Small Nozzle Research Articles

Nanomechanical characterization of 3D printed cement pastes

Cement-based 3D printing (additive manufacturing) has drawn significant attention in recent years as an emerging construction technology because of its potential environmental and economic benefits over the traditional cast-in-place concrete construction. Most research to date has focused on the macroscale properties of the printed structure. However, the performance of the printed materials depends on the properties of the individual filaments. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive X-ray spectroscopy was used to determine the effects of the printing process through extrusion on the local elastic indentation modulus and hardness of filaments in 3D printed cement paste structures. Dynamic changes in the water-to-cement ratio during the extrusion process combined with stress-induced dissolution of the cement particles led to variation in the median modulus of the printed filaments, with filaments having values greater than 23 GPa or lower than 20 GPa. Extrusion through a small diameter nozzle affected the mesoscale assemblage of the primary hydrate phases and led to printed filaments having a more uniform mesoscale packing of calcium silicate hydrates (C–S–H) with the disappearance of loosely packed C–S–H compared to their traditionally cast counterparts.

Isolation of back pressure waves in a valveless pulse detonation combustor with inlet air of high total temperature

In order to achieve the effectively isolation of back pressure waves in a valveless pulse detonation combustor (PDC) within a short axial distance, a combined aero-valve was designed and tested with a single tube PDC at firing frequencies from 10 Hz to 25 Hz. Nozzles of different size were designed to adjust the bleeding air of the combined aero-valve. The nozzles’ effect on the isolation of the back pressure waves were discussed. Numerical simulations were carried out to reveal interactions between the back pressure waves and the combined aero-valve. The experimental results proved that the combined aero-value was effective in isolating the back pressure waves at firing frequencies from 10 Hz to 25 Hz for the baseline case. When a smaller nozzle was installed, the combined aero-valve would lose the ability to isolate the back pressure waves at low firing frequencies. Numerical simulations showed that the supersonic flow in the shock isolator channel was the key factor to realize completely isolation of the back pressure waves. For the cases with pressure oscillations appeared at the inlet of the isolation section, the back pressure waves would push the shock wave out of the channel and destroy the supersonic flow in the shock isolator channel, while the supersonic flow did not disappear for the cases when the back pressure waves were completely isolated, the shock wave in the shock isolator channel was just pushed forward a certain distance and would recover to the initial position as the filling process of the PDC started.

Augmenting the performance of photovoltaic panel by decreasing its temperature using various cooling techniques

The photovoltaic (PV) systems suffer efficiency drop and performance retrogression as their operating temperature increases. This research investigates the routine of polycrystalline silicon PV modules using dissimilar cooling techniques and compares the routine of the PV modules with and without cooling. The available studied PV module output maximum power decreases by up to 0.42% for every one-degree increase in temperature. To investigate the cooling techniques, the experiments were done in July 2021 at the Faculty of Engineering, Ismailia, Egypt (30°35′N 32°16′E). The used cooling methods were; forced air cooling onto the PV module front surface by a direct current fan (case 1); back surface cooling by circulating a coolant in a heat exchanger copper serpentine fixed at the PV module back surface, water (case 2), and copper oxide nanofluid (0.2% mass fraction) (case 3) was used as different coolants in the serpentine; front surface cooling using water as a coolant that flows from small nozzles equally distributed along with the pipe fixes at the PV module frame (case 4). After comparing the recorded results of the four cooling techniques with a conventional system, cooling efficiency, the front PV module surface water cooling technique produced the best results. This technique is easy to be designed, manufactured, and installed. Also, it saves the cost of cleanliness of the surface of the PV module from dirt and dust. These cooling techniques increase the conventional PV system voltage output by 2.7%, 2.43%, 0.9%, and 7.43% and decrease in average temperature by 13.46%, 8.64%, 7.27%, and 29.37%, with an increase in PV energy conversion efficiency by 2.94%, 2.46%, 2.2% and 6.84% via using air cooling, water back cooling, nanofluid back cooling and waterfront cooling respectively.

CFD Analysis of Convergent-Divergent Nozzle for Low Altitude Rocket

The convergent-divergent nozzle in rocket engines is used to turn the chemical energy developed via the combustion chamber into kinetic energy. The wall of the nozzle is properly contoured to efficiently accelerate the combustion product towards the nozzle exit. However, for low-to medium-altitude rockets (typically within the range of 10 to 145 km), nozzle contouring increases the overall production cost due to a more complicated fabrication process. The development of the dual conical nozzle seeks to compromise between performance and ease of fabrication. The present investigation seeks to analyze small rocket nozzles involving a typical conical nozzle, Truncated Optimized Contour (TOC) and Truncated Idealized Contour nozzles and newly designed dual conical nozzles. Rocket nozzles with various divergence angles and exit area ratios are numerically analyzed. It was discovered that the best dual conical nozzle can produce an average thrust comparable to that of a standard conical nozzle. In some cases, the dual conical nozzle outperforms its conical and contoured counterparts. Keywords— Dual conical nozzle, TOC nozzle, TIC nozzle, shockwaves, thrust.

Heat transfer model and cooling performance of converter oxygen lance affected by slag sticking

The heat transfer mechanism and water-cooling effect during oxygen lance blowing changes by slag sticking at the nozzle. In order to effectively overcome this problem, in this study, the equivalent heat transfer method was applied to modify the heat transfer coefficient of the oxygen lance nozzle under different slag thicknesses and steel slag thermal conductivities. In addition, the gas–liquid two-phase heat transfer model was established by computational fluid dynamics numerical simulation, and the cooling effects for different types of oxygen lance nozzles were calculated by the improved model. The results show that the error rate between the calculated value of the modified model and the field measured value was reduced to 3.3%–4.6%. The nozzle with double angle and double flow design was found to be conducive to the improvement of the cooling system. In this study, the best cooling effect was obtained when the flow ratio of large nozzles and small nozzles is 60%/40% and the angle is 12°/17°.

Development of advanced cold crucible melting of titanium alloys

Cold crucible is used to melt reactive metal scrap at elevated temperatures for high quality castings or to produce spherical powders for additive manufacturing. The most advanced crucibles have a small exit nozzle to pour the molten alloy through the bottom opening protected by graphite or ceramic material. The nozzle operates at high temperature and typically lasts several minutes, possibly adding contamination to the outflowing liquid metal. This paper presents new efforts to improve the technique with the aim to achieve a stable commercial process by introducing melting of scrap metal in the presence of liquid flux of different compositions to purify the liquid metal and to enhance thermal effectiveness. The crucial modification in avoiding contamination is a new type of the non-consumable nozzle made of copper segments and the second coil to supply a high frequency electromagnetic field in the vicinity of the nozzle. The nozzle entrance is protected by a thin solidified layer of the same alloy as the main melt. The AC electromagnetic field adds heating at the outflow, modifies the velocity field, gives a possibility to extract particles, and precludes entrainment of slag into the final casting or into the produced powder. The electromagnetic force permits to control the outflow rate and to increase the superheat of the metal at the outlet. The presence of flux permits shielding of the liquid metal from direct contact with the water-cooled side segments of the crucible. The paper demonstrates the effectiveness of numerical modelling to predict and investigate a variety of options in advancement of the cold crucible technique. Figs 8, Refs 13.

Hydrodynamic cavitation for micropollutant degradation in water – Correlation of bisphenol A degradation with fluid mechanical properties

The present work addresses the correlation of bisphenol A (BPA) degradation by hydrodynamic cavitation with the fluid mechanical properties of the cavitating jet in the reactor. The effects of inlet pressure and two orifices were investigated. The fluid mechanics conditions during the reaction were evaluated by optical measurements to determine the jet length, bubble volume, number of bubbles, and bubble size distribution. In addition, chemiluminescence of luminol is used to localize chemically active bubbles due to the generation of hydroxyl radicals in the reactor chamber. The correlation between the rate constants of BPA degradation and the mechanical properties of the liquid is discussed. Here, linear dependencies between the degradation of BPA and the volume expansion of the bubble volume and chemiluminescence are found, allowing prediction of the rate constants and the hydroxyl radicals generated. BPA degradation of 50% was achieved in 30 min with the 1.7 mm nozzle at 25 bar. However, the 1 mm nozzle has been demonstrated to be more energetically efficient, achieving 10% degradation with 30% less power per 100 passes. There is a tendency for the number of small bubbles in the reactor to increase with smaller nozzle and increasing pressure difference.

Experimental and Numerical Study of Heat Transfer Under Lamirazition Condition in a Small Size Supersonic Nozzle

Experimental and Numerical Study of Heat Transfer Under Lamirazition Condition in a Small Size Supersonic Nozzle

Evaluation on the Performance of Automobile Engine Using Air Injection Nozzle in the Intake Manifold

In the present study, a nozzle was used to improve the flow performance of an intake manifold, and its effects on the automobile engine output and the exhaust gas were experimentally studied. It was found that the engine output of a vehicle with a mileage of 30,000 km increased by 4.7% and 6.5% when nozzles with diameters of 5 and 2.5 mm were used. In addition, the engine output of a vehicle with a mileage of 180,000 km increased by 3.3% and 13.3% when nozzles with diameters of 5 and 2.5 mm were used compared to those of the same vehicle when no nozzle was used. Thus, using a nozzle for the inflow of outside air created a uniform combustion environment to improve the engine output and reduce harmful exhaust gases, such as hydrocarbon, carbon monoxide, and nitrogen oxides, by generating vortexes inside the intake manifold and increasing the degree of mixing. Furthermore, the smaller nozzle with a diameter of 2.5 mm had greater effects.

Experimental study of the heat transfer of single-jet impingement cooling onto a large heated plate near industrial conditions

Jet impingement cooling has been intensively studied in the past by many authors because of its important application in the metallurgical industry; however, most of the experiments in the literature are at laboratory scale and, in some cases, not near industrial conditions. In this study, we performed cooling experiments near industrial conditions in a new experimental apparatus with a large nickel plate as test sample, which was heated until 850 ∘C before being cooled by a single circular water jet. Five experimental results are presented with different jet Reynolds numbers, from 9,800 to 120,000, obtained by varying the water flow rate and the nozzle diameter. The presented results are: temperature evolutions during cooling, dissipated heat flux (estimated by solving a 2D inverse heat conduction problem), transverse heat flux at the heat-exchanging surface, and the characteristics (position and velocity) of the rewetting and maximum cooling rate fronts. The increase in the jet Reynolds number increased slightly the heat flux at the stagnation zone, but increased it substantially for positions farther from the impact location. The transverse heat flux increased with the passage of the rewetting front and then decreased, and its magnitude was practically the same regardless of the jet Reynolds number. The change in the nozzle diameter did not affect significantly the heat transfer nor the rewetting front growth, although the heat dissipation was slightly higher with the smaller nozzle, possibly because of the higher jet impact velocity. Finally, we compared the present results with some found in the literature in similar conditions, showing that laboratory experiments are valuable to provide detailed information, especially near the stagnation zone, but large-scale experiments allow obtaining macroscale data of the cooling process.

Low-Thrust Solid Rocket Motors for Small, Fast Aircraft Propulsion: Design and Development

Small, low-thrust, long-burn-time solid propellant rocket motors could provide propulsion for a new class of kilogram-scale, transonic, uncrewed aerial vehicles (UAVs). This paper investigates technological challenges of small, low-thrust solid rocket motors: slow-burn solid propellants, motors that have low thrust relative to their size (and thus have low chamber pressure), thermal protection for the motor case, and small nozzles that can withstand long burn times. Slow-burn propellants were developed using ammonium perchlorate and 0–20% oxamide (burn-rate suppressant), with burn rates of at 1 MPa. Using these propellants, a low-thrust motor successfully operated at a thrust/burn area ratio 10 times less than that of typical solid rocket motors. This kilogram-scale motor can provide 5–10 N of thrust for 1–3 min. An ablative thermal protection liner was tested in these firings, and a new ceramic-insulated nozzle was demonstrated. This paper shows that small, low-thrust solid motors are feasible and presents a baseline design for the integration of such a motor into a small UAV.

Continuous Cooling Compressor for water refrigerant heat pump

A turbo compressor was developed for water refrigerant heat pumps equipped with continuous cooling compression, in which the vapour is continuously cooled during the compression process by the latent heat of evaporation of the liquid water refrigerant sprayed into the impeller channels. One of the disadvantages of water refrigerant is that the discharge temperature during vapour compression is higher than that of fluorocarbon refrigerant. Multi-stage compression with intercooling are one of the solutions, the system becomes large. In continuous cooling compression, fine particles of water are sprayed from a nozzle embedded inside the impeller, and the water vapour in compression process is directly cooled to the saturation temperature. Therefore, if sufficient amount of spray is present, the compression process follows the saturation line in p-h diagram. Water is supplied to the spray nozzle after pressurized to 10 MPa or more using the centrifugal effect of rotor rotation. A small nozzle was developed that suppresses rotor imbalance and can withstand the load of centrifugal force. A followability index was defined as a reference for the droplets to follow the vapour flow and evaporate before colliding with the blade surface. A water-refrigerant heat pump system was constructed, and the degree of superheat of the discharged vapour was evaluated while changing the spray amount. Increasing the amount of spray decreased the superheat but COP also decreased. Saturated compression was demonstrated above a certain amount of spray, but the impeller flow was choked due to the droplet evaporation. It is desirable to assume a sufficient choke margin, or to develop a special CFD code that can take into account the droplet evaporation.

Plume Stability During Direct Contact Condensation of Steam in a Crossflow of Subcooled Water, at High Mass Flux and With a Small Nozzle Diameter

Abstract The stability of a steam plume during direct-contact condensation into a crossflow of subcooled water is investigated for mass fluxes that are higher (>600 kg/m2s) and a nozzle diameter (2.4 mm) that is smaller than typically seen in the literature. The transition from a stable steam plume to an unstable plume associated with the formation and collapse of steam bubbles is characterized by high-speed imaging and high-frequency pressure measurements. Four regimes are observed: stable, condensation oscillation, transition, and unstable. A regime map and spectral signatures of the different flow regimes are provided. Results are compared with correlations from the literature, which are typically derived for lower mass fluxes, larger nozzles, and injection into stagnant pools of water.

Behaviors of discharge coefficients of small diameter critical nozzles

The discharge coefficients of 59 small diameter toroidal throat Venturi critical nozzles were measured by the static gravimetric method. The throat diameter is from 0.014 mm to 2.35 mm and the Reynolds number is 4 × 102 to 2 × 105. These nozzles were manufactured by the normally processing method base on the same design drawing, but their discharge coefficients were scattered widely. The purpose of this paper is to explain the behavior of discharge coefficient scattered. In the correction procedure used here, while comparing the discharge coefficient obtained experimentally and the reference theoretical model, the throat diameter is corrected and the optimal radius of curvature of nozzle inlet is determined so that both discharge coefficients match. Resultantly, most of the behaviors of the discharge coefficient of 59 critical nozzles could be explained well.

Antimicrobial properties of viscose yarns ring-spun with integrated amino-functionalized nanocellulose

Bio-based, renewable and biodegradable products with multifunctional properties are also becoming basic trends in the textile sector. In this frame, cellulose nanofibrils (CNFs) have been surface modified with hexamethylenediamine/HMDA and used as an antimicrobial additive to a ring-spun viscose yarn. The CNF-HMDA suspension was first characterized in relation to its skin irritation potential, antimicrobial properties, and technical performance (dispersability and suspensability in different media) to optimize its sprayability on a viscose fiber sliver with the lowest sticking, thus to enable its spinning without flowing and tearing problems. The impact of CNF-HMDA content has been examined on the yarn`s fineness, tensile strength, surface chemistry, wettability and antimicrobial properties. The yarn`s antimicrobial properties were increasing with the content of CNF-HMDA, given a 99% reduction for S. aureus and C. albicans (log 1.6–2.1) in up to 3 h of exposure at minimum 33 mg/g, and for E. coli (log 0.69–2.95) at 100 mg/g of its addition, yielding 45–21% of bactericidal efficacy. Such an effect is related to homogeneously distributed CNF-HMDA when sprayed from a fast-evaporated bi-polar medium and using small (0.4 mm) nozzle opennings, thus giving a high positive charge (0.663 mmol/g) without affecting the yarn`s tenacity and fineness, but improving its wettability. However, a non-ionic surfactant being used in the durability testing of functionalized yarn to 10-washing cycles, adheres onto it hydrophobically via the methylene chain of the HMDA, thus blocking its amino groups, and, as such, decreasing its antibacterial efficiency, which was slightly affected in the case when the washing was carried out without using it.

Universal Programmable Portable Measurement Device for Diagnostics and Monitoring of Industrial Fluid Power Systems.

This paper presents a new universal programmable portable measuring device (PMD) as a complete, accurate, and efficient solution for monitoring and technical diagnostics of industrial fluid power systems. PMD has programmable functions designed for recording, processing, and graphical visualization of measurement results at the test stand or the place of operation of fluid power systems. PMD has a built-in WiFi communication module for transferring measurement data via Industrial Internet of Things (IIoT) technology for online remote monitoring of fluid power systems. PMD can be programmed for a variety of measuring tasks in servicing, repairing, diagnosing, and monitoring fluid power systems. For this purpose, the fluid dynamic quantity, mechanical quantity, and electrical quantity can be measured. The adjustment of the PMD to the indirect measurement of leakage flow rate in a compressed air system (CAS) is presented in detail. Measuring instruments and PMDs were connected to a branch of the pipeline. The tests used the measurement system to estimate the leakage flow rate through air small nozzles, as well as other CAS indicators.

Effect of Process Conditions and Colloidal Properties of Cellulose Nanocrystals Suspensions on the Production of Hydrogel Beads.

The influence of the physical, rheological, and process parameters on the cellulose nanocrystal (CNC) drops before and after external gelation in a CaCl2 solution was investigated. The dominant role of the CNC’s colloidal suspension properties, such as the viscous force, inertial, and surface tension forces in the fluid dynamics was quantitatively evaluated in the formation of drops and jellified beads. The similarity and difference between the behavior of carbohydrate polymers and rod-like crystallites such as CNC were enlightened. Pump-driven and centrifugally-driven external gelation approaches were followed to obtain CNC hydrogel beads with tunable size and regular shape. A superior morphological control—that is, a more regular shape and smaller dimension of the beads—were obtained by centrifugal force-driven gelation. These results suggest that even by using a simple set-up and a low-speed centrifuge device, the extrusion of a colloidal solution through a small nozzle under a centrifugal field is an efficient approach for the production of CNC hydrogel beads with good reproducibility, control over the bead morphology and size monodispersion.

Single step nanospray drying preparation technique of gabapentin-loaded nanoparticles-mediated brain delivery for effective treatment of PTZ-induced seizures

In the present study, gabapentin (GBP)-loaded chitosan nanosized particles were fabricated applying the nanospray drying technique. Different preparation parameters (spray mesh diameter, chitosan concentration and presence of D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) were studied while fixing other parameters (spraying rate, inlet temperature and gas flow rate). An optimized formulation with a particle size 107 ± 13 nm was obtained upon spraying 0.1% (w/v) chitosan solution containing 0.05% (w/v) of TPGS utilizing the small nozzle (4 μm spray mesh hole size). Drug entrapment efficiency and yield were as high as 95% and 83%, respectively. A 98.1 ± 6.1% (w/w) cumulative drug release was recorded after 2 h. Confocal laser scanning microscopy showed higher fluorescent dye penetration into brain tissue following intranasal administration of Rhodamine B labeled spray dried chitosan nanoparticles (NPs) as compared to Rhodamine B solution. Pentylenetetrazole (PTZ) was used to induce convulsions in rats through elevating seizure stages, releasing neuroinflammatory mediators and reducing excitatory amino acid transporter 2 (EAAT 2) and γ-aminobutyric acid (GABA) brain contents. Nanospray dried GBP-loaded chitosan NPs reduced seizure score, neuroinflammation; TNF-α and TGF-β, elevated EAAT 2 and GABA as well as decreased degeneration in pyramidal neurons compared to marketed product Conventin® capsules. Thus, it can be concluded from the aforementioned data that nanospray dried GBP-loaded chitosan NPs could comprise an appropriate treatment of epilepsy.

Influence of Nozzle Shape on Partial Oxidation Reforming of Biogas Using Microwave Plasma

Biogas, composed of ∼60% CH4 and ∼40% CO2, is a carbon-neutral fuel but suffers from low flame stability. Thus, for effective utilization, the combustion reaction must be enhanced or biogas must be upgraded. Herein, microwave plasma-assisted combustion was utilized for partial oxidation reforming of biogas to enhance the reforming reaction and to upgrade biogas. The characteristics of the biogas reforming process and effects of the nozzle shape were investigated using four different nozzles. The small thin nozzle suppressed microwave attenuation to the greatest extent and thus most effectively promoted the reforming reaction. Microwave plasma not only reformed CH4 into H2 and CO but also decomposed CO2 (which does not have any calorific value) into CO (which has calorific value); thus, the maximum cold gas efficiency achieved with the small thin nozzle was 112.7%, and the biogas was upgraded. Biogas reforming using O2 as an oxidizer was also evaluated to improve the cold gas efficiency, but the cold gas efficiency undesirably decreased in this reaction relative to that using air with N2 as the oxidizer because the reforming reactions are enhanced by increasing the active radicals like H and OH in the latter.

A quantitative analysis of two cementing techniques in total elbow replacement: A cadaveric study.

One of the reasons for failure of total elbow replacement is loosening of the ulnar component. Cementing techniques are often outdated. A special small nozzle is needed for the ulnar component, when a cement gun is used. This may not always be available, or surgeons may prefer to use a syringe. We postulated that the use of a cement gun and smaller nozzle would result in improved filling of the ulnar canal. A cadaveric study was performed in which the ulnas of paired specimens were cemented with a cement gun or with a syringe. A 3D printed ulnar component was inserted and computed tomography scanning was performed on all specimens. Filling of the ulnar intramedullary canal was analysed using 3D reconstructions of the specimens. A greater degree of filling was seen by the use of the cement gun in 85.7%. Filling was 52.7% in the syringe group (25.1-78.7%), compared to 63.3% for the cement gun group (p < 0.05). The use of a small nozzle cement gun provided a significantly higher filling degree of the ulnar canal. We recommend to always use a cement gun with a specific small nozzle to cement the ulnar component in total elbow arthroplasty.