Pressure-atomizing nozzle

Figure 4 shows a three-dimensional distribution of the Sauter mean diameter, measured 38.1-mm downstream from the nozzle using a Delavan 1 GPH-80°A pressure atomizer. The operating pressure was 690 kPa (100 psi). TypicaUy, the mean diameters graduaUy increase with an increase in radial... 

Liquid fuel is injected through a pressure-atomizing or an air-blast nozzle. This spray is sheared by air streams into laminae and droplets that vaporize and bum. Because the atomization process is so important for subsequent mixing and burning, fuel-injector design is as critical as fuel properties. Figure 5 is a schematic of the processes occurring in a typical combustor. 

Spray characteristics of pressure nozzles depend on the pressure and nozzle-orifice size. Pressure affects not only the spray characteristics but also the capacity. If it is desired to reduce the amount of liquid sprayed by lowering the pressure, then the spray may become coarser. To correct this, a smaller orifice would be inserted, which might then require a higher pressure to produce the desired capacity, and a spray that would be finer than desired might result. Multiple nozzles tend to overcome this inflexible charac teristic of pressure atomization, although several nozzles on a diyer complicate the chamber design and air-flow pattern and risk collision of particles, resulting in nonuniformity of spray and particle size. 

The second, additive term carrying the viscosity impact in Eq. (14-199) is small at viscosities around 1 centipoise but can become controlling as viscosity increases. For example, for air at atmospheric pressure atomizing water, with nozzle conditions. 

Pressurizing the oil and forcing it through a nozzle (mechanical atomizing burner)... 

The decrease in the mean droplet size with increasing liquid injection pressure may be attributed to two effects. First, the high pressure-drop across the exit orifice makes the process more like a pressure atomization at high pressure. Second, the liquid is squeezed into fine ligaments as it flows through the injector orifice, and the ligaments are shattered into small droplets by the explosion downstream of the nozzle exit. 

Both air and fuel are injected through the same atomizing nozzle in this burner. Fuel is injected at a low pressure while air is injected at a high velocity resulting in a finer spray than is provided by the high pressure atomizing gun. A secondary, external air supply is also provided. This type of atomizer is less susceptible to nozzle plugging. 

Rotating Nozzle (rotary atomizer) fluid is fed at low pressure to the center of a rapidly rotating disk and centrifugal force breaks up the fluid. These types of nozzles are used mainly in a spray drying application. 

Fig. 4. Tail-form chamber employing nozzle atomization. System is particularly suited for dense particles requiring high-pressure atomization. (Stork-Bowen)...

For Nozzle (3), a pressure atomization nozzle, also called the centrifugal pressure nozzle, can be employed. It is desirable to use the eddy pressure nozzle (Chinese patent, ZL00230305.1). The latter has a higher flow-rotating efficiency, and thus requires less energy to atomize the liquid or solid-in-liquid suspension. 

Figure 11, Combustion efficiency and smoke emissions—pressure-atomizing nozzle, FT12/FT4 combustor, T ir = 530 K Redwood 650 oil P = iO atm Tf i = 50 K,...

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