Improvements relating to liquid or other fuel combustion apparatus

685,066. Burners. LUCAS, Ltd., J. Feb. 6, 1951 [Feb. 22, 1950], No. 4534/50. Class 75(i) [Also in Group XII] A liquid, gaseous or pulverized fuel burner apparatus comprises an air duct a, Fig. 2, containing a plurality of concentric annular louvres f, g, surrounding a fuel injection nozzle d and relatively movable axially to control the flow of air through the duct a by means of an axially movable member, e.g. a bush j, which actuates pivoted links h interconnecting the louvres. The upper half of Fig. 2 shows the louvres fully closed and the lower half shows them fully open. The bush j is in threaded engagement with and movably axially by a handwheel m, and the outer louvre f has a cylindrical extension controlling the admission to the burner through air-swirling passages p of secondary air from a chamber surrounding the primary air duct. In an alternative instruction the inner ends of the limbs are not movable axially, the adjustment being effected by axial movement of the outer louvre which has a rearward extension connected by radial arms to a slidable sleeve having a pin and helical groove connection with a bush rotatable by the handwheel. In this construction secondary air is supplied through a duct surrounding the outer louvre and its extension and is controlled by the movement of said louvre relatively to an annular shoulder in the duct.