The pressure jet
atomizer utilizes the supply pressure energy to atomize the fuel into a
spray of finely dispersed droplets. Provided adequate fuel pressure is used,
extremely good combustion results can be achieved.
The fuel oil is fed into the swirl chamber by means of the tangential ports in
the main atomizer body. An air core is set up due to the vortex formed in the
swirl chamber; this results in the fuel leaving the final orifice as a thin
annular film. This film of fuel has angular as well as axial velocity causing
the fuel to develop into a hollow con as it discharges from the orifice.
This type of fuel atomizer has a poor turn down ratio. A small drop in
fuel oil pressure will result in a dramatic reduction in combustion
performance. Two or three nozzles are sometimes fitted to achieve turn down,
one in use on low fire, two on medium fire and three for full rate firing. A
variation of the pressure jet atomizer is spill return or recirculating burner.
The problems with this type of burner are that the atomizer has an increasing
cone angle of the issuing spray as the burner is turned down with impingement
on the furnace walls being possible and the additional problem of how to
dispose of the returned hot oil if the burner has been running for prolonged
periods on low fire.
Danfoss fuel pressure jet atomizer