Experimental Study Of High Pressure Micro-atomizing Nozzle On Spray Characteristics

Nozzle is a common device in various fields. It is widely used in household air humidification, manufacture, agriculture, the pharmaceutical industry and others where fine droplets are needed for atomization. Improved atomization increases economic benefit and is more environmentally-friendly. Therefore, studying the effect of nozzle atomization is practically significant.Based on combination of simulation and experiments, the dissertation is aimed at investigating spray characteristics of high pressure micro-atomizing nozzle.Simulation is adopted to study the physical quantities where experiments are impossible or very difficult to achieve. In the dissertation, simulation of nozzles come first. Three-dimensional models are built through Solid Works, then led into ANSYS for grid partitioning and boundary-layer setting. Then it is necessary to complete the initial setup and the iteration in Fluent. The final process is finished in CFD-Post. The simulation is mainly about the atomization with nozzles of 0.2 mm,0.4 mm, 0.6 mm and 0.8 mm of aperture size. The experiments are conducted at the same inlet pressure. Under the same pressure of inlet, the smaller the aperture is, the greater the maximum velocity of the droplets will be. Spray simulation for a nozzle of 0.8 mm at five different inlet pressure. The result shows that in the case of a certain size of aperture, the maximum velocity of the droplet increases with the increase of pressure. It also suggests that the aperture size and inlet pressure have little effect on temperature field.The dissertation also includes atomization experiments with nozzles of 0.2 mm,0.4 mm, 0.6 mm and 0.8 mm under the same pressure, during which high-speed camera is used for shooting and analyzing. It shows that the atomization cone angle becomes larger with the increase of the aperture. The spray nozzle with a diameter of 0.8 mm is experimented under 4 different inlet pressure, where a high-speed camera is also used for the same purpose. The result shows that when the aperture size is decided, the greater the inlet pressure is, the greater the atomization cone angle will be. At the same time, the temperature field is measured by the infrared thermal imaging system, and the change of the aperture size and inlet pressure has no effect on the temperature change of the spray droplets.Finally, by simulation and experiments, it is concluded that reducing the size of the aperture and increasing the inlet pressure will both improve the atomization effect. Although the latter works better because the decrease of the aperture size reduces the atomization cone angle though the maximum velocity of the droplet is increased.