Influence Of Nozzle Geometry Research Articles

Study on the spray characteristics of transverse jets with elliptical nozzles in supersonic crossflows using the volume of fluid–discrete phase model

The atomization characteristics of liquid jets injected transversely into a supersonic crossflow significantly affect the performance of scramjet engines. Existing research on this topic has mainly focused on circular nozzles, while the influence of nozzle geometry, particularly elliptical nozzles, has received relatively limited attention. Therefore, this study employs a numerical simulation method coupling the volume of fluid and discrete particle model to investigate the breakup and atomization characteristics of transverse liquid jets from elliptical nozzles with different aspect ratios under supersonic crossflow conditions, as well as the total pressure loss. The simulation model is validated against experimental data obtained from a pulse wind tunnel, including measurements of the liquid jet penetration depth and the Sauter mean diameter (SMD). The results indicate that for elliptical nozzles with an aspect ratio (AR) greater than 1, columnar breakup occurs earlier, and the columnar breakup length is shorter compared to circular nozzles. As the AR increases, the jet penetration depth decreases, while the spray expansion angle increases. Furthermore, the SMD of the atomized spray field from the circular nozzle is larger than that from the elliptical nozzles, and the SMD of the spray field is smallest for an elliptical nozzle with AR of 4. Finally, the elliptical nozzles exhibit a higher total pressure recovery coefficient, indicating reduced total pressure loss in the combustion chamber. This reduction in pressure loss is expected to improve the thrust performance of the scramjet engine.

Investigating the effect of deicing parameters using high-pressure water jet

Maritime operations are impacted by ice accretion on decks, bulkheads, and offshore structures during the winter or in extremely frigid climates. In most cases, the traditional method of deicing maritime vessels is human labor, which requires enormous effort and lengthy hours for unsatisfactory results, particularly when the ice adhesion strength is high. This study experimentally examined combined effects of operational parameters, including operating pump pressure, nozzle geometry, water jet temperature, standoff distance, and time of cut, on the depth and width of a cut through an ice block. In comparison to other parameters, the influence of nozzle geometry on both the width and depth of cut was found to be more significant, with R-squared values of 85% and 62% respectively. Increasing the depth and width of the cut facilitated the delamination and disintegration of ice from an aluminum mold. This indicates that water jet deicing on maritime vessels could be effective, therefore achieving the objective of this study. The optimization of operational parameters is used to develop a cuttability chart for various thicknesses of accumulated ice on marine vessels.

Influence of Nozzle Geometry and Scale-Up on Oil Droplet Breakup in the Atomization Step during Spray Drying of Emulsions

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.

Influence of nozzle geometry on screech instability closure

The effect of nozzle exit geometry on the triadic interactions between convective Kelvin–Helmholtz instabilities and the quasi-steady shock structure of supersonic jets is discussed in this study. A circular and rectangular nozzle with an aspect ratio (AR) of 2 were evaluated using results from near field acoustics and high-speed Schlieren images. The study investigated different types of screech instabilities in both nozzle configurations, including the multimode instability in rectangular jets. The near field acoustic measurements showed comparable trends in screech staging in both nozzle configurations. The Schlieren results revealed that the standing waves in the jet near field were influenced by the oscillation mode of the jets. The study also explored a new technique of noise visualization from Schlieren images based on near field acoustics and temporal Fourier decomposition. Spatial Fourier decomposition demonstrated that the resonance closure mechanism across both nozzle configurations was dependent on the relative influence of the first two shock cells. Comparisons between the AR 2 and AR 9 jet showed that jet aspect ratio can significantly affect the energy distribution from the triadic interactions.

Influence of nozzle geometry on torch parameters during gas combustion

In this paper, when performing and analyzing the series of calculated results of the analysis of the sides of a rectangular nozzle for the parameters of a turbulent free air jet and a flame of a propane-butane mixture based on three-dimensional parabolic Navier-Stokes bonds for multicomponent reacting jets. To estimate the turbulent viscosity, differential equations of the kinetic and dissipation of the kinetic energy of turbulence are observed with refined empirical constants that are acceptable in turbulent combustion, as in the calculations, the initial values of the kinetic energy of turbulence did not exceed 5% of the dimensionless velocity of the main jet. It was found that when an air jet flows out of a nozzle with an aspect ratio of (1:2) and (1:4) in the initial sections of the jet, its shape behaves like an ellipse and, with the distance, it turns into a round one, with dimensionless, x greater or equal to 20 for the nozzle (1:2) and x greater or equal to 30 for (1:4), and for this variant there is again a transition to an elliptical shape. Studies of the diffusion combustion of a propane-butane mixture flowing out of a rectangular nozzle with an aspect ratio of (1:2) and (1:4) showed that with the ratio of the speed of the oxidizer to fuel mu, the flame length increases when mu between 0 and 0.164, and then, with an increase of mu more than 0.41, the torch length is shortened. The axial distributions of the momentum flux density with the aspect ratio (1:4), the jet core is shortened by 2÷2.5 times, compared with the aspect ratio (1:2) with the other parameters unchanged. Setting the tangential velocity at the mouth of the nozzle (ω=6.1 m/s) leads to a decrease in the torch length by 11% compared to its value equal to zero.

Influence of nozzle geometry on spray and combustion characteristics related to large two-stroke engine fuel injection systems

As emission regulations for large two-stroke marine Diesel engines increase as well, the manufacturers face similar problems as small-sized engine builders. The fuel injection, spray formation and subsequent combustion process remain among the main drivers for emissions of direct-injection, compression-ignition internal combustion engines. Since the fuel injection nozzle design of large two-stroke marine Diesel engines differs significantly, not only in size but especially regarding their non-symmetricity and eccentrical orifice arrangement, compared with four-stroke engines, the bulk of research available related to this topic is very limited.To further deepen the understanding of how in-nozzle cavitation flow during the fuel injection process affects the combustion behaviour in large two-stroke marine Diesel engines, transparent nozzle geometries have been used to link the cavitation phenomena with spray and combustion characteristics. A total of six single-orifice nozzles based on the original five-orifice nozzle design of large two-stroke marine Diesel fuel injectors, with and without hydro-erosive grinding, have been experimentally investigated under realistic engine conditions using highspeed optical measurement techniques and a unique constant-volume spray chamber that geometrically represents a combustion chamber of a large two-stroke marine Diesel engine at top dead centre.The spray morphology and combustion results reveal significant differences between the non- and hydro-erosive ground nozzle geometries. While the standard and angled nozzle versions remain similar, the eccentrical nozzle with its distinctive in-nozzle swirl cavitation pattern behaves differently, leading to a very reliable start of ignition behaviour and extreme wide spray angle.

Influence of Nozzle Type, Divergence Angle and Area Ratio on Impulse of Pulse Detonation Engine

The influence of nozzle geometry on the impulse produced by the single cycle Pulse detonation engine (PDE) was experimentally investigated. For each experiment the nozzles were attached at the end of the engine. The impulse produced by the pulse detonation engine was calculated from the measured thrust. The thrust measurement was done by sliding the engine on the central bar of the thrust stand. The main structure of the basic PDE has a detonation tube with one terminal closed, a Schelkin spiral used as deflagration to detonation device, and a thrust stand to support the structure. Stoichiometric acetylene and oxygen mixture were used as detonation mixture. Various nozzles with a range of divergent angle and area ratios were tested. The calculations of the impulse were made from the thrust pulse for the duration it lasted. The effect of the type of nozzle, divergent angle and area ratio were observed. The bell shaped nozzle with large angle of divergence produced maximum specific impulse of 80 Sec with 20° divergence angle and area ratio of 6.942; maximum impulse was produced by the bell shaped nozzle with a small area ratio of 2.969 and 10° divergence angle. The maximum total impulse obtained was 1200 N-sec.

Influence of nozzle geometry on primary and large-scale instabilities in coaxial injectors

Detailed knowledge on liquid jet instabilities is important to improve the performance of coaxial injectors, which find wide range of industrial applications. The present paper aims to investigate the influence of nozzle exit geometry on jet instabilities during the unsteady primary jet breakup process in liquid-centered coaxial injectors. Time resolved images of the liquid jet were processed to characterize Kelvin–Helmholtz instability close to the nozzle exit and flapping instability near the jet breakup location for three different nozzles with different liquid-to-gas cross-sectional area ratio (AR) and lip thickness to diameter ratio (LTR) of the central tube. The results showed considerable effect of AR and LTR on both primary and large scale instabilities as well as jet breakup length and morphology. It is found that the injector exit geometry plays a crucial role in triggering the interfacial disturbances as it conditions the liquid and air flow prior to their interaction.

On the influence of nozzle geometry on jet diffusion flames under cross-wind

Four nozzle types were used to investigate the blow-out limit, flame shape, flame mean length, and flame tilt angle of jet diffusion flames under cross-wind conditions. The experimental results revealed that the nozzle geometry had a minor influence on the flame blow-out limit when the fuel jet velocity was low. As the fuel jet velocity increased, the nozzle geometry had a significant influence on the flame blow-out limit, the blow-out velocity of the triangle nozzle was the maximum, and the rectangular nozzle was minimum. The nozzle geometry had a significant influence on the down-wash and lift-off of the flame under cross-wind conditions. The triangle nozzle was prone to the appearance of the down-wash phenomenon, and the rectangular nozzle flame easily exhibited the lift-off phenomenon. Additionally, the effect of the nozzle geometry on the flame blow-out limit and flame shape was explained from a moment of inertia viewpoint. The flame length of the rectangular and cross nozzles monotonously increased with the increase of the momentum flux ratio of the fuel jet to the cross-wind. However, two growth curves occurred as the flame length of the circle and triangle nozzles increased with the momentum flux ratio of the fuel jet to the cross-wind. Additionally, for the jet diffusion flames under cross-wind conditions, the nozzle geometry exerted a smaller effect on the flame tilt angle.

The influence of nozzle geometry on the gas-dynamic structure of the supersonic nonisobaric jet

The paper presents the investigation results of the flow structure of cold supersonic jets flowing out of model nozzles with a Mach number on the exit Ma = 3.5: an axisymmetric nozzle, a nozzle with a rectangular critical section, a beveled nozzle with a rectangular critical section. Flow schlieren images and transverse measured total pressure profiles in the flow are presented. The influence of the critical section shape and the beveled exit section on the shock-wave structure of the flow is described.

Insights into the radial water jet drilling technology – Application in a quarry

In this context, we applied the radial water jet drilling (RJD) technology to drill five horizontal holes into a quarry wall of the Gildehaus quarry close to Bad Bentheim, Germany. For testing the state-of-the-art jetting technology, a jetting experiment was performed to investigate the influence of geological heterogeneity on the jetting performance and the hole geometry, the influence of nozzle geometry and jetting pressure on the rate of penetration, and the possibility of localising the jetting nozzle utilizing acoustic activity. It is observed that the jetted holes can intersect fractures under varying angles, and the jetted holes do not follow a straight path when jetting at ambient surface condition. Cuttings from the jetting process retrieved from the holes can be used to estimate the reservoir rock permeability. Within the quarry, we did not observe a change in the rate of penetration due to jetting pressure variations. Acoustic monitoring was partially successful in estimating the nozzle location. Although the experiments were performed at ambient surface conditions, the results can give recommendations for a downhole application in deep wells.

Effect of Channel Geometry and Properties of a Vapor–Gas Mixture on Volume Condensation in a Flow through a Nozzle

A method of direct numerical solution of the kinetic equation for the droplet size distribution function was used for the numerical investigation of volume condensation in a supersonic vapor–gas flow. Distributions of temperature for the gas phase and droplets, degree of supersaturation, pressure, fraction of droplets by weight, the number of droplets per unit mass, and of the nucleation rate along the channel were determined. The influence of nozzle geometry, mixture composition, and temperature dependence of the mixture properties on the investigated process was evaluated. It has been found that the nozzle divergence angle determines the vapor–gas mixture expansion rate: an increase in the divergence angle enhances the temperature decrease rate and the supersaturation degree raise rate. With an increase or decrease in the partial pressure of incondensable gas, the droplet temperature approaches the gas phase temperature or the saturation temperature at the partial gas pressure, respectively. A considerable effect of the temperature dependence of the liquid surface tension and properties on gas phase parameters and the integral characteristics of condensation aerosol was revealed. However, the difference in results obtained with or without considering the temperature dependence of evaporation heat is negligible. The predictions are compared with experimental data of other investigations for two mixtures: a mixture of heavy water vapor with nitrogen (incondensable gas) or n-nonane vapor with nitrogen. The predictions agree quite well qualitatively and quantitatively with the experiment. The comparison of the predictions with numerical results from other publications obtained using the method of moments demonstrates the usefulness of the direct numerical solution method and the method of moments in a wide range of input data.

Influence of Nozzle Shape on the Performance of Low-Power Ar Plasma Jet

The influence of nozzle geometry on the properties of atmospheric-pressure Ar plasma jet was investigated. Three different nozzle types were tested: 1) a tapered nozzle (to get a thin plasma plume); 2) a straight nozzle (used in most cases); and 3) an enlarged nozzle (to increase the active plasma area). The electrical properties and visual appearance of the generated plasma were studied with these three nozzles. The jet’s performance for surface modification was evaluated by measuring the area of the samples with enhanced wettability and comparing it with the image analysis of the light emission over the sample surface. It has been concluded that limiting the nozzle diameter can be a solution to reduce the treatment area. However, the decrease in the treated area is limited due to the plasma spreading. The use of widen nozzle leads to increase in the treated area and possibility to control the mixture of the carrier gas with ambient air, making this nozzle configuration potentially interesting for other applications, as, for example, treatment of small 3-D objects.

Investigation of the Growth of Particles Produced in a Laval Nozzle

This study focuses on numerical modeling of condensation of water vapor in a Laval nozzle, using the liquid drop nucleation theory. Influence of nozzle geometry, pressure, and temperature on the average drop size is reported. A computer program written in MATLAB was used used to calculate the nucleation and condensation of water vapor in the nozzle. The simulation results are validated with the available experimental data in the literature for steam condensation. The model reveals that the average drop size is reduced by increasing the divergent angle of the nozzle. The results also confirm that increasing the inlet pressure has a direct effect on the average drop size while temperature rise has an inverse effect on the drop size.

English

This paper presents numerical simulations of synthetic jets in aerodynamic applications. We've analyzed the formation of isolated synthetic jets, the influence of nozzle geometry and the interaction of synthetic jets with a uniform flow on a flat plate. Also we've studied the influence of the active control in interaction with a stalled airfoil and the controllability of dynamic stall phenomenon. The results are obtained using a dedicated CFD solver. Appropriate comparisons are made with results from scientific literature; as well the numerical results are compared with a set of experimental images.

Combination of Visualization Techniques for the Analysis of Evaporating Diesel Sprays

Evaporating diesel sprays from three different multi-hole nozzles have been studied by means of three different and complementary techniques: Mie scattering, double-pass schlieren, and CH radical chemiluminescence. These three kinds of measurements provided valuable information that has allowed us to shed light on the influence of nozzle geometry on the air–fuel mixing and evaporation processes. For this purpose, three six-hole sac nozzles, with different orifice degrees of conicity have been used. These nozzles had been geometrically and hydraulically characterized in a previous publication, where important non-dimensional coefficients describing the nature of the flow have been evaluated. Injection at different pressure conditions has been carried out in an inert environment of gas to study the mixture process, avoiding window fouling by soot deposition from combustion. Studies have been carried out for three different injection pressures and four different gas densities during spray injection, representative of real engine conditions, with changing temperature and pressure in the discharge camera. Liquid-phase penetration and stabilized liquid length for all nozzles and pressure conditions have been determined with the Mie scattering technique. The cylindrical nozzle provided the highest value of the liquid length at a low injection pressure (30 MPa), because of its higher diameter and the absence of cavitation. When the two conical nozzles are compared, no clear differences have been shown between them. Because with this Mie scattering, it is not possible to follow the vapor behavior and considering constraints associated with the geometrical configuration of diesel sprays generated by the multi-hole nozzles, a double-pass schlieren technique has been used for this purpose. The combination of Mie scattering and schlieren allowed for the liquid and vapor phases to be analyzed in terms of penetration. As far as the CH radicals are concerned, these radicals are supposed to appear beyond the position of the stabilized liquid length; however, results show how first CH radical intensity is detected before liquid-phase penetration reaches the stabilized value. When CH radical apparition delays from the start of the injection between all of the nozzles and for all injection conditions are compared, in overall terms, conical nozzles present less delay than cylindrical nozzles. This means that the air–fuel mixing process is more effective in the case of conical nozzles. Thus, the analysis of all of the results made it possible to link the nozzle geometry, fuel–air mixture, spray evaporation, and incipient combustion.

Influence of nozzle geometry on underexpanded axisymmetric free jet characteristics

The effect of nozzle geometry on the structure of a supersonic free jet is investigated both experimentally and numerically for three simple nozzle geometries. In the experiments, the relation between the Mach disk height and diameter and the nozzle pressure ratio are investigated using the schlieren method. In contrast to results obtained in previous studies, our experimental results show that the Mach disk height changes depending on the nozzle geometry. Numerical investigations were conducted by introducing flows upstream of the nozzle and the influence of these upstream flows on free jet configuration has been discussed.

Superheated Atomization: Influence of Nozzle Geometry on Mass Flux and Spray Characteristics

AbstractBei überhitzter Zerstäubung wird die Desintegration des Sprays durch die von thermischer Energie induzierte partielle Verdampfung verstärkt. Der Verdampfungsgrad und die Entstehung großer Einzeltropfen sind von der Düsengeometrie abhängig. Durch Ermittlung der Massenströme und mit optischen Messmethoden werden geometrieabhängige Veränderungen der Strömungscharakteristik und der Spraymorphologie untersucht.

Viscous–inviscid interactions in transonic flows through slender nozzles

Considering the miniaturization trend in technical applications, the need of a slender nozzle theory for such conventional, that is ideal-gas-like, fluids, which accounts for a strong boundary-layer interaction with the core region, arises in quite a natural way as the dimensions of the flow device are successively reduced. Moreover, a number of modern technological processes (e.g. organic Rankine cycles) involve fluids with high molecular complexity, some of which are expected to exhibit embedded regions with negative values of the fundamental derivative in the vapour phase commonly termed Bethe–Zel'dovich–Thompson (BZT) fluids. Linked to it, unconventional Laval nozzle geometries are needed to transform subsonic to supersonic internal flows. In the present paper, the transonic flows through nozzles of short length scales located in a channel of constant cross-section so slender that the flow in the inviscid core region is one-dimensional are considered. Rapid streamwise changes of the flow field caused by the nozzle then lead to a local breakdown of the classical hierarchical boundary-layer approach, which is overcome by the triple-deck concept. Consequently, the properties of the inviscid core and the near-wall (laminar) boundary-layer regions have to be calculated simultaneously. The resulting problem is formulated for both regular (ideal-gas-like) fluids and dense gases. Differences and similarities of the resulting flow pattern with respect to the well-known classical Laval nozzle flow are presented for perfect gases, and the regularizing influence of viscous–inviscid interactions, is examined. Furthermore, the analogous problem is considered for BZT fluids in detail as well. The results indicate that the passage through the sonic point in the inviscid core is strongly affected by the combined influence of nozzle geometry and boundary-layer displacement effects suggesting in turn an inverse Laval nozzle design in order to obtain the desired flow behaviour.

Study of cavitation phenomena based on a technique for visualizing bubbles in a liquid pressurized chamber

In this paper, the influence of nozzle geometry on cavitation and near-nozzle spray behavior under liquid pressurized ambient is studied. For this purpose, eight steel drilled plates, with different diameters and degrees of conicity of their holes, are analyzed. A special near-nozzle field visualization technique, using a test rig pressurized with fuel, is used. Due to the difference in refractive index between liquid and vapor phase, bubbles present at the outlet of the orifice are visualized. The pressure conditions at which bubbles start appearing at the orifice outlet are compared with those at which choked flow appears. The results showed that pressure conditions for inception of cavitation obtained in the visualization tests differs from those seen for choked flow (5–8% in terms of cavitation number). In addition to this, the images taken are analyzed to get the angle of the jet formed by fuel bubbles, showing that it increases significantly for those conditions more prone to cavitate. Furthermore, comparison of bubbles generation when increasing or decreasing backpressure indicates the presence of hysteresis in cavitation inception phenomena.