How does a vaporizing tube fuel nozzle on a gas turbine engine work?

Question

Also what does it look like and how do they perform in relation to simplex and duplex nozzles?

Answer 1

modern jet engine has single annular type combustion chamber now. here there are 30 holes for GE- CFC engine and 20 i think in the CFM engine. this holes are fitted with spray nozzles which has a primary and secondary flow. The primary flow are spraying a fine mist fuel which is use during starting and later on the secondary flow will be the one spraying the fuel.  a modern concept which has the burning staging valve will make sure that primary flow is introduced at cruise to economize fuel.Another new concept is called the Fuel Return valve which basically returns unburned fuel to tank via an oil fuel heat exchanger.

Answer 2

First of all, it's a vaporizer tube...period.  Nozzles are different; there is no nozzle on a vaporizer tube.

The vaporizer tube is a U shaped (or W shaped) tube in which the fuel first travels forward (relative to the gas flow) to be heated and vaporized by the combustion heat, and then rearward to add fuel to the fire.

Its main disadvantage is that it requires heat to work, so a separate starting fuel nozzle must be used.  The advantages are that only a couple of simple nozzles are required (they don't need different spray patterns or flows for full power since they are only used for starting) and since they have large orifices, they aren't as sensitive to clogging and don't require cleaning as frequently.

As nozzle technology has improved, the vaporizer tubes have gone the way of the dodo.  They are found mostly on older British engines.