Annular Jet Research Articles

CFD study on the effect of particle properties on the performance of annular jet pump

Abstract The annular jet pump is a type of fluid mechanical pump that operates by exchanging momentum with the fluid. Annular jet pumps possess distinctive advantages in the transportation of solid particles. However, the efficiency of these pumps is significantly impacted by both the physical properties of the particles and their initial concentration, thereby limiting their practical applications. In this paper, by combining other scholars’ designs of annular jet pumps, the effects of different physical densities and different initial concentrations of particles on the flow field, pressure and efficiency of an annular jet pump were analysed based on the RNG k-ε turbulence model and the Mixture multiphase flow model. The efficiency of the annular jet pump decreases with a higher particle bulk density. Specifically, at an initial concentration of 20% and a flow ratio (M) of 0.5, the efficiency of the annular jet pump fluctuates as follows: it changes from 28.736% under single-phase flow conditions to 25.011%, 24.369%, 23.637%, 22.950%, and 21.733% as the density of particulate matter increases. The findings of this study offer valuable theoretical insights for the implementation of annular jet pumps in engineering discharge applications.

Study on the combination of the annular jet pump and static mixer to improve the fluid‐carrying capacity of gas wells

AbstractAiming at the problem that the suction chamber of the gas‐driven jet pump has insufficient mixing of the power gas and the sucked fluid leading to efficiency reduction, this study proposes to effectively combine the static mixer with the annular jet pump and design a new type of annular jet pump and apply it to the gas wells to improve the fluid recovery capacity. Numerical simulations based on the gas–liquid two‐phase flow model are carried out for a conventional annular jet pump (CAJP) and a new annular jet pump (NAJP). The reliability of the simulation results is verified by gas–liquid two‐phase flow experiments, and the differences between the two in terms of velocity, pressure loss, and turbulent kinetic energy are analyzed. Meanwhile, the validity of NAJP is verified, and the effects of different structures such as static mixer torsion angle, suction chamber angle, and area ratio on the performance of NAJP are analyzed. The results show that NAJP enhances the degree of mixing between the sucked fluid and the power gas through the cyclonic effect created by the static mixer compared with CAJP. It results in a 10.6% year‐on‐year increase in the velocity of the sucked fluid, a 3% year‐on‐year increase in the pressure drop, and a 12.2% year‐on‐year increase in efficiency. NAJP can significantly improve the fluid‐carrying performance. With a mixer angle of 210°, a suction chamber angle of 21°, and an area ratio of 1.77, the NAJP achieves an efficiency of 39.7%, which is a year‐on‐year increase of 7.3% compared to the structure under the same conditions before optimization. This study lays a foundation for the determination of the optimal design scheme of the annular jet pump and at the same time can provide theoretical and technical support for researchers in related fields.

Instability of viscous annular liquid film jet under high air-to-fluid velocity rate

Based on the surface wave dispersion relation equation of viscous annular liquid film jet established by the research group in the early stage, a dispersion relation equation calculation program is written according to Mathematica. A linear stability analysis is carried out for the high air-fluid velocity ratio viscous annular liquid film jet entering a compressible gas medium environment. The relationship between the surface wave growth rate of an annular liquid film jet and the surface wave number under different characteristic parameters is obtained. The connection based on the dominant wave’s growth rate or the dominant wave’s number with dimensionless parameters such as air-fluid velocity rate, air-fluid density rate, Weber number of liquid, liquid Reynolds number, and gas Mach number was analyzed. The consequences reveal that under the high air-fluid velocity ratio, the increase of the above dimensionless parameters promotes the fragmentation course of the annular liquid film jet. Moreover, the augment of the air-fluid velocity rate has the greatest influence on the stability of the viscous annular liquid film jet. In contrast, the Reynolds number of the liquid has less influence than the reliability of the annular liquid film jet. Linear stability analysis under this condition lays the foundation for the prediction model of the most unstable parameters of annular liquid film jet in practical engineering applications.

Breakup behaviors of annular liquid jet from twin-fluid atomizers in crossflow

Breakup behaviors of annular liquid jet from twin-fluid atomizers in crossflow

Annular swirling jet reactor for converting hydrocarbons to olefins and aromatics

This paper describes a novel reactor for high temperature thermochemical conversion of ethane to olefins. The central feature is an efficient flow pattern with a large recirculation zone that provides stable and compact 2500 °C flame and a thin conical annular swirling jet that provides fast transfer of mass, momentum, and heat. The jet is directed through a unique converging–diverging nozzle that maintains relatively low wall temperature and consequently reduces the need for external cooling. The hydrocarbons stream is introduced tangentially through volutes in such a way that there is initially heat transfer with minimal mass transfer followed by fast mixing of countercurrent streams. CFD simulations with detailed kinetics were employed to design and optimize this reactor including the order of the volutes to feed ethane, H2 fuel, oxidizer (O2 and N2 mix), and a cooling N2 gas; oxygen enrichment of the air, and also the overall operating conditions of this flexible and robust reactor. This highly intensified reactor was fabricated and tested at a semi-pilot scale with up to 15 kg/hr feed. The optimized reactor has high selectivity to ethylene and acetylene comparable to conventional steam cracker.

Swirling instability of coaxial liquid jet in gas surroundings

Linear instability analysis of an inviscid coaxial swirling jet is carried out by deriving an analytical dispersion relation of perturbation growth. The azimuthal Rankine vortex and the axial discontinuous velocity distribution are utilized as the jet basic flow. Due to the existence of double interfaces, the instability mechanisms of the coaxial swirling jet are much more complex than those of the single-layered swirling jet. The effects of control parameters (including the swirling ratio, the Weber number, the jet radius ratio, the velocity ratios between different fluids, and the azimuthal velocity jump at the inner interface) on the temporal instability of coaxial swirling jet with different azimuthal modes are studied. By comparing the growth rate of different azimuthal modes, the predominant mode that determines the jet breakup is identified. The results indicate that an increase in the swirling ratio, the Weber number, and the radius ratio can lead to predominant mode transition to larger azimuthal wavenumbers. The velocity ratio between the inner jet and the annular jet and that between the surrounding fluid and the annular jet mainly affect the axial Kelvin–Helmholtz (KH) instability. An enhancement of the KH instability leads to the jet breakup with smaller azimuthal wavenumbers. The azimuthal velocity jump affects the azimuthal KH instability, the centrifugal instability, and the Coriolis instability simultaneously, thus leading to a multiple influence on modes transition. The phase-diagram of the predominant modes is further given, showing that the relative importance between the centrifugal force and the interfacial tension plays a significant role on the transition of predominant modes.

Cooling performance of the hot-rolled seamless steel tube with different jet forms

The jet form is closely related to the cooling strength and uniformity of steel tubes, which is the first consideration in the design of quenching equipment. A reasonable choice of jet form will improve product quality and reduce production costs. In this study, the heat transfer behavior of different jet forms is discussed. Two jet forms are considered: planar jet and annular jet. Besides, the size of the steel tube is also an important variable in this simulation. The remaining parameters are fixed values. The axial and circumferential temperature distributions of the steel tube were obtained. The results showed that the annular jet has better performance on cooling intensity and cooling uniformity. The cooling performance of the two jet forms are almost the same when the steel tube size is smaller than 50 mm. As the planar jet quenching equipment is simple to manufacture, low in cost, and convenient in site application, so the planar jet can be considered when the diameter is small.

Study on improving liquid carrying performance of annular jet pump gas well with static mixer

AbstractIn the process of natural gas extraction, the phenomenon of liquid loading will affect the efficiency of gas well extraction and reduce the life of the well. Compared with conventional drainage gas extraction technology, the jet pump can not only reduce the bottom back pressure and ensure the stable production of gas reservoirs but also promote the final recovery rate. Since the jet pump relies on the interaction between fluid particles to transfer energy, the energy loss is large and the efficiency is low. To maximize the advantages of the gas‐driven jet pump, this study innovatively combines a static mixer with an annular jet pump. Utilizing the cyclonic effect produced by the static mixer, the original gas‐liquid axial motion is transformed into a stronger vortex motion, and the liquid droplets are changed into a liquid film that is easier to carry, which significantly improves the discharge efficiency of the jet pump. This study uses a combination of numerical simulation and experimental analysis to compare the associated effects of the new annular jet pump (NAJP) and the conventional annular jet pump (CAJP) on the liquid‐carrying performance of gas wells in terms of cyclonic effect, droplet breakage ratio, and pump efficiency. The results show that, compared with CAJP, NAJP increases the mass flow rate of the sucked fluid. The droplet breakage ratio increases by 15.4% year‐on‐year, while the critical liquid‐carrying flow rate is reduced by about 10.7%, resulting in a maximum pumping efficiency of 37%, an increase of about 30.7% year‐on‐year. At the same time, the reduction of the energy coefficient means lower energy consumption. In summary, NAJP is better than CAJP in terms of liquid‐carrying effect and efficiency.

Effects of different working parameters on the turbulent drag reduction regulated by annular plasma synthetic jet actuators

Reduction of turbulent drag force is one of important works in the design of airplanes and hypersonic aircrafts. The annular plasma synthetic jet (APSJ) has become an interesting and popular flow control method in reducing the drag of turbulent boundary layers. In this paper, a comprehensive experimental study is carried out on the turbulent drag reduction regulated by an array of annular plasma synthetic jet actuators. The effects of the operating parameters such as the actuation voltage, the pulse frequency and the incoming wind speed on the drag reduction rate are studied and discussed in detail. The performances of the plasma actuator array are evaluated and summarized at multiple working conditions. Finally, the coherent structures of turbulence and the hairpin-like vortices are depicted and discussed. The results show that the optimal drag reduction rate is achieved, as the actuation voltage, pulse frequency and incoming wind speed are Vpp = 7 kV, fp= 50 Hz, and U∞ = 7 m/s, respectively. A resonant coupling phenomenon is observed when the pulse frequency of the actuators approaches the characteristic frequency of the coherent structure. The upward sweep flow induced by APSJ actuators may lead to a reduction of the turbulent drag force, but the downward wash flow leads to an increase in the drag. Present study could provide solid experimental data and a helpful guidance for the drag reduction of an airplane.

Application of multi-extruded fuel injectors for mixing enhancement of hydrogen gas at scramjet engine: computational study.

Scramjet engines are considered a highly promising technology for improving high-speed flight. In this study, we investigate the effects of using multi-extruded nozzles on fuel mixing and distribution inside the combustion chamber at supersonic flow. Additionally, we explore the impact of an inner air jet on fuel mixing in annular nozzles. To model fuel penetration in the combustor, we employ a computational technique. Our study compares the roles of three different extruded injectors on fuel diffusion and distribution at supersonic cross-flow. Our findings reveal that the use of an inner air jet increases fuel mixing in the annular jet, while the use of extruded nozzles improves fuel distribution by enhancing the vortices between injectors. These results demonstrate the potential benefits of incorporating multi-extruded nozzles and inner air jets in the design of scramjet engines.

Numerical Prediction of a Turbulent Flow with Double Annular Jets for Different Reynolds Numbers

Numerical Prediction of a Turbulent Flow with Double Annular Jets for Different Reynolds Numbers

A computational investigation of swirl-number and Damköhler-number effects on non-premixed laminar swirling jet flames

Axisymmetric numerical simulations are used to assess the swirl-induced stabilization of low-Mach-number non-premixed jet flames at a moderate Reynolds number (Re=200). Using a one-step model chemistry describing methane-air partially premixed combustion, we carry out a parametric investigation of the coupling between vortex breakdown and laminar flame liftoff/blowoff in a concentric jet configuration involving a central non-swirling methane jet surrounded by a swirling annular air jet issuing from a pipe with radius RA′ rotating with angular speed Ω′. The analysis considers order-unity values of the two relevant controlling parameters, namely, the Damköhler number DN, defined as the square of the ratio of the stoichiometric methane-air flame-propagation velocity to the mean air-jet velocity UA′, and the swirl number S=Ω′RA′/UA′. As the Damköhler number DN is decreased the attached edge flame lifts off from the injector rim. The resulting lifted triple flame migrates downstream on further decreasing DN until a critical blowoff value DN,b is reached. Results for fixed S=1 exhibit lower values DN,b than the corresponding simulations with fixed S=0. For a fixed Damköhler number, it is found that increasing S results in increased entrainment and reduced liftoff heights. At a critical value SB* of the swirl number, equal to SB*=1.2 for DN=0.35, a recirculation zone abruptly forms upstream of the lifted triple flame, enhancing the mixing and facilitating flame stabilization closer to the injector.

Insights into the intrinsic asymmetry of bluff-body stabilised swirling and non-swirling annular flows

Bluff-body stabilised annular jets possess simple, well-defined, axisymmetric geometry, yet exhibit highly complex flow fields, are susceptible to asymmetry at larger blockage ratios, and embody both complex zones and shear layers. Practical annular combustors feature swirl and a central jet which further complicates the flows. Despite the importance of asymmetry in practical combustor design, a systematic investigation for the role of flow regime (transitional, turbulent), Reynolds number, swirl number, or central jets on asymmetry remains lacking. In this study, two-dimensional time-averaged planar particle image velocimetry measurements are conducted to resolve the intrinsic asymmetry associated in transitional (Res = 2700) and turbulent (Res = 17,800 and 35,500) bluff-body stabilised confined annular jets. Experiments are conducted on non-swirling (S = 0) and swirling annular jets (with S = 0.3), both operating independently and with the addition of a turbulent central jet (Res = 10,400). Constant temperature anemometry measurements resolve boundary conditions at the exit of annulus and an Asymmetry Index is presented.Results show that swirl significantly mitigates asymmetric vortex shedding and restores annular jet symmetry. Quantification (at x/D = 1, r/D = 0.5) reveals that turbulent swirling annular jets demonstrates a 42 % (for Res = 17,800) and 78.6 % (for Res = 35,500) reduction in asymmetry compared to non-swirling annular jets. Whereas, swirling annular jets under transitional flow regime show a negligible impact on the flow asymmetry. In addition to this, increasing the Reynolds number from Res = 2,700 to 17,800 results in a 36.2 % and 58.7 % decrease in the asymmetry for non-swirling and swirling annular jets, respectively. A further increase to Res = 35,500 brings an additional 68.6 % decrease in the asymmetry for swirling annular jets, showing that swirl in combination with high turbulence restores and maintains symmetry in bluff-body stabilised annular jets. Moreover, at medium turbulence (Res = 17,800), the non-swirling annular jet with a superimposed turbulent jet exhibits a nearly axisymmetric flow behaviour compared to stand-alone non-swirling annular jet.

A Combined Delayed Detached Eddy Simulation and Linearized Navier–Stokes Equation Study on the Generation and Reduction of Aerodynamic Noises Inside Steam Turbine Control Valve With Acoustic Liner

Abstract This study was aimed at numerically investigating the source, generation mechanism, and strategy for reducing aerodynamic noises inside a steam turbine control valve. A delayed detached eddy simulation was performed to extract the three-dimensional unsteady turbulent flow structures formed within the serpentine flow passage of the turbine valve. Acoustic analogies, spatial Fourier transform, and spectral proper orthogonal decomposition on the delayed detached eddy simulation-simulated flow data were complementarily combined to clarify the generation mechanism of tonal and broadband aerodynamic noises. The results showed that broadband noises were produced by wall-attached jet flow and turbulent mixing flow between the annular wall jets and central reverse flow. High-intensity tonal noises were generated by the excitation of multi-order natural acoustic modes of the bell-shaped valve spindle. The intensive acoustic pressure pulsations concentrated inside the bell jar and propagated along the diffuser to the downstream turbine chamber. A novel ring acoustic liner was designed using the acoustic impedance model to reduce the valve noises without sacrificing the flow performance. The noise reduction effectiveness was evaluated by solving the linearized Navier–Stokes equations in the frequency domain.

Comparative molecular dynamics study of liquid hydrogen annular jets in subcritical and supercritical environments

In this paper, the injection characteristics of a liquid hydrogen propellant jet under subcritical and supercritical operating conditions are comparatively studied at the molecular scale using molecular dynamics methods in the context of spacecraft propulsion systems. To control the temperature and pressure within the environment and nozzle respectively, two sub-computational domains are set up for separate modeling. The sub-computational domain merging process eliminates the broken molecular bonds by using the computational domain reduction in the x-direction. The jet velocity, density and other physical property distributions at different temperatures and pressures were comparatively studied. It is found that the rate of change of the radial density of the jet under supercritical conditions is small. Based on this, the surface area and volume of the liquid phase region of the jet were extracted and calculated. Compared to result of subcritical case, the volume of the liquid hydrogen jet in the supercritical environment is reduced by 1.9%, while the surface area is increase by 6.7%. To explain the variation in the surface area due to molecular diffusion, the molecular stress results revealed that the stress in the hydrogen jet in supercritical environment is only 88.9% of that in subcritical environment.

Numerical and experimental investigations on the jet and shock wave dynamics during the cavitation bubble collapsing near spherical particles based on OpenFOAM

The interaction between cavitation bubbles and particles is essential for the operational performance many kinds of fluid machineries. In the present paper, jet dynamics and shock waves induced by the cavitation bubble collapsing near two spherical particles are numerically investigated based on OpenFOAM. The numerical scheme is validated by the experimental data obtained based on our high-speed camera cavitation system. Our results reveal that bubble split induced by annular jet is the primary feature during bubble collapsing with four typical cases defined. For the jet formation, the localized high pressure produced at the bubble split point is the main reason and the split point also serves as the source of the shock waves shown by the numerical schlieren. Furthermore, the nondimensional bubble-particle distance is the most paramount parameter influencing the jet phenomenon (e.g. jet velocity).

A Numerical Study of Flow Structures and Flame Shape Transition in Swirl-Stabilized Turbulent Premixed Flames Subject to Local Extinction

ABSTRACT Large Eddy Simulations (LES) of turbulent lean-premixed flames of V- and M-shape are presented. A simple algebraic closure with the ability to capture finite-rate chemistry effects is used for subgrid reaction rate modeling. The V-shaped flame is stabilized in the inner shear layer between a swirling annular jet and a central recirculating bubble in a sudden expansion duct. The M-shaped flame is stabilized in the inner and outer shear layer, adjoining the corner recirculation zone induced by the vertical step. The focus of the study is on the flow fields and shapes of the flames, which distinguish themselves through different heat load and sensitivity to local extinction. Good agreement with measurements is observed for the cold and the reacting flow cases. The numerical results suggest that the entrainment of hot gases into the outer recirculation zone occurs close to the impingement point of the swirling annular jet on the wall and this process is strongly dependent on intense vortical structures in the outer shear layer. The results further suggest that local extinction influences the position of the flame in the inner shear layer and, thereby, also the intensity of the local entrainment process.

Flow Development of Multi-Annular Jets in a Confinement: Effect of Expansion Ratio

Confined coaxial jets have been widely used in gas turbine combustors, where the requirement is to achieve better mixing between two streams - fuel and air - prior to ignition so as to provide stable and complete combustion. Two shear layers, one between the central jet and the annular jet and other between the annular jet and the stagnant fluid outside the annular jet help in the mixing process for confined coaxial jets. Therefore, for improved mixing, a configuration of one central jet and two co-annular jets, called multi-annular or multicoaxial jets, has been considered. To understand mixing of these streams in a confinement (mixing chamber), the mean axial velocity profiles at different axial locations of the mixing chamber and the static pressure along the wall of the mixing chamber are measured for expansion ratio of 1 and 1.3. These quantities are also computed using CFD software, FLUENT, with Standard k-ε turbulence model. After validation of the CFD code, parametric studies have been carried out for different expansion ratios. The results provide a good understanding of the mixing process and flow development in expanding confinement.

Numerical investigation on the interaction of an oscillating bubble with the interface of a non-Newtonian fluid

The dynamics of an oscillating bubble near a liquid–liquid interface is a complex multiphase flow problem due to the highly nonlinear interaction, such as interface fragmentation and bubble tearing. When one of the liquid mediums is non-Newtonian, its constitution would significantly influence both the bubble motion and the interface evolution. In this study, a numerical model is established based on the Eulerian finite element method with the non-Newtonian fluid described by the Herschel–Bulkley model. The numerical model is validated by comparing with experimental results for a non-spherical pulsating bubble at a water–oil interface and the analytical solution for the laminar flow of non-Newtonian fluids in a circular tube. According to the simulation and analysis with different case parameters, our findings suggest that the non-Newtonian fluid forms a crater when squeezed by the bubble, and the downward jet can penetrate the bubble and further deepen the crater. As the distance parameter increases, the crater gradually disappears or even bulges. Furthermore, the yield shear stress can give non-Newtonian fluid plastic properties similar to a solid, effectively reducing the bubble's pulsation and jet load. Additionally, the flow behavior index n comes from the power-law model for non-Newtonian fluids and significantly impacts the jet's impact process. When n≤1, the crater is likelier to become funnel-shaped, whereas when n > 1, it is likelier to become bullet-head-shaped. In addition to enhancing the bubble's nonsphericity, the reduction in Reynolds number also weakens the crimp deformation of the interface. When the distance parameter is zero, the larger the buoyancy parameter and the less deformable the non-Newtonian fluid, the easier the bubble to split by the annular jet.

Breakup mode of continuous-type liquid-liquid pintle injector

A pintle injector is necessary for the reuse of a launch vehicle. Significant studies have been conducted on the breakup process in impinging or swirl type injectors. However, the breakup process in liquid-liquid pintle injectors from injection to the atomization of liquid films has rarely been investigated. Therefore, in this study, the breakup mode and process quantified characteristics of the pintle injector were investigated. The backlight imaging technique was applied to capture the spontaneous phenomenon, and a longitudinal section view of the spray on the pintle injector was obtained using the 2P-SLIPI technique. The breakup modes were classified into three categories based on the spray shape (hollow cone, fishbone, and branch). The atomization process was investigated with high-speed and SLIPI images in chronologicalorder. Schematics of the process were also prepared to understand the breakup mechanism. The dynamic characteristics, such as breakup frequency and peak amplitude, and static characteristic (breakup length) were investigated using the flow Weber number. Furthermore, the dynamic characteristics are dependent on the radial flow, and the static characteristics are influenced by the annular jet flow. This study will serve as a reference for the breakup mechanism and characteristics of a liquid-liquid pintle injector design.