Elliptical Nozzle Research Articles

Asymmetric Spray Characteristics According to Y-Jet Nozzle Orifice Shape and Spray Conditions.

The Y-jet nozzle is a twin-fluid nozzle that has a larger operating range and simpler structure than other twin-fluid nozzles. Furthermore, it offers outstanding atomization quality even at low flow rates, mak ing it simple to atomize viscous liquids. However, because of the structure of the Y-jet nozzle, having an asymmetrical spray pattern is limited. Most existing experimental studies focused on the orifice diameter and mixing tube length. In this study, two types of elliptical nozzles and one type of circular nozzle were tested. We found that the elliptical nozzle's asymmetric spray characteristics are different from those of the circular type. Furthermore, it was demonstrated that the spray characteristics were different even in ellipsoids, with only the major and minor axes differing.

Performance of elliptical nozzles on the spray dynamics of convergent and constant section nozzles by means of a [formula omitted] coupled model

In this paper, a computational study on the differences between a convergent and a constant section elliptical nozzle is performed. Coupled internal-external flow simulations were carried out by means of a Σ-Y model experimentally validated. The differences reported in terms of internal flow and spray parameters present the cavitation as an important effect in the elliptical nozzle geometries. The conclusions suggest a mixture improvement potential for the cavitating elliptical nozzles.

Numerical analysis of airflow turbulence intensity effect on liquid jet trajectory and breakup in two-phase cross flow

Spraying liquid jets in the transverse airflow is suitable for creating tiny droplets in the combustion chamber. This paper numerically investigated the effect of airflow turbulence intensity on liquid jet penetration and breakup. The large-eddy simulation method is used for numerical solutions. The level set model and volume of fluid (VOF) model are combined for two-phase crossflow modeling. Elliptical and circular nozzles with different aspect ratios and diameters were used to obtain liquid jet trajectories. Other trajectory equations due to different nozzle shapes were obtained for laminar flow. It is shown that the liquid jet trajectory depends on momentum ratio and dimensionless length. For turbulence flow, as results show, when the turbulence intensity of the transverse airflow increases, the energy in the flow vortexes also increases, so the breakup point approaches the liquid jet location. Also, as the turbulence intensity of the transverse airflow increases, the liquid jet trajectory and its penetration depth are not affected significantly because the dynamic energy of turbulence fluctuations is negligible compared to the air main flow. i.e., at 10 %, turbulence intensity equals 1 percent of the primary energy dynamics of the main flow.

Experimental Study on Water Distribution and Droplet Kinetic Energy Intensity from Non-Circular Nozzles with Different Aspect Ratios

(1) Background: In sprinkler irrigation systems, the water distribution and droplet kinetic energy are affected by the shape of the nozzle. In this paper, the effects of working pressure and aspect ratio (L/D) of circular and non-circular nozzles (diamond and ellipse) on water distribution and droplet kinetic energy intensity were investigated; (2) Methods: The hydraulic performance of a PY15 impact sprinkler with circular and non-circular nozzles was assessed under different working pressures, and the droplet diameter, velocity, and kinetic energy intensity were measured by a 2D video disdrometer. Moreover, the coefficient of variation (CV) and form factor (β) were introduced to represent the water distribution and droplet characteristics; (3) Results: The results revealed that, under the same working pressure, the CV of the diamond nozzle was the smallest compared with that of the circular and elliptical nozzles, reflecting a more uniform water distribution. The uniformity of water distribution was the best when the L/D of the elliptical nozzle was the smallest. In general, the larger the outlet diameter, the larger the wetted radius and water application rate. In addition, the smaller the L/D, the smaller the peak water distribution value and the radial increase of the kinetic energy intensity of a single nozzle. The maximum droplet kinetic energy per unit volume of the elliptical nozzle was the smallest compared with that of the circular and diamond nozzles. The circular nozzle at 200 kPa and the diamond and elliptical nozzles at 100 kPa obtained the highest uniformity coefficients of combined kinetic energy intensity distribution, which were 55.93% (circular), 67.59% (diamond), and 57.78% (elliptical) when the combination spacings were 1.0 R, 1.1 R and 1.2 R, and 1.0 R, respectively. Finally, the fitting function of unit volume droplet kinetic energy, distance from the nozzle, L/D, and working pressure of non-circular nozzles was established, and a fitting coefficient of 0.92 was obtained, indicating that the fitting equation was accurate; (4) Conclusions: At low working pressures, the elliptic and diamond nozzles showed better water distributions than the circular nozzle. The distal average droplet diameters of the sprinkler with non-circular nozzles were found to be smaller than those produced by the circular nozzle.

Effect of Special-Shaped Nozzle Structure on Water Jet Performance

The impact force and effective impact area of are water jet are two important indexes for evaluating jet performance, and the outlet shape of the nozzle has a great influence on jet performance. In this study, five nozzles with different outlet shapes were designed, and water jet test experiments were conducted at different inlet pressures using an independently built water jet impact test platform, and the influence law of nozzle shape on the center impact pressure and flow coefficient of the water jet was investigated. The influence of nozzle shape on the effective impact area and entrainment rate of water jet was further investigated by numerical simulation. The results showed that the center impact pressure of the circular nozzle was the greatest when the inlet pressure and the target distance were small. The center impact pressure, the flow coefficient, and the effective area of the triangular nozzle with sharp edges were better than the traditional circular nozzle when the inlet pressure and the target distance were increased. Although the center impact pressure of the square nozzle is lower than that of the circular nozzle, its flow coefficient and effective impact area are higher than those of the circular nozzle with increasing target distance. The water jets of the elliptical and cross nozzles were the most divergent, and the jet performance was poor.

Experimental study on the combustion, emissions and fuel consumption of elliptical nozzle diesel engine

A series of experiments are carried out to investigate the combustion, emissions characteristics and fuel consumption of a diesel engine equipped with elliptical nozzle. The elliptical holes, which are made with an aspect ratio of 1.5, have a similar flow area as that of the references. In-cylinder pressure, exhaust emissions and fuel consumption are measured with varied fuel injection timing under a constant speed and different loads. The elliptical nozzles are characterized by shorter ignition delays, lower maximum rates of heat release and in-cylinder average temperature, and longer combustion durations. The NOx emission of the ICE with an elliptical nozzle is lower and while Soot emission higher. Under variable fuel injection timing, the NOx-Soot trade-off are affected by the nozzle shape. A substantial improvement in the fuel consumption-NOx emission trade-off is obtained for elliptic nozzles at three different loads. Employing moderate earlier injection couple with elliptical nozzle can reduce fuel consumption 2.5% while NOx and Soot emission remain unchanged at 25% load, and NOx emission reduce by 8.3% and 12.7%, and Soot emission reduce by 5.7% and 10.9%, and fuel consumption reduce by 2.4% and 1.7% at 50% and 75% load respectively.

Near Field Decay of Mach 2 Elliptical Jet in the Presence of Tangentially Injected Secondary Swirling Flow

This investigation explores the mixing promoting capability of tangentially injected secondary swirling flow on a Mach 2 elliptical jet issuing from an elliptical nozzle of aspect ratio 2. A detailed three-dimensional numerical analysis was carried out for the combination of different levels of pressure gradient at the nozzle exit and five swirl numbers. Reynolds-Averaged Navier-Stokes equation along with Shear Stress Transport model was solved to predict the flow filed. The presence of secondary swirling flow created large pressure gradient in the direction perpendicular to jet axis, resulting in enhanced mass entrainment leading to high spread of the controlled jet compared to the uncontrolled jet. Also, the secondary jet increased the turbulence level in the flow field for all the cases studied compared to that of free jet case, leading to a reduction in jet core length. The swirl number and the pressure gradient at the nozzle exit is found to have a strong effect on the core length reduction. A maximum of about 70% reduction in core length was achieved for nozzle pressure ratio 4 with secondary flow of swirl number 5.

Shock-cell spacings of underexpanded sonic jets emerging from elliptic nozzles

Shock-cell spacings of underexpanded sonic jets emerging from elliptic nozzles

Effects of circular and non-circular nozzle exit geometries on subsonic and supersonic jet propagations

The mixing enhancement and core length reduction of a jet without significant loss of thrust are essential for reducing infrared radiation, mitigating aeroacoustic noise, improving combustion characteristics, and thrust vectoring. The jet mixing can be improved by manipulating the flow behavior. In subsonic and sonic jets, the flow manipulation may be achieved by utilizing nozzles with non-circular geometries that shed vortices of varying size due to their non-uniform azimuth curvatures. Non-uniform vortices generate differential spreading along the nozzle’s perimeter, causing axis switching and improving entrainment characteristics. Therefore, the present study examines the effects of two non-circular nozzle exit shapes (elliptic and square) on the mixing augmenting efficacy at subsonic and sonic flow conditions. The circular nozzle is tested for comparison. Both quantitative and qualitative analyses evaluate the efficacy of nozzles with non-circular exit geometries. Among the configurations investigated, the elliptic nozzle is superior in shortening the potential core length and enhancing the jet spread. A maximum reduction of 18.75% in core length with rapid jet decay was accomplished with the elliptic nozzle. The measurement of pressure profiles at different streamwise locations reveals that the spread rate is greater for elliptic and square jets than their circular counterpart. The elliptic jet exhibits the highest spread along the minor-axis direction compared to the major-axis direction. The differential jet spread rate in the elliptical jet causes an early axis-switching––direct evidence of mixing augmentation. Shadowgraph images show the asymmetric pattern of shock cell structures and differential spreading in elliptic and square jets.

Effect of Nozzle Outlet Type on the Flow Field Velocity and Impact Pressure of High-Pressure Water Jet Peening

Abstract Water jet peening can effectively improve the fatigue strength of metal materials, and the outlet shape of nozzle greatly affects the effect of water jet peening. In this paper, the effects of nozzle outlet shape on water jet velocity and impact pressure are studied by numerical simulation, and the jet velocity and dynamic pressure for different standoff distances are also discussed. The results show that the water jets of square, circular, and triangular nozzles are highly concentrated, and the water jet of elliptical nozzles is the most divergent. The axial velocity attenuation of the square nozzle along the axis is slower than that of the other three nozzles. The water axial velocity of the elliptical nozzle attenuates fastest, and the length of the core segment of the water jet is the smallest. Within a certain axial distance, the dynamic pressure area in the central area of the elliptical water jet is obviously larger than that of the other three nozzles, and the effective treatment range is large, which is more suitable for the welding surface strengthening operation.

Far-field pressure measurements of elliptic jets discharged close to a wing

This paper presents a preliminary experimental investigation into the acoustics of two elliptical jet nozzles installed close to a wing model. Acoustic pressure data is obtained for a range of observer polar angles mounted in the far field of the jets. Three nominal jet Mach numbers, namely 0.4, 0.6 and 0.8 are studied. Results suggest that the elliptic jets surveyed provide a noise reduction of the jet-surface installation noise source. The noise reduction is maximum in the forward arc and in the order of 1 dB for the fully-corrected overall sound pressure level data. Additionally, the noise benefit exists only when the minor axis of the elliptical nozzle is mounted parallel to the wing trailing edge. It is hypothesised that the reduction in the jet plume cross-section width limits the scattering of the near pressure field by the wing trailing edge to a lower frequency range. The jet mixing noise source, however, is seen to increase with decreasing nozzle exit-plane aspect ratio. The three jet velocities surveyed suggest the consistency of the key results discussed in the paper. Investigation of the jet turbulent flow structures and jet near pressure field is under way.

A new calculation formula to describe the dynamic pressure of water jet peening with elliptical nozzle for high-efficiency treatment

Water jet peening is a good potential method to control welding residual stresses. The water jet with elliptical nozzle can improve the treatment efficiency due to its large treatment area. In this article, the water jet velocity and dynamic pressure for different elliptical nozzle dimensions and standoff distances are discussed by numerical simulation. The results show that when the axial distance is 10 mm, the effective impact diameter of the elliptical nozzle a/b=8–12 is about 2 times or more than that of the circular nozzle. The length of the jet core of the elliptical nozzle is only related to the outlet structure and is independent of the inlet pressure. The correlation between the dimensionless core length of the elliptical water jet and its long and short axes is derived. When the ratio of the major axis to the minor axis is between 7 and 13, the core length of the elliptical water jet is 7–7.5 times that of its minor axis. Combining the suitable treatment area and dynamic pressure, the elliptical nozzle with an axis ratio of 8 is recommended to control the welding residual stress. Finally, a new formula for calculating dynamic pressure distribution is proposed for the elliptical nozzle water jet at different stages.

Analysis of elliptical diesel nozzle spray dynamics using a one-way coupled spray model

The elliptical nozzle has the potential ability to increase the air-fuel mixture quality. A one-way coupled spray model and Homogenous Relaxation Model (HRM) was adopted to investigate the spray behaviors and the air-fuel mixture progress in real diesel combustion chamber with the application of elliptical and circular diesel nozzle. The results indicated that the spray cone angle and the air entrainment mass of elliptical nozzle were larger than that of the circular nozzle, while the spray penetration of the elliptical nozzle which the aspect ratio is 1.5 and 2 was shortened by 11% and 8.3% as compared to circular spray respectively. Also, the air entrainment mass of the elliptical spray with a ratio of 1.5 and 2 increased by 60% and 35% as compared with circular spray respectively. Furthermore, the partial equivalent ratio and the high concentration area in the cylinder is reduced for elliptical nozzle, and the air-fuel mixture is more uniform. The fuel evaporation rate of elliptical spray is always higher than that of the circular spray.

Droplet distribution characteristics of impact sprinklers with circular and noncircular nozzles: Effect of nozzle aspect ratios and equivalent diameters

An experiment was carried out to investigate the droplet distribution characteristics of an impact sprinkler by using circular and noncircular nozzles. The noncircular nozzles used were selected by employing the principle of an equal flow rate under the same pressure. Using a two-dimensional video distrometer (2DVD) technique, the diameter, velocity, and kinetic energy of the droplets were measured. Due to its specific geometric structure, the sprinkler with elliptic and rhombic nozzles showed better water distribution than those having a circular nozzle at low working pressure. The mass mean droplet diameters of the sprays produced by the sprinklers with the noncircular nozzles were significantly larger than those produced by the circular nozzle in the near and middle ranges of the wetted radius. Coarse droplets were observed from rhombic nozzles at distal points but the droplet velocities were similar to those close to the sprinkler. A logarithmic model was developed to describe the relationship between diameter and velocity, and this model fitted with a correlation coefficient (R2) of 0.99. The kinetic energy intensity increased gradually with the distance from the sprinkler and rapidly decreased at the end of the sprinkler wetted radius. Under working pressures of 150 and 200 kPa, the uniformity coefficients of kinetic energy intensity were simulated for a rectangular combination spacing of the sprinkler with elliptic and rhombic nozzles using MATLAB. The optimum combination spacing was found to be 1.0 times the wetted radius, and the uniformity coefficients for kinetic energy intensity were 57.0, 57.1, 60.5, and 65.4%. The results provide valuable data for studying the external spraying characteristics of sprinklers and for optimising nozzle structures and irrigation systems.

Heat transfer characteristics of flat and concave surfaces by circular and elliptical jet impingement

ABSTRACT The present paper reports the thermal behavior of flat and curved surfaces with impinging jets employing circular and elliptical nozzle for identical equivalent diameter (de). Tests are performed with the Reynolds number varying from 11,250–22,500, varied range of plate to nozzle distance (z/d = 1–6), various nozzle aspect ratios (AR = 1–4). A comparison of thermal behavior between flat and concave surfaces (d/D = 0.05) is discussed in this study. The maximum enhancement in the stagnation Nusselt number found to be 27.4% and 24.8% with the increase in AR = 1 to 4 for flat surface, curved surface, respectively.

Spray Characterization of Elliptical Diesel Nozzles Using Hybrid VOF-to-DPM Transitional Approach in Large Eddy Simulation (LES) Framework

Spray Characterization of Elliptical Diesel Nozzles Using Hybrid VOF-to-DPM Transitional Approach in Large Eddy Simulation (LES) Framework

Geometrical inlet effects on the behavior of a non-premixed fully turbulent syngas combustion; a numerical study

This study numerically evaluates a three-dimensional, turbulent, non-premixed syngas (a mixture of H2 and CO) flame issued from a round nozzle. The flow Reynolds number on the basis of the inlet velocity and the nozzle diameter is 16,700 and the flame is shrouded by a coflow under atmospheric conditions. A computational tool with a modified k-omega turbulence model and eddy dissipation model is used for simulating the reacting flow and its immediate surroundings. The outcomes are first compared against the existing experimental data. This reveals that when β*, as a constant coefficient in the k-omega turbulence model, is 0.073, the numerical results match the experimental data with high accuracy. Subsequently, the effects of variations in the diameter of the inlet nozzle and its geometry are investigated. This shows that an increase in the inlet nozzle diameter leads to the downstream movement of the high-temperature region diminishing combustion efficiency. Importantly, it is shown that using the elliptical inlet nozzle with the large diameter of 1.2 based nozzle diameter (4.48 mm) assists the combustion performance and increases the maximum combustion temperature by up to 9.6%. It also results in a considerable reduction of the unburned fuels and enhances the flow residence time significantly.

Experimental study on the influence of the injection structure on solid scramjet performance

Injection structures can affect the ignition and combustion of fuel and supersonic air in scramjets, strongly impacting their performance. The influence of three different injection structures on the performance of a solid scramjet was investigated using direct-connect tests. The experiment employed a boron-based fuel-rich propellant and simulated a flight Mach number 5.6 at 25 km. The results show that, compared to a circular nozzle (test no.1), the elliptical nozzle (test no.2) can significantly improve the ignition and combustion of the fuel-rich mixture produced in the gas generator. This improvement is even more significant when a two-stage elliptical nozzle is adopted (test no. 3). The combustion of the fuel-rich mixture presents the typical cycle of establishment, development, maintenance, and decay. The wall ablation area and particle deposition distribution, show that the gaseous components in the fuel-rich mixture burn rapidly, and that particles deposition increases when an elliptical nozzle is used. The combustion efficiency of test no.3 reached 0.60, which is larger than the 0.48 obtained during test no.1. The low particle combustion efficiency is a key factor limiting solid scramjets performance.

The influence of elliptical and circular orifices on the transverse jet characteristics at supersonic crossflow

The using of an elliptical nozzle has been considered as a potential method for improving the air-fuel mixing and atomization quality. The present paper focuses on the transverse jet breakup behaviors and droplet size distribution for circular and elliptical orifices in supersonic crossflow on a pulse wind tunnel test platform, and the laser based pulsed laser background imaging method and high-speed spray particle size analyzer were adopted. The results show that the jet penetration depth of elliptical 4 (Aspect ratio of 4) orifice is always smaller than that of the circular orifice. Another interesting finding is that the difference of the jet penetration depth between the circular and elliptical 4 orifices decreases with the increase of injection pressure. Moreover, the jet surface wave number of the elliptical orifice is more than that of the circular jet, and the elliptical jet surface wave length is smaller than that of circular one. Additionally, the spray Sauter Mean Diameter (SMD) of elliptical 4 nozzle is 14.5% smaller than the circular spray at injection pressure of 5 MPa, and the elliptical 4 spray also has the smallest Dv50 and Dv90 among other orifices. Because elliptical 4 jet held larger windward surface area, which is helpful to increase the shear action of supersonic crossflow. Furthermore, the elliptical 4 spray produces the smallest droplet diameter at the largest volume fraction, and also the elliptical 4 spray has the smallest span of droplet diameter distribution than other orifices.

Scaling law for supersonic core length in circular and elliptic free jets

We present here the experiments demonstrating the scaling law for supersonic core length in circular and elliptic free jets. A proper scale for the supersonic core length of free jets is found as Lc*AR e−0.11γMj2, where Lc* is the core length normalized by nozzle throat diameter Dth, AR is the aspect ratio of the elliptic nozzle, γ is the specific heats ratio, and Mj is the ideally expanded jet Mach number. The scaling law developed for supersonic core length shows a close dependence with nozzle expansion ratio pe/pa and agrees well with the results reported in open literature, including the data reported for γ = 1.28–1.67. In spite of their uniqueness, the present results refer to circular and elliptic jets only. Thus, other similar studies on rectangular and square jets for a wide range of parameters are needed for a full comprehension of the universality of the scaling law for non-circular jets.