Outer Nozzle Research Articles

The Effect of Heterogeneous Natural Gas–Hydrogen Input Into F-Class Gas Turbine Combustor As a Combustion Optimization Method

Abstract The global push to combat climate change by transitioning to clean power generation is accelerating. One promising avenue involves using hydrogen in place of natural gas in gas turbine-based power plants. While the development of new hydrogen combustors shows potential, advancements in operational technologies are needed to ensure higher hydrogen cofiring with existing combustion systems. In our study, we propose a novel approach called heterogeneous natural gas–hydrogen input: varying hydrogen content between different nozzle groups in gas turbine combustors. Using a full-scale combustor of an F-class gas turbine model, we experimentally investigated the impact of heterogeneous hydrogen concentrations at the center and outer nozzles on combustion dynamics and emissions, comparing these with homogeneous fuel supply cases of 100% natural gas and natural gas–hydrogen mixtures. While hydrogen cofiring did not change the maximum amplitude of combustion dynamic pressure across the total frequency range, peak amplitudes in the 125–245 Hz domain were linearly proportional to the hydrogen cofiring ratio, with a 41.2% increase at 30% cofiring identified as a possible limiting factor. Our findings revealed a significant correlation between NOx emissions and combustion stability under varying levels of heterogeneity. Higher heterogeneity with intensive hydrogen input into the center nozzle improved cofiring performance, reducing the peak amplitude in the limiting frequency domain by 22% for a 25% cofiring ratio, potentially extending the critical hydrogen cofiring ratio. Implementing heterogeneous natural gas-hydrogen inputs emerges as a promising method to enhance combustion stability and enable effective hydrogen cofiring.

Effects of Coaxial Nozzle's Inner Nozzle Diameter on Filament Strength and Gelation in Extrusion-Based 3D Printing with In Situ Ionic Crosslinking.

This study systematically investigates the effects of the coaxial nozzle's inner nozzle diameter on the strength and gelation of filaments produced via extrusion-based 3D printing with in situ ionic crosslinking. In this system, bioink (sodium alginate solution) was extruded through the outer nozzle, and the ionic crosslinking solution (calcium chloride solution) was extruded through the inner nozzle. The outer nozzle diameter was fixed at 2.16 mm, and the inner nozzle diameter was varied among 1.19, 0.84, and 0.584 mm. The results indicate that, as the inner nozzle diameter decreased, filament strength decreased, and filament gelation became poorer. These findings highlight the importance of optimizing inner nozzle diameter for improved filament strength and gelation in extrusion-based 3D printing with in situ ionic crosslinking.

Suppression of Combustion Oscillations in Hydrogen-Enriched Can-Type Combustors Through Fuel Staging

Abstract To achieve decarbonization in power-generating gas turbines, the technology of mixing hydrogen with natural gas is garnering significant attention. However, when blending natural gas with hydrogen, the altered combustion characteristics can lead to combustion instability in gas turbine combustors. Although fuel staging can effectively suppress combustion instability for can-type combustors, further research on mitigation strategies for hydrogen cofiring and their predictive methods is required. This study involves hydrogen cofiring experiments using a full-scale can-type combustor. Moreover, the resulting suppression of combustion instability is analyzed through fuel staging by utilizing three-dimensional (3D) computational fluid dynamics (CFD) and one-dimensional (1D) thermo-acoustic analysis. The experiments used a full-scale industrial can-type combustor with a five-around-one nozzle configuration. Hydrogen was blended with natural gas up to a volume fraction of 30%, maintaining a constant thermal power. Fuel staging was applied by controlling two out of five outer nozzles (ONs) along with the remaining three. Before the 1D thermo-acoustic analysis, the internal flame structure of the combustor was examined through 3D CFD analysis. Based on the results, a multi-input multi-output (MIMO) system was constructed for 1D thermo-acoustic analysis of the can-type combustor. The application of time delays derived from 3D CFD analysis to the 1D model revealed that differences in flame time delays across the nozzles cause combustion instability suppression observed in fuel staging.

Co-flow jets application for occupant targeted ventilation: Focus on thermal comfort and air quality

Co-flow air jets can be used in occupant-targeted ventilation, such as personalized ventilation, stratum ventilation, aiming at improving air quality in the breathing zone of occupants. However, these have not been studied sufficiently. The velocity field and cleanness of co-flow jets comprising inner jet of clean air encircled by outer jet of room air were studied under isothermal conditions by physical measurements and CFD simulations at numerous combinations of initial diameter and velocity of the inner and outer jets appropriate for practical application. The co-flow jet had a lower axial velocity decay along the jet direction than that of the single jet. The magnitude (turbulence intensity) and frequency of the velocity fluctuations in co-flow jets were lower compared to those in a single jet. The results revealed that with regard to thermal comfort co-flow jets may provide more cooling compared to single jets, especially when supplied toward to the user. The level of cleanness depended on the initial velocity of the inner and outer jets as well as their diameters. The air on the jet axis of the co-flow was up to 40 % cleaner compared to the single jet. The increased area ratio of outer nozzle to inner nozzle from 1.0 to 3.0 improved the cleanness of the air by at least 10 % to the distance from 8 to 14 initial diameters compared to a single jet. The co-flow jet with velocity ratio of 1.5 had longest concentration core length, Lu, (up to 6 initial diameters to the inner jet) with clean air. The results can be used for design of occupant targeted ventilation.

Microstructure and topography of laterally confined porous anodic oxides produced with high growth rate in a maskless two-phase jet setup

AbstractMaskless anodic oxidation with a continuous free jet of electrolyte can be used for the local surface functionalization and structuring of aluminum materials. In this study, a two-phase jet was applied with the aim of enhanced lateral confinement of the anodic oxide on the aluminum alloy EN AW-7075. The two-phase jet was realized by a coaxial arrangement. While the inner electrolyte nozzle with a diameter of 100 µm acted as the cathode and was used to provide the electrolyte with a flow rate of 10 ml min−1 resulting in an average jet velocity of approximately 21 m s−1, the outer nozzle with a diameter of 3000 µm was used to provide deionized water with a flow rate of 383 ml min−1 resulting in an average water jet velocity of 1 m s−1, which is sufficient to realize a continuous free two-phase jet. Process voltages from 10 to 60 V were investigated. The realized oxide layers were characterized by non-destructive as well as destructive methods to determine their microstructure and their thicknesses. Optically transparent anodic oxide layers were achieved in the voltage range between 10 and 25 V. Maximum total layer thicknesses between 1.1 µm and 16.9 µm were measured in these cases. Thicknesses of more than 50 µm were determined for higher voltages up to 60 V; however, burning effects and stronger discolorations were determined for voltages ranging from 30 to 60 V. Consequently, 25 V was derived as best suitable voltage for two-phase anodizing with high growth rate leading to oxide layers with low defects. Graphical abstract

Effect of Inlet Pressure on the Polyurethane Spray Nozzle for Soil Cracking Improvement: Simulations using CFD Method

Rigid spray polyurethane (RSPU) was commercially used as an injection in crack walls or soil surfaces to enhance material performance, increase lifetime, and save operating costs. The limitation of the RSPU nozzle was reported as easily clogging when sprayed out to the insulation and crack surface area and the finished product was less aesthetically pleasing. In this study, the RSPU nozzle of flat fan nozzle, 180° angle (Design A), Hollow cone nozzle, 60° angle (Design B), and Full cone nozzle, 90° angle (Design C) were prepared by using the SOLIDWORKS software. The effect of different pressures for RSPU nozzle design at the ranges of 4Mpa, 5MPa, and 6MPa was examined by ANSYS FLUENT software. The velocity of the outer spray nozzle shows a significant increase with increasing inlet pressure of the RSPU nozzle. The results reveal that the highest velocity of RSPU was obtained at the Hollow cone nozzle (Design B) as compared to (Flat fan nozzle) Design A and (Full cone nozzle) Design C at 394.249 m/s at 4MPa, 442.327 m/s at 5MPa and 485.37 m/s at 6MPa, respectively. The distribution droplet area shows the Design B spray formation had wider area coverage at 60° and exhibited that the injection nozzle spray was scatted and uniform at 6MPa. RSPU shows the velocity increased, distribution droplet increased, and output volume spray was decreased at the increasing of injection pressure. Hence, in this study was suggested that the size of RSPU nozzle design must be made at the ranges of 60° to 90° of outlet nozzle to obtain a good RSPU area. In conclusion, design B is the most effective for RSPU nozzle and is useful in injection cracking and insulation materials applications.

Numerical Analysis of the Airflow Field and Experiments of Fiber Motion for Solution Blowing.

Solution blowing is a rapidly developing technology for the rapid and large-scale preparation of nanofibers, driven by its advantages, such as wide adaptability to raw materials, simple and safe operation, and ease of scalable production. Most of the research related to solution blowing mainly focuses on the fiber spinning and forming principle, fiber structure and properties, and the development of new materials. Limited studies have focused on the airflow field and fiber motion in solution blowing. In this paper, nine nozzles for solution blowing with varying geometrical parameters were designed by adjusting the outer nozzle diameter, inner nozzle outstretched distance, and inner nozzle diameter. The centerline airflow velocity, turbulence intensity, and velocity distribution of the solution blowing were analyzed using the numerical simulation method. The results showed that the outer nozzle diameter had the greatest influence on the air velocity and turbulence intensity. The airflow velocity increased and the turbulence intensity decreased with the increase of the outer nozzle diameter. The inner nozzle outstretched distance only affected the airflow convergence point and had less effect on the airflow velocity and turbulence intensity. The captured trajectory of the polymer jet initially shows a straight or slightly curved development that eventually diverges from the airflow field. With an increasing distance, dispersed fibers exhibit instability, including loop formation, bonding, and separation. The experimental observation of fiber morphology in the solution-blowing web further verified the instability during the fiber movement.

Applying In Situ Ionic Crosslinking in Bioprinting Using Algae Cells

Abstract Bioprinting using algae cells has many potential applications including tissue engineering, environmental engineering, contaminant removal from water, and establishing space habitats. In extrusion-based bioprinting, bioink needs to be crosslinked after being extruded from the nozzle for printed constructs to first achieve and then maintain adequate shape fidelity. Crosslinking methods used in reported studies on algae-contained bioinks include both photo-crosslinking and ionic crosslinking. This paper reports a preliminary study where the coaxial nozzle-based in situ ionic crosslinking method was used in bioprinting of algae cells without additional crosslinking of printed samples for the first time. In comparison with photo-crosslinking, in situ ionic crosslinking can minimize bioink preparation time and complexity, eliminate cells’ exposure to ultraviolet radiation, and reduce the number of post-printing steps. In this preliminary study, the bioink was an alginate solution containing algae (Chlorella vulgaris) cells, and the crosslinking solution was a calcium chloride solution. The coaxial nozzle had two nozzles: inner and outer nozzles. In printing, the bioink was delivered through the outer nozzle while the crosslinking solution was delivered through the inner nozzle. The shape of the printed samples was a square block with dimensions of 30 × 30 × 10 mm. It was observed that, 9 days after printing, the algae cells grew within the printed samples, and the samples could keep their shapes relatively well. Many knowledge gaps exist regarding the effects of input variables in bioprinting of algae cells using this method. This paper discusses future research directions to fill these knowledge gaps.

Investigation of Fuel and Load Flexibility of an Atmospheric Single Nozzle Jet-Stabilized FLOX® Combustor With Hydrogen/Methane-Air Mixtures

Abstract In this work, an existing single nozzle FLOX® (FLOX®, WS Wärmeprozesstechnik GmbH, Renningen, Germany) burner was modified with a fuel nozzle that was installed concentrically inside the outer air nozzle and was arranged in two different configurations. In the first, nonpremixed case, the fuel and air nozzles were flush at the nozzle exit. In the second, technically premixed case, the fuel nozzle terminated 50 mm below the air nozzle exit. A third, fully premixed case was also achieved by injecting fuel into the air delivery line via an inline-mixer upstream of the nozzle exit. Additionally, measurements were performed using fuel nozzles with two different sizes. For all these cases, hydrogen volume fraction in the fuel was varied from 0 to 100% at a constant equivalence ratio and thermal power. The resulting flames were characterized using two-dimensional OH-chemiluminescence measurements. In addition, load-flexibility was investigated on the 100 vol. % H2 case by varying the equivalence ratio. Some selected conditions were further investigated using particle imaging velocimetry (PIV) to obtain velocity fields. The experimental results demonstrated a strong influence of nozzle configurations (mixedness), equivalence ratio, and H2-content on flame shapes. First of all, increasing H2-content reduced the flame liftoff height (LOH) above the nozzle exit for all three configurations. Second, for the cases with 100 vol. % H2 and independent of the nozzle configuration, the liftoff height increased drastically when Φ was reduced to below 0.3 while the flame became visibly unstable. Overall, increasing level of mixedness generally caused the flame to stabilize closer to the nozzle exit. A remarkable decrease in the liftoff height was observed for the technically premixed case compared to the nonpremixed case. Increasing H2-content from 0 to 100 vol. % also increased the measured NOx emission by nearly a factor of 4, which was also strongly affected by the level of mixedness. Experimental results from this work are being used in a joint effort to validate numerical models for jet-stabilized hydrogen combustion.

Preparation and property of antibacterial filter membrane by coaxial electro‐spraying/electrospinning technology

AbstractHerein, a novel technology named coaxial electro‐spraying/electrospinning was successfully introduced, which can simultaneously prepare nanofibers and nanoparticles. First, the device contains an outer nozzle and an inner nozzle, which combine electrospinning with electro‐spraying technology. Then, the polyamide 6 (PA6) was spun to prepare the nanofibers from the inner nozzle, and the silver nanoparticles (Ag NPs) into the PA6 solution were sprayed to prepare the nanoparticles from the outer nozzle. PA6 nanofibers (NFs)/Ag nanoparticles (NPs) antibacterial composite membranes for the filtration of fine particulate pollutants were successfully prepared using coaxial electro‐spraying/electrospinning. The microstructure, physical properties, and antibacterial properties of the composite membrane were investigated. The results show that Ag NPs are successfully loaded in situ onto PA6 NFs of approximately 100 nm to form a three‐dimensional (3D) structure. The filtration efficiency of the 3D structured filtration membrane reaches 90.98%, compared to only 12.78% for the melt‐blown cloth mask filter material when tested with polystyrene microspheres (PS) of 200 nm. The contact angle of the composite membrane decreased from 145.47° to 44.11°, indicating a significant improvement in the hydrophilicity of the membrane. Furthermore, depositing Ag on the surface fibers resulted in an impressive antibacterial rate of 99.75% against Penicillium.

Effect of Al or Ti addition on the ferrite formation in ultra-low oxygen weld metal of low carbon steel

Effect of Al or Ti addition on the ferrite formation in ultra-low oxygen (about a few tens ppm) weld metal of low carbon steels were investigated. A bead-on-plate welding experiments were performed with a Tungsten Inert Gas (TIG) welding system. The double nozzle was attached to the welding torch used, Ar was passed along the outer nozzle and He is added along the inner nozzle. Optical micrographs showed that primary ferrite appeared along prior austenite grain boundaries and that as the temperature is decreased ferrite side plates were grew into grain interior. Their formation positions were approached to the welding end as the decreasing Al and increasing Ti content. This change in ferrite formation position attributed on the ferrite formation temperature, which was assumed to increase as the decreasing Al and increasing Ti content. Energy dispersive X-ray spectroscopy analysis of inclusions showed that Al and Ti were mainly associated with 0, it was obvious that the inclusions in the steels were Al- and Ti- oxide inclusions. Al-oxide inclusions were not favourable acicular ferrite nucleation sites and the inclusions contributing to acicular ferrite formation were Ti-oxide ones. The number density of acicular ferrite was small. This indicated that acicular ferrite formation was suppressed because the number density of inclusions was low under the ultra-low oxygen welding condition.

Study on jet characteristics of a dual-structure converter oxygen lance based on hydrodynamics

Oxygen lance is the key piece of equipment for iron and steel smelting. During the entire steelmaking process, the performance of the oxygen lance determines the occurrence of decarburization, slagging, heating, and splashing. In this paper, the influence of structural and process parameters on converter steelmaking is studied using a six-nozzle staggered oxygen lance and the traditional six-nozzle oxygen lance by performing jet tests, numerical simulation, and water model experiments. The research results show that, compared with the traditional oxygen lance nozzle, a stepwise fusion of the jet streams of the staggered oxygen lance nozzles occurs, which increases the fusion distance to varying degrees, reduces the amount of splash at the furnace mouth, and increases the effective impact area. For the six-nozzle staggered oxygen lance nozzle, the most ideal structure and maximum performance are obtained at an inner nozzle angle of 14° with a flow ratio of 55% and an outer nozzle angle of 18° with a flow ratio of 45%. The results show that the fusion distance of the inner nozzle and outer nozzle is 2.1 and 2.25 m, respectively; compared to the traditional oxygen lance nozzle, the splash amount of 0.19 g at the furnace mouth is reduced to only 16%, while the effective impact area has doubled to reach a value of 0.47 m2. With the increase in the oxygen lance position, the effective impact area of the jet of the oxygen lance nozzle on the molten pool first increases and then decreases, and the best position of the traditional and staggered oxygen lance nozzles is determined as 30.0 and 35.0–37.5 de, respectively.

On-demand ferrofluid droplet formation with non-linear magnetic permeability in the presence of high non-uniform magnetic fields

The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field achieved by the larger domain for the boundary condition. The Finite volume method and coupling of level-set and Volume of Fluid methods are used for solving equations. The droplet formation is simulated in a two-dimensional axisymmetric domain. The method of solving fluid and magnetic equations is validated using a benchmark. Then, ferrofluid droplet formation is investigated experimentally, and the numerical results showed good agreement with the experimental data. The effect of 12 dimensionless parameters, including the ratio of magnetic, gravitational, and surface tension forces, the ratio of the nozzle and magnetic coil dimensions, and ferrofluid to continuous-phase properties ratios are studied. The results showed that by increasing the magnetic Bond number, gravitational Bond number, Ohnesorge number, dimensionless saturation magnetization, initial magnetic susceptibility of ferrofluid, the generated droplet diameter reduces, whereas the formation frequency increases. The same results were observed when decreasing the ferrite core diameter to outer nozzle diameter, density, and viscosity ratios.

Measurements of the imploding plasma sheath in triple-nozzle gas-puff z pinches

Gas-puff z-pinch implosions are characterized by the formation of a dense annular plasma shell, the sheath, that is driven to the axis by magnetic forces and therefore subject to the magneto-Rayleigh–Taylor instability. Here, the conditions within these sheaths are measured on the 1-MA COBRA generator at Cornell University [Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)] for various gas species and initial fill densities. The gas-puff loads are initialized by a 7 cm diameter triple-nozzle gas valve assembly with concentric outer and inner annular nozzles and a central gas jet. Thomson scattering and laser interferometry provide spatially resolved flow, temperature, and electron density profiles midway through the implosion, while extreme ultraviolet pinhole cameras record the evolution of the plasma column and photoconducting diodes measure x-ray emission. Analysis of the scattering spectra includes a means of discriminating between thermal and non-thermal broadening to test for the presence of hydrodynamic turbulence. Two types of sheath profiles are observed, those with sharp discontinuities at the leading edge and those with smooth gradients. In both cases, non-thermal broadening is generally peaked at the front of the sheath and exhibits a characteristic decay length that roughly scales with the sheath ion mean free path. We demonstrate that this non-thermal broadening term is inconsistent with laminar velocity gradients and is more consistent with dissipative turbulence driven by unstable plasma waves in a collisionless shock. The resulting differences in sheath profile are then set by the sheath ion collisionality in a manner consistent with recent 1D kinetic simulations [Angus et al., Phys. Plasmas 28, 010701 (2021)].

Influence of radial fuel staging on combustion instabilities and exhaust emissions from lean-premixed multi-element hydrogen/methane/air flames

The utilization of hydrogen-blended hydrocarbon fuels, or even completely carbon-free fuels like pure hydrogen and ammonia, will be indispensable in the effort to reduce anthropogenic carbon dioxide emissions from heavy-duty land-based gas turbines. In order to make this energy transition, however, low emissions, low dynamics fuel-flexible gas turbine combustion systems will be required. To address some of the key technological obstacles in the development of such systems, we explore a prototype multi-element injector assembly devised to prevent flashback in extremely fast premixed hydrogen flames, paying particular attention to the impact of radial dual-fuel staging on the generation of self-induced instabilities and the formation of nitrogen oxides and carbon monoxide. In conjunction with phase-averaged OH*/CH* chemiluminescence and OH PLIF flame imaging, we carry out extensive measurements over the full range of 0 to 100% H2/CH4 fuel staging conditions, including even/uneven blends of H2/CH4 fuels between inner and outer nozzle groups, partial/complete fuel split cases, and pure H2 or CH4 fuel for all constituent flames, under a constant thermal power condition of 78 kW. Our measurements demonstrate that whereas carbon monoxide concentrations are largely unaffected by the radial fuel staging conditions except under high and pure hydrogen percentage conditions, there exists a strong correlation between total nitrogen oxides emissions and overall adiabatic flame temperature. Integrated analyses of isocontour instability maps reveal that near XH2,g = 0.50 a discontinuous mode transition takes place, where the intermediate-amplitude lower frequency oscillations associated with relatively low hydrogen concentration conditions give way to stronger, higher frequency instabilities under high hydrogen content conditions. While even-blend (non-staging) conditions are characterized by coherent oscillations of the constituent flames, the responses of clustered flames to radial fuel staging conditions are eccentric and complex, manifested as large-scale asynchronous modulations between inner- and outer-stage heterogeneous reaction zones. This observation suggests that in a multi-element injector environment spatiotemporal incoherence driven by inhomogeneous heat release can be used to neutralize self-excited pressure oscillations, by disrupting pressure-heat release coupling processes.

Characteristics and suppression of vibration in cross-flow turbine with a cavity

Abstract Cross-flow turbine is widely used for small hydropower in run-of-river type stations because of its excellent partial load characteristics, easy manufacturing, and low cost. The Banki-Michell turbine is the origin, and various studies have focused on improving the turbine performance. The authors have developed a new cross-flow turbine with a cavity and a guide wall from the outer nozzle wall tip to suppress flow separation on the guide wall and make the casing smaller. However, little researches are focusing on vibration, and it is also essential to get knowledge for suppressing vibration and noise from the turbine aiming to install at higher head sites. Our previous studies showed that high-pressure fluctuation occurs near the outer nozzle tip, and the cavity suppresses the pressure fluctuations, but the suppression mechanism is not fully understood. Therefore, this study experimentally investigates the pressure fluctuation generation mechanism and the cavity’s effect on suppressing the vibration. Furthermore, it aims to suppress the vibration by modifying the nozzle tip shape. The vibration level was measured on a lab-scale turbine and CFD analysis to reveal the generation of pressure fluctuation. As a result, the predominant frequency of the vibration corresponds to the blade passing frequency and the pressure fluctuation at the nozzle tip. The cavity and nozzle tip shape show a significant influence on pressure and vibration characteristics and turbine performance.

Effect of Al or Ti addition on the Ferrite Formation in Ultra-low Oxygen Weld Metal of Low Carbon Steel

Effect of Al or Ti addition on the ferrite formation in ultra-low oxygen (about a few tens ppm) weld metal of low carbon steels were investigated. A bead-on-plate welding experiments were performed with a Tungsten Inert Gas (TIG) welding system. The double nozzle was attached to the welding torch used, Ar was passed along the outer nozzle and He is added along the inner nozzle. Optical micrographs showed that primary ferrite appeared along prior austenite grain boundaries and that as the temperature is decreased ferrite side plates were grew into grain interior. Their formation positions were approached to the welding end as the decreasing Al and increasing Ti content. This change in ferrite formation position attributed on the ferrite formation temperature, which was assumed to increase as the decreasing Al and increasing Ti content. Energy dispersive X-ray spectroscopy analysis of inclusions showed that Al and Ti were mainly associated with O, it was obvious that the inclusions in the steels were Al- and Ti- oxide inclusions. Al-oxide inclusions were not favourable acicular ferrite nucleation sites and that the inclusions contributing to acicular ferrite formation were Ti-oxide ones. The number density of acicular ferrite was small. This indicated that acicular ferrite formation was suppressed because the number density of inclusions was low under the ultra-low oxygen welding condition.

Rotating co-flow jets with horizontal lip and shape transition

Purpose Control over large-scale coherent structures and stream-wise vortices lead to enhanced entrainment/conservation of the jet which is desirable for most free jet applications such as design of combustion chamber in jet engines and flame length elongation of welding torch used for metal cutting. Design/methodology/approach A co-flow nozzle with lip thickness of 2 mm, between the primary (inner) and secondary (outer) flow, is selected. Three nozzle combinations are used, i.e. C–C (circle–circle), C–E (circle–ellipse) and C–S (circle–square) for acquiring comparative data. For these nozzle combinations, inner nozzle exit plane is kept as a circle, whereas the outer nozzle exit planes are varied to circle, ellipse and square. The exit plane area of outer nozzle for the nozzle combinations has equivalent diameter, De. The nozzles are fabricated in a way that the outer nozzle can be rotated along the longitudinal axis, keeping the inner nozzle intact. Findings The C–C nozzle combination is effective in low Mach number regime in decaying the jet, when the rotational component is introduced. Around 30% reduction in the jet core length is observed for the C–C nozzle combinations without any lip. The C–E nozzle shows sedative result in decaying or preserving the jet. The C–S nozzle combination shows interesting phenomenon, whereby the low subsonic case tends to conserve the jet by 15% and the higher subsonic case tends to decay the jet by 10%. Originality/value The developed nozzle systems show both conservative and destructive effect on the jet, which is desirable for the mentioned applications.

Achieving uniform heat transfer coefficient in coaxial pulsating jet

The main aim of the present paper is to investigate the inverse design of uniform distribution of heat transfer coefficient on the target plate by employing coaxial jet in the steady and pulsating state. The objective function is defined as the root-mean-square of the deviation of the local Nusselt number on the target plate in computational fluid dynamics simulation from the desired Nusselt number. The heat transfer search method minimizes the objective function. The geometric and fluid parameters are taken into account as design variables. Firstly, optimization in the steady state for the target Nusselt numbers 7, 10 and 13 is carried out and the values of the objective function in the optimal state are found to be 0.51, 0.18 and 0.314, respectively. The range of design variables in the steady and pulsating state is similar, while the heat transfer rate of the pulsating state is higher than that of the steady state. The variations of velocity in the inner and outer nozzles with time are considered to have a sine–sine, cosine–sine and constant–sine behavior. Optimization is carried out in the pulsating state for the Nusselt numbers 33, 44, 55 and 57. The objective function for these numbers in the optimal state is less than 0.02. By employing the conjugate gradient method with adjoint equation and the optimal value of design variables, the distribution of Nusselt number on the target plate in the steady and pulsating state for the constant–sine velocity case is experimentally estimated. The difference between experimental results and the value of the target Nusselt number is about 4–14%, indicating a good agreement between the two approaches.

Multifunctional Calcium-Deficient Hydroxyl Apatite-Alginate Core-Shell-Structured Bone Substitutes as Cell and Drug Delivery Vehicles for Bone Tissue Regeneration.

In this work, we fabricated unique coiled-structured bioceramics contained in hydrogel beads for simultaneous drug and cell delivery using a combination of bone cement chemistry and bioprinting and characterized them. The core of the calcium-deficient hydroxyl apatite (CDHA) contains quercetin, which is a representative phytoestrogen isolated from onions and apples, to control the metabolism of bone tissue regeneration through sustained release over a long period of time. The shell consists of an alginate hydrogel that includes preosteoblast MC3T3-E1 cells. Ceramic paste and hydrogel were simultaneously extruded to fabricate core-shell beads through the inner and outer nozzles, respectively, of a concentric nozzle system based on a material-extruding-based three-dimensional (3D) printing system. The formation of beads and the coiled ceramic core is related to both alginate concentration and printing conditions. The size of the microbeads and the thickness of the coiled structure could be controlled by adjusting the nozzle conditions. The whole process was carried out at physiological conditions (37 °C) to be gentle on the cells. The alginate shell undergoes solidification by cross-linking in CaCl2 or monocalcium phosphate monohydrate (MCPM) solution, while the hardening and cementation of the α-tricalcium phosphate (α-TCP) core to CDHA are subsequently initiated by immersion in phosphate-buffered saline solution. This process replaces the typical sintering of ceramic processing to prevent damage to the hydrogel, cells, and drugs in the beads. The cell-loaded beads were then cultured in cell culture media where the cells could maintain good viability during the entire testing period, which was over 50 days. Cell growth and elongation were observed even in the alginate along the CDHA coiled structure over time. Sustained release of quercetin without any initial burst was also confirmed during a test period of 120 days. These novel structured microbeads with multibiofunctionality can be used as new bone substitutes for hard tissue regeneration in indeterminate defect sites.