/kloc-in the 8th century, physicist Coulomb discovered through experiments that the charges carried by insulated metal conductors would disappear in the atmosphere. In addition, physicists Roentgen and becquerel found that the gas in electrolyte solution has a positive or negative charge, which makes the gas conductive. Physicists estelle, Gatler and Wilson also explained Coulomb's experimental results with the theory of atmospheric conductivity. This conductive particle in the air is called "ion" by physicist Faraday, hence the name "air ion".
100 years later, J .Thomson was the first to express the characteristics of ions with formulas, and at the same time established the models of positive and negative ions. Eiseer and Geieel later proved the existence of ions, that is, particles with positive and negative charges, whose particle size is slightly larger than that of molecules. 1905, Langlin discovered the second ion in the atmosphere, called Langlin ion or large diameter charged particles, also known as heavy ions. By 1909 A.Pouer, the third ion, that is, the ion with medium diameter, was found, which was called the middle ion. By 1930s, Deschauer had begun to study the positive and negative ions in the atmosphere. He first used the corona ion generator, which formed the first research climax of negative ion biological effect. Hundreds of papers, research and experimental reports have proved that negative ions have obvious beneficial effects on human body, while positive ions have obvious destructive effects on human blood pressure and metabolism. These studies were terminated by World War II. Professor ALbeterPani Kragan of the University of California and his research team initiated the microscopic research and experiment of ion biological effects, which pushed the research of air negative ions to the climax of the second development and utilization. Professor Kragen has done a lot of experiments on animals, plants and humans, and demonstrated how negative ions affect humans, animals and plants and how they produce various biological effects from the aspects of human endocrine, internal circulation and the reaction of various enzymes. Many researchers around the world have carried out the above experiments on the basis of their own research, and think that negative oxygen ions have obvious biological effects. Many new negative ion generators have been developed abroad, which are used in experimental research, air conditioning rooms and medical and health fields.
From 1889, German scientists elster and Gaertel discovered the existence of negative air ions, and German physicist Dr. filippo Nair was the first to prove the efficacy of negative air ions on human body academically. By 1902, Assamas and others affirmed the biological significance of the existence of air ions. 1903, Russian scholars published a paper on the treatment of diseases with negative air ions. American RCA company Hamsen invented the world's first medical air negative ion generator in 1932. In the past half century, the research on air negative ions in Europe, America and Japan has gone through a long period of development and application.
AS series negative oxygen ions won the gold medal in 1976 Geneva international exhibition of new inventions and technologies.
The device uses corona discharge to generate negative ions. The structure of negative oxygen ion generator is shown in Figure 2- 1.
In Figure 2- 1, if a DC high voltage of 3~4 kV is applied between a row of needle-shaped negative electrodes and a ring-shaped positive electrode, a corona discharge will be generated at a row of needle-shaped negative electrodes, which will ionize the air. Because the electron affinity of oxygen is much greater than that of nitrogen and other gases, most of the free electrons ionized by air are captured by oxygen molecules, forming negative oxygen ions. These negative oxygen ions are repelled by negative high voltage, and some of them are equipped with a small axial fan behind the negative electrode. Under the action of electric field and fan wind, negative oxygen ions are constantly discharged in the gap of the annular positive electrode, forming fresh air containing a large number of negative oxygen ions.
Air is mainly composed of nitrogen (78.09% of air) and oxygen (20.95% of air). Normally it is neutral, but due to cosmic rays, ultraviolet rays, radiation of trace radioactive substances and some physical and chemical reactions, a few neutral molecules (or atoms) in the air will be ionized into free electrons and positive ions, and free electrons often combine with neutral molecules to form negative ions. Because the electron affinities of various gas atoms (or molecules) are different, those with high affinities are easy to absorb electrons and generate negative ions. The electron affinity energy of nitrogen is 0~0.05 eV, and that of oxygen is1.13 ~1.47 ev, which is in the lower layer.
The atmosphere is the most abundant, so most of the free electrons ionized in the air are captured by oxygen molecules and become negative oxygen ions. The process is as follows: [2]
However, some oxygen molecules are reduced to oxygen atoms during ionization.
If oxygen atoms recombine with oxygen molecules, ozone will be produced.
What is mentioned above is the situation near the electrode of the ionized negative oxygen ion generator.
[3]
The working principle of negative ion generator comes from corona discharge. Corona discharge is a form of gas self-sustaining discharge, which does not need external ionization source to start and maintain the discharge. In order to maintain a stable corona discharge, an uneven electric field must be formed. With the increase of applied voltage between electrodes, the intensity of space electric field near the conductor will also increase. Usually in free space, there are about 1000 free electrons per cubic centimeter of air due to cosmic radiation. Under the action of electric field, these free electrons will accelerate the impact on gas atoms or molecules. The acceleration of free electrons will increase with the increase of electric field intensity, and the energy accumulated by free electrons before hitting gas atoms or molecules will also increase. When the electric field intensity reaches the critical value of gas discharge, the energy accumulated by free electrons before impact will be enough to impact an electron from a gas atom or molecule. At this time, the air in a small area near the conductor began to ionize, and there was an unconscious discharge of gas. If the voltage continues to rise, the gas ionization intensifies, forming a large number of electrons to collapse, producing a large number of electrons and positive and negative ions, accompanied by light blue glow and hiss, and the discharge changes from non-self-sustaining discharge to self-sustaining discharge. This special form of gas discharge is called corona discharge.
The inhomogeneity of the electric field limits the main ionization process to the vicinity of the electrode with high local electric field intensity, especially in the large or small thin layer near the electrode with small curvature radius, and the gas luminescence only occurs in this area, which is called ionization region, or corona layer or corona layer. Outside the region, because the electric field is weak, ionization does not occur or rarely occurs, and the conduction of current depends on the migration movement of positive ions, negative ions or electrons, so the region outside the ionization region is called migration region or peripheral region. If the two electrodes have only one halo, the migration region of the discharge basically has only one charged particle. In this case, the current is unipolar. In this experiment, the two electrodes of negative ion generator that form uneven electric field are corona wire electrode and negative high-voltage grounding electrode, which generate negative corona discharge and form negative corona current.
After corona discharge, if the voltage between the two electrodes is further increased, the corona area will gradually expand, and the brightness and hiss will become louder and louder. When the voltage rises to a certain value, brush-like fine sparks can appear at some discharge points, which are much larger than the normal corona area, accompanied by hissing and cracking. This form of discharge is called brush discharge. With the continuous increase of voltage, the brush spark becomes longer and longer, and finally a channel will be formed between the positive and negative electrodes, which will lead to gas breakdown and the voltage between the two electrodes will drop sharply. According to the size of power supply capacity, the form of breakdown can be arc discharge or spark discharge.
When the power supply capacity is large enough, the gas will flow through a large discharge current after breakdown, forming an arc between the electrodes, which is called arc discharge; If the power supply capacity is small, the discharge current will be limited after gas breakdown, so that it is not enough to form an arc, and then the discharge will stay in the spark discharge stage. Spark discharge is a bright, tortuous and often bifurcated filament, which quickly passes through the discharge gap, then goes out quickly and reappears immediately after being extinguished. The current of spark discharge is much smaller than that of arc discharge.
In order to make the generator work normally, a certain voltage must be applied between the electrodes to form a corona discharge. The lowest voltage that forms corona discharge is called corona starting voltage. At this time, due to the ionization of air, a large number of ions will flow through a certain corona current under the action of voltage, and the corona current will increase with the increase of voltage. Of course, due to the existence of free electrons in the air, even if the applied voltage is much smaller than the corona voltage, a current will be formed between the electrodes due to the flow of free electrons, but the number of these free electrons is very small, and the formed current can be ignored compared with the corona current. [4]
An important technical index of negative oxygen ion generator is negative oxygen ion concentration. Generally in the generator manual
The concentration value marked in indicates the negative oxygen ionization in the air 20 cm in front of the negative oxygen ion generator.
The partial concentration, the concentration greater than or less than 20 cm is different, so the concentration of negative oxygen ions must be input.
Theoretical calculation and test of lines. The negative oxygen ion stream discharged from the negative oxygen ion generator contains conduction current.
And current-carrying current, i.e.
(2) Bring in (1)
Using gauss theorem
Now we will discuss the one-dimensional steady-state system of oxygen ions moving at a uniform speed, because
(4) Become
(5) There is an exponential decay solution.
because
Therefore, the negative oxygen ion concentration is
The results show that the negative oxygen ion concentration n of the steady-state system starts from the needle cathode and decreases exponentially with the distance.
As shown in Figure 2-2, the experimental observation value is consistent with the theoretical calculation value.
By simulating the temperature and humidity under natural conditions, the negative ion concentration in the air was measured for several months, and the influence of temperature and humidity changes on the negative ion concentration was discussed in detail. The radiation intensity from the same place remains basically unchanged, that is, only the temperature and humidity change in the experimental environment.
The negative ion generator generally consists of a body, a corona wire emitting end, a grounding end and a power supply input end.
As shown in figure 1, the alternating voltage is converted into direct current through step-down, rectification and filtering, and then passes through an oscillator, an amplifier circuit and a switch tube, and is controlled by a high-voltage magnetic bag to generate negative ions. The high-voltage magnetic bag is a high-frequency transformer, and there is a high-voltage silicon pile in the high-voltage magnetic bag to rectify its inverter voltage, so its output is rectified DC. All inverter currents belong to alternating current, and the current directions of transformer energy storage and energy release are opposite. A current with a fixed current direction is called direct current. There are several kinds of inverters, single-ended and bridge, single-ended forward, single-ended flyback, half bridge, full bridge and so on.
Body: It is a high-voltage insulator with plastic shell and flame-retardant epoxy resin. The fuselage shell is usually made of PBT (polybutylene terephthalate) or PEI (polyether) by injection molding, and the material must be resistant to high temperature above 200℃, flame retardant and insulating.
Corona wire emitting end: metal needle or carbon fiber is usually used.
Grounding terminal: copper sheet is used for grounding.
Power input: power cord.
The above picture shows an efficient open negative ion generator, which uses SCR inverter high-voltage floating discharge needle, with simple structure, good effect, safety and reliability. The mains voltage can work normally from 160 V to 250 V, and the power consumption is extremely low, only about 1W, so it can work continuously for a long time.
220V commercial power supply is rectified and current-limited by VD 1, VD2, R 1, R2. One-way pulsating current controls the on-off of VS to generate oscillation. After being boosted by transformer T, it is rectified by VD3 to obtain a negative high voltage of about 10000 volts. After discharge, it discharges into the air, producing ionization and negative ions.
Because of the high voltage and high temperature, the high-voltage magnetic bag is easy to generate sparks and puncture the surrounding electronic components, so Tenon (polytetrafluoroethylene) is used to package the high-voltage magnetic bag here. Epoxy resin containing flame-retardant and heat-resistant resin or plastic powder containing melamine resin is poured outside the high-voltage magnetic bag. The welding surface of PCB is covered with plastic powder, which can also fill the insulation gap; The gap is filled with flame retardant epoxy resin, which avoids the mutual interference between circuit elements and can improve the service life of circuit elements.
China has its own patented high-end negative ion technology: negative ion converter technology and nano-fullerene releaser technology, which makes negative oxygen ions become an auxiliary medical means in medical treatment.
The negative ion converter is a special component used in negative ion generating equipment, which can make the equipment generate small particles of air negative ions, that is, light ions. Small particles of negative ions have the characteristics of high kinetic energy and high activity, and the migration distance and speed are large. Negative oxygen ions can cover 4-5 meters without fan blowing.
Fullerene is an electrocatalyst material made of nanotechnology, which is close to superconductivity, that is, the resistance is almost equal to zero. When ions pass through this material, it will produce strong vibration benefits, so it makes full use of the free precipitation of ions, so it does not need strong current like traditional ion release materials (ordinary carbon fiber metal, etc.). ). Only a relatively weak current is needed to release large dose, high purity, high activity and small particle size negative ions.
Take a brand negative oxygen ion generator in Taobao as an example.
It can be seen that it has an output voltage of -40kv.