From Spray Nozzle
Flat spray nozzles are one of the most common nozzles in use today. Available in virtually any material and numerous spray angles, the pattern generated by this type of nozzle concentrates the fluid in a thin line. Not all flat sprays are created equal! Spray nozzle design and precision machining have a significant effect on the stability of the spray pattern and impact achieved. The impact received is directly related to the density of the spray pattern, so the tighter you maintain the spray pattern, the more impact per in2 will be received. Reducing the spray height to the minimum amount possible and using more nozzles also significantly increases the impact received.
There are several different types of flat spray nozzles including axial and deflector configurations. The narrower the spray angle, the greater the impact you'll receive at a given distance. Therefore narrower angle nozzles are used for difficult cleaning applications and wider angle nozzles are used for less intensive washing, foam control, dust suppression, coating and similar applications.
There are two types of flat spray patterns, some have tapered patterns and others provide an even distribution. The most common type has a tapered spray distribution and the diagram above shows overlapping the nozzles by about 30%. Since the edges of the spray flow less than the center portion, the overlapping of the spray patterns help equalize the flow distribution across the target. In some applications 100% or more overlap is required if there is a potential for nozzle pluggage problems. You must also remember to offset your spray nozzles so that their patterns do not intersect prior to impacting the target.
The latest Spray Nozzle Engineering Manual has several pages dedicated to flat spray nozzles as well as an introductory page on flat spray nozzles in general.