Nozzle Geometric Parameters Research Articles

Numerical investigation of a Coandă-based fluidic thrust vectoring system for subsonic nozzles

The numerical investigation of a novel subsonic thrust concept for fluidic thrust vectoring (FTV) of jet engines is the subject of this publication. FTV possibly offers advantages over conventional mechanical thrust vector control such as decreased complexity, mass and maintenance costs. The operating principle of the FTV nozzles under investigation at the Institute of Jet Propulsion is based on the Coandă effect. The applied concept of thrust vectoring uses dedicated secondary flow channels which are mounted in parallel around the nozzle inner cone or the nozzle wall. If required, bleed air, provided by extraction from the engine compressor or from an external source, is injected at a specific nozzle pressure ratio at the nozzle throat A_8 through these secondary ducts, resulting in the redirection of the secondary jet towards the convex Coandă surface. The interaction between the primary mass flow and the secondary jet leads to a redirection of the primary exhaust mass flow of the engine and thus to a vectoring of the exhaust flow. In this paper, the influence of different nozzle geometric parameters and different operating points are investigated within an extensive parametric study applied to a convergent two-dimensional thrust vectoring nozzle using computational fluid dynamics tools. Thrust vector deflection of up to {20}^{circ } at a maximum secondary to primary mass flow ratio of 10 % is achieved. Reducing this mass flow rate to 5 % still yields vectoring angles of up to {15}^{circ } whereby similar deflection angles compared to conventional mechanical thrust vectoring systems are achievable.

Jet characteristics and optimal design of hydraulic perforating nozzles for natural gas hydrate reservoirs

Jet nozzle is a core component of the hydraulic perforating fracturing tool, and the design of the nozzle structure directly affects the perforating effectiveness and efficiency. In this paper, the flow field characteristics of hydraulic perforating nozzles are calculated by the SST k- ω turbulence model. The results show that the nozzle structure parameters significantly influence the jet performance. Through orthogonal experiments, the conical-cylindrical nozzle geometric parameters are preliminarily optimized as follows: the cylindrical segment diameter is 6 mm, the contraction angle is 10°, the contraction segment length is 8 mm, and the cylindrical segment length is 12 mm. The results can provide theoretical guidance for later experimental research on jet rock breaking and optimization design of the jet tools.

Effects of geometric parameters on flow and atomization characteristics of swirl nozzles for artificial snowmaking

With the worldwide popularity of skiing, artificial snow technology has been gradually developed. Atomization is the key process for snowmaking, and swirl nozzles are applied as the core atomization components in snowmakers. In this research, the effects of nozzle geometric parameters on the flow and atomization characteristics are explored to improve snowmaking performance. The flow and atomization process in swirl nozzle is simulated by VOF-DPM approach after experimental validation. The results show that appropriate increase of orifice diameter and swirl slot area can effectively reduce the atomization droplet size and increase the spray flow rate. As the diameter ratio of swirl chamber to orifice decreases from 6.67 to 2.5, Sauter Mean Diameter (SMD) decreases by 54.9%, and mass flow rate increases by 168.2%. When orifice diameter is 4.0 mm, as the atomizer constant increases from 0.1688 to 0.3797, SMD decreases by 65.8% and mass flow rate increases by 114.3%. Furthermore, the reduction in SMD and the increase in spray flow rate are attributed to high discharge velocity. The swirl nozzles have the best atomization droplet size and maximum flow rate, as the inlet pressure is 0.6 -1.4 MPa, orifice diameter is 4.0 mm and swirl slot width is 2.25 mm.

A Study on Converging-Diverging Nozzle Design for Supersonic Spraying of Liquid Droplets Toward Nanocoating Applications

Abstract Supersonic cold spray (CS) of functional nanomaterials from atomized droplets has attracted significant attention in advanced thin-film coating as it enables particle deposition with high-adhesion strength. In CS, optimum design of the supersonic nozzle (i.e., converging-diverging nozzle) is essential for accelerating particles to desired velocities. However, research on the nozzle design for supersonically spraying of “liquid droplets” for nanocoating applications is limited. To this end, we investigate the effect of nozzle geometrical parameters, including throat diameter, exit diameter, and divergent length on droplets impact velocity by numerical modeling and experimental validation, followed by a case study on nanocoating. The discrete-phase modeling was employed to study droplets’ flow behavior in continuous gas flow for various nozzle geometries. The results reveal that the nozzle expansion ratio, defined as a function of throat and exit diameters, has a significant influence on droplet velocity, followed by divergent length. Noteworthy, to correctly accelerate “low-inertia liquid microdroplets,” it was found that the optimum nozzle expansion ratio for axisymmetric convergent-divergent nozzles should be in a range of 1.5–2.5, which is different and way smaller than the recommended expansion ratio (i.e., 5–9) for CS of conventional micron-scale “metal” powders. Based on the simulation results, an optimum design of supersonic nozzle is established and prototyped for the experimental studies. Particle image velocimetry (PIV) was used to experimentally investigate the spray flow field and to validate the numerical modeling results. Moreover, coating experiments using the optimized nozzle confirmed the effective supersonic spraying of droplets containing nanoparticles, thereby showing the potential for advanced nanocoating applications.

Simulation of the dynamics of a flexible fiber in the swirling airflow in a nozzle containing cylindrical and divergent conical sections

Swirling airflow plays a key role in textile production processes. The structure and properties of a textile processed by utilizing swirling airflow depend to a large extent on the dynamics of the fibers in the flow. This work presents a numerical investigation of the dynamics of a flexible fiber in the tangentially injected swirling airflow in a nozzle containing cylindrical and divergent conical sections, which is frequently encountered during textile production. Simulation of the three-dimensional, transient, compressible and turbulent swirling airflow field in the nozzle is first conducted. A model for the particle-level simulation of a flexible fiber in a wall-bounded flow is consequently adopted for studying the fiber motion in the nozzle. This model assumes the fiber to be composed of several massless elastic rods connected by rigid ball–socket joints where various forces and torques are exerted. The stretching, bending and twisting deformations of the fiber as well as the fiber–wall collision can all be modeled. The motional characteristics of the flexible fiber can be obtained by solving the translational and rotational equations for all the ball–socket joints in the fiber model. Based on the model, the effects of two process and nozzle geometric parameters – the nozzle pressure and radial position of the injectors – on the fiber motion are studied. The results show that the model and methods presented in this work can provide effective and useful insights into the dynamics of flexible fiber in the swirling airflow field inside complex-structured nozzles employed in the textile production processes.

Flow and deformation behaviors of cementitious materials through nozzles with different geometric parameters: Experimental and numerical approaches

Nozzle geometric parameters are important to control the flow and deformation behaviors of printed filament. Choosing the right nozzle geometric parameters before the printing process is critical and requires considerable attention. In this study, nozzles with various geometric characteristics were designed and fabricated. Experiment and computational fluid dynamics (CFD) simulation were used to investigate the flow and deformation behaviour of printing ink via these nozzles. The results indicated that increasing of the area ratio of outlet to inlet AR (Aoutlet/Aintlet) and direction of material deposition θ will reduce the extrusion pressure. Changing the direction of material deposition θ is a critical means for controlling the printing pressure. Increasing of nozzle aspect ratio Ψ (Wn/Hn) and decreasing of direction of material deposition θ will reduces the deformation rate of deposited filament. This study may provide a theoretical guidance for the design and selection of nozzle before printing process.

Optimization of the primary nozzle for design a high entrainment ejector in spacesuit portable life support system

In looking forward to the future of human space exploration, it is increasingly stringent for the ventilation circuit subsystem in terms of reliability, simplicity and energy-efficient. Considering this requirement, the ejector, with the advantages of miniature size, no parasitic energy consumption and high reliability, is considered an appropriate alternative to the ventilation fan because it simultaneously implements the functions of mixing, entraining, and lifting pressure. This paper proposed a high entrainment ejector for application in spacesuit portable life support systems. The optimizations of the ejector nozzle geometrical parameters and nozzle exit position (NXP) were performed using a validated three-dimensional numerical model under various operating conditions. The results show that the NXP has a more significant effect on entrainment performance than other geometrical parameters in spacesuit portable life support systems, and the optimum NXP are not impacted by changes of the primary flow pressure and mixing chamber diameter, which similarly obtained the optimal entrainment ratio at the nozzle exit position of 2 mm. The maximum increments of entrainment ratio with the NXP varying from −4 mm to 8 mm are 0.2945 and 0.7664 under different primary flow pressures and mixing chamber diameters, respectively. Compared with the nozzle exit position, the most effects of nozzle converging angle and length on entrainment ratio are just 0.0864 and 0.0445. The optimum ejector extends the oxygen service duration by 12 min compared to the original one for the same volume of an oxygen tank, which is vital for the astronauts to conduct extravehicular activities in outer space.

Evaporative pre-cooling of a condenser airflow: investigation of nozzle cone angle, spray inclination angle and nozzle location

ABSTRACT In hot and dry areas, evaporative cooling can enhance the performance of air-cooled condensers. Pre-cooling of a condenser airflow in a channel by a spray nozzle has been studied numerically. The Eulerian-Lagrangian 3D equations for two-phase flow have been discretized using the finite volume method. An experimental setup has been prepared to validate the numerical model. The effects of nozzle cone angle, spray inclination angle, and nozzle location in the channel have been investigated on the outlet air temperature, droplet evaporation rate, and spray cooling efficiency. The results represent that, between four analyzed geometrical parameters, nozzle longitudinal location is the most important parameter and the spray inclination angle has the lowest degree of importance. Spray inclination angle analysis displays that the counter-flow condition of the nozzle is more efficient than co-flow and cross-flow conditions. The case with the nozzle height of 45 cm in the duct, spray inclination angle of 180 ∘ , and nozzle cone angle of 60 ∘ is the best case. The maximum and minimum spray cooling efficiencies among the cases are about 30.5% and 21%, respectively. Hence, the nozzle geometrical parameters can affect the evaporative cooling capacity up to 45%.

CFD investigation of air-oil two-phase flow in oil jet nozzle

In aero-engines applications, nozzle geometric parameters have major effects on the lubricating oil to accurately reach target gears or bearings. To investigate the deviation phenomenon of oil jet flow in the lubrication system, the computational fluid dynamics (CFD) technique integrating with the volume of fluid (VOF) method and SST k- ω turbulence model is adopted to deeply understand the flow characteristics of the nozzle. By leveraging this method, the relationship between nozzle geometry, inlet pressure, jet velocity, and jet deviation are firstly analyzed. The results reveal that a higher average velocity and smaller jet deviation can be determined via adjusting the nozzle geometry. Furthermore, a specific test rig, composed of an oil supply system, target system and data collection system, is set up for oil injection test; experimental outlet velocity and mass flow rate of oil passing through the hole on the target plate are monitored and recorded. The experimental findings compare well with numerical results obtained by the CFD method.

Numerical Study on Effects of Geometric Parameters on the Release Characteristics of Straight Sudden Expansion Gas Extinguishing Nozzles

In order to guide the optimization design of the nozzle of the aircraft-fixed gas fire extinguishing system, we studied the influence of nozzle geometric parameters including outlet–inlet area ratio, length–diameter aspect ratio, and wall roughness on the distribution of pressure and velocity in the nozzle on the basis of CFD simulations. Although the structure of the nozzle is axisymmetric, the spatial distribution of the pressure and velocity during the flow and release of gas extinguishing agent is not completely symmetric. It was found that both of the outlet–inlet area ratio (δ) and the length–diameter aspect ratio (ξ) had a significant impact on the distribution characteristics of the pressure and axial velocity in the nozzle. With the increase of δ, the average pressure at the outlet cross-section of the nozzle decreased monotonically, while the average axial velocity at the outlet increased approximately linearly. When ξ≥2, the uniformity of the pressure and velocity distribution at the nozzle outlet was significantly improved. Moreover, with the increase of ξ, the average pressure and the average axial velocity of the outlet both showed a non-monotonic change trend, and the optimal value of ξ should be about 3.0. Compared with δ and ξ, the influence of the nozzle wall roughness (εN) on the flow and release characteristics of the extinguishing agent was weak. With the increase of εN, the average pressure of the nozzle outlet increased slightly, while the average axial velocity at the nozzle outlet decreased slightly.

Velocity Flow Field Characteristic on Nozzle Cavity using Central Composite Design of Computational Method for Dry Ice Blasting System

In the development of dry ice blasting nozzle geometry, the critical process parameters depend on particle jet velocity. However, very few researchers have attempted sensitivity on the velocity flow area of specific nozzle geometric parameters. A numerical simulation approach was performed in this paper using Ansys Fluent to investigate different nozzle parameters on the velocity flow field. A two-dimensional model is solved iteratively using averaged Navier-Stokes under Eulerian flow description. It was found that the velocity value increases that reach 550 m/s with an increment of the nozzle area ratio of up to 20 without influencing convergent angle and the velocity magnitude drop linearly from 525 m/s to 505 m/s in with the rise of divergent length that swell up to 700 mm and with constant convergent angle and convergent length.

Experimental Optimization of Self-Priming Pump Based on the Full Factor Test


 Self-priming pump as the core equipment for flood fighting and emergency rescue plays an important role in flood prevention and other fields. More importantly, the geometric parameters of the self-priming nozzle directly determine the performance of the self-priming pump. In the previous analysis，only small amount of experiment was conducted to optimize the geometry parameters of self-priming nozzle, and the interaction between the parameters was not considered. In this paper, the full factor test method is employed to explore the main and interaction effect of the nozzle geometric parameters on the self-priming performance, and the order of response to self-priming time is obtained. Meanwhile, a novel self-priming performance model was established, the self-priming time of different geometric parameters self-priming nozzles can be effectively predicted, and the test analysis cycle and production costs were greatly reduced. Finally, the self-priming test under different self-priming height with optimal self-priming nozzle was conducted, the variation regulation between self-priming time and self-priming height was obtained. Therefore, this research could effectively provide the design reference of self-priming nozzles optimization.

A Review on the Erosion Mechanism in Cavitating Jets and Their Industrial Applications

Cavitating jets have been widely studied for over a century, but despite the extensive literature on this subject, the implementation of cavitating jets in many industries is still very limited due to technical challenges. The main purpose of the present paper is to provide recommendations on using the cavitating jets based on a comprehensive literature review on the erosion mechanism in these jets. Self-resonating jets are extensively discussed in the present paper due to their importance in amplifying the erosion effect of cavitating jets. The influence of different jet nozzle geometric parameters and the operating conditions of the cavitating jet flow on the erosion mechanism is also discussed. Finally, well drilling in addition to multiple other industrial applications of cavitating jets are examined.

INVESTIGATION OF EVAPORATION AND CONDENSATION PROCESS OF INDUCED FLOW USING STEAM EJECTOR

The research aims to understand the design parameters of steam ejector nozzle on the performance of flash evaporation induced by the effect of a steam jet passing through it. The research concentrates on studying the effect of ejector nozzle outlet diameter on induced flow from preheated water in a specified evaporator using a subsonic ejector. The thermal energy extracted from the condensed steam mixture in the condenser is used to heat the water in the evaporator. The experimental tests investigate the effect of nozzle geometry on the induced evaporation process by changing nozzle outlet diameter while keeping the pressure of evaporator, condenser and primary steam constant. The experimental results proved that both primary and secondary steam mass flow rates increase versus nozzle outlet diameter, while the entrainment ratio of secondary to primary steam flow rates decreases due to the restricted increase of the secondary steam mass flow rate. The mathematical model prepared to simulate the behaviour of the subsonic ejector is validated using the comparison between experimental and theoretical results. The mathematical model showed that maximum entrainment of 0.57 is obtained at a primary steam pressure of 2 bars when the nozzle outlet diameter is fixed at 1.5 mm, while minimum entrainment ratio of 0.17 is estimated at 1.5 bar pressure related to primary steam when the nozzle outlet diameter is fixed at 2.5mm. The authors recommend defining nozzle geometrical parameters according to the operating conditions of the experimental test rig to enhance ejector efficiency.

Numerical analysis on heat-flow-coupled temperature field for orthogonal face gears with oil–jet lubrication

Lubrication and cooling performances of face gears with oil–jet lubrication are closely related to the nozzle layouts. To investigate the influence of the nozzle layouts on the lubrication performance of the face gears, a numerical analysis method based on heat-flow coupling is adopted in this study for predicting the transient temperature characteristics. First, a mathematical model of impingement depth integrating the nozzle spatial layouts, injection parameters, and geometric parameters of the given face gear is presented for determining the nozzle. Then, after accessing the friction heat, the heat-flow-coupled finite element model is built to resemble the oil–jet lubrication process and obtain the temperature field on the tooth surface. Finally, under the same nozzle layouts, the temperature distributions are compared with the oil pressure and oil volume fraction reported in previous studies. The results reveal that the nozzle layouts significantly affect lubrication performance. Specifically, the lubrication performance of the lateral layout parameter near the middle point of the tooth width is better, and there is a certain range for the longitudinal layout parameter and jet elevation angle. This study can provide a reference for further optimizing the nozzle layouts and prolonging the service life of the orthogonal face gear.

Numerical investigation on heat transfer characteristics of twin-web turbine disk-cavity system

A twin-web turbine disk with two rotor-stator cavities and inner cavity system is developed to investigate the effect of nozzle geometrical parameters on both sides, including pre-swirl angle (θ3), radial position (Rd), and inlet flow ratio of of the rotor-stator cavity to inner cavity (P1), on the heat transfer characteristics of the system using the RNG k-ε turbulence model. The maximum disk temperature (Tmax), disk temperature uniformity and local Nu are adopted as evaluation indexes. Nine structures with different θ3 and Rd are designed. The results show that the effect of θ3 is greater than that of Rd. Model 3 with a high-radius nozzle (Rd = 0.8) and small pre-swirl (θ3 = 30°) shows the lowest Tmax and the highest Nu. The axial temperature difference is affected less by θ3 and Rd, i.e., approximately 11 K. The radial temperature uniformity improved with increasing Rd. The Nu on the disk wall increased along the direction of radial temperature gradient increasing. The inlet flow ratio is optimized based on model 3 with different P1. It is revealed that Tmax is the lowest and the radial temperature uniformity is the best when P1 is 1. The axial temperature uniformity is appropriate when P1 is 1 or 2. After optimizing P1, Tmax reduced by 7.1 K, whereas the average temperature of Clip1 and Clip2, TC1 and TC2, reduced by 0.2 and 1.6 K, respectively. The radial temperature uniformity improved slightly, but the axial temperature difference increased by 1.4 K.

Dimensional analysis modeling of spraying operation – Impact of fluid properties and pressure nozzle geometric parameters on the pressure-flow rate relationship

In food industry, atomization is an essential process as a large range of products are manufactured by spray drying of concentrated solutions. The pressure drop inside the nozzle, and its relation with the flowrate, is of prime importance to size an efficient continuous process. This work thus aims at both studying liquid atomization using pressure nozzles with throttle inserts and proposing a ready-to-use pressure/flowrate correlation from a series of experimental data. Beside the process parameters (flowrate) and fluid parameters (viscosity, density) of prime importance, the geometrical parameters of the nozzle were also accounted for to obtain a generic correlation. Using Newtonian maltodextrin aqueous solutions with viscosity ranging from 1 to 70.10-3 Pa s and eleven nozzle geometries, 264 experiments were performed. Through the use of a dimensionless pressure drop number (Euler number), all the experimental points gathered on a single Eu* vs. Re curve where conventional atomization regimes could be clearly identified. A comprehensive dimensional analysis, relying on the Vashy-Buckingham theorem, was performed. A set of dimensionless correlations, allowing to predict the pressure loss over a wide range of Reynolds number from parameters linked to the fluid, process and nozzle geometry, was then deduced from experimental data.

Effects of nozzle geometries and needle lift on steadier string cavitation and larger spray angle in common rail diesel injector

The cavitating flow in diesel injector nozzles plays a vital role in spray atomization and formation of fuel–air mixture, since vortex-induced string cavitation has recently been found a much more influence on spray compared to the ordinary geometry-induced film cavitation. In this study, in order to investigating string cavitation and its’ enhancement on spray, the visualization experimental platform for the real-size optical tapered-hole nozzle was built based on the high-pressure common rail fuel injection system. Groups of optical nozzles with different geometries were designed for exploring the couple effects of several nozzle geometric parameters, including nozzle sac chamber depth, nozzle-hole position height and needle lift, on the three-dimension vortex flow structure and then on the string cavitation and spray characteristics. Results indicated that the string cavitation characteristics are tightly associated with couple characteristics of the parameters. The stable and strong string cavitation during the whole injection process can be obtained in the Min-sac nozzle with the high hole position under the low needle lift. The string cavitation extends to the nozzle-hole outlet, and subsequently induces the special hollow cone spray with air in the spray center location and corresponding a larger spray cone angle even under not so high injection pressure.

Transparent high-pressure nozzles for visualization of nozzle internal and external flow phenomena.

A new design for transparent high-pressure nozzles is presented in this work. This new design enables using the innovative Selective Laser Etching (SLE) method to manufacture transparent nozzles with outstanding accuracy. Therefore, not only the simultaneous visualization of the flow mechanics inside and outside the nozzle is enabled, but the manufacturing method applied also allows for the realization of individual nozzle geometries. Thus, nozzle internal flow phenomena (e.g., cavitation, swirl, and air inlet) and their influence on primary breakup can be analyzed with realistic nozzle geometries, e.g., for automotive applications. In addition, targeted three dimensional nozzle geometric parameters can be designed and manufactured in order to get specific tailor-made spray characteristics (e.g., droplet size distribution, spray angle, and penetration length). The basis for the transparent nozzle design is a two-parted nozzle, consisting of a re-machined original serial nozzle body and a transparent nozzle tip. The innovative SLE is used to produce the geometry of the transparent nozzle tip in fused silica, and laser polishing is utilized to achieve a maximum optical quality of nozzle surfaces for visualization. Bonding of both nozzle parts is achieved by a specially designed adhesive method. For a first feasibility study, a transparent nozzle with a simplified nozzle geometry is manufactured and used for a first study. In this study, simultaneous investigation of nozzle internal flow phenomena and their impact on spray breakup are visualized. First microscopic images of the nozzle internal flow show the formation of cavitation, its effect on nozzle internal temperature (apparent by differences in the fluid refractive index), and also the corresponding impact on spray breakup during injection. The penetration of ambient gas into the nozzle is verified at the end of injection as well as the influence of this air on the spray formation during the start of injection.

Research on geometrical parameters effect of fan nozzle jet performance based on orthogonal experiment

In order to determine the significance and importance order of the jet performance caused by fan nozzle's geometric parameters of aero-engine online cleaning equipment, the orthogonal experiment method, standard k–ɛ turbulence model and volume of fluid (VOF) two-phase flow algorithm are used to research the jet of fan nozzle. The sensitivity of nozzle contraction angle, nozzle area ratio, nozzle incision angle, nozzle exit thickness and offset to the influence of fan nozzle spray angle was verified by range analysis and variance analysis. The results of the two analysis methods consistently show that the main order of influence of the geometric parameters of fan nozzle on spray angle is nozzle area ratio, nozzle incision angle, nozzle exit thickness, offset and nozzle convergence angle. The former two have more influence on the spray angle than the others. Finally, the simulation results and orthogonal test results are verified by the injection experiment of the fan nozzle. The jet shape is mainly determined by the nozzle area ratio and incision angle. The larger the incision angle and the nozzle area ratio are, the smaller the spray angle becomes.