FM 1-506 Fundamentals of Aircraft Power Plants ... - Survival Books

WWW.SURVIVALEBOOKS.COMFM 1-506(Figure 4-7). Dual-entry fuel nozzles require a doublefuel namifold. Some dual fuel manifolds may not beapparent as such.Extreme care must be exercised when cleaning,repairing, or handling the nozzles. Even fingerprints onThe flow divider, whether self-contained in eachnozzle or installed in the manifold, is usually a springloadedvalve set to open at a specific fuel pressure. Whenthe pressure is below this value, the flow divider directsfuel to the primary manifold or nozzle orifice. Pressuresabove this value cause the valve to open, and fuel isallowed to flow in both manifolds or nozzle orifices.the metering parts may produce a fuel flow which is outof tolerance.Most modern nozzles have their passages drilled atan angle. The fuel is discharged with a swirling motion toprovide low axial air velocity and high flame speed. Inaddition, an air shroud surrounding the nozzle cools thenozzle tip. It also improves combustion by retarding theaccumulation of carbon deposits on the face. The shroudalso provides some air for combustion and helps tocontain the flame in the center of the liner (Figure 4-8).4-8