Atomizing process of atomizing nozzle
Industrial nozzle in the field of atomization of atomization spray nozzle, spray nozzle atomization technology is also divided into many kinds, atomization nozzle working principle of these technologies almost cover all industrial fields. In industrial application, we can understand how important the use of atomizing nozzle is, because atomizing nozzle can effectively remove dust and purify the environment, add moisture and cooling but industrial procedures, etc. With the multi-purpose application of atomizing nozzle. Atomizing nozzle family has gradually grown up, this article introduces the differences and characteristics of the four categories of atomizing nozzles often used in high pressure. Different characteristics of atomizing nozzles lead to different atomizing effects.
First, the atomization process of industrial atomization nozzle
Atomizing nozzle, as the name implies, is the liquid through the pressure to realize the liquid through the nozzle to form a fog structure. When the liquid is pressurized, the nozzle shoots into the static or low-speed airflow at a high speed. Due to the different structure of the nozzle, the atomization process is also different. It is usually atomized by the following process.
1, direct spray nozzle atomization process
When the liquid pressure increases, the injection velocity increases. Under the interaction of liquid surface tension, sticky parts and air resistance, the liquid transitions from dripping, smooth flow and wavy flow to spray flow. When the injection velocity (i.e., flow rate) increases, the length of liquid column changes in the above liquid flow state. The Reynolds number RE=1800 ~ 2400 for the transition from migratory flow to wavy flow to turning point is consistent with the turning point of laminar flow and turbulent flow (turbulence). When the turning point of viscous liquid RE≥3000, spray flow is formed.
2, centrifugal nozzle liquid film jet atomization process
Atomization process of swirling pressure atomizer (or centrifugal nozzle) under different oil pressure. At low oil pressure, the injection speed is small, and the surface tension and inertial force play a major role. Although the surface tension overcomes the inertial force and causes the liquid film to contract into vacuoles, it breaks into large droplets under aerodynamic force. With the increase of pressure, the injection velocity increases, and the liquid film becomes unstable under the action of inertia force. Broken into silk or ribbon, and the relative movement of the air is intense, the surface tension and viscous force are weakened, the length of the liquid film is shortened. And twisted, under the action of aerodynamic forces broken into small droplets. At higher pressure (3.0mpa), the liquid jet velocity is higher, and the liquid film is atomized when it leaves the nozzle.
In general, when the pressure of the centrifugal nozzle is 0.3-0.5mpa, a part of the liquid film at the outlet of the nozzle can also be put into the combustion process. In the study of the above atomization process, it is found that the smaller the surface tension of the liquid, the thinner the liquid film can be broken, forming fine filaments and bands, and condensing into fine droplets. The stickiness has the effect of preventing crushing. The greater the viscosity, the more difficult it is to atomize into drops, which can only form filaments, even pieces or chunks. In addition, it is found that the viscosity of the liquid influences the KCS of the liquid on the KCS. When the viscosity is low, the tangential and radial velocities increase and the atomization quality becomes better. In the middle phase of atomization, surface tension plays a major role, that is, affecting the liquid film. In the later phase of atomization, viscous force, surface tension, oil droplet inertia force and air resistance interact to make the droplet further.
3, the atomization process of rotary atomizing nozzle
The liquid is supplied to the center of the high-speed rotating part, and the liquid is thrown out to the periphery or hole of the rotating part. It is a rotating atomization of liquid atomized by centrifugal force and gas power. When the liquid flow rate is very small, when the centrifugal force is greater than the liquid surface tension, a small number of large droplets thrown from the edge of the turntable, at this time directly * into droplets. When the flow rate and rotational speed increase, the liquid is pulled into a large number of filamentous jets, and the liquid flow is extremely unstable, and it will separate into small droplets at a certain distance from the disk edge. This is filamentous splitting into droplets. When the speed and flow increase again. The liquid wire is connected into a thin film, with the liquid film outward expansion into thinner liquid film, and at a high speed, and the surrounding air friction and separation atomization. Formed by a thin film into droplets. It can be seen from the above process that rotating atomization includes the interaction between centrifugal atomization and velocity atomization. The above two methods of atomizing liquid with the help of external power (oil pump pressurization and motor growth) are collectively known as mechanical atomization. And centrifugal pressure atomization and rotary atomization, with the help of centrifugal force. However, the droplet can be further atomized by using a small amount of atomizing air on the rotating nebulizer of the rotary cup type.
4, medium atomization nozzle atomization process
By means of a high-speed coaxial or vertical jet of a fluid such as air or steam, the liquid column or liquid film of the working medium can be atomized. Collectively known as dual fluid atomization nozzle, also known as hook pneumatic nozzle, air atomization nozzle. Their atomization essence is similar to the pressure atomization process mentioned above, only strengthening the role of the surrounding air flow. It is the use of high speed, generally with tens of meters per second, even supersonic air or steam and low-speed liquid column or liquid film mutual impact, friction, broken into small droplets, that is, external force (impact force, friction force) is greater than the internal force of oil (surface tension and viscous force) and broken flow stock or liquid film.
Two, the working principle of industrial atomizing nozzle
The working principle of industrial atomizing nozzle is through the internal pressure, the internal liquid extrusion into the nozzle, the atomizing nozzle is placed inside a blade, the principle of high pressure or low pressure atomizing nozzle is through the high-speed motion of liquid through the swirl cavity of the blade to form a spray, the thickness of the nozzle blade. The spray hole aperture of the atomizing nozzle makes the liquid split into atomizing particles with a diameter of 15-60 microns after impact and rebound, and then spray out through the outlet of the atomizing nozzle to form a small atomizing spray.
Three, the use of industrial atomizing nozzle
1. Use method of fan nozzle
The fan-shaped liquid is sprayed in a fan shape, and the impact force is greater than that of the hollow cone and the solid cone. In order to obtain a more equal flow distribution when installing several fan-shaped nozzles, the distribution is generally designed as a mountain-shaped distribution. The flow distribution, spray height, spacing between installation positions, spray pressure and liquid properties are different. If the performance of multiple nozzles is upstream wrong, the design value will not be consistent with the actual value. Therefore, the company has nozzles with sufficient accuracy to ensure a balanced flow distribution.
2, the use of hollow cone nozzle
The nozzle pressure, spraying flow, spray Angle, under the condition of same hollow cone nozzle's average particle is the smallest, under the condition of minimum average particle diameter, make processing workpiece surface area increases, and handle more exquisite, larger influence on the movement of the material, hollow cone nozzle in air cooling, air humidification, Metal treatment, dust control, gas cleaning and chemical reactions can produce good results. In the hollow conical nozzle, because the liquid is squirted out through a single hole and several centrifuges, it has the largest smooth diameter, it is an ideal choice for the liquid that is easy to produce precipitation, it can minimize the generation of blocking phenomenon.