Sharif Digital Repository

In this work, the cone-jet mode of electrospray is simulated by a two phase solver in OpenFoam software. For this aim firstly, breakup of a liquid jet is examined without applying any electric potential to the injecting capillary and results are compared with other works to evaluate the two phase solver. Next with applying electric potential, the whole evolution of cone-jet in time is simulated. One of the most important issues in this mode is the minimum potential that needs to form a stable cone-jet in different flow rates. These minimum voltages are obtained in various flow rates and compared with other experimental and computational works. Result shows that with increasing flow rate the... 

In the present study liquid thermophysical properties in electrospray has been studied. Other parameters such as electrical configuration do not change during this study. For this purpose Alcoholic fuels have been chosen because of their high energy density and their polarity that make them suitable for electrospraying. Electrical conductivity, surface tension, viscosity, density and permittivity are the most effective liquid properties in the electrospraying. The visualization method used for this study is shadowgraphy and light scattering method. In this study the range of flow rate and voltage is acquired for each operational mode and Q-V diagram has been obtained for all liquids... 

The purpose of this project is investigating the effect of cross flow and electric field on a liquid simple-jet experimentally. In this research the effect of parameters such as liquid to air momentum ratio, electric field on jet trajectory, penetration and the lenght of breakup point with respect to the jet outlet were studied. The air was produced by a blower in a duct with square test section of 8 cm sides. The air velocity varied from 1 m/s to 11 m/s. Liquid ethanol was injected into the duct with a needle with outer diameter of 0/62 mm and inner diameter of 0.4 mm and 28 mm length. The velocity of jet was 0/62 m/s while the change of liquid to air momentum ratio was from 3 to 260 The... 

With increasing demand for more efficient combustion processes, alternative processes like application of magnetic and electric fields for modification of combustion have offered possible solutions. In the recent years, liquid electro-spraying has been a hot topic with growing interest due to its wide applications in such area as fuel atomization in combustion systems, which has been investigated in this project. Notice that in this method the liquid fuel in the high voltage electric field between electrodes will be broken into small droplets. In this thesis diffusion combustion of two alcoholic liquid fuels of ethanol and butanol at the exit of a small-scale combustor of vertical Pyrex... 

Electrospray is an interesting method to produce spray. This study has an insight on electrospraying phenomenon and its effective parameters. All modes, the forces and the situation to establish has been investigated for ethanol. Suitable configuration is introduced and for different flow rates and voltages the phenomenon is studied. Images are captured by two camera (high speed camera and high resolution camera) by using two method (shadowgraphy and light scattering). In the respect of producing fine and monodisperse droplets in cone-jet mode the stability of this mode is imported to enlarge. The special nozzle is design to increase stability of cone-jet mode even 70 times of using... 

Due to Reduction of fossil fuels resources and the pollution caused by using them, it seems inevitable to shift to using reproducible energies. Among different resource of reproducible energy, fuel cell is one of suitable technologies for investigation and development. Fuel cell is an electrochemical system to convert chemical energy of fuel directly to electrical energy. Each fuel cell has seven part (two Bipolar Plate, two electrode, two catalyst layer and polymeric Membrane). Oxidation occur in anode of fuel cell and created electron enters external circuit and then riches the cathode. The positive ion created in the anode reaches the cathode through the membrane (electrolyte) and... 

Due to the large application of electro-sprays in various industries, the study of the stability of electro-hydrodynamic flows is important. This thesis examines the stability of cylindrical liquid jets in the presence of an axial electric field. The definition of this jet is a simplified model of electrospray, electrospinning. In this model, the stability of a free incompressible cylindrical flow with surface tensile strength, conductivity, polarization, viscosity, and dielectric constant is determined, irrespective of the solubility of the jet and the surrounding fluid (air), in the presence of uniform axial electric field has taken. This will be done by adding the forces generated by the... 

With the progression of technology demands for novel method of heat cooling is increased so the old method of cooling such as heat removal by air stream with force convection and even single phase method was not sufficient for today’s industry need. Nowaday, spray cooling method which belongs to two phase cooling method is one of the most popular method. In this study two method of spray cooling: spray cooling with flow blurring nozzle and electrospray cooling were investigated. For both method, at first the physics of phenomena and morphology of spray is studied experimentally then the efficiency of heat removal in each method is evaluated by the assessment of variation of temperature and... 

Electrospray is one of the liquid spraying methods. This study has an insight on Electrospray phenomenon and its effective parameters. First, there is a short introduction of phenomenon, then, how it works and effective factors related to the procedure are described. All modes, the forces and the situation to establish has been investigated for ethanol sprayed from hemispherical nozzle. Suitable configuration is introduced and for different flow rates and voltages the phenomenon is studied. One of the innovations of this study is the imaging technique used to captured high-quality images. In fact, captured images by means of high-power light-emitting diode (LED) synchronized with digital... 

Liquid jet behavior in an intense electric field is studied experimentally and numerically.Imaging is used in experiments to charactrize jet behavior. Electrospray of ethanol using a simple needle in a wide range of operating conditions is investigated. Liquid meniscus is captured using a high-speed camera and different electrospray modes are described based on involved forces. A new nozzle is invented that broadens the stability margins of the useful cone-jet mode. The physical mechanisms of the new cone-jet is discussed and it is characterized using appropriate dimensionless parameters. A simple jet in presence of a gaseous crossflow and a normal electric field is also studied. The liquid... 

In the present work we first introduced ILIDS and review the theory of interferometry and light scattering from droplets. Bases on ILIDS method, droplets are irradiated by monochrome sheet laser, where the superposition of reflected and first-order refracted beams form a parallel fringe pattern at out of focus plane on the imaging sensor in the forward-scatter region. This pattern can be related to the droplet size by using simple geometrical optics. For the present work, an image processing algorithm is utilized to capture weak and noisy images of droplets to reduce the lost data in the sizing procedure. Since ILIDS method is applied for small and dilute spray, it is suitable for... 

Electrospray is a process in which the charged liquid is subjected to the effect of an electric field and after passing through an emitter, it will propagate in the form of jets or small droplets. This process is used in applications such as electric thrusters, cooling or mass spectrometry. In the electronics industry, cooling high-temperature microprocessors is a challenge. In this regard, air-based cooling systems are not well able to discharge heat from electrical and electronic components. Electrospray cooling technology is one of the new and promising methods. In this research, the two-dimensional simulation of electrospray cooling is performed by using COMSOL commercial software as a... 

The electrospray technique involves the production of small charged droplets through the application of electrohydrodynamic forces. Under well-defined operating conditions, multiple flow modes can be observed, among which the stable jet-cone mode has received significant attention from the research community. This mode is desirable due to its uniform droplet diameter, reduction in droplet rebound when impacting hot surfaces, and potential for utilizing two-phase heat transfer for cooling purposes. In this study, a comprehensive experimental investigation was conducted to evaluate the cooling of hot surfaces through the use of electrospray in the steady cone-jet mode. The fundamental... 

To develop a novel cell culture method for enhancement of bone marrow stromal cell growth and infiltration into the 3d electrospun PCL-based scaffold, we utilized the RPM system to simulate microgravity. In current study, six different scaffolds are produced using the electrospinningelectrospraying technique. These scaffolds are compared based on their structural (average diameter and SEM micrographs), mechanical (Tensile strength, elongation and wettability) and biological (Biodegradability, bioactivity, biocompatibility, cell adhesion, cell infiltration and antibacterial quality) characteristics. It is noted that the porous nano-hydroxyapatite/titanium hydroxide/polycaprolactone...