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Abstract Existing ice particle jet surface treatment technology is prone to ice particle adhesion during application, significantly affecting surface treatment efficiency. Based on the basic structure of the jet pump, the ice particle air jet surface treatment technology is proposed for the instant preparation and utilization of ice particles, solving the problem of ice particle adhesion and clogging. To achieve efficient utilization of ice particles and high-speed jetting, an integrated jet structure for ice particle ejection and acceleration was developed. The influence of the working nozzle position (L d), expansion ratio (n), and acceleration nozzle diameter ratio (D n) length-to-diameter ratio (L n) on the ice particle ejection and acceleration was systematically studied. The structural parameters of the ejector were determined using the impact kinetic energy of ice particles as the comprehensive evaluation index, and the surface treatment test was conducted to verify the results. The study shows that under 2 MPa air pressure, the ejector nozzle parameters of n = 1.5, D n = 4.0, L d = 4, and L n = 0 mm can effectively eject and accelerate the ice particles. The aluminum alloy plate depainting test obtained a larger paint removal radius and resulted in a smoother aluminum alloy plate surface, reducing the surface roughness from 3.194 ± 0.489 μm to 1.156 ± 0.136 μm. The immediate preparation and utilization of ice particles solved the problems of adhesion and storage in the engineering application of ice particle air jet technology, providing a feasible technical method in the field of material surface treatment.

This current work evaluates the efficacy of a co-flow nozzle for cold spray applications with the aim of mitigating nozzle clogging issues, which can occur during long-duration operations, by replacing the solid wall of a divergent nozzle section with an annular co-flow fluid boundary. Simulations were conducted on high-pressure nitrogen flowing through convergent–divergent (C–D) axisymmetric nozzles, with a stagnation pressure of 6 MPa and a stagnation temperature of 1273 K. In these simulations, Inconel 718 particles of varying sizes (15 µm to 35 µm) were modeled using a 2-way Lagrangian technique, and the model's accuracy was confirmed through validation against experimental results. An annular co-flow nozzle with a circular cross section and straight passage covering the primary C–D nozzle has been designed and modeled for cold spray application. Co-flow was introduced to the reduced nozzle length to compensate for particle velocity loss at higher operating conditions. It was found that co-flow facilitates momentum preservation for primary flow by providing an annular gas boundary, resulting in increased particle speed for a longer axial distance beyond the nozzle exit of the reduced divergent length nozzle. The particle acceleration performance of the reduced divergent section nozzle, when combined with co-flow, is comparable to the original length nozzle. [ABSTRACT FROM AUTHOR]

Minimum quantity lubrication (MQL) has achieved excellent results in precision machining. The geometric parameters of the nozzle play a crucial role in determining the performance of MQL. In this study, the orthogonal experimental method was employed to improve and optimize the performance of MQL. Computational fluid dynamics (CFD) simulation using ANSYS Fluent software was conducted, and the simulation data were statistically analyzed. The effects of six influencing factors, namely, the width of the gas-phase narrow flow region, the taper, the output tube length, the length of the gas-phase narrow flow region, the output aperture, and the pressure, on the performance of MQL were investigated. The results revealed that the order of importance for the six influencing factors differed depending on the evaluation criteria used. The parameter that had the greatest impact on the composite index was the absolute gas velocity at a distance of 0.1 m from the outlet. The optimum combination of geometric parameters for the nozzle was an output aperture of 2 mm, a taper of 40°, a length of the gas-phase narrow flow region of 1.5 mm, a width of the gas-phase narrow flow region of 0.3 mm, an output tube length of 15.5 mm, and a pressure of 5 bar. [ABSTRACT FROM AUTHOR]

The nozzle is the key component of water mist fire extinguishing system. As a response to the problems of small injection angle associated with straight jet nozzles and the weak axial momentum of swirl nozzles, a swirling–straight composite nozzle is designed in this work. The comparison with a straight jet nozzle and a pressure swirl nozzle shows that the swirling–straight composite nozzle has a larger axial momentum and better injection angle. Under the same pressure, the volume flow of the swirling–straight composite nozzle is more than 27% of the pressure swirl nozzle, and the injection angle was more than 65% of straight jet nozzle. The numerical model of the swirling–straight composite nozzle is established. Meantime, the internal flow field characteristics and the influence of the straight jet aperture on the performance are studied. The results demonstrate that the straight jet fluid and swirling fluid can be mixed well in the nozzle, and a larger axial momentum and tangential momentum can be obtained. With the increase of the straight jet aperture, the swirl effect in the nozzle becomes weaker, the injection angle becomes smaller, and the axial momentum improves. When the straight jet aperture increases from 1.1 to 1.9 mm, the straight jet volume flow at the nozzle inlet increases by 127%, and the injection angle reduces by 40%. [ABSTRACT FROM AUTHOR]

Spray drying of oil-in-water emulsions is a widespread encapsulation technique. The oil droplet size (ODS) significantly impacts encapsulation efficiency and other powder properties. The ODS is commonly set to a specific value during homogenization, assuming that it remains unchanged throughout the process, which is often inaccurate. This study investigated the impact of atomizer geometry and nozzle dimensions on oil droplet breakup during atomization using pressure-swirl atomizers. Subject of the investigation were nozzles that differ in the way the liquid is set in motion, as well as different inlet port and outlet orifice dimensions. The results indicate that nozzle inlet port area may have a significant impact on oil droplet breakup, with x90,3 values of the oil droplet size distribution decreasing from 5.29 to 2.30 µm with a decrease of the inlet area from 2.0 to 0.6 mm. Good scalability of the findings from pilot to industrial-scale was shown using larger nozzles. A simplified theoretical model, aiming to predict the ODS as a function of calculated shear rates, showed reasonable agreement to the experimental data for different atomization pressures with coefficients of determination of up to 0.99. However, it was not able to predict the impact of different nozzle dimensions, most likely due to changes in flow characteristics. These results suggest that the stress history of the oil droplets might have a larger influence than expected. Further studies will need to consider other zones of high stress in addition to the outlet orifice. [ABSTRACT FROM AUTHOR]

Shotcrete finds extensive applications in civil engineering, from repair and rehabilitation to new constructions. Nevertheless, shotcrete construction frequently suffers from placement issues, such as rebound and overshooting. These challenges can result in reduced operational efficiency, increased material wastage, diminished construction quality, and potential workplace hazards. It is worth noting that these placement issues are intrinsically linked to the spray characteristics of shotcrete. These characteristics are contingent upon various factors, including the material's flowability and viscosity, as well as the nozzle geometry. This research experimentally characterized the spray behavior of wet-mix shotcrete. High-speed cameras and image analysis techniques were utilized to capture and characterize wet-mix shotcrete on a full-scale spraying setup. The study experimentally determined the key placement performance parameters such as placement, rebound, and final build-up thickness and correlates the placement performance of shotcrete with the spray characteristics. The findings reveal that wider spray opening angles, smaller droplet sizes, and higher velocities contribute to improved material deposition, reduced rebound, and increased build-up thickness. The study also assesses the impact of nozzle geometry and rheology of the shotcrete mixture. Increased flowability led to slightly better spray behavior and placement. Higher material viscosity produced a more consistent spray which enhanced shotcrete performance. Multi-air jet guns, where compressed air directly contacts droplets, can enhance shotcrete spray efficiency.

Recently, the low-pressure cold spray (LPCS) technique has been used to fabricate superhydrophobic polymer coatings on metallic substrates, suggesting a significant potential in engineering applications. This study aims to design a spiral LPCS nozzle to coat the pipe's inner wall with superhydrophobic polymer. The design goal is to achieve the maximum particle velocity in a confined (limited) space, assuming that the powder can enter the feeding tube through the Venturi effect. Achieving these two goals simultaneously using only computational fluid dynamics (CFD) simulation is challenging. Therefore, the CFD simulation was combined with the neural network (NN) method to design the new spiral nozzle. During training, the effects of the NN models and algorithms were investigated. The results showed that the feedforwardnet model combined with the trainbr or trainlm algorithm (from MATLAB 2016b software), presented a minimal error for particle velocity or gas flux prediction, respectively. The trained NN correlates the nozzle parameters (i.e., mean coil diameter, spring lift angle, and expansion ratio) and its performances (i.e., particle velocity and gas flux in the powder feeding tube). As a result, the optimal spiral nozzle was determined based on the design goal of maximum particle velocity and suitable gas flux in the powder feeding tube. Furthermore, the effect of each nozzle parameter on the particle velocity and gas flux in the powder feeding tube was analyzed. The cold spray experiment confirmed that the designed spiral nozzle could fabricate Perfluoroalkoxy alkane (PFA) coatings. [ABSTRACT FROM AUTHOR]

Even though shape optimization is a powerful tool for designing aerospace vehicles, it can be time-consuming when high-fidelity models are employed. Thus, lower-fidelity simulations covering a wider design space can be a solution for shape optimization in the early design phases. With this in mind, the present work aims to develop a low-fidelity and fast method to conduct nozzle shape optimization. This method consists in using the free-form deformation (FFD) parameterization technique to control the nozzle shape by means of an optimization algorithm to maximize the coefficient of thrust determined by a two-dimensional method of characteristics (MoC). To verify the reliability of the proposed method, a similar optimization process is carried out, recurring to high-fidelity simulations, namely using an Euler solver, in the open-source framework SU 2 . This latter optimization process is established as a surrogate-based optimization (SBO) not only to mitigate the SU 2 framework limitations in performing shape optimization on nozzles, but also as a way to reduce the computational power. A good agreement between the results from both methods is achieved, displaying solely a small offset concerning the optimal contour width and the coefficient of thrust. Hence, this proves the usefulness of the developed shape optimization strategy based on the MoC for the preliminary design of nozzles. [ABSTRACT FROM AUTHOR]

Spray drying of oil-in-water emulsions is a widespread encapsulation technique. The oil droplet size (ODS) significantly impacts encapsulation efficiency and other powder properties. The ODS is commonly set to a specific value during homogenization, assuming that it remains unchanged throughout the process, which is often inaccurate. This study investigated the impact of atomizer geometry and nozzle dimensions on oil droplet breakup during atomization using pressure-swirl atomizers. Subject of the investigation were nozzles that differ in the way the liquid is set in motion, as well as different inlet port and outlet orifice dimensions. The results indicate that nozzle inlet port area may have a significant impact on oil droplet breakup, with x90,3 values of the oil droplet size distribution decreasing from 5.29 to 2.30 µm with a decrease of the inlet area from 2.0 to 0.6 mm. Good scalability of the findings from pilot to industrial-scale was shown using larger nozzles. A simplified theoretical model, aiming to predict the ODS as a function of calculated shear rates, showed reasonable agreement to the experimental data for different atomization pressures with coefficients of determination of up to 0.99. However, it was not able to predict the impact of different nozzle dimensions, most likely due to changes in flow characteristics. These results suggest that the stress history of the oil droplets might have a larger influence than expected. Further studies will need to consider other zones of high stress in addition to the outlet orifice.

• Model for the analysis and design of CO 2 two-phase nozzles. • Statistical analysis of critical mass flow values. • Nozzle design for heat pump application. The pressing needs to increase efficiency in heat pumps require refined design of various system components. In common reverse cycles, the throttling valve performs pure energy dissipation, and therefore it is well suited to be replaced by technologies such as ejectors and turbines, to augment system performance. In both two-phase turbines and two-phase ejectors a supersonic convergent-divergent nozzle is commonly required, which is responsible for accelerating the refrigerant fluid from the high-pressure part (e.g. condenser) to the low pressure part (e.g. evaporator). In the design phase of these nozzles, the accurate prediction of the maximum mass flow rate, also known as the critical mass flow rate, is particularly complex due to the two-phase nature of the expansion. In this paper, a new statistical approach to determine the value of the critical mass flow rate for CO 2 , as refrigerant fluid, is presented and assessed. This approach is based on the MF (Massflow Factor) parameter, which well correlates the value of mass flow rate in sonic conditions. The relationship shown here is based on open experimental information and it is validated on data from the open literature and the industry. The relative error on critical flow rate is less than 15% in the validation range, placing this statistical approach at a level of accuracy comparable to other physical models. An example of design is provided in this paper to demonstrate the potential of the relationship found. This approach provides the designer with a straightforward and validated basis for a reliable preliminary design of expanding two-phase nozzles. [ABSTRACT FROM AUTHOR]

Additive Manufacturing with Continuous Fibers (AM-CFRP) results in products with high strength/stiffness at low mass. As such the process holds great promise to be part of obtaining goals in fuel economy for automobiles and aircrafts. AM is able to create products with highly complex 3D geometries, not possible with other production processes. However, there are still many drawbacks to AM process variants with continuous fibers like shape limitations and high void content and low delamination resistance in the printed product. At the University of Twente research has been dedicated on using commingled yarns as a feedstock for AM-CFRP. Before using the yarn, pultrusion is used to transform it to a consolidated filament, which allows for using a FDM-type deposition setup in the AM-CFRP process. The resulting filaments thermal and mechanical properties differ from standard AM-CFRP feedstock, affecting process settings and deposition results. This paper describes the research on the interaction between feedstock, nozzle design and print settings on microstructure, mechanical performance and dimensional stability of extruded feedstock and printed products. It is shown that nozzle designs developed for thermoplastic materials function suboptimal and that the nozzles to be designed should be conceptually different regarding shaping, heating and depositing the filament. [ABSTRACT FROM AUTHOR]

• The SSSL nozzle profile is optimized with axial and lateral forces as targets. • The influence of design parameters on performance is investigated in detail. • The three-dimensional shock wave dominates the distribution of wall pressure. • The thrust vector angle of SSSL nozzle is over 16° when the swing angle is 10°. • We present an elliptic function to predict the thrust vector performance. The supersonic split line (SSSL) nozzle is one of the thrust vector nozzles. Because of the complex internal flow, designing a high-performance SSSL nozzle, especially with a large swing angle, could be quite challenging. In the present study, an SSSL nozzle design procedure is presented first. The multi-objective optimization method is utilized to determine the nozzle configurations that provide the best thrust vector performance. The influence of key geometric parameters on the nozzle thrust performance is uncovered. By monitoring the nozzle internal flow during the multi-objective optimization procedure, the significant roles played by shock waves on the nozzle thrust performance are demonstrated. The results show that the split line structure causes a total thrust loss of 1.5% at 0° swing angle, and the small round chamfers and split line gap width are helpful to avoid more losses. The detailed flow pattern analysis shows that it is very important to ensure the main oblique shock to not touch the concave side of the nozzle wall to maintain the high thrust performance. The expansion ratio at the split line and the position of swing center are essential design variables in SSSL nozzle designs. Finally, a mathematical model is proposed to predict the thrust vector performance of the SSSL nozzles based on the resultant optimized nozzle configurations. [ABSTRACT FROM AUTHOR]

Electrospinning is an easy and efficient method for preparing nanofibers on laboratory and industrial scales. In recent years, various studies have been done with special attentions to specific structures, increasing the application and eliminating the shortcomings of previous methods. Janus structure is one of the new and widely used structures that due to the limitations and challenges in achieving this structure, such as nozzle design, phase separation of two polymer solutions during electrospinning, flow rate control, optimal voltage and other parameters, the published reports in this field, are limited. Side-by-side electrospinning is one of the common ways to achieve this special structure. In this method, with appropriate nozzle design, two polymer solutions can be electrospun simultaneously. In addition, the nozzle design and the related parameters such as needle diameter, angle, and distance between the nozzles are of special importance. Also, parameters related to the rheological behavior of the polymer, especially viscosity, are crucial in achieving this particular structure. In this paper, the methods of preparation of Janus nanofibers by side-by-side electrospinning method, new structures based on these nanofibers, including the study of structure and production methods through side-by-side electrospinning, are briefly reviewed.

This study proposes a space-marching nozzle design method based on a modified CCW relation and an auxiliary secondary injection technique for the shock-focusing detonation engine initially filled with the stoichiometric hydrogen/air mixture to improve the total impulse. First, a parametric analysis of the contraction and expansion ratios is carried out to demonstrate the positive contributions of the diverging walls to the total impulse. With the expansion ratio ε increasing from 1.5 to 2.5, the total impulses of the nozzle configurations with contraction ratios ε' = 1.11, 1.25, and 1.43 increase by 13.44%, 21.28%, and 22.82%, respectively. The combination of ε' = 1.11 and ε = 2.5 (nozzle CD9) corresponds to the maximum total impulse of 0.5754 N s and the relatively large specific impulse of 4963.9s in a single cycle of 350 μs. Second, a characteristic form of the detonation shock dynamics (DSD) is then utilized to design the diverging profile of the nozzle, further enlarging the expansion ratio and modifying the straight wall into a curved one. It can be observed that the DSD profile roughly has a 70.29% higher peak thrust, a 29.5% higher total impulse, and an 8.61% higher specific impulse than nozzle CD9. Third, an optimal distance between the primary and secondary injection slots (Δx = 10.0 mm) is introduced to improve thrust, where the total impulse and specific impulse in a single cycle reach 0.7855 N s and 5693.0s. Fourth, the inlet flow parameters are adjusted to trigger a multi-cycle operation. A combination of p t,inj = 0.45 MPa, T t,inj = 300 K, and Ma inj = 1.5 can guarantee a time-averaged total thrust of 767.3 N, a specific impulse of 5066.3s, and a dominant frequency of 3233 Hz. These results reveal the reliability of the proposed design procedure for SFDE nozzles. • The shock-focusing detonation engine has a higher operating frequency than the traditional pulse detonation engine. • The diverging section of the nozzle contributes positively to the thrust, and the converging section generates drags. • The detonation shock dynamics is used to ensure perpendicularity of the detonation foot to the diverging nozzle wall. • The secondary injection induces a recirculation zone in the diverging nozzle wall, creating a pressure plateau. • The multi-cycle operation needs a high total pressure, a low total temperature, and a large injection Mach number. [ABSTRACT FROM AUTHOR]

ABSTRACT In El Oued, southern Algeria, the traditional Mini-Centre Pivot System (MCPS) is widely used for the irrigation of agricultural crops, and its use has been growing continuously. However, these systems have a constant nozzle diameter along the lateral pipe, which affects productivity directly, besides decreasing both the quantity and quality of agricultural products by irrigation heterogeneity. Therefore, optimising the design of the MCPS nozzles is linked strongly to the desired uniform irrigation. This study aims to determine the optimal configuration of nozzles for high irrigation uniformity. To achieve this goal, a genetic algorithm was used for maximising the uniformity of MCPS-mediated irrigation. The optimisation is carried out according to water distribution modelling, calculation of the Heermann and Hein uniformity coefficient (CUH), and existing nozzle diameters. To verify the accuracy of the proposed model, three existing MCPS (60 m, 50 m, and 46 m in length) are investigated experimentally. The developed code findings in terms of CUH are in agreement with those obtained by experimental tests. The analysis indicated that the nozzle diameter should vary from 5 to 15 mm along the lateral pipe. In these optimal conditions, the CUH was improved by 29.77%, 33.99%, and 19.36%, respectively, for the existing 60, 50, and 46 m irrigation systems. The most obvious findings to emerge from this study is that using a genetic algorithm to optimise the design based on the nozzle size improves water application uniformity by more than 19% in terms of the CUH.

Analytical simulation is a powerful tool for the optimization of the convective drying of continuous thin film coatings. Knowledge of the heat transfer coefficient is a prerequisite for applying such simulations. In this work, the heat transfer coefficient distributions in industrial dryers with oblique twin nozzles is investigated. Convergent nozzles show higher heat transfer than divergent nozzles. The results are used as boundary condition for a dryer simulation, which is in good agreement with experimental data. An alternative nozzle design, using a wider outlet area and a lower velocity is also investigated. A more homogeneous local Nusselt number is observed. [ABSTRACT FROM AUTHOR]

Laser-based Direct Energy Deposition (L-DED) is one of the most commonly employed metal additive manufacturing technologies. In L-DED, a laser beam is employed as a heat source to melt the metal powder that is deposited on a substrate layer by layer for the generation of a desired component. The powder is commonly fed through a nozzle into the molten pool by means of a carrier gas and therefore, a nozzle design that ensures optimal deposition of the material is of critical importance. Additionally, its design also affects the powder and gas flows that arise in the nozzle and during the deposition. This, in turn will affect the characteristics of the generated clad and the performance of the whole deposition. Therefore, an optimization of deposition nozzle geometry can be as important as the controlling of deposition process parameters in order to obtain best component qualities. In this context, the present review work is aimed at analysing the different nozzle designs employed in powder-based L-DED processes and the influence of different geometrical features and configurations on the resulting powder and gas flows. Concretely, the main characteristics of each design, their advantages and their possible shortcomings are analysed in detail. Additionally, a review of most relevant numerical models employed during the development of new and optimised nozzle designs are also addressed. [ABSTRACT FROM AUTHOR]

Jet-Electrochemical machining (Jet-ECM) is a novel variation of traditional electrochemical machining in which electrically conductive material is removed through anodic dissolution by means of a fine jet of electrolyte. In this study, the effect of nozzle geometry on material removal characteristics are investigated through physical experiments performed on a Jet-ECM system under development at the university of Manchester. A total of 8 nozzles with holes encompassing converging, diverging and rounded features are studied at flow rates between 0.125 and 0.225 l/min. The results show that the nozzle hole geometry has a significant effect on the machined profile produced due to variations in flow velocity, pressure, and electric current distribution with converging hole nozzles providing an increased depth of cut than the symmetrical cylindrical channel by up to 9.7%. A 2D Star CCM+ simulation is also proposed, and numerical results developed and compared with experimental ones to investigate the feasibility of using simulation to develop future nozzle designs. The simulated results show good profile comparison to the experimental results, however, the model needs developing to improve the process repeatability for future use in nozzle design. [ABSTRACT FROM AUTHOR]

The flow characteristics and postcombustion behavior of a single‐flow postcombustion (PC) oxygen lance are of paramount significance to optimal design and operation of the lance but not well understood, and there is also no well‐known design criterion for the optimization of the single‐flow PC lance. Herein, the design criteria of a single‐flow PC lance are first proposed. Then, a 3D fluid model is established combined with a 120 t top‐blown converter. The influences of the key parameters of secondary nozzles (i.e., inclination angle, diameter, and number) on the jet characteristics and PC behavior at the steelmaking temperature are studied. Finally, based on the design criteria, an optimal PC lance is designed and its smelting effect is compared with that of the conventional lance by industrial tests. The results indicate that the reasonably designed PC lance can effectively improve the PC zone of CO gas and simultaneously increase both the penetration depth and impact area of the main jet. Compared with conventional lance, the PC oxygen lance can raise the temperature of molten steel by ≈30 °C and reduce the total fe (T.Fe) content in the final slag by 0.86%. Moreover, it has almost no effect on the gas recovery. [ABSTRACT FROM AUTHOR]

Abstract Production is hampered by sand and scale that impede flow and require intervention. Although coiled tubing jetting tools have been very successful in wellbore cleaning operations, the coiled tubing unit has certain limitations and constraints. The fluid pumping pressures of fluids at the wellhead are limited to the normal pressure of pump, whereas some sand types and scales require a very high shear force to break and disintegrate. The dimensions of the coiled tubing unit nozzle size are directly related to the diameter of the production tubing. The present work consists in designing the nozzle of coiled tubing jetting tool with different dimensional parameters and analysing the design of the nozzle for required high outlet pressure, flow rate and velocity at various inlet pressures. Numerical technique was used to analyse the flow of fluid through the nozzle. The different port diameters and cone angles between 0.09 and 0.125 inch and 15° and 45°, respectively, were simulated. The effects of these parameters on the outlet pressure, the mass flow at the outlet and the outlet velocities were predicted and analysed. Inner nozzle diameters smaller than 0.75 inch gave good results, and the 1 inch inner diameter gave lower performance. Therefore, the lower diameter nozzle provides better performance. Decreasing the number of ports from seven to five did not create a big difference in nozzle performance, as the seven ported nozzles provide slightly better performance.

In this paper an industrially established 1D model for two-phase nozzles design and analysis (Elliott, 1968) has been extended and validated with a wider range of experimental data, focusing on single component two-phase fluid expansion from initial quality in the 0%–25% range. The Authors focused on the correlations of the gas-liquid slip velocity and wall friction for two-flow regimes. The upgraded model has been tested on a converging nozzle showing accurate results under subcritical conditions (Ma<1). Furthermore, simulations have also been carried out on a convergent-divergent nozzle, concentrating on the diverging part at Ma>1, demonstrating that the new model obtained a significant reduction in error compared to the original Elliott model and to the well-known isentropic homogeneous approach (IHE). The extended model was also tested on a convergent-divergent nozzle produced by Carrier Corporation for the 19-XRT chiller, obtaining a satisfactory performance prediction. The validation process allowed to assess the limits of validity of the new model, which can be effectively used as design tool for subsonic or supersonic two-phase nozzles. In particular, the model capability to identify critical mass flow and critical expansion ratio has been investigated, showing good match for the critical expansion ratio, while margins of improvement remain for the critical mass flow prediction. [ABSTRACT FROM AUTHOR]

During cold spray, the temperature of the particle carrier gas is at room temperature, which is lower than the preheated propulsive gas and affects the mixed gas temperature and particle acceleration. This study is investigating the associated effect of the powder carrier gas and powder characteristics on the optimal design of the nozzle using numerical simulations. The results show that the heat exchange of mixed gas stabilizes, and temperatures of mixed gas and particles are higher in the nozzle when a larger inlet diameter and a longer convergent section are used. In addition, particle impact velocity is inversely related to its size and density. Therefore, heavier particles require longer divergent lengths and larger expansion ratios for a longer acceleration distance and increased kinetic energy. The nozzle geometry can be designed depending on the selected particles and the chosen propulsive gas, for a maximum particle impact velocity. [ABSTRACT FROM AUTHOR]

Additive manufacturing of metals has become a leading technology for function-integrated and individualized components. Ongoing research leverages this technology from single-material parts to gradient compositions and multi-material combinations. Powder-based laser metal deposition is the preferred process for these novel applications because of the ability to add onto freeform surfaces and flexible material use. A crucial aspect of this powder-based process is material loss due to overspray. Furthermore, the shape and size of the powder stream must be altered depending on the intended use. For example, thin walls and fine details require a narrow powder focus whereas a larger focus can accelerate the manufacturing of volumes substantially. To address this challenge, novel 3D printable and replaceable nozzles are developed. Compared to common nozzle designs, this new approach enables quick changing of different sized nozzles and incorporates additively manufactured flow paths. Finally, the stream quality is visualized by Schlieren photography. [ABSTRACT FROM AUTHOR]

Cryogen spray cooling is used to prevent epidermal thermal damage during port-wine stain laser therapy, despite the limited understanding of the fluid dynamics, thermodynamics, and heat transfer characteristics of cryogen sprays. In recent studies, it has been suggested that the heat flux through human skin could be increased by changing physical parameters such as nozzle-to-skin distance, nozzle diameter, and/or by depositing cryogen in sequential spurts. These changes affect spray parameters such as droplet diameter, velocity, and spray temperature. Therefore, in order to optimize new nozzle designs, it is necessary to explore the influence that these fundamental spray parameters have on heat extraction. In this paper, various valve/nozzle configurations were characterized. A Phase Doppler Particle Analyzer was used to determine the average diameter, velocity, and droplet concentration of various cryogen sprays. The mass flux delivered by each valve/nozzle configuration was also measured, along with the average spray temperature. A custom-made device consisting of an insulated metallic disk was used to measure the heat extracted by different sprays. The results showed that there are significant differences in the heat extracted by the different valve/nozzle configurations. These variations are proportionally influenced by mass fluxes. Strong correlations were also observed between average droplet velocities and heat extraction. These findings indicate that mass flux has a dominant effect on heat extraction from human skin during cryogen spray cooling. It is also apparent that kinetic and thermal energies are other parameters to be considered when optimizing heat extraction.

Cryogen spray cooling is used to prevent epidermal thermal damage during port-wine stain laser therapy, despite the limited understanding of the fluid dynamics, thermodynamics, and heat transfer characteristics of cryogen sprays. In recent studies, it has been suggested that the heat flux through human skin could be increased by changing physical parameters such as nozzle-to-skin distance, nozzle diameter, and/or by depositing cryogen in sequential spurts. These changes affect spray parameters such as droplet diameter, velocity, and spray temperature. Therefore, in order to optimize new nozzle designs, it is necessary to explore the influence that these fundamental spray parameters have on heat extraction. In this paper, various valve/nozzle configurations were characterized. A Phase Doppler Particle Analyzer was used to determine the average diameter, velocity, and droplet concentration of various cryogen sprays. The mass flux delivered by each valve/nozzle configuration was also measured, along with the average spray temperature. A custom-made device consisting of an insulated metallic disk was used to measure the heat extracted by different sprays. The results showed that there are significant differences in the heat extracted by the different valve/nozzle configurations. These variations are proportionally influenced by mass fluxes. Strong correlations were also observed between average droplet velocities and heat extraction. These findings indicate that mass flux has a dominant effect on heat extraction from human skin during cryogen spray cooling. It is also apparent that kinetic and thermal energies are other parameters to be considered when optimizing heat extraction.

Inkjet technology is an essential tool for precise and quick delivery of liquids in micro-droplets. A key topic of the technology is to deliver the droplets efficiently by designing the nozzle that is related to the droplet speed and the droplet volume in a stable inkjet process. The ejected droplets are usually too small to determine their physical states through onsite measurement. Complex physical phenomena, such as the coupling effects of surface tension, viscous force and inertial force, make it difficult to optimize the nozzle design by experiments alone. In the paper, we adopt computational fluid dynamics to investigate the inkjet process with the orthogonal test method to arrange the studied cases. The computational results firstly have been verified through measuring a simulated case that could be observed in the experiment. Different nozzle structures then have been examined by numerical simulation. It is found that the Laval-shaped nozzle can improve the droplet speed significantly to deliver the droplets fast, and that the curvilinear-triangle-shaped nozzle can minimize the droplet volume to improve the printing accuracy. It is further revealed that a large ink viscosity and surface tension, as well as a low ink density can improve the process stability. Additionally, a parameter combined by the droplet speed, the droplet volume and the stability level is proposed to evaluate the comprehensive performance of the inkjet nozzle. [ABSTRACT FROM AUTHOR]

Production is hampered by sand and scale that impede flow and require intervention. Although coiled tubing jetting tools have been very successful in wellbore cleaning operations, the coiled tubing unit has certain limitations and constraints. The fluid pumping pressures of fluids at the wellhead are limited to the normal pressure of pump, whereas some sand types and scales require a very high shear force to break and disintegrate. The dimensions of the coiled tubing unit nozzle size are directly related to the diameter of the production tubing. The present work consists in designing the nozzle of coiled tubing jetting tool with different dimensional parameters and analysing the design of the nozzle for required high outlet pressure, flow rate and velocity at various inlet pressures. Numerical technique was used to analyse the flow of fluid through the nozzle. The different port diameters and cone angles between 0.09 and 0.125 inch and 15° and 45°, respectively, were simulated. The effects of these parameters on the outlet pressure, the mass flow at the outlet and the outlet velocities were predicted and analysed. Inner nozzle diameters smaller than 0.75 inch gave good results, and the 1 inch inner diameter gave lower performance. Therefore, the lower diameter nozzle provides better performance. Decreasing the number of ports from seven to five did not create a big difference in nozzle performance, as the seven ported nozzles provide slightly better performance. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the design and performance of the new aeroacoustic wind tunnel facility at the University of Bristol. The purpose of the facility is to enable near- and far-field acoustic and aerodynamic studies on a variety of different aerodynamic components and to examine diverse noise control techniques. The facility comprises a large acoustic chamber, anechoic down to 160 Hz, and a temperature controlled closed-circuit wind tunnel with an open test section. The wind tunnel features two interchangeable rectangular nozzles with a partially shared contraction. Both nozzles are shown to possess a high flow quality with high flow uniformity and low turbulence intensity of 0.09% and 0.12% for the smaller and larger nozzle, respectively. The maximum attainable flow speeds are 40 m/s for the larger nozzle and 120 m/s for the smaller nozzle corresponding to Reynolds numbers of 2.7 million and 8.1 million per meter, respectively. In this paper, we will present various aerodynamic and acoustic results to characterize the performance of the facility. The background noise levels are found to be sufficiently low and the far-field noise measurements from a flat plate, a round cylinder and a NACA 0012 airfoil compare favorably to existing experimental observations. [ABSTRACT FROM AUTHOR]