Increasing Gas Flow Rate Research Articles

Effect of nitrogen flow rate on the properties of nitrogen-doped Cu<sub>2</sub>O

Cuprous oxide (Cu₂O) has the potential applications in photovoltaic and photocatalytic fields. Nitrogen-doping in Cu₂O can improve the conductivity by increasing hole concentration. However, the chemical states of nitrogen in nitrogen-doped Cu₂O have not been studied thoroughly.A series of nitrogen-doped Cu₂O samples are prepared by increasing nitrogen flow rates and simultaneously keeping the sputtering pressure and other parameters unchanged. The samples are characterized by X-ray diffraction (XRD), step instrument, scanning electron microscope (SEM), energy dispersive spectrometer, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), spectrophotometer and Hall effect et al. The results of Hall effect measurement show that nitrogen-doping can increase the hole concentration by one order of magnitude. The band gap width decreases with the increase of nitrogen flow rate. The nitrogen in Cu₂O is in three forms: β-N (nitrogen atom), α-N₂(molecular nitrogen, —N=N—)and γ-N₂(molecular nitrogen, N≡N). With the increase of nitrogen gas flow rate, the peak of binding energy of β-N increases while that of α-N₂ decreases. The sample prepared at the nitrogen flow rate of 2.0 sccm has the minimum resistivity among all samples.

Gasification of cotton stalk in a downdraft gasifier

ABSTRACTDemand of energy is ever increasing and sustainable form of energy supply is needed. Fossil fuels utilization causes a lot of environmental pollution. Biomass is a renewable, sustainable, and environment friendly form of energy and can be used to fulfill energy needs. Gasification of biomass can be employed to use it efficiently. In the present work, trials were performed on gasification of biomass in a downdraft gasifier. The specific biomass consumption was reasonably constant with a mean value of 0.462 kg/h for all gas flow rates. The temperature of the various zones increased as the producer gas flow rate increased. The temperature of the oxidation zone rose from 580 to 725°C with increase in the gas flow rate from 7 to 19 Nm3/h. The volume percentage of the CO and H2 rose somewhat with rise in gas flow rate. The producer gas calorific value was higher at higher gas flow rates. Tar content of the producer gas was lower than the permissible limits at all gas flow rates except for very low gasification rate. The particulate matter content in the gas was somewhat higher than the permissible limits. The gasifier efficiency ranged between 69.57% and 74.48% as the gas flow rate varied from 7 to 19 Nm3/h.

Study on Flame Characteristics during Biodiesel Combustion in Industrial Furnaces

The effect of different oxygen contents (21%, 24%, 27%, and 30%) and gas rate flows (27, 29, 31, 33, and 35 m3/h) on flame characteristics during the biodiesel combustion, such as flame length, area, brightness, and breakage degree, were studied using a homemade industrial furnace combustion system. The method consisted of keeping the fuel supply constant while increasing the flow of gas from 27 to 35 m3/h in 4 s in addition to cross tests with different oxygen contents (21%, 24%, 27%, and 30%) and gas rate flows (27, 29, 31, 33, and 35 m3/h). The results showed that oxygen-rich combustion gases have an enormous advantage in biodiesel combustion. As the gas flow rate increases, the flame length, flame brightness, and flame area gradually decrease but the flame breakage gradually increases. The flame can be stably burned under high gas flow rate: the gas supply amount is constant, as the oxygen concentration increases, the flame length and area increase, but the flame breakage decreases. As the gas supply ...

Investigation into the ionization and acceleration regions shift in a Hall thruster channel

Location of the ionization and acceleration regions determines erosion belt location and thruster’s maximum throughput consequently. For Hall thrusters with wide throttle ratio the location of the ionization and acceleration regions in each operating mode could vary significantly, which makes it difficult to provide necessary throughput for multi-mode operation. In this article, the shift of the ionization and acceleration region location caused by the change of operating mode is studied with the help of numerical method. Numerical investigation was conducted with 1D3V hybrid-PIC simulations. According to the results, the ionization and acceleration regions could move upstream significantly with gas flow rate increase and magnetic field decrease. In addition, it was proved that an increase in the magnetic field gradient shifts the ionization and acceleration region location outside of the channel significantly. The trends obtained in numerical simulations were experimentally testified. The acceleration region trend validation was carried out with electrical probe measurements on a 1.5 kW laboratory Hall thruster. The ionization region shift was validated with the shift of the maximum light intensity of the xenon inside the channel of a 2.3 kW laboratory Hall thruster. Moreover, experimental investigations indicate that the ionization and acceleration regions could move significantly when oscillation mode changes.

Deposition characteristic of micro-nano soluble aerosol under bubble scrubbing condition

Bubble scrubbing is recommended as a potential way to remove aerosol under accident conditions not only because of its sufficient specific transfer area and considerable residence time but also the feasibility of the concept. The purpose of this paper is to illuminate the effect of operating parameters such as liquid height, gas flow rate on micro-nano soluble aerosol deposition characteristic under bubble scrubbing condition. The results indicate that a strong hygroscopic growth phenomenon happened under bubble scrubbing condition. A direct effect is change in deposition mechanism and the deviation of MPPS. Liquid height can significantly improve the removal efficiency of micro-nano aerosol and present a more obvious influence on inertial-dominant aerosol than Brownian one. The increase of gas flow rate can weaken the deposition efficiency in range of 0–0.6 m3/h but will reverse to enhancement effect when exceeding 0.6 m3/h.

Experimental Investigation on Metallic Droplet Behavior in Molten BOF Slag

In order to better understand the metallic droplet behavior during a slag treatment process, a physical modeling based on the similarity principle was performed in a transparent scaled-down vessel at room temperature. Paraffin oil, 20 wt pct copper sulfate solution, and compressed air were used to simulate the molten slag, metallic droplet, and carrier gas, respectively. The droplets injected into paraffin oil during the experiment were captured by a high speed camera and were analyzed by Image Pro Plus software to obtain the droplet size distribution. The critical droplet size in the physical modeling and slag treatment process is quantitatively correlated. The results show that droplet breakage phenomenon is dominant over its coalescence in the current industrial practice, and droplet breakage is enhanced with increasing gas flow rate and/or lance depth. No significant effect of the nozzle configuration was found on the droplet breakage and coalescence. The droplet size distribution varies with the lance position. Gas flow rate and lance depth are the most important factors for droplet breakage, the extent of which can be reduced through a proper selection of the operational conditions. A linear relationship between the droplet size and the input energy flux is obtained.

The Dependence of N2 Carrier Gas Flow Rate on Deposition Rate and Density Changes of Porous Silica Preform Synthesized by Eco‐Friendly Octamethylcyclotetrasiloxane

A porous silica preform for the fabrication of optical fibers is generally synthesized by flame hydrolysis deposition (FHD). To synthesize the porous silica preform, SiCl4 containing chlorine (Cl) is normally used. However, the Cl generated through the FHD process is highly reactive and generates toxic substances, which seriously affect the environment. In this study, the porous silica preform with a radius of more than 250 mm is synthesized using vaporized octamethylcyclotetrasiloxane (OMCTS), which does not contain the Cl. In addition, the effect of the N2 carrier gas flow rate on the deposition rate of the silica soot and the density of the porous silica preform are investigated. As the carrier gas flow rate increases, the deposition rate decreases and the density of the porous silica preform tends to increase. This result may be due to the difference in the substrate and flame temperature gradients depending on the carrier gas flow rate. The characteristics of the porous silica preform are investigated at the top, middle, and bottom positions. Regardless of the position, the porous silica preform is composed of spherical silica particles with the size of 100–200 nm.

Droplet transfer behaviour in twin-body plasma arc welding

A novel process, named twin-body plasma arc welding (PAW), is proposed in this study. In this novel process, the wire is used as introduced electrode to adjusting the energy distribution between base metal and droplet, and a strong plasma flow force is applied to the droplets. To understand the characteristics of droplet transfer behaviour in this process, this paper analyses the changes in the forces acting on the droplet and carry on experiments to study the effect of the current separation ratio and plasma gas flow rate on droplet transfer behaviour. The results show that as the current separation ratio increases, the total energy acting on the droplet and the promoting force of droplet transition are enhanced, and the droplet transfer behaviour and wire melting speed are changed significantly. As the plasma gas flow rate increases, the plasma flow force is enhanced, and the droplet transfer behaviour is changed, but the droplet transfer position is almost unchanged. Through reasonable parameter matching, the spray transfer could be realized under low current, and the droplet transfer mode could be freely changed from globular to spray when the total current remains unchanged.

• THE INFLUENCE OF CARBONIC ACID AMMONIUM SALTS ON THE FILTRATION PROPERTIES OF BOTTOM-HOLE FORMATION ZONE

The possibility of using ammonium carbonates to increase hydrocarbons extraction is considered. To study the effect of ammonium carbonate salts on the reservoir filtration properties a complex of experimental studies has been carried out. It has been established that carbon dioxide ammonium salts, in the absence of calcium chloride water, interact with carbonate rocks, increase the absolute permeability of reservoirs. The solutions of ammonium carbonate salts interact with calcium chloride type of formation water and form chemically precipitated chalk in the pores of the rock. Herewith the permeability of carbonate rocks decreases. The industrial tests of ammonium carbonate salts have shown an increase in gas flow rate by 30-50% at wells № 23 of Opishnyanske, № 115 of Mashivske, № 3 of Tymofiyivske gas condensate fields. The effect of the ammonium carbonates treatment of the formation is stipulated by the purification of the bottom-hole formation zone and an increase of the absolute permeability of the reservoirs. The increase of the condensation factor by 22-35% has been observed in wells № 56, 108 of Yablunivske and № 58 of Tymofiyivske gas condensate fields. The efficiency of the treatment is related to the simultaneous purification of the bottom-hole zone from asphalt-resinous contaminants and to the absolute permeability increase, as well as to the pore space hydrophilization and the increase in the mobility of condensate that has fallen due to the influence of carbon dioxide which generates as a result of the decomposition of carbonic acid ammonium salts. Thus, pilot tests at Opishnyanske, Mashivske, Tymofiyivske, Yablunsvske gas condensate fields of Poltava region confirmed the effectiveness of using ammonium carbonate salts to increase hydrocarbon production. The prospect of further research is aimed at developing a technology for increasing the liquid hydrocarbons production by the use of ammonium carbonate salts.

Effect of microchannel junction angle on two-phase liquid-gas Taylor flow

Two-phase liquid-gas Taylor flow triggered by blocking-squeezing mechanism was studied with different junction angle θ microchannels, i.e. 20°, 45°, 90°, 135° and 160°, at various liquid (ethanol) and gas (He) flow rates. We experimentally investigated the effects of flow rates and θ on the gas bubble VB and liquid slug VS volumes. A theoretical model was formulated for the quantitative predictions of bubble and slug sizes for different θ and flow rates. Good agreements were obtained between theoretical predictions and experimental observations. The unit cell volume VU (VB + VS) decreased pronouncedly for the 20° channel with decreasing liquid or increasing gas flow rate, due to the slight increase in VB and large decrease in VS. In comparison, for the 45°, 90°, 135° and 160° channels with increasing liquid or decreasing gas flow rate, VU were less sensitive to fluid flow rate changes, due to the approximate cancellation between VB decrease and VS increase. For the 20° and 45° channels, it produced larger VU, due to larger VB and VS, when compared to the 90° channel. This is caused by the larger gas bubble throat width DN at the junction when θ < 90°. As for the 135° and 160° channels (θ > 90°), DN is approximately equal to the gas channel width, with VB, VS and VU approximately the same as the 90° channel. With θ ≥ 90° (i.e. 90°, 135° and 160° channels), as evident from the smaller VU, higher gas bubble density can be obtained when compared to θ < 90° (i.e. 20° and 45° channels). Hitherto, this observation has not been realized, and the mechanics is first investigated here with the employment of extreme θ (i.e. 20° and 160°). A thorough understanding of the underlying mechanics affecting Taylor flow can facilitate its exploitation for controlled gas bubble and liquid slug generation. Our theoretical model facilitates the tuning of the channel designs and fluid flow rates to achieve the desired gas bubble and liquid slug sizes for specific applications.

Experimental and numerical study on the transition conditions and influencing factors of hetero-/homogeneous reaction for H2/Air mixture in micro catalytic combustor

Premixed combustion of Hydrogen/Air in a rectangular micro-catalytic combustor was investigated experimentally and numerically. The distribution of OH radicals in the combustor was observed by Plane Laser-Induced Fluorescence (PLIF). A method for determining the transition process of reaction types in the combustor by measuring temperature variation was proposed. The effects of combustor height and mixed gas flow rate on the transition characteristics of reaction type were analyzed and the results demonstrated that the reaction type would transform with the change of equivalence ratio between the coupled hetero-/homogeneous reaction (catalytic and gas phase reaction) and the pure heterogeneous reaction (pure catalytic reaction). The critical equivalence ratio from coupled hetero-/homogeneous reaction transforming into pure heterogeneous reaction is ФA. The critical equivalence ratio from pure heterogeneous reaction to coupled hetero-/homogeneous reaction is ФB. At different combustor heights and mixed gas flow rates, ФA is always less than ФB. When the height of combustor increases, the critical equivalence ratio ФA decreases while the critical equivalence ratio ФB increases. The critical equivalence ratios ФA and ФB both decrease with the increase of mixed gas flow rate. Heat loss on the combustor outer wall has an important influence on the transformation of reaction type.

Effects of Nozzle Radial Position, Separation Angle, and Gas Flow Partitioning on the Mixing, Eye Area, and Wall Shear Stress in Ladles Fitted with Dual Plugs

Mixing time, slag eye area, and wall shear stress in a ladle fitted with dual plugs have been studied as a function of operating variables, namely, gas flow rate, radial nozzle position, separation angle between nozzles and flow rate partitioning. While the mixing time and slag eye area have been experimentally investigated in a scaled water model (with and without a top slag layer), the shear stress on the vessel wall has been studied computationally via a RANS-based turbulent, three-dimensional coupled Eulerian–Lagrangian (VOF-DPM), multiphase flow model. Experimental and computational results have indicated that the mixing, eye area, and wall shear stress depend on the gas flow rate, i.e., while mixing efficiency increases with the increasing gas flow rate, the slag eye area, and wall shear stress, in contrast, become more pronounced with the increasing gas flow, leading to an undesirable operating regime. The radial nozzle position, separation angle between the nozzles and flow rate partitioning at any given flow rate also influence the ladle process performance, influencing the mixing, eye area, and wall shear stress, albeit to a varied degree. Within the range of operating conditions studied, an expected inverse correspondence between mixing time and shear behavior was observed. Experimental and computational results in conjunction have indicated that the best arrangement of porous plugs or gas injection nozzles for superior ladle process performance is dependent on the gas flow rate and is specific to the desired objective (i.e., decreasing the mixing time, or slag eye area and wall shear stress). Hence, a unique gas injection practice cannot and should not be suggested as the optimum for ladle metallurgy in steelmaking. Nevertheless, if the mixing time is the parameter of primary interest, a nozzle configuration with equal flow partitioning (1:1) between the nozzles and identical nozzle radial positions (0.7R/0.7R, 45 deg) should suffice for both low and high gas flow rates. In contrast, a nonidentical nozzle radial position (0.7R/0.5R, 90 deg) and an unequal gas flow rate per nozzle (1:3) appear preferable if both ladle eye and shear stresses, rather than mixing, are the issues of concern.

Computational Fluid Dynamics (CFD) Simulations and Experimental Measurements in an Inductively-Coupled Plasma Generator Operating at Atmospheric Pressure: Performance Analysis and Parametric Study

In this article, electrical characteristics of a high-power inductively-coupled plasma (ICP) torch operating at 3 MHz are determined by direct measurement of radio-frequency (RF) current and voltage together with energy balance in the system. The variation of impedance with two parameters, namely the input power and the sheath gas flow rate for a 50 kW ICP is studied. The ICP torch system is operated at near atmospheric pressure with argon as plasma gas. It is observed that the plasma resistance increases with an increase in the RF-power. Further, the torch inductance decreases with an increase in the RF-power. In addition, plasma resistance and torch inductance decrease with an increase in the sheath gas flow rate. The oscillator efficiency of the ICP system ranges from 40% to 80% with the variation of the Direct current (DC) powers. ICP has also been numerically simulated using Computational Fluid Dynamics (CFD) to predict the impedance profile. A good agreement was found between the CFD predictions and the impedance experimental data published in the literature.

New development of double dielectric barrier discharge (DBD) plasma reactor for medical

Effect of gas source and flowrate to ozone concentration and capacity was investigated using double DBD plasma reactor with cylinder-cylinder configuration. The high AC voltage was applied in the range of 200-500 Volts and the frequency of 50 Hz. Gas sources; i.e. free air and pure oxygen; flowed into the reactor with several variations in flow rate, i.e. 2 to 24 L/min. The results showed that the ozone concentration decreased with increasing gas flow rate. Free air sources produced smaller ozone concentration and capacity compared to those produced using a pure oxygen source (O2). While the ozone capacity increases with increasing gas flow rate. The pure oxygen (O2) with a flow rate of 24 L/min had produced ozone concentration of 2.2 mg/liter and ozone capacity of 52.8 mg/min. A number of further studies need to be conducted related to the effect of voltage, diameter, and length of the electrode to obtain lower ozone concentration and capacities, for ozone applications in medical therapy. The suitable dose of ozone therapy for medical can be used for wound healing and chronic disease.

Microscale wave breaking in stratified air-water pipe flow

We perform an experimental analysis of two-phase stratified wavy pipe flow, with the aim to detect and quantify the effect of small scale wave breaking. Particle image velocimetry is employed to analyze the velocity fields below individual waves, and a threshold for the vorticity on the leeward side of the crest is used to assess active wave breaking. Keeping the liquid flow rate constant, we analyze five experimental cases with increasing gas flow rates. The cases span the flow map from when first interfacial waves are observed, to the “amplitude saturation” regime, where the rms interface elevation is independent of the gas flow rate. While some wave breaking events are observed also in the wave-growth regime, wave breaking is found to be much more frequent when the gas flow rate is increased into the amplitude saturation regime, and 35%-40% of the waves passing the measurement section are assessed to be in a state of active breaking in this regime. A conditional averaging of the flow field is performed, and the turbulent dissipation rate below breaking and non-breaking waves is estimated. The effect of microscale breaking is observed down to a depth of 10 mm below the water surface. Below the crest of microscale breaking waves, the turbulent dissipation rate is increased by a factor 2.5 to 4 compared with non-breaking waves. This fraction increases with Usg, implying that the breaking events become more energetic as the gas flow rate is increased.

Continuous bubble reactor using carbon dioxide and its mixtures for ballast water treatment

The treatment of ballast water is indispensable for preventing ecological and economic damage from the spread of invasive species. In this study, a continuous gas bubble reactor (CBR) system was developed for the efficient disinfection of microorganisms in ballast water. Ballast water treatment (BWT) in the CBR was experimentally performed to disinfect Artemia salina in seawater by using 1) pure CO2 and 2) mixtures with CO2, N2, and/or SO2 as a simulated flue gas (CO2/N2: 20%/80% and CO2/N2/SO2: 19.2%/77.0%/3.8%). The BWT efficiency was improved with an increase in gas flowrate, residence time, gas pressure, and CO2 concentration in the gas. The toxicity of SO2 in the CO2 mixture significantly improved the mortality of microorganisms. Since good dispersion of bubbles and effective contact between bubbles and liquid were important factors in the BWT, a 100% mortality rate of microorganisms could be achieved by controlling the operating conditions in the vertical-type CBR with a counter-current flow between the gas bubbles and seawater. The CO2 gas distribution, CO2 solubility, and gas bubble size distribution in the CBR were determined using computational fluid dynamics (CFD) and experimentally confirmed using a high-speed camera. Since excess gas can be recovered from a gas-liquid separator before a ballast tank, the CBR system can be operated without using any toxic or explosive gases in an eco-friendly and energy saving manner.

Flow dynamic in a packed bed filled with Ni‐Al2O3 porous catalyst: Experimental and numerical approach

AbstractNumerical simulations and experiments have been carried out to explore the effect of particle shapes on the pressure drop and the loss factor in a packed fixed bed filled with a porous catalyst. The packed bed is presented by the Ni‐Al2O3 catalyst of the different shapes. The commercial program ANSYS Fluent is used for the analysis; more than 20 mln cells are used for computational fluid dynamics (CFD) modeling. The catalyst particles were set as a porous medium with the viscous resistance coefficients and the inertial resistance coefficients. The comparison of the pressure drops between the experimental and simulation results show a good correlation with the divergence of results &lt;8%. To determine the effect of the porosity properties of the medium on the numerical results, two cases of CFD modeling were realized (with taking into account the porous medium properties and without it). The discrepancy between results increases with an increasing gas flow rate.

Experimental studies of air-blast atomization on the CO2 capture with aqueous alkali solutions

Abstract In this work, an air-blast atomizing column was used to study the CO2 capture performance with aqueous MEA (mono-ethanol-amine) and NaOH solutions. The effects of gas flow rate, the liquid to gas ratio (L/G), the CO2 concentration on the CO2 removal efficiency (η) and the volumetric overall mass transfer coefficient (KGav) were investigated. The air-blast atomizing column was also compared with the pressure spray tower on the studies of the CO2 capture performance. For the aqueous MEA and NaOH solutions, the experimental results show that the η decreases with increasing gas flow rate and CO2 concentration while it increases with increasing L/G. The effects on KGav are more complicated than those for η. When the CO2 concentration is low (3 vol%), KGav increases with increasing gas flow rate while decreases with increasing L/G. However, when the CO2 concentration is high (9.5 vol%), as the gas flow rate and L/G increases, KGav increases first and then decreases. The aqueous MEA solution achieves higher η and KGav than the aqueous NaOH solution. The air-blast atomizing column shows a good performance on CO2 capture.

Large-scale surface modification to improve hydrophilicity through using a plasma brush operated at one atmospheric pressure

A uniform plume with pulsed discharges is generated through using a plasma brush excited by a direct current power supply. The results indicate that the plume length increases with the increasing gas flow rate or dissipated power. The optical emission spectrum from the plasma brush reveals that active species are abundant in the plasma plume. Based on the spectrum, an electron density on the order of 1014 cm−3 is obtained, which increases with the increasing dissipated power and gas flow rate. After a single scan of the plasma brush on the polyethylene terephthalate surface, a uniform surface modification is achieved with an improved hydrophilic width of about 24 mm. The water contact angle of the surface decreases with the decreasing scanning velocity and nozzle-sample distance or the increasing dissipated power and gas flow rate. Moreover, the treated surface shows an aging behavior in 6 days. Raman spectra indicate that oxygen-containing polar groups are generated on the treated polyethylene terephthalate surface. The polar groups are contained in oxidized materials, which are observed by scanning electron microscopy.

Removal of hydrogen sulfide on activated carbon supported ionic liquids

In this study, ionic liquid loaded activated carbon was applied as the adsorbent for hydrogen sulfide (H2S) removal under the anaerobic conditions in a fixed bed. The effects of activated carbon substrate, ionic liquid, initial H2S concentration and flow rate on the adsorption process were systematically studied. The experimental results show that the activated carbon named AC-1 having higher surface area and micropore volume is more suitable as the support for ionic liquid. Amongst three ionic liquids studied, the 1-ethyl-3-methylimidazolium acetate loaded activated carbon exhibites the highest H2S sorption capacity performance. As a results of the superior performance of the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, further tests and characterizations were performed on the sorbent. The breakthrough capacity of 1-ethyl-3-methylimidazolium acetate sorbent is two times greater than pure activated carbon. In addition, it is confirmed that increasing H2S concentration enhances H2S adsorption capacity, and the adsorption capacity of H2S decreases significantly with increasing gas flow rate.