Multi-nozzle System Research Articles

Performance assessment of the multi-nozzle injection MQL system for cleaner machining of hardened AISI D2 steel concerning power consumption

ABSTRACT Sustainable hard machining is a pressing need in manufacturing industries for techno-social, economic and environmental benefits to machine difficult-to-cut materials. Thus the present study investigates finish turning of hardened AISI D2 steel using a MTCVD coated carbide insert (TiN-TiCN-Al2O3) with geometry CNMG120408FW and grade WK05CT under a multi-nozzle MQL system using LRT 30 mineral oil (50 ml/hr flow rate, 6 bar compressed air pressure, 30 mm nozzle distance from tool tip) for minimal quantity lubrication at both the rake and flank zones for assessment of machinability. Flank wear lies between 0.79 and 0.155 mm and within the failure criterion limit of 0.2 mm. Arithmetic surface roughness trials have been within 0.361–0.877 microns and within the 1.6 microns acceptable range. The cutting temperature has been between 80.7°C and 226.9°C and even below 200°C in the majority of runs. The cutting power lies within 0.432kW–0.804kW. The optimal parametric combination has been found to be d=0.1 mm, f=0.05 mm/rev and v=80 m/min respectively and improvement has been observed over dry cutting. RSM models are found to be statistically significant. Application of multi-nozzle MQL in machining of hardened steel outperformed through machinability assessment and may be adopted in shopfloor for sustainability..

3D printing sequentially strengthening high-strength natural polymer hydrogel bilayer scaffold for cornea regeneration.

3D printing of high-strength natural polymer biodegradable hydrogel scaffolds simultaneously resembling the biomechanics of corneal tissue and facilitating tissue regeneration remains a huge challenge due to the inherent brittleness of natural polymer hydrogels and the demanding requirements of printing. Herein, concentrated aqueous solutions of gelatin and carbohydrazide-modified alginate (Gel/Alg-CDH) are blended to form a natural polymer hydrogel ink, where the hydrazides in Alg-CDH are found to form strong hydrogen bonds with the gelatin. The hydrogen-bonding-strengthened Gel/Alg-CDH hydrogel demonstrates an appropriate thickened viscosity and shear thinning for extrusion printing. The strong hydrogen bonds contribute to remarkably increased mechanical properties of Gel/Alg-CDH hydrogel with a maximum elongation of over 400%. In addition, sequentially Ca2+-physical crosslinking and then moderately chemical crosslinking significantly enhance the mechanical properties of Gel/Alg-CDH hydrogels that ultimately exhibit an intriguing J-shaped stress-strain curve (tensile strength of 1.068 MPa and the toughness of 677.6 kJ/m2). The dually crosslinked Gel-Alg-CDH-Ca2+-EDC hydrogels demonstrate a high transparency, physiological swelling stability and rapid enzymatic degradability, as well as suturability. The growth factor and drug-loaded biomimetic bilayer hydrogel scaffold are customized via a multi-nozzle printing system. This bioactive bilayer hydrogel scaffold considerably promotes regeneration of corneal epithelium and stroma and inhibits cornea scarring in rabbit cornea keratoplasty.

Development of Multi-Nozzle Electrospray Device for Fabrication of Cathode Catalyst Layer on Polymer Electrolyte Fuel Cells

We have been researching manufacturing methods of catalyst layers to improve the effective utilization rate of Pt in polymer electrolyte fuel cells. In our previous research1-3, we demonstrated experimentally that an electrospray (ES) method was able to make great progress in the interface formation between the electrolyte polymer ionomer and the Pt supported on carbon1,3 or conductive ceramics2, and that the immediate drying of the catalyst layer ink also greatly contributes to the improvement of Pt effectiveness. Since the ink droplets had already dried when these were deposited on the membrane, we proposed that the ink drying process can be reduced and that the cost of producing the catalyst layer is also greatly reduced. However, since the amount of catalyst applied is very small with a single nozzle, we also proposed that a multi-nozzle system is indispensable in order to adapt to the actual catalyst layer formation process.Therefore, we are jointly developing the ES manufacturing system with a multi-nozzle device (Fig. 1a) in a collaboration between the University of Yamanashi and Meiko Co., Ltd. We developed the first prototype machine, MES-Lab.α, for R & D, which features options such as nozzle material, multi-nozzle structure, coating treatment of nozzle tip, nozzle fixing adhesive, suck-back method, and ink energization method, among others. We have completed a new design for a basic 72-nozzle block (Fig. 1b), which incorporates all the above new materials and new structures and is compatible with the production of industry-standard electrodes (5 cm x 5 cm).We have developed a new system to control and maintain the shape of the Taylor cone, which is essential for stable coating. This is a device that precisely controls the internal pressure of the ink tank above the nozzle (Fig. 1b). We are also developing a multi-nozzle to increase the coating rate. With conventional methods, the quantity of spray depends on the nozzle diameter, but with the ES method it does not. To increase the ejected quantity for ES, the number of nozzles must be increased. We developed a 72-pin multi-nozzle, for which the coating rate is enough for research devices but not for mass production. It is estimated that more than 1000 pins are required for a mass-production multi-nozzle device. However, it is very inefficient to develop a nozzle device with 1000 pins by trial and error. It was found that the results of an electric field simulation show similarity to the actual distribution of the catalyst layer after coating (Fig. 2). We have introduced this simulation technique for the optimization of the multi-nozzle design. We believe that the design of the nozzle model using simulation will greatly contribute to the development of efficient, low-cost mass production equipment. Acknowledgement This work was partially supported by funds for the SPer-FC, the ECCEED’30-FC, and the ECCEED_ES projects from NEDO and the FCyFINE project from the Regional Innovation Ecosystems Program of MEXT. References K. Takahashi, K. Kakinuma, and M. Uchida, J. Electrochem. Soc., 163, F1182-F1188 (2016).K. Takahashi, R. Koda, K. Kakinuma, and M. Uchida, J. Electrochem. Soc., 164, F235-F242 (2017).S. Cho, K. Tamoto, and M. Uchida, Energy Fuels, 34, 14853−14863 (2020). Figure 1

Numerical Simulation of Erosion in Pelton Spear Valve at Different Openings

The spear valve is one of the most eroded hydro-mechanical components of the Pelton turbine operating in sediment-laden conditions. The spear valve is used to regulate or control the flow. In a multi-nozzle system, though having the same design, the spear valves show varying erosion patterns and intensities. The only difference was found to be the openings of the nozzle/spear valve. This demonstrates that there is some sort of connection between the nozzle opening and the erosion of the spear valve. The difference in erosion intensity in different spear valves can be seen on the site but the underlying phenomenon behind the erosion needed to be studied numerically. In this research, erosion patterns were numerically investigated using an open-source CFD tool, OpenFOAM. For this simulation, the sediment particles and their properties were incorporated into the flow using the built-in Lagrangian library of the OpenFOAM. To investigate the erosion in real time, a transient simulation was undertaken for various nozzle openings. This study only focuses on the erosion at the tip of the spear valve neglecting other parts of the nozzle. This study demonstrates that the erosion in the tip of the spear valve increases with the restriction in flow.

Continuous ink supply and circulation system for a multi-nozzle electrospray

The electrospray deposition method has been used in many applications, such as mass spectroscopy, thin film deposition, bio-applications, painting and coating. However, low flow rates must be used for electrospraying to maintain a stable cone jet mode, while most applications require high throughput. To overcome the slow deposition rate, the use of a multi-nozzle electrospray should be considered. In a typical multi-nozzle electrospray system, ink in a syringe barrel is fed to the nozzles by a syringe pump or pressure regulator. However, if the ink in the syringe barrel is depleted, the entire process should be stopped to refill the ink. In this study, we propose a new head design and an ink supply system for a multi-nozzle electrospray system so that ink can be continuously supplied to the nozzles without ink being depleted during the electrospray process. The proposed system is based on circulation through the multi-nozzle electrospray head so that unexpected air bubbles in the head can be easily removed.

Engineering uniformity in mass production of MWCNTs/epoxy nanofibers using a lateral belt-driven multi-nozzle electrospinning technique to enhance the mechanical properties of CFRPs

Electrospinning is one of the most diverse, cost-effective, and ecologically renowned methods for generating continuous nanofibers, but electrospinning of thermosetting polymers like epoxy and their mass volume productions have been a major challenge in recent years. This study proposes a fabrication method by addressing electrospun MWCNTS/epoxy (CNT/epoxy) nanofiber's volume processing, reproducibility, and accuracy issues in an effective manner. Lateral belt-driven (LBD) multi-nozzle electrospinning is here newly adopted to enhance the mechanical properties of the carbon fiber-reinforced polymer (CFRP) laminates. With the LBD approach, the electric field can be uninterruptedly distributed to deposit a uniform layer of CNT/epoxy scaffolds over the entire width of CFRP prepreg. This study optimizes the distance between two nozzles, the motion of the lateral belt, and the electrospinning period. The laminates made of coated CFRP show enhanced mechanical properties when compared to pristine CFRPs. Under high-stress conditions, these CFRP laminates' interlaminar shear strength (ILSS) and fatigue performance demonstrated 29% and 27% improvements, respectively. This study, which demonstrated the success of using an LBD multi-nozzle system, has enormous opportunities to produce thinner and continuous fibers with more concentrated collections at a faster rate, which is critical for commercial applications.

Continuous production of cellulose microbeads by rotary jet atomization

The replacement of plastic microbeads with biodegradable alternatives is essential due to the environmental persistence of plastics and their accumulation within the human food chain. HypothesisCellulose microbeads could be such alternative, but their production is hindered by the high viscosity of cellulose solutions. It is expected that this viscosity can be harnessed to induce filament thinning of jets of cellulose solutions to create droplets with diameters within the micrometre range, which can then be converted to solid cellulose microbeads via phase inversion. ExperimentsA 3D printed rotating multi-nozzle system was used to generate jets of cellulose dissolved in solutions of [EMIm][OAc] and DMSO. The jets were subject to Rayleigh breakup to generate droplets which were captured in an ethanol anti-solvent bath, initiating phase-inversion, and resulting in regeneration of the cellulose into beads. FindingsControl of both process (e.g. nozzle dimensions) and operational (e.g. rotational speed and pressure) parameters has allowed suppression of both satellite droplets generation and secondary droplet break-up, and tuning of the filament thinning process. This resulted in the continuous fabrication of cellulose microbeads in the size range 40–500 μm with narrow size distributions. This method can produce beads in size ranges not attainable by existing technologies.

Novel genetic algorithms for femtoliter jetting using multi-nozzle MEMS printheads (femtoliter jetting using MEMS printheads)

Piezoelectric inkjets have enabled highly precise, customized material deposition for the micro and nanofabrication industries. Inkjet performance relies on a delicate balance between hardware manufacturing precision and tolerancing, material rheology, and the associated actuation-waveform for drop ejection. For a multi-nozzle inkjet system, the important performance metrics include drop volume resolution, inter-nozzle drop volume variation, overall drop-placement accuracy, jetting frequency (related to throughput), and long-term reliability. Cutting-edge applications typically require minimizing drop volume to 1 pL or less; drop placement accuracy of <10 mm, 3-σ; maintaining high jetting frequency of >10 kHz; and achieving reliable long-term operation, e.g., >1 month of continuous operation without any faults. Here, we strive towards a global optimum in drop resolution while adhering to constraints related to placement accuracy and reliability, at a fixed jetting frequency of 14.2 kHz. Our approach is to explore novel genetic algorithms that generate highly complicated waveforms (>100 parameter waveforms) to achieve our global optimum goals. Our automated genetic algorithm (a) starts from rudimentary waveforms that are easily constructed based on empirical knowledge and manual tuning, and (b) systematically increases complexity to generate highly sophisticated waveforms with increasingly greater number of parameters, an approach that is unattainable through manual tuning processes. This approach was developed and implemented using a commercial MEMS-based Fujifilm Samba G3L piezo-inkjet system with 2048 sub-20μm nozzles, with an aqueous diethylene glycol-based ink supplied by Fujifilm. The genetic algorithm operated based on a variable-length chromosome which started with 10 parameter waveforms and evolved into waveforms defined by > 100 parameters, resulting in drop-volume resolution of <600 fL, and maintaining drop placement accuracy to within 10 μm, 3-σ with reliable jetting over at least 30 print fields with the same waveform, each field nominally composed of 340 drops. The best result presented yielded drops with an average volume of 568 fL, which exceeded the manufacturer's specification for drop volume of 2.4 pL by 4.23 times. In summary, we have developed a novel framework for machine-in-the-loop waveform optimization in multi-nozzle inkjet systems to achieve previously unattained drop resolution with high reliability and accuracy.

Experimental and CFD analysis of multi nozzle ejector system for aircraft compact heat exchanger applications

ABSTRACT In the present study, analysis of multi-nozzle ejector systems for aircraft compact heat exchanger applications is performed. CFD procedure is validated with experimental data of a single-nozzle ejector. Experimentation is carried out with a multi-nozzle ejector to evaluate the performance of the system at ambient temperature (307 K). Based on the pressure drop data obtained from the experiment, the computational domain for CFD studies is simplified. Further the analysis of air ejector systems at higher operating temperature (813 K) is performed. Primary air inlet temperatures and pressure are varied as parameters. Velocity contour, pressure contour and temperature contours are plotted for cold and hot fluid cases. High pressure zones are observed in the mixing regime of primary and secondary fluid. Improper mixing of primary and secondary fluid is observed. The mass ratio is reduced with increase in primary pressure. Based on the CFD results at high temperature, the performance of the compact heat exchanger is computed using the heat exchanger carpet curve for the different secondary (cold) air flows induced by the ejector.

Fabrication of Cathode Catalyst Layer By Use of Multi-Nozzle Electrospray Method on Polymer Electrolyte Fuel Cells

We have been researching manufacturing methods of catalyst layers in order to improve the effective utilization rate of Pt in polymer electrolyte fuel cells. In our previous research1-3, we demonstrated experimentally that an electrospray (ES) method was able to make great progress in the interface formation between the electrolyte polymer ionomer and the Pt supported on carbon1,3 or conductive ceramics2, and that the immediate drying of the catalyst layer ink also greatly contributes to the improvement of Pt effectiveness. Since the ink droplets had already dried when these were deposited on the membrane, we proposed that the ink drying process can be reduced and that the cost of producing the catalyst layer is also greatly reduced. However, since the amount of catalyst applied is very small with a single nozzle, we also proposed that a multi-nozzle system is indispensable in order to adapt to the actual catalyst layer formation process.Therefore, we are jointly developing the ES manufacturing system with a multi-nozzle device (Fig. 1a) in a collaboration between the University of Yamanashi and Meiko Co., Ltd. We developed the first prototype machine, MES-Lab.α, for R & D, which features options such as nozzle material, multi-nozzle structure, coating treatment of nozzle tip, nozzle fixing adhesive, suck-back method, and ink energization method, among others. We have completed a new design for a basic 72-nozzle block (Fig. 1b), which incorporates all of the above new materials and new structures and is compatible with the production of industry-standard electrodes (5 cm x 5 cm).The performance of the PEFC cell using the cathode catalyst layer produced by this ES device was superior to that of a cell using the conventional pulse-swirl-spray device (PSS). We prepared the catalyst layer according to two different ionization methods (positive (ESP), and negative (ESN) ionization), and compared these with that prepared by the PSS method.3 The catalyst layers prepared by ESN successfully mitigated oxygen transport resistance. The highest porosity, which induced better water management, revealed superior performance at high current. Moreover, we confirmed the importance of the proton conduction in the catalyst layer through the ionomer contents. Thinly coated ionomer film on the catalyst surface revealed that lower resistance originates from the ionomer film on the Pt surface, RCL, film , but poor σ H+cath. , as evaluated for low contents of ionomer in the catalyst layer. These results also suggest that we will be able to achieve superior actual cell performance for catalyst layers prepared via ES using modified ionomer chemical structures, for which there is enhanced H+ conductivity, σ H+cath. , via, e.g., increased ion exchange capacity, and oxygen permeability3 (Fig. 2). Acknowledgement This work was partially supported by funds for the “Superlative, stable, and scalable performance fuel cell” (SPer-FC) and the “Electrolytes, catalysts and catalyst layers with extraordinary efficiency, power and durability for PEFCs to 2030” (ECCEED’30-FC) projects from the New Energy and Industrial Technology Development Organization (NEDO) and the “Yamanashi Frontier for Innovation and Ecosystem” (FCyFINE) project from the Regional Innovation Ecosystems Program of the Ministry of Education, Culture, Sports, Science and Technology (MEXT). References Takahashi, K. Kakinuma, and M. Uchida, J. Electrochem. Soc., 163, F1182-F1188 (2016).Takahashi, R. Koda, K. Kakinuma, and M. Uchida, J. Electrochem. Soc., 164, F235-F242 (2017).Cho, K. Tamoto, and M. Uchida, Energy Fuels, 34, 14853−14863 (2020). Figure 1

Effect of spray properties on aerosol scavenging efficiency with water mist

In the foreseen decommissioning plans of damaged Fukushima Daiichi reactors, submicron aerosol particles will be generated when retrieving fuel debris from reactor buildings by cutting it into small pieces. A multi-nozzle spray system will be used to scavenge these aerosol particles inside the primary containment vessel. To improve the aerosol removal efficiency of the multi-nozzle spray system, it is now necessary to study the aerosol removal performance by different single spray nozzles with different spray properties (spray angle, droplet velocity, etc.). To improve the aerosol scavenging efficiency, a new method with water mist was proposed to aggregate with aerosol particles and form large-sized coagulated aerosol-mist particle clusters, which can subsequently be removed by spray with higher efficiency. In this study, the effect of spray properties on aerosol removal efficiency with preexisting water mist was investigated using three different spray nozzles. The experimental results showed that a larger droplet velocity led to stronger vortex circulation and faster gaseous entrainment from outer spray area into spray region, resulting in a smaller circulation period of gas entrainment by spray and higher aerosol removal efficiency. The numerical simulations of aerosol removal by different spray nozzles without mist were also conducted to provide more insights into the aerosol removal process. By comparing the experiment and simulation results, it is found that the accumulated spray water in the lower plenum of the vessel and the water film formed on the vessel sidewalls also contributed to aerosol removal, especially for the particles with large Stokes numbers.Copyright © 2021 American Association for Aerosol Research

Multi-nozzle spray cooling of a reactor pressure vessel steel plate for the application of ex-vessel cooling

Spray cooling is a versatile technology for various cooling applications involving high surface heat fluxes. Experimental facility was built to study heat transfer performance of an upward multi-nozzle array of water sprays impacting a surface of heated plate made of reactor vessel grade steel. The effect of inclination angles of the steel surface on the cooling performance was investigated to assess heat transfer in complex semispherical/semielliptical geometry of large reactor lower head and to address possible application of spray cooling in severe accident management (SAM) of light water reactors (LWRs) based on In-vessel melt retention with external reactor vessel cooling (IVR-ERVC). Joule heating of SA302B steel foil of 0.15 mm thickness and surface area of 96 cm2 enabled prototypic heat fluxes to be evacuated during reactor accident. A 2 × 3 array of full jet narrow-coned pressure-swirl spray nozzles was used to reproduce multi-nozzle cooling. The tests were conducted as a series of consequent steady states realized at stepwise increasing power and surface heat fluxes up to the maximum values of 29 kW and 2.97 MW/m2 limited in the specific facility design. Seven surface inclinations, between 0° and 90° were tested and no significant variations in spray cooling performance with the inclination of the heated surface was found. The results indicated a promising prospect of using a multi-nozzle array system for cooling of large surface area of reactor lower head. Much higher heat fluxes can be safely extracted by spray cooling in comparison with the critical heat fluxes that appeared at RPV water pool cooling at natural convection. The maximum value of heat flux at direct spray impact zones and its drop-off slightly from the center to the periphery of the spray cone was detected in the tests. The water flow rate and liquid subcooling significantly influenced maximum steel surface temperature but had no noticeable effects on surface temperature uniformity. The spray-to-spray interaction had no observable effects on local surface temperatures, however, the colliding zones where four spray cones have visible effects on local surface temperatures due to poor liquid momentum. The results also showed that more uniform liquid film distribution could be obtained for some inclinations because of improved liquid drainage, which in turn leads to maintaining low surface temperatures.

Multi-Nozzle Pneumatic Extrusion-Based Additive Manufacturing System for Printing Sensing Pads

This paper developed a multi-nozzle pneumatic extrusion-based additive manufacturing (AM) system and applied it to print multi-material polymers and conductive sensing pads. We used pneumatic extrusion nozzles to extrude the liquid material and then cured it by an ultraviolet (UV) light source. The multi-nozzle pneumatic extrusion-based additive manufacturing system mainly integrates both PC-based HMI and CNC controller to operate the three-axis motion and the extrusion flow control. Moreover, the peripheral I/Os include both positive and negative pressure and also the curing light source. A D/A controller is also applied to control the value of the pneumatic pressure. The coding part utilizes the numerical control software along with the PLC planning to operate the AM machine automatically. Our experiment is conducted by using Simplify3D, a commercial 3D printing slicing software. Different requirements were set for extrusion nozzles with different materials, and then we executed the path controlling G-code data by Python Language. Our system successfully prints multi-material polymer structure pads which include the hard and soft material pad fabricated in double-layers, triple-layers and also the grid structure. Finally, we find that the printed pad has conductivity.

Numerical simulation of gas‐assisted polymer‐melt electrospinning: Parametric study of a multinozzle system for mass production

AbstractIn this study, we developed a multiphysics model for simulation of a gas‐assisted melt‐electrospinning (GAME) process, focusing on jet formation and propagation behavior. By numerically calculating the stresses acting on the jet during a single‐nozzle GAME process, the shear viscous stress was identified as the main factor with respect to jet stretch; thus, the relationship between shear viscous stress and jet thickness was investigated. The jet stretch ratio increased sharply when shear viscous stress reached the level at which jet sharpening occurred, leading to stable jet formation. We defined this stress as the critical shear viscous stress to determine stable spinnability. By imposing an electric field distribution calculated for a multi‐nozzle array (number of nozzles, tip‐to‐tip distance, and applied voltage) on the boundary condition of the single‐nozzle GAME simulation model, multinozzle GAME was simulated; this enabled proposal of a spinnability diagram for stable spinning.

The impact on the mechanical properties of multi-material polymers fabricated with a single mixing nozzle and multi-nozzle systems via fused deposition modeling

Multi-material 3D printing and process parameters optimization using multiple extruders are the significant challenges of fused deposition modeling (FDM). This paper focuses on the filament extrusion method and presents a comparison of two modes: multi-material single mixing nozzle and multi-material multiple nozzles, thereby linking technology with the mechanical properties. Tensile testing specimens were printed in two different scenarios to validate the comparison: (1) multi-material multi-layered section printed using a multi in-out single mixing nozzle and (2) multi-material multi-layered section printed using a multiple extrusion nozzle within the same carriage. Both modes followed a rectilinear infill pattern and different material combinations. The material combinations implemented included ABS-HIPS, ABS-PLA, PLA- HIPS, and PLA-HIPS-ABS. A behavioral study was evaluated on the mechanical properties of these materials. The results provide a tool for selection on which type of mode is considered suitable for maximizing efficiency and performance to fabricate a multi-material 3D printed product.

A novel printing channel design for multi-material extrusion additive manufacturing

Additive manufacturing has a great potential in terms of its capability to produce components with complex geometries and to make multi-material and composite products by combining different materials in a single manufacturing platform. Current trends for the multi-material extrusion additive manufacturing process are categorized by multi-nozzle systems and multi-material inlet systems. In the case of multiple nozzle system, materials are deposited from different nozzles in sequence. On the other hand, in the case of multi-material inlet system, different materials are sent into a mixing tube and deposited as a mixture of materials. In this case, functionally graded parts can be fabricated by changing the volume fraction of two or more materials. Hence, the fabrication of parts with a continuous material supply by varying ratios for the extrusion technologies requires the development of printing heads with suitable printing channels, capable of varying the mixing ratio of different materials. To evaluate the effect of different printing channel designs on the material’s flow pattern and the functionally graded material printability, this paper presents a three-dimensional transient computational fluid dynamics (CFD) simulation of the two miscible liquid-liquid system in a printing channel. Different geometries and materials are considered

An Experimental Study of Grinding Performances of a Mild Steel under Different Environmental Conditions using Various Types of Nozzles

Grinding is a mechanical metal removal process used in manufacturing industries. In this process, the material is removed from a work-piece material by an abrasive wheel. This process gives better surface finish and close tolerance. Grinding process removes material by shearing, ploughing, rubbing and brittle fracture with high- speed and a high input of energy per unit volume. The coolant or grinding fluid is used to reduce the temperature in grinding zone and also it is used as a lubricant into grinding zone. In present work, a five port multi-nozzle system has been developed and performance of this nozzle has been compared with flood type copper cooling nozzle under different environmental conditions. Two parameters (chip characteristics, surface roughness) of grinding are considered to find the suitable process for grinding of a mild steel specimen. From this experimental investigation, it can be observed that in wet condition, five port multi-nozzle system provides better surface finish as well as it is more economical.

Staggered swirler arrangement in two self-excited interacting swirl flames

Interference of acoustic and convective disturbances controls the development of self-excited combustion oscillations of a lean-premixed swirl-stabilized flame with a central bluffbody. How this interference mechanism influences the dynamics of multiple interacting flames in a multi-nozzle environment is currently unknown. Here we present observations of a multi-nozzle system's response to staggered swirler arrangements (ξsw, 1 ≠ ξsw, 2) as compared to non-staggered arrangements; the distance between the swirler and the flame is the dominant length scale of vortical disturbances. Our results demonstrate that a slight modification of the swirler arrangement in the streamwise direction – staggered or non-staggered – has a remarkable influence on the stability map of the whole combustion system. Phase-resolved flame imaging measurements indicate that under non-staggered conditions interacting swirl flames feature a coherent motion during a period of oscillation. By contrast, the staggered swirler combination creates significantly non-symmetric flame dynamics, disturbing the development of well-organized motion over the entire reaction zone. Flame surface modulations in the lateral direction are particularly pronounced due to the formation of non-symmetric convection delays of vortical disturbances between adjacent swirl nozzles. For a given swirler arrangement, the system's response to a wide range of combinations of mean nozzle velocities, including symmetric (u¯1=u¯2) and non-symmetric (u¯1≠u¯2) conditions, were explored to account for the simultaneous effects of the two convection parameters. Our data show that a major determinant of the onset of the instability is the combination of the Strouhal numbers, 〈St1, St2〉, which can be even or uneven depending on the manipulation of the convection time of each nozzle.

Simple-jet mode electrosprays with water. Description, characterization and application in a single effect evaporation chamber

Electrohydrodynamic atomization (EHDA) is a technique which uses the influence of strong electric fields to manipulate the break-up of a liquid, pumped through a capillary nozzle, into droplets. In this work, an extended description of a specific high flow EHDA mode, known as the simple-jet mode, is presented. In it, a review of different works published about the mode is presented as well as results about the droplet population generated with varicose and whipping break-up using water as the atomized liquid. Additionally, experiments were conducted to investigate whether such atomization method could be used to improve the efficiency of droplet in air evaporation, using a single effect evaporation chamber coupled with a EHDA multinozzle system functioning as a shower head. The liquid used in these experiments was a solution of water and NaCl (35 g L−1) to simulate sea water average concentrations. The results have shown that, the manipulation of the droplet diameter, droplet size distribution and spray angle, provided by EHDA, could improve the droplet evaporation efficiency by up to 40% when combined with, e.g. forced convection and higher inlet temperatures.

All Inkjet-Printed Amperometric Multiplexed Biosensors Based on Nanostructured Conductive Hydrogel Electrodes.

Multiplexing, one of the main trends in biosensors, aims to detect several analytes simultaneously by integrating miniature sensors on a chip. However, precisely depositing electrode materials and selective enzymes on distinct microelectrode arrays remains an obstacle to massively produced multiplexed sensors. Here, we report on a "drop-on-demand" inkjet printing process to fabricate multiplexed biosensors based on nanostructured conductive hydrogels in which the electrode material and several kinds of enzymes were printed on the electrode arrays one by one by employing a multinozzle inkjet system. The whole inkjet printing process can be finished within three rounds of printing and only one round of alignment. For a page of sensor arrays containing 96 working electrodes, the printing process took merely ∼5 min. The multiplexed assays can detect glucose, lactate, and triglycerides in real time with good selectivity and high sensitivity, and the results in phosphate buffer solutions and calibration serum samples are comparable. The inkjet printing process exhibited advantages of high efficiency and accuracy, which opens substantial possibilities for massive fabrication of integrated multiplexed biosensors for human health monitoring.