spray burst is a precision device that facilitates the spreading of liquid into the spray. Nozzles are used for three purposes: to distribute liquids to an area, to increase the surface area of ​​the liquid, and to create impact force on a solid surface. A wide variety of spray nozzle applications use a number of spray characteristics to describe sprays.
The spray nozzle can be categorized based on the energy input used to cause atomization, breaking the liquid into droplets. The spray nozzle can have one or more outlets; Double outlet nozzles are known as compound nozzles. Spray nozzles range from heavy industry duty use to light spray cans or spray bottles.
Video Spray nozzle
Single-fluid nozzle
Single-fluid or hydraulic spray nozzles utilize the kinetic energy of the liquid to break it down into droplets. This type of the most widely used spray nozzle is more energy efficient in generating surface area than most other types. As the fluid pressure increases, the flow through the nozzle increases, and the drop size decreases. Many configurations of the single liquid nozzle used depend on the desired spray characteristics.
Flat hole nozzle
The simplest single-fluid nozzle is the usual orifice nozzle as shown in the diagram. This nozzle often produces little if any atomization, but directs the flow of fluid. If high pressure drops, at least 25 bar (2,500 kPa), these materials are often atomized subtly, as in diesel injectors. At lower pressures, this type of nozzle is often used for tank cleaning, either as a fixed position compound spray nozzle or as a rotary nozzle.
Shaped-orifice nozzle
The hole is shaped using a half-spherical inlet and a dotted outlet V causes the flow to spread on the V notch axis. A flat fan spray result is useful for many spray applications, such as spray painting.
Nozzle surface-nozzle nozzle
A nozzle of surface throttling causes the flow of liquid to pierce on the surface resulting in a sheet of liquid breaking into droplets. This flat fan spray nozzle is used in many applications ranging from applying agricultural herbicides to rowing plants to painting.
The crusher surface may be formed in a spiral to produce a spiral sheet that approximates a full conical spray pattern or a hollow cone spray pattern.
The spiral design generally results in a smaller decrease size than the nozzle type pressure vortex design, for a certain pressure and flow rate. This design holds the tray because of the large free parts.
Common applications include gas scrubbing applications (eg, flue-gas desulfurization where smaller droplets often offer superior performance) and fire suppression (where droplet density blends allow spray penetration through strong thermal currents).
Pressure-swirl pressure-swirl nozzle spray
A spin-pressure spray nozzle is a high-performance (small drop size) device with one shown configuration. The stationary core induces the movement of the spinning fluid that causes swirling fluid in the vortex space. The film is removed from the perimeter of the outlet hole that produces a typical perforated cone spray pattern. Air or other surrounding gases are drawn in the vortex to form the air core in the spinning fluid. Many liquid input configurations are used to produce this hollow cone pattern depending on the nozzle capacity and construction materials. The use of this nozzle includes evaporative cooling and spray drying.
Solid cone liquid nozzle
One of the configurations of the solid cone spray nozzle is shown in the schematic diagram. A circular liquid motion is induced with a propeller structure, however; the flow of discharge fills the entire outlet hole. For the same capacity and drop in pressure, the full cone nozzle will result in a larger drop size than the hollow cone nozzle. Coverage is a desirable feature for such nozzles, which are often used for applications to distribute liquids to an area.
Nozzle compound
The compound nozzle is a type of nozzle in which some single nozzle or two nozzles are inserted into a single nozzle body, as shown below. This allows control of the design of the drop size and the angle of spray coverage.
Maps Spray nozzle
Two-fluid nozzle
The two-fluid nozzle sprayed by causing high-speed gas interactions and fluids. Compressed air is most often used as an atomizing gas, but sometimes vapors or other gases are used. Many diverse designs of two-liquid nozzles can be grouped into internal or external mixtures depending on the point of mixing the flow of gas and liquid relative to the nozzle face.
Two-way mixed internal mixer
Internal fluid-filled contact nozzle in the nozzle; one configuration shown in the picture above. Sliding between high-speed gas and low-velocity fluids destroys liquid streams into droplets, producing high-speed sprays. This type of nozzle tends to use less gas atomization than an external mixer sprayer and is better suited for higher viscosity flows. Many commercially mixed mixed nozzles are commercially used; for example, to atomize the fuel oil.
External-mix two-liquid nozzles
The external mixed nozzle contacts the outer fluid nozzle as shown in the schematic diagram. This type of spray nozzle may require more atomization air and a higher drop of atomization air pressure due to the mixing and atomizing of liquids going beyond the nozzle. The decrease in liquid pressure is lower for this type of nozzle, sometimes drawing fluid into the nozzle due to suction caused by the air atomization nozzles (siphon nozzles). If the liquid to be atomized contains solids, the mixed external mixer may be preferred. This spray can be formed to produce different spray patterns. Flat patterns are formed with additional air ports to flatten or reshape a circular spray cross section.
Two-fluid nozzle control
Many applications use two-fluid nozzles to achieve controlled small droplet size over the operating range. Each nozzle has a performance curve, and the flow rate of liquid and gas determines the size of the drop. Excessive fall sizes may result in catastrophic equipment failure or may have adverse effects on processes or products. For example, the gas conditioning towers at the cement plant often use evaporative cooling caused by water atomized by a two-fluid nozzle into a dusty gas. If the droplets do not fully evaporate and crash into dust the vessel wall will accumulate, resulting in potential flow limitations in the outlet channel, disrupting the installation operation.
Rotary atomizers
Rotary atomizers use high-speed rotating disks, cups or wheels to discharge high-speed fluid to the perimeter, forming hollow cones. Rotation speed controls the size of the drop. Spray drying and spray painting are the most important and common uses of this technology.
Ultrasonic Atomizers
This type of spray nozzle uses high-frequency vibration (20-180 kHz) to produce narrow strip size distributions and low-speed sprays from liquids. Piezoelectric crystal vibrations cause capillary waves in the nozzle surface liquid film. An ultrasonic nozzle can be the key to high transfer efficiency and process stability as it is very difficult to clog up. They are very useful in coating medical devices for their reliability.
Electrostatic
Electrostatic spray filling is very useful for high transfer efficiency. Examples are spraying the paint industry and the application of lubricating oil. Charging at high voltage (20-40 kV) but low current.
Nozzle performance factor
Liquid properties
Almost all drop size data provided by nozzle manufacturers is based on water spraying under laboratory conditions, 70 ° F (21 ° C). The effects of liquid properties should be understood and taken into account when choosing a nozzle for process-sensitive drop size.
Temperature
Changes in liquid temperature do not directly affect the performance of the nozzle, but may affect the viscosity, surface tension, and specific gravity, which may subsequently affect the performance of the nozzle spray.
Specific gravity
Specific gravity is the ratio of the volume of fluid volume to the same mass of water volume. In spraying, the main effect of the specific gravity of Sg of a liquid other than water is at the capacity of the nozzle spray. All performance data provided by the vendor for the nozzle is based on water spraying. To determine the volumetric flow rate of Q, a liquid other than water, the following equation should be used.
Viscosity
Dynamic viscosity is defined as the fluid properties that resist form changes or the arrangement of its elements during flow. The viscosity of the fluid mainly affects the spray pattern formation and the size of the drop. High viscosity liquids require a higher minimum pressure to initiate spray formation and produce narrower spray angles compared to water.
Surface tension
Liquid surface tension tends to assume the smallest possible size, acting as a membrane under pressure. Each part of the liquid surface provides a tension to the adjacent part or to other objects in contact. This force is in the plane of the surface, and the sum per unit length is the surface tension. The value for water is about 0.073 N/m at 21 ° C. The main effects of surface tension are minimum operating pressure, spray angle, and drop size. Surface tension is more noticeable at lower operating pressures. Higher surface tension reduces the spray angle, especially in hollow cone nozzles. Low surface tension may allow the nozzle to be operated at a lower pressure.
Use of nozzle
Wear nozzle is indicated by the increase in the nozzle capacity and by changes in the spray pattern, where the distribution (spray pattern uniformity) worsens and increases the size of the drop. The choice of wear-resistant construction materials improves the life of the nozzle. Since many single fluid nozzles are used to measure flow, the used nozzles result in excessive use of fluid.
Construction materials
Construction materials are selected based on the liquid nature of the liquid to be sprayed and the surrounding environment of the nozzle. Spray nozzles are most commonly made of metals, such as brass, stainless steel, and nickel alloys, but plastics such as PTFE and PVC and ceramics (alumina and silicon carbide) are also used. Several factors should be considered, including erosion wear, chemical attack, and high temperature effects.
Apps
See also
- Nozzle
- Nebulizer
- Pesticide application
- Ilass Institute for Liquid Atomization and Spray System
- Bottle spray
References
Source of the article : Wikipedia
0 Comments