Prompt Atomization Mechanism of the Tangentially Injected Prefilming (TIP) LDI Injector

Lean direct injection (LDI) combustion is one of the promising low pollution combustion technologies. One challenge of implementing LDI combustion is to achieve quick fuel-atomizing and mixing with air. In this paper, the spray characteristics and the prompt atomization process of the tangentially injected prefilming (TIP) LDI injector are investigated by experiments; the energy transmission model suitable for the prompt atomization process and the semi-empirical estimation model of SMD for the conical liquid film are derived. All experiments were carried out under 20°C and atmospheric pressure by using kerosene as the fuel. Firstly, effects of We and ALR on the spray distribution and SMD were studied by Mie scattering and Malvern spraytec laser diffraction system respectively, which were carried out at the operating conditions of We varying from 664 to 2656 and ALR varying from 16.3 to 24.5. Results show that large We is beneficial to disperse the spray in primary zone downstream the swirler. Then, breakup regimes of liquid film and droplets evolution were characterized by a high-speed camera with a long-distance microscope (LDM). Breakup regimes show that the film is torn up by the fierce outer airstream immediately. The primary breakup process does not rely on the surface waves anymore, which conforms to the prompt atomization mechanism. Finally, the energy transmission of the conical liquid film during the whole atomization process was analyzed, from which the semi-empirical estimation model of SMD was derived. The calculated and the measured SMD have good consistency, which demonstrates the applicability of the prompt atomization energy transmission model on a conical liquid film.

Study on the formation and separation process of droplets in the medical piezoelectric atomization device induced by intra-hole fluctuation

Oral inhalation of aerosolized drugs can be directly performed on the affected body organs including lesions of the throat, trachea as well as lungs. As compared to the other conventional therapies such as intravenous drip, intramuscular injection and external topical administration, this novel technique can greatly reduce the dosage and side effects of drugs. However, the traditional atomization devices always exhibit many drawbacks, such as wide spreading distribution of atomization particle size, the instability of transient atomization quantity and difficulties in precise energy control, which seriously restrict more extensive application of atomization inhalation therapy. The formation and separation process of droplets is a microphenomenon of atomization. Research on the droplet formation and separation process will help us to better understand the atomization mechanism. In present work, the Conservative Level Set Method (CLSM) is the first time to be applied on the simulation of the formation and separation of droplets in a medical piezoelectric atomization device induced by intra-hole fluctuation. The intra-hole fluctuation mechanism is analyzed in details, and also the expression of the volume change of the micro cone hole is evaluated. The control equation and simulation model of droplet formation and separation process has been well established by meshing the simulation model, and thereby the process of droplet formation and separation is simulated. The corresponding results demonstrate that the breaking time of droplets decreases with the increase of inlet velocity and liquid temperature, and increases with the increase of liquid concentration. Meanwhile, the volume of droplet decreases with the increase of inlet velocity and liquid concentration, but increases with the increase of liquid temperature. The velocity of droplet is enhanced with the inlet velocity and liquid temperature rising, and reduced with the increase of liquid concentration. When the large side diameter of micro-cone hole is set as 79 μm, the breaking time of the droplet reaches a minimum value of 38.7 μs, whereas the volume and the velocity of droplet reaches a maximum value of 79.8 pL and 4.46m/s, respectively. This study reveals the atomization mechanism of the medical piezoelectric atomization device induced by intra-hole fluctuation from a micro perspective . It provides theoretical guidance for the design of medical piezoelectric atomization devices and contributes to the promotion of inhalation therapy in practical use.

Effects of Water Supply Using Ultrasonic Atomization on the Working Life of MCF Slurry in MCF Polishing

The magnetic compound fluid (MCF) polishing process is a precision finishing method that has been applied to a large variety of materials, from soft optical polymers to hard ceramics. The purpose of this study is to extend the working life of MCF slurry. In this paper, we focus on the drying phenomenon of MCF slurry during polishing, and we develop a new water supply system that uses an ultrasonic atomization mechanism. This system can moisturize the MCF polishing area locally. Polishing experiments involving supplying water to MCF slurry are carried out, and extending the working life of MCF slurry is discussed.

Experimental Studies on the Spraying Pattern of a Swirl Nozzle for Coal Dust Control

The experimental and numerical studies were performed to understand the atomization mechanism of pressure spray of a swirl nozzle. The design and performance parameters such as spray cone angle, velocity of particles, spray pressure, and Sauter Mean Diameter (SMD) of the droplets were studied using a laser particle size analyzer and high-speed camera. The results show that the SMD increases at first, then decreases as the spray distance increases, and finally tends to be stable after 1 m. The SMD is largest in the center of the spray field and decreases gradually along the radial direction. The SMD distribution is more concentrated near the nozzle. Increasing spray pressure and deceasing nozzle diameter both can make the SMD distribution more concentrated and uniform. The swirl nozzle has been used in a coal mine and was shown to be very effective in suppressing coal dust compared to other traditional nozzles.