Application of Laser Particle Size Analyzer in Nozzle Industry
First, the nozzle and its industry development
Nozzles, English NOZZLE , Chinese also known as nozzles, nozzles. The nozzle is a very important component in many types of equipment such as spraying, spraying , oil spraying, sandblasting , and spraying, and plays an important role. Nozzles are used in a wide range of applications in industries ranging from stainless steels, plastics to silicon carbide, PTFE, PP (engineering plastics), aluminum alloys, and tungsten steels. Applications are generally used in automobiles, electroplating, surface treatment, and high pressures. Cleaning, dust removal, cooling, desulfurization, humidification, mixing, gardening and other industries.
Since the nozzles are designed to operate in a variety of different spray conditions, the nozzles are selected to meet the best spray performance in use. The characteristics of the nozzle are mainly reflected in the spray type of the nozzle, that is, the shape formed when the liquid leaves the nozzle opening and its running performance. The nomenclature of the nozzle is divided into two types: a fan shape, a cone shape, a liquid column flow (ie jet), an air atomization, and a flat nozzle, wherein the tapered nozzle is divided into two major categories: a hollow cone and a solid cone; Factors such as flow, pressure, spray angle, coverage, impact, temperature, material, application, etc., and these factors are often interrelated, mutual constraints.
In recent years, the spray industry in China has grown steadily, and the status of the nozzle nozzle industry has become increasingly important. At present, the development of the nozzle industry has entered a stage of change, which is the period when China’s hardware products are replaced by new generations, from the low-end to high-end products. The market for spray parts is huge. Due to the increase in the level of Chinese hardware manufacturing and the expansion of production capacity , China's hardware products are expected to maintain a steady growth of more than 10% per year over the next five years .
Second, why the nozzle spray measurement
The atomization of liquids is a common requirement in many specialized fields. A variety of liquid atomizers are used in air-conditioning spray rooms, agricultural plant protection machinery, atomization and spray disinfection, spray irrigation and spray drying in agricultural buildings. An important indicator for assessing the performance of the nozzle is the droplet diameter and the droplet diameter distribution. However, the commonly used indexes such as the number of diameters, the volume, the arithmetic mean diameter or the average diameter of Salter can be different from each other. The side generally reflects the size of the droplet diameter, but it cannot fully reflect the overall droplet diameter distribution, that is, the range of the droplet diameter size and the droplets of different diameters do not occupy much. In order to conduct in-depth research on the spray head in order to correctly use and design the spray head and related devices that are matched with it, it is necessary to fully grasp the overall distribution of the droplet diameter spectrum.
Determination of the Nozzle Spray Particle Size Index The spray nozzle formed by the spray mist is composed of particles of different sizes of droplets. To describe and evaluate the atomization quality of fog droplets and to express their atomization characteristics, a droplet size distribution expression is required. To measure the size of particles or the number or quality of particles of different diameters. The indicator for evaluating the particle size of droplets can be expressed by a so-called “average diameterâ€, which envisages a uniform fog field with characteristics of a certain area that can replace the characteristics of the actual uneven fog field. The assumed droplet size of a uniform fog field is called the average particle diameter.
Third , spray particle size measurement method
Droplet size measurement method:
The accuracy of the droplet size test has a lot to do with the droplet sampling method and the accuracy of the measuring instrument. Ideally, the measurement of fog droplets should be performed in such a way that sampling and measurement are rapid; in the entire measured range, good droplet size resolution can be obtained; the change in the characteristics of the surrounding air in the liquid atomization zone can be well adapted; and it does not interfere with the measurement process. Atomization process or spray characteristics; easy to measure and economical. In addition, there are a large number of methods for measuring the size of droplets that have been developed. There is no one method that can satisfy all the above conditions. The key is to find a measurement method that meets the needs of a specific field.
The study of droplet size measurement experiments abroad started earlier. For example, in the early 40s of the last century , Meginer began to use the spot method to directly measure the size and distribution of droplets. Later Hoffman 's photographic method was an improved method of directly measuring the size and distribution of droplets. Due to the long experimental period and the need for professional participation, the amount of labor is very large, so few people use this method. Considering that the droplets are tiny and easily evaporate, Tate has proposed the use of immersion techniques to collect the droplets. Since the droplets are incompatible with the low-density fluids, the droplets will fall into the fluid and be surrounded by the fluid to avoid evaporation. Since the surface of the water droplet has tension, the size of the droplet can be measured using a microscope. At this stage, the size of the droplet is manually measured using a microscope, and the workload is large and the accuracy is poor.
When the droplet size is too small, the droplets are very volatile and have a lot of drift, which is difficult to measure accurately. Therefore, in order to measure the size and distribution of droplets more accurately, people have invented many optical-based measurement systems. Laser particle size analyzers are among them. When the particles dispersed in the liquid are irradiated with laser light, diffraction occurs. After passing through the Fourier lens, the diffracted light forms a “target-centered†diffraction ring on the focal plane. The radius of the diffraction ring is related to the size of the particles. The intensity of the diffractive ring is related to the size of the particles of the relevant size, and the diffraction signal or the light scattering signal of the particles of different particle sizes can be received by the ring-shaped photoreceptor array placed on the focal plane. This kind of instrument has extremely high measurement accuracy. Since non-contact measurement of the droplet is performed by using laser technology, the measurement error is reduced to very low. When the droplet diameter is 1 μm, the error is not more than 4% , and the measurement value needs no correction. The measurement process is extremely rapid and simple. The measurement of droplets in the air does not exceed a few seconds. The results of the measurement can be quickly processed after computer processing. The results of the measurement can be quickly printed out after calculation and processing; the measurement range can reach 0.5. Micron- 3500 microns. This range of manual measurement is unattainable. With the development of modern science and technology, laser particle size analyzers currently studied abroad can also measure the velocity of droplets.
Fourth, laser particle size analyzer in the nozzle industry
The laser particle size measuring instrument is a new type of particle size detection device that has emerged in recent years. It has real-time detection characteristics and it has a wide range of applications. With the development of the nozzle testing technology, the application of the laser particle size analyzer in the spray experiment has also been paid more and more attention. The State Key Laboratory of Coal Combustion, Wuhan University of Science and Technology, experimented with a winner318 laser particle sizer used in the nozzle experiment. The test results are as follows:
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