Effect Of Nozzle Shape Research Articles

Investigation of the effect of nozzle shape on supersonic/hypersonic impactors designed for size discrimination of nanoparticles

In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach. The aim of this study was to develop a nozzle design for supersonic/hypersonic impactors with the smallest possible cut-off size d50 and rather sharp collection efficiency curves. The simulation results show that the changes in the angle and width of a converging nozzle do not alter the cut-off size of the impactor; however, using a conical Laval nozzle with an L/Dn ratio less than or equal to 2 reduced d50. The effect of using a cap as a focuser in the nozzle of a supersonic/hypersonic impactor was also investigated. The results show that adding a cap in front of the nozzle had a noticeable effect on decreasing the cut-off size of the impactor. Both flat disks and conical caps were examined, and it was observed that the nozzle with the conical cap had a lower cut-off size.

Numerical Simulation of Pulse Cleaning Process in Ceramic Filtration System

The numerical simulation model was established using FLUENT code to analysis the flow field of pulse cleaning process of filtration system. The pressure variation with pulse cleaning time was studied. The effect of nozzle shape and diffuser shape on flow field was investigated. The diffuser construct can affect the flow field distribution, but the effect is little. The converged nozzle can bring better pulse cleaning effect by bring higher velocity and lower pressure at outlet.

노즐 형상에 따른 전기수력학 프린팅의 실험적 연구

The shape of nozzle cross-section plays an important role in stabilizing electrospray jet. The angle of contact line is governed based on the famous Young-Laplace equation. Compared to a round nozzle that has a constant curvature along the orifice, the square nozzle has four square corner edges and four straight edges that hold the meniscus in a different manner and is of interest in this study. By utilizing both square and round capillary nozzle, we examine the effect of nozzle shape in electrohydrodynamic jetting. The ejections were recorded with a high speed camera and analyzed to examine the jetting repeatability based on dynamic movement of meniscus. The result suggests that if the corner edges are not sharp, then its effect on repeatability is also limited.

Generation and Propagation of Intense Supersonic Beams

Computer simulations and experiments have been performed to quantify the effects of nozzle shape and skimmer placement on high-density supersonic jets. It is shown that the on axis beam intensity achieved is much higher than intensity achieved using standard sonic nozzles. Changes in skimmer design and positioning are required to allow this intense jet to propagate in a typical supersonic beam setup.

Effect of Nozzle Shape on Micro-Cutting Performance of Thin Metal Sheet by Pulsed Nd: YAG Laser

In precision laser cutting, the generation of dross can be reduced by using a high-pressure assist gas flow. However, our previous work made it clear that, for a conventional convergent nozzle, the pressure of assist gas on a workpiece is reduced to less than half of the cylinder gas pressure because of the generation of Mach Shock Disk. Furthermore, the removal of material from the micro-kerf becomes difficult since the fluidity of molten material is low in the narrow kerf. Therefore, nozzle shapes were investigated to improve the removal of material from the micro-kerf, and their effect on the fine cutting of a thin metal plate using a pulsed Nd: YAG laser was also discussed. The height of dross could be reduced by using a Laval throat nozzle with an initial expansion zone compared with that for a straight throat nozzle. The pressure on the workpiece was greater, and the straightness of the assist gas flow was excellent when the Laval throat nozzle with the initial expansion zone was used. Moreover, it was confirmed that the molten material could be effectively removed from the micro-kerf even at a middle cylinder gas pressure of around 600 kPa. Therefore, the Laval throat nozzle with the initial expansion zone can be used for fine cutting owing to its reduction of dross.

Experimental and analytical investigation of liquid sheet breakup characteristics

The main objective of this research is to study analytically and experimentally the liquid sheet breakup of a flat fan jet nozzle resulting from pressure-swirling. In this study the effects of nozzle shape and spray pressure on the liquid sheet characteristics were investigated for four nozzles with different exit widths (1.0, 1.5, 2.0 and 2.5 mm). The length of liquid sheet breakup, liquid sheet velocity and the size of formed droplets were measured by a digital high speed camera. The breakup characteristics of plane liquid sheets in atmosphere are analytically investigated by means of linear and nonlinear hydrodynamic instability analyses. The liquid sheet breakup process was studied for initial sinuous and also varicose modes of disturbance. The results presented the effect of the nozzle width and the spray pressure on the breakup length and also on the size of the formed droplets. Comparing the experimental results with the theoretical ones for all the four types of nozzles, gives a good agreement with difference ranges from 4% to 12%. Also, the comparison between the obtained results and the results due to others shows a good agreement with difference ranged from 5% to 16%. Empirical correlations have been deduced describing the relation between the liquid sheet breakup characteristics and affecting parameters; liquid sheet Reynolds number, Weber number and the nozzle width.

Investigation into the effect of nozzle shape on the nozzle discharge coefficient and heat and mass transfer characteristics of impinging air jets

High velocity impinging air jets are commonly used for heating, cooling and drying, etc. because of the high heat and mass transfer coefficients which are developed in the impingement region. In order to provide data for the designers of industrial equipment, a variety of slot nozzles were tested to determine the effect on heat transfer of both nozzle shape and slot width. A large multi-nozzle rig was also used to measure average heat and mass transfer characteristics under arrays of both slot nozzles and circular holes. As a necessary preliminary to the heat transfer investigation, the discharge coefficients of the nozzles were measured. Then, the experimental results are compared with the simplified flow model. A good agreement was found between the theoretical and experimental results. From the tests, it was also found that the heat transfer results from differently shaped nozzles could be satisfactorily correlated provided that the effective slot width or hole diameter was used to characterize the nozzle shapes.

A Sharp-Interface Level-Set Method for Simulation of a Piezoelectric Inkjet Process

A numerical method is presented for computing the droplet motion in a piezoelectric inkjet process. The level-set method for tracking the liquid–gas interface is extended to treat the immersed (or irregular-shaped) solid surface of an ink nozzle. The no-slip condition at the fluid–solid interface as well as the matching conditions at the liquid–gas interface are accurately imposed by incorporating the ghost fluid approach based on a sharp-interface representation. The dynamic contact-angle condition at the immersed solid surface is implemented by employing a fast marching approach. The numerical method is applied to analyze the effects of nozzle shape, dynamic contact angle, and pressure pulse on the inkjet process.

Evaluation of an optical particle sensor to determine the effect of nozzle shape on counting efficiency

The optical particle sensor (OPS), using light scattering from particles, is widely used in clean-rooms and in atmospheric environmental monitoring. However, parameters that affect the particle counting of the OPS have been less explored previously. The present study examines the effect of the nozzle shape on particle counting performance of the OPS. Experiments and simulation studies were carried out for four different nozzle shapes in conjunction with three different particle sizes. The effect of nozzle shape is evaluated not only by experiments analyzing the intensity of scattered light and particle velocity but also by simulation. Fluent was used to simulate the flow field and particle trajectories. We observed that particle velocity and trajectory are strongly dependent on the input nozzle shape, which in turn has an effect on the particle counting performance. Using these results, the design of OPS can be optimized to provide higher counting efficiency.

E19 Effect of Nozzle Shape on Dross Generation in Fine Cutting of Thin Metal Plate by Pulsed Nd:YAG Laser(Laser processing)

The nozzle shape was investigated in order to develop a high performance nozzle for pulsed Nd:YAG laser cutting, and its effect on fine cutting of thin metal plate was also discussed. In the case of 0.5mm throat diameter Laval throat nozzle with an initial expansion zone, the pressure on workpiece increased, and the straightness of gas flow was improved compared to a traditional straight throat nozzle, and the observation using high-speed video camera could reveal the behavior of removing molten metal downward. The experimental results proved that Laval throat nozzle with an initial expansion zone made it possible to reduce the dross height and the kerf width.

횡류수차 노즐형상이 성능과 내부유동에 미치는 영향

The purpose of this study is to examine the effect of nozzle shape on the performance and internal flow of a cross-flow hydro turbine. CFD analysis for three kinds of nozzle shape is conducted to simulate the effect of nozzle shape. The results reveal that relatively narrow nozzle width is effective to increase the turbine efficiency and output power. Almost output power is achieved at Stage 1. Therefore, optimum design of the nozzle shape is necessary to improve the turbine performance. Recirculation flow in the runner passage decreases the turbine efficiency and output power because the flow make hydraulic loss and collision loss in the region. Air should be put into the runner passage and the recirculating flow should be suppressed by the air layer in the runner.

Effect of nozzle shape on the performance of high velocity oxygen-fuel thermal spray system

Numerical analysis is performed to predict the gas dynamic behaviors in a HVOF (high velocity oxygen-fuel) thermal spray gun in which oxygen and fuel are burnt in combustion chamber linked to nozzle. The analysis is applied to investigate the axisymmetric, steady-state, turbulent, and chemically combusting flow both within the torch and in a free jet region between the torch and the substrate to be coated. The combustion is modeled using a single-step and eddy-dissipation model which is assumed that the reaction rate is limited by the turbulent mixing rate of fuel and oxidant, or the reaction is instantaneous as the reactants are mixed together. The computational fluid dynamics (CFD) model is also used to elucidate the effect of various nozzle configurations. Using a commercial code, FLUENT which uses FVM (finite volume method) and SIMPLE algorithm, governing equations have been solved for the pressure, velocity and temperature distributions in the HVOF thermal spray gun.

파력발전용 횡류형 수력터빈의 노즐형상에 관한 연구

The purpose of this study is to examine the effect of nozzle shapes on the performance and internal flow characteristics of a cross-flow type hydro turbine for wave power generation. The performance of the turbine is calculated with the variation of rotational speed for 4 types of the nozzle shape using a commercial CFD code. The results show that nozzle shape should be designed considering available head of the turbine. Best efficiencies of the turbine by 4 types of the nozzle shape do not change largely but overall performances varies mainly by the nozzle width. The output power of the cross-flow type hydro turbine changes considerably by the nozzle shape and a partial region of stage 2 in the runner blade passage produces maximum regional output power in comparison with the other runner blade passage areas.

Micro Cutting of Thin Copper Plate by Fiber Laser with Laval Nozzle

Fiber laser has many advantages such as compact size, high conversion efficiency, good beam mode, air cooling and maintenance free. Therefore, it has high possibility as an industrial light source in the near future. The beam from fiber laser can be focused in a micro spot because of its excellent beam quality. However, the narrow kerf leads to the difficulty of outflow of melted material. Therefore, micro cutting by a single-mode fiber laser is considerably difficult, then the high performance nozzles are strongly required. In the previous work, authors developed a high performance nozzle, which can increase the velocity of assist gas flow and makes it possible to reduce the dross in the micro kerf. Therefore, high performance cutting by a single-mode fiber laser can be expected by using our newly designed nozzle. In this study, the effect of nozzle shape on the machining results in precision cutting of thin copper plate by a Q-switched single-mode fiber laser was experimentally investigated. It was found that the high speed cutting at 30mm/s could be carried out by the high performance nozzle under low pulse frequency condition. Besides, the reduction of the dross and good kerf shape could be attained in the case of nitrogen assist gas.

The Effect of Nozzle Shape on Bubble Formation from a Downward Nozzle

AbstractA lot of research has been conducted on the gas injection methods; especially bubble formation from the upward orifice or nozzle, whereas few studies on bubble formation from the downward nozzle have been reported. In this study, the effects of both nozzle shape and diameter on the bubble formation mechanism from the vertically downward nozzle were investigated. The theoretical results obtained by applying the revised two‐stage spherical bubble formation model for the downward nozzle was compared with the experimental results for small metal downward nozzles. The bubble formation mechanism and the bubble size were influenced by the edge angle and diameter of the nozzle, respectively, and the gas flow rate.

Bubble formation mechanism from downward nozzle—Effect of nozzle shape and operating parameters

To achieve a complete resolution system of organic chlorinated compounds, the gas absorption of organic chlorinated compound gas into a molten salt has been considered. In this process the dispersion of gas bubbles in molten salts has played an important role for the efficient mass and heat transfers. The common dispersion method is blowing the gas bubbles through nozzles or orifices submerged in liquids. Much research has been done on bubble formation from upward nozzles or orifices in liquids, while little has been known about the bubble formation from downward nozzles. The purpose of the present study is to investigate the effects of nozzle shape and operating parameters on bubble formation mechanism from the vertically downward nozzle. As a result, the bubble formation and the bubble size are influenced by the edge angle of nozzle, inner and outer diameters of nozzle, and gas flow rate, whereas the gas chamber volume hardly influences on the bubble size.

Effects of nozzle shape on the interruption performance of thermal puffer-type gas circuit breakers

During the last decade the advanced interruption techniques, which use the arc energy itself to increase the pressure inside a chamber by PTFE nozzle ablation, have displaced the puffer circuit breakers due to reduced driving forces and better maintainability. In this paper, we have investigated thermal flow characteristics inside a thermal puffer-type gas circuit breaker (GCB) by solving the Navier–Stokes equations coupled with Maxwell's equations for considering all instability effects such as turbulence and Lorentz forces by transient arc plasmas. These relative inexpensive computer simulations might help the engineer researching and designing new advanced interrupters in order to downscale and uprate high-voltage gas-insulated switchgear (GIS) integral.

Experimental investigation of the effect of nozzle shape and test section perforation on the stationary and non-stationary characteristics of flow field in the large transonic TsAGI T-128 Wind tunnel

AbstractThe results are presented for a cycle of experimental investigations of flow field characteristics (static pressure distribution, static pressure fluctuations, upwash, boundary-layer parameters) in the perforated test section of the transonic TsAGI T-128 Wind Tunnel. The investigations concern the effect of nozzle shape, wall open-area ratio, Mach and Reynolds numbers on the above-outlined flow characteristics. During the tests, the main Wind-tunnel drive power is measured. Optimal parameters of the nozzle shape and test section perforation are obtained to minimise acoustic perturbations in the test section and their non-uniformity in frequency, static pressure field non-uniformity, nozzle and test section drag and, accordingly, required main Wind-tunnel drive power.

Effects of Anode Nozzle Geometry on Ambient Air Entrainment Into Thermal Plasma Jets Generated by Nontransferred Plasma Torch

Summary form only given, as follows. In plasma spraying, higher temperature and velocity of thermal plasma jets are preferable for producing high qualities of protective coatings for their industrial uses, because the sprayed coating powders are melted and accelerated in the plasma flame ejected from a non-transferred DC arc torch through an ambient air toward a substrate. In the typical plasma spray process operated under an atmospheric-pressure condition, the entrainment, of ambient air into the thermal plasma jet is inevitable. An air inflow to the flame alters chemical compositions of the plasma species, cools the thermal plasma flame, and decreases the jet velocity. Furthermore, the dissociation of entrained air enhances the specific heat of plasma, and then the plasma temperatures decrease even when operation power level of the plasma torch is not changed. Consequently, the gradients of temperature and velocity in the plasma jet increase with the degree of air entrainment. Therefore, the ambient air entrainment should be controlled to the lower degree for getting the better quality of coating products with higher purity, density and bond strength. In this experimental work, the geometrical effects of anode nozzle of the non-transferred plasma torch on the air entrainment are examined by measurements using a quadruple mass spectrometer. Two different types of anode nozzle, i.e., tubular and stepped nozzles are employed for the torch. For each nozzle, air contents in the thermal plasma are measured to find the effects of nozzle geometry on the ambient air mixing with the plasma species. The radial and axial distributions of plasma temperature and velocity are also measured. By analyzing the measured results of the thermal plasma characteristics and the geometrical effects of nozzle shape on the air entrainment, the suitable design requirements of the nozzle are determined for optimal processes of plasma spraying.

Effects of Nozzle Shape on Precision Micro Cutting of Thin Metal Plate by Pulsed YAG Laser

In YAG laser cutting process of thin plate, it is important to understand the assist gas flow from the tip of a convergent nozzle in order to improve the machining accuracy, since melted material is mostly carried away downward by the gas flow. Besides, it is considered that the nozzle shape influences the assist gas flow. In this paper, the effects of the nozzle shape on assist gas flow and machining results in micro machining by a pulsed YAG laser are experimentally investigated. There is an unstable region where the pressure on a workpiece changes periodically regardless of the internal shape and exit diameter of nozzle. The unstable region starts at low cylinder gas pressure and becomes smaller in range with increasing the exit diameter. Under middle and high cylinder gas pressure conditions over 300kPa, height of dross becomes smaller with the increase of the exit diameter for a nozzle of conical internal shape, since the pressure on workpiece increases. Furthermore, when the conical inner wall of nozzle is changed to a convex inner wall, it is possible to reduce the height of dross. Additionally, the height of dross becomes lower, when the curvature of the inner wall increases under the high pressure condition.