Smoke generation principle of anti-theft smoke smog

Smoke is an artificial aerosol formed by a fuming agent. As an artificial aerosol, smoke has no fundamental difference in its basic principles from general aerosols. It is usually formed by the mechanical dispersion of physical processes and the agglomeration of physical and chemical processes. The difference between the two forms of formation is that the dispersion increases the specific surface area of ​​the original system, while the agglutination reverses, reducing the specific surface area.

There are three methods for forming smoke, namely, dispersion method, agglutination method, and synthesis method. The comprehensive method is still a combination of both physical and physical chemical processes in principle.

(1) Dispersion method: It is a mechanical force that pulverizes solid or liquid smoke into fine particles dispersed in the air.

Mechanical pulverization of solid smoke is slowly applied to the solid by means of grinding, milling or extrusion; it can also be rapidly applied to the solid in the form of high pressure gas and jet or high energy impactor collision. The disadvantage is that the dispersion is not high and it is difficult to form a stable aerosol. For example, the color smoke produced by young people's favorite color running is mainly made of corn starch. The way to form smoke is a typical dispersion method.

Color smoke in the "Color Run" campaign

(2) Coacervation method: The formation of the dispersed phase of this method is divided into two stages: first, a supersaturated vapor is formed, and then the supersaturated vapor is recondensed into the smoke.

There are two ways to obtain supersaturated vapor, that is, to cool the hot vapor and to form a vaporous substance by chemical reaction to supersaturate the space vapor.

The cooling hot steam method is based on the decrease in temperature, the saturated vapor pressure and the vapor concentration in the space are also reduced, and further cooling produces supersaturated vapor, during which excess vapor is condensed into a large amount of suspended particles in the atmosphere to form a smoke. The thick white smoke from the old steam engine train is a typical condensation method.

Rolling white smoke from a steam engine train

The process of chemically reacting to form a vaporous substance to supersaturate the vapor is essentially a process of combustion into a smoke. The gaseous substance produced by the combustion chemical reaction forms a supersaturated vapor after cooling in a gaseous medium, and then condenses into a smoke by supersaturated vapor. The essence of the Funi mist is to use a chemical reaction coacervation method.

Funey smoke sprayed by smoke

(3) Comprehensive method: It uses both the dispersion method and the agglutination method to produce smoke.

A part of the soot is formed by a dispersion method, and the other part is formed by a coagulation method. The formation of soot is a combination of the two processes of dispersion and agglutination.

Explosion into smoke is an example of a comprehensive law. During the explosion, the solid or liquid is dispersed by the high pressure gas to be dispersed into the spherical space centered on the explosion point to form the aerosol particles. At the same time, due to the high temperature during the explosion, the vapor is mixed with the air and cooled to cool it. The space is supersaturated and then condensed into smoke.

Smoke from the zha bomb