Although now only of historical value, the variable
port or Lubbock fuel spray nozzle (Figure 7e17) made use
of a spring-loaded piston to control the area of the inlet
ports to the swirl chamber. At low fuel flows, the ports
were partly uncovered by the movement of the piston; at
high flows, they were fully open. By this method, the
square law pressure relationship was mainly overcome
and good atomization was maintained over a wide range of
fuel flows.