FUEL HEATING

96. The spill spray nozzle system, however, involves a somewhat modified type of fuel supply and control system from that used with the previous types. A means has to be provided for removing the

spill and also for controlling the amount of spill flow at various engine operating conditions. A

disadvatage of this system is that excess heat may be generated when a large volume of fuel is being recirculated to inlet. Such heat may eventually leadto a deterioration of the fuel.

97. The airspray nozzle (fig. 10-19), carries a proportion of the primary combustion air (Part 4) with the injected fuel. By aerating the spray, the local fuel- rich concentrations produced by other types of spray nozzle are avoided, thus giving a reduction in both carbon formation and exhaust smoke. An additional advantage of the airspray nozzle is that the low pressures required for atomization of the fuel permit sthe use of the comparatively lighter gear-type pump. 

98. A flow distributor (fig. 10-20) is often required to compensate for the gravity head across the manifold at low fuel pressures to ensure that all spray nozzles pass equal quantities of fuel.

99. Some combustion systems vaporize the fuel (Part 4) as it enters the combustion zone.