Breakup Length Of Liquid Sheet Research Articles

The effect of oil-in-water emulsion pesticide on the evolution of liquid sheet rim disintegration and the spraying distribution

Oil-based emulsions often used as agricultural chemical formulations to control pests and weeds. The instability of emulsion spray is an important challenge. In this work, the effects of liquid sheet rim disintegration on spray angle and spraying distribution were studied by visualization method. The results show that the addition of emulsion change the way of rim disintegration and this change may be responsible for the improvement of spray angle and spraying distribution uniformity compared with water spray. In emulsion spray, the typical feature of rim disintegration is the asymmetric “half-moon” shaped holes, which leads to earlier disintegration at the edge of the liquid sheet. The hole coalescence at the rim of liquid sheet may be the reason for the increase of spray angle, because it divides the liquid sheet into small liquid masses and breaks the inward contraction trend of the cohesive attraction of liquid mass. Only 0.02% addition of emulsion, the spray angle could be increased by 8°, the typical liquid sheet breakup length (typical length) and the liquid sheet rim breakup length (rim length) from 23.297 mm to 18.609 mm reduce to 16.3 mm and 9.099 mm, and the spraying distribution curve become more uniform. In addition, the effects of spray structure on spraying distribution characteristics under different concentrations and spray pressures are also discussed. This study could provide a reference for the optimal use of pesticide formulations in the field, the reduction of pesticide waste and environmental pollution, and the establishment of atomization and fragmentation models.

Experimental Study on the Spray and Self-Excitation Oscillation Characteristics of Gas-Centered Coaxial Injectors

The present article studies the spray and self-oscillation characteristics of liquid sheets generated by a series of gas-centered coaxial injectors. An experimental system has been built to investigate the impacts of gaseous core size and recess length on the breakup and self-oscillation features. The results reveal that the gaseous flow shows an apparent impact on the liquid sheet breakup length with a small gaseous core size. The atomization morphology shows the different patterns under varied pressure drops, and the spray angle is increased with larger recess ratios. Besides, there is a low oscillation frequency at which the self-oscillation phenomenon is activated. The smaller gaseous core sizes and shorter recess lengths could promote self-oscillation. The required liquid flow rate for the self-oscillation phenomena could be raised by increasing the gaseous flow rate, while the self-oscillation frequency hardly varies with it.

The effects of alumina nanoparticles as fuel additives on the spray characteristics of gas-to-liquid jet fuels

The use of metal nanoparticles as fuel additives have gained interest due to its positive influence on liquid fuels’ combustion and emission performance. Nanoparticles dispersion affects the hydrodynamic and thermo-physical properties of the liquid fuel, and in turn, its atomization, mixing and evaporation characteristics. This work investigates the influence of nanoparticles dispersion on the spray performance of alternative gas-to-liquid (GTL) jet fuel under atmospheric ambient conditions. The spray characteristics of GTL fuel with dispersed alumina nanoparticles are compared with those of the pure GTL fuel. The spray characteristics at the macroscopic and microscopic levels are measured using the optical diagnostic techniques of shadowgraph and phase Doppler anemometry, respectively. The nanoparticles dispersed in liquid fuel tend to slightly alter the transient nature of the spray formation, enhance the liquid sheet instability and reduce the liquid sheet breakup length when compared to those of the pure GTL fuel. Furthermore, the mean droplet sizes of GTL fuel dispersed with nanoparticles are smaller than those of the pure GTL fuel.

DIRECT SIMULATIONS OF LIQUID SHEET BREAKUP IN PLANAR GAS BLAST ATOMIZATION

High fidelity simulations offer a promising way to study primary breakup of liquid sheets. The present work aims at simulating liquid sheet breakup under the assumption of a 2D planar prefilming gas blast atomization. An in-house finite volume method based solver has been used in the study. Interface tracking is done using volume of fluid (VOF) methodology. The study analyzes the effect of parameters such as inner core gas velocity, outer gas velocity, and liquid sheet thickness on the atomization process. The spray is characterized in terms of liquid sheet breakup length, spray cone angle, and droplet size distribution. The obtained droplet size distribution closely represents lognormal distribution. The inner core gas velocity was found to have significant impact on liquid sheet breakup length and droplet mean diameter within the parametric range of this study. Additionally, increase in liquid sheet thickness has shown an increase in the sheet breakup length.

Effect of Nanoparticles on the Fuel Properties and Spray Performance of Aviation Turbine Fuel

The influence of nanoparticles' dispersion on the physical properties of aviation fuel and its spray performance has been investigated in this work. To this end, the conventional Jet A-1 aviation fuel and its mixtures with alumina nanoparticles (nanofuel) at different weight concentrations are investigated. The key fuel physical properties such as density, viscosity, and surface tension that are of importance to the fuel atomization process are measured for the base fuel and nanofuels. The macroscopic spray features like spray cone angle and sheet breakup length are determined using the shadowgraph technique. The microscopic spray characteristics such as droplet diameter, droplet velocity, and their distributions are also measured by employing phase Doppler anemometry (PDA) technique. The spray performance is measured at two nozzle injection pressures of 0.3 and 0.9 MPa. The results show that with the increase in nanoparticle concentrations in the base fuel, the fuel viscosity and density increase, whereas the surface tension decreases. On the spray performance, the liquid sheet breakup length decreases with increasing nanoparticle concentrations. Furthermore, the mean droplet diameters of nanofuel are found to be lower than those of the base fuel.

Visualization studies of the spray from swirl injectors under elevated ambient pressure

This paper presents the results of a visualization study on spray formed by swirl injectors with different geometries under elevated ambient pressure. A spray test facility with an ambient pressure chamber was constructed, and sprays were recorded using a high-speed camera. The parameters of the spray characteristics, e.g. the spray cone angle and breakup length of liquid sheet, were measured, and the effects of the ambient pressure and injector geometrical parameters on the spray were obtained. Experimental results indicated that when other parameters in the swirl injector remained constant, the increase of ambient pressure caused a decrease in the spray cone angle and the breakup length of liquid sheets. However, the mass flow rates remained nearly constant. An increase in nozzle diameter increased the spray cone angle, and the variation of breakup length according to nozzle diameter was somewhat irregular. The increase in the diameter of the tangential inlet reduced the spray cone angle; the breakup length scarcely varied.

Analysis on the atomization characteristics of aviation biofuel discharging from simplex swirl atomizer

The atomization characteristics of aviation biofuel discharging from a simplex swirl atomizer into quiescent atmospheric air are studied. The aviation biofuel is a mixture of 90% commercially available camelina-derived biofuel and 10% VonSol-53 (aromatics). The experiments are conducted in a spray test facility at varying fuel flow rate conditions. The measured characteristics include atomizer flow number, spray cone angle, breakup length of liquid sheet, wavelength of undulations on liquid sheet, and spray droplet size. The characteristics of biofuel sheet breakup are deduced from the captured images of biofuel spray. The measurements of spray droplet size distribution are obtained using Spraytec. The experimentally measured characteristics of the biofuel sheet breakup are compared with the predictions obtained from the liquid film breakup model proposed by Senecal et al. (1999). The measurements of wavelength and breakup length of the biofuel sheet discharging from the simplex swirl atomizer agree well with the model predictions. The model-predicted droplet size for the biofuel spray is significantly higher than the experimentally measured Sauter mean diameter (SMD). The spray droplets formed from the liquid sheet breakup undergo secondary atomization until 35–45mm from the atomizer exit and thereafter the SMD increases downstream due to the combined effect of fuel evaporation and droplet coalescence. A good comparison is observed between the experimentally measured SMD of the biofuel spray and the predictions obtained using the empirical correlation reported in literature for sprays discharging from simplex swirl atomizers.

Spray of gelled propellants from an impinging-jet injector under different temperatures

This paper presents the results of an experimental study on the spray characteristics of gelled propellant from an impinging jet injector under different liquid temperatures. A high-speed camera was used to record detailed information about the liquid sheet breakup process and spray development. The rheological characteristics of the gel simulant under different temperatures were tested. It was found that the consistency coefficient decreases and the flow index increases as the liquid temperature increases. The flow characteristics and spray patterns for injectors with tapered orifices and straight orifices were tested, respectively. Because the injection of fluid through tapered orifices can decrease the viscosity of the fluid, the mass flow rate is increased and the liquid sheet behaves more unstably for injector with tapered orifices. The influence of liquid temperature on the mass flow rate for both injectors is minor. The spray photos showed that the liquid sheet is more unstable and easier to break up at higher temperature for both injectors. Generally, the liquid sheet breakup length decreases and the disturbance wavelength increases as the liquid temperature increases.

Spray Characteristics of Gelled Propellants in Novel Impinging Jet Injector

To improve the atomization quality of gelled propellants, a chamber similar to a Helmholtz resonator was installed in an impinging jet injector to introduce disturbances on the atomized fluid. The spray formation of gelled propellant from impinging jet injectors with a Helmholtz resonator-like chamber was examined experimentally. A high-speed camera was used to record the detailed information of the liquid sheet breakup process. Installing a resonator chamber in the impinging jet injector always tends to decrease the breakup length of the liquid sheet, but rarely does the installation influence the flow rate of the injector. The breakup length of liquid sheet is minimal when the diameter ratio of chamber to exit equals 4. To obtain a shorter breakup length, the ratio of chamber inlet diameter to outlet diameter should be close to the value of 1, but cannot equal 1 because the mass flow rate is decreased when this ratio equals 1. The effect of the ratio of length to diameter of the chamber is minor. Although the breakup length is minimal, when the ratio of chamber length to diameter is between the value of 1 and 1.5, the mass flow rate is also decreased.

PREDICTION OF SIZE AND VELOCITY DISTRIBUTIONS IN SPRAYS FORMED BY THE BREAKUP OF PLANAR LIQUID SHEETS USING MAXIMUM ENTROPY FORMALISM

A predictive model for size and velocity distributions of droplets in a liquid spray from the disintegration of a planar sheet has been proposed, based on the maximum entropy formulation (MEF) principle. The conservation laws of mass, momentum, and energy over the breakup region serve as the constraint conditions in the MEF model. The liquid sheet breakup length, evaluated from the nonlinear stability analysis of planar liquid sheet, is used to evaluate the momentum and energy exchange terms in the conservation equations. The mass mean diameter is calculated from the breakup of cylindrical ligaments using the deformed interface profile at the time of breakup. The simulated results of the droplet size distribution are compared with the results published in the literature and reasonable agreement is observed at different conditions. The investigation has brought out the effects of gas-to-liquid velocity ratio, gas-to-liquid density ratio, and Weber number on the droplet size and velocity distributions in the liquid spray.

Liquid film disintegration regimes and proposed correlations

The process of liquid sheet disintegration and break-up into a spray is studied making use of a flat liquid film surrounded by two air streams. The work considers a 2-D liquid film with an aspect ratio of 114 and a liquid velocity between 0.7 and 6.4 m/s (543⩽ Re L⩽4963) and an air velocity up to 39 m/s ( Re G ⩽17 647 ), and allows to study the basic phenomena typical of airblast atomisation. The results include the quantification of instability amplitudes, break-up lengths and frequencies for the above-mentioned range of liquid (water) and air flow velocities. Three different experimental techniques are used: back light and laser light sheet illumination, to measure the instability amplitudes, which leads to the liquid film disintegration and the spray formation; strobe light illumination, for the quantification of either break-up lengths and frequencies, and; a laser attenuation technique for frequency measurements and comparison with the visualisation technique. The results quantify the range of application of the different techniques, and include an analysis of the liquid disintegration process as function of the liquid velocity when exposed to different air flow velocities, along with the quantification of break-up lengths, disintegration frequencies and spray angles, and show that the disintegration of the liquid sheet is associated with a periodic process, which is mainly dependent on the absolute air velocity and the air–liquid momentum ratio. Correlations are proposed for liquid sheet break-up length and frequency based on the air-to-liquid momentum ratio.

00/02447 Hydrogen production from methane through catalytic partial oxidation reactions

The use of metal nanoparticles as fuel additives have gained interest due to its positive influence on liquid fuels’ combustion and emission performance. Nanoparticles dispersion affects the hydrodynamic and thermo-physical properties of the liquid fuel, and in turn, its atomization, mixing and evaporation characteristics. This work investigates the influence of nanoparticles dispersion on the spray performance of alternative gas-to-liquid (GTL) jet fuel under atmospheric ambient conditions. The spray characteristics of GTL fuel with dispersed alumina nanoparticles are compared with those of the pure GTL fuel. The spray characteristics at the macroscopic and microscopic levels are measured using the optical diagnostic techniques of shadowgraph and phase Doppler anemometry, respectively. The nanoparticles dispersed in liquid fuel tend to slightly alter the transient nature of the spray formation, enhance the liquid sheet instability and reduce the liquid sheet breakup length when compared to those of the pure GTL fuel. Furthermore, the mean droplet sizes of GTL fuel dispersed with nanoparticles are smaller than those of the pure GTL fuel.