Gas-liquid Jet Research Articles

Experimental and computational fluid dynamic study of reacting gas jet in liquid: Flow pattern and heat transfer

The flow behavior of a jet reactor (consisting of a gaseous jet submerged in a molten-metal bath) is very complex. These are operated at high temperatures (1500–3000 K) and need to be contained within a heavy metal enclosure. The design of such reactors requires a prior knowledge of the jet dimensions, flow pattern and heat transfer characteristics. However, the fuel opaqueness and the high temperature of the jet create difficulties in observing the reaction mass visually and therefore the literature contains a very brief account of the experimental measurements of the flow pattern. Hence, a systematic study has been undertaken with a reaction pair (HCl gas jet submerged in aqueous NH 3), which has the potential for simulating the real systems. The present work is concerned with the CFD simulations by employing k–ε turbulence model and large eddy simulations (LES). The measurements and simulations have been carried out over a wide range of gas velocities (53–323 m/s) and these have been compared with the CFD simulations. A comprehensive comparison has also been made between the k–ε and the LES for the mean flow, temperature and the turbulent kinetic energy. An attempt has been made to understand the relative performance of these models. Further, complete energy balance has been established between the energy supply rate through the jet and the energy dissipation rate within the reactor. The plume characteristics obtained from CFD simulations have been compared qualitatively with the photographic images.

Direct numerical simulation of the near-field dynamics of annular gas-liquid two-phase jets

Direct numerical simulation has been used to examine the near-field dynamics of annular gas-liquid two-phase jets. Based on an Eulerian approach with mixed fluid treatment, combined with an adapted volume of fluid method and a continuum surface force model, a mathematical formulation for the flow system is presented. The swirl introduced at the jet nozzle exit is based on analytical inflow conditions. Highly accurate numerical methods have been utilized for the solution of the compressible, unsteady, Navier–Stokes equations. Two computational cases of gas-liquid two-phase jets including swirling and nonswirling cases have been performed to investigate the effects of swirl on the flow field. In both cases the flow is more vortical at the downstream locations. The swirling motion enhances both the flow instability resulting in a larger liquid spatial dispersion and the mixing resulting in a more homogeneous flow field with more evenly distributed vorticity at the downstream locations. In the annular nonswirling case, a geometrical recirculation zone adjacent to the jet nozzle exit was observed. It was identified that the swirling motion is responsible for the development of a central recirculation zone, and the geometrical recirculation zone can be overwhelmed by the central recirculation zone leading to the presence of the central recirculation region only in the swirling gas-liquid case. Results from a swirling gas jet simulation were also included to examine the effect of the liquid sheet on the flow physics. The swirling gas jet developed a central recirculation region, but it did not develop a precessing vortex core as the swirling gas-liquid two-phase jet. The results indicate that a precessing vortex core can exist at relatively low swirl numbers in the gas-liquid two-phase flow. It was established that the liquid greatly affects the precession and the swirl number alone is an insufficient criterion for the development of a precessing vortex core.

Study of gas–liquid jet boundaries in a gas–solid fluidized bed

The boundaries of gas–liquid jets formed during the air-assisted injection of liquids into gas–solid fluidized beds have been investigated using a small and a commercial scale fluidized bed and several injection nozzles. Two independent techniques (a triboelectric probe system and a thermal tracer method) have successfully allowed the characterization of the jet angle, of the jet penetration, and of the overall mapping of the jet cavity. The study demonstrated the effects of the nozzle geometrical configuration, of the air-to-liquid mass ratio fed through the nozzles, and of the scale of the fluidized bed on the jet boundaries. Finally, the experimental results obtained in this work confirmed the accuracy of an empirical correlation for jet penetration available in the literature.

Effect of a draft tube on gas–liquid jet boundaries in a gas–solid fluidized bed

Liquids are injected into fluidized beds in a variety of industrial processes. Installing a draft tube downstream of the nozzle works to optimize the jet–bed interactions so that the liquid feed is more evenly dispersed amongst the bed solids. Triboelectric probes were used to confirm the location of the “mixing zone” inside the draft tube, and also to study the effects a draft tube had on the upstream and downstream jet boundaries. Its publication shows how the presence of a draft tube affects the expansion angle and the penetration depth of a gas–liquid jet in a fluidized bed.

The study on the relationship between breakup modes and gas-liquid interfaces

Based on the linear instability analysis, the study on the relationship between breakup modes and gas-liquid interfaces of a viscous annular liquid jet moving in two swirling gas streams has been carried out. From the numerical results of the dispersion equation, the relevancy of the breakup mode between an annular liquid jet and two liquid jets of limiting cases, namely the cylindrical liquid jet and hollow gas jet, as well as the effects of injecting factors on the instability of an annular liquid jet, is studied in detail. Considering the effects of inner and outer interface radii on the instability of the jet, it is proved that the para-sinuous mode mainly relates to the inner interface, whereas the para-varicose mode mainly relates to the outer interface. The results also indicate that all the forces produced by liquid jet have similar impacts on either the instability of para-sinuous mode or para-varicose mode due to the fact that they can affect both inner and outer gas-liquid interfaces. On the other hand, all the forces exerting only on the inner interface have more powerful effects on the instability of para-sinuous mode, and all the forces exerting only on the outer interface have more powerful effects on the instability of para-varicose mode. That is to say, the effects of forces are weakened greatly when penetrating the liquid jet.

Numerical simulation of gas-liquid two-phase jet flow in air-bubble generator

Air-bubble generator is the key part of the self-inspiration type swirl flotation machines, whose flow field structure has a great effect on flotation. The multiphase volume of fluid (VOF), standard k-ɛ turbulent model and the SIMPLE method were chosen to simulate the present model; the first order upwind difference scheme was utilized to perform a discrete solution for momentum equation. The distributing law of the velocity, pressure, turbulent kinetic energy of every section along the flow direction of air-bubble generator was analyzed. The results indicate that the bubbles are heavily broken up in the middle cross section of throat sect and the entrance of diffuser sect along the flow direction, and the turbulent kinetic energy of diffuser sect is larger than the entrance of throat sect and mixing chamber.

Gas Holdup Distribution of Gas Bubble Dispersed Phase in Gas-Liquid Two-Phase Jet Absorber

Gas holdup distribution in a gas bubble dispersed phase generated by an impinging gas–liquid two-phase jet was measured with an optical fiber void probe. The effects of structural factors of nozzle and column diameter on gas holdup distribution were investigated.The effects of structural factors of nozzle and column diameter on gas holdup distribution were similar to the column average gas holdup. Measured values of the probe were validated by a comparison with column average gas holdup. As a result, it was found that gas holdup distribution in the jet absorber was given by the sum of the gas holdup distributions of descending bubbles and ascending bubbles.

Effect of nozzle diameter and its orientation on the flow pattern and plume dimensions in gas–liquid jet reactors

Gas–liquid jet reactors are widely used in chemical industries in various applications such as feed-water heaters, metal processing, and thermal energy sources, etc. In all these applications, the principal requirement for the design is a prior knowledge of jet shape and dimensions, which primarily depend upon the nozzle type, size, submergence and its orientation. In the present study, CFD simulations of non-reacting (steam-water) and reacting ( SF 6 -Li) jets have been carried out to understand the variation in plume dimensions of gas–liquid jet reactors. For condensation jet and reaction jet, the criteria have been developed to identify the plume boundary based on the hold-up profile of steam/ SF 6 gas and the evaporated fuel. The effect of nozzle diameter and its orientation, nozzle gas velocity and bath temperature on the plume dimensions have been studied for both the types of jets. It was observed that the extent of increase in the plume length is always higher in the case of reaction jet as compared to the condensation jet for all the cases. The analyses also proved that, the availability of reactant is much better with the horizontal orientation which leads to stable plume length. The CFD model has been extended for the prediction of the flow pattern and its effect on the rate of condensation/reaction and plume dimensions for both the jet systems.

Solids entrainment into gas, liquid, and gas–liquid spray jets in fluidized beds

The injection of liquid into a fluidized bed is a crucial step in many processes such as fluid coking, fluid catalytic cracking, or gas-phase polymerization, whose performance greatly depends on good and rapid contact between the injected liquid and the fluidized particles. The liquid spray, created by two-phase (gas–liquid) nozzles, forms a jet, i.e. a gas-rich cavity within the fluidized bed. Past studies have shown that good liquid–solid contact requires a large entrainment rate of particles into the jet, followed by intensive mixing of liquid droplets and entrained particles within the jet. The objective of this study is the experimental measurement of solids entrainment into spray jets. The specific application of interest is the enhancement of solids entrainment under conditions relevant to the fluid coking process. A novel and accurate experimental technique has been developed to measure the solids entrainment from a fluidized bed into two-phase gas–liquid jets, gas jets and liquid jets. The effects of operating conditions of the nozzle (sonic versus subsonic) and of the fluidized bed on the solids entrainment have been investigated. The differences between the mechanisms of solids entrainment for two-phase gas–liquid, gas and liquid jets have been analyzed. This experimental tool has been applied to the design and testing of a mixing chamber consisting of a cylindrical tube placed at a certain distance downstream of the nozzle tip, resulting in a confined, turbulent jet with enhanced liquid–solid mixing properties.

Effect of injection-nozzle operating parameters on the interaction between a gas–liquid jet and a gas–solid fluidized bed

The objective of the present study was to provide insight into the effect of operating conditions on the performance of gas-assisted nozzles injecting liquid into gas–solid fluidized beds. Acquisition of such knowledge is relevant to many industrial applications where liquid injections into fluidized beds of solid particles are performed via spray nozzles. In the fluid coking process, for example, product yields and reactor operability strongly benefit from a rapid and uniform distribution of the liquid feed on fluidized solid particles, which, in turn, is greatly affected by the performance of the liquid-injection system used. A novel experimental technique was employed to investigate the effect of varying the air-to-liquid ratio (ALR), the liquid mass flow rate, and the nozzle size on the contact efficiency of injected liquid on fluidized bed particles. Increasing the ALR or the liquid flow rate increased the nozzle spraying efficiency. On the contrary, increasing the nozzle size while keeping the gas and the liquid flow rates constant, and hence decreasing the pressure at the nozzle tip, lowered the liquid–solid contact efficiency. The effect of increasing the ALR on the liquid–solid contact resulting from nozzle-injections into the fluid bed, was correlated to both the nozzle atomization performance, as determined by open-air tests using a laser-photocell equipment, and the solids entrainment into the gas–liquid jet, as predicted by a model.

Submerged Gas Jet into a Liquid Bath: A Review

Gas-liquid jet reactors are widely used in commercial applications such as condensing jets for direct contact feedwater heaters and steam jet pumps, because of their efficient heat- and mass-transfer characteristics. These are also used for the blowdown of primary nuclear boiler systems into a water bath, without releasing fissionable materials into the atmosphere. Reacting jets are of major interest in metal processing and thermal energy sources that involve submerged injection of an oxidizer into a liquid metal bath. The design of gas-liquid jet reactors is strongly dependent on the plume dimensions and the flow pattern in the liquid phase. In the present review paper, a critical analysis of the published literature on the fluid dynamics and heat transfer for gas-liquid jet reactors has been performed. The analysis has been extended for the empirical, semiempirical, and analytical attempts for the correlations of experimental observations. The published works on the computational fluid dynamics (CFD) simulations have also been critically analyzed. A comprehensive discussion has been presented and an attempt has been made to arrive at a coherent theme that clearly describes the present status of the published literature. Furthermore, recommendations have been made that are expected to be useful for the design engineers as well as researchers, to improve the reliability in the design of this important class of reactors.

1114 ベンチュリ管を用いた気液二相噴流の構造と気泡の微細化に関する一考察(1)(OS11-3 ナノ・マイクロフルイディクス(マイクロ混相流),OS11 ナノ・マイクロフルイディクス,オーガナイズドセッション)

1114 ベンチュリ管を用いた気液二相噴流の構造と気泡の微細化に関する一考察(1)(OS11-3 ナノ・マイクロフルイディクス(マイクロ混相流),OS11 ナノ・マイクロフルイディクス,オーガナイズドセッション)

1114 ベンチュリ管を用いた気液二相噴流の構造と気泡の微細化に関する一考察(2)(OS11-3 ナノ・マイクロフルイディクス(マイクロ混相流),OS11 ナノ・マイクロフルイディクス,オーガナイズドセッション)

1114 ベンチュリ管を用いた気液二相噴流の構造と気泡の微細化に関する一考察(2)(OS11-3 ナノ・マイクロフルイディクス(マイクロ混相流),OS11 ナノ・マイクロフルイディクス,オーガナイズドセッション)

A Modified Correlation to Evaluate Liquid Mass Transfer Coefficient in an Impinging-Jet Tall Bubble Column

An impinging-jet bubble column has been installed in Al- Mansoor Co.-Baghdad for measurements of the ozone mass transfer applications in water treatment Two injectors were used to produce turbulent gas-liquid jets in the working fluid by placing them at an intersecting angle of 1200 . The impact of the two jets increased the gas-liquid mass transfer rates. Experiments are conducted at different ranges of Reynolds number for gas and liquid such that 12.8<ReG< 78 and 804.24<ReL<2928. A correlation to predict volumetric liquid mass transfer coefficient is developed based on CSTRM applied on each section of the tall bubble column. Using the minimization technique, the following correlation was obtained: kLa=21.09uG1.14uL0.078.

気液二相旋回噴流下での均一混合時間とオゾンを用いた汚泥処理技術

気液二相旋回噴流下での均一混合時間とオゾンを用いた汚泥処理技術

Horizontal Penetration of Gas-Liquid Spray Jets in Gas-Solid Fluidized Beds

A new method has been developed to predict the horizontal jet penetration of gas-liquid sprays injected into gas-solid fluidized beds. The technique involves combining a theoretical model to predict the momentum flux of two-phase sprays with the Benjelloun et al. (1995) correlation for gas jets. Following this treatment, a generalized version of the jet penetration correlation has been developed, which includes the effect of nozzle geometry. The correlation predictions are in very good agreement with the experimental data for a wide range of nozzle geometries, nozzle scales, and jet fluids.

円筒容器内気液二相噴流の旋回現象の発生条件

円筒容器内気液二相噴流の旋回現象の発生条件

気液二相噴流による円筒容器内の旋回現象の特性

気液二相噴流による円筒容器内の旋回現象の特性

Entrainment and Stability of a Horizontal Gas-Liquid Jet in a Fluidized Bed

Fluid coking is a non-catalytic process where heavy hydrocarbon feed, sprayed using jets into a fluidized bed reactor, cracks upon contacting hot coke particles and produces valuable volatile fractions. It is estimated that the Alberta tar sands contain 1.7 trillion barrels of oil, equivalent to 35% of the world’s crude oil reserves, of which the majority is processed using fluid cokers. Important parameters that affect the yield of fluid cokers include the feed jet stability and therefore its ability to entrain and mix the injected feedstock with the fluidized coke particles. To this purpose, this study investigated the effect of the use of various types of draft tubes, placed downstream of the feed jet to enhance mixing, on solids entrainment and jet stability.Specifically, it has been demonstrated with the use of a gas-liquid and gas-only jet that an optimum distance exists between the nozzle and draft tube for entrainment of solids. For both cases, this optimal distance occurs as the jet touches the draft tube wall. However, for a gas-only jet this occurs at a shorter distances due to the increased angle of expansion. The angles of expansion were confirmed using triboelectric probe measurements. It has also been shown that the shape of the inlet to the draft tube will have an effect on the rate of solids entrainment as will the presence of pulsations in the jet.

Digital X-ray Imaging Technique to Study the Horizontal Injection of Gas-Liquid Jets into Fluidized Beds

Gas-liquid jets injected into fluidized beds of particles/catalyst find applications in many industrial processes. The effective distribution and mixing of the feed droplets with the entrained bed particles is vital in improving the process efficiency. The present study utilizes a sophisticated digital X-ray imaging system to study the internal flow structure of jets injected into fluidized beds. The system is equipped with an X-ray image intensifier (XRII) and optical detectors, which convert the transmitted X-ray photons into digital images of up to 60 frames s-1. The imaging technique provides useful information such as the jet expansion angle and the penetration distance. These are functional quantities in optimizing the performance of feed nozzles, and in modeling the jet-fluidized bed interactions.In this work, the horizontal injection of gas, gas-liquid, and liquid jets into fluidized beds is investigated. The results indicate that the jet expansion (half-angle) is considerably reduced for a gas-liquid jet (5-7 degrees) when compared to that of a gas jet (10-15 degrees). The gas-liquid jet also appears to penetrate more than a gas jet with the same momentum. When a liquid feed is introduced into a fluidized bed of particles, the particles may agglomerate if they are wet-enough to form liquid bridges. Improper feed distribution may be a direct contributor to enhanced agglomeration. In this regard, radio-opaque tracers mixed with the feed liquid are injected to track the formation and the movement of agglomerates. The tracer experiments show that the agglomerates are generated at the end of the jet region, close to its maximum penetration distance. A brief discussion on the modifications required to achieve improved contrast for the acquired images, and the effect of some important X-ray parameters are also included in the present study.