Nozzle atomization technology covers almost all industr […]
Nozzle atomization technology covers almost all industrial fields, such as transportation, agricultural production, and people's daily life. In addition to the combustion of various fuels (gas, liquid and solid fuel), atomization technology in non-combustion industries such as catalytic production Granules, food processing, powder coating, and pesticide spraying are also widely used. The atomization nozzle technology of the nozzle for liquid fuel is briefly introduced.
The so-called atomization of liquid refers to the physical process of liquid becoming a liquid mist or other small droplets in a gaseous environment under the action of external energy. For its atomization mechanism, there have been many explanations, such as pressure oscillation theory, aerodynamic interference theory, air disturbance theory, turbulence disturbance theory, and sudden change of boundary conditions, which are briefly introduced as follows:
1. Pressure oscillation says
The pressure oscillation is said to observe that the pressure oscillation of the liquid supply system has a certain influence on the atomization process. Thus, pressure oscillations are prevalent in general injection systems and are therefore considered to play an important role in atomization.
2, aerodynamic interference
Castleman first proposed aerodynamic interference, he believes that due to the aerodynamic interference between the jet and the surrounding gas, the surface of the jet is unstable. As the speed increases, the surface length of the unstable wave is shorter and shorter, up to the order of micrometers, and the jet is dispersed into a mist.
3, the air disturbance said
The air disturbance said that it has the opposite attitude to the turbulence disturbance, and believes that the large amplitude pressure disturbance generated by the cavitation phenomenon in the fuel injection system is the cause of atomization.
4, the boundary conditions change
The boundary condition mutation says that the boundary condition (internal stress) of the liquid is abrupt at the nozzle exit; or the laminar jet protrudes and loses the wall constraint, causing the velocity distribution in the section to suddenly change and atomization. The five nozzle mechanism hypotheses listed above have deficiencies, and even contradict each other. Most scholars, such as BraccoFV, support the aerodynamic interference. This hypothesis has developed more fully, explaining the reason for the splitting and fragmentation of low-speed jets, and reasoning that high-speed jets can be used as the basic cause of atomization. At present, the research on the mechanism of fuel injection atomization is mainly carried out from two aspects: one is to use numerical calculation technology to establish a variety of hypothetical models for numerical modeling research; on the other hand, the advanced photoelectric testing technology is used to capture the details of the atomization process. To support some or a comprehensive hypothesis.