Plume Angle Research Articles

A computational approach to predict external spray characteristics for flashing and cavitating nozzles

A computational approach to predict external spray characteristics for flashing and cavitating nozzles was presented and validated. It is developed as a fully Eulerian and compressible two-phase flow solver that simulates vaporization and condensation of the fuel using a Homogeneous Relaxation Model (HRM). The flow solver together with the interface area density model was applied to predict spray spreading angle. A method to identify spray plume boundary from the predicted flow field that offers a meaningful comparison to experimental definition was discussed in detail. Using the experimental data available in literature, a comparison between axi-symmetric and asymmetric nozzles was made to assess the nature of the influence of the nozzle geometry and the operating conditions on the ensuing spray. On the basis of this comparison, it was inferred that the spray plume angle of asymmetric nozzles is largely geometry dependent for a wide range of pressure ratios.

A Review: Non-Evaporating Spray Characteristics of Biodiesel Jatropha and Palm Oil and Its Blends

The study on the Non-evaporating spray characteristics in biodiesel is imperative to comprehend the conduct of the spray in different biodiesel. Non evaporating spray characteristics give some parameters, such as spray cone (plume) angle, spray (tip) penetration and droplet size. This paper reviews that methyl ester or biodiesel fuel from Jatropha (BDFJ) and biodiesel fuel from palm oil (BDFP) have similar characteristics of Diesel Fuel (DF). Biodiesel derived from palm oil and Jatropha oil have longer cone angle and spray (tip) penetration than DF. In biodiesel, high surface tension and viscosity, caused by the slower separation, can lead to shorter cone angle and higher penetration. Spray tip penetration will increment with the increasing of mixing proportion in biodiesel blends. In the cone angle, palm methyl ester gives a smaller angle than DF. The characteristic of cone angle is decreased when the percentage of the proportion of biodiesel is expanded. In Sauter Mean Diameter (SMD), diesel fuel sprays are smaller than the biodiesel spray. The SMD diminishes when the injection pressure is expanded. It happens because of the biodiesel has high viscosity that can expand the friction among the fuels to the surface of the nozzle. Hence, a study of biodiesel is needed before conducting the experiment of non-evaporating spray. Mainly, the fuel properties such as surface tension, viscosity and density play critical parts in the conduction of non-evaporating spray characteristics of biodiesel and its blends.

Particle Simulations of the Effects of Atomic Oxygen on Ion Thruster Plumes

Ion thruster plumes interacting with ambient atomic oxygen are simulated using direct simulation Monte Carlo/particle-in-cell code with automatic mesh refinement/octree grids. Because of the disparity among the species concentrations and velocities, particle weighting factors with multiple species weighting time steps have been used. To calculate the elastic cross section for collisions, the variable hard sphere collision cross section was compared with the higher-fidelity Lennard–Jones model and found to agree well at the relevant collision energies. Because momentum and charge exchange cross sections for and O are not available in the literature, analytic approaches were used to infer these values. The simulations provide a number of interesting results about the role of and collisions. The effect of incoming freestream atomic oxygen direction on the ion thruster plume at 185 and 300 km altitudes was studied by changing the plume angle with respect to the freestream atomic oxygen, corresponding to satellite orientation change in orbit. It was observed that the freestream atomic oxygen affects the backflux of Xe at the lower altitude. This effect lessens as the altitude increases and is not observable at 300 km, and it was observed that Xe fluxes scale in a linear fashion with the density of O. The spatial distribution of the xenon ion fluxes was not influenced by collisions with freestream atomic oxygen.

Mass Median Plume Angle: A novel approach to characterize plume geometry in solution based pMDIs

High-speed laser imaging (HSLI) is the preferred technique to characterize the geometry of the plume in pressurized metered dose inhalers (pMDIs). However, current methods do not allow for simulation of inhalation airflow and do not use drug mass quantification to determine plume angles. To address these limitations, a Plume Induction Port Evaluator (PIPE) was designed to characterize the plume geometry based on mass deposition patterns. The method is easily adaptable to current pMDI characterization methodologies, uses similar calculations methods, and can be used under airflow. The effect of airflow and formulation on the plume geometry were evaluated using PIPE and HSLI. Deposition patterns in PIPE were highly reproducible and log-normal distributed. Mass Median Plume Angle (MMPA) was a new characterization parameter to describe the effective angle of the droplets deposited in the induction port. Plume angles determined by mass showed a significant decrease in size as ethanol increases which correlates to the decrease on vapor pressure in the formulation. Additionally, airflow significantly decreased the angle of the plumes when cascade impactor was operated under flow. PIPE is an alternative to laser-based characterization methods to evaluate the plume angle of pMDIs based on reliable drug quantification while simulating patient inhalation.

Investigation of injector coking effects on spray characteristic and engine performance in gasoline direct injection engines

Spray and droplet characteristics of a coked injector were compared to those of a clean injector at the atmospheric conditions and investigated using high-speed imaging and a Phase Doppler Particle Analyzer (PDPA). Scanning Electron Microscope (SEM) and X-ray 3D microtomography images were analysed to understand the physical characteristics of injector nozzle deposits. Furthermore, Energy Dispersive X-Ray Spectroscopy (EDS) was utilized to obtain the elemental composition of the deposit. A single cylinder optical gasoline direct injection (GDI) engine was used to compare diffusion flames for each injector. In this study, the location and topography of the deposits demonstrated that they extensively formed in the external holes of the injector, and reduced in size and quantity through the internal holes. Elemental analysis of the deposits exhibited that carbon (C) and oxygen (O) were the predominant elemental components through both the internal and external holes of the injector. The coked injector exhibited higher penetration lengths, smaller plume angles, larger spray cone angles, higher mean droplet velocity and larger droplet size as compared to the clean injector. Images of the optical engine indicated strong diffusion flames around the coked injector tip. In-cylinder pressure measurements indicated that the coked injector produced lower in-cylinder pressures, implying lower combustion stability compared with the clean injector. This work was carried out to obtain a comprehensive study of injector coking effects on spray behaviour and engine performance.

Personalized Medicine in Nasal Delivery: The Use of Patient-Specific Administration Parameters To Improve Nasal Drug Targeting Using 3D-Printed Nasal Replica Casts.

Effective targeting of nasal spray deposition could improve local, systemic, and CNS drug delivery; however, this has proven to be difficult due to the anatomical features of the nasal cavity, including the nasal valve and turbinate structures. Furthermore, nasal cavity geometries and dimensions vary between individuals based on differences in their age, gender, and ethnicity. The effect of patient-specific administration parameters was evaluated for their ability to overcome the barriers of targeted nasal drug delivery. The nasal spray deposition was evaluated in 10 3D-printed nasal cavity replicas developed based on the CT-scans of five pediatric and five adult subjects. Cromolyn sodium nasal solution, USP, modified with varying concentrations of hypromellose was utilized as a model nasal spray to evaluate the deposition pattern from formulations producing a variety of plume angles. A central composite design of experiments was implemented using the formulation with the narrowest plume angle to determine the patient-specific angle for targeting the turbinate region in each individual. The use of the patient-specific angle with this formulation significantly increased the turbinate deposition efficiency compared to that found for all subjects using an administration angle of 30°, around 90% compared to about 73%. Generally, we found turbinate deposition increased with decreases in the administration angle. Deposition to the upper regions of the replica was poor with any formulation or administration angle tested. Effective turbinate targeting of nasal sprays can be accomplished with the use of patient-specific administration parameters in individuals. Further research is required to see if these parameters can be device-controlled for patients and if other regions can be effectively targeted with other nasal devices.

Magnetic field configurations on thruster performance in accordance with ion beam characteristics in cylindrical Hall thruster plasmas

Magnetic field configuration is critical in Hall thrusters for achieving high performance, particularly in thrust, specific impulse, efficiency, etc. Ion beam features are also significantly influenced by magnetic field configurations. In two typical magnetic field configurations (i.e., co-current and counter-current configurations) of a cylindrical Hall thruster, ion beam characteristics are compared in relation to multiply charged ions. Our study shows that the co-current configuration brings about high ion current (or low electron current), high ionization rate, and small plume angle that lead to high thruster performance.

Time-dependent line-of-sight extinction tomography for multi-hole GDI injectors

Finely atomized sprays from multi-hole gasoline direct injection (GDI) fuel injectors make them an ideal choice for automobile applications. A knowledge of the factors affecting the performance of these injectors is hence important. In the study presented here, we employ statistical extinction tomography to examine the transient characteristics of two GDI fuel injectors with five and six holes. Two axial locations, 25 mm and 35 mm from the injector exit, are chosen for experimental measurements, and the dependence of injection pressure and ambient temperature on plume locations and angles is examined from these measurements. A pressure chamber with opposing windows is used which permits the nozzle to be rotated 12 times (30° each rotation) to obtain information on the complete spray structure. Additionally, the plume centroid locations are measured and compared with those obtained with a mechanical patternator. The centroid locations from the two instruments compare favorably.

High-Speed Laser Image Analysis of Plume Angles for Pressurised Metered Dose Inhalers: The Effect of Nozzle Geometry.

The aim of this study is to investigate aerosol plume geometries of pressurised metered dose inhalers (pMDIs) using a high-speed laser image system with different actuator nozzle materials and designs. Actuators made from aluminium, PET and PTFE were manufactured with four different nozzle designs: cone, flat, curved cone and curved flat. Plume angles and spans generated using the designed actuator nozzles with four solution-based pMDI formulations were imaged using Oxford Lasers EnVision system and analysed using EnVision Patternate software. Reduced plume angles for all actuator materials and nozzle designs were observed with pMDI formulations containing drug with high co-solvent concentration (ethanol) due to the reduced vapour pressure. Significantly higher plume angles were observed with the PTFE flat nozzle across all formulations, which could be a result of the nozzle geometry and material's hydrophobicity. The plume geometry of pMDI aerosols can be influenced by the vapour pressure of the formulation, nozzle geometries and actuator material physiochemical properties.

Fluid Motions Associated with Engineered Area Bubble Plumes

AbstractCurrent bubble oil booms (BOBs) create bubble curtains to protect fixed installations in calm waters such as harbors, but fail in more energetic environments. Field and lab studies reveal that area bubble plumes enable BOB applications in such environments. Area bubble plumes exhibit dynamics distinct from point- or line-source plumes, including thicker and more robust outwelling flows and relatively smaller turbulence scales. Area bubble plume studies broaden our understanding of natural systems, where currents and waves are ubiquitous, leading to a variety of marine applications. Laboratory studies in a large flume have investigated the fluid dynamics of shallow line and area bubble plumes. These studies focused on area-plume application to oil spill response, which, based on preliminary tests, featured improved outflows with a downstream barrier. A range of ambient currents, current–plume angles, and airflows were tested. Key to understanding current–plume interactions was the upstream rotor or...

Temporal investigations of transient fuel spray characteristics from a multi-hole injector using dimensionless analysis

The breakup of high speed liquid jets and the spray formation from a multi-hole direct-injection injector were investigated by analyzing the temporal development of spray penetration and cone angle. Planar Mie scattering was applied to generate spray images under a wide range of operating conditions with ethanol, methanol and gasoline as test fuels. Dimensionless parameters such as Reynolds number (Re), Weber number (We), and gas-to-liquid density ratio (ρa/ρl) were used to enumerate the competition and balance of forces that dominated the spray formation, including the inertia force, viscous force, surface tension force and aerodynamic force. The results show that two temporally sequential stages exist during the spray formation, namely the initial stage and developed stage. During the initial stage, the spray penetration increases linearly with time after the start of injection (ASOI). The penetrating speed during the initial stage is primarily controlled by the competition between the inertia and surface tension while the aerodynamic force shows only minor influence. The duration of the initial stage of penetration is dependent on the competing process between inertia and viscous force as well as that between inertia and aerodynamic force. During the developed stage, the effect of aerodynamic forces becomes more influential on the spray penetration. The viscous force shows weak impact on developed stage penetration under low Reynolds number (Re<12,500) conditions. In contrast with the strongly time-dependent penetration, the plume angle of the emerging jets stays relatively constant during the entire injection duration. Based on the above analysis, new dimensionless correlations have been established to quantitatively characterize the effects of competing forces on spray penetration and cone angle. Compared to the classical correlations, these new correlations explicitly express the relative importance of each force during different temporal stages of spray formation. Therefore, they provide more insight into the physical mechanism of high pressure spray formation process.

Plume Control of a Cusped Field Thruster

The cusped field thruster uses several permanent ring magnets of alternating polarity to create a multistage cusp magnetic topology. It has demonstrated a long lifetime because of reduced plasma losses to the discharge channel surface. However, the high beam divergence problem has not been solved in this type of thruster. The purpose of this technical note is to describe a plume control method to reduce its plume angle. The results show that the magnetic field intensity in the plume region and the shape of the last separatrix have great influence on plume divergence.

A Comparison of the Deposition Patterns of Different Nasal Spray Formulations Using a Nasal Cast

For nasally delivered medications, it is quite a challenge in the formulation development to characterize the deposition pattern in vivo. An in vitro nose model has been developed recently and adopted in our study to compare the deposition pattern of different nasal solution formulations. One low-viscosity nasal solution and five other solutions containing either Avicel or hydroxypropyl methylcellulose (HPMC) as the viscosity enhancers were examined in this study. The viscosity, spray pattern, plume geometry, and droplet size were characterized. The in vitro deposition patterns were assessed using an anatomically correct silicone nasal cast combined with a color-based image-analysis method. The correlations between the formulation variables, the spray characteristics, and the deposition pattern were investigated. The addition of each viscosity enhancer resulted in increasing viscosity, larger droplet size, narrower plume angle, and lesser anterior deposition. However, it appears that the changes in spray ...

Radial scale effect on the performance of low-power cylindrical Hall plasma thrusters

Investigation of the radial scale effect on low-power cylindrical Hall thrusters has been undertaken by comparing the thrusters with three different channel diameters of 28, 40, and 50 mm. The investigation found that both the anode efficiency and the thrust of the larger thruster are higher as the anode power is raised. On the other hand, higher current and propellant utilizations are achieved for the smaller thruster, which is due to higher neutral density and better electron confinement. The large plume angle of the small cylindrical Hall thruster causes thrust loss, resulting in the reduction of anode efficiency.

A Review on Atomization and Sprays of Biofuels for IC Engine Applications

Ever increasing energy requirements, environmental concerns and energy security needs are strongly influencing engine researchers to consider renewable biofuels as alternatives to fossil fuels. Spray process being important in IC engine combustion, existing literature on various biofuel sprays is reviewed and summarized. Both experimental and computational research findings are reviewed in a detailed manner for compression ignition (CI) engine sprays and briefly for spark ignition (SI) engine sprays. The physics of basic atomization process of sprays from various injectors is included to highlight the most recent research findings followed by discussion highlighting the effect of physico-chemical properties on spray atomization for both biofuels and fossil fuels. Biodiesel sprays are found to penetrate faster and have narrow spray plume angle and larger droplet sizes compared to diesel. Results of analytical and computational models are shown to be useful in shedding light on the actual process of atomization. However, further studies on understanding primary atomization and the effect of fuel properties on primary atomization are required. As far as secondary atomization is concerned, changes in regimes are observed to occur at higher air-jet velocities for biodiesel compared to those of diesel. Evaporating sprays revealed that the liquid length is longer for biodiesel. Pure plant oil sprays with potential use in CI engines may require alternative injector technology due to slower breakup as compared to diesel. Application of ethanol to gasoline engines may be feasible without any modifications to port fuel injection (PFI) engines. More studies are required on the application of alternative fuels to high pressure sprays used in Gasoline Direct Injection (GDI) engines.

Electrospray cone-jet breakup and droplet production for electrolyte solutions

The production of charge droplets via the electrospray of an electrolyte is experimentally and theoretically found to be a Coulombic fission phenomenon that occurs when induced space charge at the microjet interface reaches a critical density as the charge separation approaches the Bjerrum length. The field surrounding the cone is dominated by the Taylor harmonic, which is responsible for inducing space charge within an interfacial Debye layer, such that the jet breakup length and plume angle are strong functions of both the ionic strength and interfacial surface tension.

Computed intranasal spray penetration: comparisons before and after nasal surgery

Quantitative methods for comparing intranasal drug delivery efficiencies pre- and postoperatively have not been fully utilized. The objective of this study is to use computational fluid dynamics techniques to evaluate aqueous nasal spray penetration efficiencies before and after surgical correction of intranasal anatomic deformities. Ten three-dimensional models of the nasal cavities were created from pre- and postoperative computed tomography scans in 5 subjects. Spray simulations were conducted using a particle size distribution ranging from 10 μm to 110 μm, a spray speed of 3 m/second, plume angle of 68 degrees, and with steady state, resting inspiratory airflow present. Two different nozzle positions were compared. Statistical analysis was conducted using Student t test for matched pairs. On the obstructed side, posterior particle deposition after surgery increased by 118% and was statistically significant (p = 0.036), while anterior particle deposition decreased by 13% and was also statistically significant (p = 0.020). The fraction of particles that bypassed the airways either pre- or postoperatively was less than 5%. Posterior particle deposition differences between obstructed and contralateral sides of the airways were 113% and 30% for pre- and postsurgery, respectively. Results showed that nozzle positions can influence spray delivery. Simulations predicted that surgical correction of nasal anatomic deformities can improve spray penetration to areas where medications can have greater effect. Particle deposition patterns between both sides of the airways are more evenly distributed after surgery. These findings suggest that correcting anatomic deformities may improve intranasal medication delivery. For enhanced particle penetration, patients with nasal deformities may explore different nozzle positions.

Macroscopic characteristics for direct-injection multi-hole sprays using dimensionless analysis

The macroscopic spray characteristics were quantified using dimensionless analysis by examining the role of the dominating forces associated with liquid-jet breakup. The Weber number, Reynolds number, and air-to-liquid density ratio dimensionless numbers were used to capture the primary forces including the inertia, viscous, surface tension, and aerodynamic drag forces. Planar Mie-scattering technique was applied to generate spray images over a broad range of conditions found in today’s spark-ignition-direct-injection (SIDI) engines, providing a relatively large range of dimensionless numbers. The effect of fuel properties were examined using gasoline, methanol and ethanol fluids. Six regions described on a Weber number versus Reynolds number domain were selected to identify the relative importance of the inertia force, surface tension force, and viscous force on macroscopic spray structure. The effect of aerodynamic drag was individually determined by characterizing the spray over a range of ambient air-to-liquid density ratios. As a result, for the non-flash-boiling multi-hole sprays in this study, the Weber number and air-to-liquid density ratio have much more profound effect on the spray penetration and spray–plume angle compared to the Reynolds number contribution. The inertia force and air drag force are more important factors compared to the viscous force and surface tension force. This analysis yielded dimensionless correlations for spray penetration and spray–plume angle that provided important insight into the spray breakup and atomization processes.

Preliminary investigation tests of novel antifungal topical aerosol

Spray formulation can minimize pain and irritation experience during the application of conventional dosage forms. Econazole Nitrate is an active ingredient of the aerosol concentrate to be used for twice-daily application because of its long durability in the superficial layers of the fungal infected skin. The aim of this study is preliminary investigation of Econazole Nitrate spray by varying the concentrations of different constituents of the spray. The ratios of Propylene glycol (PG) and isopropyl myristate (IPM) were selected as independent variables in 22 full factorial designs, keeping the concentration of solvent, co-solvent and propellant LPG constant. Aerosol also contained Ethanol as solvent and Isopropyl alcohol as co-solvent. All ingredients of the aerosol were packaged in an aluminum container fitted with continuous-spray valves. Physical properties evaluated for the Econazole Nitrate spray included delivery rate, delivery amount, pressure, minimum fill, leakage, flammability, spray patterns, particle image and plume angle. Glass containers were used to study incompatibility between concentrate and propellant due to the ease of visible inspection. Isopropyl myristate at lower concentrate showed turbidity, while at high concentration it met the requirements for aerosol and produced Econazole Nitrate spray with expected characteristics.

Deviated nasal septum hinders intranasal sprays: a computer simulation study.

This study investigates how deviated nasal septum affects the quantity and distribution of spray particles, and examines the effects of inspiratory airflow and head position on particle transport. Deposition of spray particles was analysed using a three-dimensional computational fluid dynamics model created from a computed tomography scan of a human nose with leftward septal deviation and a right inferior turbinate hypertrophy. Five simulations were conducted using FluentTM software, with particle sizes ranging from 20-110 &#956;m, a spray speed of 3 m/s, plume angle of 68(deg), and with steady state inspiratory airflow either present (15.7 L/min) or absent at varying head positions. With inspiratory airflow present, posterior deposition on the obstructed side was approximately four times less than the contralateral side, regardless of head position, and was statistically significant. When airflow was absent, predicted deposition beyond the nasal valve on the left and right sides were between 16% and 69% lower and positively influenced by a dependent head position. Simulations predicted that septal deviation significantly diminished drug delivery on the obstructed side. Furthermore, increased particle penetration was associated with presence of nasal airflow. Head position is an important factor in particle deposition patterns when inspiratory airflow is absent.