Effect Of Nozzle Geometry Research Articles

Influence of divergent length on the gas-particle flow in dual hose dry ice blasting nozzle geometry

A numerical simulation study was performed to examine the effect of nozzle geometry and divergent length on gas-particle flows in dual hose dry ice blasting. The simultaneous model of mass momentum and energy exchange between two phases was solved iteratively. The phases are solid dry ice particle and compressible air fluid as a working medium. The results were presented in the gas flow field along the nozzle centerline. The results showed that increasing divergent length decreases the gas-particle density along the centerline; and the density development along the nozzle centerline decreased along the length. Eddy viscosity of the nozzle cavity was steady for length of 0.25 m, but increased drastically for higher values. The substantial increase in eddy viscosity after that position is due to the mixing flow between dry ice pellet and compressed gas which is diverging out from the nozzle outlet area. Thus, the mixing flow experienced back pressure from the atmospheric pressure. The particle mass concentration decreased by increasing nozzle centerline coordinates. The pressure increased along the length; however, it dropped at the end due to the reverse pressure. The temperature increased steadily because of conversion of turbulence to internal thermal energy. The characteristics of gas-particle flow in the nozzle cavity provide better understanding of multiphase flow in turbine and jet engine flow analysis.

The effect of nozzle geometry on the turbulence evolution in an axisymmetric jet flow: A focus on fractals

Multifractal modeling has originated from the study of turbulence to reproduce scale-invariant variations of the energy flux in different scales. Turbulent eddies partition themselves into finer ones in a multiplicative process that produces a population spread over a domain. The population generated is a union of subsets, where each subset is fractal with its own fractal dimension. In this study, we compare the multifractal exponents of jet turbulence intensities obtained through numerical simulation. Turbulence intensities were obtained from numerical jet discharge experiments based on Reynolds-Averaged Navier–Stokes (RANS) equations, where two types of nozzle geometry and two statistical turbulent closure models (i.e., k-ε model and the k-ω model) were tested. The simulation results by two closure models demonstrate in common that the RANS model reproduced hydraulic properties such as transversal velocity profile successfully compared to an analytical solution, but exhibit a limitation for reproducing the turbulence intensity decay in the longitudinal direction. Meanwhile, a common multifractal spectrum turns out to exist for turbulence intensity obtained from numerical simulation based on a statistically-averaged turbulence model. While two different turbulence models produced almost identical transverse velocity profiles, multifractal characteristics are quite distinct; the minimum Lipschitz–Hölder exponent (αmin) and entropy dimension (α1) are dependent on the turbulence as well as outfall nozzle geometry. Consequently, it is demonstrated that the multifractal exponents capture the difference in turbulence structures of hierarchical turbulence intensities produced with different experimental conditions.

Effects of Nozzle Geometries on 3D Printing of Clay Constructs: Quantifying Contour Deviation and Mechanical Properties

In this research, ready-to-print clay was employed to 3D print cylindrical constructs using two different nozzle geometries. The cylinders were printed using a direct ink writing (DIW) 3D printer with similar printing parameters such that the impacts of using different nozzle geometries in contour deviation and mechanical properties of the printed constructs can be quantified. Choosing the right nozzle geometry before printing is critical as it affects the surface finish as well as the mechanical properties of the constructs. This study utilizes point cloud data of the printed samples obtained from a scanning system to measure the contour deviation and surface roughness. According to the results from the point cloud analysis, for cylindrical constructs, circular nozzle imparts less surface roughness and contour deviation whereas square nozzle imparts higher compression strength but with comparatively higher contour deviation and surface roughness. The study provides framework to determine the deviations and mechanical properties of the free form constructs. The work has provided a guideline of nozzle selection in 3D printing of clay constructs for civil infrastructures.

Experimental and Numerical Investigation on Nozzle Exit Shape and Plume for Aft-Boom Mitigation of Supersonic Transport

This paper describes effects of nozzle geometry and a jet plume on the near-field signature and the thrust performance to explore concepts of aft-boom mitigation for future supersonic transport. Numerical analyses of four kinds of convergent-divergent nozzles were conducted to investigate the sensitivity of the near-field signature and the thrust. The results showed that reducing expansion region at the boat-tail is important to reduce both the peak pressure of near-field signature and the nacelle drag. A nozzle shape, which has an inclined exit shape without a boat-tail portion at lower side, demonstrated a good potential to reduce aft-boom. Supersonic wind tunnel tests using a jet with high-pressure air were also performed to validate the numerical analyses and the results showed good agreement with numerical analyses.

Eulerian CFD modeling of nozzle geometry effects on ECN Sprays A and D: assessment and analysis

Diesel spray modeling is a multi-scale problem with complex interactions between different flow regions, that is, internal nozzle flow, near-nozzle region and developed spray, including evaporation and combustion. There are several modeling approaches that have proven particularly useful for some spray regions although they have struggled at other areas, while Eulerian modeling has shown promise in dealing with all characteristics at a reasonable computational effort for engineering calculations. In this work, the [Formula: see text]–Y single-fluid diffuse-interface model, based on scale separation assumptions at high Reynolds and Weber numbers, is used to simulate the engine combustion network Sprays A and D within a Reynolds-averaged Navier–Stokes turbulence modeling approach. The study is divided into two parts. First of all, the larger diameter Spray D is modeled from the nozzle flow till evaporative spray conditions, obtaining successful prediction of numerous spray metrics, paying special attention to the near-nozzle region where spray dispersion and interfacial surface area can be validated against measurements conducted at the Advanced Photon Source at Argonne National Laboratory, including both the ultra-small-angle X-ray scattering and the X-ray radiography. Afterwards, an analysis of the modeling predictions is made in comparison with previous results obtained for Spray A, considering the nozzle geometry effects in the modeling behavior.

Effect of Nozzle Geometry on Particle Size Distribution in Atomized Spray of Metastable Superheated Liquid

It is experimentally shown that diverging nozzles with a cone angle of 12o -14° and a length of 10-15 mm provide the finest atomization of metastable superheated liquid with a submicron droplet fraction at a level of 65-70%.

Effect of Bath Depth and Nozzle Geometry on Spout Height in Submerged Gas Injection at Bottom

Spout height is a widely used parameter to quantitatively analyze the performance of the submerged gas injection in industrial applications. However, the effect of bath depth and nozzle geometry on spout height in submerged gas injection is still unclear. In this work, the effect of bath depth and nozzle geometry on spout height in submerged gas injection at bottom was experimentally investigated. Circular-shaped, three-leaf-shaped, four-leaf-shaped, and four-flower-shaped nozzles were used for this study. Spout height was extracted from the images captured by high-speed camera and analyzed by digital image processing. The results indicate that the effect of nozzle geometry on spout height is as important as gas flow rate and bath depth. Through dimensional analysis, predictive correlations of spout height from circular shape and four-leaf shape were developed with dimensionless bath depth and a modified Froude number using orifice perimeter and opening area as characteristic parameters. Experimental data were compared with the correlations from literature and good agreement was found.

Effect of nozzle geometry on pressure drop in submerged gas injection

Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths. Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter AoL o −2 and on the modified Froude number gd o 5 Q−2 with the hydraulic diameter of the nozzle do as characteristic length.

Effects of Nozzle Geometry on Turbulent Characteristics and Structure of Surface Attaching Jets

The effects of nozzle exit geometry on the characteristics of a surface attaching jet were investigated experimentally. Three different types of nozzle geometries were studied, including a circular, square and rectangular nozzle with the same exit area. The jets were discharged with an offset height of two nozzle width at a Reynolds number of 5500. A particle image velocimetry system was used to measure the flow. Instantaneous visualizations revealed that the largest enhancements in the near field mixing and entrainment occur in the minor plane of the rectangular nozzle compared to the square and circular nozzles resulting in more rapid expansion of the shear layer. This also caused a faster deflection of the jet towards the free surface, maximum velocity decay and spread rates of the rectangular jet with minor axis orientation. The jet-surface interaction was examined using surface velocity, vorticity thickness and surface turbulence intensities. It was found that the damping of the surface-normal velocity fluctuations at the free surface is more severe in the minor plane of the rectangular jet than the square and circular nozzles. The influence of the free surface was also felt in the profiles of mean velocity and Reynolds stresses. The attenuation of Reynolds shear stress due to confinement was more dramatic in the minor plane of the rectangular nozzle than the other geometries. To quantify the influence of nozzle geometry on the coherent structures in the interaction region, two-point correlations of the velocity fluctuations and swirling strength; and proper orthogonal decomposition were performed.

Numerical Modelling of Internal Flow in Water Mist Injectors: Effect of Nozzle Geometry and Operating Conditions

Water mist fire fighting has achieved a well established position in fire protection for industrial and civil applications. The performances of water mist nozzles, largely used in water mist production, are deeply influenced by the internal nozzle flow characteristics and CFD modelling is a powerful tool to analyse them in details. The paper focuses on the numerical investigation of the internal flow in pressure swirl injectors for water mist applications. 3D large eddy simulations based on the Volume-Of-Fluid methodology have been implemented. The flow is assumed to be incompressible and under isothermal non-reacting conditions. Validation of the model against available experimental data is performed with satisfactory results. The effect of internal nozzle geometry on the injector behaviour is investigated by modifying the inclined swirling channels (five configurations) and the injection pressure in the range 5 to 320 bar. The effect of the size of cylindrical and conical swirl chambers are also independently investigated. Three different flow regimes can be distinguished as a function of imposed swirl and injection pressure and a map is reported to clarify the effect of these parameters. When a stable hollow cone spray is formed the mass flow rate fluctuations are < 5%, corresponding to a discharge coefficient between 0.34 and 0.50. When no air core is present in the discharge hole, mass flow rate fluctuations as high as 16% are observed, which correspond to discharge coefficient as high as 0.7. A detailed quantification of in-nozzle characteristics, like swirl number and momentum flux distribution along the nozzle and lamella thickness in the discharge hole, is reported and discussed, with particular emphasis on stability and transient behaviour of the atomiser internal flow, which represents the main novelty of the present study.

Viscous Heating Assists Jet Formation During Needle-Free Jet Injection of Viscous Drugs.

Jet injectors use a high-pressure liquid jet to pierce the skin and deliver drug into underlying tissues. This jet is formed through a short, narrow orifice; the geometry of the orifice and the properties of the fluid affect the nature of the flow. We aimed to discover information about the turbulent and viscous processes that contribute to pressure loss and flow patterns during jet injection. We used computational fluid dynamics methods and experimental observation to investigate the effects of nozzle geometry, fluid viscosity, and viscous heating on jet production. We experimentally verified the temperature change of the jet during ejection, using an infrared camera. Our models accurately predict the average jet speed produced for two example nozzle geometries over two orders of magnitude of viscosity. The models reveal the previously unreported importance of viscous heating in the formation of the jet. Temperatures >65°C were predicted at the edge of the flow as a result of viscous heating. These caused a significant local reduction in viscosity and effectively allowed the fluid to lubricate itself. Our experiments confirmed changes in mean jet temperature of up to 2.5°C, which are similar to those predicted by our model (∼2.8°C). These results reveal the importance of the viscous heating properties of a fluid in the formation of high-speed jets for drug delivery. This property is crucial to consider when formulating new drugs for needle-free jet injection.

Effect of nozzle geometry on critical-subcritical flow transitions

The geometry of converging-diverging nozzles affects the conditions at which critical-subcritical flow transition occurs. The objective of this work is to develop guidelines to identify the optimum nozzle geometry that maximizes critical pressure ratio while minimizing pressure drop across the nozzle. Experiments were conducted in a facility with 1.5 in. ID PVC pipelines and a 30 ft. long lateral pipeline section. In total, 27 different nozzle geometries were tested, divided into two groups – conical and parabolic nozzles. Nozzles from the ASTAR, Deich, LJ and Moby Dick nozzle groups showed improved performance compared to other nozzle groups. It was determined that a smaller diverging angle and absence of an elongated throat resulted in a higher critical pressure ratio. Length of converging and diverging sections of nozzles did not have as much of an impact on nozzle performance as the throat diameter and shape of converging and diverging sections.

Effect of Geometric Parameters on Mean Drop Sizes From Dual-Orifice Pressure Nozzles

Experimental studies have been conducted to investigate the effect of nozzle geometries on the atomization. Extensive measurements of mean drop size are conducted on the 15 dual-orifice pressure nozzles. These nozzles provide a range of discharge coefficient from 0.06 to 0.13. These experimental results are used to substantiate a semi-empirical correlation derived for determining the Sauter mean diameter (SMD) of sprays generated by dual-orifice pressure nozzles. The correlation is obtained by modeling the liquid internal and outer flow that govern the atomization process in dual-orifice pressure nozzles. A very satisfactory agreement is demonstrated between the predictions based on the correlations and the actual measured values of the SMD.

Effect of nozzle geometry on the gas dynamics and evaporation rates of Suspension High Velocity Oxy Fuel (SHVOF) thermal spray: A numerical investigation

Thermally sprayed coatings formed from sub-micron or nanoparticles feedstock provide enhanced coating properties and Suspension High Velocity Oxy Fuel (SHVOF) thermal spray is a process that allows the deposition of dense coatings from fine particulates. However, in SHVOF thermal spray, submicron and nanoparticles are significantly influenced by fluctuations in the gas velocity and temperature field because of the turbulence and disturbance of the gas fields from the breakup of the suspension due to the small inertia of the particles. In this study, an ethanol suspension containing widely used engineering ceramic particles, TiO2, with four different particle concentrations was considered 0, 10, 15 and 25 wt%. The aim of this paper was to model four nozzle geometries and to investigate the influence the nozzle geometry has on the gas flow and the evaporation rate at four particle concentrations. Comparing four nozzle geometries it is found that the gas exits the longer barrel nozzles at a high velocity; while the velocity in the free jet region beyond the shock diamonds is greater for the shorter nozzles. It is seen that the shorter the nozzle the higher the gas temperature in the free jet; which is due to the lower contact time of the gas with the cooled nozzle walls. This study also considered the effect the nozzle geometry has on the evaporation of the suspension. It was found that the longer the combustion chamber the lower the maximum evaporation rate. Moreover, higher particle concentrations result in evaporation commencing closer to the nozzle inlet due to the lower volatile fraction of the suspension.

Effect of Nozzle Geometry on Flowfield for High Subsonic Jets

The present Paper aims to present a comparative study of the external and internal flow characteristics through an axisymmetric circular convergent nozzle, a nonserpentine convergent nozzle with an elliptic exit, and a shallow single serpentine convergent nozzle with an elliptic exit under the fully expanded condition at a nozzle pressure ratio of 1.6. The static wall pressure measurements reveal that, due to the axisymmetric shape, the conventional circular nozzle shows symmetric jet development. However, the flow through the serpentine nozzle follows its curvature, making the flow through it asymmetric. The upper and the lower walls have different flow expansion due to the secondary flow created by the wall curvature and transition. This asymmetric nature of the flow through the serpentine nozzle also vectors the external jet toward the lower wall. The saddle-shaped velocity profile is observed along the major axis plane of serpentine nozzle. The nozzles with elliptic exits show higher mass entrainment and faster velocity decay as compared to the conventional circular nozzle. The nonserpentine elliptic nozzle shows the maximum velocity decay with the fastest decay rate among the three nozzles considered. This nozzle also shows the maximum mass entrainment across its major as well as minor axes and thus reduces the length of the external jet more effectively.

Effect of Nozzle Geometry and Distance on Cooling Performance of Impinging Jets

Effect of Nozzle Geometry and Distance on Cooling Performance of Impinging Jets

Experimental study on the effect of nozzle geometry on string cavitation in real-size optical diesel nozzles and spray characteristics

Cavitation is quite important for the diesel spray atomization and the combustion of air–fuel mixture. In this study, a high-speed CMOS camera equipped with a long-distance microscope was utilized to capture the transient cavitating flow and spray characteristics in real-size optical nozzles with needle motion. The transient cavitation images, including geometry-induced cavitation and vortex-induced string cavitation, were captured clearly in cylindrical-orifice nozzles and tapered-orifice nozzles, respectively. Besides, the agglomerated phenomenon of geometry-induced cavitation was visually captured and analyzed for the first time. It was found that the string cavitation in nozzle excites the instability of spray cone angle and it is synchronized with increase of spray cone angle. In addition, it is the string cavitation but not geometry-induced cavitation has a much larger contribution to the increase of spray cone angle. It is interesting that the influence of agglomerated geometry-induced cavitation on spray cone angle was prominent. Furthermore, both the nozzle orifice L/D ratio and sac types have significant influences on string cavitation and spray characteristics. The smaller L/D ratio and VCO-type nozzles are prone to incur the stronger string cavitation, and then spray cone angle is obviously larger.

Effect of nozzle diameter on bubble generation with gas self-suction through swirling flow

Understanding the effects of nozzle geometry on bubble generation is very important in nozzle design. Gas self-suction is discussed with different nozzle diameter by detecting the pressure at gas inlet. The effects of nozzle diameter on the bubble size distribution and spray morphology of bubble generators were investigated to assess the aeration capabilities. The increase in the geometric criterion K from 3.2 to 4.8 leads to an amazing transformation from non-self-suction to the maximum vacuum degree. The maximum vacuum degree with a geometric criterion K of 4.8, the maximum aeration capability with a K of 8.0, and the minimum bubble diameter with a K of 12 were achieved. The liquid handling capacity and spray angle increase together with increasing K. This work contributes to the foundation for the design of an industrial bubble generator through a pressure-swirl nozzle.

Effects of nozzle geometry on the reignition by hot gas jets

ABSTRACTIn this paper, the ignition of a hydrogen–air mixture by a jet of burned hot gas (often termed reignition in the field of explosion protection) is studied in a two-chamber experimental configuration. This experiment allows systematic creation of hot gas jets emerging from a thin, long nozzle and them to impinge into an unburned, cold hydrogen–air mixture, possibly causing (re)ignition. In an extensive parametric study, hot exhaust gas jets originating from different nozzle diameters (0.6 mm–1.2 mm) and lengths (25 mm and 70 mm), as well as different pressure ratios along the nozzle (up to 5.5) were tested for their ability to reignite the hydrogen–air mixture. It was investigated how often reignition occurred within 10 tests under each condition. Dependencies between the occurrence of reignition and the mentioned nozzle and jet parameters were determined. It was found that the outcome (reignition or no reignition) can differ for nominally identical experimental paramete rs, which demonstrates the parametric sensitivity of the process. The statistical frequency of reignition occurrence depends on the nozzle diameter as well as on its length. For pressure ratios above the critical value, reignition occurred more often for the longer nozzle (l = 70 mm) at a given diameter. Some of these findings, notably the dependence on the nozzle length, pose a challenge to conventional models.

Effect of Nozzle Geometry on the Microstructure and Properties of HVAF-Sprayed WC-10Co4Cr and Cr3C2-25NiCr Coatings

Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications to improve wear resistance. In the aim of improving coating quality by utilising finer particle size distributions, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high-quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr and Cr3C2-25NiCr powders were sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting carbide dissolution can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent–divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. The increase in particle velocity significantly improved the coating structure and density. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved in the case of WC-10Co4Cr coatings with the increasing average particle velocity.