Figure 2.4. Simplex Fuel Nozzle.

a. Simplex nozzle. Figure 2.4 illustrates a typical simplex

nozzle; as its name implies, it is simpler in design than the duplex

nozzle. Its big disadvantage lies in the fact that a single orifice

cannot provide a satisfactory spray pattern with the changes in fuel

pressure.

Figure 2.4. Simplex Fuel Nozzle.

b. Duplex nozzle. Because the fuelflow divider and the

duplex nozzle work hand in hand, the description of these units is

combined. The chief advantage of the duplex nozzle is its ability to

provide good fuel atomization and proper spray pattern at all fuel

pressures. For the duplex nozzle to work, there must be a fuelflow

divider to separate the fuel into low (primary) and high (secondary)

pressure supplies. Singleentry duplex nozzles have an internal flow

divider and require only a single fuel manifold, while, as shown in

figure 2.5, dualentry fuel nozzles require a double fuel manifold.

The flow divider, whether selfcontained in each nozzle, or installed

separately with the manifold, is usually a springloaded valve set to

open at a specific fuel pressure. When the pressure is below this

value, the flow divider directs fuel to the primary manifold.

Pressures above this value cause the valve to open and fuel is

allowed to flow in both manifolds. A fuel flow divider is shown in

figure 2.6.

In addition, an air shroud surrounding the nozzle, as

shown in figure 2.7, cools the nozzle tip and improves combustion by

retarding the accumulation of carbon deposits on the face. The

shroud also helps to contain the flame in the center of the liner.