CG (p = 0.044). Ten days into treatment, both the area of PUSH wounds (p < 0.001) and the pain scale (p = 0.029) were significantly reduced in TG. Staphylococcus aureus was the most prevalent pathogen (40%) with no significant difference between the two groups. DiscussionAlthough the follow-up time was of only ten days, a significant improvement was observed in TG. As a limitation of the study, the small sample size precluded the comparison of S. aureus infections between the two groups. ConclusionTOJT accelerated the healing process, reduced pain and contributed to an improvement in the clinical status of the wounds when compared to CG. These findings demonstrate the effectiveness and relevance of the employed technique. It can be easily incorporated as a routine procedure in hospitals without extra investment.

Diode laser assisted oxygen cutting of thick mild steel with off-axis beam delivery

Laser assisted oxygen cutting (LASOX) of 20–40 mm thick mild carbon steel is performed using fiber-coupled diode lasers with a combined optical power of 400 W. The experimental cutting head assembly is designed to deliver the laser beam off-axis to the cutting oxygen jet. Under this non-standard beam delivery conditions, the top edge of the cut may suffer from an excessive melting, overheated by the inclined laser beam. We propose a strategy in order to diminish the top edge melting defect and demonstrate that high quality cuts can be obtained in 20 mm thick workpieces, and lower quality separation of up to 40 mm steel thickness. The experimental results demonstrate the potential of high-power diode sources in the LASOX cutting method, and the ability of relatively low power, compact and lightweight diode-based systems to cut thick sections of mild steel.

Inhibition of the aflatoxin‐producing fungus Aspergillus flavus by a plasma jet system

This study was aimed to determine the effects of a plasma jet of mixed argon and oxygen (Ar-O2) on Aspergillus flavus growth in potato dextrose broth (PDA). Settings for power, discharge duration, and gas flow rate of the plasma jet system (PJS) were optimized over ranges of 10–20 W, 1–10 min, and 3–9 L/min, respectively. The optimal conditions required to inhibit 100% of A. flavus growth at 30°C for 48 hr were 20 W, 10 min, and 9 L/min, respectively. The PJS inhibited 100% of the A. flavus growth in 20 replicates of infected peeled peanuts. Aspergillus flavus cell walls were destroyed via lipid and cell membrane oxidization, resulting in lost osmotic capability and damaged DNA and enzymes. However, the PJS is limited by a short exposure distance. More power, longer exposure, and increased gas flow might be needed to increase the distance while maintaining 100% microbial growth inhibition. Application to real foods and agricultural products, and upscaling the PJS for industrial use will be assessed in further studies. Practical applications Our proposed plasma system could be applied to postharvested agricultural products such as dried peanuts and chili. However, the technology will require validation before it can be applied in an industrial scale.

Flame temperature analysis in the oxycut process using acetylene gas: a numerical study

To cut metals, the oxycut process uses a preheating flame, usually composed of oxygen and a combustible gas, in addition to a flame-independent jet of oxygen. In the present work, the partially premixed combustion model of a finite volume-based software was applied to analyze the flame temperature in a cutting tip of acetylene. At the torch inlet boundary, the flow rates of oxygen and acetylene were adjusted to sweep a wide range of fuel-oxygen ratio. The results pointed a peak surrounding the stoichiometric ratio, at 3106 °C for the literature and 2650.93 °C for the numerical model, contrasting a deviation of 14.65%. The maximum temperature occurs at 52.38% of oxygen volume for the literature and 50.03% for the model, a difference of 2.35 percentage points only. It is concluded that the results of the numerical approach attained the ends of the research.

Measuring the velocity field of a shear-coaxial, cryogenic flame in a high-pressure rocket thrust chamber

High-speed imaging was used to visualize one of the transcritical flames in a multi-injector, sub-scale rocket thrust chamber at pressures up to 80 bar. Image correlation velocimetry (ICV) was applied to the imaging to obtain quantitative information on the flow field from the shear-coaxial injectors. ICV was used to track surface irregularities on the liquid oxygen (LOX) jet in imaging filtered to blue wavelengths. By choosing the interrogation area carefully, only the LOX jet was effectively tracked, excluding the coaxial H2 flow, and the time-averaged velocity field was reconstructed. Due to the transient nature of the tracked features, which frequently change shape or disappear, the averaged ICV result underestimates the absolute values of velocity. Therefore, the averaged values were scaled by the mean of the instantaneous velocity maxima. A second, reference measurement of LOX jet propagation speed was calculated using dynamic mode decomposition (DMD). The results were consistent following the aforementioned correction of the ICV values. Comparing the ICV fields for two different operating conditions showed a marked difference in the axial velocity distribution and lateral expansion of the LOX jet, demonstrating the potential of the method in studying injection in rocket combustion chambers.

Dense core response to forced acoustic fields in oxygen-hydrogen rocket flames

Oscillatory combustion representative of thermo-acoustic instability in liquid rockets is simulated by experiment and LES calculation to investigate the flame behavior in detail. In particular, we focus on how the velocity and pressure fluctuations affect the behavior of the dense oxygen jet, or ‘LOx core’. The test case investigated is a high pressure, multi-injector, oxygen-hydrogen combustor with a siren for acoustic excitation. First, the LES calculation is validated by the resonant frequencies and average flame topology. A precise frequency correction is conducted to compare experiment with LES. Then an unforced case, a pressure fluctuation case, and a velocity fluctuation case are investigated. LES can quantitatively reproduce the LOx core shortening and flattening that occurs under transverse velocity excitation as it is observed in the experiments. On the other hand, the core behavior under pressure excitation is almost equal to the unforced case, and little shortening of the core occurs. The LOx core flattening is explained by the pressure drop around an elliptical cylinder using the unsteady Bernoulli equation. Finally, it is shown that the shortening of the LOx core occurs because the flattening enhances combustion by mixing and increase of the flame surface area.

Carbon Powder Mixed Injection with a Shrouding Supersonic Oxygen Jet in Electric Arc Furnace Steelmaking

The method of carbon powder mixed injection with a shrouding supersonic oxygen jet was proposed to increase the utilization efficiency of carbon powder and improve the foaming slag operation during the electric arc furnace (EAF) steelmaking process by delivering the carbon powder more deeply into the molten bath. In this study, the fluid flow characteristics of the carbon powder mixed injection with a shrouding supersonic oxygen jet were studied and analyzed using numerical simulations, which were first validated by a cold test experiment. Compared with the conventional carbon powder injection without a shrouding jet, the shrouding supersonic oxygen jet can protect the central gas-powder jet against the entrainment of the surrounding atmosphere, increase the velocity of carbon powder and make the carbon powder cluster together in a longer distance. Furthermore, the industrial application research was carried out in a 50-ton commercial Consteel EAF, and the relative metallurgical effects were also studied. Compared with EAF steelmaking using conventional carbon powder injection without a shrouding jet, the powder consumption, tap-to-tap time, FeO content in the final molten slag and phosphorus content of the final molten steel were reduced by 19.3 kWh/ton, 4 min/heat, 2.6 pct and 1.2 × 10−3 pct, respectively, after using the method of carbon powder mixed injection with a shrouding supersonic oxygen jet.

A Study on the Supersonic Jet Nozzle to Improve of the Operating Efficiency of the Converter Process

Recently, various worldwide studies have been conducted to improve converter operation by modifying the lance nozzle. In this study, a numerical analysis of the lance nozzle was conducted to improve the dephosphorization efficiency, and to reduce blowing time. The lance nozzle was designed in the form of an abnormal expansion type nozzle capable of increasing the oxygen supply rate. ANSYS FLUENT, a commercial flow analysis program, was used to verify the flow characteristics of the supersonic jet. The nozzle shape was designed according to the ratio of exit diameter to throat diameter, and an analysis was carried out based on the change in inlet flow rate, to confirm the influence of the oxygen supply flow rate. The velocity of the oxygen jet was the fastest for the normal expansion type nozzle and decreased with the abnormal expansion type nozzle. In addition, the oxygen jet velocity tended to increase with the oxygen flow rate.

Effect of Furnace Gas Composition on Characteristics of Supersonic Oxygen Jets in the Converter Steelmaking Process.

During the converter steelmaking process, the presence of supersonic oxygen jets can provide oxygen to high-temperature metal baths that promotes chemical reactions in the bath, accelerates the smelting rhythm, and facilitates a uniform distribution of the ingredients in the bath. In this paper, a computational fluid dynamics (CFD) model with combustion reactions is established and compared to the results of combustion experiment. This paper studies the behavior and fluid flow characteristics of supersonic oxygen jets under different environmental compositions under a steelmaking temperature of 1873 K. This validated CFD model can be used to investigate the effect of furnace gas on supersonic oxygen jet characteristics during the converter steelmaking process. The results indicate that the composition of furnace gas has an impact on the characteristics of the oxygen jet. Specifically, as the carbon monoxide (CO) volume fraction increases, the high velocity region of supersonic oxygen jet increases, and the high temperature and the high turbulent kinetic energy regions expand.