Papers by Keyword: Droplet Size

Abstract: Investigations of the influence of the parameters of mechanical effects on the temperature and mass of electrode metal droplets during electric arc surfacing with electrode materials of various chemical composition and type have been carried out. The main regularities of the process of droplet transfer during melting of a strip electrode with the introduction of control mechanical impacts have been established. The optimal range of the oscillation frequency of the strip electrode end is 40 ÷ 80 Hz, in which the average droplet diameter decreases to 1.3 ÷ 1.5 mm, and the mass to 0.08 ÷ 0.1 g. As a result of the research, it was found that, during electric arc surfacing with a strip electrode, changing the parameters of mechanical control impacts on the strip end allows not only to control the drop transfer frequency, but also to reduce the size and temperature of the electrode metal droplets, ensuring a decrease in heat input into the base metal and the formation of a favorable structure of the deposited weld metal.

Abstract: In microlubrication, effective spray cooling is generally dependent on the atomization process. Air assisted atomizer is commonly used in many industrial applications because even at low-pressure fuel or coolant supply, it can create a fine spray formation. Viscosity force resists the deformation of liquid ligaments into a droplet. This increase in viscosity creates a bigger droplet size. If the density of the coolant is more, it will resist the acceleration and results in a bigger droplet. Properties of coolant such as viscosity, density, and surface tension are important and will affect the droplet size. Hence, for effective microlubrication, the performance study of atomization is important. In this paper, computational fluid dynamics (CFD) is used to study atomization characteristics of biodegradable coolant castor oil and AccuLube-2000 at flow rate 150 ml/hr to 60 ml/hr. This paper focuses on the effect of coolant properties like viscosity and density on the droplet size and discrete phase model concentration. In this work, the CFD atomization is studied using a discrete phase model and a Realizable k-ϵ turbulent flow model. Numerical simulation shows that the droplet size of the castor oil is more than AccuLube-2000. Also, for a higher flow rate, the area near the nozzle had a very uneven concentration of sprayed particles. However, the concentration was more even as the spray went farther away from the nozzle.

Abstract: An experimental investigation has been carried out to study the effect of surfactant dosage on micro explosion phenomenon. Three water in diesel emulsion with 20% water by volume was prepared using mechanical stirring at 17000rpm for 100s.The emulsions were stabilised by a were stabilized by a single surfactant with three different doses. Water in diesel emulsion droplet was suspended on a thermocouple and the evolution of micro explosion was recorded with a high speed camera synchronized with temperature data logger. Secondary atomization of emulsion droplet was observed under Leiden frost regime using a hot plate as the heat source. The results show that the occurrences of micro explosion are affected by the volume of added surfactant by influencing the exploding temperature and waiting time. Physical properties like density, viscosity and surface tension were also found to be influenced by the amount of surfactant used.

Abstract: Sufficient air insert by reduced liquid in flashing propellants are required to produce fine droplet size with symmetrical spray in an aerosol atomiser without swirling design. It is called novel matched valve-actuator with two-fluid fine nozzle. Two-fluid fine nozzle design is an arrangement between air-assist atomiser insert, air blast and effervescent atomiser insert. However, 50% fill ratio and 9bar on pressure can with a currently acceptable become “Benchmark Objective” in this research. The results shows a few measurement with the same volume flow rate and variable flow rate of two fluids atomiser which have been taken in the experimental. 50 ml/min for liquid flow rate and 150ml/min flow rate of insert gas could reduce droplet size less than 70μm SMD by modifying the insert to promote greater cone angle and droplet size distribution with differences on quantity of air, liquid supply and the atomising velocity. Validation of two-fluid fine nozzle results is also recommended to be carried out and compared with the experiment results which related to turbulence kinetic energy with the atomiser insert and droplet size. Further researches are concentrating on modelling droplet breakup downstream of the atomiser insert.Keywordaerosol atomiser, two-fluid fine nozzle, fill ratio, droplet size.

Abstract: The internal-mixing twin-fluid atomizer has found wide application in aerospace, industrial gas turbine, oil-fired boiler, energy field and so on. The atomization characteristics of internal mixing nozzle under different operating conditions are studied by utilizing the Malvern laser particle size analyzer. According to the experiment results, the influence of air pressure, hydraulic pressure and air-liquid ratio to droplet size and uniformity are analyzed. The three-dimensional flow field model of internal mixing nozzle is built to simulate the droplet size of mixing room and outlet by Fluent. The simulation results show that the droplet size decreases along with the increase of the air pressure and the air-liquid ratio, moreover, the air pressure plays a main actor. The droplet size increases in the mixing room, and then decrease sharply at the domain of the outlet. The droplet size of the nozzle’s outlet obtained in simulation matches the experimental result.

Abstract: In order to find out the factors influencing self-suction spraying with pressure gas and water performance, the working principle of the spray was analyzed, orthogonal experiments were conducted, in which influenced of different air flow, bronchia-nozzle distance, nozzle diameter as well as the diffusion angle on the effective rang and spray particle size were tested, the optimal matching of parameters was obtained. The results showed that, the optimal configuration parameters could be obtained by orthogonal test of self-suction spraying with pressure gas and water, to provide data support for the design of efficient spraying device.

Abstract: Gas turbine cycles with after fogging where water is injected after compressor could offer enhanced efficiency compared to inlet fogging system due to higher water injection ratio. In this work the after fogging process is modeled based on the evaporation of droplets. Transient behaviors of the process are investigated with analytic expressions obtained by considering heat and mass transfer and thermodynamic relations. Effects of droplet size on the transient behaviors of important system variables are thoroughly investigated including diameter and mass of droplets, temperature and density of air, and mass flux and heat transfer from the droplets.

Abstract: Aiming at the welding arc can act with the magnetic field, has electrical quasi-neutral and electrical conductivity. This paper introduced an adscititious longitudinal magnetic field to control the CO2 welding process and used the Hanover Welding Quality Analyzer to acquire the real-time welding signal. Meanwhile, the short circuit behavior of CO2 welding under the adscititious longitudinal magnetic field, was monitored with the High-speed Photography System. The results show that when the excitation current in an optimal range, the welding current decay and the frequency of short circuit transition is uniform and faster, smaller droplet size and the welding process is more stability than welding without adscititious magnetic field.

Abstract: Ultrasound was adopted to prepare emulsion fuels between bio-oil and 0# diesel. The effects of ultrasound power and treating time on the stability of emulsion fuels were investigated. Excellent stability with stable time as long as 35 hours was obtained under an ultrasound power of 80W and a treating time of 3 minutes. Malvern nanometer particle size analyzer (Zetasizer Nano S90) was used to study the droplet size of emulsion fuels. The emulsion fuels with smaller droplet size had longer stable time. And the droplet size of the optimal emulsion fuel was around 0.4 um.

Abstract: The Venturi scrubber, equipment frequently used in the removal of particles from gases, is constituted basically by a duct with a convergent section followed by a constriction, or throat, and a divergent section. A liquid, usually injected in the throat, is atomized by the flowing air at high speed. The formed droplets act as collectors of particles from the gas. The process of droplet formation from an injected liquid can be described as follows: the liquid enters the gas stream in the form of a jet, perpendicular to the gas flow. As the jet penetrates the gas stream, it is bent by the gas drag. After a given penetration distance, a burst occurs, and the remaining jet is disintegrated as a droplet cloud. Depending on the liquid and gas flow rates, the penetration on the jet into the gas stream may reach the walls of the equipment, and a fraction of liquid deposits in the form of a film. This film contributes little for the removal of particles from the dust laden gas. Few studies have analyzed the formation of film at the scrubber walls and its influence in the droplet size inside the Venturi scrubber. For this reason, the present study is focused on the experimental measurement of the deposition of the liquid film on the walls of a rectangular Venturi scrubber and, simultaneously, the estimation of the droplet size measured in the Venturi throat. The experiments were carried out varying the liquid flow rate, the gas velocity and the number of orifices of liquid injection. A correlation, using a dimensionless number, was proposed to quantify the influence of each experimental condition. The results indicate that film fraction has a significant influence in the droplet size measured inside of Venturi scrubber.